• 专利附录
  • 专利说明
  • 权利要求
  • 类似技术
  • 同族专利
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    • 专利摘要:
    The invention relates to an exhaust air heat recovery apparatus and method. The apparatus comprises a first inlet channel (13) for exhaust indoor air, an outlet channel (15) for discharge air, a heat exchange unit (11) comprising an air intake connected to the first inlet channel (13), an air output connected to the outlet channel (15) and a liquid circuit (14, 16), the heat exchange unit (11) comprising a passive air-to-liquid heat exchanger for transferring heat from air provided to said air intake to said liquid circuit (14, 16), whereby said discharge air is produced at the air output. According to the invention, the apparatus further comprises a second inlet channel (18) for outdoor air, the second inlet channel (18) being connected to the air intake of the heat exchange unit (11) so that the outdoor air can be mixed with the exhaust indoor air, and a a fan (16) downstream of first and second inlet channels (13, 18), the fan being adapted to draw air from said first inlet channel (13) and said second inlet channel (18) through the heat exchange unit (11).
    公开号:FI20185178A1
    申请号:FI20185178
    申请日:2018-02-26
    公开日:2019-08-27
    发明作者:Kari Saarinen
    申请人:Scandesco Energy Tech Oy；
    IPC主号:
    专利说明:

    Exhaust air heat recovery apparatus and method of processing exhaust air
    Field of the Invention
    The invention relates to exhaust air heat recovery technology. In particular, the invention relates to heat recovery apparatuses and exhaust air heat recovery methods. Heat recovery 5 apparatuses generally comprise an inlet channel for exhaust indoor air, an outlet channel for discharge air, and a heat exchange unit for recovering heat from the exhaust indoor air.
    Background of the Invention
    Exhaust air heat recovery systems are used to recover heat from indoor air that is exhausted and discharged from a building through ventilation. Many modern systems are 10 active systems, which employ a heat pump that is able to transfer heat from the indoor air back to the building, improving energy efficiency of the system. These are called exhaust air heat pump systems (EAHP systems). In EAHP systems the heat of the exhaust air is transferred by actively pumping with a compressor in a evaporation-condensder circuit to the fresh air led to the building, domestic hot water (DHW) system and/or central heating 15 system of the building. In centralized air-to-air heat recovery ventilation (HRV) or air conditioning systems, the heat is transferred to fresh replacement air taken in by the HRV system and delivered to the building. In decentralized replacement air systems, there are other replacement air channels in the building, such as fresh air channels on walls or windows of the building.
    Optimizing the function of an active heat recovery apparatus is a complex task. One example of centralized HRV air-to-air EAHP systems is presented in WO 2011/077007, which discloses one related apparatus with an arrangement to enhance its function. The apparatus comprises an exhaust air duct, a discharge duct, a fresh air duct and an inlet air duct. There is also provided a first evaporator-condenser unit adapted to the discharge air 25 duct and a second evaporator-condenser unit adapted to the inlet air duct. There is also a bypass channel and flow control means between the fresh air duct and the discharge air duct, prior to the first evaporator-condenser unit in the flow direction of the discharge air
    20185178 PRH 26 -02- 2018 duct and prior to the second evaporator-condenser unit in the flow direction of the inlet air duct. The bypass channel and flow control means are adapted to pass fresh air from the fresh air duct to the discharge air duct in order to enhance the function of the evaporatorcondenser unit.
    Particular control and optimization challenges are faced in decentralized replacement air heat recovery systems, because the flow of replacement air to the building is not under direct control of the HRV system but the amount of indoor air flowing through the heat pump must be high enough for heat to be efficiently recovered. For example, in manyapartment houses with a common EAHP, adjusting the air flow rates in replacement and/or 10 exhaust air channels in a single apartment affects the balance of the system and also the ventilation of other apartments in the building. This can lead to situations where the EAHP is far from its optimal point of operation and/or some apartments are facing problems relating to indoor air quality, temperature or ventilation. Another problem relating to decentralized replacement air EAHP systems relates to their relatively low coefficient of 15 performance (COP) in some situations. A still non-published Finnish patent application
    20165696 addresses these issues in EAHP systems.
    Active exhaust air heat recovery apparatuses are efficient but more expensive than passive apparatuses, since they require the installation, control system and maintenance of a heat pump and evaporator-condenser circuit in the flow path of exhaust air. In some cases, in 20 particular if the property where the apparatus is installed already contains an active pump circuit in the central heating system thereof, it is preferred to use a passive exhaust air hear recovery apparatus. However, the coming into market of active systems, the development and optimization of passive apparatuses has slowed down.
    Thus, there is a need for improved passive exhaust air heat recovery apparatuses.
    Summary of the Invention
    It is an aim of the invention to provide a novel passive exhaust air heat recovery apparatus with improved controllability and/or efficiency. A particular aim is to provide a passive apparatus, which has improved controllability and/or efficiency when installed in many
    20185178 PRH 26 -02- 2018 apartment buildings having decentralized replacement air intake system. It is also an aim to provide a related method for recovering energy in ventilation systems.
    According to one aspect, the invention provides an exhaust air recovery apparatus comprising a first inlet channel for exhaust indoor air, and an outlet channel for discharge air. Further, there is provided a heat exchange unit comprising an air intake connected to the first inlet channel, and an air output connected to the outlet channel and a liquid circuit, whereby the heat exchange unit comprises a passive air-to-liquid heat exchanger adapted to passively transfer heat from air provided to said air intake to the liquid circuit. The discharge air is thereby produced at the air output. The apparatus further comprises a second inlet channel for outdoor air, the second inlet channel being connected to the air intake of the heat exchange unit so that the outdoor air is mixed with the exhaust indoor air, and a flow control system, typically comprising at least one fan, and adapted to transport said mixed air through the heat exchange unit. Typically, the flow control system is capable of varying the ratio of mixing of the exhaust indoor air and the outdoor air.
    In a variation of this aspect, the apparatus further comprises a recirculation channel capable of recirculating part of air at the output of the heat exchange unit back to the air intake of the heat exchange unit, wherein the flow control system is further adapted to mix said outdoor air, said recirculated air or both said outdoor air and said recirculated air with said exhaust indoor air before feeding to the heat exchange unit.
    The present exhaust air process comprises recovering heat from exhaust air of a building. Thus, the method comprises exhausting air from the building to an air mixing zone and feeding air from the air mixing zone through a passive heat exchange unit comprising an air intake and an air output and being adapted to recover heat from to air provided to the intake and to provide cooled air at the output of the heat exchange unit. In variations of the method, a portion of the secondary air is recirculated back to the mixing zone and/or outdoor air is fed to the mixing zone, where the recirculated air and/or outdoor air is mixed with the exhausted air before feeding to the air intake of the heat exchange unit.
    More specifically, the invention is characterized by what is stated in the independent claims.
    The invention offers significant advantages.
    20185178 PRH 26 -02- 2018
    Particular advantages are gained in the variation with a recirculation channel and a possibility to recirculate air as well as to intake outdoor air increases the control possibilities of the apparatus, as not only the exhaust air and outdoor air can be used as a heat source but also air having passed through the heat exchanger. In addition, the apparatus is more immune to varying ventilation conditions of the building. For example, if residents in some part of the building close their exhaust or replacement air valves, the missing air in the heat recovery apparatus can be replaced with recirculated air and/or outdoor air without affecting other parts of the building. In addition, as air-to-liquid heat exchangers require a certain amount of air flowing through them in order to operate efficiently, in some conditions, it may be beneficial to recirculate part of air back to the heat exchanger and/or to add outdoor air to the air flow passing the heat exchanger even though the recirculated air, and often also outdoor air, is cooler than the “fresh” exhaust air. The amount of recirculated air and/or outdoor air can be e.g. 1... 50% of the total volume flow passing the heat exchanger. The possibility to choose between recirculated air and outdoor air, or to use both of these simultaneously, is beneficial as it makes it possible to find optimal mode of driving of the apparatus in different outdoor temperatures, for example.
    In particular, the ability to feed outdoor air, and optionally recirculated air, through the heat exchanger allows for increasing the mass flow through the heat exchanger. This allows for maximizing the efficiency of the heat exchanger. This is beneficial in the case of a passive exchanger which operates according to external conditions without feed of energy to the exchange process. This allows for transferring more energy to the liquid circuit and for example connecting the liquid circuit whereby its energy content can further be used in a large variety of passive or active external heat recovery apparatuses.
    The dependent claims are directed to selected embodiments of the invention.
    In some embodiments the flow control system comprises a fan downstream of first and second inlet channels, and downstream or upstream of the heat exchange unit, the fan being adapted to draw air from said first inlet channel and said second inlet channel through the heat exchange unit.
    20185178 PRH 26 -02- 2018
    The fan can adjustable to keep the total mass flow through the heat exchange unit at a predefined level, which is higher, such as at least 1.5 times, for example at least 2.0 times higher, than the mass flow through the first inlet channel.
    In some embodiments, the liquid circuit is a glycol circuit. Alternatively, it can be a water 5 circuit, salt water circuit or water-ethanol circuit, depending on the intended use of the circuit in other parts of the building.
    According to one embodiment, the apparatus comprises means for adjusting mixing ratio of exhaust indoor air, outdoor air and recirculated air. Typically, the apparatus can be driven in a mode of operation where a significant portion, in particular at least 25%, typically at least 50%, such as 50-95% of mixed air comprises exhaust indoor air, in terms of volume flow. The rest comprises outdoor air, recirculated air, or both.
    According to one embodiment, the recirculation channel comprises a first adjustable valve (recirculation valve) for controlling the amount of air recirculated to the air intake of the heat exchange unit. According to one embodiment, the second inlet channel for outdoor air 15 comprises a second adjustable valve (outdoor air valve) for controlling the amount of outdoor air provided to intake of the heat exchange unit through the second inlet channel. There may also be an adjustable discharge valve in the discharge channel of the apparatus, whereby the positions of the recirculation valve, outdoor air valve and discharge valve together determine the mixing ratio of the mixed air flow fed to the heat exchange unit.
    In some embodiments, there is provided a mixing zone, such as a mixing chamber, upstream of the heat exchange unit. The mixing zone is adapted to mix the exhaust indoor air with the recirculated discharge air and/or the outdoor air before feeding to the intake of the heat exchange unit. The proportions of air to be mixed are dependent on the positions of the outdoor air valve and the recirculation valve, and optionally the discharge valve.
    Embodiments with both adjustable recirculation channel and adjustable outdoor air inlet channel, and a control system for adjusting them, are particularly advantageous. They allow for adjusting the flows in varying ambient air temperature conditions and ventilation configurations, and therefore optimization of energy efficiency of the heat exchange unit.
    20185178 PRH 26 -02- 2018
    According to one embodiment, there are provided one or more temperature and/or air flow sensors within the apparatus and a control unit adapted to control the adjustable valves of the apparatus based on measurement data provided by the sensors. The control unit may be adapted to control the valves such that in a first mode of operation at least a portion of air 5 provided to the mixing zone comprises recirculated air and in a second mode of operation at least a portion of air provided to the mixing zone comprises outdoor air. In typical configurations, at least a portion of the air provided to mixing zone comprises nonrecirculated exhaust air.
    For example, the control unit may be adapted to control the flows of recirculated air and 10 outdoor air to the mixing zone based on temperature and/or air flow measurements such that a significant portion, preferably at least 25%, such as 25 ... 95%, in particular 50.. .95% of air in the mixing zone is air exhausted directly from the building, and the remaining portion is recirculated air and/or outdoor air in proportion 0:100... 100:0.
    According to one embodiment, the mixing zone comprises at least one mesh of metal through which the air is adapted to flow. This evens out temperature differences within the flow and improves the energy efficiency of the heat exchange unit.
    According to one embodiment, the apparatus is a decentralized replacement air exhaust air heat recovery apparatus, wherein the heat exchange unit is adapted to recover heat to or transfer heat from a liquid circuit connectable to heat distribution system of a building.
    Thus, there are no replacement air channels in the apparatus that would be suitable for conducting fresh outdoor air to the building. Instead of that, the replacement air channels form a separate functional system in the building. In particular, the replacement air channels can be distributed on outer walls and/or windows of different rooms of the building.
    According to one embodiment, the heat exchange unit comprises a exchanger such as a plate exchanger e.g. with air flow channels between parallel metal plates. There may also be a cascade of two of more heat exchangers. In this case, the recirculation channel, if present, is arranged to convey air from air output of the last exchanger to air input of the single heat exchanger or the first heat exchanger of the cascade.
    20185178 PRH 26 -02- 2018
    According to one embodiment, the apparatus comprises one or more exhaust fans downstream of the heat exchange unit, the fan(s) being adapted to transfer the exhaust air from the building to the mixing zone. Flow of recirculated air can be adjusted by means of a valve in the recirculation channel in the presence of pressure caused or contributed by the 5 fan.
    In some embodiments, there are only two fans or fan groups in the apparatus, i.e., an exhaust air fan (group) and the fan (group) downstream of the heat exchage unit, using which all the air flows are made to occur as determined by valves in respective channels.
    According to one embodiment, heat is recovered by the heat exchanger to a liquid curcuit, 10 in particular a glycol circuit, which is further connected to the central heating water and/or domestic hot water reservoir of the building.
    In a typical installation environment, the exhausting comprises collecting air from at least ten different rooms of the building, and providing at least part of replacement air to said room via decentralized replacement air channels, i.e. outside the present apparatus. The 15 present invention is most beneficial in many-apartment houses with at least 10 apartments, such as 10 - 100 apartments, a centralized exhaust ventilation system, and decentralized replacement air system (many replacement air intake points). In such buildings, the ventilation conditions are continuously changing due to changing of ambient conditions and actions of the residents of the building, whereby improved controllability of ventilation 20 and heat recovery is needed without sacrificing performance too much.
    Next, embodiments of the invention and advantages thereof are discussed in more detail with reference to the attached drawings.
    Brief Description of the Drawings
    Fig. 1 shows schematically an AEHP apparatus according to one embodiment of the 25 invention.
    Figs. 2A and 2B show in more detail the construction of a heat recovery apparatus as side and top views, respectively, according to one embodiment.
    Figs. 3 A and 3B illustrate in two different views a temperature evening assembly.
    20185178 PRH 26 -02- 2018
    Fig. 4 depicts a building provided with a heat recovery apparatus according to one embodiment of the invention.
    Fig. 5 illustrates a heat recovery method according to one embodiment of the invention.
    Fig. 6 shows an alternative heat recovery apparatus, containing an additional heat transfer 5 element for efficient flow control and heat recovery.
    Detailed Description of Embodiments
    In the following description, embodiments of the passive exhaust air heat recovery apparatus comprising both the outdoor air inlet channel and recirculation channel are described, the apparatus thereby that allowing wide optimization of efficiency in varying 10 conditions.
    “Passive” heat recovery apparatus, heat exchange unit or heat exchanger herein means a device without a heat pump, i.e., a compressor and evaporator-condenser circuit, or any analogous electrically powered unit that actively transfers heat from the exchange air flow to the liquid circuit. This does not exclude the use of a fan or fans that cause air and/or 15 liquid circulation in the unit, the fan(s) typically being placed outside of the exchanger.
    With reference to Fig. 1, the exhaust air heat recovery apparatus 10 comprises a heat exchange unit 11, which forms the heat recovery core of the apparatus 10. There is provided a first inlet channel 13 for exhaust indoor air flow Fe. The inlet channel 13 is connected to a mixing zone 22. The mixing zone 22 is further connected to air intake of the 20 heat exchange unit 11 for providing an exhange flow Fh through the exchange unit 11. In the heat exchange unit 11, a heat flow is formed from exchange flow Fh to a liquid circuit 14, comprising a liquid inlet 14A and liquid outlet 14B. There is also provided an outlet channel 15 to outdoors for discharge air flow Fd passing the heat exchange unit. However, there is provided a recirculation channel 17 for directing part of the air passing the heat 25 exchange unit 11, i.e. recirculation flow Fr, back to the mixing zone 22. Thus, when the recirculation channel 17 is in use, the exchange flow Fh is a sum of exhaust air flow Fe and recirculation flow Fr.
    20185178 PRH 26 -02- 2018
    There is also provided a second inlet channel 18 for outdoor air flow Fo. Also this inlet is connected to the mixing zone 22, adding a third potential sum component to the exchange flow Fh, namely the outdoor flow Fo.
    The apparatus can be used in different modes of operation. In one mode, the exchange flow 5 Fh essentially consists of the exhaust flow Fe, recirculation flow Fr and outdoor air flow Fo in a chosen mixing ratio. In another mode, the exchange flow Fh essentially consists of the exhaust flow Fc and recirculation flow Fr in a chosen mixing ratio. In still another mode, the exchange flow Fh essentially consists of the exhaust flow Fe and outdoor air flow Fo in a chosen mixing ratio. In all cases, the exhaust flow Fe preferably forms at least 25%, in particular at least 50% of the total exchange flow Fh in terms of volume flow.
    The mixing zone 22 in front of the heat exchange unit 11 is used to even out temperature and pressure differences in the various flows such that the heat exchange flow Fh is as homogeneous as possible and the exchange unit 11 will operate optimally. The mixing zone 22 may comprise a chamber with a volume sufficient for the air flows to mix. In 15 addition, there may be provided additional temperature evening means, such as a stack of metal wires or meshes that facilitate evening out of temperature differences.
    According to one embodiment, the mixing zone is adapted to even out the temperature such that in the mixed air flow fed to the heat exchange unit temperature unevenness, i.e. maximum temperature difference between different cross-sectional points of the flow, is at 20 maximum half, in particular at maximum a quarter, of the maximum difference between temperatures of the incoming flows.
    Figs. 2A and 2B show an exemplary structure of the exhaust air heat recovery apparatus 10 installed on a roof of a building. In the exemplary configuration, an insulation layer 109 is provided between the roof and the apparatus 10 for reducing transfer of vibrations. The exhaust air is provided through ventilation channels 13 A from different parts of the building to a common collector chamber 13B. An exhaust fan 101 causes an underpressure that causes the exhaust air to enter a mixing chamber 103 of the apparatus. Between the mixing chamber 103 and the heat exchange unit 11, there is provided a temperature evening assembly 105 through which the air flow passes on its way to an intake chamber
    1 IB of the heat exchange unit 11. The exchange fan 16 causes the air to pass the heat
    20185178 PRH 26 -02- 2018 exchange unit. The heat exchange unit flow channel may secured with one or more seal elements 1 ID that ensure that all air goes through heat transfer zone (not specifically shown) of the heat exchange unit 11. The heat exchange unit 11 comprises also connectors 111 of the liquid circuit to which the heat is recovered for guiding the liquid for further 5 use.
    Air exiting the heat exchange unit 11 is directed to a circulation chamber 12 from which there are two exits. One of the exist leads to the ambient air space through an adjustable discharge valve 15A, optionally via a discharge chamber 15B. The discharge chamber 15B is formed by a weather shield 15C preventing water or snow from entering the apparatus.
    The other exit leads to a recirculation channel 17B through an adjustable recirculation valve 17 A.
    The recirculation channel 17B leads to the mixing chamber 103 through optional recirculation air grate 17C. In the described way, the recirculation flow Fr is controlled by the positions of the valves 15 A, 17A without any additional fans. Although herein 15 presented as to separate components, valves 15A, 17A can also be understood and, if desired, also physically implemented as a single discharge/recirculation valve.
    The exemplary apparatus comprises also the possibility to mix fresh outdoor air to the exchange flow Fh. For this purpose, there is provided an outdoor air intake valve 18A, which, when open, allows ambient outdoor air flow Fo to enter the mixing chamber 103 20 due to pressure caused by the fan 16. The ambient air is taken from an outdoor air intake chamber 18B defined by a weather shield 18C. In the mixing chamber 103, the oudoor air is mixed with the exhaust air and recirculated air before feeding to the intake chamber 1 IB of the heat exchange unit 11. The intake air temperature of the heat exchange unit is thus determined by the temperatures and magnitudes of the exhaust, recirculation and oudoor 25 air flows.
    As illustrated in Fig. 2A, the mixing chamber may comprise one or more flow direction plates 104, which assist the exhaust air flow Feto be directed towards the heat exchange unit 11. The plates 104 can be generally oblique with respect to the original (upwards) direction of the exhaust air flow Fe. The plates 104 are arranged so that they let the 30 recirculation flow Fr and/or the outdoor air flow Fo through to the heat exchange unit 11.
    20185178 PRH 26 -02- 2018
    There may for example be a plurality of oblique plates 104 placed one after another and at a distance from each other, like exemplified in Fig. 2A.
    There may be provided a control unit (not shown) functionally connected to the valves
    A, 17A, 18A. The control unit can be configured to drive the apparatus selectively into 5 a first mode of operation, where only outdoor air is mixed with exhaust air, into a second mode of operation, where only recirculated air is mixed with exhaust air, and optionally into a third mode of operation, where both outdoor air and recirculated are mixed with exhaust air before feeding to the heat exchange unit.
    In some embodiments, the outdoor air valve 18A is replaced with non-adjustable intake 10 means, such as non-regulated (static) apertures. Thus, the amount outdoor air flow Fo is passively determined based on the pressure difference between the mixing chamber 103 and the environment. Depending i.a. on the speeds of the fans 105, 106, the flow through the valve 18A or non-regulated apertures is either inwards or outwards.
    There may be provided one or more temperature sensors (not shown) in the collector 15 ventilation channel 43 (for measuring the temperature of the exhaust air flow), recirculation channel 17B (recirculation flow), outdoor air intake chamber 18B (outdoor flow) and/or the heat exchange unit unit (exchange flow). The sensors are functionally connected to the control unit to provide input data for a control algorithm running therein.
    The heat exchange unit may comprise any passive air-to-liquid exchanger element, manny 20 kind of which are known per se. Plate exchangers with several heat transfer plates thermally connected to one or more liquid pipes of the liquid circuit and allowing air to flow between them are the most common. The exchanger can be in countercurrent configuration where the temperature gradients of the air flow and the liquid flow being essentially in opposite directions to maximize transfer efficiency.
    Figs. 3 A and 3B show an exemplary temperature evening element 105, which comprises stack of a plurality, in this case four, metal meshes, such as aluminum meshes that are thermally well conductive. This kind of an element 105 is efficient and easy to keep clean by e.g. waterjet, and allows for a filterless apparatus design.
    20185178 PRH 26 -02- 2018
    Valves 15A, 17A, 18A may comprise plate valves driven by motors controlled by a control unit (not shown).
    Fig. 4 shows a many-apartment building 41 with the present apparatus 40 installed on top of it. The building comprises ventilation channels 42 in each apartment and/or room 49 5 thereof, and a collector ventilation channel 43, that are designed to provide an exhaust air flow Fe which is directed to the exhaust air channel of the apparatus 40 operating in the way described above. Replacement air flows to the apartments/rooms 49 of the building are denoted with numeral 48.
    The liquid circuit of the apparatus, to which the heat is recovered, can be connected to a 10 central heating or domestic water heating system of the building, this system not being part of the present apparatus. Heat may be transferred from the liquid circuit passively or actively to a central heating or domestic hot water reservoir. There may be one or more heat pumps that use the present liquid circuit as its primary circuit. The present apparatus allows for converting an existing ground heat pump system or outdoor-air-to-water heat 15 pump system to, or supplementing the same with, an exhaust air recovery system.
    Fig. 5 illustrates the present heat recovery method. The heat recovery process is started in step. After that, magnitudes of air flows and/or temperatures thereof are measured and input to a monitoring and control system in step 52. The monitoring and control system runs an algorithm based on which the proportions of recirculation air flow Fr and the outdoor air flow Fo of the total exchange flow Fh are adjusted using suitable control electronics and mechanics.
    Fig. 6 shows a variation of the apparatus shown in Figs 2A and 2B. The apparatus comprises the same basic components but has a heat transfer element 606 provided in or in front of the mixing chamber 603.
    The heat transfer element 606 is placed in front of the heat exchange unit so as to transfer heat between outdoor air, recirculated air, exhaust indoor air, and optionally outdoor air, before mixing them for feeding to the heat exchange unit. In addition, the heat transfer element 606 may also comprise a branch outlet for the recirculated air for drawing not all of the recirculated air to back the heat exchange unit but a part of it to the environment through the heat transfer element.
    20185178 PRH 26 -02- 2018
    The heat transfer element 606 has an inlet for the exhaust air flow Fe, an inlet for recirculated air flow Fr, and, optionally, for outdoor intake air flow Fo. In addition, it comprises at least one outlet through which the exhaust air flow Fe, an inlet for recirculated air flow Fr, and, optionally, the outdoor intake air flow Fo having passed the heat transfer 5 element is conducted towards the heat exchange unit as heat exchange air flow Fh.
    The heat transfer element 606 may contain internal flow channels, through which the flows run and between which temperature differences even out. Thus, the heat transfer cube may supplement or entirely replace the temperature evening element 105 shown in in Figs. 2A and 2B. In addition to evening the temperatures, the element 606 may be configured to 10 affect the magnitudes of the various flows running therein so as to fine-tune the operation of the apparatus.
    According to one embodiment, the heat transfer element 606 comprises an additional outlet for recirculation outlet flow Fro, which is therefor arranged to bypass the heat exchange unit directly to the outside. The magnitude of the recirculation outlet flow Fro can generally 15 equal to 0 ... Fr. Preferably, its magnitude is passively determined in the heat transfer element 606 based on the magnitudes and/or temperatures of the flows Fe, Fr and Fo according to predefined criteria, for example for maximizing the efficiency of the apparatus under prevailing flow and temperature conditions. There may be mechanical passively moving members in the element 606 for adjusting Fro or the desired adjusting can 20 be achieved only by dimensioning of the flow channels within the element 606. Thus, the heat transfer element 606 may act as an entirely passive efficiency control unit.
    The flow channels of the heat transfer element are preferably separated by metal plates, and may operate according to the parallel-flow or cross-flow principle or a combination of these. The heat transfer element may for example form an octahedron, such as a cube filled 25 with the flow channels.
    It has been found that a heat transfer element placed in front of the heat exchange unit can increase the efficiency and tenability of the apparatus significantly in particular in low outside temperature conditions and when at least one of the flows Fr and Fo is active.
    Next, an exemplary control scheme of the apparatus is described.
    20185178 PRH 26 -02- 2018
    Let total target exchange flow Fh be equal to X units (e.g. X = 2 m3/s).
    In a first (classic) state recirculation valve 17A and outdoor air valve 18A are closed, whereby the exchange flow Fh is formed solely by exhaust air. Thus, Fe and Fd equal to X units and Fo = Fr = 0
    In a second (recirculation intensive) state, recirculation valve 17A is opened and oudoor air valve 18A stays closed, whereby Fr equals to y units (y < X; e.g. y = 1 m3/s) and Fe and Fd equal to X - y units (1 m3/s). Fo = 0.
    In a third (outdoor air intensive) state, recirculation valve 17A is closed and outdoor air valve 18A opened, whereby Fo equals to z units (z < X; e.g. z = 1 m3/s) and Fe equals to X 10 z units (1 m3/s). Fr = 0 and Fd = X units (2 m3/s).
    The control system is designed such that it is able to adjust the state flexibly between the second and third states such that both the recirculation valve 17A and outdoor air valve 18A may be simultaneously open, and 0 < Fr < X, 0 < Fo < X and Fe + Fr + Fo = Fh= X.
    The control system may have certain boundary conditions implemented, such as Fe > X/4, 15 or Fe > X/2 and/or Fh > Fh,min, where Fh,min is the minimum flow required through the exchange unit. An algorithm running in the control unit takes into account the boundary conditions and measurement data from the apparatus, and determines optimal values for the various flows. Then, the control system drives the apparatus into a corresponding mode of operation, which uses the flows determined.
    According to one embodiment, the control system is adapted to seek the maximum temperature of the total exchange flow Fh, by changing the proportions of the exhaust flow Fe, recirculation flow Fr and outdoor air Foflow..
    Industrial applicability
    The invention is industrially applicable and provides benefits over known systems, as can be understood through theoretical considerations.
    Generally, the mass flow of mixed air through the heat exchange unit is
    20185178 PRH 26 -02- 2018 q = qs + qu + β(ΐ where qs is the mass flow of indoor air, qu is the mass flow if outdoor air, and β is the proportion of air that is recirculated. In terms of heat content, this can be written as cqT = cqsTs + cquTu + βcqTj where c is the specific heat capacity of air, T the temperature of mixed air, Ts the temperature of indoor air, Tu the temperature of outdoor air and Tj the temperature of discharge air (in Kelvin units). Thus, the temperature of mixed air is T _ qsTs + quTu + βqTj q
    Assuming that the sum of outdoor air and recirculated air flows is constant, i.e.,
    q. + Jq = k it can be shown that
    T = 9‘T‘ + kT“ + I3I.T, - T„)
    The function Τ(β) is thus linear function with the slope Tj-Tu. If Tj > Tu, the function has a maximum at β = 1-qTq, whereby qu = 0, i.e., the outside air flow is zero. On the other hand, if Tj < Tu, the function has maximum at β = 0, whereby qt = 0, i.e., the circulated air flow is zero.
    Using this simplified model, and assuming that the efficiency of the heat exchange unit is proportional to the temperature of the air taken in, it can be concluded that the present hybrid apparatus with both outdoor air intake and recirculation allows for choosing optimal mixed air composition in varying circumstances. Thus, with the present apparatus, one can choose a mode of operation, which maximizes the efficiency of the apparatus.
    One can also estimate a threshold value for the outside temperature, below which it is more beneficial to use recirculated air. With normal indoor air temperature and heat exchange unit performance parameters, it can be estimated that the threshold value is typically between -10°C and 0°C. Such predefined threshold value, together with outside air temperature measurement, can be used by the control algorithm for determining the mixing ratio of outside air and recirculated air.
    20185178 PRH 26 -02- 2018
    List of reference numbers 10Exhaust air heat recovery apparatus1011Passive heat exchange unit 11BIntake air chamber 11DSeal 12Circulation chamber 13First inlet channel for exhaust indoor air1513AVentilation channel 13BCollector chamber 14Liquid circuit 14ARecovery liquid circuit inlet 14BRecovery liquid circuit outlet2015Outlet channel for discharge air (to outdoors) 15ADischarge valve 15BDischarge chamber 15CWeather shield 16Fan2517Recirculation channel 17ARecirculation valve 17BRecirculation channel 17CRecirculation air grate 18Inlet channel for outdoor air3018AOutdoor air intake valve 18BOutdoor air intake chamber
    20185178 PRH 26 -02- 2018
    C Weather shi el d
    Mixing zone
    Heat recovery apparatus
    Building
    42 Apartment/room ventilation channel
    Collector ventilation channel
    Exhaust air flow
    Discharge air flow
    Replacement air flow
    49 Apartment/room
    101 Exhaust fan
    103 Mixing chamber
    105 Temperature evening mesh assembly
    105A-D Temperature evening mesh
    109 Insulation
    111 Connectors for liquid circuit
    606 Heat transfer element
    Fe Exhaust air flow
    Fo Outdoor intake air flow
    Fr Recirculation flow
    Fr Recirculation outlet flow
    Fh Heat exchange air flow
    Fd Discharge air flow
    权利要求:
    Claims (19)
    [1] Claims
    1. An exhaust air heat recovery apparatus (10, 40), comprising
    - a first inlet channel (13) for exhaust indoor air,
    - an outlet channel (15) for discharge air,
    5 - a heat exchange unit (11) comprising an air intake connected to the first inlet channel (13), an air output connected to the outlet channel (15) and a liquid circuit (14, 16), the heat exchange unit (11) comprising a passive air-to-liquid heat exchanger for transferring heat from air provided to said air intake to said liquid circuit (14, 16), whereby said discharge air is produced at the air output,
    10 characterized in that the apparatus further comprises
    - a second inlet channel (18) for outdoor air, the second inlet channel (18) being connected to the air intake of the heat exchange unit (11) so that the outdoor air can be mixed with the exhaust indoor air,
    - a fan (16) downstream of first and second inlet channels (13, 18), the fan being
    15 adapted to draw air from said first inlet channel (13) and said second inlet channel (18) through the heat exchange unit (11).
    [2] 2. The apparatus according to claim 1, characterized by comprising a flow control system capable of varying the ratio of mixing of the exhaust indoor air and the outdoor air before feeding the mixed air through the heat exchange unit (11).
    20
    [3] 3. The apparatus according to claim 1 or 2, characterized in that the liquid circuit is a glycol circuit or water-ethanol circuit.
    [4] 4. The apparatus according to any of the preceding claims, characterized in that the apparatus further comprises a recirculation channel (17) capable of recirculating part of air at the output of the heat exchange unit (11) back to the air intake of the heat exchange unit 25 (11), wherein the apparatus is further adapted to mix said outdoor air, said recirculated air or both said outdoor air and said recirculated air with said exhaust indoor air before feeding to the heat exchange unit (11).
    20185178 PRH 26 -02- 2018
    [5] 5. The apparatus according to claim 4, characterized by comprising means for adjusting mixing ratio of said exhaust indoor air, said outdoor air and said recirculated air.
    [6] 6. The apparatus according to claim 4 or 5, characterized in that the recirculation channel (17) comprises a first adjustable valve (17A) for controlling the amount of air recirculated
    5 to the air intake of the heat exchange unit (11) and a second adjustable valve (18A) or nonadjustable inlet for controlling the amount of outdoor air provided to the intake of the heat exchange unit (11).
    [7] 7. The apparatus according to claim 6, characterized by comprising a control unit functionally connected to said first and second adjustable valves (17A, 18A), the control
    [8] 10 unit being capable to drive the apparatus selectively into a first mode of operation, where only outdoor air is mixed with exhaust air, and into a second mode of operation, where only recirculated air is mixed with exhaust air, and optionally into a third mode of operation, where both outdoor air and recirculated are mixed with exhaust air before feeding to the heat exchange unit (11).
    15 8. The apparatus according to any of claims 6-7, characterized by comprising
    - one or more temperature and/or air flow sensors associated with said first inlet channel (13), second inlet channel (18) and/or said recirculation channel (17) and
    - a control unit adapted to control the first and second adjustable valves (17A, 18A) based on measurement data provided by said one or more sensors.
    20 9. The apparatus according to any of claims 4-8, characterized by comprising a heat transfer element (606) placed upstream of the heat exchange unit (11), the heat transfer element (606) being arranged to transfer heat between exhaust indoor air and recirculated air, and optionally outdoor air, before mixing the same for feeding to the heat exchange unit (11), the heat transfer element preferably comprising a branch outlet for the
    25 recirculated air.
    10. The apparatus according to any of claims 4-9, characterized in that it is adapted, in at least one mode of operation, to mix outdoor air and/or recirculated air to the mixed air flow such that at least 5 %, for example 5... 50% of the mixed air flow comprises outdoor air and/or recirculated air, in terms of volume flows.
    20185178 PRH 26 -02- 2018
    [9] 11. The apparatus according to any of claims 4 - 10, characterized by comprising means for freely adjusting the mixing ratio of outdoor air and recirculated air.
    [10] 12. The apparatus according to any of claims 4-11, characterized in that the fan (16) is located upstream or downstream of the heat exchange unit for conveying air through the
    5 heat exchange unit (11), and wherein said recirculation of air through the air recirculation channel (17) is adapted to occur solely due to air pressure caused by said fan (16).
    [11] 13. The apparatus according to any of the preceding claims, characterized by comprising a mixing chamber (103) upstream of the heat exchange unit (11), whereby the first and second inlet channels (13, 18), and optionally the recirculation channel (17), are connected
    10 to the mixing chamber (22) for carrying out said mixing.
    [12] 14. The apparatus according to claim 13, characterized in in that the mixing chamber comprises one or more flow direction plates (104) for redirecting the exhaust air flow towards the heat exchange unit (11), the plates (104) being arranged so that they let the outdoor air, and optionally the recirculated air, through to the heat exchange unit (11), the
    [13] 15 plates for example comprising a plurality of oblique plates (104) placed one after another and at a distance from each other and being oblique with respect to original direction of the exhaust air flow entering the apparatus.
    15. The apparatus according to claim 13 or 14, characterized in that the mixing chamber (103) comprises at least one mesh (105A-D) of metal through which the air is adapted to 20 flow for evening the temperature of air flow fed to the intake of the heat exchange unit (H)·
    [14] 16. The apparatus according to any of the preceding claims, characterized by being a decentralized replacement air exhaust air heat apparatus, wherein the heat exchange unit (11) is adapted to exchange heat passively to a liquid circuit connectable to heat
    25 distribution system of a building.
    [15] 17. The apparatus according to any of the preceding claims, characterized in that said fan (16) is adjustable to keep the total mass flow through the heat exchange unit (11) at a predefined level, which is higher, such as at least 1.5 times, for example at least 2.0 times higher, than the mass flow through the first inlet channel (13).
    20185178 PRH 26 -02- 2018
    [16] 18. A method of processing exhaust air of a building (41), the method comprising
    - exhausting air from the building to an air mixing zone (22),
    - feeding air from the air mixing zone (22) through a heat exchange unit (11) comprising an air intake, an air output, and a liquid circuit (14, 16), the heat
    5 exchange unit (11) comprising a passive air-to-liquid heat exchanger for transferring heat from air provided to said air intake to said liquid circuit (14, 16) and being adapted to recover heat from air provided to the intake and to provide cooled air at the output of the heat exchange unit (11), characterized by
    10 - feeding outdoor air to the air mixing zone (22),
    - mixing the outdoor air with the exhausted air in said mixing zone (22) before feeding the mixed air to the heat exchange unit (11).
    [17] 19. The method according to claim 18, characterized by recirculating a portion of the cooled air back to the mixing zone (22) and mixing the recirculated air with the outdoor air
    15 and exhausted air in said mixing zone (22).
    [18] 20. The method according to claim 18 or 19, characterized in that
    - said exhausting comprises collecting air from at least ten different rooms (49) of the building (41), and
    - providing at least part of replacement air to said rooms (49) via decentralized
    20 replacement air channels, and
    - recovering said heat to a heating water or domestic water reservoir of the building.
    [19] 21. The method according to any of claims 18-20, characterized by using an exhaust air heat recovery apparatus (10, 40) according to any of claims 1 - 17.
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    FI128692B|2020-10-15|
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