Patent Application
20250052459
The present invention relates generally to heat pump systems and more particularly, but not by way of limitation, to a method of and system for reducing compressor discharge temperature and recovery of compressor heat loss using liquid refrigerant.
Heat pump systems running in a heating mode and operating in cold climate at temperatures less than, for example, −15° C., operate with lower evaporating temperatures resulting in drastic reduction in a capacity of the heat pump system due to less mass flow rate for a same volume flow rate of a compressor. In such situations, the compressor operates near a high compression ratio (HCR) region of an operating envelope of the compressor (i.e., minimum evaporating and maximum condensing temperatures) where the compressor discharge temperature and/or the temperature of a compressor shell is generally higher. In order to maximize compressor capacity, the compressor is required to operate at maximum compressor speed with high mass flow rate resulting in an increase in, for example, compressor noise, compressor discharge temperature and temperature of the compressor shell. In an effort to suppress the compressor noise, acoustic jackets are placed around the compressor. While the acoustic jacket suppresses the compressor noise, the acoustic jacket works as a thermal insulator limiting heat generated by the compressor to escape thereby increasing the compressor discharge temperature. As a result, the compressor discharge temperature reaches an operating threshold limit shutting off the compressor and preventing continuous operation. To reduce the compressor discharge temperature, various conventional methods are used such as, for example, vapor or liquid injection in the heat pump systems. However, more desirable solutions are needed to reduce the compressor discharge temperature.
This summary is provided to introduce a selection of concepts that are further described below in the detailed description. This summary is not intended to identify key or essential features of the claimed subject matter, nor is it to be used as an aid in limiting the scope of the claimed subject matter.
A heat pump system includes an evaporator coil, a condenser coil coupled to the evaporator coil to permit a refrigerant to cycle between the evaporator coil and the condenser coil via a first valve and a compressor coupled between the evaporator coil and the condenser coil. The heat pump system further includes a reversing valve configured to reverse a direction of flow of the refrigerant through the heat pump system and a refrigerant redirection circuit configured to redirect a portion of the refrigerant around the compressor to absorb heat and lower a compressor discharge temperature.
A heat pump system includes an evaporator coil, a condenser coil coupled to the evaporator coil to permit a refrigerant to cycle between the evaporator coil and the condenser coil via a first valve and a compressor coupled between the evaporator coil and the condenser coil. The heat pump system further includes a reversing valve configured to reverse a direction of flow of the refrigerant through the heat pump system and a refrigerant redirection circuit. The refrigerant redirection circuit includes a second valve, a third valve and a plurality of coils wrapped around the compressor. The second valve is configured to regulate a portion of the refrigerant to the plurality of coils wrapped around the compressor via the third valve to absorb heat and lower a compressor discharge temperature.
A method of lowering a discharge temperature of a compressor for a heat pump system, the method includes operating the heat pump system in a heating mode, circulating refrigerant to cycle between an evaporator coil and a condenser coil via a first valve, reversing, using a reversing valve, a direction of flow of the refrigerant through the heat pump system and redirecting, using a refrigerant redirection circuit, a portion of the refrigerant around the compressor to absorb heat and lower the discharge temperature.
For a more complete understanding of the present invention and for further objects and advantages thereof, reference may now be had to the following description taken in conjunction with the accompanying drawings in which:
Various embodiments of the present invention will now be described more fully with reference to the accompanying drawings. The invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein.
Heat pump systems typically include an exterior coil that operates as an evaporator coil and an interior coil that operates as a condenser coil. For the purposes of this application, the term “evaporator coil” is used to refer to the exterior coil and the term “condenser coil” is used refer the interior coil irrespective of the operating mode being described unless specifically stated otherwise.
Referring now to
The refrigerant flows through the heat pump system 100 in a continuous heating cycle. Starting from the evaporator coil 102, an outlet 103 of the evaporator coil 102 is coupled to a suction line 106 of the compressor 108 via the reversing valve 104 to feed the refrigerant to the compressor 108. The compressor 108 compresses the refrigerant. A discharge line 110 feeds the compressed refrigerant from the compressor 108 through the reversing valve 104 to the condenser coil 112. In the heat pump configuration, refrigerant traveling from the condenser coil 112 flows through a first valve 120 and is directed to the evaporator coil 102. In a typical embodiment, the first valve 120 may be, for example, thermostatic expansion valve or a throttling valve that is configured to reduces a pressure of the refrigerant as it enters the evaporator coil 102 and the heating cycle begins again. The behavior of the refrigerant as it flows through heat pump system 100 is discussed in more detail below.
During operation of the heat pump system 100, low-pressure, low-temperature refrigerant is circulated through the evaporator coil 102. The refrigerant is initially in a liquid/vapor state. In a typical embodiment, the refrigerant is, for example, R-22, R-134a, R-410A, R-744, or any other suitable type of refrigerant as dictated by design requirements. Ambient air from the environment surrounding the evaporator coil 102, which is typically warmer than the refrigerant in the evaporator coil 102, is circulated around the evaporator coil 102 by an exterior fan 130. In a typical embodiment, the refrigerant begins to boil after absorbing heat from the ambient air and changes state to a low-pressure, low-temperature, super-heated vapor refrigerant. Saturated vapor, saturated liquid, and saturated fluid refer to a thermodynamic state where a liquid and its vapor exist in approximate equilibrium with each other. Super-heated fluid and super-heated vapor refer to a thermodynamic state where a vapor is heated above a saturation temperature of the vapor. Sub-cooled fluid and sub-cooled liquid refers to a thermodynamic state where a liquid is cooled below the saturation temperature of the liquid.
The low-pressure, low-temperature, super-heated vapor refrigerant leaving the evaporator coil 102 is fed into the reversing valve 104 that, in the heat pump mode, directs the refrigerant into the compressor 108 via the suction line 106. The compressor 108 increases the pressure of the low-pressure, low-temperature, super-heated vapor refrigerant and, by operation of the ideal gas law, also increases the temperature of the low-pressure, low-temperature, super-heated vapor refrigerant to form a high-pressure, high-temperature, superheated vapor refrigerant. The high-pressure, high-temperature, superheated vapor refrigerant leaves the compressor 108 via the discharge line 110 and enters the reversing valve 104 that, in the heat pump mode, directs the refrigerant to the condenser coil 112.
Air from the enclosed space 101 is circulated around the condenser coil 112 by an interior fan 132. The air from enclosed space 101 is typically cooler than the high-pressure, high-temperature, superheated vapor refrigerant present in condenser coil 112. Thus, heat is transferred from the high-pressure, high-temperature, superheated vapor refrigerant to the air from the enclosed space 101. Removal of heat from the high-pressure, high-temperature, superheated vapor refrigerant causes the high-pressure, high-temperature, superheated vapor refrigerant to condense and change from a vapor state to a high-pressure, high-temperature, sub-cooled liquid state. The high-pressure, high-temperature, sub-cooled liquid refrigerant leaves the condenser coil 112 and enters the evaporator coil 102. Just before the high-pressure, high-temperature, sub-cooled liquid refrigerant enters the evaporator coil 102, the high-pressure, high-temperature, sub-cooled liquid refrigerant passes through the first valve 120.
The first valve 120 abruptly reduces the pressure of the high-pressure, high-temperature, sub-cooled liquid refrigerant and regulates an amount of refrigerant that travels to the evaporator coil 102. Abrupt reduction of the pressure of the high-pressure, high-temperature, sub-cooled liquid refrigerant causes sudden, rapid, evaporation of a portion of the high-pressure, high-temperature, sub-cooled liquid refrigerant, commonly known as “flash evaporation.” The flash evaporation lowers the temperature of the resulting liquid/vapor refrigerant mixture to a temperature lower than a temperature of the ambient air. The liquid/vapor refrigerant mixture leaves the first valve 120 and returns to the evaporator coil 102, and the cycle begins again.
The controller 122 is configured to communicate with the components of the heat pump system 100 to monitor and control the components of the heat pump system 100. Communication between the controller 122 and the components of the heat pump system 100 may be via a wired or a wireless connection. In a typical embodiment, the controller 122 is configured to control operation of one or more of the reversing valve 104, the compressor 108, the valve 120, the exterior fan 130, the interior fan 132, and other components of the heat pump system 100. In some embodiments, the compressor 108 may be a variable or multispeed compressor. In such embodiments, the controller 122 controls the speed at which the compressor 108 operates. In some aspects, the controller 122 controls whether the first valve 120 is in the open or closed position. In some aspects, the first valve 120 may be controlled by changes in system pressures and/temperatures, independent of the controller 122. The controller 122 also controls whether the exterior fan 130 and the interior fan 132 are operating. In some embodiments, one or both of the exterior fan 130 and the interior fan 132 may be variable or multispeed fans. In such embodiments, the controller 122 controls the speed at which the exterior fan 130 and the interior fan 132 operate.
The controller 122 can communicate with an external data source 150 via an antenna 124. In some embodiments, the controller 122 may use the antenna 124 to communicate with a router 154. The router 154 may be, for example, an internet access point that is connected to the Internet. The external data source 150 provides data regarding local environmental conditions to controller 122 and may be, for example, an internet weather-data service. In a typical embodiment, the data from external data source 150 may include, for example, temperature, humidity, dew point temperature, forecast information, and the like. Forecast information can include predictions about future temperature, humidity, dew point temperature, and the like. In some embodiments, the controller 122 can monitor the ambient conditions (e.g., temperature and humidity) near the evaporator coil 102 via a sensor 160 positioned proximal to the evaporator coil 102.
As stated above, during operation of the heat pump system 200, low-pressure, low-temperature refrigerant at approximately −25° C. is circulated through the evaporator coil 102. Ambient air from the environment surrounding the evaporator coil 102, which is typically warmer than the refrigerant in the evaporator coil 102, is circulated around the evaporator coil 102 by the exterior fan 130. In a typical embodiment, the refrigerant begins to boil after absorbing heat from the ambient air and changes state to a low-pressure, low-temperature, super-heated vapor refrigerant. The low-pressure, low-temperature, super-heated vapor refrigerant leaving the evaporator coil 102 is fed into the reversing valve 104 that, in the heat pump mode, directs the refrigerant into the compressor 108 via the suction line 106. The compressor 108 increases the pressure of the low-pressure, low-temperature, super-heated vapor refrigerant and, by operation of the ideal gas law, also increases the temperature of the low-pressure, low-temperature, super-heated vapor refrigerant to approximately 123° C. to form a high-pressure, high-temperature, superheated vapor refrigerant. The high-pressure, high-temperature, superheated vapor refrigerant at approximately 123° C. leaves compressor 108 via the discharge line 110 and enters reversing the valve 104 that, in the heat pump mode, directs the refrigerant to the condenser coil 112.
Air from the enclosed space 101 is circulated around the condenser coil 112 by the interior fan 132. The air from the enclosed space 101 is typically cooler than the high-pressure, high-temperature, superheated vapor refrigerant (at approximately 123° C.) present in the condenser coil 112. Thus, heat is transferred from the high-pressure, high-temperature, superheated vapor refrigerant to the air from enclosed space 101. Removal of heat from the high-pressure, high-temperature, superheated vapor refrigerant causes the high-pressure, high-temperature, superheated vapor refrigerant to condense and change from a vapor state to a high-pressure, high-temperature, sub-cooled liquid state at approximately 40° C. The high-pressure, high-temperature, sub-cooled liquid refrigerant at approximately 40° C. leaves the condenser coil 112. Just before the high-pressure, high-temperature, sub-cooled liquid refrigerant enters the evaporator coil 102, at least a portion of the high-pressure, high-temperature, sub-cooled liquid refrigerant at approximately 40° C. is redirected, via the refrigerant redirection circuit 202, to the compressor 108 to absorb heat and lower the compressor discharge temperature. In a typical embodiment, a portion of the high-pressure, high-temperature, sub-cooled liquid refrigerant is redirected in the heat pump system 200.
In a typical embodiment, the second valve 204 may be, for example, a solenoid valve that is configured to regulate the high-pressure, high-temperature, sub-cooled liquid refrigerant at approximately 40° C. for redirection. The redirected portion of the refrigerant passes through the third valve 206. In a typical embodiment, the third valve 206 may be, for example, thermostatic expansion valve or a throttling valve. The third valve 206 abruptly reduces the pressure of the high-pressure, high-temperature, sub-cooled liquid refrigerant before the redirected refrigerant enters the coils 208 that wrap around the compressor 108. Abrupt reduction of the pressure of the high-pressure, high-temperature, sub-cooled liquid refrigerant causes sudden, rapid, evaporation of a portion of the high-pressure, high-temperature, sub-cooled liquid refrigerant, commonly known as “flash evaporation.” The flash evaporation lowers the temperature of the resulting liquid/vapor refrigerant mixture to approximately −25° C. which is lower than a temperature of the ambient air around the compressor 108. The liquid/vapor refrigerant mixture leaves the third valve 206 and travels to the coils 208 surrounding the compressor 108.
Ambient air from the environment surrounding the compressor 108, which is typically warmer (e.g., approximately 123° C.) than the refrigerant in the coils 208 (e.g., −25° C.) surrounding the compressor 108, is circulated around the coils 208. As a result, the refrigerant absorbs heat from the ambient air surrounding the compressor 108 as well as compressor heat resulting in a reduction in the compressor discharge temperature. The redirected refrigerant after passing through the coils 208 surrounding the compressor 108 is redirected to the compressor 108 via the suction line 106. As a result, the heat absorbed by the refrigerant is retained within the heat pump system 200.
The pressure enthalpy diagram 300 describes a relationship of pressure and enthalpy of the refrigerant within the heat pump system 200. On the pressure enthalpy diagram 300, pressure is indicated on the y-axis and enthalpy is indicated on the x-axis. Typically, enthalpy is in units of shown on the pressure enthalpy diagram 300 designates points at which the refrigerant changes phase. A left vertical curve indicates a saturated liquid curve and a right vertical curve indicates a saturated vapor curve. The region in between the two curves describe refrigerant states that contain a mixture of both liquid and vaper. Locations to the left of the saturated liquid curve indicate that the refrigerated is in liquid from and location to the right of the saturated vapor curve indicate that the refrigerant is in vapor from. In the pressure enthalpy diagram 300, points 1-4 illustrate a refrigerant cycle in a conventional heat pump system 100 of
Air from the enclosed space 101 is circulated around the condenser coil 112 by the interior fan 132. The air from the enclosed space 101 is typically cooler than the high-pressure, high-temperature, superheated vapor refrigerant (at approximately 123° C.) present in the condenser coil 112. Thus, heat is transferred from the high-pressure, high-temperature, superheated vapor refrigerant to the air from enclosed space 101 causing the high-pressure, high-temperature, superheated vapor refrigerant to condense and change from a vapor state to a high-pressure, high-temperature, sub-cooled liquid state at approximately 40° C. The high-pressure, high-temperature, sub-cooled liquid refrigerant at approximately 40° C. leaves the condenser coil 112.
From step 404, the process 400 proceeds to step 406. At step 406, just before the high-pressure, high-temperature, sub-cooled liquid refrigerant enters the evaporator coil 102, at least a portion of the high-pressure, high-temperature, sub-cooled liquid refrigerant at approximately 40° C. is redirected, via the refrigerant redirection circuit 202, to the compressor 108. In a typical embodiment, the refrigerant redirection circuit 202 includes the second valve 204, the third valve 206 and coils 208 that wrap around the compressor 108. In a typical embodiment, the refrigerant redirection circuit 202 is configured to redirect a portion of the refrigerant from the heat pump system 200 around the compressor 108 to absorb heat and lower the compressor discharge temperature. In a typical embodiment, the second valve 204 may be, for example, a solenoid valve that is configured to regulate the high-pressure, high-temperature, sub-cooled liquid refrigerant at approximately 40° C. for redirection. The redirected portion of the refrigerant passes through the third valve 206. In a typical embodiment, the third valve 206 may be, for example, thermostatic expansion valve or a throttling valve. The third valve 206 abruptly reduces the pressure of the high-pressure, high-temperature, sub-cooled liquid refrigerant before the redirected refrigerant enters the coils 208 that wrap around the compressor 108. Abrupt reduction of the pressure of the high-pressure, high-temperature, sub-cooled liquid refrigerant causes sudden, rapid, evaporation of a portion of the high-pressure, high-temperature, sub-cooled liquid refrigerant, commonly known as “flash evaporation.” The flash evaporation lowers the temperature of the resulting liquid/vapor refrigerant mixture to approximately −25° C. which is lower than a temperature of the ambient air around the compressor 108. The liquid/vapor refrigerant mixture leaves the third valve 206 and travels to the coils 208 surrounding the compressor 108. The refrigerant absorbs heat from the ambient air surrounding the compressor 108 as well as compressor heat resulting in a reduction in the compressor discharge temperature at step 408. At step 410, the redirected refrigerant after passing through the coils 208 surrounding the compressor 108 is redirected to the compressor 108 via the suction line 106 resulting in the heat absorbed by the refrigerant to be retained within the heat pump system 200. At step 412, the process 400 ends.
Various advantages of the exemplary embodiments of the present invention include reducing the compressor shell temperature resulting in a reduction in the compressor discharge temperature. Heat absorbed by the refrigerant is retained within the heat pump system improving an isentropic efficiency of the compressor unlike conventional systems where the heat is lost to the ambient air. The exemplary heat pump system provides smoother operation while the compressor is equipped with acoustic jacket on high pressure ratios. Approximately 8% to 16% of evaporator load is shifted for compressor cooling resulting in less load in the evaporator. As such, the exemplary heat pump system operates with higher evaporating temperatures which improves overall system performance while reducing and slowing frost formation. The exemplary heat pump system minimizes the discharge temperature extending an operating envelope of the compressor. The exemplary heat pump system can be utilized with other methods such as, for example, vapor/liquid injection without any limitations.
The term “substantially” is defined as largely but not necessarily wholly what is specified (and includes what is specified; e.g., substantially 90 degrees includes 90 degrees and substantially parallel includes parallel), as understood by a person of ordinary skill in the art. In any disclosed embodiment, the terms “substantially,” “approximately,” “generally,” and “about” may be substituted with “within [a percentage] of” what is specified, where the percentage includes 0.1, 1, 5, and 10 percent.
While the above detailed description has shown, described, and pointed out novel features as applied to various embodiments, it will be understood that various omissions, substitutions, and changes in the form and details of the devices or algorithms illustrated can be made without departing from the spirit of the disclosure. As will be recognized, the processes described herein can be embodied within a form that does not provide all of the features and benefits set forth herein, as some features can be used or practiced separately from others. The scope of protection is defined by the appended claims rather than by the foregoing description. All changes which come within the meaning and range of equivalency of the claims are to be embraced within their scope.
For purposes of this patent application, the term computer-readable storage medium encompasses one or more tangible computer-readable storage media possessing structures. As an example and not by way of limitation, a computer-readable storage medium may include a semiconductor-based or other integrated circuit (IC) (such as, for example, a field-programmable gate array (FPGA) or an application-specific IC (ASIC)), a hard disk, an HDD, a hybrid hard drive (HHD), an optical disc, an optical disc drive (ODD), a magneto-optical disc, a magneto-optical drive, a floppy disk, a floppy disk drive (FDD), magnetic tape, a holographic storage medium, a solid-state drive (SSD), a RAM-drive, a SECURE DIGITAL card, a SECURE DIGITAL drive, a flash memory card, a flash memory drive, or any other suitable tangible computer-readable storage medium or a combination of two or more of these, where appropriate.
Particular embodiments may include one or more computer-readable storage media implementing any suitable storage. In particular embodiments, a computer-readable storage medium implements one or more portions of the processor, one or more portions of the system memory, or a combination of these, where appropriate. In particular embodiments, a computer-readable storage medium implements RAM or ROM. In particular embodiments, a computer-readable storage medium implements volatile or persistent memory. In particular embodiments, one or more computer-readable storage media embody encoded software.
In this patent application, reference to encoded software may encompass one or more applications, bytecode, one or more computer programs, one or more executables, one or more instructions, logic, machine code, one or more scripts, or source code, and vice versa, where appropriate, that have been stored or encoded in a computer-readable storage medium. In particular embodiments, encoded software includes one or more application programming interfaces (APIs) stored or encoded in a computer-readable storage medium. Particular embodiments may use any suitable encoded software written or otherwise expressed in any suitable programming language or combination of programming languages stored or encoded in any suitable type or number of computer-readable storage media. In particular embodiments, encoded software may be expressed as source code or object code. In particular embodiments, encoded software is expressed in a higher-level programming language, such as, for example, C, Python, Java, or a suitable extension thereof. In particular embodiments, encoded software is expressed in a lower-level programming language, such as assembly language (or machine code). In particular embodiments, encoded software is expressed in JAVA. In particular embodiments, encoded software is expressed in Hyper Text Markup Language (HTML), Extensible Markup Language (XML), or other suitable markup language.
Depending on the embodiment, certain acts, events, or functions of any of the algorithms described herein can be performed in a different sequence, can be added, merged, or left out altogether (e.g., not all described acts or events are necessary for the practice of the algorithms). Moreover, in certain embodiments, acts or events can be performed concurrently, e.g., through multi-threaded processing, interrupt processing, or multiple processors or processor cores or on other parallel architectures, rather than sequentially. Although certain computer-implemented tasks are described as being performed by a particular entity, other embodiments are possible in which these tasks are performed by a different entity.
