Systems and Methods for Heat Pump Systems

This section is intended to provide relevant background information to facilitate a better understanding of the various aspects of the described embodiments. Accordingly, these statements are to be read in this light and not as admissions of prior art.

A heat pump is a refrigerant system that is typically operable in both cooling and heating modes. While air conditioners are familiar examples of heat pumps, the term “heat pump” is more general and applies to many heating, ventilating, and air conditioning (“HVAC”) devices used for space heating or space cooling. A cold climate heat pump (“CCHP”) is a heat pump specially designed for use in cold outdoor temperatures and can provide mechanical air heating utilizing a refrigerant vapor compression cycle or a combination of mechanical air heating and electrical resistance or combustion heating. The US Department of Energy specifies that 5° F. CCHPs are capable of heat pump operation down to at least 5° F. (−15° C.) ambient temperature, and −15 F CCHPs are capable of heat pump operation down to at least −15° F. (−26° C.).

In a cooling mode, a heat pump operates like a typical air conditioner, i.e., a refrigerant flows through an HVAC circuit where the refrigerant is compressed in a compressor and delivered to a condenser (or an outdoor heat exchanger). In the condenser, heat is exchanged between a medium such as outside air, water, or the like and the refrigerant. From the condenser, the refrigerant passes to an expansion device, at which the refrigerant is expanded to a lower pressure and temperature, and then to an evaporator (or an indoor heat exchanger). In the evaporator, heat is exchanged between the refrigerant and the indoor air, to condition the indoor air. When the refrigerant system is operating, the evaporator cools the air that is being supplied to the indoor environment. In addition, as the temperature of the indoor air is lowered, moisture usually is also taken out of the air. In this manner, the humidity level of the indoor air can also be controlled. When a heat pump is used for heating, it employs the same basic refrigeration-type cycle used by an air conditioner or a refrigerator, but refrigerant flows through the HVAC circuit in the opposite direction, releasing heat into the conditioned space rather than the surrounding environment. In this use, heat pumps generally draw heat from cooler external air, water, or from the ground.

Reversible heat pumps (generally referred to herein simply as “heat pumps”) work in either direction to provide heating or cooling to the internal space as mentioned above. Reversible heat pumps employ a reversing, or four-way, valve to reverse the flow of refrigerant from the compressor through the condenser and evaporation coils. In heating mode, the outdoor coil is an evaporator, while the indoor coil is a condenser. The refrigerant flowing from the evaporator (outdoor coil) carries the thermal energy from outside air (or source such as water, soil, etc.) indoors. Vapor temperature is augmented within the pump by compressing it. The indoor coil then transfers thermal energy (including energy from the compression) to the indoor air, which is then moved around the inside of the building by an air handler. The refrigerant is then allowed to expand, cool, and absorb heat from the outdoor environment in the outside evaporator, and the cycle repeats.

For a constant amount of compressor work input, a pressure difference between the input and the output of the compressor is constant. The compressor operation thus increases the enthalpy of the refrigerant by a constant magnitude, between the upper and lower pressures of the compressor. Thus the pressure and temperature difference of the refrigerant (e.g., an operational range) between the indoor and outdoor heat exchangers is set by the upper and lower pressures of the compressor in a standard heating and cooling refrigeration cycle. With a set operational range, the lower limit temperature for the outdoor heat exchanger is thus also limited and the use of the heat pump system is limited to outdoor temperatures greater than or equal to the outdoor heat exchanger temperature. However, the use of heat pump systems is increasingly desirable in colder and colder environments, and thus a need exists for systems and methods that allow for an expansion of the operational range between the indoor and outdoor heat exchangers. Additionally, a need exists for systems and methods that can be used to improve compressor energy efficiency. Recognizing these needs, the US Department of Energy launched a CCHP Technology Challenge in 2021 to accelerate innovation, development, and commercialization of 5° F. CCHP and −15 F CCHP technologies.

Some embodiments disclosed herein are directed to a heat pump heating, ventilation, and air conditioning (heat pump HVAC) system operable to use a refrigerant to heat or cool an indoor space. In an embodiment, the heat pump HVAC system includes a compressor, an outdoor heat exchanger, an indoor heat exchanger, a first expansion device, and a four-way valve connected together as a refrigerant circuit. The four-way valve is configurable to direct refrigerant flow through the first expansion device in a first direction in a cooling mode and in a second direction, opposite the first direction, in a heating mode. Additionally, an ejector is in fluid communication with the refrigerant circuit. When the heat pump HVAC system is in the heating mode, the refrigerant circuit includes a first flow of refrigerant upstream from the outdoor heat exchanger and a second flow of refrigerant downstream from the outdoor heat exchanger. Additionally, the ejector is configurable to combine the first flow and the second flow into a combined flow, at least a portion of which is returned to the compressor.

Other embodiments disclosed herein are directed to a method of operating a heat pump HVAC system operable to use a refrigerant to heat an indoor space in a heating mode or cool an indoor space in a cooling mode. The method includes compressing the refrigerant with a compressor, flowing the refrigerant in a refrigerant circuit including an indoor heat exchanger, a first expansion device, and an outdoor heat exchanger. The refrigerant flows through the first expansion device in a first direction in the cooling mode and in a second direction, opposite the first direction, in the heating mode. The method further including flowing a first flow of refrigerant upstream from the outdoor heat exchanger in the heating mode, flowing a second flow of refrigerant downstream from the outdoor heat exchanger in the heating mode, combining the first flow and the second flow into a combined flow within an ejector in the heating mode, and flowing at least a portion of the combined flow to the compressor in the heating mode.

Still other embodiments disclosed herein are directed to a heat pump HVAC system operable to use a refrigerant to heat or cool an indoor space and including a compressor, an outdoor heat exchanger, an indoor heat exchanger, a first expansion device, and a four-way valve connected together as a refrigerant circuit. The four-way valve is configurable to direct the refrigerant flow through the first expansion device in a first direction in a cooling mode and in a second direction, opposite the first direction, in a heating mode. Additionally, an ejector is in fluid communication with the refrigerant circuit; and an internal heat exchanger is thermally coupling a first flow of refrigerant upstream from the outdoor heat exchanger and a second flow of refrigerant downstream from the outdoor heat exchanger when in the heating mode.

Certain aspects of some embodiments disclosed herein are set forth below. It should be understood that these aspects are presented merely to provide the reader with a brief summary of certain forms the invention might take and that these aspects are not intended to limit the scope of the invention. Indeed, the invention may encompass a variety of aspects that may not be set forth below.

Various refinements of the features noted above may exist in relation to various aspects of the present embodiments. Further features may also be incorporated in these various aspects as well. These refinements and additional features may exist individually or in any combination. For instance, various features discussed below in relation to one or more of the illustrated embodiments may be incorporated into any of the above-described aspects of the present disclosure alone or in any combination. Again, the brief summary presented above is intended only to familiarize the reader with certain aspects and contexts of some embodiments without limitation to the claimed subject matter.

One or more specific embodiments of the present disclosure are described below. In an effort to provide a concise description of these embodiments, not all features of an actual implementation may be described. It should be appreciated that in the development of any such actual implementation, as in any engineering or design project, numerous implementation-specific decisions are made to achieve the developers' specific goals, such as compliance with system-related and business-related constraints, which may vary from one implementation to another. Moreover, it should be appreciated that such a development effort might be complex and time consuming, but would nevertheless be a routine undertaking of design, fabrication, and manufacture for those of ordinary skill having the benefit of this disclosure.

When introducing elements of various embodiments, the articles “a,” “an,” “the,” and “said” are intended to mean that there are one or more of the elements. The terms “comprising,” “including,” and “having” are intended to be inclusive and mean that there may be additional elements other than the listed elements. Also, the term “couple” or “couples” is intended to mean either an indirect or direct connection. Thus, if a first device couples to a second device, that connection may be through a direct connection of the two devices, or through an indirect connection that is established via other devices, components, nodes, and connections. In addition, as used herein, the terms “axial” and “axially” generally mean along or parallel to a given axis (e.g., central axis of a body or a port), while the terms “radial” and “radially” generally mean perpendicular to the given axis. For instance, an axial distance refers to a distance measured along or parallel to the axis, and a radial distance means a distance measured perpendicular to the axis. As used herein, the terms “approximately,” “about,” “substantially,” and the like mean within 10% (i.e., plus or minus 10%) of the recited value. Thus, for example, a recited angle of “about 80 degrees” refers to an angle ranging from 72 degrees to 88 degrees.

Unless the context dictates the contrary, all ranges set forth herein should be interpreted as being inclusive of their endpoints, and open-ended ranges should be interpreted to include only commercially practical values. Similarly, all lists of values should be considered as inclusive of intermediate values unless the context indicates the contrary.

The present disclosure relates to heat pump heating, ventilating, and air conditioning (“heat pump HVAC”) systems using an ejector. More particularly the disclosure relates to systems and methods of using an ejector to improve the heat pump HVAC system thermal performance in a heating mode and expanding an operational envelope with respect to ambient temperatures. While heat pump HVAC systems are discussed, it should also be appreciated that the concepts are also applicable to refrigeration systems.

Referring now to, a heat pump HVAC systemis shown in a partial isometric view, a top view, and a schematic view, respectively. Some components of the heat pump HVAC systemhave been removed fromfor clarity. Although not shown, it should be appreciated that the heat pump HVAC systemincludes additional components such as panel covers for covering and protecting the equipment of the heat pump HVAC system. The example heat pump HVAC systemis a “light” commercial packaged rooftop unit. The heat pump HVAC systemincludes both an “outdoor” section SPand an “indoor” section SPmounted on a common frame. However, the heat pump HVAC systemmay also represent residential packaged, residential split, light commercial split, or commercial applied applications as well as refrigeration system applications. The heat pump HVAC systemmay be a variable refrigerant flow system with variable speed outdoor fans.

As shown in, the outdoor section SPincludes one or more compressors, which may be any suitable type. (e.g., fixed speed, two speed, variable speed, etc.) Without limitation, the outdoor section SPmay also include other HVAC system components, such as accumulators, receivers, charge compensators, flow control devices, air movers, pumps, and filter driers secured within and attached to the structure of the heat pump HVAC system. Also included are one or more outdoor heat exchangersand outdoor fansthat move air into the outdoor section SPacross the outdoor heat exchangerand to the outside of the heat pump HVAC system. The outdoor fansmay be any suitable type of fan, for example, a propeller fan. The outdoor heat exchangersare not shown in infor clarity. Howeverincludes two outdoor heat exchangerscurved along a perimeter of the outdoor section SP. The outdoor heat exchangersmay include a plurality of heat-transfer tubes, in which a refrigerant flows, and a plurality of heat-transfer fins (not shown), in which air flows between gaps thereof. The plurality of heat-transfer tubes may be arranged in an up-down direction (herein referred to as “row direction”), and each heat-transfer tube may extend in a direction substantially orthogonal to the up-down direction (in a substantially horizontal direction). Without limitation, the heat-transfer tubes of the outdoor heat exchangerare connected to each other along end portions via U-shape return bends that allow flow of the refrigerant from a certain column to another column and/or a certain row to another row. The plurality of heat-transfer fins, which extend in the up-down direction, are arranged side by side with a predetermined interval between the plurality of heat-transfer fins. The plurality of heat-transfer fins and the plurality of heat-transfer tubes are assembled to each other so that each heat-transfer fin extends through the plurality of heat-transfer tubes. Alternatively, the plurality of heat-transfer fins may also be disposed in a plurality of columns.

Due to the structure of the outdoor heat exchangers, operation of the outdoor fansdraws an outdoor airflowinto the outdoor section SPand passes through the outdoor heat exchangers. As the outdoor air passes through the outdoor heat exchangersthe outdoor airflowexchanges thermal energy with the refrigerant that flows in the outdoor heat exchangers. After the thermal energy exchange in the outdoor heat exchanger, the air is then also discharged to the outside of the outdoor section SPby the outdoor fans. Even though the outdoor heat exchangeris described as a round tube and plate fin heat exchanger, other heat exchanger types, such as for instance a microchannel heat exchanger, are within the scope of the disclosure.

The outdoor section SPand the indoor section SPare separated by a partition plate. Outdoor airflowpasses into the outdoor section SPand an indoor airflowpasses into the indoor section SP. By separating the outdoor section SPand the indoor section SPby the partition plate, the airflow bypass between the outdoor section SPand the indoor section SPis blocked. Therefore, in an ordinary state, the indoor airflowand the outdoor airflowdo not mix and do not communicate with each other within or via the heat pump HVAC system. It should be noted, that airside economizers allow mixing indoor and outdoor air, however they are not discussed in relation to this disclosure.

The indoor section SPalso includes an indoor heat exchangerand a blower, which may be, for example, a centrifugal fan. The indoor section SPmay also optionally include a combustion heat exchanger (not shown). The indoor heat exchangermay also include a plurality of heat-transfer tubes, in which a refrigerant flows, and a plurality of heat-transfer fins, in which air flows between gaps thereof. The plurality of heat-transfer tubes may be arranged in an up-down direction (row direction), and each heat-transfer tube may extend in a direction substantially orthogonal to the up-down direction. Without limitation, the heat-transfer tubes of the indoor heat exchangerare connected to each other along end portions via U-shape return bends that allow flow of the refrigerant from a certain column to another column and/or a certain row to another row. The plurality of heat-transfer fins and the plurality of heat-transfer tubes may be assembled so that each heat-transfer fin extends through the plurality of heat-transfer tubes. Although the indoor heat exchangeris described as a round tube and plate fin heat exchanger, other heat exchanger types, such as for instance a microchannel heat exchanger, are within the scope of this disclosure.

The indoor heat exchangerdivides the indoor section SPinto spaces upstream and downstream with respect to the indoor airflowpassing through the indoor heat exchanger. The bloweris disposed in the space on the downstream side of the indoor heat exchangerand operation of the blowerimparts the indoor airflowthrough the indoor heat exchangerand thus between a return air openingand a supply air openingwhich each lead to indoor spaces (not shown) to be conditioned. In this manner, a looped circuit of airflow is established between the indoor spaces and the indoor heat exchanger. Although the return air openingand the supply air openingare formed through a bottom platein the example of, side-oriented passages are also feasible.

depict a heat pump HVAC system. In general, when in a cooling mode and a heating mode of operation, a refrigerant circuit circulates the refrigerant to perform a vapor compression refrigeration cycle, whereby heat is exchanged at the indoor heat exchangerand at the outdoor heat exchangers. The direction of heat transfer for the heat exchangers,is reversed between the cooling and heating modes of operation.

The heat pump HVAC systemofdepicts a cooling mode of operation. The heat pump HVAC systemalso includes a refrigerant circuit that recirculates a refrigerant between the indoor heat exchangerand the outdoor heat exchanger. The refrigerant circuit includes the compressor, a configurable four-way valve, the indoor heat exchanger, an expansion device, an ejector, a check valve, a separation tank, the outdoor heat exchanger, an expansion device, and various lines as detailed herein to connect the components of the refrigerant circuit. In the cooling mode, the refrigerant is compressed by the compressorto increase an enthalpy of the refrigerant. A flowof the compressed refrigerant flows through the four-way valve, through a linevia a flow, and to the separation tank. In the cooling mode of operation, the separation tankacts as a pass-through for the refrigerant.

Downstream of the separation tank, the refrigerant then flows in a linevia a flowto the expansion device. Substantially all of the flowis directed to the flow. The check valverestricts flow from the pressurized separation tankthrough a line. In the cooling mode of operation, the expansion deviceis fully open and thus does not change the velocity or pressure of the refrigerant flowing therein. Alternatively, the bypass with the on/off solenoid valve around the expansion valvecan be arranged, if desired. The refrigerant then flows into the outdoor heat exchanger, where heat is exchanged with the outdoor environment via an outdoor airflowestablished by the outdoor fan. In the cooling mode, the refrigerant within the outdoor heat exchangermay be hotter than the outdoor environment. In that case, heat is transferred away from the refrigerant and the enthalpy is reduced as part of the vapor compression cycle.

After the outdoor heat exchanger, the refrigerant is sent through a linevia a flowto the ejector, and then into a linevia a flowout of the ejector. If desired, the bypass with the on/off solenoid valve can be arranged around the ejector. The ejectoris also connected to the refrigerant circuit at a third position via the line. Each of the lines,,are in fluid communication through internal orifices within the ejector, but substantially all of the flowis directed into the flowbecause the check valveis spring loaded (or otherwise biased) to a closed position with a set pressure difference across the check valve. As described, the linehas less or substantially equal pressures between the ejectorand the separation tankand the biased check valveis normally closed when the heat pump HVAC systemis in the cooling mode. The expansion deviceis installed along the lineand expands the flowof the refrigerant therein, causing a reduced pressure, a reduced temperature, and an associated increased volumetric flow rate as shown by a flowdownstream of the expansion device. The expanded and cooled refrigerant of the flowthen passes through the indoor heat exchangerto exchange heat with the indoor airflowestablished by the blower. The enthalpy of the refrigerant is increased as the refrigerant is heated, and the air cooled by the indoor heat exchangeris supplied to the indoor space or environment being conditioned. After the heat exchange at the indoor heat exchanger, the refrigerant is evaporated into a gaseous state and then travels back through a line, the four-way valve, and is then sucked back into the compressorto repeat the cycle. The expansion devicemay be replaced by two unidirectional expansion devices, one dedicated to a cooling mode of operation and the other to a heating mode of operation. Optionally, the ejectormay also include a valve operable to selectively allow the flowinto the flowor a valve to selectively allow flow along the line. Thus, the check valvemay be omitted while still maintaining the functionality described. Optionally, the separation tankmay be placed between the four-way valveand the compressorwithout departing from the principles described herein.

depicts the heat pump HVAC systemin a heating mode of operation. In the heating mode, the refrigerant is again compressed by the compressorto increase an enthalpy of the refrigerant. The flowof the compressed refrigerant is sent through the four-way valveto the indoor heat exchangervia the line. The refrigerant dissipates heat at the indoor heat exchangerto the indoor airflowthat is supplied to the indoor space or environment being conditioned. After the heat exchange at the indoor heat exchanger, the enthalpy of the refrigerant is decreased. The refrigerant is sent via the lineand the flowto the expansion device. At the expansion device, the refrigerant expands which reduces a pressure and temperature of the refrigerant. The refrigerant is then transferred as the flowinto the ejector. Narrowed orifices within the ejectorfocus and accelerate the flowand further reduce the refrigerant pressure within the ejector. The reduced pressure becomes useful to suck in, entrain, and thus mix flows of low pressure and low temperature refrigerant from the flowwithin the line, as discussed below. The orifices within the ejectorthen expand the mixed refrigerants to reduce the refrigerant velocity and increase the pressure and temperature.

The pressure within the lineis greater than the biased pressure setting of the check valveand a combined flowtransfers the refrigerant into the separation tank. At some operating conditions, the pressure and temperature within the separation tankresults in a gas phase of the refrigerant at the top of the separation tankand a liquid phaseof the refrigerant that is condensed and accumulated at the bottom of the separation tank. The liquid phasethen flows via the lineas the flowthrough the expansion device. The expansion deviceexpands the flowof the refrigerant therein, causing a reduced pressure, a reduced temperature, and an associated increased volumetric flow rate as shown by the flowdownstream of the expansion device.

The expanded and cooled refrigerant then passes through the outdoor heat exchangerand absorbs heat from the outdoor environment via the outdoor airflowto increase the enthalpy of the refrigerant. The pressure and temperature of the refrigerant within the lineare less than the pressure and temperature of the refrigerant feeding the ejector via the line, however the operation of the ejectorstill allows mixing and combination of the flows,. As previously described, the accelerated flow and the associated pressure drop within the ejectorcreates a lower pressure within the orifice of the ejectorthat is used to suck in, entrain, and mix the flowwith the flowof refrigerant. In this manner, the flow, which has a relatively higher pressure upstream of the ejector, is mixed with the lower pressure flow, and the resulting combined flowhas a relatively intermediate enthalpy that is between the enthalpy of the flows,leading into the ejector.

By creating an intermediate enthalpy for the combined flow, the flowthat returns to the compressorhas a higher enthalpy than if the flowreturned directly to the compressor. Thus, by using the ejector, the work input energy of the compressoris less to return the enthalpy of the refrigerant to the initial compressed condition, relative to the work input energy required to compress the flowto the initial compressed condition. Stated alternatively, for a constant amount of compressorwork input, a pressure difference between the input (line) and the output (line) is constant. Operation of the compressorthus increases the enthalpy of the refrigerant by a constant magnitude, between the upper and lower pressures of the compressor. The pressure and temperature difference (e.g., an operational range) between the heat exchangers,is set by the upper and lower pressures of the compressorin a standard heating and cooling refrigeration cycle. However, the operational range between the heat exchangers,can be expanded by using the ejectorarrangement. For example, the outdoor heat exchangercan be operated at a lower pressure (and hence at a lower temperature) than the pressure of the flowinto the compressor, because the ejectorwill maintain the needed pressure of the flowby blending the flows,in the manner previously described. By lowering the operational pressure and temperature of the outdoor heat exchanger, greater enthalpy gains are achieved as more heat energy is absorbed by the refrigerant in the outdoor heat exchanger. Additionally, a lower temperature for the outdoor heat exchangeralso allows the use of the heat pump HVAC systemin colder environments because heat transfer is still possible when the outdoor heat exchangeris colder than the outdoor ambient temperature. In an example, the heat pump HVAC systemmay be classified as a cold climate heat pump (“CCHP”), where the outdoor heat exchangerhas an operational range down to at least 5° F. (−15° C.) ambient temperature. Alternatively the heat pump HVAC systemis a CCHP, where the outdoor heat exchangerhas an operational range down to at least −15° F. (−26° C.) ambient temperature. It should be pointed out that in the heating mode of operation, the refrigerant systemcan operate as a conventional system, bypassing the ejectorwhile the expansion deviceis fully open or bypassed. Furthermore, the defrosting or deicing the outdoor heat exchangerin the cold environments can be done by one of the known methods (e.g. reversing the vapor compression cycle, hot gas bypass, etc.).

depict a heat pump HVAC system. In general, when in a cooling mode and a heating mode of operation, the refrigerant circuit circulates the refrigerant to perform a vapor compression refrigeration cycle, whereby heat is exchanged at the indoor heat exchangeran offset heat exchanger, and an outdoor heat exchanger. The direction of heat transfer for the heat exchangers,,is reversed between the cooling and heating modes of operation. In general, some components and the refrigeration circuit of the heat pump HVAC systemare similar to the components and refrigerant circuit of the heat pump HVAC system, and thus the same or similar reference numerals are used. Accordingly, such features will not be described again in detail, except as necessary for the understanding of the heat pump HVAC system.

The heat pump HVAC systemofdepicts a cooling mode of operation. The refrigerant circuit of the heat pump HVAC systemrecirculates a refrigerant between the indoor heat exchanger, the offset heat exchanger, and the outdoor heat exchanger. The refrigerant circuit includes a compressor, a configurable four-way valve, the indoor heat exchanger, an optional expansion device, an ejector, a check valve, an optional three-way valve, the offset heat exchanger, an expansion device, the outdoor heat exchanger, and various lines as detailed herein to connect the components of the refrigerant circuit. In the cooling mode, the refrigerant is compressed by the compressorto increase an enthalpy of the refrigerant. A flowof the compressed refrigerant is sent through the four-way valve, through a linevia a flow, and to the offset heat exchanger. The flow of the refrigerant within the offset heat exchangerexchanges heat with the outdoor environment via an outdoor airflowestablished by an outdoor fan. In the cooling mode, the refrigerant within the offset heat exchangeris hotter than the outdoor environment and thus heat is transferred away from the refrigerant and the enthalpy of the refrigerant is reduced as part of the vapor compression cycle.

After the offset heat exchanger, the refrigerant is sent through a linevia the flowto the ejectorand then into a linevia a flowout of the ejector. The flows,are substantially equal as the ejectormay be configured to not substantially restrict or change the pressure or velocity between the flows,. The ejectoris also connected to the refrigerant circuit at a third position via a line, however the check valverestricts flow along the line. Optionally, the three-way valvemay be included along the lineto direct a bypass flowof the refrigerant to the line, while blocking the flow, and thus bypassing the ejector. The three-way valvemay include larger internal flow passages than the ejector, and thus bypassing the ejectorvia the three-way valvecan allow higher volumetric flowrates of refrigerant while having lower pressure drops. Alternatively, the three-way valvemay be replaced by a solenoid valve (not shown) along the bypass line.

The refrigerant within the linepasses through the outdoor heat exchangeras shown by a flowand exchanges heat with the outdoor airflow. As heat energy is removed from the refrigerant, the enthalpy of the refrigerant is further reduced. Thus, in the cooling mode of operation the offset heat exchangeris in series with and upstream from the outdoor heat exchangerrelative to the outdoor airflowand the heat exchangers,both reduce the enthalpy of the refrigerant as part of the vapor compression cycle. The expansion deviceinstalled along a linethen expands refrigerant, causing a reduced pressure, a reduced temperature, and an associated increased volumetric flow rate as shown by a flowdownstream of the expansion device. The expanded and cooled refrigerant of the flowthen passes through the optional expansion device, which is fully open and thus does not change the velocity or pressure of the refrigerant flowing therein.

The refrigerant continues along a lineand as a flowthat passes through the indoor heat exchangerto exchange heat with an indoor airflowestablished by a blower. The enthalpy of the refrigerant is increased as it is heated, and the air cooled by the indoor heat exchangeris supplied to the indoor space or environment being conditioned. After the heat exchange at the indoor heat exchanger, the refrigerant is evaporated into a gaseous state and then travels back through a line, the four-way valve, and is then sucked back into the compressorto repeat the cycle. Optionally, the expansion devicecan be replaced by two unidirectional expansion devices, one dedicated to a cooling mode of operation and the other to a heating mode of operation. Also optionally, the expansion devicemay also be omitted. Also optionally, an accumulator (not shown) may be placed between the four-way valveand the compressorto ensure separation of gaseous and liquid phases of the returned refrigerant.

The heat pump HVAC systemofdepicts a heating mode of operation. The refrigerant is compressed by the compressorto increase an enthalpy of the refrigerant. The flowof the compressed refrigerant is sent through the four-way valveto the indoor heat exchangervia the line. The refrigerant dissipates heat at the indoor heat exchangerto the indoor airflowthat is supplied to the indoor space or environment being conditioned. The indoor heat exchangerreduces the enthalpy of the refrigerant. After the heat exchange the refrigerant flows in the linevia the flowto the expansion device. The expansion deviceexpands the refrigerant as the flowwithin the lineand the pressure and temperature of the refrigerant are reduced. Optionally, the expansion devicemay be omitted and the pressure and temperature of the refrigerant in the lines,may be equal.

If the pressure within the lineis greater than the biased pressure setting of the check valve, refrigerant flows in the linevia a flowto the ejector. The biased pressure of the check valvemay be set to achieve the desired flow rate of the flowto the ejector. Optionally, the expansion device(when included) and the expansion devicemay be controlled to establish the pressure difference across the check valveand the thus control the amount of the flowinto the ejector.

The flowtransfers the refrigerant through the expansion devicethat expands the refrigerant and reduces the pressure and temperature of the refrigerant for heat exchange in the outdoor heat exchangervia the outdoor airflowestablished by the outdoor fan. In the heating mode, the refrigerant within the outdoor heat exchangeris typically colder than the outdoor environment and thus heat may be transferred into the refrigerant and the enthalpy is increased.

The refrigerant is then transferred in the lineas the flowinto the ejector. In the heating mode, the optional three-way valve(when included, or substituted by an on/off solenoid valve, as discussed above) is closed to the line, and thus substantially all of the flowis directed into the flowand into the ejector. Narrowed orifices within the ejectorfocus and accelerate the flowand reduce the refrigerant pressure within the ejector. The pressure of the refrigerant in the flowis less than the pressure of the refrigerant in the flow, however the operation of the ejectorstill allows mixing and combination of the flows,. As previously described, the accelerated flow and associated pressure drop within the ejectorcreates a lower pressure within the orifice of the ejectorthat may suck in, entrain, and mix the flows,. In this manner, the flow, which has a relatively higher pressure upstream of the ejector, is mixed with the lower pressure flow, and a resulting combined flowhas a relatively intermediate enthalpy that is between the enthalpy of the flows,leading into the ejector. The combined flowthen flows through the offset heat exchangerand exchanges heat with the outdoor airflowin the manner described for the outdoor heat exchanger.

By creating an intermediate enthalpy for the combined flow, the flowthat returns to the compressoris at a higher enthalpy than if the flowreturned to the compressor. Thus by using the ejectoras described, the work input energy of the compressoris less to return the enthalpy of the refrigerant to the initial compressed condition, relative to the work input energy required to compress the flowto the initial compressed condition. Stated alternatively, for a constant amount of compressorwork input, a pressure difference between the input (line) and the output (line) is constant. The compressoroperation thus increases the enthalpy of the refrigerant by a constant magnitude, between the upper and lower pressures of the compressor. The pressure and temperature difference (e.g., an operational range) between the heat exchangers,is set by the upper and lower pressures of the compressorin a standard heating and cooling refrigeration cycle. However, the operational range between the heat exchangers,can be expanded by using the ejectorarrangement described. For example, the outdoor heat exchangercan be operated at a lower pressure (and hence at a lower temperature) than the pressure of the flowinto the compressor, because the ejectorwill maintain the needed pressure of the flowby blending the flows,in the manner previously described. By lowering the operational pressure and temperature of the outdoor heat exchanger, greater enthalpy gains are achieved as more heat energy is absorbed by the refrigerant.

Additionally, a lower temperature for the outdoor heat exchangeralso allows the use of the heat pump HVAC systemin colder environments because heat transfer is still possible when the outdoor heat exchangeris colder than the outdoor ambient temperature. In an example, the heat pump HVAC systemis classified as a CCHP, where the outdoor heat exchangerhas an operational range down to at least 5° F. (−15° C.) ambient temperature. Alternatively, the heat pump HVAC systemis a CCHP, where the outdoor heat exchangerhas an operational range down to at least −15° F. (−26° C.) ambient temperature. Still further, the use of the offset heat exchangerdownstream of the ejectormay be an advantage relative to only using the outdoor heat exchangerbecause the offset heat exchangerreduces the possibility of the compressorflooding by assuring all-vapor conditions along the linereturning the refrigerant to the compressor. Thus the inclusion of the offset heat exchangermay increase the compressoroperational reliability. Furthermore, the inclusion of the offset heat exchangermay also allow for improved or simplified defrosting operation. The in-series arrangement with the outdoor heat exchanger, relative to the outdoor airflow, may result in all or a majority of the frost formation on the offset heat exchangerrather than the outdoor heat exchanger. As the outdoor airflowpasses across the offset heat exchange, a predominant amount of moisture contained in the air will be removed by the offset heat exchanger, leaving a lower humidity content in the outdoor airflowpassing across the outdoor heat exchanger. It should be pointed out that in the heating mode of operation, the refrigerant systemcan optionally operate by bypassing the ejectorby blocking the flowvia the check valveor a solenoid valve (not shown) along the line. When bypassing the ejector, the three-way valvemay also be used to flow the refrigerant along the linevia the bypass flow.

depict a heat pump HVAC system. In general, when in a cooling mode and a heating mode of operation, the refrigerant circuit circulates the refrigerant to perform a vapor compression refrigeration cycle, whereby heat is exchanged at the indoor heat exchangerand an outdoor heat exchanger. The direction of heat transfer for the heat exchangers,is reversed between the cooling and heating modes of operation. In general, some components and the refrigeration circuit of the heat pump HVAC systemare similar to the components and refrigerant circuit of the heat pump HVAC system, and thus the same or similar reference numerals are used. Accordingly, such features will not be described again in detail, except as necessary for the understanding of the heat pump HVAC system. As described further herein the heat pump HVAC systemincludes an internal heat exchangerthat is used in the cooling and heating modes to transfer heat into a vapor injection lineand to a compressor. In addition, the internal heat exchangermay also be configured, in the heating mode, to transfer heat between a lineand a line, which leads into an ejector.

The heat pump HVAC systemofdepicts a cooling mode of operation. The refrigerant circuit of the heat pump HVAC systemrecirculates a refrigerant between the indoor heat exchangerand the outdoor heat exchanger. The refrigerant circuit includes a compressor, a configurable four-way valve, an indoor heat exchanger, an expansion device, a vapor line expansion device, the internal heat exchanger, an ejector, a check valve, a separation tank, an outdoor heat exchanger, an expansion device, and various lines as detailed herein to connect the components of the refrigerant circuit. In a cooling mode, the refrigerant is compressed by the compressorto increase an enthalpy of the refrigerant. A flowof the compressed refrigerant is sent through the four-way valve, through a linevia a flowand to the separation tank. In the cooling mode of operation, the separation tankacts merely as a pass-through for the refrigerant.

Downstream of the separation tank, the refrigerant then flows in a linevia a flowto an expansion device. Substantially all of the flowis directed to the flow. The check valverestricts flow from the pressurized separation tankthrough a line. In the cooling mode of operation, the expansion deviceis fully open and thus does not change the velocity or pressure of the refrigerant flowing therein. The refrigerant then flows into the outdoor heat exchangers, where heat is exchanged with the outdoor environment via an outdoor air flowestablished by an outdoor fan. In the cooling mode, the refrigerant within the outdoor heat exchangeris hotter than the outdoor environment. Thus, heat is transferred away from the refrigerant and the enthalpy of the refrigerant is reduced as part of the vapor compression cycle.

After the outdoor heat exchanger, the refrigerant flows through a linevia a flow, through the internal heat exchanger, through the ejector, and then into a linevia a flowout of the ejector. The lines,are thermally coupled by the internal heat exchanger(e.g., by using counter flow, parallel flow, or combinations thereof through a common thermally conductive material) such that heat may be transferred between the lines,. However, during the cooling mode of operation, the flow through the ejectordoes not substantially change the pressure or the temperature of the refrigerant, thus the lines,are at substantially the same temperature and minimal heat is transferred therebetween in the internal heat exchanger. The ejectoris also connected to the refrigerant circuit at a third position via a line, but substantially no flow of refrigerant is passed within the linebecause the check valveis spring loaded (or otherwise biased) to a closed position. The lineis downstream of the expansion deviceand thus has lower pressure than the separation tank. Therefore, the check valveis also closed in the cooling mode due to a pressure differential across the check valve.

Referring again to the line, downstream of the internal heat exchanger, the flowof refrigerant flows through the expansion deviceinstalled along a lineand expands the refrigerant therein. The expansion of the refrigerant causes a reduced pressure, a reduced temperature, and an associated increased flow rate as shown by a flowdownstream of the expansion device. The expanded and cooled refrigerant of the flowthen passes through the indoor heat exchangerto exchange heat with an indoor airflowestablished by a blower. The enthalpy of the refrigerant is increased as the refrigerant is heated and the air cooled by the indoor heat exchangeris supplied to the indoor space or environment being conditioned. After the heat exchange at the indoor heat exchanger, the refrigerant is evaporated into a gaseous state and then travels back through a line, the four-way valve, and is then sucked back into the compressorto repeat the cycle.

Optionally, the expansion devicecan be replaced by two unidirectional expansion devices, one dedicated to a cooling mode of operation and the other to a heating mode of operation. Optionally, the vapor line expansion devicemay also be coupled to the lineat a position upstream of the expansion device. When the vapor line expansion deviceis opened, the refrigerant from a lineis reduced in pressure and temperature as the refrigerant is expanded into a vapor injection flowvia a vapor injection line. The pressure and temperature of the refrigerant in the vapor injection lineis between the pressures and temperatures of the compressorinlet and outlets via lines,. The vapor injection lineis thermally coupled with the lines,via the internal heat exchangerand thus heat is transferred between lines,and the vapor injection line.

The vapor injection flowis then supplied to the compressorfor internal mixing with the flowof refrigerant downstream of the indoor heat exchanger. The enthalpy of the refrigerant of the vapor injection flowis greater than the enthalpy of the refrigerant of the flow. Thus less work input energy is needed by the compressorto return the refrigerant to the initial conditions for the flow. In this manner, an operational range between the heat exchangers,is expanded as previously described.

Optionally, the ejectormay also include a valve operable to selectively allow the flowto be combined into the flowor a valve to selectively allow flow along the line. Thus, the check valvemay optionally be omitted while still maintaining the functionality described. Optionally, the separation tankmay be placed between the four-way valveand the compressorwithout departing from the principles described herein.

The heat pump HVAC systemofdepicts a heating mode of operation. The refrigerant is compressed by the compressorto increase an enthalpy and pressure of the refrigerant. The flowof the compressed refrigerant is sent through the four-way valveto the indoor heat exchangervia the line. The refrigerant dissipates heat at the indoor heat exchangerto the indoor airflowthat is supplied to the indoor space or environment being conditioned.

After the heat exchange at the indoor heat exchanger, the enthalpy of the refrigerant is decreased and the refrigerant is sent via the lineand the flowto the expansion device. The expansion deviceis fully open in the heating mode and thus does not change the pressure or temperature of the refrigerant flowalong the line.

The refrigerant the flows in the linevia the flowthrough the internal heat exchangerand into the ejector. Narrowed orifices within the ejectorfocus and accelerate the flowand reduce the refrigerant pressure within the ejector. The reduced pressure becomes useful to suck in, entrain, and thus mix flows of low pressure and low temperature refrigerant from the flowwithin the line, as discussed below. The orifices within the ejectorexpand to reduce the refrigerant velocity and increase the pressure and temperature. The pressure within the lineis greater than the biased pressure setting of the check valveand a combined flowtransfers the refrigerant into the separation tank.