EP4624828A1

EP4624828A1 - Assembly comprising a heat pump and a cascade module and the associated method of operating

Info

Publication number: EP4624828A1
Application number: EP25165961.1A
Authority: EP
Inventors: Matthew Clark; Eduardo Iturbide RODRIGUEZ; Johannes Kohler Mendizabal; Ahmad Mahmoud
Original assignee: Carrier Corp
Current assignee: Carrier Corp
Priority date: 2024-03-26
Filing date: 2025-03-25
Publication date: 2025-10-01
Also published as: CN120702016A; US20250305694A1

Abstract

An assembly includes a heat pump (20) and a cascade module (50) fluidly couplable to the heat pump. The cascade module is fluidly connected to the heat pump during a first mode of operation to increase a capacity of the heat pump and the cascade module is not fluidly connected to the heat pump during a second mode of operation.

Description

BACKGROUND

Embodiments of the present invention pertain to the art of heating, ventilation, and air-conditioning (HVAC) systems.
Heat pumps are used in a variety of settings, for example, in heating, ventilation, and air fluid conditioning (HVAC) systems that provide a desired air temperature in a facility. Such heat pumps commonly include a compressor, evaporator, expansion device, and condenser. The heat pumps input work to the refrigerant, e.g., by driving the compressor, thereby enabling the refrigerant to move heat from a colder heat reservoir to a warmer heat sink.
Some heat pumps are provided as "split" systems, having a first heat exchanger arranged inside of the building to be conditioned and a second heat exchanger located outside of the building to be conditioned. When such a heat pump is used in areas having very cold outdoor temperatures, the heat pump is forced to operate at a high-pressure ratio which results in increased power consumption. In addition the density of the refrigerant is lower at colder outdoor temperatures and this results in a decreased refrigerant mass flow. Further, as the temperature outdoors drops, the building load increases so the heating capacity output of the heat pump is critical. There is therefore a need to improve the performance of a heat pump that operates at lower outdoor air temperatures.

BRIEF DESCRIPTION

According to a first aspect of the invention, an assembly includes a heat pump and a cascade module fluidly couplable to the heat pump. The cascade module is fluidly connected to the heat pump during a first mode of operation to increase a capacity of the heat pump and the cascade module is not fluidly connected to the heat pump during a second mode of operation.
Optionally, the heat pump includes an indoor unit and an outdoor unit.
Optionally, the cascade module is a separate module, removably mounted at the outdoor unit.
Optionally, the cascade module is a separate module, removably mounted at the indoor unit.
Optionally, the cascade module is a separate module, positioned remotely from both the indoor unit and the outdoor unit.
Optionally, the cascade module is integral with the heat pump.
Optionally, the heat pump includes a compressor, a first heat exchanger, at least one expansion device, and a second heat exchanger and the cascade module includes a second compressor and a cascade heat exchanger.
Optionally, when the cascade module is fluidly connected to the heat pump during the first mode of operation, the assembly includes a first vapor compression loop associated with the compressor and a second vapor compression loop associated with the second compressor and the first vapor compression loop and the second vapor compression loop are thermally coupled at the cascade heat exchanger.
Optionally, in the first mode of operation, the compressor, the cascade heat exchanger, the at least one expansion device and the second heat exchanger are fluidly connected and in combination form the first vapor compression loop.
Optionally, in the first mode of operation, the second compressor, the first heat exchanger, the at least one expansion device, and the cascade heat exchanger are fluidly connected and in combination form the second vapor compression loop.
Optionally, during the second mode of operation, the assembly includes a single vapor compression loop defined by the heat pump.
Optionally, a controller is operably coupled to the compressor, the second compressor, and at least one valve. The controller is configured to identify a mode of operation associated with a demand on the heat pump and operate the at least one valve to initiate operation in the identified mode.
Optionally, the assembly includes at least one sensor operably coupled to the controller, the at least one sensor being configured to monitor at least one parameter or operating condition associated with the heat pump.
According to a second aspect of the invention, a method of operating a heat pump includes: receiving a demand on the heat pump, determining a mode of operation in response to the demand by comparing the demand with a heating capacity of the heat pump, and if the demand is greater than the heating capacity of the heat pump, fluidly connecting a cascade module to the heat pump.
Optionally, fluidly connecting the cascade module to the heat pump further comprises operating at least one valve to control a flow of refrigerant to the cascade module.
Optionally, if the demand is less than the heating capacity of the heat pump, the method comprises fluidly isolating the cascade module from the heat pump.
Optionally, fluidly disconnecting the cascade module from the heat pump further comprises operating at least one valve to direct a flow of refrigerant away from the cascade module.
Optionally, the method comprises monitoring the heating capacity of a heat exchanger of the heat pump and initiating a defrost mode when the heating capacity of the heat exchanger is less than or equal to a threshold.
Optionally, initiating the defrost mode includes fluidly connecting the cascade module to the heat pump and transforming at least one reversing valve from a first position to a second position.
Optionally, monitoring the heating capacity of the heat exchanger further comprises monitoring at least one parameter or operating condition of the heat pump associated with the heating capacity.
Optionally, the at least one parameter or operating condition of the heat pump is at least one of temperature, pressure, and refrigerant mass flow.

BRIEF DESCRIPTION OF THE DRAWINGS

The following descriptions should not be considered limiting in any way. With reference to the accompanying drawings, like elements are numbered alike:

FIG. 1 is a schematic diagram of an exemplary heat pump;
FIG. 2A is a schematic diagram of an exemplary heat pump in a first mode;
FIG. 2B is a schematic diagram of an exemplary heat pump in a second mode;
FIG. 3 is a schematic diagram of a fluid conditioning system;
FIG. 4 is a schematic diagram of the fluid conditioning system of FIG. 3 in a full load heating mode of operation;
FIG. 5 is a schematic diagram of the fluid conditioning system of FIG. 3 in a partial load heating mode of operation;
FIG. 6 is a schematic diagram of the fluid conditioning system of FIG. 3 in a full load cooling mode of operation;
FIG. 7 is a schematic diagram of the fluid conditioning system of FIG. 3 in a partial load cooling mode of operation; and
FIG. 8 is a schematic diagram of a control system of a heat pump.

DETAILED DESCRIPTION

A detailed description of one or more embodiments of the disclosed apparatus and method are presented herein by way of exemplification and not limitation with reference to the Figures.
With reference now to FIG. 1, a schematic diagram of an example of a basic vapor compression cycle of a fluid conditioning system 20, such as an air conditioning system for example, is illustrated. The vapor compression cycle includes one or more compressors 22, a first heat exchanger 24, an expansion device 26, and a second heat exchanger 28. A fluid, such as a refrigerant for example, is configured to circulate through the vapor compression cycle, such as in a counterclockwise direction for example.
In operation, the compressor 22 receives a refrigerant vapor from the second heat exchanger 28 and compresses it to a high temperature and pressure. The relatively hot refrigerant vapor is then delivered to the first heat exchanger 24 where it is cooled and condensed to a liquid state via heat exchange relationship with a cooling medium C, such as air or water. Accordingly, when the first heat exchanger 24 receives the refrigerant output from the compressor 22, the first heat exchanger functions as a condenser. The cooled liquid refrigerant flows from the first heat exchanger 24 to the expansion device 26, such as an expansion valve for example, in which the refrigerant is expanded to a lower pressure where the temperature is reduced and the refrigerant may exist in a two-phase liquid/vapor state. From the expansion device 26, the refrigerant is provided to the second heat exchanger 28. Because heat is transferred from a secondary medium, such as air for example, to the refrigerant within the second heat exchanger 28, causing any refrigerant in the liquid phase to vaporize, the second heat exchanger 28 functions as an evaporator. From the second heat exchanger 28, the low-pressure vapor refrigerant returns to the compressor 22 so that the cycle may be repeated.
Where the fluid conditioning system 20 is a heat pump, the flow of refrigerant within the vapor compressor cycle may be reversed. In such instances, the refrigerant may flow clockwise from the compressor 22 to the second heat exchanger 28, the expansion device 26, and the first heat exchanger 24 sequentially. In such instances, the refrigerant within the second heat exchanger 28 is cooled and condensed to a liquid state and the refrigerant within the first heat exchanger is heated to form a low-pressure vapor. Accordingly, when operating in this reverse flow direction, the second heat exchanger 28 functions as the condenser and the first heat exchanger 24 functions as the evaporator of the vapor compression cycle.
With reference now to FIGS. 2A-2B, a schematic diagram of a heat pump 20 is shown. In the illustrated, non-limiting example, the heat pump 20 includes a first, indoor unit or portion 30 positioned inside a building to be conditioned and a second outdoor unit or portion 32 positioned outside of the building. It should be understood that embodiments where the fluid conditioning system 20 is installed in a single casing located partially or completely inside or outside of the building are also within the scope of the invention.
As shown, at least one compressor 22 is located within the outdoor unit 32. The one or more compressors 22 may be any suitable single or multistage compressor, including, but not limited to a screw compressor, reciprocating compressor, centrifugal compressor, scroll compressor, rotary compressor, or axial-flow compressor. The compressor(s) 22 may be fixed speed or variable speed and may be driven by an electrically powered motor, or another suitable energy source.
The first heat exchanger 24 is arranged within the indoor unit 30 and is directly or indirectly fluidly coupled to the one or more compressors 22. The first heat exchanger 24 may be any suitable type of heat exchanger configured to transfer heat between a refrigerant and air or another medium. For example, the first heat exchanger 24 may include one or more coils of thermally conductive material, such as copper, aluminum, alloys thereof, or combinations thereof. In other embodiments, the first heat exchanger 24 may be a round-tube plate fin, microchannel, shell-and tube heat exchanger, a printed circuit heat exchanger, a plate-fin heat exchanger, or any combination thereof. In the illustrated, non-limiting example, the air or other medium is moved (drawn, blown, or pumped) over the first heat exchanger 24 via a first movement mechanism 34, such as a axial or centrifugal fan for example.
The fluid conditioning system 20 includes at least one expansion device 26. Although a single expansion device 26 is illustrated, it should be understood that embodiments having a separate indoor expansion device positioned within the indoor portion and an outdoor expansion device positioned within the outdoor portion are also contemplated herein. The first heat exchanger 24 is fluidly coupled to the expansion device 26.
The second heat exchanger 28 is arranged within the outdoor unit 32 of the fluid conditioning system 20 and is also fluidly coupled to the expansion device 26. In embodiments including a separate indoor expansion device and outdoor expansion device 26, the first heat exchanger 24 is fluidly coupled to a first (indoor) expansion device and the second heat exchanger 28 is fluidly coupled to a second (outdoor) expansion device. In some embodiments, refrigerant is only configured to flow through one of the expansion devices in each direction of flow through the refrigeration circuit. In other embodiments, the refrigerant may be configured to flow through both expansion devices 26, 26a in series, regardless of a direction of flow; however, the refrigerant will only be expanded in one of the expansion devices, such as the downstream expansion device relative to the direction of flow, and the flow will be unrestricted in the other expansion device.
Similar to the first heat exchanger 24, the second heat exchanger 28 may be any suitable type of heat exchanger configured to transfer heat between a refrigerant and air or another medium. In the illustrated, non-limiting example, the second heat exchanger 28 is disposed about the outer extent of the outdoor unit 32. However, embodiments where the second heat exchanger 28 is arranged at another location, such as within or proximal to the outdoor unit 32 are also contemplated herein.
The second heat exchanger 28 may have any suitable configuration. For example, the second heat exchanger 28 may include one or more coils of thermally conductive material, such as copper, aluminum, alloys thereof, or combinations thereof. In other embodiments, the second heat exchanger 28 may be a round-tube plate fin heat exchanger, microchannel heat exchanger, shell-and tube heat exchanger, a printed circuit heat exchanger, a plate-fin heat exchanger, or any combination thereof.
In the illustrated, non-limiting example, the outdoor unit 32 includes a second movement mechanism 36, such as a fan assembly for example, to move air or another medium over the second heat exchanger 28. The second movement mechanism 36 may be arranged adjacent a top 38 of the outdoor unit 32, as shown, or may be positioned near a bottom 40 of the outdoor portion, or at any point between the top 38 and the bottom 40 to push or pull air through the outdoor portion.
The fluid conditioning system 20 additionally includes a reversing valve 42 configured to redirect the flow of refrigerant R therein. In the illustrated example, the reversing valve 42 is arranged within the outdoor unit 32 and includes a fluidly separate first flow path and second flow path. In a first state, as shown in FIG. 2A, the first flow path fluidly connects an outlet of the one or more compressors 22 to the first heat exchanger 24, and the second flow path fluidly connects the second heat exchanger 28 to an inlet of the one or more compressors 22. In a second state, the first flow path fluid connects the outlet of the one or more compressors 22 to the second heat exchanger 28 and the second flow path fluidly connects the first heat exchanger 24 to the inlet of the one or more compressors 22 (FIG. 2B). It should be understood that the fluid conditioning system 20 illustrated and described herein is intended as an example only and that a fluid conditioning system having another configuration and/or additional components arranged along the fluid flow path are also within the scope of the invention.
The fluid conditioning system may be operable in a "heating" mode, as shown in FIG. 2A. When the reversing valve 42 is in the first state, refrigerant is configured to flow through the closed refrigeration circuit from the compressor 22 to the first heat exchanger 24 acting as a condenser. Within the first heat exchanger 24, heat is transferred from the refrigerant to the air moving across the first heat exchanger 24 by the first movement mechanism 34. This warmed air may be used to heat one or more areas to be conditioned within the building. The partially or fully condensed liquid refrigerant is provided from the first heat exchanger 24 to the expansion device 26 where the pressure is reduced causing the refrigerant to be expanded and cooled to a temperature below the ambient temperature. Within the second heat exchanger 28, heat is transferred to the refrigerant from the air moving across the second heat exchanger 28 by the second movement mechanism 36. This heat causes the liquid portions of the refrigerant to evaporate to a gaseous phase. From the second heat exchanger 28, the refrigerant is returned to the compressor 22 via the reversing valve 42.
During normal operation of the fluid conditioning system in a heating mode, frost can accumulate on the second heat exchanger 28. When frost accumulates on the second heat exchanger 28, the frost diminishes heat transfer from the air to the heat exchanger and therefore provides undesirable insulating properties to the heat exchanger. The undesirable insulating properties result in an increase in the temperature difference between the temperature of the air and the temperature of the heat exchanger. As the extent and thickness of frost increases, the degree of insulating properties of the frost increases. Accordingly, the temperature of the second heat exchanger 28 will continue to decrease indefinitely as frost continues to accumulate.
As frost accumulates on the second heat exchanger 28 and the operating temperature of the second heat exchanger 28 decreases, the operating temperature of the refrigerant within the second heat exchanger 28 decreases as a result. Given a fixed amount of superheat, the density of the refrigerant vapor leaving the second heat exchanger 28 decreases as the temperature of the vapor decreases. Decreasing vapor density for a given volume flow results in decreasing mass flow, and the heating capacity of the refrigerant system decreases. Therefore, the extent and thickness of the presence of frost will directly relate to a decrease in mass flow and heating capacity.
To eliminate, or at least mitigate, this frost, the fluid conditioning system 20 may transition to a defrost mode, such as by switching the reversing valve 42 to the second state. In the second state, shown in FIG. 2B the direction of flow of refrigerant through the closed refrigerant circuit is reversed. Accordingly, the warm, high pressure refrigerant output from the at least one compressor 22 is routed to the second heat exchanger 28 such that the second heat exchanger 28 functions as a condenser rather than as an evaporator. As the second heat exchanger 28, heat is rejected from the fluid, thereby melting the frost to prepare the second heat exchanger 28 for operation as an evaporator once the system transforms back to a heating mode. In the defrost mode, the second movement mechanism 36 may be disabled to prevent air movement through the second heat exchanger 28 thus enabling the temperature of the second heat exchanger 28 to increase.
From the second heat exchanger 28, the refrigerant is expanded in an expansion device 26, such as the indoor expansion device (not shown), and then is delivered to the first heat exchanger 24, which is configured to operate as an evaporator. Within the first heat exchanger 24, the refrigerant can absorb heat from the medium moving across the first heat exchanger 24 via the first movement mechanism 34. In the example, the fluid conditioning system 20 includes an auxiliary heater 44 configured to heat the cool air output from the first heat exchanger 24 during a defrost cycle to meet the heating demands of the area being conditioned. From the first heat exchanger 24, the refrigerant is returned to the compressor 22 via the reversing valve 42.
With reference now to FIGS. 3-8, a fluid conditioning system 20 according to an embodiment is illustrated. In an embodiment, the fluid conditioning system 20 is similar to the heat pump described above with respect to FIGS. 2A and 2B; however, the fluid conditioning system 20 additionally includes or is connected to a cascade module 50 selectively operable to extend the operating conditions of the fluid conditioning system 20. In some embodiments, the cascade module 50 is an integral portion of the fluid conditioning system 20. In such embodiments, the indoor unit 30, outdoor unit 32, and cascade module 50 may be packaged as a single unit. In other embodiments, the cascade module 50 is separate module that can be attached to and removed from both new and existing fluid conditioning systems.
When installed, the cascade module 50 may be fluidly coupled to at least a portion of the fluid conditioning system 20. For example, the cascade module 50 may be fluidly coupled to the outdoor unit 32, to the indoor unit 30, or both. Further, the cascade module 50 may be continuously fluidly connected to the fluid conditioning system 20, or alternatively, may be selectively fluidly connected to the fluid conditioning system 20. In embodiments where the cascade module 50 is selectively fluidly connected to the fluid conditioning system 20, one or more valves V are operable to control the flow of refrigerant in response to a desired mode of operation of the fluid conditioning system. For example, the at least one valve may be operated to direct a flow of refrigerant to the cascade module 50 or may be operated to direct a flow of refrigerant away from the cascade module 50.
The cascade module 50 may include a plurality of components. In the illustrated, non-limiting embodiment, the components include a compressor 52, and a heat exchanger 56 (see FIG. 4). In an embodiment, the cascade module 50 may additionally include a reversing valve 54. However, embodiments including only a portion of these components, additional components, and/or alternative components are also within the scope of the invention. It should be appreciated that the cascade module 50 may additionally include one or more conduits operable to fluidly connect components of the cascade module 50 to one another or to another portion of the heat pump 20. Further, these conduits may cooperate with or may form conduits that define a direct flow path between the indoor unit 30 to the outdoor unit 32.
In some embodiments, the plurality of components is integrated or packaged within a single housing or unit, illustrated schematically at 60 in FIG. 3. In such embodiments, the housing 60 is located at, and in some embodiments is mechanically affixed to, a portion of the outdoor unit 32 or a portion of the indoor unit 30. Further, in other embodiments, the components associated with the cascade module 50 may be separated into a plurality of packages or units. In such embodiments, the units may be mounted at the same location about the fluid conditioning system 20, such as the outdoor unit 32 or the indoor unit 30 for example, or may be split between the indoor unit 30 and the outdoor unit 32. Further, embodiments where a unit including at least a portion of the cascade module 50, and in some embodiments the entirety of the cascade module, is mounted at another location remote from both the indoor unit 30 and outdoor unit 32 are also contemplated herein. For example, the fluid conditioning system 20 may be associated with a building, and the cascade module 50 may be positioned at a different location about the building than the indoor unit 30.
When the cascade module 50 is fluidly connected to the fluid conditioning system 20, the overall capacity of the heat pump 20 is increased. As used herein, the term "fluidly connected" when used relative to the cascade module 50 is intended to describe embodiments where at least one of the compressor 52 and the heat exchanger 56 of the cascade module 50 is configured to receive a flow of refrigerant. In an embodiment, such as shown in FIGS. 4 and 6 for example, when the cascade module 50 is fluidly connected to the heat pump 20, the heat pump 20 is transformed from a single vapor compression loop to a plurality of fluidly separate vapor compression loops. For example, the fluid conditioning system 20 may include two fluidly separate compression loops, identified at VC1 and VC2 respectively, thermally coupled to one another. The vapor compression loops VC1, VC2 may be thermally coupled at a component of the cascade module 50. As will be described in more detail below, in an embodiment, the two vapor compression loops VC1, VC2 are thermally coupled to one another at the heat exchanger 56 of the cascade module 50 during one or more modes of operation.
The heat pump 20 is operable in a plurality of modes. For example, the modes of operation may include but are not limited a full load heating mode, a partial load heating mode, a full load cooling mode, a partial load cooling mode, and a turbo defrost mode. With reference to FIG. 4, a schematic diagram of the fluid conditioning system 20 in a full load heating mode is illustrated. In the full load heating mode, the cascade module 50 is fluidly connected to the remainder of the fluid conditioning system 20. The reversing valve 42 is in a first position or state such that the refrigerant within the first vapor compression loop VC1 is configured to flow from the compressor 22 of the outdoor unit 32 to a first pass 62 of the cascade heat exchanger 56 of the cascade module 50. The first pass 62 of the cascade heat exchanger 56 functions as a condenser causing the refrigerant of the first vapor compression loop VC1 to be cooled therein. The resulting cool liquid refrigerant is then provided to an expansion device 26, such as within the outdoor unit 32, and to the second heat exchanger 28 of the outdoor unit 32 operable as an evaporator in series. The refrigerant vapor output from the evaporator 28 is then returned to the inlet of the compressor 22 to repeat the cycle.
Similarly, the reversing valve 54 of the cascade module 50 is in a first position such that the refrigerant within the second vapor compressor loop VC2 is configured to flow from the outlet of the compressor 52 of the cascade module 50 to the first heat exchanger 24. In the full load heating mode, the first heat exchanger 24 functions as a condenser, thereby cooling the refrigerant to a liquid. From the first heat exchanger 24, the refrigerant of the second vapor compression loop VC2 flows to an expansion device, such as the expansion device 26a arranged within the indoor unit 30 or an expansion device within the cascade module 50, and then to a second pass 64 of the cascade heat exchanger 56. The second pass 64 of the cascade heat exchanger 56 is configured as an evaporator such that heat from the refrigerant within the first pass 62 (from the first compression loop VC1) of the cascade heat exchanger 56 is transferred to the refrigerant within the second pass 64, thereby causing the refrigerant within the second pass to vaporize. The refrigerant output from the second pass 64 has a higher vapor quality and enthalpy than the refrigerant provided to the second pass, and is returned to the inlet of the compressor 52 of the cascade module 50.
A schematic diagram of a heat pump 20 including a cascade module 50 in a partial load heating mode is illustrated in FIG. 5. In the partial load heating mode, although the cascade module 50 is mechanically connected to the fluid conditioning system 20, the cascade module 50 is not fluidly connected to and does not form a portion of the vapor compression cycle of the fluid conditioning system 20. When the cascade module is not fluidly connected to the heat pump, none of the fluid or refrigerant of the heat pump is provided to the compressor 52 or the heat exchanger 56 of the cascade module 50. However, it should be understood that fluid or refrigerant may be configured to flow or pass through one or more conduits located within the cascade module 50 to pass between the indoor unit 30 and the outdoor unit 32.
In such embodiments, the fluid conditioning system 20 only has a single vapor compression loop. As shown, the reversing valve 42 is in a first position such that refrigerant is configured to flow from the outlet of the compressor 22 of the outdoor unit 32 to the first heat exchanger 24. The condensed refrigerant output from the first heat exchanger may then be provided to an expansion device, such as the expansion device 26 arranged within the outdoor unit 32. From the expansion device 26, the refrigerant is supplied to the second heat exchanger 28, where the refrigerant absorbs heat and transforms into a vapor. This vapor refrigerant is then provided to the inlet of the compressor 22 to repeat the cycle.
With reference to FIG. 6, a schematic diagram of the fluid conditioning system 20 in a full load cooling mode and/or a turbo defrost mode is illustrated. Similar to the full load heating mode, the cascade module 50 is fluidly coupled to the remainder of the fluid conditioning system 20 resulting in a first and second vapor compression loop, VC1, VC2. However, the reversing valves 42 and 54 are in a second position or state such that the flow within each of these loops is reversed relative to the flow in the full load heating mode. As shown, the refrigerant of the first vapor compression loop VC1 is configured to flow from the outlet of the compressor 22 of the outdoor unit 32 to the second heat exchanger 28. Within the second heat exchanger, the refrigerant is cooled and condensed into a liquid. The condensed refrigerant output from the second heat exchanger 28 may then be provided to an expansion device, such as the expansion device 26 of the outdoor unit 32 or an expansion device of the cascade module 50 for example. From the expansion device, the refrigerant is provided to the first pass 62 of the cascade heat exchanger 56 of the cascade module 50. Heat is transferred to the refrigerant within the first pass 62 causing the refrigerant of the first vapor compression loop VC1 to vaporize. The vapor refrigerant output from the first pass 62 of the cascade heat exchanger 56 is then returned to an inlet of the compressor 22.
Similarly, refrigerant within the second vapor compressor loop VC2 is configured to flow from the compressor 52 of the cascade module 50 to the second pass 64 of the cascade heat exchanger 56. In the full load cooling mode, heat from the refrigerant within the second pass 64 of the cascade heat exchanger 56 transfers to the refrigerant within the first pass 62 thereof. As a result, the refrigerant within the second pass of the heat exchanger is cooled. From the cascade heat exchanger 56, the refrigerant of the second vapor compression loop VC2 is provided to an expansion device. In the illustrated, non-limiting embodiment, the flow is provided to the expansion device 26a arranged within the indoor unit 30. However, embodiments where the flow from the cascade heat exchanger 56 is provided to an expansion device of the cascade module 50 are also contemplated herein. From the expansion device 26a, the refrigerant is provided to the first heat exchanger 24 within the indoor unit 30. In such embodiments, the first heat exchanger 24 is configured as an evaporator. From the first heat exchanger 24, the refrigerant of the second vapor compression loop VC2 is returned to the compressor 52 to repeat the cycle.
A schematic diagram of a fluid conditioning system 20 including a cascade module 50 in a partial load cooling mode is illustrated in FIG. 7. In the partial load cooling mode, the cascade module 50 is not fluidly connected to and does not form a portion of the vapor compression cycle of the fluid conditioning system 20. In a cooling mode, the reversing valve 42 is in the second position. As a result, refrigerant is configured to flow from the outlet of the compressor 22 of the outdoor unit 32 to the second heat exchanger 28. The condensed refrigerant output from the second heat exchanger 28 may then be provided to an expansion device, such as the expansion device 26a arranged within the indoor unit 30. From the expansion device 26, the refrigerant is supplied to the first heat exchanger 24, where the refrigerant absorbs heat and is vaporized. The resulting refrigerant is then provided to the inlet of the compressor 22 to repeat the cycle.
The mode of operation of the fluid conditioning system 20 may be selected based on at least one parameter of the fluid conditioning system 20 and/or of the ambient atmosphere. For example, the mode may be selected based on the demand put on the system, such as based on the load or set point of the area being conditioned by the fluid conditioning system 20 and the outdoor air temperature. When the fluid conditioning system 20, absent the cascade module 50, is capable of meeting the demand of the system, such as during a partial load heating mode (FIG. 5) or partial load cooling mode (FIG. 7), the cascade module 50 need not be fluidly connected to the vapor compression cycle. Accordingly, one or more valves V may be transformed between a first configuration, such as an open configuration, and a second configuration, such as a closed configuration or another suitable configuration for example, to fluidly disconnect or isolate the components, such as the compressor 52 and the heat exchanger 56 of the cascade module 50 from the remainder of the fluid conditioning system 20. In embodiments where the fluid conditioning system 20, without the cascade module 50, is not able to meet the demands on the system, the valves V will be operated to fluidly connect the cascade module 50 to the remainder of the system, thereby increasing the capacity of the fluid conditioning system 20. It should be appreciated that a heating or cooling mode is selected based on one or more of the set point of the area being conditioned, the current temperature of the area being conditioned, and the outdoor temperature.
With reference to FIG. 8, in an embodiment, the fluid conditioning system 20 includes a control system 70 configured to control operation of the fluid conditioning system in one of the plurality of modes. The control system 70 of the fluid conditioning system 20 includes a controller 72 having one or more of a microprocessor, microcontroller, application specific integrated circuit (ASIC), or any other form of electronic controller known in the art. The controller 72 is operably coupled to the compressor 22 and/or the compressor 52, at least one reversing valve, such as reversing valve 42 and 54, the one or more valves V, and any other suitable components, such as fan 34, auxiliary heater 44, and/or the expansion device 26, 26a. In an embodiment, the control system 70 additionally includes at least one sensor S operable to monitor one or more operating parameters or operating conditions (referred to collectively herein as parameters) of the fluid conditioning system 20 to determine the mode of operation of the fluid conditioning system 20 at any given time. The at least one sensor S may be configured to continuously monitor and communicate a respective parameter to the controller 72, or alternatively, may be configured to intermittently monitor and communicate a respective parameter to the controller 72.
Although the configuration of the vapor compression loops VC1, VC2 of the fluid conditioning system 20 are the same for both a full load cooling mode and a turbo defrost mode, the conditions required to initiate operation in the turbo defrost mode may vary from those that initiate operation of the fluid conditioning system 20 in the full load cooling mode. In an embodiment, the turbo defrost mode may be initiated in response to the running time of the fluid conditioning system 20 in a heating mode. In other embodiments, the turbo defrost mode is initiated in response to the heating capacity of the second heat exchanger 28 during a heating mode. A comparison of the heating capacity of the second heat exchanger 28 during operation of the heating mode and the heating capacity of the second heat exchanger 28 when no frost is present will indicate the reduction in heating capacity due to frost accumulation on the second heat exchanger 28. It should be appreciated that several parameters of the fluid conditioning system 20 can be used to observe a reduction in heating capacity. Heating capacity relates directly to refrigerant mass flow and occurs primarily with refrigerant phase change (i.e., when it condenses into a liquid or evaporates into a vapor).
In an embodiment, the at least one sensor S that correlates to or is associated with determining the heating capacity of the second heat exchanger 28. The controller 72 may be configured to compare the monitored parameter with a respective threshold to determine when to initiate or trigger operation in the defrost mode. As used herein, the term "monitored parameter" is intended to include parameters or operating conditions that are measured via one or more sensors, or alternatively, parameters or operating conditions that are calculated using the monitored parameters or operating conditions.
The at least one sensor S of the control system 70 may include a temperature sensor. A temperature sensor may be used to monitor one or more or an ambient temperature surrounding the outdoor unit 32, a temperature of the discharge air output from the second heat exchanger 28, and a temperature of the refrigerant circulating within the fluid conditioning system 20, and a temperature of the second heat exchanger 28 itself. In embodiments where the at least one sensor S includes a temperature sensor, the temperature sensor may be any suitable device, including but not limited to a thermistor, thermocouple, thermostat, infrared sensor, etc. Alternatively, or in addition, the at least one sensor S may be a pressure sensor, for example operable to measure a reduction in pressure of the refrigerant. A pressure sensor consisting of any suitable device, including but not limited to a strain gage bridge, for example is within the scope of the invention. In an embodiment, the at least one sensor S includes a mass flow sensor. It should be appreciated that the temperature, pressure, and mass flow rate described herein are intended as exemplary parameters only, and that a reduced heating capacity of the fluid conditioning system can be detected by observing a reduction of some other operating parameter indicative of a reduced heat transfer at the second heat exchanger 28.
The term "about" is intended to include the degree of error associated with measurement of the particular quantity based upon the equipment available at the time of filing the application.
The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the present invention. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises" and/or "comprising," when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, element components, and/or groups thereof.
While the present invention has been described with reference to an exemplary embodiment or embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the present invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the present invention without departing from the scope thereof. Therefore, it is intended that the present invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this present invention, but that the present invention will include all embodiments falling within the scope of the claims.

Claims

An assembly comprising:
a heat pump (20);
a cascade module (50), the cascade module being fluidly couplable to the heat pump; and

wherein the cascade module is fluidly connected to the heat pump during a first mode of operation to increase a capacity of the heat pump and the cascade module is not fluidly connected to the heat pump during a second mode of operation.
The assembly of claim 1, wherein the heat pump (20) includes an indoor unit (30) and an outdoor unit (32).
The assembly of claim 2, wherein the cascade module (50) is a separate module, which is:
removably mounted at the outdoor unit (32); or

removably mounted at the indoor unit (30); or

positioned remotely from both the indoor unit (30) and the outdoor unit (32).
The assembly of claim 1 or 2, wherein the cascade module (50) is integral with the heat pump (20).
The assembly of any of the preceding claims, wherein the heat pump (20) further comprises a compressor (22), a first heat exchanger (24), at least one expansion device (26), and a second heat exchanger (28) and the cascade module (50) further comprises a second compressor (52) and a cascade heat exchanger (56).
The assembly of claim 5, wherein when the cascade module (50) is fluidly connected to the heat pump (20) during the first mode of operation, the assembly includes a first vapor compression loop (VC1) associated with the compressor (22) and a second vapor compression loop (VC2) associated with the second compressor (52) and the first vapor compression loop and the second vapor compression loop are thermally coupled at the cascade heat exchanger (50).
The assembly of claim 6, wherein in the first mode of operation, the compressor (22), the cascade heat exchanger (56), the at least one expansion device (26) and the second heat exchanger (28) are fluidly connected and in combination form the first vapor compression loop (VC1),
and/or wherein in the first mode of operation, the second compressor (52), the first heat exchanger (24), the at least one expansion device (26), and the cascade heat exchanger (56) are fluidly connected and in combination form the second vapor compression loop (VC2).
The assembly of any of claims 5 to 7, wherein during the second mode of operation, the assembly includes a single vapor compression loop defined by the heat pump.
The assembly of claim any of claims 5 to 8, further comprising a controller (72) operably coupled to the compressor (22) and the second compressor (52), and at least one valve (42, 54), the controller being configured to:
identify a mode of operation associated with a demand on the heat pump (20); and

operate the at least one valve (42, 54) to initiate operation in the identified mode.

optionally wherein the assembly further comprises at least one sensor (S) operably coupled to the controller (72), the at least one sensor being configured to monitor at least one parameter or operating condition associated with the heat pump (20).
A method of operating a heat pump (20), the method comprising:
receiving a demand on the heat pump (20);

determining a mode of operation in response to the demand by comparing the demand with a heating capacity of the heat pump; and

wherein if the demand is greater than the heating capacity of the heat pump, fluidly connecting a cascade module (50) to the heat pump (20).
The method of claim 10, wherein fluidly connecting the cascade module (50) to the heat pump (20) further comprises operating at least one valve (42, 54) to control a flow of refrigerant to the cascade module (50).
The method of claim 10 or claim 11, comprising fluidly isolating the cascade module (50) from the heat pump (20) if the demand is less than the heating capacity of the heat pump (20).
The method of any of claims 10 to 12, further comprising:
monitoring the heating capacity of a heat exchanger (28) of the heat pump (20); and

initiating a defrost mode when the heating capacity of the heat exchanger (28) is less than or equal to a threshold.
The method of claim 13, wherein initiating the defrost mode further comprises:
fluidly connecting the cascade module (50) to the heat pump (20); and

transforming at least one reversing valve (42, 54) from a first position to a second position.
The method of claim 14, wherein monitoring the heating capacity of the heat exchanger (28) further comprises monitoring at least one parameter or operating condition of the heat pump (20) associated with the heating capacity,
optionally wherein the at least one parameter or operating condition of the heat pump (20) is at least one of temperature, pressure, and refrigerant mass flow.