JP5539996B2 - Liquid and vapor separation in a transcritical refrigerant cycle. - Google Patents

Description

  The present invention relates to refrigerant vapor compression systems, and more particularly to improving separation of a two-phase refrigerant flow into a liquid portion and a vapor portion in a refrigerant vapor compression system having a flash tank economizer and operating in a transcritical cycle.

  Refrigerant vapor compression systems are well known, and in transport refrigeration systems, air is supplied to temperature-controlled cargo spaces such as trucks, trailers, containers, etc. to transport fresh and frozen products by truck, rail, ship or combined transport. And widely used for cooling other gas fluids. In refrigerant vapor compression systems used in conjunction with transport refrigeration systems, the refrigerant vapor compression system must operate to maintain the product in the cargo space at the desired temperature over a wide range of operating load conditions and a wide range of external ambient conditions. As a result, the operating conditions are generally more severe. The desired temperature at which the cargo needs to be controlled will vary over a wide range depending on the nature of the cargo to be stored. Refrigerant vapor compression systems not only have sufficient capacity to quickly lower the temperature of products placed in the cargo space at ambient temperatures, but also at low loads to maintain a stable product temperature during transport. Must be able to drive efficiently. Furthermore, transportation refrigerant vapor compression systems are subject to vibrations and movements that are not experienced with stationary refrigerant vapor compression systems. In addition, the refrigerant vapor compression system is limited in size because there is a restriction on an available space that is not generally related to a stationary refrigerant vapor compression system, for example, an air conditioner or a heat pump.

  Traditionally, common refrigerant vapor compression systems used in transportation refrigeration applications usually operate at subcritical refrigerant pressures, and are typically compressor, condenser, evaporator, and upstream of the evaporator as refrigerant flow and condenser And an expansion device (usually an expansion valve) disposed on the downstream side. These basic refrigerant system components are connected in a refrigerant line so as to form a refrigerant closed circuit, arranged along a known refrigerant vapor compression cycle, and in a subcritical pressure range using a specific refrigerant. Driven. Refrigerant vapor compression systems operating in the subcritical range are typically filled with a fluorocarbon refrigerant, such as, but not limited to, a hydrochlorofluorocarbon (HCFC) such as R22 and R134a, R410A, R404A, R407C. Hydrofluorocarbons (HFCs) such as are more common.

  In the current market, attention has been focused on “natural” refrigerants such as carbon dioxide for use in air conditioners and transport refrigeration systems instead of HFC refrigerants. However, because carbon dioxide has a low critical temperature and the ratio of the liquid phase density to the vapor phase density is small, many refrigerant vapor compression systems filled with carbon dioxide as a refrigerant are designed to operate in a transcritical pressure mode. Has been. In a refrigerant vapor compression system that operates in a subcritical cycle, both the condenser and the heat exchanger that is the evaporator operate at a refrigerant temperature and pressure that are below the critical point of the refrigerant. However, in a refrigerant vapor compression system that operates in a transcritical cycle, the heat-dissipating heat exchanger (which is not a capacitor but rather a gas cooler) operates at a refrigerant temperature and pressure that exceeds the critical point of the refrigerant, The evaporator operates at refrigerant temperatures and refrigerant pressures in the subcritical range. Therefore, in the refrigerant vapor compression system that operates in the transcritical cycle, the pressure difference between the refrigerant pressure in the gas cooler and the refrigerant pressure in the evaporator causes the refrigerant pressure in the condenser and the evaporator in the refrigerant vapor compression system that operates in the subcritical cycle. It is characteristic that it is considerably larger than the pressure difference with the refrigerant pressure inside.

  Also, incorporating an economizer into the refrigerant circuit is widely practiced. This allows the refrigerant vapor compression system to selectively operate in the economizer mode so as to increase the capacity of the system. In some refrigerant vapor compression systems operating in transcritical mode, a flash tank economizer is incorporated between the refrigerant circuit gas cooler and the evaporator. In such a case, the refrigerant exiting the gas cooler expands through an expansion device such as a temperature-sensitive expansion valve or an electronic expansion valve, and then flows into the flash tank. Here, the expanded refrigerant is composed of a liquid refrigerant component and vapor. Separated into refrigerant components. The vapor component of the refrigerant is then led from the flash tank to the intermediate pressure stage of the compression process. The liquid component of the refrigerant is directed from the flash tank through the system's main expansion valve to the evaporator. Patent Document 1 discloses a transcritical refrigerant vapor compression system in which a flash tank economizer is incorporated between a gas cooler and an evaporator of a refrigerant circuit.

US Pat. No. 6,385,980

  A transport refrigeration refrigerant vapor compression system operating in a transcritical refrigerant cycle is connected in communication with the refrigerant circuit to compress refrigerant vapor to supercritical pressure, a gas cooler operating at supercritical refrigerant pressure, An evaporator that operates at a critical refrigerant pressure, and is further disposed between a primary expansion device that is disposed between the gas cooler and the evaporator of the refrigerant circuit, and between the gas cooler and the primary expansion device of the refrigerant circuit. And a flash tank disposed upstream of the primary expansion device and downstream of the secondary expansion device as a refrigerant flow in the refrigerant circuit.

  The flash tank includes a shell that defines an inner volume having an upper chamber, a lower chamber, and an intermediate chamber, a first fluid passage that communicates the intermediate chamber and the upper chamber, and a first fluid passage that communicates the intermediate chamber and the lower chamber. Two fluid passages, an inlet port in communication with the intermediate chamber to receive the refrigerant flow that has passed through the secondary expansion device, and a first in communication with the upper chamber to discharge a gas phase refrigerant flow from the flash tank separator. And a second outlet port in communication with the lower chamber so as to discharge a liquid phase refrigerant flow from the flash tank to the refrigerant circuit.

  In one embodiment, the flash tank includes a lower plate and an upper plate that extend apart from each other within the inner volume defined by the shell so as to divide the inner volume into an upper chamber, an intermediate chamber, and a lower chamber. Forming a first fluid passage extending through the upper plate and a second fluid passage communicating the intermediate chamber and the lower chamber to form a first fluid passage communicating the chamber and the upper chamber; And a second opening extending through the lower plate.

  In one embodiment, the flash tank defines an elongate support tube extending along the vertical central axis of the shell and a continuous helical fluid flow passage so as to define a conduit that communicates the lower and upper chambers. Thus, a spiral member extending around the support tube is provided. A first portion of the continuous helical fluid flow passage forms a first flow path that communicates the middle chamber and the upper chamber. A second portion of the continuous spiral fluid flow passage forms a second flow path that communicates the intermediate chamber and the lower chamber. An upper balancing hole extending through the support tube near the upper end of the support tube is provided to communicate the upper region of the conduit defined by the support tube with the upper chamber and is near the lower end of the support tube. A lower balancing hole extending through the support tube is provided to communicate the lower region of the conduit defined by the support tube with the lower chamber.

1 schematically illustrates a first exemplary embodiment of a refrigerant vapor compression system operating in a transcritical cycle. FIG. FIG. 3 is a diagram schematically illustrating a second exemplary embodiment of a refrigerant vapor compression system operating in a transcritical cycle. It is a cross-sectional perspective view of 1st Example of the flash tank of the refrigerant | coolant vapor compression system shown in FIG. FIG. 3 is a cross-sectional perspective view of a first exemplary embodiment of a flash tank of the refrigerant vapor compression system shown in FIG. 2.

  1 and 2 are suitable for use in a transport refrigeration system that cools air and other gas atmospheres in a temperature-controlled cargo space 200 such as trucks, trailers, and containers that transport fresh and frozen products. An exemplary embodiment of a refrigerant vapor compression system 100 is illustrated. The refrigerant vapor compression system 100 is particularly suitable for operation in a transcritical cycle using a refrigerant with a low critical temperature, such as, but not limited to, carbon dioxide. The refrigerant vapor compression system 100 includes a multistage compressor 20, a refrigerant heat dissipation heat exchanger 40, and a refrigerant heat absorption heat exchanger (herein also referred to as an evaporator) 50, and these components include a refrigerant circuit. Are connected by refrigerant circuits 2, 4 and 6 so as to communicate with each other. A primary expansion device 55 that operates in association with the evaporator 50, for example, an electronic expansion valve, is disposed between the refrigerant heat dissipation heat exchanger 40 and the evaporator 50 in the refrigerant line 4 of the refrigerant circuit. The secondary expansion device 65, for example, an electronic expansion valve, is disposed between the refrigerant heat dissipation heat exchanger 40 and the primary expansion device 55 in the refrigerant line 4 of the refrigerant circuit. Further, the flash tanks 10 </ b> A and 10 </ b> B are disposed downstream of the secondary expansion device 65 and upstream of the primary expansion device 55 as a refrigerant flow in the refrigerant line 4 of the main refrigerant circuit. Therefore, the flash tanks 10 </ b> A and 10 </ b> B are arranged downstream of the refrigerant heat dissipation heat exchanger 40 and upstream of the evaporator 50 as a refrigerant flow in the refrigerant circuit.

  In a refrigerant vapor compression system operating in a transcritical cycle, the refrigerant heat dissipation heat exchanger 40 operates at a pressure higher than the critical pressure of the refrigerant, and thus functions to cool the supercritical refrigerant vapor. The supercritical refrigerant vapor exchanges heat with a cooling medium, such as, but not limited to, ambient air or water. In the present specification, the refrigerant heat radiating heat exchanger 40 may be referred to as a gas cooler. In the illustrated embodiment, the heat radiating heat exchanger 40 includes a fin / tube heat exchanger 42 including, for example, a fin / round tube heat exchange coil or a fin / flat mini-channel tube heat exchanger. The refrigerant passing there exchanges heat with the ambient air drawn through the finned tube heat exchanger 42 by the fan 44 associated with the gas cooler 40.

  The refrigerant heat absorption heat exchanger 50 functions as an evaporator in which the liquid refrigerant passing therethrough exchanges heat with the fluid to be cooled, most commonly air or a mixture of air and an inert gas. To do. This air is drawn in from the temperature control environment 200 which is, for example, a truck, trailer or container cargo box for transport refrigeration and returned to the temperature control environment 200. In the illustrated embodiment, the refrigerant heat absorption heat exchanger 50 includes a fin-and-tube heat exchanger 52, and through this heat exchanger 52, the refrigerant is refrigerated cargo box by an evaporator fan 54 attached to the evaporator 50. Heat exchange with the air drawn in from 200 and returned to the frozen cargo box 200 is performed. The fin / tube heat exchanger 52 is, for example, a fin / round tube heat exchange coil or a fin / flat mini-channel tube heat exchanger.

  The compressor 20 functions to compress the refrigerant to a supercritical pressure and circulate the refrigerant through the main refrigerant circuit as will be described later. The compression device 20 is composed of a single multi-stage refrigerant compressor disposed in the main refrigerant circuit, for example, a scroll compressor, a screw compressor or a reciprocating compressor, and as shown in FIG. 2 compression stages 20b. The first compression stage and the second compression stage are in a serial relationship as the refrigerant flow, and the refrigerant that has left the first compression stage flows directly to the second compression stage for further compression. Alternatively, the compression device 20 can comprise a pair of independent compressors 20a, 20b connected together in a main refrigerant circuit in which the refrigerant flows in series, the compressors 20a, 20b being shown in FIG. As described above, the discharge port of the first compressor 20a and the suction port of the second compressor 20b are connected to each other through the refrigerant line 8. In independent compressor embodiments, the compressors 20a, 20b can be scroll compressors, screw compressors, reciprocating compressors, rotary compressors, or other types of compressors, or combinations of these compressors.

  In operation, the high-temperature and supercritical pressure refrigerant vapor discharged from the second compression stage of the compressor or the second compressor 20b is cooled to a low temperature when passing through the heat exchanger 42 of the gas cooler 40, and the second Passes through the expansion device 65. As it passes through the second expansion device 65, the supercritical pressure refrigerant vapor expands to a subcritical pressure at a low temperature sufficient to form a two-phase mixture of refrigerant vapor and liquid refrigerant, and the flash tank 10 Flows into.

  With particular reference to FIGS. 3 and 4, the flash tanks 10A, 10B include a shell 120 that surrounds an inner volume having an upper chamber 122, an intermediate chamber 124, and a lower chamber 126. Yes. The two-phase refrigerant flow that has passed through the secondary expansion device 65 flows into the intermediate chamber 124 through the inlet 125 that communicates with the intermediate chamber 124. The two-phase refrigerant flow received in the intermediate chamber 124 flows into the vapor phase moving upward to the upper chamber 122 of the shell 120 of the flash tank 10A, 10B, and to the lower chamber 126 of the shell 120 of the flash tank 10A, 10B. It separates into a liquid phase that moves downward. Further, the flash tanks 10 </ b> A and 10 </ b> B include a first outlet 127 that communicates with the lower chamber 126 and a second outlet 129 that communicates with the upper chamber 122.

  Liquid phase refrigerant, which is generally a saturated liquid, flows from the lower chamber 126 of the flash tanks 10A, 10B into the refrigerant line 4 of the refrigerant circuit through the first outlet 127 communicating with the lower chamber 126. In one operation mode, all of the liquid-phase refrigerant that flows from the lower chamber 126 of the flash tanks 10A and 10B is subjected to primary expansion of a refrigerant circuit that is arranged upstream of the evaporator 50 as a refrigerant flow in the refrigerant line 4. Pass through device 55. When this liquid refrigerant passes through the primary expansion device 55, the liquid refrigerant expands to a low temperature and a low pressure and flows into the evaporator 50. The evaporator 50 is a heat exchanger for evaporating the refrigerant. The expanded refrigerant flowing through the inside exchanges heat with air to be cooled, whereby the refrigerant evaporates and is generally overheated. As is common, the primary expansion device 55 maintains the superheat of the refrigerant vapor exiting the evaporator 50 at a desired level to ensure that no liquid remains in the refrigerant vapor exiting the evaporator 50. The refrigerant flow through the refrigerant line 4 is measured. The low-pressure refrigerant vapor exiting the evaporator 50 returns through the refrigerant line 6 to the first compression stage of the compressor 20 or the suction port of the first compressor 20a.

  In one embodiment, the refrigerant bypass line 5 is provided to bypass all or part of the liquid phase refrigerant flowing from the lower tank 126 of the flash tank through the refrigerant line 4 around the primary expansion device 55. be able to. The refrigerant bypass line 5 includes a first position upstream of the primary expansion device 55 as a refrigerant flow and downstream of the flash tanks 10A and 10B, and a downstream position of the primary expansion device 55 as a refrigerant flow. At the second position on the upstream side of the evaporator 50, it branches off from the refrigerant line 4. A flow control device 57, for example, a solenoid valve having an open position and a closed position is arranged in the refrigerant bypass line 5 so as to selectively open and close the bypass flow passage with respect to the refrigerant flow flowing through the refrigerant bypass line 5. be able to.

  Further, the refrigerant vapor compression system 100 includes a refrigerant vapor injection line 14, and the refrigerant vapor injection line 14 passes through the second outlet 129 of the flash tanks 10 </ b> A and 10 </ b> B and enters the shell 120 of the flash tank 10 </ b> A and 10 </ b> B. The upper chamber 122 of the defined inner volume communicates with the intermediate stage of the compression process. Further, the refrigerant vapor compression system 100 can also include a liquid refrigerant injection line 18, which is generally downstream of the flash tanks 10A, 10B as the refrigerant flow and of the primary expansion device 55. By branching from the refrigerant line 4 at a position on the upstream side, the lower chamber 126 of the inner volume defined in the shell 120 of the flash tank 10A, 10B is communicated with the intermediate stage of the compression process. In the exemplary embodiment of the refrigerant vapor compression system 100 shown in FIG. 1, the injection of refrigerant vapor or liquid refrigerant into the intermediate pressure stage of the compression process is performed from the first compression stage 20a of one compressor to the second compression. It can be achieved by injecting refrigerant vapor or liquid refrigerant into the refrigerant flowing into stage 20b. In the exemplary embodiment of the refrigerant vapor compression system 100 shown in FIG. 2, the injection of refrigerant vapor or liquid refrigerant into the intermediate pressure stage of the compression process is from the outlet of the first compressor 20a to the second compressor 20b. It can be achieved by injecting refrigerant vapor or liquid refrigerant into the refrigerant flowing through the refrigerant line 8 extending to the inlet.

  The refrigerant vapor compression system 100 can also include a compressor unloader refrigerant line 16, which communicates the intermediate pressure stage of the compressor and the suction pressure portion of the refrigerant circuit, that is, the refrigerant line 6. ing. Here, the refrigerant line 6 is connected to the outlet of the evaporator 50, the suction port of the first compression stage 20a of the compressor 20 shown in the embodiment of FIG. 1, or the first compressor 20a shown in the embodiment of FIG. It extends between the inlet. Each of the refrigerant vapor injection line 14 and the liquid refrigerant injection line 18 can be in communication with the compressor unloader refrigerant line 16 so that the compressor unloader refrigerant line 16 is both the refrigerant vapor injection line 14 and the liquid refrigerant injection line 18. Forming the downstream part of Therefore, the refrigerant vapor can flow through the refrigerant vapor injection line 14 so as to be selectively injected into the intermediate stage of the compression process or the suction pressure portion of the refrigerant circuit. Similarly, liquid refrigerant can be selectively passed through the liquid refrigerant injection line 18 so as to be selectively injected into an intermediate stage of the compression process or into the suction pressure portion of the refrigerant circuit. Further, in order to put the compressor into an unloaded state, all or part of the refrigerant discharged from the first compression stage 20a or the first compressor 20a is passed through the compressor unloader refrigerant line 16 to the suction pressure portion of the refrigerant circuit. Can be made to flow.

The refrigerant vapor compression system 100 can further include a control system having a controller 70. In one embodiment, the controller 70 can comprise a microprocessor controller, which is a MicroLink ^™ controller provided by Carrier Corporation, for example, Syracuse, NY, USA. However, the present invention is not limited to this. The controller 70 is controlled to operate the refrigeration unit to maintain a predetermined thermal environment within the enclosed inner volume 200, i.e., the cargo box, for storing the product to be transported. The controller 70 includes a compressor 20, a condenser fan 34 associated with the condenser heat exchange coil 32, an evaporator fan 44 associated with the evaporator heat exchange coil 42, and a plurality of refrigerant flows operating in conjunction with the controller 70. A predetermined thermal environment is maintained by selectively controlling the operation with the control device. A plurality of refrigerant flow controllers operating in conjunction with the controller 70 are flow controls disposed in the refrigerant line 18 to control the liquid refrigerant flow flowing through the refrigerant line 18 from the lower chamber 126 of the flash tanks 10A, 10B. A device 53 and a flow control device 73 disposed in the refrigerant line 14 to control the vapor phase refrigerant flow from the upper chamber 122 of the flash tank 10A, 10B through the refrigerant line 14 may be provided. Also, the plurality of refrigerant flow control devices operating in association with the controller 70 are flow control devices 93 disposed in the refrigerant line 16 to control the refrigerant flow flowing through the refrigerant line 16 to the suction portion of the refrigerant circuit. Can also be provided. Each of the flow control devices 53, 73, and 93 has an open position where the refrigerant can flow through the refrigerant line in which the flow control valve is arranged, and the refrigerant flows through the refrigerant line in which the flow control valve is arranged. It is possible to provide a flow control valve that can be selectively positioned between the closed position and the closed position. In one example, each of the flow control devices 53, 73, 93 includes a solenoid valve having two positions that can be selectively positioned between a first open position and a second closed position. it can. Also, the plurality of refrigerant flow control devices that operate in connection with the controller 70 can include a primary expansion valve 55, a secondary expansion valve 65, and a flow control device 57. In operation, the controller 70 operates in conjunction with the controller 70 in conjunction with the various flow controls described above to selectively guide the refrigerant flow as desired through the main refrigerant circuit and refrigerant lines 5, 14, 16, 18. The device can be selectively opened and closed.

  To facilitate control of the refrigerant system 100, the controller 70 monitors operating parameters at various points of the refrigerant system by means of a plurality of sensors located at selected locations throughout the system 100. As sensors that can be provided, although not shown in detail, an ambient air temperature sensor 90 that inputs a variable resistance value indicating the ambient air temperature at the front of the capacitor 30 to the controller 70, and a cargo box that exits the evaporator 50. Return air temperature sensor 92 that inputs a variable resistance value indicating the temperature of the air returning to 200 to controller 70, and box air temperature that inputs a variable resistance value indicating the temperature of the air in cargo box 200, that is, the product storage temperature, to controller 70. A sensor 94, a flash tank temperature sensor 101 for inputting a variable resistance value indicating the temperature of the refrigerant flowing into the flash tanks 10A and 10B to the controller 70, and a variable voltage indicating the pressure of the refrigerant flowing into the flash tanks 10A and 10B are input. The flash tank pressure sensor 102 and the refrigerant suction temperature , A compressor suction temperature sensor 103 for inputting a variable resistance value indicating the refrigerant suction pressure to the controller 70, a compressor suction pressure sensor 104 for inputting a variable voltage indicating the refrigerant suction pressure to the controller 70, and a variable resistance value indicating the refrigerant discharge refrigerant temperature. A compressor discharge temperature sensor 105 that is input to the controller 70, a compressor discharge pressure sensor 106 that inputs a variable voltage indicating the refrigerant discharge refrigerant pressure to the controller 70, and a variable resistance value that indicates the temperature of the refrigerant that has passed through the gas cooler 40. And a gas cooler temperature sensor 107 that inputs a variable voltage indicating the pressure of the refrigerant that has passed through the gas cooler 40. The pressure sensors 102, 104, 106, 108 can be general pressure sensors, for example, pressure transducers, and the temperature sensors 90, 92, 94, 101, 103, 105, 107 are general temperature sensors. For example, a thermocouple or a thermistor can be used. The above sensors are merely illustrative of some of the various sensors that may be associated with the system 100 and do not limit the types of sensors or transducers that can be provided.

  The refrigerant vapor compression system 100 operates in an operating mode selected based on load requirements and ambient conditions, such as, but not limited to, a box temperature pull-down mode, an over-freezing box temperature management mode, and a frozen product box temperature management mode. be able to. Refrigerant vapor compression system 100 defines desirable operating modes and positions various flow control valves based on ambient conditions, box conditions and various detection system controls.

  As described above, the flash tanks 10 </ b> A and 10 </ b> B are disposed upstream of the primary expansion device 55 and downstream of the secondary expansion device 65 as a refrigerant flow in the refrigerant line 4 of the refrigerant circuit. With particular reference to FIGS. 3 and 4, as described above, the flash tanks 10 </ b> A, 10 </ b> B include a shell 120 that defines an inner volume having an upper chamber 122, a lower chamber 126, and an intermediate chamber 124. The shell 120 includes a substantially cylindrical intermediate portion 120-1 extending between the upper end cap 120-2 and the lower end cap 120-3. The top cap 120-2 and the bottom cap 120-3 are attached, for example, by welding, brazing, etc., so as to form a sealed enclosure that defines the inner volume of the flash tank.

  The flash tanks 10A and 10B further include an inlet port 125, a first outlet port 127, and a second outlet port 129. The inlet port 125 is in communication with the intermediate chamber 124 to receive the refrigerant flow that has passed through the secondary expansion device. The inlet port 125 can be defined by the outlet opening of the tube 160 through the shell 120 and communicates with the refrigerant line 4 located upstream of the flash tank (as a refrigerant flow) at the inlet end of the tube 160. doing. The second outlet port 129 communicates with the upper chamber 122 so as to discharge a gas-phase refrigerant flow from the flash tanks 10A and 10B. The second outlet port 129 can be defined by the inlet opening of the tube 162 that passes through the shell 120 and is in communication with the refrigerant line 14 at the outlet end of the tube 162. The first outlet port 127 communicates with the lower chamber 126 so as to discharge a liquid-phase refrigerant flow from the flash tanks 10A and 10B to the refrigerant circuit. The first outlet port 127 can be defined by the inlet opening of the tube 164 that passes through the shell 120, and at the outlet end of the tube 164, a refrigerant line located downstream of the flash tank (as refrigerant flow). 4 communicates.

  In the embodiment of FIG. 3, the flash tank 10 </ b> A includes a lower plate 130 and an upper plate 140 that are spaced apart from each other within an inner volume defined by the shell 120. Each of the plates 130, 140 extends across the inner volume and abuts the inner circumferential wall of the generally cylindrical intermediate portion 120-1 of the shell 120 in an airtight manner, thereby bringing the inner volume of the shell 120 into three Divide into separate chambers. Here, the three individual chambers include an intermediate chamber 124 positioned between two plates 130 and 140 spaced apart from each other, an upper chamber 122 positioned between the upper plate 140 and the upper end cap 120-2, and a lower chamber. A lower chamber 126 located between the plate 130 and the lower end cap 120-3. In the present embodiment, the first fluid passage 142 is provided in the upper plate 140 and extends through the upper plate 140, thereby communicating the intermediate chamber 124 with the upper chamber 122. The second fluid passage 132 is provided in the lower plate 130 and extends through the lower plate 130, thereby communicating the intermediate chamber 124 and the lower chamber 126.

  In operation, the two-phase refrigerant flow that flows into the flash tank 10 </ b> A through the inlet tube 160 flows into the intermediate chamber 124 through the inlet port 125. In the intermediate chamber 124, the two-phase refrigerant stream is separated by the density difference between the liquid phase and the vapor phase. The vapor phase refrigerant moves through the first fluid passage 142 to the upper chamber 122 above. The liquid phase refrigerant moves through the second fluid passage 132 to the lower chamber 126 below. The outlet portion of the inlet tube 160 can be a diverging flute, which slows down the two-phase refrigerant flow when the two-phase refrigerant flow passing through the inlet port 125 flows into the intermediate chamber 124. The resulting deceleration of the two-phase refrigerant flow improves the separation of the vapor phase and the liquid phase, so that the carryover of the liquid refrigerant in the vapor phase refrigerant stream moving upward through the first fluid passage 142 ( carry over) and the vapor phase refrigerant carrier in the liquid phase refrigerant stream moving downwardly through the second fluid passage 132 is reduced. Furthermore, in order to reduce the possibility of carryover, the first fluid passage 142 and the second fluid passage 132 can be arranged to be opposite to each other along the diametrical direction. Also, the outlet end of the inlet tube 160 can extend into the intermediate chamber 124 enough to allow the inlet port 125 to be positioned opposite the top surface of the lower plate 130, and the first end of the upper plate 140. The fluid passage 142 may be disposed vertically above the flute portion of the inlet tube 160 as shown in FIG. With this arrangement, a part of the vapor phase refrigerant flows along the outer diameter of the flute portion at the outlet end portion of the inlet tube 160 to the upper first fluid passage 142, and the liquid phase of the incoming refrigerant flow is substantially the liquid phase. All can spread horizontally along the top surface of the lower plate 130. In this configuration, the second fluid passage 132 of the second plate 130 is arranged to diametrically oppose the first fluid passage 142 and thus is a turbulence located below the inlet port 125. Can be spaced from the flow region.

  Referring to the exemplary embodiment of FIG. 4, the flash tank 10 </ b> B includes a spiral member 150 that extends around a vertical support tube 152 disposed along the central axis of the shell 120. Yes. A radially outer peripheral end portion of the spiral member 150 is in airtight contact with an inner peripheral wall of the substantially cylindrical intermediate portion 120-1 of the shell 120. Thereby, the helical member 150 defines a continuous helical passage extending between the lower chamber 126 and the upper chamber 122. The inlet tube 160 is in communication with a continuous spiral passage located at a position between the upper chamber 122 and the lower chamber 126, which in this embodiment is referred to as the intermediate chamber 124. . In one embodiment, the inlet is such that a two-phase refrigerant flow entering the intermediate chamber 124 through the inlet port 125 flows tangentially along the inner peripheral wall of the generally cylindrical intermediate member 120-1 of the shell 120. A tube 160 can be placed. Due to the density difference between the vapor phase and the liquid phase, the vapor phase refrigerant in the incoming two-phase refrigerant stream generally flows upward through a continuous helical passage defined by the helical member 150, and the two-phase refrigerant flow The liquid phase refrigerant therein flows downward through a continuous spiral passage defined by the spiral member 150. The intermediate support tube 152 that supports the helical member 150 also defines an elongated conduit 155 that extends along the vertical central axis of the shell 120, thereby providing communication between the upper chamber 122 and the lower chamber 126.

  An upper balance hole 154 and a lower balance hole 156 pass through the wall of the tube 152 in the vicinity of each of the upper end portion and the lower end portion of the tube 152. The upper balance hole 154 allows the upper chamber 122 and the conduit 155 to communicate with each other, and the lower balance hole 156 allows the lower chamber 126 and the conduit 155 to communicate with each other. Due to the flow path defined between the upper balance hole 154 and the lower balance hole 156 via the conduit 155, the liquid level in the conduit 155 defined in the support tube 152 causes the level of the support tube 152 in the center of the shell 120 to increase. It becomes equal to the liquid level in the continuous spiral passage defined between the outer peripheral wall and the inner peripheral wall of the intermediate part 120-1. This fluid passage also provides a relatively stagnant refrigerant flow within conduit 155, thereby increasing the opportunity to improve phase separation.

  Unlike flash tanks used in stationary refrigeration systems, in refrigerant refrigeration applications, refrigerant vapor compression systems are subject to vibrations and movements caused by moving along roads, rails and the sea. As a result, the refrigerant in the flash tanks 10 </ b> A and 10 </ b> B jumps, so that the vapor phase and the liquid phase of the refrigerant in the flash tank can be further mixed. The plates 130, 140 or the spiral member 150 reduce the degree of splashing that results from the vibration and movement of the transport refrigeration system. Furthermore, the flash tanks 10A, 10B have internal components that substantially improve the separation between the liquid phase and the vapor phase introduced therein, thereby maximizing the difference in refrigerant enthalpy across the evaporator. Thus, the size of system components is limited, and the system performance coefficient COP and rated energy efficiency EER are optimized. Furthermore, the capacity of the refrigeration system increases due to the high quality of the refrigerant that is drawn from the flash tanks 10A, 10B and injected into the intermediate stage of the compression process. It should be understood that the flash tank 10A embodiment or the flash tank 10B embodiment can be used in the embodiment of FIG. 1 of the refrigerant vapor compression system 100 or the embodiment of FIG.

  Those skilled in the art will appreciate that many modifications can be made to particular exemplary embodiments of the invention. For example, the refrigerant vapor compression system can operate in a subcritical cycle instead of the transcritical cycle described above. While the invention has been particularly shown and described with reference to the illustrated exemplary embodiments, various modifications may be made by those skilled in the art without departing from the spirit and scope of the invention as defined by the claims. It will be understood that this can be done.

Claims (14)

A compressor for compressing refrigerant vapor to supercritical pressure, connected in communication in the refrigerant circuit, a gas cooler operating at supercritical refrigerant pressure, and an evaporator operating at subcritical refrigerant pressure;
A primary expansion device disposed between the gas cooler of the refrigerant circuit and the evaporator;
A secondary expansion device disposed between the gas cooler of the refrigerant circuit and the primary expansion device;
A flash tank disposed upstream of the primary expansion device and downstream of the secondary expansion device as a flow of refrigerant in the refrigerant circuit;
A transport refrigeration refrigerant vapor compression system operating in a transcritical refrigeration cycle comprising:
The flash tank is
A shell defining an inner volume divided into an upper chamber, a lower chamber and an intermediate chamber;
A lower plate and an upper plate that are spaced apart from each other within the inner volume defined by the shell and extend across the inner volume so as to abut the inner peripheral wall of the shell;
A first fluid passage communicating the intermediate chamber and the upper chamber;
A second fluid passage communicating the intermediate chamber and the lower chamber;
An inlet port in communication with the intermediate chamber to receive a refrigerant flow that has passed through the secondary expansion device;
A first outlet port in communication with the upper chamber to discharge a vapor phase refrigerant stream from the flash tank;
A second outlet port in communication with the lower chamber to discharge a liquid phase refrigerant flow from the flash tank to the refrigerant circuit;
A transport refrigeration refrigerant vapor compression system comprising:   The transport refrigeration refrigerant according to claim 1, further comprising a refrigerant vapor injection line that communicates the first outlet port communicating with the upper chamber of the flash tank and an intermediate pressure stage of the compression device. Vapor compression system.   2. The transport refrigeration refrigerant according to claim 1, further comprising a liquid refrigerant injection line that communicates the second outlet port communicating with the lower chamber of the flash tank and an intermediate pressure stage of the compression device. Vapor compression system. The flash tank,
To form said first fluid passage for providing communication between the before and Symbol intermediate chamber upper chamber, a first opening extending through said upper plate,
A second opening extending through the lower plate so as to form the second fluid passage communicating the intermediate chamber and the lower chamber;
The transport refrigeration refrigerant vapor compression system according to claim 1, further comprising: The flash tank is
An elongate support tube extending along a vertical central axis of the shell to define a conduit communicating the lower chamber and the upper chamber;
A helical member extending about the support tube to define a continuous helical fluid flow passage, wherein a first portion of the continuous helical fluid flow passage communicates the intermediate chamber and the upper chamber. Forming a first fluid flow path, wherein a second portion of the continuous helical fluid flow passage forms the second fluid flow path communicating the intermediate chamber and the lower chamber. Members,
The transport refrigeration refrigerant vapor compression system according to claim 1, further comprising:   The transport refrigerant refrigerant compression system according to claim 1, wherein the refrigerant is carbon dioxide.   The transport refrigeration refrigerant according to claim 1, wherein the compression device is a single compressor having at least a first relatively low pressure compression stage and a second relatively high pressure compression stage. Vapor compression system.   The compression devices are a first compressor and a second compressor, and the first compressor and the second compressor have a relationship in which refrigerant flows in series in the refrigerant circuit. The transport refrigeration refrigerant vapor compression system according to claim 1, wherein the discharge port and the suction port of the second compressor are arranged to communicate with each other. An upper balance hole extending through the support tube near the upper end of the support tube to communicate the upper region of the conduit with the upper region of the continuous spiral fluid flow passage;
A lower balance hole extending through the support tube near the lower end of the support tube to communicate the lower region of the conduit with the lower region of the continuous spiral fluid flow passage;
The transport refrigerant refrigerant compression system according to claim 5, further comprising: A shell defining an inner volume;
They are disposed separated from each other in the inner volume within which is defined by the previous SL shell, extending across the inner volume so as to be in contact with the inner peripheral wall of the shell, an upper chamber the inner volume, the intermediate chamber and the lower A lower plate and an upper plate , divided into chambers ;
A first opening extending through the upper plate to communicate the intermediate chamber and the upper chamber;
A second opening extending through the lower plate to communicate the intermediate chamber and the lower chamber;
An inlet port in communication with the intermediate chamber to receive a fluid flow comprising a mixture of a liquid phase and a vapor phase;
A first outlet port in communication with the upper chamber to discharge a vapor phase refrigerant stream from the upper chamber;
A second outlet port in communication with the lower chamber to discharge a liquid phase refrigerant stream from the lower chamber;
With flash tank separator.   The flash tank separator according to claim 10, wherein the first opening of the upper plate and the second opening of the lower plate are spaced apart from each other.   The flash tank separator of claim 10, further comprising an inlet tube having a flute-like outlet extending through the shell and defining the inlet port. A shell defining an inner volume having an upper chamber, an intermediate chamber and a lower chamber;
An elongated support tube extending between the lower chamber and the upper chamber along a vertical central axis of the shell;
A helical member extending about the support tube to define a continuous helical fluid flow passage, wherein a first portion of the continuous helical fluid flow passage connects the intermediate chamber and the upper chamber. A helical member in communication, wherein a second portion of the continuous helical fluid flow passage communicates the intermediate chamber and the lower chamber;
An upper balance hole extending through the support tube near the upper end of the support tube to communicate the upper region of the conduit with the upper region of the continuous spiral fluid flow passage;
A lower balance hole extending through the support tube near the lower end of the support tube to communicate the lower region of the conduit with the lower region of the continuous spiral fluid flow passage;
An inlet port in communication with the intermediate chamber to receive a refrigerant flow that has passed through the secondary expansion device;
A first outlet port in communication with the upper chamber to discharge a gas phase refrigerant stream from the flash tank separator;
A second outlet port in communication with the lower chamber to discharge a liquid phase refrigerant flow from the flash tank separator to the refrigerant circuit;
With flash tank separator.   An inlet tube having an outlet penetrating the shell and defining the inlet port is further provided, and the outlet of the inlet tube is circulated along the inner circumferential wall of the shell along the circumferential direction. 14. The flash tank separator according to claim 13, wherein an inflow flow of a fluid obtained by mixing the phases is guided.

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