Patent Application
20240110733
This invention pertains to packaged air source heat pump units and packaged water source heat pump units. In particular, the invention concerns a refrigerant charge control system that controls the amount of refrigerant being used in the main refrigerant loop during a cooling cycle and/or a heating cycle in the units, whereby the amount of refrigerant in the main refrigerant loop is different when comparing the cooling cycle and heating cycle modes. The invention also concerns refrigerant systems that provide reheat function during cooling mode.
A packaged heat pump unit typically comprises the following major components: compressor, reversing valve, and at least two heat exchangers with expansion valves. One of the heat exchangers is present on the indoor side and is used to regulate the heat inside a building space while the other heat exchanger is exposed to the outdoor ambient conditions. All the components of the heat pump unit are connected to form a closed loop. A refrigerant is circulated within the closed loop, which allows for the transfer of heat from the internal space to the ambient and vice versa. The heat pump system utilizes a refrigeration cycle when operating to heat or cool a building space.
A heat pump unit is said to be operating in AC (air conditioning) or cooling mode when the indoor heat exchanger acts as an evaporator and cools a stream of air that is delivered to the internal building space. During this mode, super-heated and compressed refrigerant vapor from the compressor is directed to the outdoor heat exchanger through the reversing valve. The outdoor heat exchanger acts as a condenser to reject the heat from the refrigerant vapor to the outdoor ambient. The refrigerant is cooled and changes phase to a saturated liquid when passing through the expansion valve. This refrigerant is then fed to the indoor heat exchanger and finally back to the compressor to complete the refrigeration cycle. During the heating or heat pump mode, the reversing valve changes the direction of refrigerant flow wherein the super-heated refrigerant vapor from the compressor is directed to the indoor heat exchanger which now acts as a condenser and heats the oncoming air stream that is sent to the internal building space.
In a typical heat pump unit, an additional hot-gas heat exchanger can be added downstream to the indoor heat exchanger. As the air-conditioned ambient space is getting cooled, the relative humidity levels as well as the temperature decrease. If the target temperature is achieved but the target humidity level is not, the hot gas heat exchanger is activated to reheat the air stream and thereby remove excess humidity in the cooling space while delivering close to neutral air to prevent over cooling the space. When activated, the super-heated refrigerant vapor from the compressor is directed first to the hot gas heat exchanger and then resumes the similar path to the outdoor heat exchanger as in the regular cooling mode. This mode of operation is termed as hot-gas reheat mode.
Depending on the heat sources/heat sinks used, the heat pump systems are termed as Air source heat pump (ASHP) systems and Water source heat pump (WSHP) systems. ASHP units utilize a blower fan to facilitate the heat transfer from the heat exchanger to the outdoor ambient, and WSHP units utilize a heat exchanger that directly exchanges heat between the refrigerant and water/brine mixture. The water/brine mixture is available as a stable thermal source either in the form of a closed loop piping system or by directly pumping well water.
In a packaged heat pump system, a WSHP unit generally employs a plate heat exchanger in the outdoor side of the unit while a fin-tube heat exchanger is used in the case of an ASHP unit. The total quantity of the refrigerant present in the closed loop (circuit) is usually fixed. A greater amount of refrigerant is required for an ASHP during cooling mode and for a WSHP during heating mode. Hence, when the cycle reverses, the excess refrigerant will result in flooding of the heat exchanger and causes very high discharge pressure at the compressor. Due to the high discharge pressure, the airflow over the condenser may not be significantly reduced to minimize sound levels with lower airflows, meaning that the unit is very noisy to during operation. A condition known as refrigerant flooding generally occurs during the heating cycle of an ASHP and during the cooling cycle of a WSHP. During refrigerant flooding, heat exchange is less efficient, which causes excessive compressor discharge pressure which may cause pressure limits to trip and the compressor may cease to operate. In the case of the air source heat pump unit (ASHP), the outdoor coil is generally larger compared to the indoor coil. Hence the ASHP system would require more refrigerant volume when operating in the cooling mode when the outdoor coil acts as a condenser. During heating mode when the indoor coil takes the role as a condenser a relatively lower volume of refrigerant is required to maintain an optimum performance and sound levels. In the case of a water source heat pump system (WSHP), the outdoor heat exchanger is generally much smaller and compact compared to the indoor coil. In regular cooling mode the outdoor heat exchanger would require a fraction of the total volume of the refrigerant in the unit.
It is an object of the invention to provide a heat pump unit that overcomes one or more of the disadvantages of prior art heat pump units. The current invention seeks to reduce the occurrence of or avoid the occurrence of refrigerant flooding during the heating cycle of an ASHP unit or during the cooling cycle of a WSHP unit. It is another object of the invention to provide a heat pump unit that employs (operates with) a reduced amount of refrigerant in the main refrigerant system during either the heating cycle or the cooling cycle. It is another object of the invention to provide an ASHP unit that employs (operates with) a smaller amount of refrigerant in the main refrigerant system during the heating cycle as compared to during the cooling cycle. It is another object of the invention to provide a WSHP unit that employs (operates with) a smaller amount of refrigerant in the main refrigerant system during the cooling cycle as compared to during the heating cycle.
An aspect of the invention provides a heat pump unit that operates with a first amount of refrigerant in the main refrigerant system during a cooling or heating cycle and a smaller second amount of refrigerant in the main refrigerant system during a heating or cooling cycle, respectively, wherein the total amount of refrigerant in the heat pump unit is fixed.
The invention also provides heat pump unit that distributes its total charge of refrigerant between a main refrigerant system and a refrigerant charge control system conductively engaged to the main refrigerant system, wherein the total charge of refrigerant in the heat pump unit is constant. In some embodiments, the heat pump unit distributes its total charge of refrigerant between a main refrigerant system, a refrigerant charge control system conductively engaged to the main refrigerant system, and a hot gas reheat system conductively engaged to the main refrigerant system, wherein the total charge of refrigerant in the heat pump unit is constant.
The heat pump unit of the invention comprises a refrigerant charge control system in the closed loop circuit. The charge control system acts as a reservoir to trap excess refrigerant during the heating cycle in the case of an ASHP unit and during cooling cycle in the case of WSHP unit. This prevents the heat exchangers from experiencing refrigerant flooding and improves the efficiency and sound levels of the unit.
The invention also provides a heat pump unit comprising:
A hot gas reheat system can be conductively engaged to the main refrigerant system.
The invention also provides a heat pump unit comprising:
The invention also provides an air source heat pump unit comprising:
The invention also provides a water source heat pump unit comprising:
The invention also provides a heat pump unit comprising:
The invention also provides a heat pump unit comprising:
Embodiments of the invention include those wherein: a) the heat pump unit is an air source heat pump unit, the at least one high pressure heat exchanger is an outdoor heat exchanger, and the low pressure heat exchanger is an indoor heat exchanger; b) the heat pump unit is a water source heat pump unit; the at least one high pressure heat exchanger is an indoor heat exchanger, and the low pressure heat exchanger is an outdoor heat exchanger; c) the refrigerant charge control system comprises at least the following conductively engaged components: at least one refrigerant reservoir, at least one flow control valve, and at least one check valve; d) the heat pump unit is a packaged, air source or water source heat pump unit; e) the heat pump unit is adapted to cool or heat air or water; f) the heat pump unit further comprises at least one blower fan; or g) a combination of two or more of the above.
Accordingly, a heat pump unit of the invention comprises: a) a refrigerant charge control system comprising at least one refrigerant reservoir, at least one first flow control valve, e.g. solenoid valve, pneumatically actuated valves including butterfly valves, ball valves, gate valves, globe valves, needle valve, diaphragm valves, angle valves, plug valves or other such valves, and at least one first check valve; and b) plural components selected from the group of at least one compressor, at least one higher pressure heat exchanger, e.g. fin and tube, shell and tube, plate and frame, Immersion plate, spiral-helical coil, spiral coil, slinky type, co-axial tube, graphite block, or other such heat exchangers, at least one lower pressure heat exchanger, plural conduits, at least one second check valve, at least one second flow control valve (ON/OFF valve), at least one reversing valve, and at least one expansion valve (e.g. electronically controlled, spring controlled, or orifice), wherein the refrigerant charge control system controls the amount of refrigerant distributed between the refrigerant charge control system and the plural components.
The invention provides a heat pump unit wherein the total amount of refrigerant in a heat pump unit (RFtotal) is constant (fixed) and equals the sum of the amount of refrigerant in a refrigerant charge control system (RFRCC) and the amount of refrigerant in the remaining conduits and components (or at least the primary (main) refrigerant system (loop)) (RFcon) in the heat pump unit: RFtotal=RFRCC+RFcon.
The heat pump unit of the invention, optionally, further comprises a separate hot gas reheat cycle system comprising a separate line from the compressor discharge activated by the solenoid valve to ensure the super-heated refrigerant vapor enters the hot gas reheat coil to dehumidify the incoming stream of cold air from the indoor coil. The hot gas reheat cycle then follows the circuit (closed loop) as a regular cooling cycle. The refrigerant charge control system can be active (operating) during the hot-gas reheat cycle.
A refrigerant charge control system may serve as a refrigerant temporary storage system to compensate for the excess refrigerant in heating/cooling cycle depending on the type of heat pump system, as described above. The flow of refrigerant through the charge control system is generally unidirectional, and the refrigerant charge control system is conductively connected (engaged) with the main (primary) refrigerant loop (plural conduits). The main refrigeration loop also comprises a compressor, indoor heat exchanger, outdoor heat exchanger, and optionally a hot gas heat exchanger, at least one expansion valve, and at least one reversing valve.
As described above for known heat pump units, especially in the case of the air source heat pump unit (ASHP), the inner volume of the outdoor heat exchanger is generally larger compared to the inner volume of the indoor heat exchanger. Hence the ASHP system would require more refrigerant volume when operating in the cooling mode when the outdoor heat exchanger acts as a condenser. During heating mode when the indoor heat exchanger takes the role as a condenser a relatively lower volume of refrigerant is required to maintain an optimum performance and sound levels. In order to overcome the disadvantage of known systems, the present invention comprises a refrigerant reservoir as part of a refrigerant charge control system installed between the indoor heat exchanger and the reversing valve. An outlet pipe from the indoor heat exchanger is connected to one end of the reservoir, of the refrigerant charge control system, through a solenoid valve which when activated during the heating mode to allow a predetermined amount of refrigerant to be collected. The predetermined amount of refrigerant was empirically determined based on charge levels required for optimum capacity and efficiency between the cooling and heating mode. The refrigerant reservoir comprises at least one outlet that is connected to the main refrigerant loop to direct the flow of refrigerant to the outdoor heat exchanger through at least one one-way valve. When the cycle changes to cooling mode, the excess refrigerant from the reservoir is migrated (returned) back to the main refrigerant loop and to the outdoor heat exchanger.
The reservoir comprises at least one container (tank, receptacle) adapted to temporarily retain (store or hold) a predetermined amount of refrigerant, meaning the container has a predetermined storage capacity. In some embodiments, the at least one container is a cylinder adapted to hold a predetermined amount of refrigerant. The reservoir is, optionally, placed in the lowest physical position in the heat pump unit to allow the refrigerant to collect in the reservoir through the use of gravity. The refrigerant may also be transported to the reservoir through the use of a series of one or more control valves, one or more orifices, one or more expansion devices, one or more check valves and/or one or more refrigerant pumps. In some embodiments, the refrigerant reservoir is physically placed such that it resides at a lower elevation than the heat pump unit. In other embodiments, the refrigerant reservoir is placed at higher or equal elevations than the heat pump unit through the use of one or more check valves, and/or one or more refrigerant pumps.
At least one flow control (ON/OFF) valve, as already described herein, is placed before the refrigerant reservoir input, meaning between the indoor heat exchanger and the refrigerant reservoir. Refrigerant is collected within the reservoir when the flow control valve is open. The flow control valve is open for at least a majority of, and preferably the entire, duration of the heating cycle in the case for the ASHP unit. At least one check valve can be included in the charge control system to promote one-directional (unidirectional) flow of refrigerant from the reservoir back to main refrigerant loop. The reservoir further comprises at least one outlet and at least one suction line conductively engaged with the indoor heat exchanger, wherein low pressure occurring in the indoor heat exchanger during the cooling cycle in the ASHP unit forces, (draws, pulls) the refrigerant from the reservoir tank back to the main line. The system further comprises at least one check valve downstream of the reservoir and upstream of the indoor heat exchanger to prevent the refrigerant from returning back to the reservoir tank through the suction line of the reservoir.
As described above for known heat pump units, especially in the case of a water source heat pump system (WSHP), the outdoor heat exchanger is generally smaller and more compact compared to the indoor heat exchanger. During the regular cooling mode, the outdoor heat exchanger generally requires a fraction of (less than) the total amount of refrigerant in the unit. For a WSHP system according to the invention, excess refrigerant is collected in the charge control system during the cooling mode. The WSHP comprises at least one flow control valve (as already described herein) upstream of the inlet of the reservoir, which valve is kept open during the entire (or at least majority of) duration of the cooling mode, to allow excess refrigerant to be collected in the reservoir. The reservoir comprises at least one outlet conductively engaged with at least one suction line, which is conductively engaged with the outdoor heat exchanger, wherein low pressure occurring in the outdoor heat exchanger during the heating cycle in the WSHP unit forces (draws, pulls) the refrigerant from the reservoir tank back to the main line. The system further comprises at least one check valve downstream of the reservoir and upstream of the outdoor heat exchanger to prevent the refrigerant from returning back to the reservoir tank through the suction line of the reservoir
In some embodiments, the heat pump unit of the invention further comprises at least one hot gas reheat system comprising at least one hot gas heat exchanger, e.g. fin-tube, shell-tube, or coil. In such embodiments, the hot gas heat exchanger is placed downstream of the indoor heat exchanger. In addition to the cooling mode of operation and the heating mode of operation, such heat pump units comprise a separate third mode of operation termed a “hot gas reheat mode”, which operates when active de-humidification of process air is necessary. During the hot-gas reheat mode, refrigerant from the compressor discharge (outlet) is directed towards the hot gas heat exchanger. After passing through the hot gas heat exchanger, the refrigerant returns to the main refrigerant loop for use during a regular cooling cycle. Hence, during hot gas reheat mode, the excess refrigerant is discharged from the reservoir back to the main refrigerant loop in the case of ASHP unit, while the excess refrigerant is collected in the reservoir in the case of WSHP unit. The hot gas reheat system is active only during the hot gas reheat cycle when it actively reheats the air, or water. During a regular cooling cycle, the hot gas heat exchanger remains inactive. In some embodiments, the hot gas reheat system comprises at least one flow control valve upstream of the hot gas heat exchanger and downstream of the indoor heat exchanger. The valve is closed during at least a majority of or during the entire regular cooling cycle and heating cycles. The hot gas cycle generally does not occur during regular cooling and heating cycles but can or does activate during oil return cycles. This prevents the hot gas heat exchanger coil from being flooded with refrigerant during cooling and heating cycles. Any excess refrigerant present in the hot gas heat exchanger is generally drawn back to the main loop gradually during unit cooling or heating operation.
When a hot gas reheat system is present, the total charge of refrigerant in the heat pump unit (RFtotal) equals the sum of the amount of refrigerant in the refrigerant charge control system (RFRCC) plus the amount of refrigerant in the hot gas reheat system (RFHGR) plus the amount of refrigerant in the remaining conduits and components (RFcon): RFtotal=RFRCC+RFHGR+RFcon.
In some embodiments, a heat pump unit of the invention comprises at least one refrigerant charge control system and a main refrigerant loop (system), wherein the at least one refrigerant charge control system comprises at least one refrigerant reservoir, and the at least one refrigerant charge control system controls distribution of refrigerant in the heat pump unit between the at least one refrigerant reservoir and the main refrigerant loop, whereby the heat pump unit employs a first amount of refrigerant during a cooling or heating cycle and a smaller second amount of refrigerant during a heating or cooling cycle, respectively, and wherein the total amount of refrigerant in the heat pump unit is fixed (constant). More specifically, the heat pump unit of the invention distributes its total charge (amount) of refrigerant according to the following formulas:
cooling cycle RFtotal=heating cycle RFtotal=constant value for a given unit;
RFtotal=RFRCC+RFcon, when refrigerant charge control system and additional conduits and components are present and hot gas reheat system is absent;
RFtotal=RFRCC+RFHGR+RFcon, when refrigerant charge control system, hot gas reheat system, and additional conduits and components are present.
For an ASHP unit, the heating cycle RFcon<cooling cycle RFcon, whereby the ratio of cooling cycle RFcon to heating cycle RFcon>1. This means that heating cycle RFcon=cooling cycle RFcon−RFRCC, for an ASHP unit.
For a WSHP unit, the heating cycle RFcon>cooling cycle RFcon, whereby the ratio of cooling cycle RFcon to heating cycle RFcon<1. This means that cooling cycle RFcon=heating cycle RFcon−RFRCC, for a WSHP unit.
The invention also provides method of operating an air source heat pump unit comprising:
The invention also provides method of operating a water source heat pump unit comprising:
The methods of the invention can further comprise: during a hot gas reheat cycle of the heat pump unit, directing a portion of refrigerant away from the main refrigerant system through a hot gas heat exchanger and back to the main refrigerant system.
In some embodiments of a heat pump unit comprising a main refrigerant system, the invention also provides a refrigerant charge control system conductively engaged to the main refrigerant system and comprising: at least one reservoir; at least one check valve; and at least one flow control valve. Embodiment of the invention include those wherein: a) the check valve is downstream of the reservoir, and the reservoir is downstream of the flow control valve; and/or b) the flow of refrigerant through the refrigerant charge control system is unidirectional.
The invention includes all combinations of the aspects, embodiments and sub-embodiments disclosed herein. Other features, advantages and embodiments of the invention will become apparent to those skilled in the art by the following description, accompanying examples and appended claims.
The following drawings are part of the present specification and are included to further demonstrate certain aspects of the invention. The invention may be better understood by reference to one or more of these drawings in combination with the detailed description of the specific embodiments presented herein.
With reference to the drawings (
The heating cycle in the ASHP unit is depicted in
With reference to
Conversely, during the heating cycle in the WSHP unit, the flow control valve (31) is closed (see
The refrigerant charge control system functions to remove the excess refrigerant in the main refrigerant loop during the heating cycle in the case of ASHP unit and during the cooling cycle in the case of WSHP unit. It also increases the amount of refrigerant in the main refrigerant loop during the cooling cycle in the case of ASHP unit and during the heating cycle in the case of WSHP unit, respectively.
When charging (collecting) refrigerant in the reservoir by gravity feed, it is preferable to place the reservoir at a vertical position that is relatively lower than (below) most or all of the other components conductively engaged with the main refrigerant loop. In other words, the reservoir would be placed such that at least a major portion of, or all, of its volume (or of its charge of refrigerant) is placed at a relative height that is below the indoor heat exchanger, outdoor heat exchanger, hot gas heat exchanger, filter drier and at least a majority of the remaining volume of the conduits of the main refrigerant loop.
In some embodiments, the entire charge of refrigerant in the heat pump unit is dividable into at least to portions: a first portion of refrigerant in the main refrigerant loop and a second portion of refrigerant in the RCC system (inclusive of the reservoir and respective conduit(s) and components thereof).
In some embodiments, at least a majority of the refrigerant in the RCC system is vertically lower than at least a majority of the charge of refrigerant in the main refrigerant loop (which comprises components and conduit(s) that are not part of the RCC system).
The heat pump unit is designed such that during a first mode of operation a majority of refrigerant charge in the heat pump unit is present in the main refrigerant loop and little to no refrigerant is in the RCC and during a second mode of operation a significant portion of refrigerant is still in the main refrigerant loop and a substantial portion of refrigerant is in the RCC. For example, during a first mode of operation at least 50%, at least 60%, at least 70%, at least 80%, at least 90%, at least 95%, at least 97%, at least 98%, at least 99% of the entire charge of refrigerant is in the main refrigerant loop, with the remainder, if any, being present in the RCC system. Then during a second mode of operation not more than 1%, not more than 2%, not more than 5%, not more than 7.5%, not more than 10%, not more than 20%, not more than 25%, not more than 30%, not more than 35%, not more than 40%, or not more than 50% of the entire charge of refrigerant is in the RCC system.
In some embodiments, the RCC reservoir is located at a height that is at or near the lowest point of the heat pump unit so that the refrigerant is collected to its full capacity. Referring to
The reservoir of the RCC can be any container that can safely retain a charge of pressurized refrigerant (in either liquid or vapor form). The reservoir of
In some embodiments, the heat pump unit comprises a hot gas reheat system comprising at least a flow control valve, and a hot gas heat exchanger.
A hot gas reheat (HGRH) dehumidification mode is enabled when there is a call for dehumidification during cooling mode. In HGRH mode, the unit is not actively involved in heating or cooling. The mode of operation of ASHP and WSHP unit during hot gas reheat mode can be referred in
Although the present invention and its advantages have been described here in detail, it should be taken into consideration that there will several variations in the unit, alterations and minor changes that can be made herein without departing from the scope of the invention as defined by the claims. For example, although the cross-sectional views of ASHP and WSHP packaged units as shown in
All values disclosed herein may have standard technical measure error (standard deviation) of ±10%. The term “about” is intended to mean±10%, ±5%, ±2.5% or ±1% relative to a specified value, i.e. “about” 20% means 20±2%, 20±1%, 20±0.5% or 20±0.25%.
The above is a detailed description of particular embodiments of the invention. It will be appreciated that, although specific embodiments of the invention have been described herein for purposes of illustration, various modifications may be made without departing from the spirit and scope of the invention. Accordingly, the invention is not limited except as by the appended claims. All embodiments disclosed and claimed herein can be made and executed without undue experimentation in light of the present disclosure.
This application claims the benefit of and is a division of application Ser. No. 16/456,140, filed Jun. 28, 2019, which claims the benefit of application No. 62/699,052 filed Jul. 17, 2018, the entire disclosures of which are hereby incorporated by reference.
| Number | Date | Country | |
|---|---|---|---|
| 62699052 | Jul 2018 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 16456140 | Jun 2019 | US |
| Child | 18532750 | US |
