Patent Application
20170191718
This application relates generally to vapor compression systems incorporated in air conditioning and refrigeration applications.
Vapor compression systems utilize a working fluid, typically referred to as a refrigerant that changes phases between vapor, liquid, and combinations thereof in response to being subjected to different temperatures and pressures associated with operation of the vapor compression system. Refrigerants are desired that are friendly to the environment, yet have a coefficient of performance (COP) that is comparable to traditional refrigerants. COP is a ratio of heating or cooling provided to electrical energy consumed, and higher COPs equate to lower operating costs. Unfortunately, there are challenges associated with designing vapor compression system components compatible with environmentally-friendly refrigerants, and more specifically, vapor compression system components that operate to maximize efficiency using such refrigerants.
In an embodiment of the present disclosure, a heating, ventilation, air conditioning, and refrigeration (HVAC&R) system includes a refrigerant loop, a compressor disposed along the refrigerant loop and configured to circulate refrigerant through the refrigerant loop, an evaporator disposed along the refrigerant loop and configured to evaporate the refrigerant into refrigerant vapor, a condenser disposed along the refrigerant loop and configured to condense the refrigerant vapor into liquid refrigerant, a first conduit fluidly coupling the evaporator and the condenser to one another, a first expansion valve disposed along the first conduit between the evaporator and the condenser, a second conduit fluidly coupling the evaporator and the condenser to one another, where the first conduit and the second conduit are separate from one another, and a second expansion valve disposed along the second conduit between the evaporator and the condenser.
In another embodiment of the present disclosure, a heating, ventilation, air conditioning, and refrigeration (HVAC&R) system includes a refrigerant loop, a compressor disposed along the refrigerant loop and configured to circulate refrigerant through the refrigerant loop, an evaporator disposed along the refrigerant loop and configured to evaporate the refrigerant into refrigerant vapor, a condenser disposed along the refrigerant loop configured to condense the refrigerant vapor into liquid refrigerant, a plurality of expansion valves disposed between the evaporator and the condenser, where each expansion valve of the plurality of expansion valves is in separate fluid communication with the evaporator and the condenser, and one or more tangible, non-transitory machine-readable media comprising processor-executable instructions to receive feedback from a sensor indicative of a target heating or cooling capacity of the HVAC&R system and adjust at least one of the expansion valves of the plurality of expansion valves based at least on the feedback to control a flow of the refrigerant between the evaporator and the condenser.
In still another embodiment of the present disclosure, a method includes receiving feedback from a sensor of a heating, ventilation, air conditioning, and refrigeration (HVAC&R) system, where the feedback is indicative of a target heating or cooling capacity of the HVAC&R system and selectively adjusting a plurality of expansion valves based at least on the feedback to control a flow of refrigerant between an evaporator and a condenser of the HVAC&R system, wherein the plurality of expansion valves is disposed between the evaporator and the condenser of the HVAC&R system, and wherein each expansion valve of the plurality of expansion valves is in separate fluid communication with the evaporator and the condenser.
Embodiments of the present disclosure are directed to an HVAC&R system that includes multiple (e.g., more than one) expansion devices between a condenser and an evaporator. The expansion devices may include a plurality of expansion valves, which may be different sizes. Including expansion valves that are different sizes may enhance control of a flow of the refrigerant between the condenser and the evaporator, which may lead to enhanced efficiency of the HVAC&R system. For example, a controller may be configured to adjust one or more of the plurality of expansion valves (e.g., selectively control) based on a target heating or cooling capacity of the HVAC&R system. Moreover, multiple relatively small expansion valves may be less expensive than a single expansion valve sized to accommodate a maximum heating or cooling capacity of the HVAC&R system. Accordingly, including multiple expansion devices between the condenser and the evaporator of the HVAC&R system may reduce costs and enhance efficiency of the HVAC&R system.
Turning now to the drawings,
Some examples of fluids that may be used as refrigerants in the vapor compression system 14 are hydrofluorocarbon (HFC) based refrigerants, for example, R-410A, R-407, R-134a, hydrofluoro olefin (HFO), “natural” refrigerants like ammonia (NH3), R-717, carbon dioxide (CO2), R-744, or hydrocarbon based refrigerants, water vapor, or any other suitable refrigerant. In some embodiments, the vapor compression system 14 may be configured to efficiently utilize refrigerants having a normal boiling point of about 19 degrees Celsius (66 degrees Fahrenheit) at one atmosphere of pressure, also referred to as low pressure refrigerants, versus a medium pressure refrigerant, such as R-134a. As used herein, “normal boiling point” may refer to a boiling point temperature measured at one atmosphere of pressure.
In some embodiments, the vapor compression system 14 may use one or more of a variable speed drive (VSDs) 52, a motor 50, the compressor 32, the condenser 34, the expansion valve or device 36, and/or the evaporator 38. The motor 50 may drive the compressor 32 and may be powered by a variable speed drive (VSD) 52. The VSD 52 receives alternating current (AC) power having a particular fixed line voltage and fixed line frequency from an AC power source, and provides power having a variable voltage and frequency to the motor 50. In other embodiments, the motor 50 may be powered directly from an AC or direct current (DC) power source. The motor 50 may include any type of electric motor that can be powered by a VSD or directly from an AC or DC power source, such as a switched reluctance motor, an induction motor, an electronically commutated permanent magnet motor, or another suitable motor.
The compressor 32 compresses a refrigerant vapor and delivers the vapor to the condenser 34 through a discharge passage. In some embodiments, the compressor 32 may be a centrifugal compressor. The refrigerant vapor delivered by the compressor 32 to the condenser 34 may transfer heat to a cooling fluid (e.g., water or air) in the condenser 34. The refrigerant vapor may condense to a refrigerant liquid in the condenser 34 as a result of thermal heat transfer with the cooling fluid. The liquid refrigerant from the condenser 34 may flow through the expansion device 36 to the evaporator 38. In the illustrated embodiment of
The liquid refrigerant delivered to the evaporator 38 may absorb heat from another cooling fluid, which may or may not be the same cooling fluid used in the condenser 34. The liquid refrigerant in the evaporator 38 may undergo a phase change from the liquid refrigerant to a refrigerant vapor. As shown in the illustrated embodiment of
In some embodiments, the expansion device 36 and/or 66 may include two or more expansion valves that may be in separate fluid communication between the condenser 34 and the evaporator 38 (e.g., fluid flowing through a first expansion valve does not flow through a second expansion valve). Typically, a single expansion valve may be used between the condenser 34 and evaporator 38. The single expansion valve may be sized to accommodate a target heating or cooling capacity of the HVAC&R system 10. Unfortunately, such a single expansion valve may be relatively large and expensive. Additionally, control of the single expansion valve may be difficult or limited, especially when the single expansion valve cannot be tuned (e.g., adjusted to intermediate positions between on and off). Therefore, the single expansion valve may lead to reduced efficiency of the HVAC&R system 10 (e.g., the single expansion valve may not provide fine-tuned control of a flow of the refrigerant between the condenser 34 and the evaporator 38). Accordingly, embodiments of the present disclosure are related to the HVAC&R system 10 that includes multiple expansion devices (e.g., expansion valves) between the condenser 34 and the evaporator 38 that may be selectively controlled to reduce costs and improve control and/or efficiency of the HVAC&R system 10.
In some embodiments, the plurality of expansion valves 100 may be symmetrically positioned along the condenser 34 and/or evaporator 38 relative to a midpoint 101 (e.g., center) of a first length 102 of the condenser 34 and/or a midpoint 103 (e.g., center) of a second length 104 of the evaporator 38. However, in other embodiments, the plurality of expansion valves 100 may be non-symmetrically positioned relative to the midpoints 101 and/or 103 of the first length 102 and/or the second length 104. In still further embodiments, the plurality of expansion valves 100 may be uniformly spaced relative to one another along the first length 102 of the condenser 34 and/or the second length 104 of the evaporator 38. In other embodiments, at least two of the plurality of expansion valves 100 may be non-uniformly spaced relative to one another along the first length 102 of the condenser 34 and/or the second length 104 of the evaporator 38.
Additionally, the first expansion valve 90, the second expansion valve 94 and the third expansion valve 98 may be positioned in the same or different positions between the condenser 34 and the evaporator 38. In other words, the first expansion valve 90, the second expansion valve 94, and the third expansion valve 98 may be positioned at the same or different distances from the condenser 34 and/or the evaporator 38. In any case, the plurality of expansion valves 100 may be disposed at any suitable position along a length 105 of the conduits 92, 96, and/or 99.
Each of the plurality of expansion valves 100 may be sized the same or differently than at least one expansion valve of the plurality of expansion valves 100. The sizing of each of the plurality of expansion valves 100 may be based at least partially on a heating or cooling capacity of the HVAC&R system 10. Additionally, some expansion valves of the plurality of expansion valves 100 may be tuned (e.g., a position of such expansion valves may be adjusted to enable a partial flow of the refrigerant through the expansion valve) whereas others may be on/off expansion valves (e.g., the position of the expansion valve may either be open or closed, but not in a position in between). As discussed above, utilizing multiple smaller expansion valves 100 may be less expensive than utilizing a single expansion valve that may be configured to meet the entire heating or cooling capacity of the HVAC&R system 10.
Further, a position of one or more of the plurality of expansion valves 100 may be selectively adjusted by a controller 106 (e.g., based on a target heating or cooling capacity of the HVAC&R system 10). The controller 106 may include memory circuitry 108 (e.g., memory) and a processor 110. For example, the controller 106 may include non-transitory code or instructions stored in a machine-readable medium (e.g., the memory 108) that is used by a processor (e.g., the processor 110) to implement the techniques disclosed herein. The memory 108 may store computer instructions that may be executed by the processor 110. Additionally, the memory 108 may store experimental data and/or other values (e.g., threshold values) relating to operating conditions of the HVAC&R system 10.
In some embodiments, a cooling or heating capacity of the HVAC&R system 10 may vary, such that a flow of the refrigerant from the condenser 34 to the evaporator 38 (or vice versa) may be adjusted to achieve a target heating or cooling capacity of the HVAC&R system 10 (e.g., predetermined capacity). Therefore, the controller 106 may be coupled to the plurality of expansion valves 100 (e.g., actuators configured to adjust a position of one or more of the plurality of expansion valves 100) to control a flow of the refrigerant between the condenser 34 and the evaporator 38 based at least on feedback related to an actual cooling or heating capacity of the HVAC&R system 10. In some embodiments, the controller 106 may selectively control at least one of the plurality of expansion valves 100 based on the target heating or cooling capacity of the HVAC&R system 10. Accordingly, the controller 106 may be coupled to one or more sensors 112 (e.g., temperature sensors, pressure sensors, composition sensors, flow meters, or another suitable sensor) that may be configured to provide feedback to the controller 106 related to the actual heating or cooling capacity of the HVAC&R system 10.
As a non-limiting example, the controller 106 may be coupled to one of the sensors 112 configured to monitor a temperature of the refrigerant in the condenser 34. The temperature of the refrigerant in the condenser 34 may be indicative of the actual heating or cooling capacity of the HVAC&R system 10. The controller 106 may adjust one or more of the plurality of expansion valves 100 based on the feedback received from the one or more sensors 112. Further, the controller 106 may be configured to monitor one or more operating parameters of the HVAC&R system 10 to determine whether the adjustment to the at least one expansion valve 100 of the plurality of expansion valves 100 achieves the target heating or cooling capacity of the HVAC&R system 10. For example, the controller 106 may compare the actual heating or cooling capacity of the HVAC&R system 10 to the target heating or cooling capacity of the HVAC&R system 10 to determine a differential between the target heating or cooling capacity of the HVAC&R system 10 and the actual heating or cooling capacity of the HVAC&R system 10. In response, the controller 106 may re-adjust one or more of the plurality of expansion valves 100 based on such differential.
In some embodiments, the controller 106 may selectively adjust a first expansion valve of the plurality of expansion valves 100 based on a size of the first expansion valve and/or the differential between the target heating or cooling capacity of the HVAC&R system 10 and the actual heating or cooling capacity of the HVAC&R system 10. Therefore, control of the plurality of expansion valves 100 may provide enhanced control when compared to a single expansion valve. Because the plurality of expansion valves 100 may include expansion valves having different sizes, smaller expansion valves in combination with larger expansion valves may enable more precise control over the flow of refrigerant between the condenser 34 and the evaporator 38.
Additionally, by using multiple expansion valves 100 each in separate fluid communication between the condenser 34 and the evaporator 38, at least one of the plurality of expansion valves 100 may be reduced in size. Reducing a size of one or more of the plurality of expansion valves 100 may result in lower pressure losses, improved (e.g., more uniform) distribution of refrigerant, and enhanced capacity control overall. In some embodiments, the plurality of expansion valves 100 may serve as a storage control (e.g., expansion valves may be configured to be closed to store refrigerant in the condenser 34). It should be noted that the evaporator 38 may include either a flooded arrangement or a falling film arrangement.
Furthermore, in some embodiments, the condenser 34 may include a subcooler 130. For example, the subcooler 130 may further cool the refrigerant after the refrigerant exits the condenser 34, which may ultimately enhance an efficiency of the HVAC&R system 10. As shown in the illustrated embodiment, the subcooler 130 may be integral to the condenser 34 (e.g., disposed within a common housing of the condenser 34). However, in other embodiments, the subcooler 130 may be positioned external to the condenser 34. In any case, the refrigerant flowing from the subcooler 130 may be directed into one or more of the plurality of expansion valves 100 before the refrigerant is directed to the evaporator 38.
While only certain features and embodiments have been illustrated and described, many modifications and changes may occur to those skilled in the art (e.g., variations in sizes, dimensions, structures, shapes and proportions of the various elements, values of parameters (e.g., temperatures, pressures, etc.), mounting arrangements, use of materials, colors, orientations, etc.) without materially departing from the novel teachings and advantages of the subject matter recited in the claims. The order or sequence of any process or method steps may be varied or re-sequenced according to alternative embodiments. It is, therefore, to be understood that the appended claims are intended to cover all such modifications and changes as fall within the true spirit of the invention. Furthermore, in an effort to provide a concise description of the exemplary embodiments, all features of an actual implementation may not have been described (i.e., those unrelated to the presently contemplated best mode of carrying out the invention, or those unrelated to enabling the claimed invention). It should be appreciated that in the development of any such actual implementation, as in any engineering or design project, numerous implementation specific decisions may be made. 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, without undue experimentation.
This application claims priority from and the benefit of U.S. Provisional Application Ser. No. 62/275,522, filed Jan. 6, 2016, entitled “VAPOR COMPRESSION SYSTEM,” the disclosure of which is hereby incorporated by reference in its entirety for all purposes.
| Number | Date | Country | |
|---|---|---|---|
| 62275522 | Jan 2016 | US |
