Patent Grant
12188697
This application claims the benefit of PCT/GB2020/0522924 filed on 16 Nov. 2020 under 35 USC § 365.
The present invention relates to heat pumps and more particularly, but not exclusively, to heat pumps for domestic and commercial premises.
A large proportion of the energy footprint of buildings is consumed in heating the interior of the building, with a substantial proportion of the heating loss being through ventilation, commonly 30%. Traditionally, buildings have been ventilated by releasing exhaust air directly from the interior to the exterior of the building, wasting the heat carried by the exhaust air. In active heat recovery, exhaust air heat pumps have been used to extract heat from exhaust air, with the heat being pumped into the fresh supply air, or supplied to a heating element within the interior of the building. However, there remains a need to improve the heating of buildings using heat pump systems.
According to a first aspect, there is provided a heat pump adaptor system for coupling to the refrigerant flow path and air flow path of a heat pump to form a heat pump system with a heating mode refrigerant flow path comprising:
According to a second aspect, there is provided a heat pump system, in accordance with the first aspect, and with a heating mode refrigerant flow path comprising:
According to a third aspect, there is provided a method of heating a building provided with a heat pump system with a heating mode refrigerant flow path comprising:
According to a fourth aspect, there is provided a method of cooling a building provided with a heat pump system with a cooling mode refrigerant flow path comprising:
The first air flow conduit may be provided with a first air pump for pumping air through the first air inlet.
The heat pump adaptor system may comprise a mixing chamber having a second air inlet provided for receiving and mixing air from the first air flow conduit and the second air inlet to form a mixed air flow and for coupling the mixed air flow to the second air flow conduit.
The second air inlet may be provided with a third air pump for pumping air into the mixing chamber from the second air flow conduit.
The mixing chamber may be provided with a perforated screen, and air from the first air flow conduit and the second air inlet may be coupled to the second air flow conduit by passage through the perforated screen.
The compressor may have first and second gas inlets.
The compressor may be a vapour injection compressor. The vapour injection compressor may be a vapour injection scroll compressor. The vapour injection compressor may be a vapour injection screw compressor. The vapour injection compressor may be a multistage centrifugal compressor.
The first evaporator may be provided within a first evaporator refrigerant conduit and have a first external surface area for exposure to air in the first air flow conduit, the second evaporator may be provided within a second evaporator refrigerant conduit and have a second external surface area for exposure to air in the second air flow conduit, and the second external surface area may be larger than the first external surface area.
The first air flow conduit may be provided with a first air pump for pumping air through the first air flow conduit.
The second air flow conduit may be provided with a second air pump for pumping air through the second air flow conduit.
A mixing chamber having a second air inlet may be provided for receiving and mixing air from the first air flow conduit and the second air inlet to form a mixed air flow and for coupling the mixed air flow to the second air flow conduit.
The second air inlet may be provided with a third air pump for pumping air into the mixing chamber from the second air flow conduit.
The mixing chamber may be provided with a perforated screen, and air from the first air flow conduit and the second air inlet may be coupled to the second air flow conduit by passage through the perforated screen.
The heat pump system may be configured for switching between a heating mode of operation and a cooling mode of operation.
The refrigerant flow path may comprise switchable valves that are switchable to close portions of the refrigerant flow path for the heating mode of operation, and to open alternative refrigerant flow paths to provide a modified refrigerant flow path for the cooling mode of operation.
The heat pump system may comprise, in the cooling mode of operation:
The heat pump system may comprise a mixing chamber having a second air inlet provided for receiving and mixing air from the first air flow conduit and the second air inlet to form a mixed air flow and for coupling the mixed air flow to the second air flow conduit,
the method may comprise:
The heat pump system may comprise a mixing chamber having a second air inlet provided for receiving and mixing air from the first air flow conduit and the second air inlet to form a mixed air flow and for coupling the mixed air flow to the second air flow conduit,
the method comprising:
Examples are further described hereinafter with reference to the accompanying drawings, in which:
In the described examples, like features have been identified with like numerals, albeit in some cases having one or more suffix letters. For example, in different figures, L0, L1, L2, L2sc, L0′, L0sc′, L1sc′, L2sca′ and L2scb′ have been used to indicate liquid refrigerant.
The air flow path has a first air inlet IN1 for receiving exhaust air flow A1 (e.g. at 20° C.) from a building into a first air flow conduit C1. A first evaporator EVP1 (first refrigerant-air heat exchanger) is provided within the first air flow conduit C1 for recovering heat from the exhaust air flow A1 flowing through the first evaporator EVP1, and transferring the recovered heat into the refrigerant passing through the first evaporator EVP1. The air leaving the first air flow conduit C1 (e.g. at 10° C.) is coupled into a second air flow conduit C2. A second evaporator EVP2 (second refrigerant-air heat exchanger) is provided within the second air flow conduit C2 for recovering heat from the air flowing through the second evaporator EVP2, and transferring the recovered heat into the refrigerant passing through the second evaporator EVP2 before the outlet air flow A3 (e.g. at −3° C.) is coupled out of the air outlet OUT.
In the illustrated heat pump system 100, the air flow path is (optionally) provided with a second air inlet IN2 for receiving ambient air flow A2 (e.g. at 1° C.), which is mixed with the exhaust air flow A1 in a mixing chamber (mixing conduit) CM, before the mixed exhaust air flow A1 and ambient air flow A2 (e.g. mixed air at 2° C.) flow into the second air flow conduit C2. The illustrated mixing chamber CM is additionally (optionally) provided with a perforated screen PS to enhance mixing of the exhaust air flow A1 received from the first evaporator EVP1 and the ambient air flow A2 from the second air inlet IN2.
The heat pump system 100 may be provided with one or more fans F1, F2, F3 to drive the air flow A1, A2, A3 through the air flow path. Alternatively, the air flow(s) may be driven by external components to which the air flow path of the heat pump system 100 is coupled. In the case that the heat pump system 100 is provided with a second air inlet IN2 for receiving and mixing ambient air flow A2 into the exhaust air flow A1, the provision of two or more fans F1, F2, F3 in, or coupled to, different air flow conduits (first air inlet IN1, second air inlet IN2, air mixing chamber MC, and the air outlet OUT) enables control of the ratio of the exhaust air flow A1 and the ambient air flow A2.
The heating mode refrigerant flow path forms a closed, streamed refrigerant circuit around which the refrigerant circulates, in use, which is described below, for the refrigerant R-410A.
In the heating mode common refrigerant stream:
A vapour injection compressor is adapted to compress both a lower pressure and a higher pressure gas stream, and is particularly suited for use as the compressor in the present heat pump system. A vapour injection compressor may improve performance of the heat pump system, by reducing thermodynamic irreversibility during the throttling process, which may be particularly beneficial when the temperature difference between the hot and cold sides of the heat pump system is large. The compressor COMP may be a vapour injection scroll compressor. The vapour injection compressor may be a vapour injection screw compressor or a multistage centrifugal compressor.
In the heating mode first refrigerant stream:
In the binary phase refrigerant, dryness is defined as follows:
In the heating mode second refrigerant stream:
As a result of the transfer of heat from the liquid refrigerant L2 in the heating mode second refrigerant stream to the higher dryness binary phase refrigerant B1b in the heating mode first refrigerant stream, within the heat exchanger (heating mode first refrigerant stream-to-second refrigerant stream heat exchanger) HX:
The described heating mode refrigerant temperatures and pressures correspond with a heat pump operating with −5.0° C. ambient air A2, 20° C. exhaust air flow A1 entering the first evaporator EVP1, 10° C. air flow exiting the first evaporator EVP1, and −7.8° C. outlet air flow A3.
The coefficient of performance (COP) of a heat pump is determined by the difference between the condensation and evaporation temperatures (the hot and cold side temperatures of the heat pump system, respectively), with a smaller difference producing a higher COP. The first evaporator EVP1 is exposed to the exhaust air flow A1 received by the heat pump system, which typically has a higher temperature than the air to which the second evaporator EVP2 is exposed (being the air that has flowed over the first evaporator, and which is optionally mixed with ambient air flow A2), resulting in a higher evaporation temperature in the first evaporator EVP1 than in the second evaporator EVP2. Through the use of two evaporators EVP1 and EVP2 in different refrigerant streams, with a higher evaporation temperature within the first evaporator EVP1, the present heat pump system effectively has a higher overall evaporation temperature, producing a higher COP.
A vapour injection compressor is adapted to compress a lower pressure and a higher pressure gas stream, and is particularly suited to the present heat pump system.
The mass flow rate through the heating mode second refrigerant stream (e.g. through the second evaporator EVP2) may be higher than the mass flow rate through the heating mode first refrigerant stream (e.g. through the first evaporator EVP1). The ratio of mass flow rates corresponds to the ratio of thermal recovery from the first and second evaporators EVP1, EVP2. Where the heat pump system provides all of the heat to a building, thermal loss by exhaust ventilation may be less than half of the total thermal loss of the building, and the more heat may be recovered from the heating mode second refrigerant stream than from the heating mode first refrigerant stream. The ratio of mass flow rates of the heating mode first refrigerant stream:heating mode second refrigerant stream may be between 0.4:1 and 0.9:1.
The ratio of mass flow rates in the heating mode first and second refrigerant streams may be controlled in correspondence with the ambient air temperature, the exhaust air temperature, the condensation temperature (e.g. temperature of load water circulating to the condenser COND), and the power of the compressor COMP. The first throttle valve TEV1 and the second throttle valve TEV2 may be controlled to regulate the mass flow rates in the heating mode first and second refrigerant streams, respectively.
The heating mode first and second refrigerant streams in the heat pump system may be respectively provided with a first temperature sensor TS1 for measuring the temperature of the vapour V1 output from the heat exchanger HX and flowing to the higher pressure input of the compressor COMP, and a second temperature sensor TS2 for measuring the temperature of the vapour V2 output from the second evaporator EVP2 and flowing to the low pressure input of the compressor COMP. The first and second temperature sensors TS1, TS2 respectively provide feedback used to control the first throttle valve TEV1 and the second throttle valve TEV2, ensuring that the refrigerant is fully vaporised at the locations of the temperature sensors TS1, TS2. In the heating mode first refrigerant stream, the first temperature sensor TS1 may be located downstream of the heat exchanger HX. In the heating mode second refrigerant stream, the second temperature sensor TS2 may be located downstream of the second evaporator EVP2. The temperature sensors TS1, TS2 provide temperature readings that respectively corresponds with the temperature of the refrigerant V1, V2 exiting the heat exchanger HX and the second evaporator EVP2, which is related to the temperature of the air flow A1, A2 passing through the evaporators EVP1, EVP2. The mass flow rates through the first throttle valve TEV1 and the second throttle valve TEV2 may be controlled in correspondence with the respective temperatures of the refrigerant vapours V1, V2 exiting the heat exchanger HX and the second evaporator EVP2.
A higher refrigerant V1, V2 temperature at the temperature sensor TS1, TS2 provides feedback that controls the throttle valve TEV1, TEV2 to increase the mass flow rate through the throttle valve TEV1, TEV2. If the temperature of the air flow A1, A2 passing into the evaporators EVP1, EVP2 changes, the mass flow rate through the throttle valves TEV1, TEV2 will change in correspondence.
Examples of suitable refrigerant are R-410A (a zeotropic, but near-azeotropic mixture of difluoromethane {R-32} and pentafluoroethane {R-125}), R-22 (Chlorodifluoromethane), or R-134A (1,1,1,2-Tetrafluoroethane).
Advantageously, the use of a second evaporator EVP2 and a heat exchanger HX that transfers heat from the liquid refrigerant flow L2 in the heating mode second refrigerant stream of the refrigerant circuit to the higher dryness binary phase refrigerant B1b in the heating mode first refrigerant stream, enables additional heat to be recovered from the exhaust air flow A1, beyond what would be recovered with only a single stage evaporator heat recovery process. Also, by the use of the heat exchanger HX, and the supporting refrigerant circuit, the heat pump system is able to recover more heat from exhaust air flow A1 than a two-stage evaporator heat recovering process without the heat exchanger and supporting refrigerant circuit.
Advantageously, the (optional) introduction and mixing of ambient air flow A2 into the air flow of exhaust air flow A1 enables the heat pump system to recover more heat, in total, from the air flow through the first and second conduits C1, C2 than is available from only the building exhaust air flow A1. Accordingly, the use of ambient air flow A2 enables the heat pump system 100 to supply a larger amount of heat than can be recovered only from the exhaust air flow A1, e.g. a single heat pump system can both recover heat from exhaust air and recover additional heat from ambient air, which may together supply all of the space heating requirements of a building.
The air flow leaving the first evaporator EVP1 would typically have a significantly higher temperature than the ambient air flow A2 (e.g. 5-10° C. higher than ambient), in heating mode, and so raises the temperature of the ambient air when mixed, which increases the heat recovery performance of the second evaporator EVP2. For typical conditions, the present heat pump system may provide a coefficient of performance (COP) that is 20-30% higher than for a conventional air source heat pump.
Conventional air source heat pumps are vulnerable to frosting, in which ice forms on the evaporator, which substantially reduces heat recovery performance and consequently reduces their commercial viability. In conventional air source heat pumps, it is typically necessary to supply significant additional energy (e.g. heating, or running the refrigerant cycle in reverse) to remove any build-up of ice. Advantageously, in the case where the present heat pump system uses ambient air, in addition to exhaust air, the problem of frosting is substantially reduced compared with a conventional air source heat pump, because the air entering the second evaporator EVP2 is warmer than ambient, because of being mixed with the exhaust air flow exiting the first evaporator EVP1. Further, even if the second evaporator EVP2 should become frosted with ice, that ice may be removed by stopping (or reducing) the flow of ambient air flow A2 into the mixing chamber CM, and stopping (or reducing) the flow of refrigerant through the first evaporator EVP1, so that the ice on the second evaporator EVP2 is melted by the heat in the exhaust air flow A1 (e.g. about 20° C. above ambient). Additionally, or alternatively, ice may be removed by increasing the exhaust air flow A1. Similarly, any ice on the first evaporator EVP1 will be melted by passing the exhaust air flow A1 through the first evaporator EVP1 whilst stopping (or reducing) the refrigerant flow through the first evaporator EVP1. Accordingly, the use of exhaust air flow A1 mixed with the ambient air flow A2 can reduce the energy consumption of the heat pump system compared with a conventional air source heat pump, in conditions susceptible to frosting.
The second evaporator EVP2 may have a larger surface area exposed to the air flow than the first evaporator EVP1. Advantageously, the larger surface area may facilitate greater thermal recovery by the second evaporator EVP2, than by the first evaporator EVP1. For example, the volume of ambient air flow A2 may be 300-600% of the volume of exhaust air flow A1 received at the first air inlet IN1 to the first conduit C1.
The heat pump system may be manufactured as a complete system, as shown in
Commonly, existing heat pumps HP are provided on and within a cuboidal housing, commonly with the evaporator mounted on the exterior of the housing H, and an air inlet on a face of the housing, through which air is drawn by an air pump. The heat pump adaptor system 150 has a port PRT that is complementarily shaped for coupling to a heat pump, e.g. having a generally planar port for sealing around the air inlet, or having a port for sealing around the air inlet on two or more external faces of the heat pump HP. For example, the seal may be formed by connecting together fixings that hold a gasket under compression. In use, the mixed air from the mixing chamber CM flows through the second evaporator EVP2 in place of ambient air when the stand-alone heat pump HP is in conventional use.
The heat pump adaptor system 150 is fitted to the heat pump HP by connecting the refrigerant flow path of the heat pump adaptor system 150 with the refrigerant flow path of the heat pump HP, to form an integrated refrigerant flow path (e.g. as shown in
The heat pump system 100 of
In the cooling mode, the refrigerant flows the opposite way through the condenser COND0 (refrigerant-load heat exchanger) of the heating mode, which is operated as an evaporator EVP2′ on the second stream, and absorbs heat (e.g. from within a building) as the thermal load to the heat pump 200′. In the cooling mode, the first evaporator EVP1 (first refrigerant-air heat exchanger) operates as a common subcooler SUBC0′, and the second evaporator EVP2 (second refrigerant-air heat exchanger) of the heating mode operates as a common condenser COND0′, with the refrigerant flowing through the common condenser in the opposite direction to its operation as the second evaporator EVP2.
The heating mode of operation of the heat pump system 200 of
The heat pump system is switched from the heating mode 200 to the cooling mode 200′, by switching all of the three-way valves TV1, TV2, TV3 and four-way valves RV1, RV2, opening the alternative flow paths P1-P4, and closing other flow paths Q1, Q2, Q3 (indicated in
In the cooling mode of operation 200′, the refrigerant flow path forms a closed, streamed refrigerant circuit around which the refrigerant circulates, in use, which is described below, for the refrigerant R-410A, in relation to
In the cooling mode common refrigerant stream:
In the cooling mode first refrigerant stream:
In the cooling mode second refrigerant stream:
As a result of the transfer of heat from the subcooled liquid refrigerant L2sca′ in the cooling mode second refrigerant stream to the binary phase refrigerant B1′ in the cooling mode first refrigerant stream, within the heat exchanger (cooling mode first refrigerant stream-to-second refrigerant stream heat exchanger) HX the refrigerant exiting the first throttle valve TEV1 and entering the cooling mode second stream evaporator EVP2′ has a reduced dryness, leading to more heat absorption by the second stream evaporator EVP2′ and a higher Energy Efficiency Ratio (EER, which is the ratio of the cooling load to the power input).
The mass flow rate through the cooling mode second refrigerant stream (e.g. through the first throttle valve TEV1) may be higher than the mass flow rate through the cooling mode first refrigerant stream (e.g. through the second throttle valve TEV2). The ratio of mass flow rates of the cooling mode first refrigerant stream:second refrigerant stream may be between 0.25:1 and 0.05:1 (e.g. 9%:91%).
The ratio of mass flow rates in the cooling mode first and second refrigerant streams may be controlled in correspondence with the ambient air temperature, the exhaust air temperature, the condensation temperature (e.g. temperature of load water circulating to the cooling mode second stream evaporator EVP2′), and the power of the compressor COMP. The first throttle valve (expansion valve) TEV1 and the second throttle valve (expansion valve) TEV2 may be controlled to regulate the mass flow rates in the cooling mode second and first refrigerant streams, respectively.
The cooling mode first and second refrigerant streams in the heat pump system may be respectively provided with the first temperature sensor TS1 for measuring the temperature of the vapour V1′ output from the heat exchanger HX and flowing to the higher pressure input of the compressor COMP, and the second temperature sensor TS2, for measuring the temperature of the common superheated vapour V0sh′ output from the compressor COMP and flowing to the common condenser COND0′. The first and second temperature sensors TS1, TS2 respectively provide feedback used to control the second throttle valve TEV1 and the second throttle valve TEV2, in particular ensuring that the refrigerant is fully vaporised at the locations of the first temperature sensor TS1.
Examples of a suitable refrigerant for the cooling mode are R-410A and R-134A.
Advantageously, the (optional) introduction and mixing of ambient air flow A2 into the air flow of exhaust air flow A1 enables the heat pump system to absorb more heat, in total, from the air flow through the first and second conduits C1, C2 than is available from only the building exhaust air flow A1. Accordingly, the use of ambient air flow A2 enables the heat pump system 100 to extract a larger amount of heat than can be recovered only from the exhaust air flow A1, e.g. a single heat pump system can both absorb heat from the exhaust air and absorb additional heat from the ambient air, which may together supply all of the space cooling requirements of a building.
Advantageously, in the cooling mode, the exhaust air flow A1 (e.g. 20° C.) has a lower temperature than the ambient air flow A2 (e.g. 35° C.). The degree of subcooling of the refrigerant is increased by the subcooler SUBC0′. For a given the mass flow rate of refrigerant in the cooling mode second stream evaporator EVP2′, this enables more heat to be absorbed in the evaporator EVP2′ than with a conventional heat pump, leading to a higher cooling load and Energy Efficiency Ratio (EER).
The figures provided herein are schematic and not to scale.
Throughout the description and claims of this specification, the words “comprise” and “contain” and variations of them mean “including but not limited to”, and they are not intended to (and do not) exclude other moieties, additives, components, integers or steps.
Throughout the description and claims of this specification, the singular encompasses the plural unless the context otherwise requires. In particular, where the indefinite article is used, the specification is to be understood as contemplating plurality as well as singularity, unless the context requires otherwise.
Features, integers, characteristics, compounds, chemical moieties or groups described in conjunction with a particular aspect, embodiment or example of the invention are to be understood to be applicable to any other aspect, embodiment or example described herein unless incompatible therewith. All of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive. The invention is not restricted to the details of any foregoing embodiments. The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed.
The reader's attention is directed to all papers and documents which are filed concurrently with or previous to this specification in connection with this application and which are open to public inspection with this specification, and the contents of all such papers and documents are incorporated herein by reference.
| Number | Date | Country | Kind |
|---|---|---|---|
| 1916710 | Nov 2019 | GB | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/GB2020/052924 | 11/16/2020 | WO |
| Publishing Document | Publishing Date | Country | Kind |
|---|---|---|---|
| WO2021/094787 | 5/20/2021 | WO | A |
| Number | Name | Date | Kind |
|---|---|---|---|
| 5651258 | Harris | Jul 1997 | A |
| 5899091 | Fraser, Jr. | May 1999 | A |
| 9605883 | Katoh | Mar 2017 | B2 |
| 20070180852 | Sugiura | Aug 2007 | A1 |
| 20130205824 | Morimoto | Aug 2013 | A1 |
| 20190154322 | Ito | May 2019 | A1 |
| 20210039474 | Kim | Feb 2021 | A1 |
| Number | Date | Country |
|---|---|---|
| 109737641 | May 2019 | CN |
| 110168288 | Aug 2019 | CN |
| WO2013140918 | Sep 2013 | JP |
| WO 2018198609 | Nov 2018 | JP |
| Entry |
|---|
| State IP Office First Review Opinion Notice; Dated Mar. 12, 2024. |
| Number | Date | Country | |
|---|---|---|---|
| 20220404073 A1 | Dec 2022 | US |
