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CN-122015336-A - Heat pump system

CN122015336ACN 122015336 ACN122015336 ACN 122015336ACN-122015336-A

Abstract

A heat pump system for controlling the temperature inside a building. The system includes a compressor, a first heat exchanger, an expansion device, and a second heat exchanger fluidly connected together by a refrigerant flow to define a refrigerant circuit, and a thermal energy storage device thermally connectable to the refrigerant circuit to exchange thermal energy with the refrigerant. The heat pump system is configured to operate in a normal heating mode, a defrost mode, and/or an auxiliary heating mode. The heat pump system includes a switching assembly configured to switch between a normal heating mode, a defrost mode, and/or an auxiliary heating mode, and the switching assembly is configured to direct refrigerant exiting the first heat exchanger to flow through the second heat exchanger when the heat pump system is operated in the defrost mode, causing excess heat in the refrigerant to defrost the second heat exchanger.

Inventors

  • YU ZHIBIN

Assignees

  • 格拉斯哥大学校董会

Dates

Publication Date
20260512
Application Date
20210929
Priority Date
20200930

Claims (19)

  1. 1. A heat pump system for controlling the temperature inside a building, the system comprising: A compressor, a first heat exchanger, an expansion device, and a second heat exchanger fluidly connected together by a refrigerant flow to define a refrigerant circuit, and a thermal energy storage device thermally connectable to the refrigerant circuit to exchange thermal energy with the refrigerant flow; Wherein the heat pump system is configured to be operable in a normal heating mode, a defrost mode and/or an auxiliary heating mode, wherein: In a normal heating mode, heat energy is transferred from the second heat exchanger into the refrigerant flow and from the refrigerant flow through the first heat exchanger to heat a building, In defrost mode, thermal energy is transferred from the thermal energy storage device into the refrigerant flow and from the refrigerant flow through the first heat exchanger to heat a building, from the refrigerant flow through the second heat exchanger to defrost the second heat exchanger, In an auxiliary heating mode, thermal energy is transferred from the thermal energy storage device into the refrigerant flow and from the refrigerant flow through the first heat exchanger to heat a building; Wherein the heat pump system comprises a switching assembly configured to switch between a normal heating mode, a defrost mode and/or an auxiliary heating mode, and the switching assembly is configured to direct refrigerant exiting the first heat exchanger to flow through the second heat exchanger when the heat pump system is operated in defrost mode, defrost the second heat exchanger with waste heat in the refrigerant, and the switching assembly is configured to bypass the expansion device and the second heat exchanger when the heat pump system is operated in the auxiliary heating mode.
  2. 2. The heat pump system of claim 1, wherein the switching assembly is configured to direct refrigerant exiting the first heat exchanger through the second heat exchanger, the expansion device, and the compressor in that order when the heat pump system is operated in a defrost mode.
  3. 3. A heat pump system according to claim 1 or claim 2, wherein the thermal energy storage device is connected to the refrigerant circuit between the expansion device and the compressor.
  4. 4. A heat pump system according to claim 2 or claim 3, wherein the switching assembly comprises a four-way valve configured to directly connect the first heat exchanger to the second heat exchanger when the heat pump system is operated in defrost mode.
  5. 5. The heat pump system of claim 1, wherein the switching assembly is configured to bypass the expansion device and direct refrigerant exiting the first heat exchanger through a second expansion device, the thermal energy storage device, the second heat exchanger, and the compressor in that order when the heat pump system is operated in a defrost mode.
  6. 6. The heat pump system of claim 5, wherein the switching assembly comprises a first bypass assembly configured to isolate the expansion device from the refrigerant circuit when the heat pump system is operated in a defrost mode.
  7. 7. A heat pump system according to claim 5 or claim 6, wherein the thermal energy storage device is connected to the refrigerant circuit between the second expansion device and the second heat exchanger.
  8. 8. The heat pump system of claim 7, wherein the switching assembly comprises a second bypass assembly configured to fluidly connect the second expansion device to the refrigerant circuit between the first heat exchanger and the thermal energy storage device when the heat pump system is operated in a defrost mode.
  9. 9. The heat pump system of any of claims 5-8, wherein the heat pump system is operable in a charging mode in which thermal energy is transferred from the refrigerant to the thermal energy storage device, wherein the switching assembly is configured to direct refrigerant exiting the compressor to bypass the second expansion device and the first heat exchanger when the heat pump system is operated in the charging mode.
  10. 10. A heat pump system according to any preceding claim, wherein the thermal energy storage means comprises a phase change material.
  11. 11. The heat pump system of claim 10, wherein the phase change material is configured to be in direct thermal contact with a conduit of the refrigerant circuit.
  12. 12. The heat pump system of claim 10, wherein the phase change material is thermally connected to a conduit of the refrigerant circuit by a circuit comprising a heat transfer fluid.
  13. 13. The heat pump system according to any one of the preceding claims, wherein the refrigerant circuit comprises a high pressure stage and a low pressure stage, the high pressure stage and low pressure stage being fluidly connected together by a phase separator, wherein the high pressure stage comprises the first heat exchanger and the low pressure stage comprises the second heat exchanger.
  14. 14. The heat pump system of claim 13, wherein the thermal energy storage device is thermally connectable to the phase separator.
  15. 15. The heat pump system of claim 13 or claim 14, wherein the compressor defines a compressor assembly comprising a first compressor fluidly connected to the high pressure stage and a second compressor fluidly connected to the low pressure stage.
  16. 16. A heat pump system according to claim 13 or claim 14, wherein the compressor comprises a vapor injection compressor fluidly connected to the high pressure and low pressure stages of the refrigerant circuit.
  17. 17. The heat pump system of any of claims 13-16, wherein the expansion device defines an expansion device assembly comprising a first expansion device fluidly connected to the high pressure stage and a second expansion device fluidly connected to the low pressure stage.
  18. 18. The heat pump system of claim 17, wherein the switching assembly is configured to bypass the first expansion device and direct refrigerant exiting the first heat exchanger through a second expansion device, the second heat exchanger, and the phase separator in that order when the heat pump system is operated in defrost mode.
  19. 19. A building comprising the heat pump system of any one of claims 1 to 18, wherein the second heat exchanger is thermally connected to a second heat source, and wherein the first heat exchanger is thermally connected to a central heating system of the building.

Description

Heat pump system Technical Field The present invention relates to a heat pump system and a method of operating a heat pump system. Background It is known to provide heat pumps to extract thermal energy (i.e. heat) from a heat source (e.g. ambient external air) and then release the extracted thermal energy to the interior of an enclosed space such as a building. Any heat source having a temperature above absolute zero contains some thermal energy that can be used to raise the internal temperature of the enclosure. One known example of a heat pump system is an Air Source Heat Pump (ASHP), which generally includes an evaporator, a compressor, a condenser, and an expansion device. ASHP are fluidly connected by fluid conduits to form a refrigerant circuit. The evaporator and the condenser each include a heat exchanger configured to allow heat to be transferred into and/or out of the refrigerant flowing through the refrigerant circuit. The evaporator is arranged in an external position such that it can transfer heat from the surrounding outside air, while the condenser is typically connected to the central heating system of the building. The refrigeration circuit begins with a compressor and the vaporized refrigerant is compressed to form hot vapor. The hot refrigerant vapor is then directed to a condenser, which transfers some heat from the refrigerant, thereby condensing the vapor into a liquid. The liquid refrigerant then flows to an expansion valve where expansion occurs, thereby reducing the pressure and temperature. The cold refrigerant mixture is directed through an evaporator, which then transfers heat from the outside air, causing the refrigerant to evaporate. The refrigerant vapor is then directed back to the compressor to restart the refrigerant circuit. A known problem with ASHP is that the heat capacity and coefficient of performance (COP) drop dramatically as the ambient outside air temperature drops. This means that the performance of ASHP will drop to a minimum when the inflow of heat is most needed to raise the internal temperature of the building. Another problem with known ASHP is that when the external temperature drops below about 6 ℃, frost and ice may form on the coils or fins of the evaporator. Icing can reduce the operating efficiency of the evaporator, thereby causing ASHP to cease operation. It is necessary to defrost the evaporator periodically to prevent icing, especially in cold and humid climates. A typical method of defrosting an evaporator involves reversing the flow direction of the refrigerant through the circuit, directing the refrigerant from the compressor to the evaporator. This so-called "reverse circulation method" is performed by configuring ASHP to extract heat from the condenser to melt ice accumulated in the evaporator. An alternative approach is to provide a bypass conduit or passage for the refrigerant circuit that is configured to fluidly connect the output of the compressor to the input of the evaporator while bypassing the condenser. In this "hot gas bypass method" the compressor is configured to produce hot vaporized refrigerant that is then directed to the evaporator to melt ice formed thereon. Another alternative defrost method uses a separate electric heater configured to directly heat the external surface of the evaporator to melt frost and ice that accumulate under cold and humid conditions. This defrosting method uses additional power and also requires ASHP devices to be turned off during defrosting, which can result in a disruption of the heating of the building interior. During defrosting operation, each of these defrosting methods consumes electric power without providing heat to the interior of the building. For example, in the hot gas bypass method, the compressor is operated to provide hot refrigerant vapor, but no heat is provided to the central heating system of the building because the hot vapor is transferred from the condenser. Or reverse circulation, causes cold refrigerant to flow through the condenser on its way to the evaporator. This results in heat extraction from the condenser, thereby lowering the temperature inside the building. These defrost methods all require the provision of a backup heat source, such as an electric heater or a gas boiler, during operation to defrost the evaporator while simultaneously heating the building interior. Therefore, each defrosting method significantly reduces the overall coefficient of performance (COP) of the heat pump system. The present disclosure is directed to solving one or more of the above-described problems of existing heat pump systems. Disclosure of Invention In its broadest sense, aspects of the present invention provide a heat pump system configured to direct residual thermal energy from a condenser to an evaporator for defrosting while also directing stored thermal energy from a thermal energy storage device to the condenser for heating the interior of a building during defrosting operation.