GB2488331A - Heat pump system with a thermal store comprising a phase change material - Google Patents

Heat pump system with a thermal store comprising a phase change material Download PDF

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Publication number
GB2488331A
GB2488331A GB1103071.5A GB201103071A GB2488331A GB 2488331 A GB2488331 A GB 2488331A GB 201103071 A GB201103071 A GB 201103071A GB 2488331 A GB2488331 A GB 2488331A
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GB
United Kingdom
Prior art keywords
heat
heat pump
target fluid
thermal store
heated
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
GB1103071.5A
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GB201103071D0 (en
Inventor
Stephen Forbes Pearson
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Star Refrigeration Ltd
Original Assignee
Star Refrigeration Ltd
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Filing date
Publication date
Application filed by Star Refrigeration Ltd filed Critical Star Refrigeration Ltd
Priority to GB1103071.5A priority Critical patent/GB2488331A/en
Publication of GB201103071D0 publication Critical patent/GB201103071D0/en
Publication of GB2488331A publication Critical patent/GB2488331A/en
Withdrawn legal-status Critical Current

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Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F24—HEATING; RANGES; VENTILATING
    • F24H—FLUID HEATERS, e.g. WATER OR AIR HEATERS, HAVING HEAT-GENERATING MEANS, e.g. HEAT PUMPS, IN GENERAL
    • F24H4/00—Fluid heaters characterised by the use of heat pumps
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F24—HEATING; RANGES; VENTILATING
    • F24H—FLUID HEATERS, e.g. WATER OR AIR HEATERS, HAVING HEAT-GENERATING MEANS, e.g. HEAT PUMPS, IN GENERAL
    • F24H4/00—Fluid heaters characterised by the use of heat pumps
    • F24H4/02—Water heaters
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F24—HEATING; RANGES; VENTILATING
    • F24H—FLUID HEATERS, e.g. WATER OR AIR HEATERS, HAVING HEAT-GENERATING MEANS, e.g. HEAT PUMPS, IN GENERAL
    • F24H7/00—Storage heaters, i.e. heaters in which the energy is stored as heat in masses for subsequent release
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B13/00—Compression machines, plants or systems, with reversible cycle
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B30/00—Heat pumps
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B30/00—Heat pumps
    • F25B30/06—Heat pumps characterised by the source of low potential heat
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B47/00—Arrangements for preventing or removing deposits or corrosion, not provided for in another subclass
    • F25B47/02—Defrosting cycles
    • F25B47/022—Defrosting cycles hot gas defrosting
    • F25B47/025—Defrosting cycles hot gas defrosting by reversing the cycle

Abstract

A heat pump system 10 comprises a heat pump 12 having an evaporator 22 to be arranged in heat exchange with a heat source 16 and a condenser 24 to be arranged in heat exchange with a target fluid. The heat pump is configurable between a heating mode of operation, in which heat is transferred from the heat source to heat the target fluid, and a defrosting mode of operation, in which heat is transferred from the target fluid to heat the evaporator to remove frost formed on it. The heat pump system further comprises a thermal store 34 which includes a phase change material 36 configured to be heated when the heat pump is in a heating mode of operation. When the heat pump is switched to a defrosting mode of operation, heat is transferred from the target fluid to heat the evaporator, and the thermal store provides heat to re-heat the target fluid. In a further aspect, an air source heat pump utilising a reversed cycle defrosting system to defrost an air cooler is disclosed, where a thermal store is used to re-heat flowing water cooled as a result of the reversed cycle defrost.

Description

HEAT PUMP SYSTEM
HELD OF THE INVENTION
The present invention r&ates to a heat pump system, and in particular to an air source heat pump system including a defrosting system.
BACKGROUND TO THE INVENTION
A typical heat pump operates by permitting a working fluid, such as a refrigerant, to vaporise in an evaporator thus absorbing heat from a heat source, wherein the vaporised working fluid is compressed and dehvered as hot vapour to a condenser where it is condensed, thus releasing heat at a target location. Foowing this the condensed working fluid is passed through an expansion valve and dehvered at reduced pressure to the evaporator for the heat pump and thermodynamic cycle to be repeated. In this way, heat may be transferred from the heat source to the target location to be used in, for example, space heating, water heating; providing heat to a process or the ike. The available heat produced at the target location is in a quantity that equals the heat absorbed from the heat source plus the energy required to drive the compressor, and although the energy required to drive the compressor may be significantly less than the energy released from the condensing working fluid, it is stifi recognised that this energy driving the compressor is high grade energy. It is therefore desirable to maximise the efficiency and use of such high grade energy in any heat pump design.
Many sources of heat may be used by existing heat pump designs. For example, ground source heat pumps are arranged such that the evaporator is embedded within the earth, which may involve complex installation! and may be difficult to achieve retrofit, although in such ground source heat pump designs the source temperature vanation, for example between different seasons of the year, is relatively small As such, a fairly consistent heat output may be achieved without requiring significant fluctuations in energy input.
Air-source heat pumps are also known, in which the evaporator component of the heat pump is provided as an air cooler and arranged in heat exchange with ambient S air. However, one disadvantage with such air-source heat pumps is that both the capacity and efficiency of the heat pump fafi as the ambient temperature reduces. A further disadvantage is that as the ambient temperature fafis towards 0C, frost may forni on the air cooler thus restricting flow of air therethrough. The heat pump wifi cease to function when the air cooler becomes blocked, and in order to keep the heat pump functioning even at ambient temperatures below Ot it is necessary to provide some form of defrosting of the air cooler.
A form of defrosting known as reversed cycle defrosting is known in the art, in which the flow of hot working fluid norrnaHy sent to the condenser is instead sent to the evaporator (air cooler) where it condenses and provides large quantities of heat thus raising the evaporator to temperatures at which frost is rapidly melted. Thus, during reverse cycle defrosting the evaporator temporarily functions as the condenser, and as such the condenser at the target heating location temporarily functions as the evaporator, which will have the undesirable effect of cooling the target location.
SUMMARY OF THE INVENTION
According to a first aspect of the present invention there is provided a heat pump system, comprising: a heat pump having an evaporator to be arranged in heat exchange with a heat source and a condenser to be arranged in heat exchange with a target fluid, wherein the heat pump is configurable between a heating mode of operation in which heat is transferred from the heat source to heat the target fluid, and a defrosting mode of operation in which heat is transferred from the target fluid to heat the evaporator to remove frost formed thereon; and a thermal store comprising a phase change material configured to be heated when said heat pump is in a heating mode of operation, and to heat the target fluid when the heat pump is in a defrosting mode of operation.
The phase change material may be configured to be transitioned between different phases during the heating and defrosting modes of operation of the heat pump.
Heat source conditions approaching and falling b&ow Ut may cause a build up of frost on the evaporator, which in accordance with the present invention may be addressed by operation of the heat pump in the defrosting mode of operation.
During the defrosting mode of operation, heat is transferred from the target fluid which will have the effect of cooling said fluid, In accordance with the present invention the target fluid is heated, for example re-heated, by the thermal store, thus minimising or offsetting cooling of the target fluid during defrosting of the evaporator.
The present invention may assist to provide or maintain a substantially consistent output temperature of the target fluid, irrespective of operational mode of the heat pump.
The target fluid may comprise water, air, or the like.
The heat source may comprise air, such that the heat pump may define an air source heat pump. In such an air-source heat pump the evaporator may define an air cooler.
The heat pump may comprise a working fluid configured to be communicated between the evaporator and condenser to transfer heat therebetween. The heat pump 26 may comprise a compressor configured to compress the working fluid to establish pressure and temperature conditions suitable to achieve condensing within the condenser The heat pump may comprise a pressure reducing arrangement, such as an expansion valve, configured to permit a reduction in pressure of the working fluid to establish pressure and temperature conditions suitable to achieve evaporation within the evaporator.
During the heating mode of operation a working fluid may be vaporised within the evaporator, thus absorbing heat from the heat source, and delivered to the condenser to transfer the absorbed heat to the target fluid, The vaporised working fluid from the evaporator may be compressed and delivered to the condenser as vaporised fluid at a high temperature and pressure which is condensed within the condenser to heat the target fluid. Condensed working fluid from the condenser may be reduced in pressure and returned to the evaporator.
The heat pump system may be configured to communicate the target fluid, for example heated target fluid, to the evaporator while the heat pump is configured in the defrosting mode of operation. As such, the target fluid may be used to defrost the evaporator, which may result in a drop in temperature of the target fluid.
The heat pump system may be configured to reverse flow of working fluid within the heat pump to establish the defrosting mode of operation. Such an arrangement may be defined as reversed cycle defrosting and comprise evaporating working fluid within the condenser by absorbing heat from the target fluid, and delivering said vaporised working fluid to the evaporator to condense therein to provide a desired defrosting effect, Thus, during a defrosting cycle the condenser may temporarily function as an evaporator, and the evaporator may temporarily function as a condenser. The vaporised working fluid may be compressed prior to being delivered to the evaporator. The working fluid condensed within the evaporator may be subsequenUy expanded.
The working fluid may be diverted using a valve, such as a reversing valve, to reconfigure the heat pump between the heating and defrosting modes of operation.
The thermal store may be heated by the heat pump during the heating mode of operation. Such heating may be configured to charge the thermal store with heat energy which is released to heat the target fluid during a defrosting mode of operation of the heat pump.
During the heating mode of operation the phase change material is configured to undergo an endotherrnic process and be transitioned into a state of higher enthalpy, absorbing latent heat. The phase change material may be configured to be transitioned from a sofld state to a liquid state during the heating mode of operation.
The phase change material may be configured to be transitioned from a Uquid state to a gaseous state during the heating mode of operation. The phase change material may be configured to be transitioned from a solid state, to a quid state and then to a gaseous state during the heating mode of operation.
During the defrosting mode of operation the phase change material is configured to undergo an exotherrnic process and be transitioned into a state of lower enthalpy, releasing latent heat. This effect may therefore permit the thermal store to release both sensible and latent heat for use in heating the target fluid, The phase change material may be configured to be transitioned from a liquid state to a solid state during the defrosting mode of operation. The phase change material may be configured to be transitioned from a gaseous state to a liquid state during the defrosting mode of operation. The phase change material may be configured to be transitioned from a gaseous state, to a liquid state and then to a solid state during the defrosting mode of operation.
The phase change material may be configured or selected in accordance with operational conditions, such as desired or user defined operational conditions? of the heat pump system. The phase change material may be configured or selected to undergo a phase transition at a temperature higher than a desired heated temperature of the target fluid. For example, the phase change material may be configured or selected to melt at a temperature higher than a desired heated temperature of the target fluid.
The phase change material may be configured to undergo a phase transition at a temperature which is lower than an operational temperature of the heat pump, for example lower than the temperature of a working fluid within the heat pump. For example, the phase change material may be configured or selected to melt at a temperature which is lower than an operational temperature of the heat pump.
The phase change material may comprise a single compound. The phase change material may comprise a mixture or blend of compounds. The phase change material may comprise an organic compound. The phase change material may comprise a wax material, The phase change material may comprise an acid, such as a fatty acid. The phase change material may comprise, for example, Stearic acid, Palmitic acid or the ke.
The thermal store may be heated by heat exchange with the target fluid.
The thermal store may be heated by heat exchange with one or more components of the heat pump. The thermal store may be heated by heat exchange with a working fluid within the heat pump. The thermal store may be heated by heat exchange with a working fluid following evaporation of the working fluid within the evaporator of the heat pump. The thermal store may be heated by heat exchange with a working fluid following compression of the working fluid by a compressor within the heat pump.
The thermal store may be heated by heat exchange with a working fluid within the condenser of the heat pump. In such an arrangement the working fluid within the condenser may heat both the target fluid and the thermal store.
The thermal store may be heated by heat exchange with a working fluid upstream of the condenser of the heat pump. Accordingly, the working fluid may heat the thermal store prior to heating the target fluid, The thermal store may be heated by the working fluid at a temperature higher, for example considerably higher, than the saturation temperature of the working fluid, In this way, condensing of the working fluid may be substantially avoided when used to heat the thermal store, permitting the working fluid to proceed to condense withfri the condenser and appropriately heat the target fluid, In such an arrangement the working fluid may be capable of heating the thermal store to a greater temperature than the target fluid in heat exchange with the compressor. This may therefore permit the thermal store to achieve a sufficient enthalpy to appropriately heat the target fluid to a target temperature during a defrosting mode of operation of the heat pump. The heat pump may comprise a de superheater, and the thermal store may be heated by heat exchange with said de superheater.
The thermal store may be heated by direct heat exchange with one or more components of the heat pump. For example, the thermal store may be provided or associated with a heat exchanger in operational cooperation with the heat pump.
The thermal store may be heated by indirect heat exchange with one or more components of the heat pump. For example, the thermal store may be heated by an intermediate heat exchange fluid which is communicated between one or more components of the heat pump and the thermal store. That is, the intermediate heat exchange fluid may be first heated by one or more components of the heat pump, and then used to heat the thermal store. The intermediate heat exchange fluid may comprise the target fluid. In some embodiments the target fluid may be communicated through a flow path which permits the target fluid to be arranged in heat exchange with one or more components of the heat pump and the thermal store.
The heat pump system may comprise a target fluid flow circuit defining a cold inlet and a hot outiet, wherein target fluid to be heated is received via the cold inlet, and heated target fluid is delivered via the hot outlet. Heated target fluid delivered from the hot outlet may be consumed. Heated target fluid delivered from the hot outlet may be utilised in a process such as a space heating process, and then returned for reheating via the cold inlet.
The target fluid flow circuit may he configured to establish heat exchange between the target fluid and the condenser of the heat pump. Such heat exchange may occur during both the heating and defrosting mode of operation of the heat pump.
In this way the target fluid is heated during the heating mode of operation, and is cooled during the defrosting mode of operation (that is, during defrosting the target fluid functions as a heat source).
When the heat pump is operating in the defrosting mode of operation the target fluid flow circuit may be configured to establish heat exchange between the target fluid which has been cooled by the condenser and the thermal store which has been heated during a previous heating mode of operation of the heat pump. Establishing such heat exchange between cooled target fluid and the thermal store may be selective. Such selective heat exchange may be provided by a diverting arrangement, such as a diverting valve, The target fluid flow circuit may comprise a loop portion which is configured to permit at least a portion of the target fluid to be delivered between the heat pump, such as a desuperheater component of the heat pump, and the thermal store, during the heating mode of operation of the heat pump. In this way the target fluid may function as an intermediate heat exchange fluid permitting the thermal store to be heated by the heat pump during the heating mode of operation.
The thermal store may comprise a plate heat exchanger.
The thermal store may not only be configured for use when the heat pump is operated in a defrosting mode. In some embodiments the thermal store may be used to provide additional heating to the target fluid, for example where a large demand for hot target fluid, or an increase in temperature is required within a short space of time.
According to a second aspect of the present invention there is provided a method of operating a heat pump system, comprising: arranging an evaporator of a heat pump in heat exchange with a heat Source; and arranging a condenser of the heat pump in heat exchange with a target fluid; establishing a heating mode of operation in which heat is transferred from the heat source to heat the target fluid, and heating a thermal store comprising a phase change material: and then establishing a defrosting mode of operation in which heat is transferred from the target fluid to heat the evaporator, and the thermal store provides heat to reheat the target fluid.
The defrosting mode of operation may be established by reversing the flow of a The thermal store may be heated by the heat pump during the heating mode of operation.
Features and aspects of operating the heat pump system defined in accordance with the first aspect may be applied to the second aspect.
According to a third aspect of the present invention there is provided a heat pump defrosting system comprising a thermal store including a phase change material configured to be heated during a heating mode of operation of an associated heat pump; and to heat a target fluid during a defrosting operation of the heat pump.
Features associated with the heat pump system defined in accordance with the first aspect may be applied to the third aspect.
According to a fourth aspect of the present invention there is provided a heat pump system using air as the heat source where a reversed cycle defrosting system is used to defrost an air cooler and where a thermal store containing a phase change material is used to reheat flowing water that had been cooled as a result of the reversed cycle defrost.
According to a fifth aspect of the present invention there is provided a heat pump system compri&ng: a heat pump having an evaporator to be arranged in heat exchange wh a heat source and a condenser to be arranged in heat exchange with a target fluid, wherein S the heat pump is operational in a heating mode of operation in which heat is transferred from the heat source to heat the target fluid; and a thermal store comprising a phase change material configured to further heat the target fluid, in use, the thermal store may be available to provide boost heat to the target fluid when demand requires.
The thermal store may be heated by the heat pump when further heating of the target fluid by the thermal store is not required. Accordingly, the heat pump may be used to charge the thermal store.
According to a sixth aspect of the present invenUon there is provided a heat pump system, comprising: a heat pump having an evaporator to be arranged in heat exchange with a heat source and a condenser to be arranged in heat exchange with a target fluid, wherein the heat pump is configurable between a heating mode of operation in which heat is transferred from the heat source to heat the target fluid, and a defrosting mode of operation in which heat is transferred from the target fluid to heat the evaporator to remove frost formed thereon; and a thermal store material fluidly isolated from the target fluid and configured to be heated when said heat pump is in a heating mode of operation, and to heat the target fluid when the heat pump is in a defrosting mode of operation.
The thermal store material by being fluidly isolated from the target fluid therefore prevents any mixing of the target fluid and the thermal store material.
Another aspect of the invention relates to a heat pump system, comprising: a heat pump having an evaporator to be arranged in heat exchange with a heat source and a condenser to be arranged in heat exchange with a target fluid, wherein the heat pump is configurable between a heating mode of operation in which heat is transferred from the heat source to heat the target fluid, and a defrosting mode of operation in which heat is transferred from the target fluid to heat the evaporator to remove frost formed thereon; and a thermal store configured to be heated when said heat pump is in a heating mode of operation, and to heat the target fluid when the heat pump is in a defrosting mode of operation.
BRIEF DESCRIPTION OF THE DRAWINGS
These and other aspects of the present invention wifi now be described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 is a schematic illustration of a heat pump system in accordance with an embodiment of the present invention, configured to operate in a heating mode; and Figure 2 is a schematic illustration of the heat pump system of Figure 1, configured to operate in a defrosting mode.
DETAILED DESCRIPTION OF THE DRAWINGS
A heat pump system. generally identified by reference numeral 10, in accordance with an embodiment of the present invention is schematicay illustrated in Figures 1 and 2, where Figure 1 illustrates the system 10 operating in a heating mode, and Figure 2 illustrates the system operating in a defrosting mode. The system 10 is composed of an air-source heat pump, generally identified by reference numeral 12, and a water circuit, generally identified by reference numeral 14. The heat pump 12 utilises ambient air 16 as a heat source and functions to heat water flowing within the water circuit 14 to a desired output temperature. In this respect the water circuit 14 defines a cold inlet 16 for receiving water to be heated, and a hot outlet 20 for devering heated water. In some embodiments the heated water may be consumed, for example as domestic hot water. In other embodiments, as illustrated, the heated water is utflised in a process, such as a space heating process, and returned to the cold inlet 18 for reheating.
The heat pump 12 comprises an evaporator 22 which is arranged in heat transfer with ambient air 16, and a condenser 24 arranged in heat transfer with the water flowing within the water circuit 14. The heat pump 12 further comprises a compressor 28, expansion valve 28, a four port reversing valve 30 and a de superheater 32.
During a heating mode of operation the fourport reversing valve 30 is configured as shown in Figure 1 such that a vaporised working fluid (refrigerant) from the evaporator is compressed by the compressor 26 and delivered to the condenser 24, via the desuperheater 32, at a pressure which permits condensing of the working fluid to achieve heating of the water flowing within the water circuit 14. The water may be heated to a desired output temperature, which may be assisted by use of appropriate thermostatic controls (not shown). The condensed working fluid is then passed through the expansion valve 28 to be reduced in pressure and temperature to the evaporating temperature, and then passed through the evaporator where the working fluid is evaporated and absorbs heat from the ambient air 1$. Cyclical operation of the heat pump 12 in this manner may permit continuous heating of the water within the water circuit 14.
However, in circumstances where the ambient air 16 fafls close to or below Ct frost may form on the evaporator 22, which can adversely affect the functionality of the heat pump 12, and in severe cases of frost the heat pump 12 may cease to operate. In order to address any frost formation the heat pump 12 may be configured to operate in a defrosting mode in which the fouNport reversing valve 30 is configured as shown in Figure 2. In this configuration hot pressurised vapour from the compressor 26 is diverted to the evaporator 22 where it is condensed thus warming the evaporator 22 and melting the frost. The condensed working fluid is then reduced in pressure within the expansion valve 28 and deUvered to the condenser 24 where the working fluid is evaporated by absorbing heat from the water flowing through the water circuit 14. This process is known as reverse cycle defrosting, and aRhough this effectively removes frost from the evaporator 22, it utihses the water within the circuit 14 as a heat source, thus causing the water to become cooled, which is undesirable. As wifi be described in deta below, the present invention permits such cooling of the water to be offset by use of a thermal store 34 which is heated or charged via the de-superheater 32 during heating operation of the heat pump 12, and provides heat to the water during defrosting operation of the heat pump 12.
During a heating mode of operation the water flowing within the water circuit 14 is heated within the condenser 24 and is then delivered to the hot outlet 20 via a three-port changeover valve 39 configured as shown in Figure 1. The water circuit comprises a thermal store charging loop 14a which, during a heating mode of operation, draws a portion of the heated water from the condenser via pump 40 to be passed through the S-superheater 32. In this respect the working fluid within the 5-superheater 32 is at a temperature considerably higher than the saturation temperature of the working fluid, and is thus capable of further increasing the temperature of the water within the charging loop 14a. The water heated within the de-superheater 32 passes through ba valve 42 configured as shown in Figure 1 to flow through and heat the thermal store 34. In this respect the thermal store 34 comprises a phase change material 3$ within a plate heat exchanger 38, and during heating by hot water supplied via the charging loop 14a the phase change material 3$ transitions into a state of higher enthalpy, absorbing latent heat. For example, the phase change material 36 may transition from a solid state to a liquid state during heating. The water used to heat the thermal store 34 is then commingled with the water from the condenser 24 and deHvered from the hot ouflet 20 for appropriate use. As the water within the charging loop 14a is heated to a greater temperature than the water from the condenser 24, it is possible to heat the thermal store 34 to a temperature greater than the desired output water temperature from the water circuit 14. As such, the thermal store may be appropriately charged with sufficient energy to heat water, when required, to achieve the desired outlet temperature.
During a defrosting mode of operation, in which the water is cooled within the condenser 24, the water circuit 14 is reconfigured to permit the cooled water to pass through the charged thermal store 34 for reheating. Specifically, the charging loop 14a is closed using ball valve 42; and a reheating loop 14b is opened via the thre&port vaWe 39 to permit the cooled water from the condenser 24 to be passed:through the thermal store heat exchanger 38 for reheating. During such reheating the phase change material 36 transitions into a state of lower enthalpy, releasing latent heat. For example, the phase change material may be configured to be transitioned from a liquid state to a solid state during the defrosting mode of operation. The reheated water may then be flowed to be deRvered from the hot outlet 20 at a desired temperature.
The phase change material may be configured or selected in accordance with desired operational conditions; such as desired or user defined operational conditions.
In a preferred exemplary operation; the phase change material may be configured or selected to undergo a phase transition at a temperature higher than a desired heated temperature of the target fluid. For example, the phase change material may be configured or selected to melt at a temperature higher than a desired heated temperature of the target fluid. Further, the phase change material may be configured to undergo a phase transition at a temperature which is lower than an operational temperature of the heat pump, for example lower than the temperature of a working fluid within the heat pump. For example, the phase change material may be configured or s&ected to melt at a temperature which is lower than an operational temperature of the heat pump.
In one exemplary embothment the operational conditions of the heat pump system 10 may requfre a water output temperature in the region of, for example, 35°C to 55°C, and the discharge temperature of refrigerant from the compressor 26 may be controed to be within the region of 100°C.
In an exemplary embodiment the phase change material may comprise Stearic acid, which has a melting point of 696°C and a latent heat of fusion of 198.91 kJ/kg.
another exemplary embodiment the phase change material may comprise Palmitic acid, which has a melting point of 62.9°C and a latent heat of fusion of 16393 kJ/kg. In another exemplary embodiment a mixture of phase change materials may be used, such as a mixture of Stearic acid and PalmiUc acid. Such a mixture may permit a blend to be created which has a desired melting point.
The use of a phase change material within the thermal store may permit a sufficient heating effect to be achieved while maintaining a relatively compact arrangement.
It should be understood that the embodiments and possible variations identified above are merely exemplary and that various or further modifications may be made thereto without departing from the scope of the invention. For example, in some cases a portion of the water within water circuit 14 may be diverted to defrost the evaporator and returned to the thermal store 34 for reheating, Further, alternative phase change materials may be selected other than those identified above. Also, the heat pump system is not restricted only as an aifrsource heat pump system, Also, the present invention may not solely be utilised where defrosting is required, and instead the thermal store may be used to provide additional heating to the water. for example during a period of increased demand for hot water, or when an increase in temperature is required within a short space of time,

Claims (29)

  1. CLAIMS: I. A heat pump system, comprising; a heat pump having an evaporator to be arranged in heat exchange with a heat source and a condenser to be arranged in heat exchange with a target fluid, wherein the heat pump is configurable between a heating mode of operation in which heat is transferred from the heat source to heat the target fluid, and a defrosting mode of operation in which heat is transferred from the target fluid to heat the evaporator to remove frost formed thereon; and a therma store configured to be heated when said heat pump is in a heating mode of operation, and to heat the target fluid when the heat pump is in a defrosting mode of operation, wherein the thermal store comprises a phase change material configured to be transitioned between different phases during the heating and defrosting modes of operation of the heat pump.
  2. 2. The system according to claim 1, wherein the heat source comprises air.
  3. 3. The system according to daim I or 2, wherein the heat pump comprises a working fluid configured to be communicated between the evaporator and condenser to transfer heat therebetween.
  4. 4. The system according to any preceding daim, configured to reverse flow of a working fluid within the heat pump to establish the defrosting mode of operation.
  5. 5 The system according to any preceding claim, wherein the thermal store is heated by the heat pump during the heating mode of operation.
  6. 6. The system according to any preceding claim, wherein during the heating mode of operation the phase change material is configured to transition into a state of higher enthalpy, absorbing latent heat.
  7. 7, The system according to any preceding claim, wherein during the defrosting mode of operation the phase change material is configured to transition into a state of lower enthalpy, releasing latent heat.
  8. 8. The system according to any preceding claim, wherein the phase change material is configured or selected to undergo a phase transition at a temperature higher than a desired heated temperature of the target fluid.
  9. 9. The system according to any preceding claim, wherein the phase change material is configured to undergo a phase transition at a temperature which is lower than an operational temperature of the heat pump! for example lower than the temperature of a working fluid within the heat pump.
  10. 10. The system according to any preceding claim, wherein the thermal store is heated by heat exchange with one or more components of the heat pump.
  11. 11. The system according to any preceding claim, wherein the thermal store is heated by heat exchange with a working fluid within the heat pump.
  12. 12. The system according to any preceding claim, wherein the thermal store is heated by heat exchange with a working fluid at a location downstream of a compressor within the heat pump, and upstream of the condenser of the heat pump.
  13. 13. The system according to any preceding daim, wherein the thermal store is heated by a working fluid within the heat pump at a temperature higher than the saturation temperature of the working fluid.
  14. 14. The system according to any preceding claim, wherein the thermal store is heated by direct heat exchange with one or more components of the heat pump.
  15. 15. The system according to any preceding claim, wherein the thermal store is heated by indirect heat exchange with one or more components of the heat pump.
  16. 16. The system according to claim 15, wherein the thermal store is heated by an intermediate heat exchange fluid which is communicated between one or more components of the heat pump and the thermal store,
  17. 17. The system according to claim 16, wherein the intermediate heat exchange fluid comprises the target fluid.
  18. 18. The system according to any preceding claim, further comprising a target fluid flow circuit defining a cold inlet and a hot outlet, wherein target fluid to be heated is received via the cold inlet, and heated target fluid is delivered via the hot outlet.
  19. 19. The system according to claim 18, wherein the target fluid flow circuit is configured to establish heat exchange between the target fluid and the condenser of the heat pump.
  20. 20. The system according to claim 18 or 19, wherein when the heat pump is operating in the defrosting mode of operation the target fluid flow circuit is configured to estabUsh heat exchange between the target fluid which has been cooled by the condenser and the thermal store which has been heated during a previous heating mode of operation of the heat pump.
  21. 21. The system according to daim 18, 19 or 20, wherein the target fluid flow circuit comprises a loop portion which is configured to permit at east a porfion of the target fluid to be deUvered between the heat pump, such as a d&superheater component of the heat pump; and the thermal store, during the heating mode of operation of the heat pump.
  22. 22. The system according to any preceding claim, wherein the thermal store comprises a plate heat exchanger.
  23. 23. A method of operating a heat pump system, comprising: arranging an evaporator of a heat pump in heat exchange with a heat source, and arranging a condenser of the heat pump in heat exchange with a target fluid; establishing a heating mode of operation in which heat is transferred from the heat source to heat the target fluid, and heating a thermal store comprising a phase change material; and then establishing a defrosting mode of operation in which heat is transferred from the target fluid to heat the evaporator, and the thermal store provides heat to reheat the target fluid,
  24. 24. A heat pump defrosting system comprising a thermal store including a phase change material configured to be heated during a heating mode of operation of an associated heat pump, and to heat a target fluid during a defrosting operation of the heat pump.
  25. 25. A heat pump system using air as the heat source where a reversed cyde defrosting system is used to defrost an air cooler and where a thermal store containing a phase change material is used to reheat flowing water that had been cooled as a result of the reversed cycle defrost.
  26. 26. A heat pump system, comprising: a heat pump having an evaporator to be arranged in heat exchange with a heat source and a condenser to be arranged in heat exchange with a target fluid, wherein the heat pump is operational in a heating mode of operation in which heat is transferred from the heat source to heat the target fluid; and a therma' store comprising a phase change materia' configured to further heat the target fluid.Amendments to the claims have been filed as follows CLAMS: I A heat pump system, corn pdsng: a heat pump having an evaporator to be arranged in heat exchange with a heat source and a condenser to be arranged in heat exchange with a target flthd, wherein the heat pump is configurable between a heafing mode of operatbn in which heat is transferred from the heat source to heat the target fluid, and a defrosfing mode of operation in which heat is transferred from the target fluid to heat the evaporator to remove frost formed thereon; and a thermal store configured to be heated when said heat pump k in a heating mode of operation, and to heat the target fluid when the heat pump is in a defrosting mode of operafion, wherein the thermal store compdses a phase change material C\J configured to be transitionS between thfferent phases during the heating and r defrosting modes of operation of the heat pump.r 2. The system according to claim I, wherein the heat source comprises air.3. The system according to cm I or 2, wherein the heat pump comprises a working fluid configured to be communicated between the evaporator and condenser to transfer heat therebetween, 4. The system according to any preceding claim, configured to reverse flow of a working fluid within the heat pump to estabsh the defrosting mode of operation.The system according to any preceding claim, wherein the thermal store is heated by the heat pump during the heating mode of operation.6, The system according to any precedftig daim, wherein duhng the heating mode of operation the phase change material is configured to transition into a state of higher enthalpy, absorbing latent heat.7, The system according to any preceding cm, wher&n during the defrosting mode of operation the phase change material is configured to transition into a state of lower enthalpy, relea&ng latent heat.8. The system according to any preceding claim, wherein the phase change material is configured or selected to undergo a phase transition at a temperature higher than a desired heated temperature of the target fluid.9. The system according to any preceding claim, wherein the phase change r material is configured to undergo a phase transition at a temperature which is lower C than an operational temperature of the heat pump, for example lower than the temperature of a working fluid within the heat pump.10. The system according to any preceding claim, wherein the thermal store is heated by heat exchange wffli one or more components of the heat pump.11. The system according to any preceding claim, wherein the thermal store is heated by heat exchange with a working fluid within the heat pump.12. The system according to any preceding claim, wherein the thermal store is heated by heat exchange with a working fluid at a location downstream of a compressor within the heat pump, and upstream of the condenser of the heat pump.13. The system according to any preceding cm, wherein the thermal store is heated by a working flthd wfthh the heat pump at a temperature higher than the saturation temperature of the working fluid, 14. The system according to any preceding daim, wherein the thermal store is heated by direct heat exchange with one or more components of the heat pump.15. The system according to any preceding claim, wherein the thermal store is heated by indirect heat exchange with one or more components ol the heat pump.16. The system according to daim 15, wherein the thermal store is heated by an intermediate heat exchange fluid which is communicated between one or more C'iJ components of the heat pump and the thermal store. r0 17, The system according to claim 16, wherein the intermediate heat exchange fluid comprises the target fluid.18. The system according to any preceding claim, further comprising a target fluid flow circuit defining a cold inlet and a hot outlet, wherein target fluid to be heated is received via the cold inlet, and heated target fluid is delivered via the hot outlet.19. The system according to claim 18, wherein the target fluid flow circuit is configured to establish heat exchange between the target fluid and the condenser of the heat pump.20. The system according to claim 18 or 19, wherein when the heat pump is operating in the defrosting mode of operation the target fluid flow circuit is configured to establish heat exchange between the target fluid which has been cooled by the condenser and the thermal store which has been heated durkig a prevbus heathig mode of operafion of the heat pump.21. The system according to daim 16, 19 or 20, wher&n the target fluid flow drctht comprises a loop portion which is configured to permit at least a portion of the target fluid to be delivered between the heat pump, such as a desuperheater component of the heat pump, and the thermal store, during the heating mode of operation of the heat pump.22. The system according to any preceding claim, wherein the thermal store comprises a plate heat exchanger.23. The system according to any preceding claim, wherein the phase change r material is a wax, c'J 24. The system according to any preceding claim, wherein the phase change c'J matenal s a fatty acid.25. The system according to any preceding claim, wher&n the phase change material is selected from stearic acid, palmitic acid and mixtures thereof.26. A method of operating a heat pump system, comprising: arranging an evaporator of a heat pump in heat exchange with a heat source, and arranging a condenser of the heat pump in heat exchange with a target fluid; establishing a heating mode of operation in which heat is transferred from the heat source to heat the target fluid, and heating a thermal store comprising a phase change material; and then estabshing a defrosting mode of operation in which heat is transferred from the target fluid to heat the evaporator, and the thermal store provides heat to reheat the target fluid.
  27. 27. A heat pump defrosfing system comprising a thermS store including a phase change material configured to be heated during a heating mode of operation of an associated heat pump? and to heat a target fluid during a defrosting operation of the heat pump.
  28. 28. A heat pump system using air as the heat source where a reversed cycle defrosting system is used to defrost an air cooler and where a thermal store containing a phase change material is used to reheat flowing water that had been C\I cooled as a result of the reversed cycle defrost. r c\J0
  29. 29. A heat pump system, comprising: a heat pump having an evaporator to be arranged in heat exchange with a heat source and a condenser to be arranged in heat exchange with a target fluid, wherein the heat pump is operational in a heating mode of operation in which heat is transferred from the heat source to heat the target fluid; and a therma store comprising a phase change material configured to further heat the target fluid.
GB1103071.5A 2011-02-23 2011-02-23 Heat pump system with a thermal store comprising a phase change material Withdrawn GB2488331A (en)

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CN104101126A (en) * 2014-07-25 2014-10-15 上海理工大学 Continuous heat-supplying phase change energy storage overlapped type air source heat pump system and operation method thereof
CN104534653A (en) * 2014-12-30 2015-04-22 黑龙江国德节能服务有限公司 Recycling and cyclic utilization device and cyclic utilization method for heat energy of waste water and waste gas of campus canteen
CN104879916A (en) * 2015-05-27 2015-09-02 合肥美的暖通设备有限公司 Heat pump water heater
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CN105650943A (en) * 2016-03-31 2016-06-08 天津众石睿哲科技有限责任公司 Phase-change heat storage type carbon dioxide air source solar-assisted heat pump
CN105758064A (en) * 2016-03-09 2016-07-13 北京工业大学 Self-cleaned photoelectric frost thickness sensor
CN105783317A (en) * 2016-04-19 2016-07-20 上海理工大学 Continuous heating phase change energy storage cascade air source heat pump experiment system
CN105890211A (en) * 2016-04-08 2016-08-24 陈建平 Energy-storage interconnected heat pump system suitable for heat supply of cold regions
WO2017221025A1 (en) * 2016-06-23 2017-12-28 Sunamp Limited Phase change material-based enhancement for reversed-cycle defrosting in vapour compression refrigeration systems
GB2604955A (en) * 2021-02-07 2022-09-21 Octopus Energy Group Ltd Methods and systems for performing a heat pump defrost cycle
EP4249812A1 (en) * 2022-03-25 2023-09-27 Mitsubishi Electric R&D Centre Europe B.V. System and method for providing domestic hot water and/or space heating within a building
US20240102671A1 (en) * 2021-02-07 2024-03-28 Octopus Energy Heating Limited Methods and systems for performing a heat pump defrost cycle

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CN101413744A (en) * 2008-11-25 2009-04-22 哈尔滨工业大学 Air source heat pump phase-change energy storage defrosting system with super cooling effect
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CN105276874A (en) * 2014-07-10 2016-01-27 南京理工大学 Heat pump air-conditioning unit achieving thermal defrosting through supercooling of stored liquid
CN104101126B (en) * 2014-07-25 2017-01-25 上海理工大学 Continuous heat-supplying phase change energy storage overlapped type air source heat pump system and operation method thereof
CN104101126A (en) * 2014-07-25 2014-10-15 上海理工大学 Continuous heat-supplying phase change energy storage overlapped type air source heat pump system and operation method thereof
CN104534653A (en) * 2014-12-30 2015-04-22 黑龙江国德节能服务有限公司 Recycling and cyclic utilization device and cyclic utilization method for heat energy of waste water and waste gas of campus canteen
CN104879916A (en) * 2015-05-27 2015-09-02 合肥美的暖通设备有限公司 Heat pump water heater
CN104879916B (en) * 2015-05-27 2018-06-05 合肥美的暖通设备有限公司 Teat pump boiler
CN105758064A (en) * 2016-03-09 2016-07-13 北京工业大学 Self-cleaned photoelectric frost thickness sensor
CN105650943A (en) * 2016-03-31 2016-06-08 天津众石睿哲科技有限责任公司 Phase-change heat storage type carbon dioxide air source solar-assisted heat pump
CN105890211A (en) * 2016-04-08 2016-08-24 陈建平 Energy-storage interconnected heat pump system suitable for heat supply of cold regions
CN105890211B (en) * 2016-04-08 2018-05-08 陈建平 A kind of accumulation of energy interconnection heat pump system of suitable cold district heat supply
CN105783317A (en) * 2016-04-19 2016-07-20 上海理工大学 Continuous heating phase change energy storage cascade air source heat pump experiment system
CN105783317B (en) * 2016-04-19 2018-08-28 上海理工大学 Continuous heat supply phase-changing energy-storing overlapping air source heat pump experimental system
WO2017221025A1 (en) * 2016-06-23 2017-12-28 Sunamp Limited Phase change material-based enhancement for reversed-cycle defrosting in vapour compression refrigeration systems
US11193702B2 (en) 2016-06-23 2021-12-07 Sunamp Limited Phase change material-based enhancement for reversed-cycle defrosting in vapour compression refrigeration systems
GB2604955A (en) * 2021-02-07 2022-09-21 Octopus Energy Group Ltd Methods and systems for performing a heat pump defrost cycle
GB2604955B (en) * 2021-02-07 2023-04-05 Octopus Energy Heating Ltd Methods and systems for performing a heat pump defrost cycle
US20240102671A1 (en) * 2021-02-07 2024-03-28 Octopus Energy Heating Limited Methods and systems for performing a heat pump defrost cycle
EP4249812A1 (en) * 2022-03-25 2023-09-27 Mitsubishi Electric R&D Centre Europe B.V. System and method for providing domestic hot water and/or space heating within a building

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