Heat Pump Systems with Reheat Features

This application claims priority to and benefit of U.S. provisional patent application No. 63/653,351 filed May 30, 2024, which is herein incorporated by reference in its entirety.

This disclosure relates generally to heat pumps and more particularly to heat pump systems that include de-humidification or a reheat function.

Conventional heat pump systems operating in a humid environment are unable to adequately remove humidity from the air. This deficiency in conventional systems is more pronounced when the heat pump system is operating in a cooling mode. In that mode, conventional systems are unable to effectively control the humidity of the air being circulated in a house, resulting in colder, but humid air. This not only affects the efficiency of the heat pump system, but also results in an unpleasant customer experience.

This disclosure relates generally to vapor compression cycle systems that include a de-humidification or a reheat feature. A “vapor compression cycle system” may broadly encompass any system that is configured to heat and/or cool a conditioned space, heat and/or cool a fluid that is provided to a load, and/or perform any other actions associated with a vapor compression cycle. Non-limiting examples of types of a vapor compression cycle systems can include air conditioners (e.g., no reversing valve, only provides cooling mode), heat pumps (e.g., air source or geothermal; has a reversing valve and operates in both heating and cooling modes), heat pump water heaters, integrated heat pump water heaters, split system heat pump water heaters, heat pump water heaters with a circulation pump and a brazed plate heat exchanger, split systems, packaged systems, mini-splits, PTACs, window units, vertical packaged systems, VRF systems, etc. Reference is made herein to a specific use case in which the vapor compression cycle system is a heat pump system, however, this is not intended to limit the type of vapor compression cycle system to which the configuration described herein may be applicable.

The present disclosure provides various systems and methods for using a reheat feature that can be enabled to remove or control humidity within an indoor space while at the same time keeping the ambient temperature in the indoor space cooler than the external ambient temperature. This improves the overall efficiency of the vapor compression cycle system while saving energy and increasing user comfort.

In regions where it may get extremely hot during some parts of the year, any climate control system operating in a facility, such as a house or a commercial building, often has difficulty maintaining a comfortable temperature within the facility. For example, in regions where the ambient outside temperature goes above 100° F., the climate control system may have difficulty in maintaining a comfortable temperature, such as 68° F., inside a facility. This large difference between the outside temperature and the indoor set point often leads to the climate control system operating for longer periods of time, resulting in more wear and tear on the system, and may even lead to failure in certain conditions. Further, if the hot outside air is coupled with high humidity, such as 90% or above, it becomes difficult to maintain dry conditions within a facility. If the climate control system is operating in a cooling mode, the air provided within the facility may be cooler but is also humid. This is undesirable as cold, humid air results in an unpleasant experience for the occupants of the facility.

In order to reduce the humidity of the air after the air is cooled, the present disclosure provides various systems and methods as described below. One of the techniques is to provide a mechanism for reheating the air after it is cooled using some of the existing refrigerant in the system. This technique of recovering heat from existing refrigerant in order to cool the air on-demand greatly increases the efficiency of the climate control system and also helps in reducing the humidity in the air, thereby providing better comfort to the occupants of the premises.

illustrates a block diagram of a vapor compression cycle systemthat includes a reheat feature according to an embodiment of the present disclosure. For example, the vapor compression cycle systemmay be a heat pump or any other type of vapor compression cycle system described herein or otherwise. It is to be noted that not all components of a heat pump system are illustrated in. Only components for explaining the disclosure are shown. One skilled in the art will realize that a vapor compression cycle system can and does have many more components than what is shown in.

Vapor compression cycle systemincludes a compressor. Compressorhas an intake portand an outlet port. Compressoroperates to receive a fluid (for example, a refrigerant like R134a, R454B, or R410a or the like) and compress it into a high pressure, high temperature vapor. This high temperature, high pressure vapor is then output by compressorvia outlet portto a reversing valve. Reversing valveis in fluid communication with outlet portand inlet portof compressor. “Fluid” as used throughout the specification includes materials in liquid, liquid-vapor mix, and vapor form. For example, fluid may include a refrigerant in its liquid, vapor, or liquid-vapor mix form. “Fluid” can also include air and other types of gases. It should be noted that throughout the disclosure, ports/components described as being in “fluid communication” with each other have one or more refrigerant lines or other appropriate means of fluid communication that facilitate flow of a fluid between these ports/components.

In one embodiment, reversing valveis in fluid communication with 3-way valveand also a first portof a first heat exchanger. In some embodiments, the first heat exchangercan be an indoor heat exchanger that is located within the indoor space being heated or cooled or otherwise in thermal communication (e.g., via one or more air ducts) with an inside ambient environment. Reversing valveoperates in various modes. In one mode (e.g., a cooling mode), it can allow the fluid coming out of compressorto flow to the 3-way valve. The fluid may then flow to a second heat exchanger, and then to a thermostatic expansion (TXV) valveand the first heat exchangerand onwards to compressor intake port. In one embodiment, the thermostatic expansion valvecan be a bi-directional thermostatic expansion valve (TXV), or in another embodiment, two TXVs can be arranged to provide bi-directional control the flow of fluid. The thermostatic expansion valveexpands the fluid passing through it, thereby lowering the pressure of the fluid and converting a small amount of the fluid to vapor form. The fluid that exits the thermostatic expansion valveis in a liquid-vapor mix form.

While described in the example ofas a thermostatic expansion valve, any other expansion device may be used. For example, the thermostatic expansion valvemay be an electronic expansion valve (EXV), capillary tube, or any other refrigerant expansion device or combinations thereof.

The 3-way valve (also referred to herein as “reheat valve”)is in fluid communication with the second heat exchanger. In an embodiment, the second heat exchangercan be an outdoor heat exchanger that is located outside/external to a home/the indoor space or facility that uses vapor compression cycle systemor otherwise in thermal communication (e.g., via one or more air ducts) with an outside ambient environment. The 3-way valveis also in fluid communication with a reheat coil. Details and operation of reheat coilare described below. The 3-way valveis also in fluid communication with reversing valve. In some embodiments, the 3-way valvemay direct the flow of fluid from compressorto reheat coil.

A first portof the second heat exchangeris in fluid communication with the 3-way valve. The second portof the second heat exchangeris in fluid communication with thermostatic expansion valve. The thermostatic expansion valveis in fluid communication with portof the first heat exchanger. The second heat exchangermay be any kind of heat exchanger known in the art or that may fit the purpose and function described below.

In an embodiment, the first heat exchangermay be an indoor heat exchanger located within the facility that uses vapor compression cycle systemor otherwise in thermal communication (e.g., via one or more air ducts) with an indoor ambient environment. The first heat exchangermay be any kind of heat exchanger known in the art or that may fit the purpose and function described below. The second portof the first heat exchangermay be in fluid communication with reversing valve. In addition to being in fluid communication with the thermostatic expansion valve, the portof the first heat exchangeris also in fluid communication with a solenoid valve.

Solenoid valveis located between the portof the first heat exchangerand reheat coil. Solenoid valveis in fluid communication with reheat coilat a first endof the reheat coil. Operation of solenoid valveallows control of the flow of fluid between the first heat exchangerand reheat coilfor use during the reheat operation, if needed. The same endof reheat coilis also in fluid communication with another solenoid valve. The other end of solenoid valveis in fluid communication with a check valve. Check valveallows flow of fluid in only one direction, i.e. from solenoid valvetowards the second heat exchanger. Check valveis in fluid communication with the portof the second heat exchangerat a locationthat is between the 3-way valveand the second heat exchanger.

A first fan unitmay be coupled to the second heat exchanger. A second fan unitmay be coupled to the first heat exchanger. Both the first fan unitand the second fan unitare operable to blow a fluid, such as air, over their respective heat exchangers to either cool or warm the fluid. In one embodiment, reheat coiland the first heat exchangerare placed adjacent to each other such that the first heat exchangeris closer to the second fan unitand an air inlet of an air handler unit, which both the first heat exchangerand reheat coilmay be a part of. In this embodiment, the second fan unitis coupled to both the first heat exchangerand reheat coil. Reheat coilis placed adjacent to but after the first heat exchangersuch that when the second fan unitis in operation, the return air first passes over the first heat exchangerand then over (or otherwise comes in contact with) reheat coil. In this manner, especially in cooling mode with the reheat feature enabled, the air is first cooled by the first heat exchangerand then heated slightly by reheat coilto reduce moisture in the air. This cooler and reduced moisture air is then transported to the indoor space/facility via ducts and the like. After the air passes over reheat coil, it is provided to the premises being served by vapor compression cycle system. The second fan unitthen directs the cooler but drier/lower moisture air to its intended destination via the associated ductwork.

In an embodiment, the vapor compression cycle systemmay include a controller unit. The controller unitmay include one or more processors, one or more memories, and instructions stored in the one or more memories. The instructions when executed by the one or more processors may allow the controller unitto control various aspects of the operation of the vapor compression cycle system. In one embodiment, the controller unitmay communicate with one or more components (e.g., as illustrated in) of the vapor compression cycle systemvia a wired or a wireless communication medium. The controller unitmay be a Direct Digital Control (DDC) type control unit or a non-DDC type control unit. In one embodiment, the controller unitmay receive input from and send instructions to the one or more of the components of the heat pumpillustrated inin order to control the operation of the one or more components. In other embodiments, the controller unitmay be separate from the vapor compression cycle system.

Vapor compression cycle systemmay operate in several modes.illustrate flow charts for the various modes of operation, such as of vapor compression cycle systemof. Each of the modes of operations are described in detail below with reference to the corresponding figures.

illustrates a flow chart for a processof operating a vapor compression cycle system in a first mode according to an embodiment of the present disclosure. For example, processmay be executed by the controller unitduring a heating mode of vapor compression cycle systemof. The details of the processare explained below with reference to both.

At the start of process, the solenoid valveis closed at step. This prevents flow of fluid from reheat coilto the second heat exchangervia solenoid valveand check valve. At step, the 3-way valveis placed in a first state in which it prevents flow of the fluid (e.g., refrigerant) to/from reheat coilto compressor, via the first endof reheat coil. In the first state of the 3-way valve, the fluid is allowed to flow from the second heat exchangerthrough the 3-way valveand reversing valveto the intake portof the compressor.

At step, solenoid valveis opened for a first period of time. In some embodiments, the first time period may be between 5 and 30 seconds depending on the operation and other parameters of vapor compression cycle system. This causes the superheated, high pressure fluid from compressorto flow via reversing valveto the first heat exchanger(e.g., a condenser in the heating mode) and be condensed to a liquid. While the fluid exiting the first heat exchangeris substantially liquid, some small remnant of vapor may be present, as understood by those of ordinary skill in the art. For example, the vapor content of the fluid exiting the first heat exchangermay be less than 1%, less than 5%, less than 10%, or less than 25% of the fluid. Since solenoid valveis open, a portion of the fluid (e.g., liquid refrigerant) flows from the first heat exchangerinto reheat coilat step. Since solenoid valveis closed and the 3-way valveis in the first state, the portion of the fluid in reheat coilhas nowhere to go and stored in the reheat coil. In some embodiments, the portion of fluid in reheat coilhas a first temperature that is higher than the temperature of the portion of fluid in the second heat exchanger. In an embodiment, the temperature of the portion of the fluid in reheat coilcan be above 80° F. Also, the portion of the fluid in reheat coilis at a higher pressure, such as 350 psi.

At step, the rest of the fluid output from compressorflows through the first heat exchanger, the thermostatic expansion valve, the second heat exchanger, the 3-way valve, and the reversing valve, and enters compressorat the intake. It should be noted that while the 3-way valveprevents the flow of fluid from reheat coilto compressor, it allows flow of fluid from the second heat exchangerto compressor. At step, solenoid valveis closed after expiration of the first time period. From then on, for the rest of the time that heat pump system is operating in the heating mode, solenoid valveremains closed and the fluid circulation continues from compressor, to the first heat exchanger, to thermostatic expansion valve, to the second heat exchanger, via the 3-way valveand reversing valve, back to compressor.

In some embodiments, the filling up of reheat coilwith fluid from compressorin the manner described above is done once, during the winter season, when the vapor compression cycle systemis first put in a heating mode. Thereafter, the heat pump system can keep running in the heating mode. This extra fluid stored in reheat coilreduces the amount of refrigerant flowing in the vapor compression cycle systemwhen it is operating in the heating mode. Thus, the reheat coilis used to store refrigerant in the heating mode as the heat pump system can operate with less refrigerant in the heating mode than in the cooling mode.

illustrates a processthat can occur during operation of vapor compression cycle systemofin a second mode (e.g., a cooling mode) according to another embodiment of the present disclosure. In an embodiment, processmay be executed by the controller unitillustrated in. For example, processillustrates operation of the heat pump system in a cooling mode without the reheat feature enabled. For example, the cooling mode without reheat may be used when it is desired for a facility to be cooled and the humidity in the ambient air is low enough so that vapor compression cycle systemoperates efficiently. For example, hotter, but drier climate regions would likely benefit more from this mode of operation. The details of the processare explained below with reference to both.

At step, solenoid valveis opened. In instances where a prior mode of operation causes solenoid valveto remain open, then valvecan be left open for the purposes of process. In other instances, even if solenoid valveis open prior to the beginning of process, it can be closed and then reopened as part of step.

At step, solenoid valveis closed. In instances where solenoid valveis already closed prior to step, it is verified that the valve is indeed closed. At step, the 3-way valveis placed in the first state such that it prevents flow of fluid to/from compressorto reheat coilvia the second endof reheat coil. However, in the first state, the 3-way valveallows flow of fluid from compressorto the second heat exchanger(e.g., a condenser in the second mode).

At step, vapor compression cycle systemcauses flow of fluid from compressor, via the 3-way valve, to the second heat exchangerand onwards to the first heat exchangervia thermostatic expansion valve. The fluid then continues to flow from the first heat exchanger(e.g., an evaporator in the second mode) back to compressor via reversing valve.

At step, the portion of fluid stored in reheat coilalso flows to compressor via the first heat exchangerto improve heat exchange capability. This occurs due to the following reasons. One, since solenoid valveis open the fluid can flow from reheat coilto the first heat exchangervia the endof the reheat coil. Second, the pressure inside the first heat exchangeris lower than the pressure in the reheat coil. This pressure imbalance causes the fluid to flow into the first heat exchanger. In addition to the above, compressoris also exerting a pull/suction force on the fluid. The vapor compression cycle systemthen continues to run in this cooling mode until another change to its mode of operation is triggered.

In some embodiments, a portion of fluid may be stored in reheat coilprior to the start of process, for example, using one or more actions described above in connection with process. For example, steps-may be executed prior to executing the steps of process.

In environments where the ambient air is hot and carries a lot of moisture, it is desirable to also lower/remove the amount of moisture in the air in addition to cooling the air so that the facility/premises being cooled has a pleasant environment and vapor compression cycle systemoperates efficiently while not excessively cooling the moisture-laden air.

illustrates a processfor operating vapor compression cycle systemofin a third mode according to yet another embodiment of the present disclosure. In an embodiment, processmay be executed by the controller unitillustrated in. For example, the third mode can be referred to as cooling mode with reheat feature enabled. At a high-level, this mode operates to both cool the air as well as remove the moisture from the cooled air by cooling air with the first heat exchangerto a first temperature to remove a desired amount of moisture and subsequently slightly raising the air to a second temperature with the reheat coilafter it passes the first heat exchanger. The details of the processare explained below with reference to both.

In an embodiment, processmay be preceded by one or more steps of process. For example, one or more of steps,,, andmay occur before processbegins such that a portion of fluid is already stored in reheat coilprior to the beginning of process. In other embodiments, other actions may occur that cause a portion of fluid from the compressorto be stored in reheat coil.

At step, solenoid valveis closed. This prevents fluid that is inside the reheat coilfrom flowing to/from the first heat exchanger. At step, solenoid valveis opened. This allows fluid stored in reheat coilto flow via check valveto the second heat exchanger.

At step, the 3-way valveis placed in a second state such that it allows flow of fluid from compressorto reheat coilvia the 3-way valve. Further, in the second state, the 3-way valveprevents flow of fluid from the output of check valveto compressorvia the 3-way valve.

At step, fluid from compressorflows through the reversing valveand to reheat coilvia the 3-way valve. It is to be noted that the fluid coming out of the compressor is superheated and at high pressure.

Concurrently, the second fan unitis circulating/traversing a second fluid, such as air, over the first heat exchanger. The first heat exchangercools and dehumidifies the air, and reheat coilslightly heats up the cooled and dehumidified air. The air is then collected after it is slightly heated by reheat coiland provided to the facility/space that is coupled to vapor compression cycle system. For example, for a setting of 70° F., the air may be cooled to around 50-55° F. and dehumidified by the first heat exchangerand then heated by reheat coilto around 65-68° F., to get it closer to or about the setting/desired temperature. Thus, the temperature of air leaving the first heat exchangeris lower than the temperature of air after it is heated by reheat coil.

At step, the fluid that is in the reheat coilflows to the second heat exchanger(e.g., a condenser in the third mode) via the valve. At step, the same first portion of the fluid flows from the second heat exchanger, via the thermostatic expansion valve, to the first heat exchanger first(e.g., an evaporator in the third mode) and onwards back to compressor. This flow of the fluid continues in this fashion while the vapor compression cycle systemis operated in this cooling with reheat mode.

It should be noted that, as used in the specification and the appended claims, the singular forms “a,” “an,” and “the” include plural references unless the context clearly dictates otherwise. References to a composition containing “a” constituent is intended to include other constituents in addition to the one named.

Also, in describing the disclosed technology, terminology will be resorted to for the sake of clarity. It is intended that each term contemplates its broadest meaning as understood by those skilled in the art and includes all technical equivalents which operate in a similar manner to accomplish a similar purpose.

Ranges may be expressed herein as from “about” or “approximately” or “substantially” one particular value and/or to “about” or “approximately” or substantially” another particular value. When such a range is expressed, the disclosed technology can include from the one particular value and/or to the other particular value. Further, ranges described as being between a first value and a second value are inclusive of the first and second values. Likewise, ranges described as being from a first value and to a second value are inclusive of the first and second values.

Herein, the use of terms such as “having,” “has,” “including,” or “includes” are open-ended and are intended to have the same meaning as terms such as “comprising” or “comprises” and not preclude the presence of other structure, material, or acts. Similarly, though the use of terms such as “can” or “may” are intended to be open-ended and to reflect that structure, material, or acts are not necessary, the failure to use such terms is not intended to reflect that structure, material, or acts are essential. To the extent that structure, material, or acts are presently considered to be essential, they are identified as such.

It is also to be understood that the mention of one or more method steps does not preclude the presence of additional method steps or intervening method steps between those steps expressly identified. Moreover, although the term “step” can be used herein to connote different aspects of methods employed, the term should not be interpreted as implying any particular order among or between various steps herein disclosed unless and except when the order of individual steps is explicitly required. Further, the disclosed technology does not necessarily require all steps included in the methods and processes described herein. That is, the disclosed technology includes methods that omit one or more steps expressly discussed with respect to the methods described herein.

It should be apparent that the foregoing relates only to certain embodiments of the present disclosure and that numerous changes and modifications may be made herein by one of ordinary skill in the art without departing from the general spirit and scope of the disclosure.

Although specific embodiments of the disclosure have been described, numerous other modifications and alternative embodiments are within the scope of the disclosure. For example, any of the functionality described with respect to a particular device or component may be performed by another device or component. Further, while specific device characteristics have been described, embodiments of the disclosure may relate to numerous other device characteristics. Further, although embodiments have been described in language specific to structural features and/or methodological acts, it is to be understood that the disclosure is not necessarily limited to the specific features or acts described. Rather, the specific features and acts are disclosed as illustrative forms of implementing the embodiments. Conditional language, such as, among others, “can,” “could,” “might,” or “may,” unless specifically stated otherwise, or otherwise understood within the context as used, is generally intended to convey that certain embodiments could include, while other embodiments may not include, certain features, elements, and/or steps. Thus, such conditional language is not generally intended to imply that features, elements, and/or steps are in any way required for one or more embodiments.