Refrigerant circuit suction heat control

Abstract

A method intended to control overheating in a refrigerant circuit containing a working fluid. The method includes directing a suction flow of working fluid from the evaporator through the suction heat exchanger and directing working fluid compressed by the compressor to the suction heat exchanger. The method further includes controlling a flow of compressed working fluid through the suction heat exchanger. The controlling includes modulating the working fluid control valve based on a determined target saturation temperature of the compressed working fluid. The refrigerant circuit includes a main flow path, a bypass flow path, a working fluid control valve, and a controller for the refrigerant circuit. The controller is configured to determine a target saturation temperature of working fluid flowing through the suction heat exchanger in the bypass flow path, and modulate the working fluid control valve based on the target saturation temperature.

Description

Technical Field

[0001] The present disclosure relates to a heating, ventilation, air conditioning, and refrigeration ("HVACR") system. More specifically, embodiments herein relate to controlling a refrigerant circuit of an HVACR system. Background Art

[0002] Heating, ventilation, air conditioning and refrigeration (HVACR) systems are typically used to heat, cool and / or ventilate an enclosed space (e.g., the interior of a commercial or residential building, the interior of a refrigerated transport unit, etc.). An HVACR system may include a refrigerant circuit for providing cooled or heated air to the area. A heat transfer circuit cools or heats the air directly or indirectly using a working fluid. Typically, the heat transfer circuit includes a compressor for compressing the working fluid. In some configurations, the working fluid may be heated before entering the compressor. Summary of the invention

[0003] In one embodiment, a method for controlling superheat in a refrigerant circuit includes a compressor, a condenser, an expansion device, an evaporator, and a suction heat exchanger. A working fluid is contained in the refrigerant circuit. The method includes directing a suction flow of the working fluid from the evaporator through the suction heat exchanger to the compressor, and directing a first portion of the working fluid compressed by the compressor from the compressor to the suction heat exchanger. The method also includes controlling the flow of the first portion of the working fluid entering the suction heat exchanger with a thermal fluid control valve. Controlling the flow of the first portion of the working fluid includes detecting a characteristic of the working fluid, determining a target saturation temperature of the first portion of the working fluid based on a predetermined suction superheat set point and the detected characteristic of the working fluid, and modulating the thermal fluid control valve based on the determined target saturation temperature.

[0004] In one embodiment, detecting the property of the working fluid includes detecting a saturation temperature of a first portion of the working fluid. Modulation of the working fluid control valve is based on a difference between the determined target saturation temperature and the detected saturation temperature of the first portion of the working fluid.

[0005] In one embodiment, detecting the characteristics of the working fluid includes: detecting the inlet temperature, outlet temperature and pressure of the working fluid in the suction flow flowing through the suction heat exchanger, and detecting the inlet temperature, outlet temperature and pressure of a first portion of the working fluid flowing through the suction heat exchanger.

[0006] In one embodiment, determining the target saturation temperature comprises determining a target log mean temperature difference for the suction heat exchanger based on the suction superheat set point and one or more detected characteristics of the working fluid. The target saturation temperature is determined based on the suction superheat set point, the target log mean temperature difference, and the saturation temperature of the working fluid in the suction flow.

[0007] In one embodiment, detecting the characteristic of the working fluid includes detecting one or more of the Prandtl number, the specific heat, the dynamic viscosity and the saturation temperature of the working fluid in the suction flow based on the detected characteristic of the working fluid. The target logarithmic mean temperature difference is determined based on one or more of the detected Prandtl number, the detected specific heat and the detected dynamic viscosity.

[0008] In one embodiment, the target superheat temperature is determined based on the suction superheat set point and one or more most severe characteristics of the suction heat exchanger.

[0009] In one embodiment, the one or more maximum severity characteristics of the suction heat exchanger correspond to when the compressor is operated at a predetermined maximum mass flow rate and at a predetermined minimum compression setting at the predetermined maximum mass flow rate.

[0010] In one embodiment, modulation of the working fluid control valve adjusts the working fluid control valve between different open positions.

[0011] In one embodiment, the suction flow of the working fluid flows through a first side of the suction heat exchanger, and the first portion of the working fluid flows through a second side of the suction heat exchanger. The first portion of the working fluid exchanges heat with the working fluid in the suction flow flowing through the suction heat exchanger but does not physically mix.

[0012] In one embodiment, the method also includes directing a second portion of the working fluid compressed by the compressor from the compressor through the condenser and the expansion device to the evaporator; and rejoining the first portion of the working fluid with the second portion of the working fluid downstream of the expansion device and upstream of the evaporator after passing the first portion of the working fluid through the suction heat exchanger.

[0013] In one embodiment, the method further comprises directing the first portion of the working fluid through a flow resistor after passing through the suction heat exchanger before the first portion of the working fluid rejoins the second portion of the working fluid.

[0014] In one embodiment, the method further includes cooling a second portion of the working fluid with a first process fluid using the condenser, expanding the second portion of the working fluid cooled in the condenser using the expansion device, and heating the second portion of the working fluid expanded by the expansion device with a second process fluid using the evaporator.

[0015] In one embodiment, a refrigerant circuit of a heating, ventilation, air conditioning and refrigeration (HVACR) system includes a compressor, a condenser, an expansion device, an evaporator and a suction heat exchanger connected in fluid connection; the refrigerant circuit includes a main flow path, a bypass flow path, a thermal fluid control valve, one or more sensors, and a controller for the refrigerant circuit. The main flow path extends from the compressor through the condenser, the expansion device, the evaporator and the suction heat exchanger and returns to the compressor. The bypass flow path extends through the suction heat exchanger. The bypass flow path extends from the main flow path downstream of the compressor and upstream of the condenser in the main flow path and extends to the main flow path downstream of the expansion device and upstream of the suction heat exchanger. The thermal fluid control valve controls the flow of the working fluid through the bypass flow path. The controller is configured to detect a characteristic of the working fluid using the one or more sensors, and determine a target saturation temperature of the working fluid in the bypass flow path flowing through the suction heat exchanger based on a suction superheat set point and the detected characteristic of the working fluid. The controller is also configured to modulate the thermal fluid control valve based on the determined target saturation temperature.

[0016] In one embodiment, the controller is configured to modulate the working fluid control valve based on a difference between a detected saturation temperature of the working fluid in the bypass flow path and the determined target saturation temperature.

[0017] In one embodiment, the controller is configured to detect a characteristic of the working fluid, including: the controller is configured to detect the pressure of the working fluid in the bypass flow path using a pressure sensor among the one or more sensors. The controller is also configured to determine the detected saturation temperature based on the pressure of the working fluid in the bypass flow path detected by the pressure sensor.

[0018] In one embodiment, the controller is configured to detect one or more of the Prandtl number, specific heat capacity, and dynamic viscosity of the working fluid flowing through the suction heat exchanger in the main flow path to detect the characteristic of the working fluid. The controller is also configured to determine a target logarithmic mean temperature difference of the suction heat exchanger based on the predetermined suction superheat set point and one or more of the Prandtl number, specific heat capacity, and dynamic viscosity of the working fluid in the suction flow. The target saturation temperature is determined based on the predetermined suction superheat set point, the target logarithmic mean temperature difference, and the saturation temperature.

[0019] In one embodiment, the target superheat temperature is determined based on the predetermined suction superheat set point and one or more most severe characteristics of the suction heat exchanger.

[0020] In one embodiment, the suction heat exchanger includes a first side and a second side, the main flow path extends through the first side of the suction heat exchanger, and the bypass flow path extends through the second side of the suction heat exchanger.

[0021] In one embodiment, a flow resistor is provided in the bypass flow path downstream of the suction heat exchanger. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 is a schematic diagram of an embodiment of a refrigerant circuit for a heating, ventilation, air conditioning, and refrigeration system.

[0023] Figure 2 is a flow chart of an embodiment of a method of controlling superheat in a refrigerant circuit.

[0024] Like reference numerals represent like features. DETAILED DESCRIPTION

[0025] Heating, ventilation, air conditioning, and refrigeration systems ("HVACR") are typically configured to heat and / or cool an enclosed space (e.g., the interior of a commercial or residential building, the interior of a refrigerated transport unit, etc.). The HVACR system includes a heat transfer loop for heating or cooling a process fluid (e.g., air, water, and / or glycol, etc.). A working fluid flows through the heat transfer loop and is used to heat or cool the process fluid. In one embodiment, the working fluid includes one or more refrigerants. The working fluid can heat and / or cool the process fluid directly or indirectly. For example, indirect heating and / or cooling can include the working fluid heating and / or cooling an intermediate fluid (e.g., air, water, and / or glycol, etc.), and then the heated / cooled intermediate fluid heats and / or cools the process fluid.

[0026] Figure 11 is a schematic diagram of an embodiment of a heat transfer loop 2 in an HVACR system 1. The heat transfer loop 2 includes a compressor 10, a condenser 30, an expansion device 40, an evaporator 50, and a suction heat exchanger 60. Optionally, the heat transfer loop 2 may also include Figure 1 Lubricant separator 20 is shown. In an embodiment, heat transfer circuit 2 may be modified to include additional components such as, for example, an economizer heat exchanger, one or more flow control devices, a receiving tank, a dryer, and the like.

[0027] The components of the heat transfer loop 2 are fluidly connected. The heat transfer loop 2 can be configured as a cooling system that can operate in a cooling mode (e.g., a fluid cooler of an HVACR system, an air conditioning system, etc.), or the heat transfer loop 2 can be configured to operate as a heat pump system that can operate in a cooling mode or a heating mode.

[0028] The working fluid flows through the heat transfer circuit 2. The flow path 5 of the working fluid through the heat transfer circuit 2 extends from the compressor 10 through (optionally) the lubricant separator 20, the condenser 30, the expansion device 40, the evaporator 50, the suction heat exchanger 60, and returns to the compressor 10. The working fluid includes one or more refrigerants with a lower environmental impact and may include one or more additional components as described above. The flow path 5 may also be referred to as the main flow path of the heat transfer circuit 2. Figure 1 As shown, the refrigerant circuit 2 further includes a bypass flow path 7 extending from the main flow path 5 and returning to the main flow path 5. The bypass flow path 7 will be described in more detail below.

[0029] A working fluid in a low-pressure gaseous state is sucked into the suction port 12 of the compressor 10. When the working fluid flows from the suction port 12 of the compressor 10 to the discharge port 14, the working fluid is compressed. In one embodiment, the compressor 10 may be a screw compressor, a scroll compressor, a centrifugal compressor, etc. The compression of the working fluid in the compressor 10 also increases the temperature of the working fluid. Therefore, the compressed working fluid discharged from the discharge port 14 of the compressor has a higher temperature (e.g., than the temperature at the suction port 12).

[0030] The compressor 10 may utilize a lubricant to lubricate its moving parts (e.g., rotors, bearings, etc.). The lubricant is mixed with the working fluid flowing through the compressor 10 such that the compressed working fluid discharged from the compressor 10 contains the lubricant. In one embodiment, the high pressure and high temperature working fluid flows to a lubricant separator 20 (if present). The lubricant separator 20 separates the lubricant from the refrigerant. For example, the lubricant separator 20 separates the liquid lubricant from the working fluid (e.g., separates the liquid lubricant from the gaseous component / refrigerant of the working fluid). The liquid lubricant may also contain dissolved refrigerant, and / or the gaseous refrigerant may contain some lubricant. The separated liquid lubricant then flows from the lubricant separator 20 back to the compressor 10 (e.g., Figure 1 The working fluid with higher pressure and temperature (e.g., including gaseous refrigerant) flows from the lubricant separator 20 to the condenser 30. Figure 1 In the embodiment, the lubricant separator 20 is separate from the compressor 10. In one embodiment, the lubricant separator 20 may be an internal lubricant separator incorporated into the compressor 10 (eg, incorporated into the same housing as the compressor 10).

[0031] In another embodiment, the lubricant may not be separated from the working fluid (i.e., lubricant separator 20 is not included) and remain mixed with the working fluid within the refrigerant circuit 2. In such an embodiment, the higher pressure and temperature working fluid may flow from the discharge port 14 of the compressor 10 to the condenser 30 without passing through the lubricant separator.

[0032] A first portion of the compressed working fluid discharged from the compressor 10 (i.e., a first portion of the higher temperature and higher pressure working fluid discharged from the compressor and / or after flowing through the optional lubricant separator 20 (if present)) flows into the bypass flow path 7. In the bypass flow path 7, the first portion of the compressed working fluid flows into and flows through the suction heat exchanger 60 within the bypass flow path 7 (e.g., flows through the second side 64 of the suction heat exchanger). A second portion of the compressed working fluid discharged from the compressor 10 flows to and flows through the condenser 30. The second portion of the working fluid remains in the main flow path 5. The flow of the working fluid through the suction heat exchanger 60 is described in more detail below.

[0033] The condenser 30 allows the working fluid and the first process fluid PF to 1 The heat exchanger is in heat transfer relationship without physical mixing within the condenser 30. When the working fluid and the first process fluid PF 1 When flowing through the condenser 30, the working fluid is mixed with the first process fluid PF 1 Cooling. Process fluid PF 1 The first process fluid PF is heated by the working fluid and leaves the condenser 30 at a higher temperature.1 It can be air, water and / or ethylene glycol, etc., suitable for absorbing and transferring heat from the working fluid and the heat transfer loop 2. For example, the first process fluid PF 1 It may be ambient air circulated from the outside atmosphere, water to be heated to hot water, or a fluid for transferring heat from the heat transfer loop 2. The working fluid becomes liquid or mostly liquid when cooled in the condenser 30.

[0034] The liquid / gas working fluid flows from the condenser 30 to the expansion device 40. The expansion device 40 allows the working fluid to expand. The expansion significantly reduces the temperature of the working fluid. In one embodiment, the expansion device 40 can be an expansion valve, an expansion plate, an expansion container, an orifice, etc., or other such expansion mechanisms. It should be understood that the expansion device 40 can be any type of expansion device used in the art to expand the working fluid so as to reduce the temperature of the working fluid. The expansion device 40 can also be referred to as an expander.

[0035] The lower temperature gaseous / liquid working fluid then flows from the expansion device 40 to and through the evaporator 50. The second process fluid PF 2 The evaporator 50 is a device that allows the working fluid and the second process fluid PF to flow separately from the working fluid. 2 The heat exchanger is in heat transfer relationship without physical mixing within the evaporator 50. When the working fluid and the second process fluid PF 2 When flowing through the evaporator 50, the working fluid is converted from the second process fluid PF 2 Absorbs heat and cools the second process fluid PF 2 In one embodiment, the working fluid exiting the evaporator 50 may be at or approximately at its saturation temperature.

[0036] In one embodiment, the second process fluid PF 2 The air is cooled by the HVACR system and conditioned by ventilation into the enclosure. In one embodiment, the second process fluid PF 2 The second process fluid PF may be an intermediate fluid (eg, water, a heat transfer fluid, a coolant, etc.), and the cooled second process fluid PF 2 It can then be used by the HVACR system to cool the air. The working fluid is in a gaseous or mostly gaseous state when it leaves the evaporator 50.

[0037] In some embodiments, lubricant entrained in the gaseous working fluid exiting the lubricant separator 20 is subsequently separated due to changes in temperature and / or pressure of the working fluid as it flows toward and / or through the evaporator 50. Such separated lubricant may flow to the evaporator 50 (e.g., accumulate within a particular region / volume of the evaporator 50). In one embodiment, an optional secondary lubricant flow path (not shown) may fluidly connect the evaporator 50 to the compressor 10, which is configured to allow liquid lubricant accumulated in the evaporator 50 to flow back to the compressor 10.

[0038] The bypass flow path 7 extends through the suction heat exchanger 60. The compressed working fluid in the bypass flow path 7 flows through the suction flow path and flows back to the main flow path 5. Figure 1 As shown, the bypass flow path 7 extends from the main flow path 5, passes through the suction heat exchanger 60, and then returns to the main flow path 5. The bypass flow path 7 extends from the downstream of the compressor 10 and the upstream of the condenser 30 of the main flow path 5. The bypass flow path 7 extends to the main flow path 5 downstream of the expander 40 and upstream of the suction heat exchanger 60.

[0039] The gaseous / mostly gaseous working fluid flows from the evaporator 50 to and through the suction heat exchanger 60. The suction heat exchanger 60 further heats the working fluid exhausted from the evaporator 50. The suction heat exchanger 60 heats the working fluid to increase the superheat of the working fluid and / or to more completely evaporate any remaining droplets in the suction stream. Superheat (superheat) is a measure of the change in temperature relative to the temperature at which the working fluid evaporates at a set pressure (e.g., T(P X ) 过热度 =T(P X )( 实际 -T(P X ) 饱和度 ). For example, increasing the superheat of the working fluid is to increase the temperature of the working fluid to a temperature above the saturation temperature at which the refrigerant(s) of the working fluid changes from a liquid state to a gaseous state. The heating of the working fluid within the suction heat exchanger 60 will be discussed in more detail below.

[0040] The expander 40 may be configured to operate based on the superheat of the suction working fluid. For example, the expander 40 may be configured to adjust the flow of the working fluid therethrough based on the superheat of the suction working fluid (eg, based on the evaporator outlet temperature T 5 To achieve the desired superheat, suction heat exchanger outlet temperature T 2In one embodiment, the expander 40 may be an electronic expansion valve operated / controlled by the controller 90 (e.g., controlled based on detections of the sensors 92A, 92B, and / or 94A). In one embodiment, the expander 40 may be configured to operate independently of the controller 90 (e.g., a mechanical expansion valve using a sensing bulb, an electronic expansion valve that operates directly based on signals from the sensors 92A, 92B, and / or 94A, or a separate one or more temperature and / or pressure sensors).

[0041] like Figure 1 As shown, the suction heat exchanger 60 includes a first side 62 and a second side 64. It should be understood that each "side" refers to a separate flow path through the suction heat exchanger 60, rather than a specific physical orientation. The fluids in the first side 62 and the second side 64 of the suction heat exchanger 60 exchange heat but do not physically mix.

[0042] The main flow path 5 extends through a first side 62 of the suction heat exchanger 60. The bypass flow path 7 extends through a second side 64 of the suction heat exchanger 60. The working fluid discharged from the evaporator 50 flows to the suction heat exchanger 60, passes through the first side 62, and flows from the suction heat exchanger 60 to the compressor 10. The compressed working fluid discharged from the compressor 10 (e.g., the second portion of the compressed working fluid) flows to the suction heat exchanger 60, passes through the second side 64, and enters the main flow path 5 from the suction heat exchanger 60. The working fluid flowing through the first side 62 of the suction heat exchanger 60 includes the second portion of the working fluid (after passing through the condenser 30, the expander 40, and the evaporator) and the first portion of the working fluid (after passing through the suction heat exchanger 60 and the optional evaporator 50).

[0043] In the main flow path 5, the first part of the working fluid and the second part of the working fluid are separated downstream of the compressor 10 and upstream of the condenser 30. In the main flow path 5, the first part of the working fluid and the second part of the working fluid are reunited downstream of the expander 40 and upstream of the suction heat exchanger 60. Figure 1 As shown, the first and second portions of the working fluid may be reunited in the main flow path 5 downstream of the expander 40 and upstream of the evaporator 50. In another embodiment, the first and second portions of the working fluid may be reunited in the main flow path 5 downstream of the evaporator 50 and upstream of the suction heat exchanger 60 (e.g., Figure 1 (indicated by the dashed arrow in the middle).

[0044] like Figure 1As shown, the bypass flow path 7 includes a first passage 72 (e.g., an inlet passage) and a second passage 74 (e.g., an outlet passage). The first passage 72 and the second passage 74 connect the suction heat exchanger 60 to the main flow path 5. For example, the bypass flow path 7 is formed by the first passage 72, the second side 64 of the suction heat exchanger 60, and the second passage 74.

[0045] The first passage 72 extends from the main flow path 5 to the suction heat exchanger 60. The first passage 72 is configured to guide / supply the first portion of the compressed working fluid to the second side 64 of the suction heat exchanger 60. For example, the first passage 72 extends to the second side 64 of the suction heat exchanger 60 and guides / supplies the first portion of the compressed working fluid to the second side 64 of the suction heat exchanger 60.

[0046] The second passage 74 extends from the suction heat exchanger 60 to the main flow path 5. The second passage 74 is configured to direct the second portion of the compressed working fluid from the suction heat exchanger 60 back to the main flow path 5 after passing through the suction heat exchanger 60. For example, the second passage 74 extends from the second side 64 of the suction heat exchanger 60 to the main flow path 5 and supplies the second portion of the working fluid (after passing through the suction heat exchanger 60) back to the main flow path 5. The second passage 74 can be connected to the main flow path 5 upstream of the suction heat exchanger 60 and downstream of the expander 40.

[0047] The relatively hotter and relatively higher pressure working fluid (e.g., the second portion of the compressed working fluid) flowing through the second side 64 of the suction heat exchanger 60 heats the relatively cooler and relatively lower pressure working fluid flowing through the first side 62 of the suction heat exchanger 60. The refrigerant circuit 2 includes a compression fluid control valve 80 that controls the mass flow of the relatively hotter compressed working fluid through the suction heat exchanger 60 (e.g., through the second side 64 of the suction heat exchanger 60). The compression working fluid control valve 80 may also be referred to as a thermal fluid control valve, a hot gas control valve, a working fluid control valve, a bypass control valve, a suction heat exchanger ("SHX") control valve, etc. For example, the thermal fluid control valve 80 controls the amount (e.g., percentage) of compressed working fluid discharged from the compressor 10 and redirects it to the suction heat exchanger 60 instead of the condenser 30. The thermal fluid control valve 80 is controlled / operated by a controller 90. In one embodiment, the expander 40 is configured to operate separately from the thermal fluid control valve 80. This can advantageously help ensure that the suction working fluid has at least some superheat. Control of the thermal fluid control valve 80 will be discussed in greater detail below.

[0048] like Figure 1As shown, the thermal fluid control valve 80 may be disposed in the bypass flow path 7 upstream of the suction heat exchanger 60 (e.g., the bypass flow path extends through the thermal fluid control valve 80). For example, the inlet / first passage 72 of the bypass flow path 7 includes the thermal fluid control valve 80. In one embodiment, the refrigerant circuit 2 may include an auxiliary hot gas valve 82 disposed in parallel with the thermal fluid control valve 80. When included, the auxiliary hot gas valve 82 may be included and used as a bypass valve for the thermal fluid control valve 80 (e.g., when a problem occurs with the thermal fluid control valve 80).

[0049] In one embodiment, the thermal fluid control valve 80 is an electric flow control valve that is adjustable to control the flow of the working fluid through the thermal fluid control valve (e.g., having an adjustable opening to change the amount of working fluid flowing through the valve). The "electric" flow control valve is driven by an electric motor to adjust the degree of opening of the valve (e.g., to change the amount of working fluid flowing through the expansion valve). The "position" of the thermal fluid control valve 80 refers to the degree to which the valve is open or closed. The positions of the thermal fluid control valve 80 include a first position (e.g., a 100% open position), a second position (e.g., a 100% closed position or a 0% open position), and a plurality of intermediate positions (i.e., stages) between the first position and the second position (e.g., 90% open, 80% open, 70% open, 60% open, etc.). The number of intermediate positions can be selected according to the required sensitivity of the valve. For example, based on its required flow control, the valve can have, but is not limited to, dozens of positions, hundreds of positions, thousands of positions, etc. In one embodiment, the thermal fluid control valve can have at least 10 positions. The control of the thermal fluid control valve 80 will be discussed in more detail below.

[0050] like Figure 1 As shown, the refrigerant circuit 2 may include a flow resistor 78. The flow resistor 78 is disposed downstream of the suction heat exchanger 60 in the bypass flow path 7. The compressed working fluid discharged from the suction heat exchanger 60 flows through the flow resistor 78 before flowing back to the main flow path 5. For example, the outlet / second passage 74 of the bypass flow path extends through the flow resistor 78 (e.g., the second passage 74 includes the flow resistor 78).

[0051] The flow resistor 78 is a restriction that provides resistance to the outflow of the compressed working fluid. In one embodiment, the flow resistor 78 is an orifice that restricts the flow of the compressed working fluid from the suction heat exchanger 60. For example, the flow resistor 78 has a relatively small area in the bypass flow path (e.g., a smaller cross-sectional area than other parts of the bypass flow path 7, a smaller cross-sectional area than the first passage 7, etc.).

[0052] The flow resistor 78 is configured to prevent the liquid working fluid from accumulating in the suction heat exchanger 60. Under some operating conditions, the compressed working fluid may be partially condensed in the suction heat exchanger 60. The flow resistor 78 has a certain size (e.g., cross-sectional area) configured so that any / all liquid condensed working fluid and at least some gaseous working fluid of the compressed working fluid are discharged from the suction heat exchanger 60. The size of the flow resistor 78 is configured so that at least some of the compressed working fluid in the gas phase is discharged and flows out of the suction heat exchanger 60 (e.g., flows through the second passage 74). For example, the size of the flow resistor 78 ensures that at least some of the compressed working fluid in the gas phase is discharged from the suction heat exchanger 60 when operating at the maximum severity. This operation of the flow resistor 78 is relative to the normal operation of the refrigerant circuit 5 (e.g., steady-state operation, not during the startup of the refrigerant circuit 2, not during the shutdown of the refrigeration circuit 2). In one embodiment, the flow resistor 78 is configured to have a fixed configuration (e.g., fixed size) during normal operation of the refrigerant circuit 5. The flow resistor 78 is configured to help maintain a desired flow through the suction heat exchanger 60. For example, the flow resistor 78 can help prevent the occurrence of an undesirable, relatively high flow through the suction heat exchanger 60 that may occur when the pressure downstream of the valve 40 is very low. Maximum severity operation will be discussed in detail below.

[0053] The refrigerant circuit 2 includes a controller 90 for controlling the operation of the refrigerant circuit 2 and its components. In one embodiment, the controller 90 may be a controller of the HVACR system 1. In one embodiment, the controller 90 may be a controller of the compressor 10. In one embodiment, the controller 90 includes a memory 91A and a processor 91B for storing information. The control scheme, operation, and information related to such control scheme and operation of the refrigerant circuit 2 and its components (e.g., the compressor 10, the expander 40, the thermal fluid control valve 80) as described herein may be stored on the memory 91A. For example, the following description of Figure 2 The operations described in method 1000 may be stored on controller 90 . Figure 1 The controller 90 described in the figure and below is described / shown as a single component. However, it should be understood that the "controller" shown in the figure and described herein may include multiple discrete or interconnected components, which in one embodiment include a memory 91A and a processor 91B.

[0054] The dashed lines provided in the figure represent the flow of fluid through the heat exchanger (e.g., condenser 30, evaporator 50, suction heat exchanger 60), and should be understood as not specifying the specific flow path of the fluid through the heat exchanger. The dotted lines provided in the figure are to illustrate the electronic communication between different features. For example, dotted lines are provided between the controller 90 and different components used, controlled, etc. by the controller 90. For example, the dotted lines extend from the controller 90 to the compressor 10 because the controller 90 can be configured to control the operation of the compressor 10 (e.g., the speed of the compressor when adjustable, the discharge pressure of the compressor 10 when adjustable, etc.).

[0055] For example, when the controller 90 receives temperature readings from the temperature sensors 92A, 92B, 92C, 92D of the working fluid in the refrigerant circuit 2, the dotted lines extend between the temperature sensors 92A, 92B, 92C, 92D and the controller 90. The temperature sensors 92A and 92B are disposed in the main flow path 5 and can be used to detect the inlet temperature T of the suction working fluid entering and leaving the suction heat exchanger 60, respectively. 1 and outlet temperature T 2 (For example, the inlet temperature T of the suction working fluid entering and exiting the suction heat exchanger 60 1 and outlet temperature T 2 , the inlet temperature T of the working fluid flowing into and out of the first side 62 of the suction heat exchanger 60 1 and outlet temperature T 2 ). The temperature sensor 93C and the temperature sensor 92D are disposed in the bypass flow path 7 and can be used to detect the inlet temperature T of the compressed working fluid entering and leaving the suction heat exchanger 60, respectively. 3 and outlet temperature T 4 (For example, the inlet temperature T of the compressed working fluid entering and exiting the suction heat exchanger 60 3 and outlet temperature T 4 , the inlet temperature T of the working fluid flowing into and out of the second side 64 of the suction heat exchanger 60 3 and outlet temperature T 4 ).

[0056] For example, when the controller 90 receives pressure readings from the pressure sensors 94A, 94B of the working fluid in the refrigerant circuit 2, the dashed line extends between the pressure sensors 94A, 94B and the controller 90. For example, the pressure sensor 94A is disposed in the main flow path 5 and can be used to detect the pressure P of the suction working fluid flowing through the suction heat exchanger 60 (e.g., the working fluid flowing through the first side 62 of the suction heat exchanger 60). 1For example, the pressure sensor 94B is disposed in the bypass flow path 7 and can be used to detect the pressure P of the compressed working fluid flowing through the suction heat exchanger 60 (eg, the working fluid flowing through the second side 64 of the suction heat exchanger 60). 2 .

[0057] For example, a mass flow sensor 96 is disposed in the bypass flow path to detect the mass flow rate of the compressed working fluid flowing through the suction heat exchanger 60 (eg, flowing into and through the bypass flow path). Mass flow sensor 96 may be a mass flow sensor configured to directly detect mass flow, or may be a volumetric flow sensor for indirectly detecting mass flow (eg, also using detection from pressure sensor 94B and / or temperature sensor 92C).

[0058] It should be understood that sensors 92A, 92B, 94C, 94D, 94A, 94B, 96 can be used to indirectly detect other properties of the working fluid. Such properties may include, but are not limited to, saturation temperature, viscosity, dynamic viscosity, specific heat capacity, Prandtl number, etc. of the working fluid flowing through the suction heat exchanger 60 (e.g., the suction working fluid flowing in the first side 62 of the suction heat exchanger, the compressed working fluid flowing in the second side 64 of the suction heat exchanger 60). Pressure sensor 94A can be used to indirectly detect the saturation temperature of the suction working fluid flowing through / in the suction heat exchanger (e.g., using a previously determined pressure-saturation temperature relationship of the working fluid, the saturation temperature is calculated based on the detected pressure). Pressure sensor 94B can be used to indirectly detect the saturation temperature of the compressed working fluid flowing through / in the suction heat exchanger 60.

[0059] Figure 2 is a flow chart of a method 1000 for controlling compressor suction superheat in a refrigerant circuit. For example, the method 1000 may be used to control Figure 1 The compressor suction superheat in the refrigerant circuit 2 is reduced. In one embodiment, the method 1000 can be implemented by a controller of the refrigerant circuit (e.g., the controller 90). For example, the operations for implementing the method 1000 and any related information used in implementing the method 1000 can be stored in the memory 91A of the controller 90.

[0060] The refrigerant circuit includes a working fluid. The refrigerant circuit includes a compressor (e.g., compressor 10), a condenser (e.g., condenser 30), an expander (e.g., expander 40), an evaporator (e.g., evaporator 50), a suction heat exchanger (e.g., suction heat exchanger 60), and a thermal fluid control valve (e.g., thermal fluid control valve 80). In one embodiment, method 1000 can be used for normal operation of the refrigerant circuit (e.g., not during shutdown and / or startup of the refrigerant circuit). Method 1000 starts at 1010.

[0061] At 1010, the working fluid discharged from the evaporator is directed through the suction heat exchanger to the compressor. The working fluid may also be referred to as the suction working fluid. For example, directing the suction working fluid through the suction heat exchanger at 1010 includes passing the working fluid through a first side (e.g., first side 62) of the suction heat exchanger. In one embodiment, in 1010, the working fluid is directed through a main flow path (e.g., main flow path 5) of the refrigerant circuit. Then, method 1000 proceeds from 1010 to 1020.

[0062] At 1020, a portion of the working fluid discharged from the compressor is directed through the suction heat exchanger. The working fluid can be referred to as compressed working fluid (e.g., working fluid compressed by and discharged from the compressor, a working fluid at a relatively high pressure within the refrigerant circuit 2). For example, directing the compressed working fluid through the suction heat exchanger at 1020 includes passing the compressed working fluid through a second side (e.g., second side 64) of the suction compression heat exchanger. The suction working fluid absorbs heat from the compressed working fluid as the compressed working fluid and the suction working fluid each flow through the suction heat exchanger, thereby further heating the suction working fluid.

[0063] In one embodiment, at 1020, the portion of the working fluid is directed from the main flow path through a bypass flow path (e.g., bypass flow path 7) and returned to the main flow path in the refrigerant circuit. Directing the compressed working fluid at 1020 may include passing the compressed working fluid through a suction heat exchanger and then through a flow restrictor (e.g., flow restrictor 78). For example, the compressed working fluid discharged from the suction heat exchanger passes through the flow restrictor (e.g., flows sequentially through the suction heat exchanger and then through the flow restrictor in the bypass flow path). After passing through the suction heat exchanger and the flow restrictor, the compressed working fluid flows from the flow restrictor back to the main flow path (e.g., flows from the bypass flow path into the main flow path 5).

[0064] The portion of the working fluid directed through the suction heat exchanger at 1020 can be a first portion of the working fluid discharged from a compressor (e.g., compressor 10). A second portion of the working fluid discharged from the compressor is directed through a condenser and an expander to an evaporator. The suction working fluid directed at 1010 includes a second portion of the working fluid after passing through the condenser, the expander, and the evaporator. For example, the first portion and the second portion of the working fluid can rejoin in the main flow path of the refrigerant circuit downstream of the expander and upstream of the compressor. Then, method 1000 proceeds from 1020 to 1030.

[0065] At 1030, a thermal fluid control valve is used to control the flow of compressed working fluid to the suction heat exchanger. The flow of the compressed working fluid is controlled at 1030. The flow of the compressed working fluid is controlled based on a suction superheat set point, as described in more detail below.

[0066] Controlling the flow at 1030 includes detecting a characteristic of the working fluid flowing through the suction heat exchanger at 1040. In one embodiment, the characteristic may be detected at 1040 using one or more sensors for the refrigerant circuit (e.g., sensors 92A-D, 94A, 94B, 96). The characteristic detected at 1040 may include, but is not limited to, at least one of: one or more temperatures 1042A of the working fluid, one or more pressures 1042B of the working fluid, one or more flow rates 1042C of the working fluid, one or more viscosities 1042D, one or more specific heat capacities of the working fluid, and / or one or more Prandtl numbers 1042F of the working fluid.

[0067] The detected temperature(s) 1042A may include an inlet temperature of the intake fluid (eg, inlet temperature T 1 ), the outlet temperature of the inhaled working fluid (e.g., the outlet temperature T 2 ), the inlet temperature of the compressed working fluid entering the suction heat exchanger (e.g., the inlet temperature T 3 ) and / or the outlet temperature of the compressed working fluid leaving the suction heat exchanger (e.g., outlet temperature T 4 ) in one or more of the above. The inlet temperature refers to the temperature of the working fluid flowing into the suction heat exchanger, and the outlet temperature refers to the temperature of the working fluid flowing out (e.g., discharged) from the suction heat exchanger. For example, each of the temperatures 1042A can be directly detected using various temperature sensors of the refrigerant circuit (e.g., refrigerant sensors 92A, 92B, 92C, 92D).

[0068] The detected pressure(s) 1042B may include the pressure of the suction working fluid in the suction heat exchanger (eg, pressure P 1) and / or the pressure of the compressed working fluid (e.g., pressure P 2 ) One or more of. The characteristics detected at 1040 may include the saturation temperature of the compressed working fluid and / or the saturation temperature of the suction working fluid. For example, the saturation temperature of the compressed / suction working fluid may be indirectly detected by the pressure of the compressed / suction working fluid detected at 1042B.

[0069] The detected flow rate(s) 1042C may include the flow rate (eg, mass flow rate) of the compressed working fluid flowing through the suction heat exchanger (eg, flowing through the first side of the suction heat exchanger). ). Flow 1042C may also include the flow of the heated working fluid flowing through the suction heat exchanger (eg, flowing through the second side of the suction heat exchanger). Flow 1042C may be a mass flow of the working fluid. Then, method 1000 proceeds from 1040 to 1030.

[0070] The detected viscosity (one or more) 1042D may include the viscosity of the compressed working fluid and / or the viscosity of the suction working fluid. The viscosity / dynamic viscosity may be indirectly detected from other directly detected characteristics of the working fluid (e.g., using the temperature, pressure, and / or flow rate of the working fluid detected at 1042A, 1042B, 1042C). The detected viscosity 1042D may be the dynamic viscosity of the working fluid.

[0071] The detected specific heat capacity 1042E may include the specific heat capacity of the compressed working fluid and / or the specific heat capacity of the suction working fluid. The viscosity / dynamic viscosity may be indirectly detected from other directly detected properties of the working fluid (e.g., using the temperature, pressure, and / or flow rate of the working fluid detected at 1042A, 1042B, 1042C).

[0072] like Figure 2 As shown, the flow control at 1030 also includes determining a target saturation temperature of the compressed working fluid in the suction heat exchanger at 1050. The target saturation temperature is determined based on the suction superheat set point and working fluid characteristics detected at 1040. The target saturation temperature (for the compressed working fluid) is used to provide an optimal amount of thermal energy to the suction working fluid in the suction heat exchanger. The target saturation temperature will be discussed in more detail below.

[0073] The suction superheat set point is the desired superheat of the suction flow of the compressor. The suction superheat set point can be a value previously provided by the user. For example, the suction superheat set point can be stored in the memory of the controller (e.g., the memory 91A of the controller 90). In one embodiment, the value of the predetermined suction superheat set point can be based on the working fluid (e.g., the type of refrigerant in the working fluid, the type of lubricant (e.g., oil) in the working fluid, etc.). In one embodiment, additionally or alternatively, the value of the suction superheat set point can be based on the characteristics of the compressor (e.g., compressor type, compressor configuration, current operation of the compressor, etc.). For example, the suction superheat set point can be a variable value determined based on the current operation of the compressor 10 (e.g., the predetermined variable value is a stored formula, a stored table, etc.). In one embodiment, the suction superheat set point can be a predetermined suction superheat set point (e.g., a predetermined set value, a predetermined variable value, etc.). For simplicity, the suction superheat set point may also be referred to as a superheat set point in this article. In one embodiment, the superheat set point is at least 5°F. In one embodiment, the superheat set point is at least 8°F. In one embodiment, the superheat set point is from at or about 5° F. to at or about 10° F. In one embodiment, the superheat set point is from at or about 8° F. to at or about 10° F.

[0074] In one embodiment, determining the target saturation temperature at 1050 may include determining a suction heat exchanger target logarithmic mean temperature difference (“LMΔT”) based on a suction superheat set point (“suction SSP”) and one or more detected characteristics of the working fluid flowing through the suction heat exchanger (e.g., the one or more characteristics detected at 1040). Determining the target LMΔT for the suction heat exchanger may be based on a predetermined suction SSP and one or more detected characteristics of the working fluid flowing through the suction heat exchanger (e.g., the one or more characteristics detected at 1040).

[0075] In one embodiment, a target LMΔT may be determined at 1050 based on a predetermined suction SSP and specific heat capacity, mass flow rate, and Prandtl number of the suction working fluid flowing through the suction heat exchanger. A target log mean temperature difference may also be determined based on one or more maximum severity characteristics of the suction heat exchanger.

[0076] The maximum severity characteristic refers to a characteristic of the working fluid in the suction heat exchanger when the refrigerant circuit is operated at the maximum severity setting. The maximum severity setting is the normal operating setting of the refrigerant circuit, operating the suction heat exchanger at its most severe thermal condition. For example, at the maximum severity setting, the suction heat exchanger provides high / maximum heating for the suction working fluid while having a low / minimum temperature difference between the working fluids in the suction heat exchanger. The maximum severity setting can be a normal state operation of the refrigerant circuit (e.g., not startup or shutdown of the refrigerant circuit) that provides a maximum flow rate of the suction working fluid through the suction heat exchanger and provides a minimum temperature difference between the working fluid flows in the suction heat exchanger. For example, a predetermined maximum severity setting corresponds to operation of the compressor at a predetermined maximum mass flow rate (e.g., a predetermined maximum speed) and a predetermined minimum compression (e.g., a minimum pressure difference) at the predetermined maximum mass flow rate. The maximum mass flow rate and the minimum pressure difference are for predetermined settings of the compressor (e.g., from an operating map of the compressor). The maximum severity characteristic may be determined based on previous testing of the suction heat exchanger, suction heat exchanger computational modeling, etc., and stored in a memory of a controller of the refrigerant circuit (eg, in memory 91A of controller 90).

[0077] In one example, the target LMΔT may be determined at 1050 according to the following formula (1). The superscript “*” indicates that the characteristic is the maximum severity characteristic of the working fluid in the suction heat exchanger. The subscript “s” indicates that the characteristic is the characteristic of the suction working fluid flowing through the suction heat exchanger. For example, Pr S corresponds to the characteristic (ie, Prandtl number) of the suction fluid in the suction heat exchanger in its current operation (eg, based on the characteristic detected at 1040), and Pr S *Corresponds to the same characteristic (i.e. Prandtl number) of the suction fluid in the suction heat exchanger when operating at maximum severity.

[0078] (1)

[0079] Target ΔT LM = Target logarithmic mean temperature difference

[0080] SSP = Suction superheat set point

[0081] Pr S = Prandtl number of the suction working fluid flow (e.g., detected at 1040)

[0082] μ S = Dynamic viscosity of the suction working fluid

[0083] =Mass flow rate of the working fluid sucked in

[0084] Cp,S =Specific heat capacity of the inhaled working fluid

[0085] ΔT LM =LMTD of suction heat exchanger

[0086] n = first constant (e.g. 0.8)

[0087] m = second constant (e.g. 0.4)

[0088] Determining a target LMΔT for the suction heat exchanger is based on the suction SSP and one or more detected characteristics of the working fluid flowing through the suction heat exchanger (e.g., one or more characteristics detected at 1040). In one embodiment, a target saturation temperature at 1050 may be determined based on the suction SSP, the target LMΔT (e.g., as determined at 1060), and one or more detected characteristics of the working fluid (e.g., the characteristics detected at 1040). In one example, the target saturation temperature at 1050 may be determined based on the suction SSP, the target LMΔT, and the saturation temperature of the suction working fluid in the suction heat exchanger. In one example, the target saturation temperature may be determined at 1050 according to the following formula (2):

[0089] (2)

[0090] Target T Sat,H = Target saturation temperature of the hot working fluid

[0091] T Sat,S = Detected saturation temperature of the suction working fluid

[0092] Target ΔT LM = Target log mean temperature difference (e.g., determined at 1052)

[0093] SSP = Suction superheat set point

[0094] At 1060, the thermal fluid control valve is modulated based on the target saturation temperature determined at 1050. The term "modulation" refers to adjusting the thermal fluid control valve between different open positions (e.g., partially open and / or partially closed). For example, the thermal fluid control valve moves between its intermediate positions (e.g., between a non-fully open or 100% open position and a fully closed or 0% open position). The modulation at 1060 adjusts the position of the thermal fluid control valve based on the target saturation temperature. In one embodiment, the modulation at 1060 may include one or more of adjusting the thermal fluid control valve to a more open position and adjusting the suction to a less open position.

[0095] In one embodiment, the thermal fluid control valve may be modulated based on a target saturation temperature and a detected saturation temperature of a compressed working fluid in the working fluid at 1060. For example, the detected saturation temperature may be detected at 1040 (e.g., indirectly detected from a pressure P2 of the compressed working fluid). Modulation of the thermal fluid control valve at 1060 may include comparing the target saturation temperature and the detected saturation temperature at 1062. In such an embodiment, modulation of the thermal fluid control valve at 1060 is based on the comparison at 1062.

[0096] The modulation at 1060 may be a proportional adjustment of the thermal fluid control valve based on a comparison of the target saturation temperature and the detected saturation temperature at 1062. The proportional adjustment is proportional to the difference between the target saturation temperature and the detected saturation temperature. For example, when the detected saturation temperature is greater than the target saturation temperature, the thermal fluid control valve may be further partially opened (e.g., opened by an amount proportional to the difference between the two); and when the detected saturation temperature is less than the target saturation temperature, the thermal fluid control valve may be partially closed (e.g., closed by an amount proportional to the difference between the two). The correlation / relationship between the amount of adjustment of the thermal fluid control valve and the difference between the detected saturation temperature and the target saturation temperature may be based on previous testing, computational modeling, etc. For example, such a correlation / relationship may be stored in a memory (e.g., memory 91A) of a controller of the refrigerant circuit.

[0097] In the method 1000 , the outlet temperature of the suction working fluid (eg, the outlet temperature T 2 ). In contrast, the outlet temperature is used directly to adjust the thermal fluid control valve by using a comparison / difference between the outlet temperature of the suction working fluid and the temperature of a predetermined minimum compressor suction superheat. Such direct use of the outlet temperature of the suction working fluid from the suction heat exchanger may result in a negative interaction between the control / operation of the expander and the control / operation of the thermal fluid control valve (e.g., adjustment of the expander results in adjustment of the thermal fluid control valve, which in turn results in further adjustment of the expander, which then repeats itself). In one embodiment, method 1000 may advantageously help minimize such negative control interactions in the control of suction heat.

[0098] In one embodiment, the use of a target saturation temperature in method 1000 can also help to advantageously ensure that sufficient (gaseous) compressed working fluid flow passes through and is discharged from the suction heat exchanger. Such (gaseous) compressed working fluid flow can help prevent any liquid / condensed working fluid from accumulating within the suction heat exchanger. For example, accumulation of liquid compressed working fluid in the suction heat exchanger can reduce the efficiency of the suction heat exchanger.

[0099] It should be understood that in one embodiment, method 1000 may be modified to have the same Figure 1 One or more features shown and / or described in the refrigerant circuit 2 in . For example, in one embodiment, method 1000 can be modified to include compressing the working fluid with a compressor, condensing another portion of the compressed working fluid with a condenser, expanding the working fluid with an expander, and heating the expanded working fluid in an evaporator, as described above for refrigerant circuit 2. For example, in one embodiment, method 1000 can be modified to include control of the expander (e.g., control of the hot fluid control valve at 1030) separate from control of the suction heat exchanger.

[0100] aspect:

[0101] Any of aspects 1-12 may be combined with any of aspects 13-20.

[0102] Aspect 1. A method for controlling superheat in a refrigerant circuit, the refrigerant circuit comprising a compressor, a condenser, an expander, an evaporator, and a suction heat exchanger, the refrigeration circuit containing a working fluid, the method comprising: directing the suction flow of the working fluid from the evaporator through the suction heat exchanger to the compressor; directing the first part of the working fluid compressed by the compressor from the compressor to the suction heat exchanger; and controlling the flow of the first part of the working fluid entering the suction heat exchanger using a working fluid control valve, the control comprising: detecting characteristics of the working fluid, determining a target saturation temperature of the first part of the working fluid based on a suction superheat set point and the detected characteristics of the working fluid, and modulating the working fluid control valve based on the determined target saturation temperature.

[0103] Aspect 2. A method according to aspect 1, wherein detecting the characteristics of the working fluid includes detecting the saturation temperature of a first portion of the working fluid, and modulating the working fluid control valve is based on a difference between a determined target saturation temperature and the detected saturation temperature of the first portion of the working fluid.

[0104] Aspect 3. A method according to any one of Aspects 1-2, wherein detecting the characteristics of the working fluid includes: detecting the inlet temperature, outlet temperature and pressure of the working fluid in the suction flow flowing through the suction heat exchanger, and detecting the inlet temperature, outlet temperature and pressure of the first part of the working fluid flowing through the suction heat exchanger.

[0105] Aspect 4. A method according to any one of aspects 1-3, wherein determining the target saturation temperature includes determining a target logarithmic mean temperature difference of the suction heat exchanger based on the suction superheat set point and one or more detected characteristics of the working fluid, and determining the target saturation temperature based on the suction superheat set point, the target logarithmic mean temperature difference, and the saturation temperature of the working fluid in the suction flow.

[0106] Aspect 5. A method according to Aspect 4, wherein detecting the characteristics of the working fluid includes detecting one or more of the Prandtl number, specific heat, dynamic viscosity and the saturation temperature of the working fluid in the suction flow based on the detected characteristics of the working fluid, and determining the target logarithmic mean temperature difference based on one or more of the detected Prandtl number, the detected specific heat and the detected dynamic viscosity.

[0107] Aspect 6. The method according to any one of aspects 1 to 5, wherein the target superheat temperature is determined based on the suction superheat set point and one or more maximum severity characteristics of the suction heat exchanger.

[0108] Aspect 7. The method of aspect 6, wherein the one or more maximum severity characteristics of the suction heat exchanger correspond to when the compressor is operated at a predetermined maximum mass flow rate and at a predetermined minimum compression setting at the predetermined maximum mass flow rate.

[0109] Aspect 8. A method according to any one of aspects 1 to 7, wherein modulation of the working fluid control valve adjusts the working fluid control valve between different opening positions.

[0110] Aspect 9. A method according to any one of Aspects 1-8, wherein the suction flow of the working fluid flows through a first side of the suction heat exchanger, the first part of the working fluid flows through a second side of the suction heat exchanger, and the first part of the working fluid exchanges heat with the working fluid in the suction flow flowing through the suction heat exchanger but does not physically mix.

[0111] Aspect 10. The method according to any one of Aspects 1-9 further includes: directing a second portion of the working fluid compressed by the compressor from the compressor through the condenser and the expander to the evaporator; and reuniting the first portion of the working fluid with the second portion of the working fluid downstream of the expander and upstream of the evaporator after passing through the suction heat exchanger.

[0112] Aspect 11. The method according to aspect 10, further comprising: directing the first portion of the working fluid through a flow resistor after passing through the suction heat exchanger before the first portion of the working fluid rejoins the second portion of the working fluid.

[0113] Aspect 12. The method according to any one of Aspects 10-11 further includes: utilizing the condenser to cool a second portion of the working fluid using a first process fluid; utilizing the expander to expand the second portion of the working fluid cooled in the condenser; and utilizing the evaporator to heat a second portion of the working fluid expanded by the expander using a second process fluid.

[0114] Aspect 13. A refrigerant circuit for a heating, ventilation, air conditioning and refrigeration (HVACR) system, comprising: a compressor, a condenser, an expander, an evaporator and a suction heat exchanger connected in fluid connection; a main flow path, the main flow path extending from the compressor through the condenser, the expander, the evaporator and the suction heat exchanger, and returning to the compressor; a bypass flow path extending through the suction heat exchanger, the bypass flow path extending from the main flow path downstream of the compressor and upstream of the condenser in the main flow path, the bypass flow path extending to the main flow path downstream of the expander and upstream of the suction heat exchanger; a working fluid control valve, the working fluid control valve being used to control the flow of the working fluid through the bypass flow path; one or more sensors; a controller for the refrigerant circuit, the controller being configured to: use the one or more sensors to detect a characteristic of the working fluid, determine a target saturation temperature of the working fluid in the bypass flow path flowing through the suction heat exchanger based on a predetermined suction superheat set point and the detected characteristic of the working fluid, and modulate the working fluid control valve based on the determined target saturation temperature.

[0115] Aspect 14. The refrigerant circuit according to aspect 13, wherein the controller is configured to modulate the working fluid control valve based on a difference between a detected saturation temperature of the working fluid in the bypass flow path and the determined target saturation temperature.

[0116] Aspect 15. A refrigerant circuit according to any one of Aspects 13-14, wherein the controller is configured to detect characteristics of the working fluid, including: the controller is configured to detect the pressure of the working fluid in the bypass flow path using a pressure sensor among the one or more sensors, and the controller is configured to determine the detected saturation temperature based on the pressure of the working fluid in the bypass flow path detected by the pressure sensor.

[0117] Aspect 16. A refrigerant circuit according to Aspect 15, wherein the controller is configured to: detect one or more of the Prandtl number, specific heat capacity, and dynamic viscosity of the working fluid flowing through the suction heat exchanger in the main flow path to detect the characteristics of the working fluid, and determine a target logarithmic mean temperature difference of the suction heat exchanger based on the predetermined suction superheat set point and one or more of the Prandtl number, specific heat capacity, and dynamic viscosity of the working fluid in the suction flow, and wherein the target saturation temperature is determined based on the predetermined suction superheat set point, the target logarithmic mean temperature difference, and the saturation temperature.

[0118] Aspect 17. The refrigerant circuit according to any one of aspects 13-16, wherein the target superheat temperature is determined based on the predetermined suction superheat set point and one or more maximum severity characteristics of the suction heat exchanger.

[0119] Aspect 18. A refrigerant circuit according to any one of Aspects 13-17, wherein the suction heat exchanger includes a first side and a second side, the main flow path extends through the first side of the suction heat exchanger, and the bypass flow path extends through the second side of the suction heat exchanger.

[0120] Aspect 19. The refrigerant circuit according to any one of aspects 13 to 18 further includes: a flow resistor, wherein the flow resistor is disposed in the bypass flow path downstream of the suction heat exchanger.

[0121] The terms used in this article are intended to describe specific embodiments and are not intended to be limiting. Unless otherwise expressly stated, the terms "a", "an" and "the" also include plural forms. When the terms "include" and / or "comprise" are used in this specification, it is specified that the features, integers, steps, operations, elements and / or components are present, but the presence or addition of one or more other features, integers, steps, operations, elements and / or components is not excluded. In one embodiment, "connected" and "connected" described herein may refer to "directly connected" and "directly connected".

[0122] With respect to the foregoing description, it should be understood that detailed changes may be made without departing from the scope of the present disclosure, especially in the construction materials adopted and the shapes, sizes and arrangements of the components. This specification and the described embodiments are exemplary only, and the true scope and spirit of the present disclosure are indicated by the appended claims.

Claims

1. A method for controlling superheat in a refrigerant circuit, characterized in that The refrigerant circuit includes a compressor, a condenser, an expander, an evaporator, and a suction heat exchanger, the refrigeration circuit contains a working fluid, and the method includes: directing a suction flow of the working fluid from the evaporator through the suction heat exchanger to the compressor; directing a first portion of the working fluid compressed by the compressor from the compressor to the suction heat exchanger; and Controlling the flow of the first portion of the working fluid entering the suction heat exchanger using a working fluid control valve, the controlling comprising: detecting a property of the working fluid, determining a target saturation temperature for the first portion of the working fluid based on a suction superheat set point and the sensed characteristic of the working fluid, and The working fluid control valve is modulated based on the determined target saturation temperature.

2. The method according to claim 1, characterized in that Detecting a characteristic of the working fluid includes detecting a saturation temperature of the first portion of the working fluid, and Modulating the working fluid control valve is based on a difference between the determined target saturation temperature and the detected saturation temperature of the first portion of the working fluid.

3. The method according to claim 1, characterized in that Detecting the characteristics of the working fluid includes: detecting an inlet temperature, an outlet temperature and a pressure of the working fluid in the suction flow passing through the suction heat exchanger, and An inlet temperature, an outlet temperature, and a pressure of the first portion of the working fluid flowing through the suction heat exchanger are detected.

4. The method according to claim 1, characterized in that: determining the target saturation temperature includes determining a target log mean temperature difference for the suction heat exchanger based on the suction superheat set point and one or more sensed characteristics of the working fluid, and The target saturation temperature is determined based on the suction superheat set point, the target log mean temperature difference, and a saturation temperature of the working fluid in the suction flow.

5. The method according to claim 4, characterized in that Detecting the property of the working fluid includes detecting one or more of the Prandtl number, specific heat, dynamic viscosity and the saturation temperature of the working fluid in the suction flow based on the detected property of the working fluid, and The target log mean temperature difference is determined based on one or more of the detected Prandtl number, the detected specific heat, and the detected dynamic viscosity.

6. The method according to claim 1, characterized in that The target superheat temperature is determined based on the suction superheat set point and one or more most severe characteristics of the suction heat exchanger.

7. The method according to claim 6, characterized in that The one or more maximum severity characteristics of the suction heat exchanger correspond to when the compressor is operated at a predetermined maximum mass flow rate and at a predetermined minimum compression setting at the predetermined maximum mass flow rate.

8. The method according to claim 1, characterized in that Modulation of the working fluid control valve adjusts the working fluid control valve between different opening positions.

9. The method according to claim 1, characterized in that: a suction flow of the working fluid flows through a first side of the suction heat exchanger, the first portion of the working fluid flows through a second side of the suction heat exchanger, and The first portion of the working fluid exchanges heat with, but does not physically mix with, the working fluid in the suction stream flowing through the suction heat exchanger.

10. The method according to claim 1, characterized in that Also includes: directing a second portion of the working fluid compressed by the compressor from the compressor through the condenser and expander to the evaporator; and The first portion of the working fluid is rejoined with the second portion of the working fluid downstream of the expander and upstream of the evaporator after passing through the suction heat exchanger.

11. The method according to claim 10, characterized in that Also includes: The first portion of the working fluid is directed through a flow resistor after passing through the suction heat exchanger before the first portion of the working fluid rejoins the second portion of the working fluid.

12. The method according to claim 10, characterized in that Also includes: cooling the second portion of the working fluid with a first process fluid using the condenser; expanding the second portion of the working fluid cooled in the condenser using the expander, and The second portion of the working fluid expanded by the expander is heated with a second process fluid using the evaporator.

13. A refrigerant circuit for a heating, ventilation, air conditioning and refrigeration (HVACR) system, characterized in that: The refrigerant circuit comprises: Fluid-connected compressor, condenser, expander, evaporator and suction heat exchanger, a main flow path extending from the compressor, through the condenser, the expander, the evaporator, and the suction heat exchanger, and back to the compressor; a bypass flow path extending through the suction heat exchanger, the bypass flow path extending from the main flow path downstream of the compressor and upstream of the condenser in the main flow path, the bypass flow path extending to the main flow path downstream of the expander and upstream of the suction heat exchanger; a working fluid control valve for controlling the flow of the working fluid through the bypass flow path; one or more sensors; A controller for the refrigerant circuit, the controller being configured to: detecting a property of the working fluid using the one or more sensors, determining a target saturation temperature of the working fluid in the bypass flow path through the suction heat exchanger based on a predetermined suction superheat set point and a sensed characteristic of the working fluid, and The working fluid control valve is modulated based on the determined target saturation temperature.

14. The refrigerant circuit according to claim 13, characterized in that The controller is configured to modulate the working fluid control valve based on a difference between a detected saturation temperature of the working fluid in the bypass flow path and the determined target saturation temperature.

15. The refrigerant circuit according to claim 13, characterized in that The controller is configured to detect the characteristic of the working fluid, including: the controller is configured to detect the pressure of the working fluid in the bypass flow path using a pressure sensor among the one or more sensors, and The controller is configured to determine the detected saturation temperature according to the pressure of the working fluid in the bypass flow path detected by the pressure sensor.

16. The refrigerant circuit according to claim 15, characterized in that The controller is configured to: detecting one or more of a Prandtl number, a specific heat capacity, and a dynamic viscosity of the working fluid flowing through the suction heat exchanger in the main flow path to detect a characteristic of the working fluid, and determining a target log mean temperature difference for the suction heat exchanger based on the predetermined suction superheat set point and one or more of the Prandtl number, specific heat capacity, and dynamic viscosity of the working fluid in the suction flow, and Wherein the target saturation temperature is determined based on the predetermined suction superheat set point, the target log mean temperature difference, and the saturation temperature.

17. The refrigerant circuit according to claim 13, characterized in that The target superheat temperature is determined based on the predetermined suction superheat set point and one or more most severe characteristics of the suction heat exchanger.

18. The refrigerant circuit according to claim 13, characterized in that The suction heat exchanger includes a first side and a second side, the main flow path extends through the first side of the suction heat exchanger, and the bypass flow path extends through the second side of the suction heat exchanger.

19. The refrigerant circuit according to claim 13, characterized in that: Also includes: A flow resistor is provided in the bypass flow path downstream of the suction heat exchanger.

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