MULTI-STAGE HEAT EXCHANGE SYSTEM

专利摘要:
ocean thermal energy conversion power plant. The present invention relates to a power generating structure comprising a portion having a first deck portion comprising an integral multistage evaporator system, a second deck portion comprising an integral multistage condensing system , a third deck portion that houses power generation equipment, a cold water pipe, and a cold water pipe connection. the evaporator and condenser systems include a multi-stage cascade heat exchange system. hot water conduits on the first deck portion and cold water conduits on the second deck portion are integral with the structure of the deck portion.
公开号:BR112014003524B1
申请号:R112014003524-5
申请日:2012-08-15
公开日:2021-08-10
发明作者:Laurence Jay Shapiro；Jonathan M. Ross；Barry R. Cole；Bruce Robert Marson
申请人:The Abell Foundation, Inc.；
IPC主号:

专利说明:

FIELD OF TECHNIQUE
[001] This invention relates to ocean thermal energy conversion power plants and more specifically to low oscillation floating platform ocean thermal energy conversion power plants, multistage thermal engine. BACKGROUND
[002] Energy consumption and demand across the world has grown at an exponential rate. This demand is expected to continue to increase, specifically in developing countries in Asia and Latin America. At the same time, traditional energy sources, namely fossil fuels, are being depleted at an accelerating rate and the cost of exploiting fossil fuels continues to rise. Environmental and regulatory concerns are exacerbating this problem.
[003] Solar relative renewable energy is an alternative energy source that can provide a portion of the solution to the growing demand for energy. Solar relative renewable energy is attractive because, unlike fossil fuels, uranium, or even "green" thermal energy, there are few or no climate risks associated with its use. Furthermore, relative solar energy is free and widely abundant.
[004] Ocean Thermal Energy Conversion ("OTEC") is a way of producing renewable energy using solar energy stored as heat in tropical regions of the ocean. Tropical oceans and seas around the world offer a unique renewable energy resource. In many tropical areas (between approximately 20° north and 20° south latitude), surface seawater temperature remains nearly constant. At depths of approximately 30.5 m (100 ft) the average surface temperature of seawater seasonally varies between 23.9°C and 29.4°C (75°F and 85°F) or more. In the same regions, deep ocean water (between 762 m and 1280 m (2500 ft and 4200 ft) or more) remains fairly constant at 4.4°C (40°F). Thus, the tropical ocean structure offers a large surface hot water reservoir and a large deep cold water reservoir with a temperature difference between the reservoirs and hot and cold between 1.7°C and 7.2°C ( 35°F and 45°F). This temperature difference (ΔT) remains fairly constant throughout the day and night, with small seasonal changes.
[005] The OTEC process uses the temperature difference between tropical surface and deep sea waters to drive a heat engine to produce electrical energy. OTEC power generation was identified in the late 1970s as a possible renewable energy source that has a low to zero carbon footprint for the energy produced. An OTEC power plant, however, has a low thermodynamic efficiency compared to more traditional high pressure high temperature power generation plants. For example, using average ocean surface temperatures between 26.7°C and 29.4°C (80°F and 85°F) and a constant water temperature of 4.4°C (40°F), the maximum ideal Carnot efficiency of an OTEC power plant will be 7.5 to 8%. In practical operation, the gross energy efficiency of an OTEC power system has been estimated to be approximately half of the Carnot limit, or approximately 3.5 to 4.0%. Furthermore, an analysis carried out by prominent researchers in the 1970s and 1980s, and documented in "Renewable Energy from the Ocean, a Guide to OTEC" William Avery and Chih Wu, Oxford University Press, 1994, indicates that between a quarter and a half ( or more) of the gross electrical energy generated by an OTEC plant operating at a ΔT of 4.4°C (40°F) would be required to operate the water and working fluid pumps and to supply energy for other ancillary needs of the power plant. On this basis, the low total net efficiency of an OTEC power plant converting thermal energy stored in ocean surface waters to net electrical energy has not been a commercially viable energy production option.
[006] An additional factor that results in further reductions in total thermodynamic efficiency is the loss associated with providing the necessary controls over the turbine for precise frequency regulation. This introduces pressure losses into the turbine cycle that limit the work that can be extracted from the hot sea water. The resulting net plant efficiency would then be between 1.5% and 2.0%.
[007] This low net efficiency of OTEC compared to typical efficiencies of heat engines operating at high temperatures and pressures has led to the widely credited assumption by energy planners that OTEC energy is too expensive to compete with more traditional production methods power.
[008] Indeed, parasitic electrical power requirements are specifically important in an OTEC power plant due to the relatively small temperature difference between hot and cold water. To obtain maximum heat transfer between warm seawater and working fluid, and between cold seawater and working fluid, large heat exchange surface areas are required, together with high fluid velocities. Increasing any of these factors can increase the parasitic load on the OTEC plant, thereby decreasing net efficiency. An inefficient heat transfer system that maximizes energy transfer at the limited temperature differential between seawater and the working fluid would increase the commercial viability of an OTEC power plant.
[009] In addition to the relatively low efficiencies with apparently large inherent parasitic loads, the operating environment of OTEC plants presents design and operation challenges that also diminish the commercial viability of such operations. As previously mentioned, the hot water needed for the OTEC heat engine is found on the ocean surface at a depth of 100 feet (30.5 m) or less. The constant source of cold water to cool the OTEC engine is found at depths between 822 m and 1280 m (2700 ft and 4200 ft) or more. Such depths are not typically found near population centers or even land masses. An offshore power plant is required.
[0010] Whether the plant is floating or fixed to a submerged structure, a long cold water inlet pipe of 610 m (2000 ft) or longer is required. Furthermore, due to the large volume of water required in commercially viable OTEC operations, the cold water inlet pipe requires a large diameter (typically between 1.8 and 10.7 m (6 and 35 ft) or more). Suspending a large diameter pipe from an offshore structure presents stability, connection and construction challenges that previously pushed OTEC costs beyond commercial viability.
[0011] In addition, a pipe that has a significant length to diameter ratio that is suspended in a dynamic ocean environment may be subject to variable ocean currents and temperature differences along the length of the pipe. Bend stresses and vortex path along the tube also present challenges. Furthermore, surface influences such as wave action present additional challenges such as the connection between the tube and the floating platform. A cold water pipe inlet system that has desirable performance, connection, and construction consideration would increase the commercial viability of an OTEC power plant.
[0012] The environmental concerns associated with an OTEC plant have also been an impediment to OTEC operations. Traditional OTEC systems aspirate large volumes of nutrient-rich cold water from deep ocean and discharge this water to or near the surface. Such a discharge can affect, in a positive or adverse manner, the ocean environment near the OTEC plant impacting schools of fish and reef systems that may be undercurrent to the OTEC discharge. SUMMARY
[0013] In some aspects, a power generation plant uses ocean thermal energy conversion processes as an energy source.
[0014] Additional aspects relate to an offshore OTEC power plant that has improved overall efficiencies with reduced parasitic loads, greater stability, lower construction and operating costs, and improved environmental footprint. Other aspects include large volume water conduits that are integral with the floating structure. The modularity and compartmentalization of the multi-stage OTEC heat engine reduces construction and maintenance costs, limits off-grid operation and improves operating performance. Still further features provide a floating platform that has a structurally integrated heat exchange compartment and provides low platform movement due to wave action. The integrated floating platform can also provide an efficient flow of hot water or cold water through the multi-stage heat exchanger, increasing efficiency and reducing parasitic energy demand. Associated systems can promote an environmentally neutral thermal footprint by discharging hot and cold water in appropriate depth/temperature ranges. The energy extracted in the form of electricity reduces the ocean's gross temperature.
[0015] Additional aspects refer to a floating, low oscillation OTEC power plant that has a high efficiency, multi-stage heat exchange system, in which the hot and cold water supply conduits and the heat exchangers are structurally integrated into the platform or floating structure of the power plant.
[0016] In one aspect, a multistage heat exchange system includes: a first stage heat exchange chassis comprising one or more open flow plates in fluid communication with a first working fluid flowing through an internal passage in each of the one or more open flow plates; a second stage heat exchange chassis vertically aligned with the first stage heat exchange chassis, the second stage heat exchange chassis comprising one or more open flow plates in fluid communication with a second working fluid which flows through an internal passage in each of the one or more open flow plates. A non-working fluid flows first through the first-stage heat exchange chassis and around each of the one or more open flow plates therein for a heat exchange with the first working fluid and secondly through the heat exchanger chassis. second stage heat exchange in and around each of the one or more open flow plates for a heat exchange with the second working fluid.
[0017] In one aspect a multistage heat exchange system includes: a first stage heat exchange chassis comprising one or more open flow plates, each plate comprising an outer surface surrounded by a non-working fluid and an internal passage in fluid communication with a first working fluid flowing through the internal passage; a second-stage heat exchange chassis vertically aligned with the first-stage heat exchange chassis, the second-stage heat exchange chassis comprising one or more open flow plates comprising an outer surface surrounded by the non-fluid. working and an internal passage in fluid communication with a second working fluid flowing through the internal passage; a third-stage heat exchange chassis vertically aligned with the second-stage heat exchange chassis, the third-stage heat exchange chassis comprising one or more open flow plates comprising an outer surface surrounded by the non-fluid. work and an internal passage in fluid communication with a third working fluid flowing through the internal passage; a fourth-stage heat exchange chassis vertically aligned with the third-stage heat exchange chassis, the fourth-stage heat exchange chassis comprising one or more open flow plates comprising an outer surface surrounded by the non-fluid. working and an internal passage in fluid communication with a fourth working fluid flowing through the internal passage. The non-working fluid flows through the first-stage heat exchange chassis for a thermal interaction with the first working fluid before flowing through the second-stage heat exchange chassis for a thermal interaction with the second working fluid . The non-working fluid flows through the second-stage heat exchange chassis for a thermal interaction with the second working fluid before flowing through the third-stage heat exchange chassis for a thermal interaction with the third working fluid . The non-working fluid flows through the third-stage heat exchange chassis for a thermal interaction with the third working fluid before flowing through the fourth-stage heat exchange chassis for a thermal interaction with the fourth working fluid .
[0018] In one aspect, an open flow heat exchange cabinet includes: a first open flow heat exchange plate comprising: an outer surface in fluid communication with and surrounded by a non-working fluid; and an internal passage in fluid communication with a working fluid flowing through the internal passage; one or more second open flow heat exchanger plates horizontally aligned with the first open flow heat exchanger plate, each of the one or more second open flow heat exchanger plates comprising: a communicating outer surface of fluid with and surrounded by a non-working fluid; and an internal passage in fluid communication with a working fluid flowing through the internal passage. The first open-flow heat exchange plate is separated from the second heat exchange plate by a gap, the non-working fluid flowing through the gap.
[0019] The embodiments of these systems may include one or more of the following features.
[0020] In some embodiments, the first working fluid is heated to a vapor and the second working fluid is heated to a vapor that has a lower temperature than the first vaporous working fluid. In some cases, the first working fluid is heated to a temperature between 20.6 and 21.7°C (69 and 71°F). In some cases, the second-stage working fluid is heated to a temperature below the first-stage working fluid temperature and between 20.0 to 21.1°C (68 to 70°F).
[0021] In some embodiments, the first working fluid is cooled to a condensed liquid in the first-stage heat exchange chassis and the second working fluid is cooled to a condensed liquid in the second-stage heat exchange chassis, the condensed second-stage working fluid having a higher temperature than the condensed first-stage working fluid. In some cases, the first working fluid is cooled to a temperature between 5.6 and 7.8°C (42 and 46°F). In some cases, the second-stage working fluid is cooled to a higher temperature than the first-stage working fluid and between 7.2 to 8.3°C (45 to 47°F). In some cases, non-working fluid enters the first-stage heat exchange chassis at a first temperature and non-working fluid enters the second-stage heat exchange chassis at a lower second temperature. In some cases, non-working fluid enters the first-stage heat exchange chassis at a temperature between 3.3 and 6.6°C (38 and 44°F) and exits the second-stage heat exchange chassis stage at a temperature between 5.6 and 8.9°C (42 and 48°F).
[0022] In some embodiments, the non-working fluid to working fluid flow ratio is greater than 2:1.
[0023] In some embodiments, the non-working fluid to working fluid flow ratio is between 20:1 and 100:1.
[0024] In some embodiments, the first and second stage heat exchange chassis form first and second stage cabinets and in which the non-working fluid flows from the first cabinet to the second cabinet without pressure loss due to piping.
[0025] In some embodiments, open flow plates reduce pressure losses in the working fluid flow due to the absence of nozzles and/or non-working fluid penetrations through the plate.
[0026] In some embodiments, the working fluids flow path comprises a first flow direction through the non-working fluid flow path and a second flow path direction opposite the first flow path direction.
[0027] In some embodiments, the first and second working fluids are working fluids in an OTEC system. In some cases, the first and second working fluids are ammonia.
[0028] In some embodiments, the non-working fluid is pure water.
[0029] In some embodiments, the open flow plates still comprise front, rear, top and bottom external surfaces and the non-working fluid is in contact with all external surfaces.
[0030] In some embodiments, the first stage chassis further comprises a plurality of open flow plates in horizontal alignment that have a clearance between each plate within the first stage chassis; the second stage chassis further comprises a plurality of open flow plates in horizontal alignment which have a clearance between each plate within the second stage chassis; and the plurality of open flow plates and clearances therebetween in the second stage chassis are vertically aligned with the plurality of open flow plates and clearances therebetween in the first stage chassis to reduce pressure losses in the working fluid flow through of the first and second stage chassis. In some cases, the heat exchange system further includes a rail for suspending each of the plurality of open-flow plates and a plurality of slits to maintain the horizontal position of each of the plurality of open-flow plates.
[0031] In some embodiments, the first working fluid is heated to a vapor; the second working fluid is heated to a vapor having a lower temperature than the first vaporous working fluid; the third working fluid is heated to a vapor that has a lower temperature than the second working fluid; and the fourth working fluid is heated to a lower vapor than the third vapor fluid. In some cases, the first working fluid is heated to a temperature between 20.6 and 21.7°C (69 and 71°F); the second working fluid is heated to a lower temperature than the first working fluid and between 20.0 to 21.1°C (68 to 70°F); the third working fluid is heated to a temperature below the second working fluid and between 18.9 to 20.6°C (66 and 69°F); and the fourth working fluid is heated to a temperature below the third working fluid and between 17.8 to 19.4°C (64 to 67°F).
[0032] In some embodiments, the first working fluid is cooled to a liquid condensed in the first-stage heat exchange chassis; the second working fluid is cooled to a condensed liquid in the second-stage heat exchange chassis and has a higher temperature than the first condensed working fluid; the third working fluid is cooled to a condensed liquid in the third stage heat exchange chassis and has a higher temperature than the second condensed working fluid; and the fourth working fluid is condensed to a liquid in the fourth stage heat exchange chassis and has a higher temperature than the third condensed working fluid. In some cases, the first working fluid is condensed at a temperature between 5.6 and 7.8°C (42 and 46°F); the second working fluid is condensed at a higher temperature than the first working fluid and between 7.2 to 8.3°C (45 and 47°F); the third working fluid is condensed at a higher temperature than the second working fluid and between 7.8 and 9.4°C (46 and 49°F); and the fourth working fluid is condensed at a higher temperature than the third working fluid and between 9.4 and 11.1°C (49 and 52°F).
[0033] In some embodiments, the non-working fluid flows from the first heat exchange chassis to the second heat exchange chassis, from the second heat exchange chassis to the third heat exchange chassis, and from the third chassis heat exchanger for the fourth heat exchanger chassis without pressure losses due to piping.
[0034] In some embodiments, open flow plates reduce pressure losses in the working fluid flow due to the absence of nozzles and/or non-working fluid penetrations through the plate.
[0035] In some embodiments, the working fluids flow path comprises a first flow direction through the non-working fluid flow path and a second flow path direction opposite the first flow path direction.
[0036] In some embodiments, the first stage chassis further comprises a plurality of open flow plates in horizontal alignment that have a clearance between each plate within the first stage chassis; the second stage chassis further comprises a plurality of open flow plates in horizontal alignment which have a clearance between each plate within the second stage chassis; the third stage chassis further comprises a plurality of open flow plates in horizontal alignment which have a clearance between each plate within the third stage chassis; the fourth stage chassis further comprises a plurality of open flow plates in horizontal alignment which have a clearance between each plate within the fourth stage chassis; and the plurality of open flow plates and clearances within each chassis are vertically aligned with the open flow plates and clearances in each of the other chassis of the other stages so as to reduce pressure losses in the working fluid flow through the first and second stage chassis.
[0037] In some embodiments, open flow plates reduce pressure losses in the working fluid flow due to the absence of nozzles and/or non-working fluid penetrations through the plate.
[0038] Further aspects include a floating ocean thermal energy conversion power plant. A low oscillation structure, such as a spar, or modified semi-submersible offshore structure may comprise a first deck portion having structurally integral warm seawater passages, multi-stage heat exchange surfaces, and working fluid passages, wherein the first deck portion provides for the evaporation of the working fluid. A second deck portion is also provided having structurally integral cold seawater passages, multi-stage heat exchange surfaces, and working fluid passages, wherein the second deck portion provides a condensing system for condensing the working fluid from a vapor to a liquid. The first and second deck working fluid passages are in communication with a third deck portion comprising one or more steam turbine driven electrical generators for power generation.
[0039] In one aspect an offshore power generation structure is provided that comprises a submerged portion. The submerged portion further comprises a first deck portion comprising an integral multistage evaporator system, a second deck portion comprising an integral multistage condensing system; and a third deck portion that houses energy generation and transformation equipment. One cold water pipe and one cold water pipe connection.
[0040] In a further aspect, the first deck portion further comprises a first stage hot water passageway structure that forms a high volume hot water conduit. The first deck portion also comprises a first-stage working fluid passage arranged in cooperation with the structural first-stage hot water passageway to heat a working fluid to a steam. The first deck portion also comprises a first stage hot water discharge directly coupled to a structural second stage hot water passage. The second-stage hot-water structure passage forms a high-volume hot water conduit and comprises a second-stage hot water inlet coupled to the first-stage hot water discharge. The arrangement of the first-stage hot water discharge to the second-stage hot water inlet provides a low pressure drop in the hot water flow between the first and second stages. The first deck portion also comprises a second stage working fluid passage arranged in cooperation with the structural second stage hot water passageway to heat the working fluid to a steam. The first deck portion also comprises a second stage hot water discharge.
[0041] In a further aspect, the submerged portion further comprises a second deck portion comprising a first stage cold water passageway structure that forms a high volume cold water conduit. The first stage cold water passage further comprises a first stage cold water inlet. The second deck portion also comprises a first-stage working fluid passage in communication with the first-stage working fluid passage of the first deck portion. The first-stage working fluid passage of the second deck portion in cooperation with the structural first-stage cold water passageway cools the working fluid into a liquid. The second deck portion also comprises a first stage cold water discharge directly coupled to a structural second stage cold water passage that forms a high volume cold water conduit. The structural second stage cold water passage comprises a second stage cold water inlet. The first stage cold water discharge and the second stage cold water inlet are arranged to provide a low pressure drop in the cold water flow from the first stage cold water discharge to the second stage cold water inlet. The second deck portion also comprises a second-stage working fluid passage in communication with the second-stage working fluid passage of the first deck portion. The second stage working fluid passage in cooperation with the structural second stage cold water passage cools the working fluid within the second stage working fluid passage to a liquid. The second deck portion also comprises a second stage cold water discharge.
[0042] In a further aspect, the third deck portion may comprise a first and a second steam turbine, wherein the first-stage working fluid passage of the first deck portion is in communication with the first turbine and the passage. of stage working fluid from the first deck portion is in communication with the second turbine. The first and second turbines can be coupled to one or more electrical generators.
[0043] In still further aspects, an offshore power generation structure is provided which comprises a submerged portion, the submerged portion further comprises a fourth stage evaporator portion, a fourth stage condenser portion, a power generation portion fourth stage, a cold water pipe connection, and a cold water pipe.
[0044] In one aspect, the fourth stage evaporator portion comprises a hot water conduit that includes, a first stage heat exchange surface, a second stage heat exchange surface, a heat exchange surface of third stage and a fourth stage heat exchange surface. The hot water conduit comprises a vertical structural member of the submerged portion. The first, second, third and fourth heat exchange surfaces are in cooperation with the first, second, third and fourth stage portions of a working fluid conduit, wherein a working fluid flows through the fluid conduit The working temperature is heated to a steam in each of the first, second, third, and fourth stage portions.
[0045] In one aspect, the fourth stage condenser portion comprises a cold water conduit that includes a first stage heat exchange surface, a second stage heat exchange surface, a third stage heat exchange surface stage, and a fourth stage heat exchange surface. The cold water conduit comprises a vertical structural member of the submerged portion. The first, second, third and fourth heat exchange surfaces are in cooperation with the first, second, third and fourth stage portions of a working fluid conduit, wherein a working fluid flows through the working fluid conduit. work is cooled to a liquid in each of the first, second, third, and fourth stage portions, with a progressively higher temperature in each successive stage.
[0046] In yet another aspect, the working fluid conduits of the first, second, third, and fourth stages of the evaporator portion are in communication with the first, second, third and fourth steam turbines, wherein the fluid conduit first-stage working fluid of the evaporator portion is in communication with a first steam turbine and discharges into the fourth-stage working fluid conduit of the condenser portion.
[0047] In yet another aspect, the working fluid conduits of the first, second, third, and fourth stages of the evaporator portion are in communication with the first, second, third and fourth steam turbines, wherein the fluid conduit second-stage working fluid of the evaporator portion is in communication with a second steam turbine and discharges to the third-stage working fluid conduit of the condenser portion.
[0048] In yet another aspect, the working fluid conduits of the first, second, third, and fourth stages of the evaporator portion are in communication with the first, second, third and fourth steam turbines, wherein the fluid conduit third-stage working fluid of the evaporator portion is in communication with a third steam turbine and discharges into the second-stage working fluid conduit of the condenser portion.
[0049] In yet another aspect, the working fluid conduits of the first, second, third, and fourth stages of the evaporator portion are in communication with the first, second, third and fourth steam turbines, wherein the fluid conduit fourth-stage working fluid of the evaporator portion is in communication with a fourth steam turbine and discharges into the first-stage working fluid conduit of the condenser portion.
[0050] In still a further aspect, a first electric generator is driven by the first turbine, the fourth turbine, or a combination of the first and fourth turbines.
[0051] In yet a further aspect, a second electrical generator is driven by the second turbine, the third turbine, or a combination of both the second and third turbines.
[0052] Additional aspects may incorporate one or more of the following characteristics: the first and fourth turbines or the second and third turbines produce between 9 MW and 60 MW of electrical energy; the first and second turbines produce approximately 55 MW of electrical energy; the first and second turbines form one of a plurality of turbogenerator assemblies in an Ocean Thermal Energy Conversion power plant; the first-stage hot water inlet is free from interference from the second-stage cold water discharge; the first-stage cold water inlet is free from interference from the second-stage hot water discharge; the working fluid within the first or second stage working fluid passages comprises a commercial refrigerant. The working fluid comprises any fluid with suitable thermodynamic properties such as ammonia, propylene, butane, R-134, or R-22; the working fluid within the first and second stage working fluid passages increases in temperature between -11.1°C and -4.4°C (12°F and 24°F); a first working fluid flows through the first-stage working fluid passage and a second working fluid flows through the second-stage working fluid passage, wherein the second working fluid enters the second steam turbine at a temperature lower than the first working fluid enters the first steam turbine. The first working fluid in the first and second stage working fluid passages decreases in temperature between -11.1°C and -4.4°C (12°F and 24°F); a first working fluid flows through the first-stage working fluid passage and a second working fluid flows through the second-stage working fluid passage, wherein the second working fluid enters the second deck portion at a temperature lower than the first working fluid enters the second deck portion.
[0053] Additional aspects may also incorporate one or more of the following characteristics: the hot water flowing within the structural first or second stage hot water passage comprises hot sea water, geothermally heated water, solar heated reservoir water; heated industrial cooling water, or a combination thereof; hot water flows between 1,900 and 22,712 m3/min (500,000 and 6,000,000 gpm); hot water flows at 20,590 m3/min (5,440,000 gpm); hot water flows between 136,077,720 kg/h (300,000,000 lb/h) and 453,592,400 kg/h (1,000,000,000 lb/h); hot water flows at 1,233,771 kg/h (2,720,000 lb/h); the cold water flowing within the structural first or second stage cold water passage comprises cold sea water, cold fresh water, cold ground water, or a combination thereof; hot water flows between 950 and 11,000 m3/min (250,000 and 3,000,000 gpm); hot water flows at 12,900 m3/min (3,420,000 gpm); hot water flows between 56,699,050 kg/h (125,000,000 lb/h) and 793,786,700 kg/h (1,750,000,000 lb/h); hot water flows at 775,643 kg/h (1,710,000 lb/h).
[0054] Aspects may also incorporate one or more of the following characteristics: the offshore structure is a low oscillation structure; the offshore structure is a floating spar structure; the offshore structure is a semi-submersible structure.
[0055] A still further aspect may include a high volume, low speed heat exchange system for use in an ocean thermal energy conversion electrical plant comprising: a first stage cabinet further comprising a first flow passage of water for heat exchange with a working fluid; and a first working fluid passage; and a second-stage cabinet coupled to the first-stage cabinet, further comprising a second water flow passage for exchanging heat with a working fluid and coupled to the first water flow passage in a manner to limit pressure drop. of water flowing from the first water flow passage to the second water flow passage; and a second working fluid passage. The first and second stage cabinets comprise structural members of the power plant.
[0056] In one aspect, water flows from the first stage cabinet to the second stage cabinet and the second stage cabinet is under the first stage cabinet evaporator. In another aspect, water flows from the first stage cabinet to the second stage cabinet and the second stage cabinet is above the first stage cabinet on the condensers and below the first stage cabinet on the evaporators.
[0057] In yet a further aspect, a cold water pipe provides cold water from ocean depths to the OTEC cold water inlet. The cold water inlet may be on the second deck portion of the submerged portion of the OTEC plant. The cold water pipe can be a segmented construction. The cold water tube can be a continuous tube. The cold water pipe may comprise: an elongated tubular structure having an outer surface, an upper end and a lower end. The tubular structure may further comprise a plurality of first and second stave segments wherein each stave segment has an upper portion and a lower portion, and wherein the upper portion of the second stave segment is offset from the upper portion of the first stave segment. stave. The cold water tube may include a row or tape at least partially spirally wound around the outer surface. The first and second staves and/or row may comprise polyvinyl chloride (PVC), chlorinated polyvinyl chloride (CPVC), fiber reinforced plastic (FRP), reinforced polymer mortar (RPMP), polypropylene (PP), polyethylene (PE), cross-linked high density polyethylene (PEX), polybutylene (PB), acrylonitrile butadiene styrene (ABS); polyester, fiber reinforced polyester, vinyl ester, reinforced vinyl ester, concrete, ceramic, or a composite of one or more of these.
[0058] Additional aspects include a dynamic connection between the submerged portion of the OTEC plant and the cold water pipe. The dynamic connection can withstand the weight and dynamic forces of the cold water pipe while it is suspended from the OTEC platform. The dynamic tube connection can allow for relative movement between the OTEC platform and the cold water tube. Relative movement can be between 0.5° and 30° from vertical. In one aspect the relative motion can be between 0.5° and 5° from vertical. The dynamic tube connection can include a spherical or arcuate bearing surface.
[0059] In some arrangements, a static connection is provided between the submerged portion of the OTEC plant and the cold water pipe. In these systems, the top of the cold water pipe can be tapered and is recessed into a tapered receptacle using lines and winches lowered from inside the spar. The cold water pipe can be retained using locking mechanisms so that the lines can be detached for use in lifting equipment from the lower decks of the stringer to the half-body decks.
[0060] In one aspect, a submerged standpipe connection comprises a floating structure having a standpipe receiving compartment, wherein the receiving compartment has a first diameter, a standpipe for insertion into the pipe receiving compartment, the vertical tube having a second diameter smaller than the first diameter of the tube receiving compartment; a support surface; and one or more retainers operable with the bearing surface, wherein the retainers define a diameter that is different than the first or second diameter when in contact with the bearing surface.
[0061] Further details of other aspects are described in US Patent Application Number 13/209,893 (Protocol No. 25667-016001) entitled Ocean Thermal Energy Conversion Power Plant - Cold Water Pipe Connection, and Patent Application US Number 13/209,944 (Protocol No. 25667-014001) entitled Transferring Heat Between Fluids, filed concurrently with the present application.
[0062] Aspects may have one or more of the following advantages: OTEC energy production requires little or no fuel cost for energy production; the low pressures and low temperatures involved in the OTEC heat engine reduce component costs and require common materials compared to the high-cost exotic materials used in high-pressure, high-temperature power generation plants; plant reliability is comparable to commercial refrigeration systems, which operate continuously for several years without significant maintenance; reduced construction times compared to high pressure, high temperature plants; and safe, environmentally benign energy production and operation. Additional advantages can include, increased net efficiency compared to traditional OTEC systems, lower electrical sacrificial charges; reduced pressure loss in hot and cold water passages as well as working fluid flow passages; modular components; less frequent off-grid production time; low oscillation and reduced susceptibility to wave action; cooling water discharge below surface levels, interference-free hot water inlet from cold water discharge.
[0063] Details of one or more modalities are shown in the accompanying drawings and in the description below. Other features, objects, and advantages will be apparent from the description and drawings, and from the claims. DESCRIPTION OF DRAWINGS
[0064] Figure 1 illustrates an exemplary prior art OTEC heat engine.
[0065] Figure 2 illustrates an exemplary prior art OTEC power plant.
[0066] Figure 3 illustrates an OTEC structure.
[0067] Figure 4 illustrates a deck plan of a heat exchanger deck.
[0068] Figure 5 illustrates a heat exchanger cabinet.
[0069] Figure 6A illustrates a conventional heat exchange cycle.
[0070] Figure 6B illustrates a multistage cascaded heat exchange cycle.
[0071] Figure 6C illustrates a hybrid cascade multistage heat exchange cycle.
[0072] Figure 6D illustrates the evaporator pressure drop and the associated energy production.
[0073] Figures 7A and B illustrate an exemplary OTEC heat engine.
[0074] Figure 8 illustrates a conventional shell and tube heat exchanger.
[0075] Figure 9 illustrates a conventional plate heat exchanger.
[0076] Figure 10 illustrates a heat exchanger cabinet.
[0077] Figure 11 illustrates a perspective view of a heat exchange plate arrangement.
[0078] Figure 12 illustrates a perspective view of a heat exchange plate arrangement.
[0079] Figure 13 illustrates a side view of a heat exchange plate configuration.
[0080] Figure 14 illustrates a P-h diagram of a conventional high temperature steam cycle.
[0081] Figure 15 illustrates a P-h diagram of a heat cycle.
[0082] Figure 16 illustrates an embodiment of a heat exchanger plate.
[0083] Figure 17 illustrates an embodiment of a heat exchange plate.
[0084] Figure 18 illustrates a portion of a heat exchange plate.
[0085] Figures 19A and 19B illustrate an embodiment of a pair of heat exchanger plates.
[0086] Figure 20A and 20B illustrate an embodiment of a pair of heat exchanger plates.
[0087] Like reference symbols in the various drawings indicate like elements. DETAILED DESCRIPTION
[0088] This description refers to the generation of electrical energy using an Ocean Thermal Energy Conversion (OTEC) technology. Aspects refer to a floating OTEC power plant that has improved overall efficiencies with reduced parasitic loads, greater stability, and lower construction and operating costs compared to conventional OTEC power plants. Other aspects include large volume water conduits that are integral with the floating structure. The modularity and compartmentalization of the multi-stage OTEC heat engine reduces construction and maintenance costs, limits off-grid operation and improves operating performance. Still additional features provide a floating platform that has integrated heat exchange compartments and provides low platform movement due to wave action. The integrated floating platform can also provide an efficient flow of hot water or cold water through the multi-stage heat exchanger, increasing efficiency and reducing parasitic energy demand. Aspects promote a neutral thermal footprint by discharging hot and cold water in appropriate depth/temperature ranges. The energy extracted in the form of electricity reduces the raw temperature for the ocean.
[0089] OTEC is a process that uses thermal energy from the sun that is stored in the Earth's oceans to generate electricity. OTEC uses the temperature difference between the warmer upper ocean layer and the cooler, deep ocean water. Typically this difference is at least 20°C (36°F). These conditions exist in tropical areas, approximately between the Tropic of Capricorn and the Tropic of Cancer, or up to 20° north and south latitude. The OTEC process uses the temperature difference to power a Rankine cycle, with hot surface water serving as the heat source and cold deep water serving as the heat sink. Rankine cycle turbines drive generators which produce electrical energy.
[0090] Figure 1 illustrates a typical OTEC Rankine cycle heat engine 10, which includes a hot seawater inlet 12, an evaporator 14, a hot seawater outlet 15, a turbine 16, an inlet of cold sea water 18, a condenser 20, a cold sea water outlet 21, a working fluid conduit 22 and a working fluid pump 24.
[0091] In operation, the thermal machine 10 may utilize any one of a number of working fluid, for example, commercial refrigerants such as ammonia. Other working fluids can include propylene, butane, R-22, and R-134a. Other commercial refrigerants can be used. Warm sea water between approximately 23.9°C and 29.4°C (75°F and 85°F), or more, is sucked from the ocean surface or just below the ocean surface through the water inlet of the hot sea 12 and in turn heats the ammonia working fluid passing through the evaporator 14. The ammonia boils at a vapor pressure at approximately 0.94 MPascal (9.3 atm). Steam is carried along working fluid conduit 22 to turbine 16. Ammonia vapor expands as it passes through turbine 16, producing energy to drive an electrical generator 25. Ammonia vapor then enters condenser 20 where this is cooled to a liquid by cold seawater aspirated from a deep ocean depth of approximately 914 m (3000 ft). Cold seawater enters the condenser at a temperature of approximately 4.4°C (40°F). The vapor pressure of the ammonia working fluid at the temperature inside condenser 20, approximately 10.6°C (51°F), is 0.62 MPascal (6.1 atm). Thus, a significant pressure difference is available to drive turbine 16 and generate electrical energy. As the ammonia working fluid condenses, the liquid working fluid is pumped back to the evaporator 14 by the working fluid pump 24 through the working fluid conduit 22.
[0092] The heat engine 10 of Figure 1 is essentially the same as the Rankine cycle of most steam turbines, except that the OTEC differs using different working fluids and lower temperatures and pressures. Heat engine 10 in Figure 1 is also similar to commercial refrigeration plants, except that the OTEC cycle runs in the opposite direction so that a heat source (eg warm ocean water) and a cold heat sink ( for example, deep ocean water) are used to produce electricity.
[0093] Figure 2 illustrates the components of a floating OTEC 200 power plant, which include: the ship or platform 210, a hot sea water inlet 212, a hot water pump 213, an evaporator 214, an outlet of hot sea water 215, a turbogenerator 216, a cold water pipe 217, a cold water inlet 218, a cold water pump 219, a condenser 220, a cold water outlet 221, a working fluid conduit 222 , a working fluid pump 224, and a pipe connection 230. The OTEC 200 plant may also include electrical generation, transformation and transmission systems, position control systems such as propulsion, impellers, or mooring systems, as well. as various auxiliary and support systems (eg, personnel accommodations, emergency power, potable water, black and gray water, firefighting, damage control, reserve flotation, and other common on-board or marine systems).
[0094] OTEC power plant implementations using the basic heat engine and system of Figures 1 and 2 have a relatively low total efficiency of 3% or less. Due to this low thermal efficiency, OTEC operations require large amounts of water to flow through the power system per kilowatt of energy generated. This in turn requires large heat exchangers that have large heat exchange surface areas.
[0095] Such large volumes of water and large surface areas require considerable pumping capacity in the hot water pump 213 and cold water pump 219, reducing the net electrical energy available for distribution to a land-based installation or industrial purposes. on board. Furthermore, the limited space of most surface vessels does not easily facilitate large volumes of water being directed to and flowing through the evaporator or condenser. Indeed, large volumes of water require large diameter tubes and conduits. Placing such structures within a limited space requires multiple bends to accommodate other machinery. And the limited space of ships or surface structures does not easily facilitate the large surface area of heat exchange required for maximum efficiency from an OTEC plant. Thus OTEC systems and the ship or platform have traditionally been large and expensive. This has led to an industry conclusion that OTEC operations are a high-cost, low-yield energy production option when compared to other energy production options that utilize higher temperatures and pressures.
[0096] The systems and proposals described here solve the technical challenges in order to improve the efficiency of OTEC operations and reduce the cost of construction and operation.
[0097] The ship or platform 210 requires low movements to limit the dynamic forces between the cold water pipe 217 and the ship or platform 210 and provide a benign operating environment for the OTEC equipment on the platform or ship. The vessel or platform 210 must also support incoming cold and hot water volume flows (218 and 212), bringing sufficient cold and hot water at appropriate levels to ensure OTEC process efficiency. The ship or platform 210 must also allow the discharge of cold and hot water through cold and hot water outlets (221 and 215) well below the waterline of the ship or platform 210 to prevent thermal recirculation in the ocean surface layer. . In addition, ship or platform 210 must survive heavy weather without disrupting power generation operations.
[0098] The OTEC 10 heat engine described here uses a highly efficient thermal cycle for maximum efficiency and energy production. Heat transfer in boiling and condensing processes, as well as heat exchanger materials and design, limit the amount of energy that can be extracted from each kilogram of warm seawater. The heat exchangers used in the evaporator 214 and condenser 220 utilize high volumes of hot and cold water flow with low head loss to limit parasitic loads. Heat exchangers also provide high heat transfer coefficients to improve efficiency. Heat exchangers incorporate materials and designs modeled for hot and cold water inlet temperatures to improve efficiency. Heat exchanger design can utilize a simple construction method with low amounts of material to reduce cost and volume.
[0099] The 216 turbogenerators are highly efficient with low internal losses and can also be modeled for the working fluid to improve efficiency.
[00100] Figure 3 illustrates an implementation of an OTEC system that improves the efficiency of previous OTEC power plants and overcomes many of the technical challenges associated with them. This implementation comprises a spar for the ship or platform, with heat exchangers and associated hot and cold water piping integral with the spar.
[00101] The OTEC 310 spar houses an integral multistage heat exchange system for use with an OTEC power generation plant. Spar 310 includes a submerged portion 311 below water line 305. Submerged portion 311 comprises a hot water inlet portion 340, an evaporator portion 344, a hot water discharge portion 346, a condenser portion 348, a cold water inlet portion 350, a cold water pipe 351, a cold water discharge portion 352, a machinery deck portion 354, and a deck housing 360.
[00102] In operation, hot seawater between 23.9°C and 29.4°C (75°F and 85°F) is sucked through the hot water inlet portion 340 and flows down the stringer through of structurally integral hot water ducts (not shown). Due to the high volume water flow requirements of OTEC thermal machines the hot water conduits direct the flow to the 344 evaporator portion between 1,892.7 and 22,712 m3/min (500,000 and 6,000,000 gpm). Hot water pipes have a diameter between 1.8 m and 10.7 m (6 ft and 35 ft) or more. Because of this size, the hot water conduits are vertical structural members of the spar 310. The hot water conduits may be large diameter tubes structurally joined to the spar and of sufficient strength to contribute to the overall strength of the vertical support spar 310. Alternatively, the hot water conduits can be integral passages with the construction of the spar 310.
[00103] The hot water then flows through the evaporator portion 344 which houses one or more stacked multi-stage heat exchangers to heat a working fluid to a steam. The hot sea water is then discharged from stringer 310 through hot water discharge 346. The hot water discharge can be located or directed through a hot water discharge pipe to a depth in or near an ocean thermal layer. which is at approximately the same temperature as the hot water discharge temperature to limit environmental impacts. The hot water discharge can be directed deep enough to avoid thermal recirculation with either hot water inlet or cold water inlet.
[00104] Cold sea water is sucked from a depth between 762 m and 1280 m (2500 ft and 4200 ft) or more, at a temperature of approximately 4.4°C (40°F), through the cold water pipe 351. Cold seawater enters spar 310 through cold water inlet portion 350. Due to the high volume water flow requirements of OTEC heat engines, cold seawater conduits direct the flow to the portion. of condenser 340 between 1,892.7 m3/min and 13,248,942 m3/min (500,000 gpm and 3,500,000 gpm). Such cold seawater conduits have a diameter between 1.8 m and 10.7 m (6 ft and 35 ft) or more. Due to this size, the cold seawater conduits are vertical structural members of the spar 310. The cold water conduits can be large diameter tubes structurally joined to the spar and of sufficient strength to contribute to the overall strength of the spar 310. Alternatively , the cold water conduits can be integral passages with the construction of the spar 310.
[00105] The cold seawater then flows upward to the stacked multistage condenser portion 348, where the cold seawater cools a working fluid to a liquid. The cold seawater is then discharged from the spar 310 via the cold seawater discharge 352.
[00106] The machinery deck portion 354 may be positioned vertically between the evaporator portion 344 and the condenser portion 348. Positioning the machinery deck portion 354 under the evaporator portion 344 allows an almost in-line hot water flow straight from the inlet, through the multistage evaporators, and to the discharge. Positioning the machinery deck portion 354 above the condenser portion 348 allows for an almost straight-line cold water flow from the inlet, through the multi-stage condensers, and to the discharge. Machinery deck portion 354 includes turbogenerators 356. In operation, hot working fluid heated to a steam flows from evaporator portion 344 to one or more turbogenerators 356. The working fluid expands within turbogenerator 356 thereby driving a turbine for the production of electricity. The working fluid then flows to the condenser portion 348 where it is cooled to a liquid and pumped to the evaporator portion 344.
[00107] Figure 4 illustrates an implementation of an OTEC system in which a plurality of multistage heat exchangers 420 are arranged around the periphery of the OTEC 410 spar. The heat exchangers 420 can be evaporators or condensers used in an OTEC thermal machine. The peripheral arrangement of heat exchangers can be used with the evaporator portion 244 or the condenser portion 348 of an OTEC spar platform. The peripheral arrangement can support any number of heat exchangers (eg 1 heat exchanger, between 2 and 8 heat exchangers, 8-16 heat exchangers, 16-32 heat exchangers, or 32 or more heat exchangers). One or more heat exchangers may be peripherally disposed on a single deck or on multiple decks (for example, on 2, 3, 4, 5, or 6 or more decks) of the OTEC 410 spar. One or more heat exchangers may be peripherally offset between two or more decks so that no heat exchangers are vertically aligned on each other. One or more heat exchangers may be peripherally arranged so that heat exchangers on one deck are vertically aligned with heat exchangers on another adjacent deck.
[00108] Individual heat exchangers 420 may comprise a multi-stage heat exchanger system (eg 2, 3, 4, 5, or 6 or more heat exchange systems). In some embodiments, the individual 420 heat exchangers are heat exchanger enclosures constructed to provide a low pressure loss in the warm seawater flow, the cold seawater flow, and the working fluid flow through the exchanger. of heat.
[00109] Referring to Figure 5, an embodiment of a heat exchanger cabinet 520 includes multiple heat exchange stages 521, 522, 523 and 524. In some implementations, stacked heat exchangers accommodate hot seawater flowing into low through the cabinet, from first stage evaporator 521, to second stage evaporator 522, to third stage evaporator 523, to fourth stage evaporator 524. In another modality, the stacked heat exchange cabinet, the water of the cold sea flows upward through the first-stage condenser cabinet 531, to the second-stage condenser 532, to the third-stage condenser 533, to the fourth-stage condenser 534. The working fluid flows through the supply conduits of working fluid 538 and working fluid discharge conduits 539. In one embodiment, the working fluid conduits 538 and 539 enter and exit each heat exchanger stage horizontally. compared to the vertical flow of warm seawater or cold seawater. The 520 heat exchanger cabinet's vertical multi-stage heat exchange design facilitates a vessel design (eg spar) and integrated heat exchanger, removes the requirement to interconnect a pipeline between the heat exchanger stages, and ensures that virtually all heat exchanger system pressure drop occurs over the heat transfer surface.
[00110] Surface heat transfer efficiency can be improved by using a surface shape, treatment and spacing as described herein. A selection of material such as aluminum alloys offers superior economic performance over traditional titanium-based designs. The heat transfer surface may comprise Series 100, Series 3000, or Series 5000 aluminum alloys. The heat transfer surface may comprise titanium and titanium alloys.
[00111] It has been found that the multistage heat exchanger cabinet allows for a high transfer of energy to the seawater working fluid within the relatively low available temperature differential of the OTEC heat engine. The thermodynamic efficiency of any OTEC power plant is a function of how close the temperature of the working fluid approaches that of seawater. The physics of heat transfer dictate that the area required to transfer energy increases as the temperature of the working fluid approaches that of seawater. Increasing the velocity of seawater can increase the heat transfer coefficient to compensate for the increase in surface area. However, increasing the velocity of seawater can greatly increase the power required to pump, thereby increasing the parasitic electrical load on the OTEC plant.
[00112] Figure 6A illustrates an OTEC cycle in which the working fluid is boiled in a heat exchanger using hot surface seawater. The fluid properties in this conventional Rankine cycle are constrained by the boiling process which limits the outgoing working fluid to approximately -16.1°C (3°F) below the temperature of warm seawater. In a similar fashion, the condensing side of the cycle is limited to being no closer than -16.7°C (2°F) higher than the outgoing cold seawater temperature. The total available temperature drop for the working fluid is approximately -11.1°C (12°F) (between 20°C and 13.3°C (68°F and 56°F)).
[00113] It has been found that a cascading multi-stage OTEC cycle allows working fluid temperatures to more closely coincide with those of seawater. This increase in temperature differential increases the amount of work that can be done by the turbines associated with the OTEC heat engine.
[00114] Figure 6B illustrates a cascaded multi-stage OTEC cycle that uses multiple boiling and condensing steps to expand the available working fluid temperature drop. Each step requires an independent heat exchanger, or a dedicated heat exchanger stage in heat exchanger cabinet 520 of Figure 5. The cascaded multi-stage OTEC cycle of Figure 6B allows you to match the output of the turbines to the loads of expected pumping for seawater and working fluid. This highly efficient project would require dedicated and customized turbines.
[00115] Figure 6C illustrates a hybrid yet still efficient cascade OTEC cycle that facilitates the use of identical equipment (eg, turbines, generators, pumps) while retaining the thermodynamic efficiencies or optimization of the true cascade arrangement of Figure 6B . In the hybrid cascade cycle of Figure 6C, the temperature differential available for the working fluid ranges from approximately -7.8°C (18°F) to approximately -5.6°C (22°F). This narrow range allows the turbines in the heat engine to have identical performance specification, thereby lowering construction and operating costs.
[00116] System performance and power output are greatly increased using the hybrid cascade cycle in an OTEC power plant. Table A compares the performance of the conventional cycle of Figure 6A with that of the hybrid cascade cycle of Figure 6C. Table A

[00117] Using the four-stage hybrid cascade heat exchange cycle reduces the amount of energy that needs to be transferred between the fluids. This in turn serves to reduce the amount of heat exchange surface that is required.
[00118] The performance of heat exchangers is affected by the available temperature difference between fluids as well as the heat transfer coefficient on the heat exchanger surfaces. The heat transfer coefficient generally varies with the velocity of the fluid across the heat transfer surfaces. Higher fluid speeds require higher pumping power, thereby reducing the plant's net efficiency. A hybrid cascade multi-stage heat exchange system facilitates lower fluid speeds and increased plant efficiencies. The stacked hybrid cascade heat exchange design also makes it easy to lower pressure drops across the heat exchanger. The vertical plant design also makes it easy to lower the pressure drop across the entire system.
[00119] Figure 6D illustrates the impact of heat exchanger pressure drop on total OTEC power plant generation to supply 100 MW to a power grid. Limiting the pressure drop across the heat exchanger greatly improves the performance of the OTEC power plant. The pressure drop is reduced by providing a ship or platform - integrated heat exchanger system, in which the seawater conduits form the structural members of the ship and allow the flow of seawater from one heat exchanger stage to another in series. An approximate straight-line seawater flow, with low changes towards the inlet to the ship, through the pump, through the heat exchanger cabinets and in turn through each heat exchange stage in series, and finally discharging from the plant, allows a low pressure drop. HYBRID OTEC POWER GENERATION IN CASCADE:
[00120] An integrated multi-stage OTEC power plant can produce electricity using the temperature differential between surface water and deep ocean water in tropical and subtropical regions. Traditional piping extensions to seawater can be eliminated by using the vessel or offshore platform structure as a conduit or flow passage. Alternatively, Alternatively, hot and cold seawater piping extensions may utilize ducts or tubes of sufficient size and strength to provide vertical or other structural support for the vessel or platform. These integral seawater conduit sections or passages serve as structural members of the ship, thereby reducing the requirements for additional steel. As part of the integral seawater passages, the multistage heat exchanger enclosures provide multiple stages of working fluid evaporation without the need for external water nozzles or piping connections. The integrated multi-stage OTEC power plant allows warm and cold seawater to flow in their natural directions. Warm seawater flows downward through the vessel as it is being cooled before being discharged into a cooler part of the ocean. In a similar fashion, cold seawater deep in the ocean flows upward through the ship as it is heated before discharging into a warmer part of the ocean. This arrangement avoids the need for changes in seawater flow direction and the associated pressure losses. The arrangement also reduces the pumping energy required.
[00121] Multistage heat exchanger cabinets allow the use of a hybrid cascade OTEC cycle. These stacks of heat exchangers comprise multiple stages or heat exchanger sections that have seawater passing through them in series to boil or condense the working fluid as appropriate. In the evaporator section, warm seawater passes through a first stage where it boils some of the working fluid as the seawater is cooled. The warm seawater then flows down from the stack into the next heat exchanger stage and boils the additional working fluid at a slightly lower temperature pressure. This occurs sequentially across the entire stack. Each stage or section of the heat exchanger cabinet supplies working fluid vapor to a dedicated turbine that generates electrical energy. Each of the evaporator stages has a corresponding condenser stage at the turbine discharge. Cold seawater passes through the condenser stacks in a reverse order to the evaporators.
[00122] Referring to Figures 7A and 7B, an exemplary 710 multistage OTEC heat engine utilizes a hybrid cascade heat exchange cycle. Hot seawater is pumped from a hot seawater inlet (not shown) by the hot water pump 712, discharging from the pump at approximately 5,150 m3/min (1,360,000 gpm) and at a temperature of approximately 26.1 °C (79°F). All or parts of the hot water conduit in the hot water inlet to the hot water pump, and the hot water pump to the stacked heat exchanger cabinet can form the integral structural members of the vessel.
[00123] From the hot water pump 712, the hot sea water then enters a first-stage evaporator 714 where it boils a first working fluid. Hot water exits the first stage evaporator 714 at a temperature of approximately 24.9°C (76.8°F) and flows down to a second stage evaporator 715.
[00124] Hot water enters the 715 second stage evaporator at approximately 24.9°C (76.8°F) where it boils a second working fluid and exits the 715 second stage evaporator at a temperature of approximately 23, 6°C (74.5°).
[00125] The hot water flows down to a third stage evaporator 716 from the second stage evaporator 715, entering a temperature of approximately 23.6°C (74.5°), where it boils a third working fluid. Hot water exits the third stage evaporator 716 at a temperature of approximately 22.4°C (72.3°F).
[00126] The hot water then flows from the third-stage evaporator 716 down to the fourth-stage evaporator 717, entering a temperature of approximately 22.4°C (72.3°F), where it boils a fourth fluid of Work. The hot water exits the 717 fourth stage evaporator at a temperature of approximately 21.2°C (70.1°F) and then discharges from the ship. Although not shown, the discharge can be directed to a thermal layer at an ocean depth of approximately the same temperature as the discharge temperature of warm seawater. Alternatively, the portion of the power plant that houses the multistage evaporator can be located at a depth within the structure so that the hot water is discharged to an appropriate thermal ocean layer. In some embodiments, the hot water conduit from the fourth stage evaporator to the hot water discharge from the ship may comprise structural members of the ship.
[00127] Similarly, cold seawater is pumped from a cold seawater inlet (not shown) through the cold seawater pump 722, discharging from the pump at approximately 3,236.54 m3/min (855,003 gpm) and at a temperature of approximately 4.4°C (40.0°F). Cold seawater is drawn from ocean depths between approximately 823 and 1280 m (2700 and 4200 ft), or more. The cold water conduit carrying cold sea water from the cold water inlet of the ship to the cold water pump, and from the cold water pump to the first stage condenser may comprise all or part of the ship's structural members .
[00128] From the cold seawater pump 722, the cold seawater enters a first-stage condenser 724, where it condenses the fourth working fluid of the fourth-stage evaporator 717. first stage at a temperature of approximately 6.4°C (43.5°F) and flows upward to a 725 second stage condenser.
[00129] Cold seawater enters second stage condenser 725 at approximately 6.4°C (43.5°F) where it condenses the third working fluid of third stage evaporator 716. of the second stage condenser 725 at a temperature of approximately 8.3°C (46.9°F) and flows upward to a third stage condenser 726.
[00130] Cold seawater enters third-stage condenser 726 at a temperature of approximately 8.3°C (46.9°F) where it condenses the second working fluid of second-stage evaporator 715. Cold sea exits third stage condenser 726 at a temperature of approximately 10.2°C (50.4°F).
[00131] The cold seawater then flows upward from the 726 to a fourth stage condenser 727, entering a temperature of approximately 10.2°C (50.4°F). In the fourth-stage condenser, the seawater curls condenses the first working fluid of the first-stage evaporator 714. The cold seawater then exits the fourth-stage condenser at a temperature of approximately 12.2°C (54.0°C °F) and finally unloads from the ship. The discharge of cold seawater can be directed to a thermal layer at a depth of ocean or at approximately the same temperature as the discharge temperature of cold seawater. Alternatively, the portion of the power plant that houses the multistage condenser can be located at a depth within the structure so that the cold seawater is discharged to an appropriate thermal ocean layer.
[00132] The first working fluid enters the first stage evaporator 714 at a temperature of 13.7°C (56.7°F) where it is heated to a steam with a temperature of 23.7°C (74, 7°F). The first working fluid then flows to the first turbine 731 and then to the fourth stage condenser 727 where the first working fluid is condensed to a liquid having a temperature of approximately 13.6°C (56.5°F). The first liquid working fluid is then pumped through the first working fluid pump 741 back to the first stage evaporator 714.
[00133] The second working fluid enters the 715 second stage evaporator at a temperature of approximately 11.7°C (53.0°F) where it is heated to a vapor. The second working fluid exits second stage evaporator 715 at a temperature of approximately 22.4°C (72.4°F). The second working fluid then flows to a second turbine 732 and then to the third stage condenser 726. The second working fluid exits the third stage condenser at a temperature of approximately 11.7°C (53.0°F) and flows to the working fluid pump 742, which in turn pumps the second working fluid back to the second stage evaporator 715.
[00134] The third working fluid enters the third stage evaporator 716 at a temperature of approximately 9.7°C (49.5°F) where it will be heated to a steam and exits the third stage evaporator 716 at a temperature of approximately 21.2°C (70.2°F). The third working fluid then flows to the third turbine 733 and then to the second stage condenser 725 where the third working fluid is condensed to a fluid at a temperature of approximately 9.7°C (49.5°F). The third working fluid exits the second stage condenser 725 and is pumped back to the third stage evaporator 716 via the third working fluid pump 743.
[00135] The fourth working fluid enters the 717 fourth stage evaporator at a temperature of approximately 7.8°C (46.0°F) where it will be heated to a vapor. The fourth working fluid exits the fourth stage evaporator 717 at a temperature of approximately 20.0°C (68.0°F) and flows into a fourth turbine 734. The fourth working fluid exits the fourth turbine 734 and flows to the first 724 condenser where it is condensed to a liquid with a temperature of approximately 7.8°C (46.0°F). The fourth working fluid exits the first stage condenser 724 and is pumped back to the fourth stage evaporator 717 via the fourth working fluid pump 744.
[00136] The first turbine 731 and the fourth turbine 734 cooperatively drive a first generator 751 and form the first turbogenerator pair 761. The first turbogenerator pair will produce approximately 25 MW of electrical energy.
[00137] The second turbine 732 and the third turbine 733 cooperatively drive a second generator 754 and form the second pair of turbogenerator 762. The second pair of turbogenerator 762 will produce approximately 25 MW of electrical energy.
[00138] The four-stage hybrid cascade heat exchange cycle of Figure 7 allows the maximum amount of energy to be extracted from the relatively low temperature differential between warm seawater and cold seawater. Furthermore, all heat exchangers can directly support the pairs of turbogenerators that produce electricity using the same component turbines and generators.
[00139] It will be appreciated that multiple multi-stage hybrid cascade heat exchangers and pairs of turbogenerators can be incorporated into a ship or platform design. MULTI-STAGE, OPEN-FLOW HEAT EXCHANGE CABINETS
[00140] OTEC systems by their nature require large volumes of water, for example, a 100 megawatt OTEC power plant may require, for example, up to orders of magnitude more water than required for a steam powered power plant by combustion similarly sized. In an exemplary implementation a 25 MW OTEC power plant may require approximately 3,800 m3/min (1,000,000 gallons per minute) of hot water supply to the evaporators and approximately 3,300 m3/min (875,000 gallons per minute) of cold water for the capacitors. The energy required to pump water together with the small temperature differentials (approximately 1.7°C to 7.2°C (35 to 45°F)) act to decrease efficiency while increasing construction cost.
[00141] Presently available heat exchangers are insufficient to handle the large volumes of water and high efficiencies required for OTEC heat exchange operations. Shell and tube heat exchangers consist of a series of tubes. A set of these tubes contains the working fluid that must be either heated or cooled. The second non-working fluid flows over the tubes being heated or cooled so that it can either provide the heat or absorb the required heat. A set of tubes is called the bundle of tubes and can be composed of different types of tubes: common, longitudinally finned, etc. Shell and tube heat exchangers are typically used for high pressure applications. This is because wrap and tube heat exchangers are robust due to their shape. Shell and tube heat exchangers are not ideal for the low temperature differential, low pressure, high volume nature of OTEC operations. For example, shell and tube heat exchangers, as shown in Figure 8, typically require complicated piping arrangements with high pressure losses and associated piping energy. These types of heat exchangers are difficult to manufacture, install and maintain, specifically in a dynamic environment such as an offshore platform. Shell and tube heat exchangers also require precision mounting specifically for the tube shell connections and the inner supports. Furthermore, shell and tube heat exchangers often have a low heat transfer coefficient and are restricted in the volume of water that can be accommodated.
[00142] Figure 9 presents a plate heat exchanger. Plate heat exchangers can include multiple thin, slightly spaced plates that have very large surface areas and fluid flow passages for heat transfer. This stacked plate arrangement can be more effective, in a given space, than the shell and tube heat exchanger. Advances in gasket and brazing technology have made the plate-type heat exchanger increasingly practical. In HVAC applications for example, large heat exchangers of this type are called plate and frame; when used in open loops, these heat exchangers are typically of the gasket type to allow for periodic disassembly, cleaning, and inspection. Permanently bonded plate heat exchangers, such as the dip brazed and vacuum brazed plate varieties, are often specified for closed loop applications such as refrigeration. Plate heat exchangers also differ in the types of plates that are used, and in the configurations of these plates. Some boards may be stamped with "chevrons" or other patterns, while others may have machined fins and/or grooves.
[00143] Plate heat exchangers, however, have some significant disadvantages in OTEC applications. For example, these types of heat exchangers may require complicated piping arrangements that do not easily accommodate the large volumes of water needed with OTEC systems. Often, gaskets must be precisely mounted and maintained between each pair of plates, and significant bolting is required to maintain the gasket seals. Plate heat exchangers typically require a complete disassembly to inspect and repair even a defective plate. The materials needed for plate heat exchangers can be limited to expensive titanium and/or stainless steel. These types of heat exchangers require relatively equal flow areas between working and non-working fluids. Flow ratios between fluids are typically 1:1. As can be seen from Figure 9, supply and discharge ports are typically provided on the face of the plate, reducing the total heat exchange surface area and complicating the flow path of each of the working and non-working fluids. . Furthermore, plate heat exchangers include a complex internal circuit for nozzles that penetrate all plates.
[00144] In order to overcome the limitations of such conventional heat exchangers, a gasket-free, open flow heat exchanger is provided. In some implementations, the individual boards are aligned horizontally within an enclosure so that a gap exists between each board. A flow path for the working fluid runs through the interior of each plate in a pattern that provides high heat transfer (eg, coil, chevrons, alternating z-patterns, and the like). Working fluid enters each slab through connections on the side of the slabs to reduce obstructions on the face of the slab or impediments to the flow of water through the working fluid. Non-working fluid, such as plain water, flows vertically through the cabinet and fills the gaps between each of the open flow plates. In some implementations, the non-working fluid is in contact with all sides of the open-flow plates or in contact with only the front and rear surfaces of the open-flow plates.
[00145] Figure 10 illustrates a stacked cabinet 520 arrangement of heat exchangers, similar to the arrangement as described in Figure 5, with a detail of a single cabinet 524 having a multi-plate heat exchanger rack 1022. non-work flows vertically through the 524 cabinet and past each of the 1022 boards in the rack. The 1025 arrow indicates the water flow direction. The direction of flow of water can be top to bottom or bottom to top. In some embodiments, the flow direction can be in the natural direction of the water as it is heated or cooled. For example, when condensing a working fluid, water can flow through the cabinet arrangement from the bottom to the top in the natural flow of convection as the water is heated. In another example, when evaporating a working fluid, water can flow from the top to the bottom as the water cools.
[00146] Referring to Figure 10, the open flow heat exchanger cabinet 624 includes a 1030 cabinet face and a 1031 cabinet side. Opposite the 1030 cabinet face is the 1032 cabinet face (not shown) and opposite the 1031 cabinet side is the 1033 cabinet side (not shown). The cabinet faces and sides form a water conduit plenum through which the pure water non-working fluid flows with little or no pressure loss due to the piping.
[00147] In contrast to the gasket heat exchanger described above with respect to Figure 9, the open-flow heat exchanger uses the cabinet to form a flow chamber that contains the non-working fluid (eg, water from the sea) instead of using gaskets between the plates to form the flow chamber containing the non-working fluid. Thus, the 524 open flow heat exchanger cabinet is effectively gasket-free. This important aspect of this system provides significant advantages over other plate and frame heat exchangers that rely on gaskets to isolate the working fluid from the energy supply medium (eg seawater). Corrosion testing of aluminum frame and plate heat exchangers done on NELHA in the 1980s and 1990s had to stop after only approximately six months because there was too much leakage around the gaskets where biological deposits had caused extensive erosion. Applicants have identified gasket problems as a major impediment to utilizing plate and frame design in an OTEC system.
[00148] In addition, the proposed cabinet combined with side mounted input and output ports for the heat exchanger plates avoids the need for the supply and discharge ports typically provided on the face of plate heat exchanger systems (See, for example, Figure 9). This proposal increases the total heat exchange surface area of each plate as well as simplifying the flow path of both working and non-working fluids. Removing the gaskets between the plates also removes significant obstructions that can cause resistance to flow. Gasket-free open flow heat exchanger enclosures can reduce back pressure and associated pumping demand, thus reducing the parasitic load of an OTEC plant and resulting in increased power that can be supplied to the utility company.
[00149] In the case of an OTEC condenser, the 524 cabinet is open at the bottom for the supply of pure cold water, and open at the top to provide unobstructed fluid communication with the 523 cabinet above. The final cabinet in the 521 vertical series is open at the top for the pure water discharge system.
[00150] In the case of an evaporator, cabinet 521 is open at the top for the hot pure water supply and open at the bottom to provide unobstructed fluid communication with the cabinet below 522. The final cabinet 524 in the vertical series is open at the bottom for pure hot water discharge system.
[00151] Within each of the heat exchange cabinets, a plurality of open-flow heat exchanger plates 1022 are disposed in a horizontal alignment to provide a 1025 clearance between each pair of 1022 plates. Each open-flow plate has a front face, a back face, a top face, a bottom face, and right and left sides. Plates 1022 are disposed in horizontal alignment so that the rear face of a first plate faces the front face of a second plate immediately behind the first plate. A working fluid supply and discharge is provided on the sides of each of the plates to prevent impediments to the flow of pure water through gaps 1025 as pure water flows past the front and rear faces of the plurality of plates 1022 within the rack. Each of the plates 1022 includes a working fluid flow passage that is internal to the plate. Open flow plates 1022 are further described in greater detail below.
[00152] In some implementations, each individual 1022 plate has a dedicated working fluid supply and discharge so that the working fluid flows through a single plate. The working fluid supply is directly to one or more of the working fluid supply passages. In other implementations, the working fluid may flow through two or more plates in series before being discharged from the heat exchange cabinet to the remainder of the working fluid system.
[00153] It will be appreciated that each heat exchanger cabinet 524, 523, 522, and 521 has similar components and is vertically aligned so that the horizontally aligned 1022 plates in one cabinet align vertically over the cabinet plates below. The 1025 clearances between the 1022 plates on one cabinet vertically align over the 1025 clearances between the 1022 plates on the cabinet below.
[00154] Referring to Figures 11 and 12, an exemplary implementation of the plate arrangement within heat exchange cabinet 524 includes a first open flow heat exchange plate 1051 having an outer surface that includes at least one front face and rear. The outer surface is in fluid communication with and surrounded by a 1057 non-working fluid such as cold pure water. The first open flow plate also includes an internal passage in fluid communication with a working fluid 1058 flowing through the internal passage. At least one further second open flow heat exchanger plate 1052 is horizontally aligned with the first open flow heat exchanger plate 1051 so that the front outer surface of second plate 1052 faces the rear outer surface of first plate 1051. Like the first plate, at least one second plate 1052 includes an outer surface in fluid communication with and surrounded by non-working fluid 1057, and an inner passage in fluid communication with a working fluid 1058 flowing through the internal passage. . The first open flow heat exchanger plate 1051 is separated from the second heat exchanger plate 1052 by a gap 1053. Non-working fluid 1057 flows through the gap.
[00155] Figure 13 presents a side view of an exemplary open flow heat exchanger cabinet 524 that includes a first open flow heat exchanger plate 1051, a second heat exchanger plate 1052, and gaps 1053 that separate each plate 1051 and 1052. Working fluid 1058 flows through internal working fluid flow passages 1055.
[00156] As described above, in some implementations, a single heat exchange cabinet can be dedicated to a single stage of a hybrid cascade OTEC cycle. In some implementations, four heat exchange cabinets are vertically aligned, as shown and described in Figure 5. In other implementations, cabinets that have working fluid supply and discharge lines connected to the sides of each plate can be used. This prevents the working fluid conduits from being over the face of the plates and preventing the flow of both working fluid and non-working fluid.
[00157] For example, a gasket-free multistage heat exchange system may include a first stage heat exchange rack comprising one or more open flow plates in fluid communication with a first flowing working fluid through an internal passage in each of the one or more open flow plates. Working fluid can be supplied and discharged from each plate through supply and discharge lines dedicated to each individual plate. A second-stage heat exchanger rack vertically aligned with the first heat exchanger rack is also included. The second stage heat exchange rack comprises one or more open flow plates in fluid communication with a second working fluid flowing through an internal passage in each of the one or more open flow plates. Again, the second working fluid is supplied and discharged to and from each individual plate via lines dedicated to each individual plate. A non-working fluid, such as plain water, first flows through the first stage heat exchange rack and around each of the one or more open flow plates allowing a heat exchange with the first working fluid. The non-working fluid then passes through the second heat exchange rack and around each of the open flow plates allowing heat exchange with the second working fluid.
[00158] The first stage rack includes a plurality of open flow plates in horizontal alignment that have a gap between each plate. The second stage rack also includes a plurality of open flow plates in horizontal alignment which have a gap between each plate within the second stage rack. The plurality of open flow plates and gaps in the second stage rack are vertically aligned with the plurality of open flow plates and gaps in the first stage rack. This reduces pressure losses in the non-working fluid flow through the first and second stage racks. Pressure losses in the non-working fluid are also reduced by having the non-working fluid discharge directly from one cabinet to the next thereby eliminating the need for extensive and massive piping systems. In some embodiments, the walls of the cabinets containing the first and second stage racks of heat exchange plates form the conduit through which the non-working fluid flows.
[00159] Due to the open-flow arrangement of the plates in each rack of each stage of an exemplary four-stage OTEC system, the non-working fluid to working fluid flow ratio is increased from the typical 1:1 of the most conventional plate heat exchanger systems. In some implementations, the non-working fluid flow ratio is greater than 1:1, (for example, greater than 2:1, greater than 10:1, greater than 20:1, greater than 30:1, greater than 40:1, greater than 50:1, greater than 60:1, greater than 70:1, greater than 80:1, greater than 90:1 or greater than 100 :1).
[00160] When a multistage arrangement of heat exchange cabinets is used as a condenser, non-working fluid (eg cold seawater) generally enters the first stage cabinet at a lower temperature than that when non-working fluid enters the second-stage cabinet, and the non-working fluid then enters the second-stage cabinet at a lower temperature than when non-working fluid entered the third-stage cabinet; and non-working fluid enters the third-stage cabinet at a generally lower temperature than when it enters the fourth-stage cabinet.
[00161] When a multi-stage arrangement of heat exchange cabinets is used as an evaporator, non-working fluid (eg, hot sea water) generally enters the first-stage cabinet at a higher temperature than the temperature. that when non-working fluid enters the second-stage cabinet, and the non-working fluid then enters the second-stage cabinet at a higher temperature than when non-working fluid enters the third-stage cabinet; and non-working fluid enters the third-stage cabinet at a generally higher temperature than when it enters the fourth-stage cabinet.
[00162] When a multistage arrangement of heat exchange cabinets is used as a condenser, the working fluid (eg ammonia) generally exits the first stage cabinet at a lower temperature than when the working fluid. work leaves the second-stage cabinet, and the working fluid leaves the second-stage cabinet at a lower temperature than when the working fluid leaves the third-stage cabinet; and the working fluid leaves the third-stage cabinet at a generally lower temperature than when it leaves the fourth-stage cabinet.
[00163] When a multistage arrangement of heat exchange cabinets is used as an evaporator, the working fluid (eg ammonia) generally exits the first stage cabinet at a higher temperature than when the working fluid. work leaves the second-stage cabinet, and the working fluid leaves the second-stage cabinet at a generally lower temperature than when the working fluid leaves the third-stage cabinet; and the working fluid leaves the third-stage cabinet at a temperature generally higher than when it leaves the fourth-stage cabinet.
[00164] An exemplary thermal equilibrium implementation of a four-stage OTEC cycle is described here and generally illustrates these concepts.
[00165] In some implementations, a four-stage, gasket-free heat exchange system includes a first-stage heat exchange rack that has one or more open flow plates, each plate includes an outer surface that has at least one front and rear face surrounded by a non-working fluid. Each plate also includes an internal passage in fluid communication with the first working fluid flowing through the internal passage. Working fluid is supplied and discharged from each plate by supply and discharge lines dedicated to each plate.
[00166] The four-stage heat exchange system also includes a second-stage heat exchange rack vertically aligned with the first heat exchange rack, the second-stage heat exchange rack includes one or more exchange plates of open-flow heat substantially similar to those of the first stage and vertically aligned with the first stage plates.
[00167] A third stage heat exchange rack substantially similar to the first and second stage racks is also included and is vertically aligned with the second stage heat exchange rack. A fourth-stage heat exchanger frame, substantially similar to the first, second, and third-stage racks, is included and vertically aligned with the third-stage heat exchanger rack.
[00168] In operation, the non-working fluid flows through the first-stage heat exchange rack and surrounds each open flow plate therein for thermal interaction with the first working fluid that flows within the internal flow passages of each board. The non-working fluid then flows through the second-stage heat exchange rack for thermal interaction with the second working fluid. The non-working fluid then flows through the second stage heat exchange rack for thermal interaction with the second working fluid before flowing through the third stage heat exchange rack for thermal interaction with the third working fluid. The non-working fluid flows through the third stage heat exchange rack for thermal interaction with the third working fluid before flowing through the fourth stage heat exchange rack for thermal interaction with the fourth working fluid. The non-working fluid is then discharged from the heat exchange system. FREE FLOW HEAT EXCHANGE PLATES:
[00169] The low temperature differential of OTEC operations (typically between 1.5°C and 47.2°C (35°F and 85°F)) requires a heat exchange plate design free of flow obstructions non-working fluid and working fluid. Furthermore, the plate must provide sufficient surface area to support the low temperature energy conversion of the working fluid.
[00170] Conventional power generation systems typically utilize a combustion process with a high temperature rise system such as a steam power cycle. As environmental problems and unbalanced fossil fuel supply problems become more prevalent, Low Temperature Rise Power Conversion (LTLEC) systems, such as the OTEC system implementations described herein, and which utilize sources Renewable energy such as solar thermal and ocean thermal will become more important while conventional steam energy cycles use off-gas from the combustion process and are usually at very high temperatures, LTLEC cycles use low energy sources. temperature ranging from 30 to 100°C. Therefore, the temperature difference between the heat source and the heat sink of the LTLEC cycle is much smaller than that of the steam power cycle.
[00171] Figure 14 shows the process of a conventional high temperature steam energy cycle in a pressure - enthalpy (P-h) diagram. The thermal efficiency of the steam power cycle is in the range of 30 to 35%.
[00172] In contrast, Figure 15 shows the P-h diagram of an LTLEC cycle, such as the one used in OTEC operations. Thermal efficiency for an LTLEC cycle is 2 to 10%. This is nearly one-third to one-tenth of that of a conventional high-temperature steam power cycle. Thus, an LTLEC cycle requires much larger size heat exchangers than conventional energy cycles.
[00173] The heat exchanger plates described below provide a high heat transfer performance and also a low pressure drop on the fluid sides of the heat source and heat sink to limit the pumping energy requirements which affect the system efficiency. These heat exchanger plates designed for OTEC and other LTLEC cycles, may include the following features:
[00174] A working fluid flow path that has a mini-channel design. This can be provided on a bearing-bonded aluminum heat exchanger plate and provides a large area of active heat transfer between the working and non-working fluids;
[00175] A clearance provided between the plates and/or displacement of the plates connected by bearing between even numbered and odd numbered plates so as to significantly reduce the pressure drop in the heat source and heat sink non-working fluids. In this way, a relatively wide fluid flow area to the heat source and heat sink fluid sides can be provided, while maintaining a relatively narrow fluid flow area for the power cycle work flow;
[00176] A setting of progressively changing the numbers of channels per pass within the working fluid flow passages can reduce the phase change working fluid pressure drop along the flow. The number of channels on the plate can be designed according to the working fluid, operating conditions, and heat exchanger geometry;
[00177] Working fluid flow passages or corrugated channel configuration can improve heat transfer performance;
[00178] Within working fluid flow channels and between parallel channels, both ends of the inner walls of the flow channel channel can be curved to smoothly direct fluid to subsequent channels when the flow direction is reversed, and distances non-uniforms from the ends of the inner walls of the channel to the side wall may be used between the parallel channels.
[00179] The above characteristics can reduce the pumping energy needed in the system, and improve the heat transfer performance.
[00180] Referring again to Figure 11, mini-channel bearing adhered heat exchange plates 1051 and 1052 are shown in perspective view. A cross-flow between the working fluid and the non-working fluid is provided. When used as an evaporator, the 1057 non-working fluid (eg seawater) enters the top of the plates and exits the bottom of the plates. The 1058 working fluid (eg ammonia) enters the underside of the plates in a liquid state and evaporates and finally becomes a vapor phase absorbing the thermal energy of the higher temperature non-working fluid. The 1059 steam generated exits the plates from the upper side.
[00181] Figure 13 shows the fluid flows in a side view. The working fluid flow channels 1055 have a relatively wide width w and a relatively low height h so as to increase the active heat transfer area between the two fluids while reducing the volume of the entire heat exchange plate. The width w of the channels can vary between approximately 10 and approximately 15 mm (eg, more than 11 mm, more than 12 mm, more than 13 mm, less than 14 mm, less than 13 mm, and/ or less than 12 mm). The height h of the channels can vary between approximately 1 and approximately 3 mm (for example, more than 1.25 mm, more than 1.5 mm, more than 1.75 mm, more than 2 mm, less than than 2.75 mm, less than 2.5 mm, less than 2.25 mm and/or less than 2 mm). The spacing between the channels can be between approximately 4 and approximately 8 mm (eg more than 4.5 mm, more than 5 mm, more than 5.5 mm, less than 7.5 mm, less than than 7 mm, and/or less than 6.5 mm). The bearing-connected plates are arranged in a distribution of even plates 1051 and odd plates 1052 with working fluid flow passages 1055 displaced so as to provide a smooth flow path for the non-working fluid 1057 and provide an area of non-working fluid flow wider than the working fluid flow area in the 1055 working fluid channels. This arrangement reduces the pressure drop on the heat source fluid and heat sink fluid sides.
[00182] Figure 16 illustrates a wavy or undulating working fluid flow path designed to improve plate heat transfer performance.
[00183] Figure 17 illustrates an embodiment of a heat exchange plate with two inlets that receive the 1058 working fluid and two outlets that discharge the heated or cooled 1059 fluid. The internal flow paths within each open flow plate are arranged in an alternating serpentine pattern so that the flow of working fluid is substantially perpendicular or transverse to the flow direction of the non-working flow. Furthermore, the progression of the working fluid through the coil pattern can generally be parallel to the non-working fluid flow or opposite the non-working fluid flow direction. In some embodiments, flow distribution between channels can be improved by using guide vanes. Figure 18 illustrates an embodiment of a heat exchange plate in which an area 1710 of variable space in the flow path 1701 is provided to even out the flow distribution between the parallel channels 1705. Furthermore, both ends 1715 of the inner walls of channel 1712 are curved to smoothly direct fluid to subsequent channels when the direction of flow is reversed, and non-uniform distances from the ends of inner walls of channel 1712 to sidewall 1702 can be used between the parallel channels. These guide vanes and variable flow path dimensions can be implemented in heat exchange plates such as, for example, the heat exchange plates shown in Figures 17, 19A and B, and 20A and B.
[00184] In some embodiments, it has been found that the working fluid changes its phase from liquid to vapor along the flow path, and consequently the working fluid pressure drop will increase significantly if the same flow passage area is used across the entire heat exchanger plate. In order to reduce the fluid pressure drop increase along the flow associated with its change in steam quality, the number of parallel flow passages per pass can be increased along the working fluid flow path.
[00185] Figures 19A and 19B illustrate a pair of heat exchanger plates 1905, 1910 that implement this proposal in an evaporator. The 1905 heat exchange plate in Figure 19A has two 1911 inputs which each feed into two 1912 mini-channels. The 1912 mini-channels extend across the plate in a serpentine mode that is similar to the heat exchange plate channels shown in Figure 17. However, on the heat exchange plate shown in Figure 19A, the flow from two mini-channels feeds into three mini-channels at a first transition point 1914. The flow from the three mini-channels feeds into four mini-channels at a second transition point 1916. As the heat exchange plate includes two separate, complementary flow paths, these expansions result in eight mini-channels which discharge through four outlets 1918.
[00186] The four 1918 outputs of the 1905 heat exchange board are hydraulically connected to the four 1920's inputs of the 1910 heat exchange board shown in Figure 19B. The four mini-channels flow feeds into five mini-channels at a third transition point 1922. The five mini-channels flow feeds into six mini-channels at a fourth transition point 1924. As this heat exchange plate also includes two paths of separate, complementary flow, these expansions result in twelve mini-channels which discharge through six 1926 outlets. Connecting the 1905, 1910 heat exchanger plates in series provides the equivalent of a single long heat exchanger plate but is easier to manufacture .
Plates 1905, 1910 have a length L between approximately 1200 mm and 1800 mm (for example, more than 1300 mm, more than 1400 mm, more than 1450 mm, more than 1475 mm, less than 1700mm, less than 1600mm, less than approximately 1550mm and/or less than 1525mm). The width W of the plates can vary between approximately 250 and approximately 450 mm (for example, more than 275 mm, more than 300 mm, more than 325 mm, more than 350 mm, less than 425 mm, less than than 400 mm, less than 375 mm and/or less than 350 mm).
[00188] In some embodiments, plates of different sizes and different numbers of inputs and outputs are used to provide the heat exchange area and the desired expansion/contraction characteristics. For example, the 1905, 1910 pair plates are sized in part based on current supplier limitations. In some embodiments, a single plate will replace the 1905, 1910 pair plates thus removing the need for the 1920 outputs and 1918 inlets that are used to transfer the working fluid from the 1905 plate to the 1910 plate. L between approximately 2700mm and 3300mm (for example, more than 2800mm, more than 2900mm, more than 2950mm, more than 2975mm, less than 3200mm, less than 3100mm, less than than approximately 3050 mm and/or less than 3025 mm). Larger boards can have a width W between approximately 550 mm and approximately 850 mm (eg more than 575 mm, more than 600 mm, more than 625 mm, more than 650 mm, less than 825 mm, less than 800 mm, less than 775 mm and/or less than 750 mm). In some embodiments, a single larger 1918 inlet replaces the 2 inlets of the 1905 board and feeds the working fluid to all four 1912 mini-channels. As the 1918 inlets and 1920 outlet can be sources of pressure loss that decrease the efficiency of the platens. heat exchange, reducing the number of 1918 inlets and 1920 outlets will reduce the total pumping requirement, and thus the parasitic load, of a given OTEC system.
[00189] Flow through heat exchange plates 1905, 1910 is described for an evaporator. Heat exchange plates 1905, 1910 could also be used in a condenser. However, the fluid flow through a condenser would be the inverse of the flow described for the evaporator.
[00190] Some heat exchanger plates include mini meandering channels which can increase the residence time for the working fluid (eg ammonia) to pass through the heat exchanger plates as well as providing additional surface area for heat transfer . Figures 20A and 20B illustrate a pair of heat exchanger plates 2005, 2010 that are generally similar to the heat exchanger plates 1905, 1910 shown in Figures 19A and 19B. However, the mini-channels of the heat exchanger plates 2005, 2010 include a sinuous pattern. Based on laboratory testing and numerical modeling, 2005, 2010 heat exchanger plates that include a sinuous sinusoidal pattern are estimated to provide the same heat exchange as 1905, 1910 heat exchanger plates with a reduction of approximately 10% in the number of plates.
[00191] Both the 1905, 1910 and the 2005, 2010 plates include channels arranged in relatively sinusoidal curve patterns. These patterns seem to provide several advantages. The relatively sinusoidal curve patterns cause the water flow over the plates to take a more turbulent and longer path between the plates allowing the working fluid side (eg ammonia) to theoretically extract more thermal energy from the water. Furthermore, the sinusoidal flow patterns are configured so that the plates can be turned in opposite directions or staggered (eg alternating left and right) so that the input and output connections do not interfere with each other.
[00192] Heat exchange plates that incorporate the various features discussed above can be manufactured using a bearing bonding process. Rolling bonding is a manufacturing process whereby two metal plates are fused together by heat and pressure then expanded with high pressure air so that flow channels are created between the two panels. A carbon-based material is printed on the bottom panel in the desired flow pattern. A second panel is deposited on top of the first panel and the two panels are then rolled through a hot rolling press where the two panels are fused everywhere except where carbon material is present. At least one channel is printed to the edge where a vibrating mandrel is inserted between the two plates creating a port into which pressurized air is injected. Pressurized air causes the metal to deform and expand so that channels are created where the two plates are prevented from fusing together. There are two ways the roll bonding can be done: continuous, in which the metal is run continuously through hot rollers presses on the sheet metal rollers; or discontinuous in which pre-cut panels are individually processed.
[00193] In a prototype two metal sheets, each approximately 1.05-1.2 mm thick, 1545 mm long, and 350 mm wide, were joined by bearing together to form the plates. Channels, in the patterns shown in Figures 19A and 19B, were formed between the metal sheets joined by blow molding. The channels were formed with a width w between 12-13.5 mm and a height h of approximately 2 mm. The plates exhibit good heat exchange properties using ammonia as the working fluid and water as the non-working fluid. ADDITIONAL OTEC FEATURES:
[00194] In an exemplary implementation of an OTEC power plant, an offshore OTEC spar platform includes four separate power modules, each generating approximately 25 MWe Net at nominal design condition. Each power module comprises four separate power cycles or cascading thermodynamic stages that operate at different pressure and temperature levels and capture heat from the seawater system in four different stages. The four different stages operate in series. The approximate pressure and temperature levels of the four stages at the nominal design conditions (Full Load - Summer Conditions) are:

[00195] The working fluid is boiled in multiple evaporators capturing heat from warm sea water (WSW). The saturated value is separated in a steam separator and led to an ammonia turbine by a seamless schedule STD carbon steel tube. The condensed liquid inside the condenser is pumped back to the evaporator by two constant speed feed pumps driven by a 100% electric motor. Cycles 1 and 4 turbines drive a common electrical generator. Similarly, cycles 1 and 3 turbines drive another common electrical generator. In some modes, there are two generators in each plant module and a total of 8 in the 100 MWe plant. Feed to the evaporators is controlled by feed control valves to maintain the level inside the vapor separator. Condenser level is controlled by cycle fluid composition control valves. Minimum feed pump flow is maintained by recirculation lines conducted to the condenser through flow meter regulated control valves in the feed line.
[00196] In operation, the four (4) power cycles of the modules operate independently. Any one of the cycles can be switched off without jeopardizing the operation of the other cycles if necessary, for example in case of a failure or for maintenance. Such partial shutdowns will reduce the net power generation of the total power module.
[00197] The system requires large volumes of seawater and includes separate systems for handling cold and hot seawater, each with its own pumping equipment, water ducts, piping, valves, heat exchangers, etc. Sea water is more corrosive than fresh water and all materials that come into contact with it need to be carefully selected with this in mind. The construction materials for the main components of the seawater system will be:

[00198] Unless controlled by appropriate means, biological growths within seawater systems can cause a significant loss of plant performance and can cause contamination of heat transfer surfaces that lead to decreased plant output. This in-growth can also increase resistance to water flows causing higher pumping power requirements, lower system flows, etc. and even complete blockages of flow paths in more severe cases.
[00199] The Cold Sea Water ("CSW") system aspirated from the deep ocean should have very little or no biocontamination problem. Water at these depths does not receive much sunlight and is lacking in oxygen, so there are fewer living organisms in it. Some types of anaerobic bacteria, however, are able to grow this under certain conditions. A shock chlorination will be used to combat biofouling.
[00200] The Near Surface Warm Sea Water ("WSW") system will need to be produced from biofouling. It has been found that contamination rates are much lower in tropical open ocean waters suitable for OTEC operations than in coastal waters. When necessary, chemical agents can be used to control biofouling in OTEC systems at very low doses that will be environmentally acceptable. Dosing small amounts of chlorine has been shown to be very effective in combating biocontamination in seawater. Chlorine dosages at the rate of approximately 70 ppb per hour per day are very effective in preventing the growth of marine organisms. This dosing rate is only 1/20th the environmentally safe level stipulated by the EPA. Other types of treatment (thermal shock, shock chlorination, other biocides, etc.) may be used from time to time between low dose treatment regimens to get rid of chlorine resistant organisms.
[00201] The chlorine needed to dose the seawater flows is generated on board the plant ship by seawater electrolysis. Electrochlorination plants of this type are commercially available and have been used successfully to produce a hypochlorite solution to be used for dosing. The electrochlorination plant can operate continuously to fill storage tanks and the contents of these tanks are used for the periodic dosing described above.
[00202] Seawater conduits are designed to avoid any dead pockets where sediment may deposit or organisms may settle to start a colony. Washing arrangements are provided with low points in the water ducts to flush out deposits that may collect there. The high points of the water ducts and chambers are vented to allow trapped gases to escape.
[00203] The Cold Sea Water (CSW) system consists of a common deep water inlet to the power plant, and water pumping/distribution systems, the condensers with their associated water piping, and discharge ducts to return the water back to the sea. The cold water inlet pipe extends downward to a depth of more than 823 m (2700 ft), (eg between 823 m and 1280 m (2700 ft and 4200 ft)) where the seawater temperature is approximately 4.4°C (40°F) constant. The tube inlet is screened to prevent large organisms from being sucked into the tube. After entering the pipe, the cold water flows upwards towards the sea surface and is supplied to a cold well chamber near the bottom of the ship or spar.
[00204] The supply pumps, distribution ducts, condensers, etc. of CSW are located at the lowest level of the plant. The pumps take suction from the cross duct and send cold water to the distribution duct system. 4 x 25% CSW suction pumps are provided for each module. Each pump has an independent circuit with inlet valves so they can be isolated and opened for inspection, maintenance, etc. when required. Pumps are driven by high-efficiency electric motors.
[00205] Cold sea water flows through the series cycle condensers and then the CSW effluent is discharged back to the sea. CSW flows through the condenser heat exchangers of the four power plant cycles in series in the required order. Condenser installations are arranged to allow them to be isolated and opened for cleaning and maintenance when necessary.
[00206] The WSW system comprises submerged inlet grids located below the sea surface, an inlet plenum to conduct incoming water to pumps, water pumps, biocide dosing system to control contamination of transfer surfaces heat, water filtration system to prevent blockages by suspended materials, evaporators with their associated water piping, and discharge ducts to return water back to the sea.
[00207] Inlet grates are provided on the outer wall of the plant modules to draw hot water from near the sea surface. Face velocity on inlet grids is kept to less than 0.15 m/s (0.5 ft/s) to limit drag of marine organisms. These grates also keep out large floating debris and their free openings are based on the maximum size of solids that can safely pass through the pumps and heat exchangers. After passing through these grates, water enters the inlet plenum located behind the grates and is routed to the suctions of the WSW supply pumps.
[00208] WSW pumps are located in two groups on opposite sides of the pump floor. Half of the pumps are located on each side with separate inlet plenum suction connections for each group. This arrangement limits the maximum flow rate through any portion of the inlet plenum to approximately 1/16 of the total flow and thus reduces friction losses in the inlet system. Each of the pumps is provided with valves on the inlet side so that these can be isolated and opened for inspection, maintenance, etc. when required. Pumps are driven by high-efficiency electric motors with variable frequency drives to match pump output to load.
[00209] It is necessary to control the biocontamination of the WSW system and specifically its heat transfer surfaces, and suitable biocides will be dosed into the pump suction for this.
[00210] The hot water flow may need to be filtered to remove the larger suspended particles that can block the narrow passages in the heat exchangers. Large automatic filters or 'Debris Filters' can be used for this if required. Suspended materials can be retained on screens and then removed by backwashing. Backwash effluent carrying the suspended solids will be routed to the plant's discharge stream to be returned to the ocean. The exact requirements for this will be decided during further development of the project after more data regarding seawater quality has been collected.
[00211] The filtered warm seawater (WSW) is distributed to the evaporator heat exchangers. WSW flows through the evaporators of the four plant cycles in series in the required order. The WSW effluent from the last cycle is discharged to a depth of approximately 53.3 m (175 ft) or deeper below the sea surface. It then slowly sinks to a depth where the temperature (and therefore the density of the seawater will coincide with that of the effluent). ADDITIONAL ASPECTS:
[00212] The cold water inlet tube is a stave, segmented, pultruded fiberglass tube. Each stave segment can be 12.1 - 15.2 m (40 - 50 ft) long. Stave segments can be joined by staggered staves to create an interlock seam. Tube staves can be extruded into panels up to 1.32 meters (52 inches) wide and at least 15.2 m (50 feet) long and can incorporate e-glass or s-glass with polyurethane, polyester, or vinylester resin. In some respects the stave segment may be concrete. The staves can be of solid construction. The staves can have a core or bee hive construction. The staves will be designed to interlock with each other and at the ends the staves will be staggered thereby eliminating the use of flanges between the cold water pipe sections. In some arrangements, the staves may be 12.1 m (40 ft) long and staggered by 1.5 m and 3.0 m (5 ft and 10 ft) where the pipe sections are joined. The staves and pipe section can be bonded together, for example using polyurethane or polyester adhesive. 3-M and other companies make suitable stickers. If a sandwich construction is used, a polycarbonate foam or syntactic foam can be used as the core material. Spider web cracks should be avoided and the use of polyurethane helps to provide a reliable design.
[00213] In some modalities, the predicted CWP is continuous, that is, it does not have flanges between the sections.
[00214] The CWP can be connected to the spar through a spherical support joint. The cold water pipe can also be connected to the spar using a combination of lifting cables and a piston or dead bolt system.
[00215] One of the significant advantages of using the spar as the platform is that doing so results in relatively small rotations between the spar itself and the CWP even in the most severe storm conditions in 100 years. Furthermore, the vertical and lateral forces between the spar and the CWP are such that the downward force between the spherical ball and its seat keeps the bearing surfaces in contact at all times. This support, which also acts as a water seal, does not come out of contact with its corresponding spherical seat. Thus, there is no need to install a mechanism to hold the CWP in place vertically. This helps to simplify the ball bearing design and also limits pressure losses that would otherwise be caused by any additional CWP pipe restraint hardware or structure. The lateral forces transferred through the spherical support are also low enough that these can be adequately accommodated without the need for vertical restraint of the CWP.
[00216] Although the embodiments herein have described a multistage heat exchanger on a floating ship or offshore platform, it will be appreciated that other embodiments are within the scope of the invention. For example, the multi-stage heat exchanger and integrated flow passages can be incorporated into land-based installations including land-based OTEC installations. Furthermore, hot water can be hot fresh water, geothermally heated water, or industrial discharge water (eg, cooling water discharged from a nuclear power plant or other industrial plant). Cold water can be cold fresh water. The OTEC system and components described herein can be used for the production of electrical energy or in other fields of use including: seawater desalination; water purification; deep water recovery; aquaculture; the production of biomass or biofuels; and still other industries.
[00217] Other modalities are within the scope of the following claims.

权利要求:
Claims (17)
[0001]
1. Multi-stage heat exchange system, the multi-stage heat exchange system being characterized by the fact that it comprises: a first-stage heat exchange chassis comprising one or more open flow plates (1022 , 1051, 1052, 1905, 1910, 2005, 2010) in fluid communication with a first working fluid (1058) which flows through an internal passage in each of the one or more open flow plates; a second stage heat exchange chassis vertically aligned with the first stage heat exchange chassis, the second stage heat exchange chassis comprising one or more open flow plates (1022, 1051, 1052, 1905, 1910, 2005, 2010) in fluid communication with a second working fluid that flows through an internal passage in each of the one or more open flow plates; wherein a non-working fluid flows first through the first-stage heat exchange chassis and around each of the one or more open flow plates therein for a heat exchange with the first working fluid and secondly through the second stage heat exchanger chassis and around each of the open flow plates for heat exchange with the second working fluid.
[0002]
2. Heat exchange system according to claim 1, characterized in that the first working fluid is heated to a steam and the second working fluid is heated to a steam that has a lower temperature than the first vaporous working fluid particularly, wherein the first working fluid is heated to a temperature between 20.6°C and 21.7°C (69°F and 71°F), more particularly wherein the working fluid of second stage is heated to a temperature below the first stage working fluid temperature and between 20.0°C to 21.1°C (68°F and 70°F).
[0003]
3. Heat exchange system according to claim 1, characterized in that the first working fluid is cooled to a condensed liquid in the first stage heat exchange chassis and the second working fluid is cooled to a liquid condensed in the second-stage heat exchange chassis, the condensed second-stage working fluid having a higher temperature than the condensed first-stage working fluid, particularly where the first working fluid is cooled to a temperature between 5.6°C and 7.8°C (42°F and 46°F), more particularly, where the second-stage working fluid is cooled to a higher temperature than the first-stage working fluid and to a temperature between 7.2°C to 8.3°C (45°F and 47°F).
[0004]
4. Heat exchange system according to claim 2, characterized in that the non-working fluid enters the first stage heat exchange chassis at a first temperature and the non-working fluid enters the chassis stage heat exchanger at a lower second temperature, or where non-working fluid enters the first stage heat exchanger chassis at a temperature between 3.3°C and 6.7°C (38 °F and 44°F) and exits the second stage heat exchanger chassis at a temperature between 5.6°C and 8.9°C (42°F and 48°F).
[0005]
5. Heat exchange system according to claim 1, characterized in that the flow ratio of the non-working fluid to the working fluid is greater than 2:1, particularly where the ratio of flow from non-working fluid to working fluid is between 20:1 and 100:1.
[0006]
6. Heat exchange system according to claim 1, characterized in that the first and second stage heat exchange chassis form first and second stage cabinets (521, 522, 523, 524) and in which non-working fluid flows from the first cabinet to the second cabinet without pressure loss due to piping.
[0007]
7. A heat exchange system according to claim 1, characterized in that the open flow plates reduce pressure losses in the working fluid flow due to the absence of nozzles and/or non-fluid penetrations. work across the board.
[0008]
8. A heat exchange system according to claim 1, characterized in that the working fluids flow path comprises a first flow direction through the non-working fluid flow path and a second flow direction of flow path opposite the first flow path direction.
[0009]
9. Heat exchange system according to claim 1, characterized in that the first and second working fluids are working fluids in an OTEC system (310), particularly in which the first and second fluids are ammonia.
[0010]
10. Heat exchange system according to claim 1, characterized in that the non-working fluid is pure water.
[0011]
11. Heat exchange system according to claim 1, characterized in that the open flow plates further comprise front, rear, top and bottom external surfaces and the non-working fluid is in contact with all surfaces external.
[0012]
12. Heat exchange system according to claim 1, characterized in that: the first stage chassis further comprises a plurality of open flow plates in horizontal alignment that have a clearance (1053) between each plate inside the first-stage chassis; the second stage chassis further comprises a plurality of open flow plates in horizontal alignment having a clearance (1053) between each plate within the second stage chassis; and the plurality of open flow plates and clearances therebetween in the second stage chassis are vertically aligned with the plurality of open flow plates and clearances therebetween in the first stage chassis to reduce pressure losses in the working fluid flow through the first and second stage chassis, particularly, further comprising a rail for suspending each of the plurality of open-flow plates and a plurality of slots for maintaining the horizontal position of each of the plurality of open-flow plates.
[0013]
13. Multi-stage heat exchange system, characterized in that it comprises: a first-stage heat exchange chassis comprising one or more open flow plates, each plate comprising an outer surface surrounded by a non-fluid. working and an internal passage in fluid communication with a first working fluid flowing through the internal passage; a second-stage heat exchange chassis vertically aligned with the first-stage heat exchange chassis, the second-stage heat exchange chassis comprising one or more open flow plates comprising an outer surface surrounded by the non-fluid. working and an internal passage in fluid communication with a second working fluid flowing through the internal passage; a third-stage heat exchange chassis vertically aligned with the second-stage heat exchange chassis, the third-stage heat exchange chassis comprising one or more open flow plates comprising an outer surface surrounded by the non-fluid. work and an internal passage in fluid communication with a third working fluid flowing through the internal passage; a fourth-stage heat exchange chassis vertically aligned with the third-stage heat exchange chassis, the fourth-stage heat exchange chassis comprising one or more open flow plates comprising an outer surface surrounded by the non-fluid. working and an internal passage in fluid communication with a fourth working fluid flowing through the internal passage; wherein the non-working fluid flows through the first-stage heat exchange chassis for a thermal interaction with the first working fluid before flowing through the second-stage heat exchange chassis for a thermal interaction with the second fluid working fluid, the non-working fluid flows through the second-stage heat exchange chassis for a thermal interaction with the second working fluid before flowing through the third-stage heat exchange chassis for a thermal interaction with the third working fluid, and the non-working fluid flows through the third-stage heat exchange chassis for a thermal interaction with the third working fluid before flowing through the fourth-stage heat exchange chassis for a thermal interaction with the fourth working fluid.
[0014]
A heat exchange system according to claim 13, characterized in that: the first working fluid is heated to a steam; the second working fluid is heated to a vapor having a lower temperature than the first vaporous working fluid; the third working fluid is heated to a vapor that has a lower temperature than the second working fluid; and the fourth working fluid is heated to a steam having a lower temperature than the third steam fluid, particularly wherein: the first working fluid is heated to a temperature between 20.6°C and 21.7° C (69°F and 71°F); the second working fluid is heated to a lower temperature than the first working fluid and between 20.0°C to 21.1°C (68°F and 70°F); the third working fluid is heated to a temperature below the second working fluid and between 18.9°C to 20.6°C (66°F and 69°F); and the fourth working fluid is heated to a temperature below the third working fluid and between 17.8°C to 19.4°C (64°F and 67°F).
[0015]
15. Heat exchange system according to claim 13, characterized in that: the first working fluid is cooled to a condensed liquid in the first stage heat exchange chassis; the second working fluid is cooled to a condensed liquid in the second-stage heat exchange chassis and has a higher temperature than the first condensed working fluid; the third working fluid is cooled to a condensed liquid in the third-stage heat exchange chassis and has a higher temperature than the second condensed working fluid; and the fourth working fluid is condensed to a liquid in the fourth stage heat exchange chassis and has a higher temperature than the third working fluid condensed, particularly where: the first working fluid is condensed at a temperature between 5.6°C and 7.8°C (42°F and 46°F); the second working fluid is condensed at a higher temperature than the first working fluid and between 7.2°C and 8.3°C (45°F and 47°F); the third working fluid is condensed at a higher temperature than the second working fluid and between 7.8°C and 9.4°C (46°F and 49°F); and the fourth working fluid is condensed at a higher temperature than the third working fluid and between 9.4°C and 11.1°C (49°F and 52°F).
[0016]
16. A heat exchange system according to claim 13, characterized in that the non-working fluid flows from the first-stage heat exchange chassis to the second-stage heat exchange chassis, of the second-stage heat exchange to the third-stage heat exchange chassis, and from the third-stage heat exchange chassis to the fourth-stage heat exchange chassis without pressure losses due to piping.
[0017]
17. A heat exchange system according to claim 13, characterized in that: the first stage chassis further comprises a plurality of open flow plates in horizontal alignment that have a gap between each plate within the first chassis Internship; the second stage chassis further comprises a plurality of open flow plates in horizontal alignment which have a clearance between each plate within the second stage chassis; the third stage chassis further comprises a plurality of open flow plates in horizontal alignment which have a clearance between each plate within the third stage chassis; the fourth stage chassis further comprises a plurality of open flow plates in horizontal alignment which have a clearance between each plate within the fourth stage chassis; and the plurality of open flow plates and clearances within each chassis are vertically aligned with the open flow plates and clearances in each of the other chassis of the other stages so as to reduce pressure losses in the flow of working fluid through of the chassis of the first and second stages.

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US20130042612A1|2013-02-21|

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WO2013025797A2|2013-02-21|

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法律状态:
2018-12-11| B06F| Objections, documents and/or translations needed after an examination request according [chapter 6.6 patent gazette]|

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2020-01-21| B06U| Preliminary requirement: requests with searches performed by other patent offices: procedure suspended [chapter 6.21 patent gazette]|

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2021-06-01| B09A| Decision: intention to grant [chapter 9.1 patent gazette]|

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2021-08-10| B16A| Patent or certificate of addition of invention granted [chapter 16.1 patent gazette]|Free format text: PRAZO DE VALIDADE: 20 (VINTE) ANOS CONTADOS A PARTIR DE 15/08/2012, OBSERVADAS AS CONDICOES LEGAIS. |

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