A test device for supercritical and subcritical heat exchanger of R744

Abstract

The application discloses a kind of supercritical, subcritical heat exchanger test device satisfying R744, it is related to air-conditioning heat exchanger test technical field.The application includes primary compressor and secondary compressor, primary compressor and secondary compressor are connected in parallel by refrigerant pipeline and are arranged between gas separation and oil separation;Primary compressor and secondary compressor are also connected by first air cooler using refrigerant pipeline, and oil separation is connected with primary compressor and secondary compressor respectively by two oil return pipelines;Oil separation refrigerant outlet end is connected with condenser upper inlet and second air cooler upper inlet respectively through tee joint, condenser lower outlet is connected with liquid storage tank, and liquid storage tank is connected with evaporator through refrigerant pipeline, and evaporator liquid outlet end is connected with gas separation.The application is fast in response by setting regulating valve opening degree, and it is faster and more direct than original way of adjusting condenser water temperature or flow.

Description

Technical Field

[0001] This invention belongs to the field of air conditioning heat exchanger testing technology, and in particular relates to a testing device for supercritical and subcritical heat exchangers that meets R744 standards. Background Technology

[0002] With the ongoing global trend of replacing conventional refrigerants with environmentally friendly ones, the natural refrigerant R744 (carbon dioxide) is being widely used in large supermarkets, cold storage facilities, and new energy vehicles. However, because its operating pressure is 5-10 times higher than that of conventional refrigerants, with an operating pressure range of 5-15 MPa and an exhaust temperature reaching 130°C, all components within the refrigeration system require new development. As a crucial component of the refrigeration system, the heat exchanger's heat exchange performance, flow resistance, and flow distribution significantly impact the overall system energy efficiency; therefore, comprehensive and highly stable testing equipment is urgently needed to test it.

[0003] Currently, the application scenarios using carbon dioxide as a refrigerant are relatively limited. Therefore, the corresponding testing equipment is mainly built based on the actual systems in use, such as... Figure 1 The diagram shows the schematic of most current test systems for evaluating the performance of heat exchangers using carbon dioxide as a refrigerant. Firstly, the flow rate of the tested component is controlled in real-time by a compressor frequency converter. However, due to the limited range and large adjustment amplitude of the compressor's frequency converter, the flow control range is small, resulting in poor stability. Poor oil return processing can also easily damage the compressor. Secondly, high-pressure is controlled by the water flow or temperature on the air cooler side. However, since the critical temperature of R744 is around 31℃, above this temperature the refrigerant is in a supercritical state, where temperature and saturation pressure do not correspond, leading to poor control stability. Furthermore, the strong thermal inertia of the water circuit results in slow control speed. Thirdly, single-unit compressor operation: using a single compressor limits the overall test system's control range, making some high-pressure conditions uncontrollable. Fourth, switching between evaporator and condenser requires reversing the expansion valve flow direction and position: Because the flow direction of samples differs when testing evaporators and condensers, this method necessitates reversing the expansion valve flow rate and position for different sample types, resulting in low testing efficiency and preventing automatic switching between defrosting and defrosting modes. Fifth, condenser inlet temperature control relies on compressor discharge temperature control: When testing high-temperature inlet conditions, the inlet temperature depends on the compressor discharge temperature, which in turn depends on the compressor suction superheat, causing stability deviations and a narrow control range.

[0004] Existing testing devices for supercritical and subcritical heat exchangers that meet R744 requirements suffer from poor stability and narrow control range when testing heat exchangers. The high pressure required for testing is provided solely by the condenser, resulting in slow testing speed. Furthermore, the single-unit operation of the compressor leads to a small operating condition control range, making it impossible to test high-pressure ratio conditions. Switching between testing the evaporator and condenser requires reversing the expansion valve, preventing automatic switching of the tested components and resulting in low testing efficiency. Therefore, this invention proposes a testing device for supercritical and subcritical heat exchangers that meets R744 requirements. Summary of the Invention

[0005] The purpose of this invention is to provide a testing device for supercritical and subcritical heat exchangers of R744, solving the problems of poor stability, narrow control range, slow testing speed, limited control range due to the single-unit operation of the compressor, inability to test high-pressure ratio conditions, and the inability to automatically switch between the tested evaporator and condenser when switching between them, resulting in low testing efficiency.

[0006] To solve the above-mentioned technical problems, the present invention is achieved through the following technical solution:

[0007] This invention relates to a testing device for supercritical and subcritical heat exchangers meeting R744 standards. It includes a primary compressor and a secondary compressor, which are connected in parallel between a gas separator and an oil separator via refrigerant piping. The primary and secondary compressors are also connected via a first gas cooler through a refrigerant piping. The oil separator is connected to both the primary and secondary compressors via two return oil pipes. The refrigerant outlet of the oil separator is connected to the upper inlet of the condenser and the upper inlet of the second gas cooler via a tee. The lower outlet of the condenser is connected to a liquid storage tank, which is connected to an evaporator via a refrigerant piping. The liquid outlet of the evaporator is connected to the gas separator. The lower outlet of the second gas cooler is connected to the upper inlet of an oil heater. The lower outlet of the oil heater is connected via a tee, with one end connected to the gas separator via a refrigerant piping and the other end connected to the test piece. One end of the test piece is connected to the gas separator.

[0008] Preferably, a pressure control point PSE1 and a temperature control point TIS1 are respectively provided at the outlet end of the gas separator; a temperature control point TWS1 and a pneumatic ball valve UNS1 are respectively provided at the inlet end of the first-stage compressor; and a pneumatic ball valve UNS2 and a temperature control point TWS2 are respectively provided at the outlet end of the first-stage compressor; a temperature control point TIS3 and a pneumatic ball valve UNS4 are respectively provided at the inlet end of the second-stage compressor; and a pneumatic ball valve UNS5 and a temperature control point TWS4 are respectively provided at the outlet end of the second-stage compressor; a pneumatic ball valve UNS25 is provided at the lower inlet end of the first air cooler, and a pneumatic ball valve UNS26 is provided at the upper outlet end of the first air cooler.

[0009] Preferably, a regulating valve UNW5 is installed at the liquid inlet of the condenser, and a pneumatic ball valve UNS28 is connected in parallel to the regulating valve UNW5; the liquid outlet of the storage tank is connected to the inlet of the second gas cooler through a refrigerant pipeline, and a pneumatic ball valve UNS29 is installed on the refrigerant pipeline; a pneumatic ball valve UNS13 is installed near the inlet of the second gas cooler; a pneumatic ball valve UNS14 is installed on the refrigerant pipeline connecting the lower outlet of the oil heater to the gas separator; and a series of pneumatic ball valves are installed on the refrigerant pipeline connecting the lower outlet of the oil heater to the end of the test piece. The system includes a pneumatic ball valve UNS18, a connecting system hose LHS1, a pneumatic ball valve UNS19, a pressure control point PSE5, a temperature control point TIS5, a regulating valve UNW1, a pneumatic ball valve UNS20, a connecting system hose LHS2, a pressure control point PSE6, and a temperature control point TIS6; a pneumatic ball valve UNS15 is connected in parallel between the liquid inlet of the pressure control point PSE5 and the liquid outlet of the pneumatic ball valve UNS20; a pneumatic ball valve UNS16 is connected in parallel between the liquid inlet of the pneumatic ball valve UNS19 and the liquid outlet of the regulating valve UNW1.

[0010] Preferably, the other end of the test piece is connected to the refrigerant pipeline of the gas separator, which is sequentially connected to a temperature control point TIS7, a pressure control point PSE7, a connecting system hose LHS3, and a pneumatic ball valve UNS21; wherein, the pressure control point PSE7 and the pressure control point PSE6 are connected by a differential pressure control point.

[0011] Preferably, a refrigerant pipe extends outward from the refrigerant pipe between the pneumatic ball valve UNS18 and the connecting system hose LHS1 and connects to the liquid inlet of the evaporator, and a pneumatic ball valve UNS17 is installed on the refrigerant pipe; a regulating valve UNW3 is installed between the liquid storage tank and the evaporator.

[0012] Preferably, when testing the evaporator under supercritical conditions according to R744, the primary and secondary compressors are kept in parallel, and the pneumatic ball valves UNS29, UNS14, UNS17, UNS1, and UNS15 are closed. After the refrigerant passes through the primary and secondary compressors in parallel, the oil separator is used to separate the compressor oil discharged from the two compressors. After passing through the oil separator, the refrigerant is divided into two liquid paths. In one liquid path, the refrigerant flows sequentially through the second air cooler, oil heater, pressure control point PSE5, temperature control point TIS5, the tested evaporator, temperature control point TIS7, and pressure control point PSE7 until the gas separation completes one loop. In the other liquid path, the refrigerant flows sequentially through the regulating valve UNW5, condenser, and evaporator until the gas separation completes one loop.

[0013] Preferably, when testing the condenser under supercritical conditions (R744), the primary and secondary compressors are kept in parallel, and the pneumatic ball valves UNS21, UNS19, and UNS20 are closed. The refrigerant is divided into two liquid paths after oil separation. In one liquid path, the refrigerant flows sequentially through the second air cooler, oil heater, pneumatic ball valve UNS14, pressure control point PSE7, temperature control point TIS7, the tested condenser, pneumatic ball valve UNS15, pneumatic ball valve UNS16, and evaporator until the gas separation completes one loop. In the other liquid path, the refrigerant flows sequentially through the regulating valve UNW5, condenser, liquid receiver, and evaporator until the gas separation completes one loop. The liquid outlet of the liquid receiver and the liquid inlet of the second air cooler are connected by a refrigerant pipeline.

[0014] Preferably, when testing the evaporator under the R744 subcritical state, the primary compressor and the secondary compressor are kept in parallel, and the regulating valve UNW5, pneumatic ball valve UNS13, pneumatic ball valve UNS14, pneumatic ball valve UNS15, pneumatic ball valve UNS16, and pneumatic ball valve UNS17 are closed. The refrigerant discharged from the compressor passes through the oil separator, pneumatic ball valve UNS28, condenser, and liquid receiver in sequence, and then splits into two liquid paths. In one liquid path, the refrigerant flows through pneumatic ball valve UNS29, the second air cooler, the oil heater, pneumatic ball valve UNS18, pneumatic ball valve UNS19, pneumatic ball valve UNS20, the tested evaporator, and pneumatic ball valve UNS21 until the gas separator completes one loop. In the other liquid path, the refrigerant flows through the evaporator in sequence until the gas separator completes one loop.

[0015] Preferably, when testing the condenser under the R744 subcritical state, the primary compressor and the secondary compressor are kept in parallel, and the regulating valve UNW5, pneumatic ball valve UNS29, pneumatic ball valve UNS18, pneumatic ball valve UNS19, pneumatic ball valve UNS20, and pneumatic ball valve UNS21 are closed. The refrigerant discharged from the compressor is divided into two liquid paths after passing through the oil separator. In one liquid path, the refrigerant flows sequentially through the second air cooler, oil heater, pneumatic ball valve UNS14, the tested condenser, pneumatic ball valve UNS15, pneumatic ball valve UNS16, pneumatic ball valve UNS17, and evaporator until the gas separation completes one loop. In the other liquid path, the refrigerant flows sequentially through pneumatic ball valve UNS28, condenser, liquid receiver, and evaporator until the gas separation completes one loop.

[0016] Preferably, the parameters to be controlled for the evaporator test sample include: inlet valve pressure PSE5: controlled by the condenser during subcritical testing and by the regulating valve UNW5 during supercritical testing; inlet valve temperature TIS5: controlled by the second air cooler and oil heater; evaporator outlet pressure PSE7: controlled by the auxiliary regulating valve UNW3; evaporator outlet temperature TIS7: controlled by the main regulating valve UNW1.

[0017] The parameters that need to be controlled for the condenser test specimen include: condenser inlet pressure PSE7: controlled by the condenser during subcritical testing, and controlled by regulating valve UNW5 during supercritical testing; condenser inlet temperature TIS7: controlled by the second air cooler and oil heater; condenser outlet temperature TIS6: controlled by the main regulating valve UNW1. In this invention, the evaporator and condenser are the testing mechanisms in the testing device, and the evaporator and condenser of the test specimen are the test specimens.

[0018] The present invention has the following beneficial effects:

[0019] 1. This invention tests the evaporator under test and controls four parameters on the refrigerant side of the evaporator: inlet temperature, inlet pressure, outlet temperature, and outlet pressure. These four parameters correspond to the inlet and outlet enthalpy values ​​of the evaporator under test, respectively. When the operating conditions are stable, the heat exchange on the refrigerant side of the evaporator under test is obtained by multiplying the inlet and outlet enthalpy values ​​by the flow rate.

[0020] 2. This invention tests the condenser of the test component and controls three parameters on the refrigerant side of the condenser: condenser inlet temperature, condenser inlet pressure, and condenser outlet temperature. These four parameters, along with the measured condenser outlet pressure, correspond to the inlet and outlet enthalpy values ​​of the condenser under test. When the operating conditions are stable, the heat exchange on the refrigerant side of the condenser under test is obtained by multiplying the inlet and outlet enthalpy values ​​by the flow rate.

[0021] 3. This invention controls the refrigerant flow in the test circuit by using frequency converters for the auxiliary primary and secondary compressors and the auxiliary flow regulating valve UNW3 to divert the refrigerant flow. The auxiliary primary and secondary compressors operate at high, medium, and low frequencies to fix the approximate total refrigerant flow in the system. The refrigerant flow is then diverted through the auxiliary flow regulating valve UNW3 to achieve precise control of the refrigerant flow in the test circuit.

[0022] 4. This invention controls the compressor discharge pressure by adjusting the opening degree of the regulating valve UNW5, thereby controlling the inlet pressure PSE5 during evaporator testing and the inlet pressure PSE7 during condenser testing. Because the regulating valve has a fast response time, this method is faster and more direct than the previous method of adjusting the condenser water temperature or flow rate. Attached Figure Description

[0023] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0024] Figure 1 This is a schematic diagram of the original supercritical heat exchanger test principle.

[0025] Figure 2 General diagram of the testing device for R744 supercritical and subcritical heat exchangers provided by the present invention;

[0026] Figure 3 The parallel operation diagram of the compressors provided by this invention;

[0027] Figure 4 The compressor series operation diagram provided by the present invention;

[0028] Figure 5 The subcritical evaporator test operation diagram provided by this invention;

[0029] Figure 6 The subcritical condenser test operation diagram provided for this invention;

[0030] Figure 7 The supercritical evaporator test operation diagram provided by this invention;

[0031] Figure 8 The diagram shows the test operation of the supercritical condenser provided by this invention.

[0032] The attached diagram lists the components represented by each number as follows:

[0033] 1. Primary compressor; 2. Secondary compressor; 3. First air cooler; 4. Oil separator; 5. Gas separator; 6. Condenser; 7. Secondary air cooler; 8. Oil heater; 9. Liquid receiver; 10. Evaporator. Detailed Implementation

[0034] To make the technical means, creative features, objectives and effects of this invention easier to understand, the invention will be further described below in conjunction with specific embodiments.

[0035] See Figure 2-4 This invention relates to a testing device for supercritical and subcritical heat exchangers meeting the R744 standard. It includes a primary compressor 1 and a secondary compressor 2, which are connected in parallel between a gas separator 5 and an oil separator 4 via refrigerant pipelines. The primary compressor 1 and secondary compressor 2 are also connected via a first air cooler 3 through a refrigerant pipeline. The oil separator 4 is connected to both the primary compressor 1 and the secondary compressor 2 via two return oil pipelines. The refrigerant outlet of the oil separator 4 is connected via a tee to the upper inlet of a condenser 6 and the upper inlet of a second air cooler 7. The lower outlet of the condenser 6 is connected to a liquid storage tank 9, which is connected to an evaporator 10 via a refrigerant pipeline. The liquid outlet of the evaporator 10 is connected to the gas separator 5. The lower outlet of the second air cooler 7 is connected to the upper inlet of an oil heater 8. The lower outlet of the oil heater 8 is connected via a tee, with one end connected to the gas separator 5 via a refrigerant pipeline and the other end connected to the test piece. The test piece is connected to the gas separator 5 at one end; the first and second auxiliary compressors provide refrigerant flow to the test system and establish a system operating pressure differential; the first air cooler controls the suction temperature of the second-stage compressor when compressors are connected in series; the oil separator separates the compressor oil from the refrigerant discharged from the auxiliary compressor and returns it to the compressor through pipelines; the gas separator ensures that the compressor suction is free of liquid; all starting ball valves are used to switch the refrigerant flow path in the system; the regulating valve is used to adjust the refrigerant flow in the corresponding flow path and control the temperature and pressure measurement points in the system; the condenser controls the intermediate pressure of the system in the supercritical state and the high pressure of the system in the subcritical state; the second air cooler and the oil heater are used to control the temperature before the valve or the inlet temperature of the condenser; the evaporator is used to control the suction superheat of the auxiliary compressor; the liquid receiver is used to store and buffer the amount of refrigerant in the system; the connecting hose is used to connect the moving parts and the test sample.

[0036] Among them, the outlet end of gas separator 5 is equipped with pressure control point PSE1 and temperature control point TIS1 respectively; the inlet end of primary compressor 1 is equipped with temperature control point TWS1 and pneumatic ball valve UNS1 respectively; and the outlet end of primary compressor 1 is equipped with pneumatic ball valve UNS2 and temperature control point TWS2 respectively; the inlet end of secondary compressor 2 is equipped with temperature control point TIS3 and pneumatic ball valve UNS4 respectively; and the outlet end of secondary compressor 2 is equipped with pneumatic ball valve UNS5 and temperature control point TWS4 respectively; the lower inlet of the first air cooler 3 is equipped with pneumatic ball valve UNS25, and the upper outlet of the first air cooler 3 is equipped with pneumatic ball valve UNS26.

[0037] A regulating valve UNW5 is installed at the liquid inlet of condenser 6, and a pneumatic ball valve UNS28 is connected in parallel to the regulating valve UNW5; the liquid outlet of the liquid storage tank 9 is connected to the inlet of the second air cooler 7 via a refrigerant pipeline, and a pneumatic ball valve UNS29 is installed on this refrigerant pipeline; a pneumatic ball valve UNS13 is installed near the inlet of the second air cooler 7; a pneumatic ball valve UNS14 is installed on the refrigerant pipeline connecting the lower outlet of the oil heater 8 to the gas separator 5; and a series of pneumatic ball valves are installed on the refrigerant pipeline connecting the lower outlet of the oil heater 8 to the end of the test piece. The system includes a pneumatic ball valve UNS18, a connecting system hose LHS1, a pneumatic ball valve UNS19, a pressure control point PSE5, a temperature control point TIS5, a regulating valve UNW1, a pneumatic ball valve UNS20, a connecting system hose LHS2, a pressure control point PSE6, and a temperature control point TIS6; a pneumatic ball valve UNS15 is connected in parallel between the inlet end of the pressure control point PSE5 and the outlet end of the pneumatic ball valve UNS20; a pneumatic ball valve UNS16 is connected in parallel between the inlet end of the pneumatic ball valve UNS19 and the outlet end of the regulating valve UNW1.

[0038] The other end of the tested component is connected to the refrigerant pipeline of gas separator 5, which is sequentially connected to temperature control point TIS7, pressure control point PSE7, connecting system hose LHS3 and pneumatic ball valve UNS21; among them, pressure control point PSE7 and pressure control point PSE6 are connected by differential pressure control point.

[0039] Among them, a refrigerant pipe extends outward from the refrigerant pipe between the pneumatic ball valve UNS18 and the connecting system hose LHS1 and connects to the liquid inlet of the evaporator 10, and a pneumatic ball valve UNS17 is installed on the refrigerant pipe; a regulating valve UNW3 is installed between the liquid storage tank 9 and the evaporator 10.

[0040] Among them, the parameters that need to be controlled for the evaporator test sample include: valve inlet pressure PSE5: controlled by condenser 6 during subcritical testing and by regulating valve UNW5 during supercritical testing; valve inlet temperature TIS5: controlled by the second air cooler 7 and oil heater 8; evaporator outlet pressure PSE7: controlled by auxiliary regulating valve UNW3; evaporator outlet temperature TIS7: controlled by main regulating valve UNW1.

[0041] The parameters that need to be controlled for the condenser test sample under test include: condenser inlet pressure PSE7: controlled by condenser 6 during subcritical testing and by regulating valve UNW5 during supercritical testing; condenser inlet temperature TIS7: controlled by the second air cooler 7 and oil heater 8; condenser outlet temperature TIS6: controlled by the main regulating valve UNW1.

[0042] Since a single compressor has its own operating range limitation, and under supercritical operating conditions, the operating pressure ratio required for the test of the device under test may exceed the compressor's operating range under some heat pump conditions, in order to avoid excessively high compressor discharge temperature and ensure reliable compressor operation, two auxiliary compressors are connected in series to operate in relay mode. At this time, auxiliary compressor MCM1 is the first-stage compressor (low-pressure stage), and auxiliary compressor MCM2 is the high-pressure stage. The discharge from the first-stage compressor is cooled by the intermediate air cooler XPE1 and then enters the suction end of the second-stage compressor to achieve high-pressure ratio operation.

[0043] Example 1

[0044] See Figure 7 When testing the evaporator under supercritical conditions according to R744, the first-stage compressor 1 and the second-stage compressor 2 are kept in parallel. At the same time, pneumatic ball valves UNS29, UNS14, UNS17, UNS1, and UNS15 are closed. After the refrigerant passes through the first-stage compressor 1 and the second-stage compressor 2 in parallel, the oil separator 4 is used to separate the compressor oil in the refrigerant discharged from the two compressors. After passing through the oil separator 4, the refrigerant is divided into two liquid paths. In one liquid path, the refrigerant flows sequentially through the second air cooler 7, the oil heater 8, the pressure control point PSE5, the temperature control point TIS5, the tested evaporator, the temperature control point TIS7, the pressure control point PSE7, and finally to the gas separator 5 to complete one loop. In the other liquid path, the refrigerant flows sequentially through the regulating valve UNW5, the condenser 6, the evaporator 10, and finally to the gas separator 5 to complete one loop.

[0045] Example 2

[0046] See Figure 8When testing the condenser under supercritical conditions according to R744, the first-stage compressor 1 and the second-stage compressor 2 are kept in parallel, and pneumatic ball valves UNS21, UNS19, and UNS20 are closed. The refrigerant is divided into two liquid paths after passing through the oil separator 4. In one liquid path, the refrigerant flows sequentially through the second air cooler 7, the oil heater 8, the pneumatic ball valve UNS14, the pressure control point PSE7, the temperature control point TIS7, the tested condenser, the pneumatic ball valve UNS15, the pneumatic ball valve UNS16, the evaporator 10, and finally to the gas separator 5 to complete one loop. In the other liquid path, the refrigerant flows sequentially through the regulating valve UNW5, the condenser 6, the liquid receiver 9, the evaporator 10, and finally to the gas separator 5 to complete one loop. The liquid outlet of the liquid receiver 9 is connected to the liquid inlet of the second air cooler 7 through a refrigerant pipeline.

[0047] Example 3

[0048] See Figure 5 When testing the evaporator under the subcritical state of R744, the primary compressor 1 and the secondary compressor 2 are kept in parallel. At the same time, the regulating valve UNW5, pneumatic ball valve UNS13, pneumatic ball valve UNS14, pneumatic ball valve UNS15, pneumatic ball valve UNS16, and pneumatic ball valve UNS17 are closed. The refrigerant discharged from the compressor passes through the oil separator 4, pneumatic ball valve UNS28, condenser 6, and liquid receiver 9 in sequence, and then splits into two liquid paths. In one liquid path, the refrigerant flows through the pneumatic ball valve UNS29, the second air cooler 7, the oil heater 8, the pneumatic ball valve UNS18, the pneumatic ball valve UNS19, the pneumatic ball valve UNS20, the tested evaporator, and the pneumatic ball valve UNS21 until the gas separator 5 completes one loop. In the other liquid path, the refrigerant flows through the evaporator 10 until the gas separator 5 completes one loop.

[0049] Example 4

[0050] See Figure 6 When testing the condenser under subcritical conditions according to R744, the first-stage compressor 1 and the second-stage compressor 2 are kept in parallel. At the same time, the regulating valve UNW5, pneumatic ball valve UNS29, pneumatic ball valve UNS18, pneumatic ball valve UNS19, pneumatic ball valve UNS20, and pneumatic ball valve UNS21 are closed. The refrigerant discharged from the compressor passes through the oil separator 4 and is divided into two liquid paths. In one liquid path, the refrigerant flows sequentially through the second air cooler 7, the oil heater 8, the pneumatic ball valve UNS14, the tested condenser, the pneumatic ball valve UNS15, the pneumatic ball valve UNS16, the pneumatic ball valve UNS17, the evaporator 10, and finally to the gas separator 5 to complete one loop. In the other liquid path, the refrigerant flows sequentially through the pneumatic ball valve UNS28, the condenser 6, the liquid receiver 9, the evaporator 10, and finally to the gas separator 5 to complete one loop.

[0051] When the refrigerant system is running under different test types, ball valves UNS15, UNS16, UNS19, and UNS20 are switched on and off according to the evaporation test and the condensation test of the tested component. When testing the evaporator, UNS15 and UNS16 are closed, and UNS19 and UNS20 are open. When testing the condenser, UNS15 and UNS16 are open, and UNS19 and UNS20 are closed. This ensures that the flow direction of the expansion valve remains unchanged and also enables automatic switching between the condenser and evaporator operating conditions.

[0052] The condenser inlet temperature is controlled by the second air cooler and the oil heater.

[0053] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of this invention is defined by the appended claims and their equivalents.

Claims

1. A testing device for supercritical and subcritical heat exchangers meeting the R744 standard, characterized in that: It includes a primary compressor (1) and a secondary compressor (2), which are connected in parallel between the gas separator (5) and the oil separator (4) via refrigerant pipelines; the primary compressor (1) and the secondary compressor (2) are also connected to each other via a first air cooler (3) through a refrigerant pipeline; the oil separator (4) is connected to the primary compressor (1) and the secondary compressor (2) respectively via two oil return pipelines; the refrigerant outlet of the oil separator (4) is connected to the condenser (5) via a tee. 6) The upper inlet and the upper inlet of the second air cooler (7) are connected. The lower outlet of the condenser (6) is connected to the liquid storage tank (9). The liquid storage tank (9) is connected to the evaporator (10) through a refrigerant pipe. The liquid outlet of the evaporator (10) is connected to the gas separator (5). The lower outlet of the second air cooler (7) is connected to the upper inlet of the oil heater (8). The lower outlet of the oil heater (8) is connected to the gas separator (5) through a tee. One end is connected to the gas separator (5) through a refrigerant pipe, and the other end is connected to the test piece. The other end of the test piece is connected to the gas separator (5). The gas separator (5) is equipped with a pressure control point PSE1 and a temperature control point TIS1 at its outlet. The first-stage compressor (1) is equipped with a temperature control point TWS1 and a pneumatic ball valve UNS1 at its air inlet; and the first-stage compressor (1) is equipped with a pneumatic ball valve UNS2 and a temperature control point TWS2 at its air outlet; the second-stage compressor (2) is equipped with a temperature control point TIS3 and a pneumatic ball valve UNS4 at its air inlet; and the second-stage compressor (2) is equipped with a pneumatic ball valve UNS5 and a temperature control point TWS4 at its air outlet; the first air cooler (3) is equipped with a pneumatic ball valve UNS25 at its lower inlet and a pneumatic ball valve UNS26 at its upper outlet; A regulating valve UNW5 is installed at the liquid inlet of the condenser (6), and a pneumatic ball valve UNS28 is connected in parallel to the regulating valve UNW5; a pneumatic ball valve UNS13 is installed near the tee position at the inlet end of the second air cooler (7), and the liquid outlet of the liquid storage tank (9) is connected to the refrigerant pipeline between the second air cooler (7) and the pneumatic ball valve UNS13 through a refrigerant pipeline, and a pneumatic ball valve UNS29 is installed on the refrigerant pipeline; a pneumatic ball valve UNS14 is installed on the refrigerant pipeline connecting the lower outlet end of the oil heater (8) to the gas separator (5), and the lower outlet end of the oil heater (8) is connected to the gas separator (5). A pneumatic ball valve UNS18, a connecting system hose LHS1, a pneumatic ball valve UNS19, a pressure control point PSE5, a temperature control point TIS5, a regulating valve UNW1, a pneumatic ball valve UNS20, a connecting system hose LHS2, a pressure control point PSE6, and a temperature control point TIS6 are sequentially installed on the refrigerant pipeline connected to the test component. A pneumatic ball valve UNS15 is connected in parallel between the liquid inlet of the pressure control point PSE5 and the liquid outlet of the pneumatic ball valve UNS20. A pneumatic ball valve UNS16 is connected in parallel between the liquid inlet of the pneumatic ball valve UNS19 and the liquid outlet of the regulating valve UNW1. The other end of the test piece is connected to the refrigerant pipe of the gas separator (5), which is sequentially connected to a temperature control point TIS7, a pressure control point PSE7, a connecting system hose LHS3, and a pneumatic ball valve UNS21; wherein, the pressure control point PSE7 and the pressure control point PSE6 are connected by a differential pressure control point. A refrigerant pipe extends outward from the refrigerant pipe between the pneumatic ball valve UNS18 and the connecting system hose LHS1 and connects to the liquid inlet of the evaporator (10), and a pneumatic ball valve UNS17 is installed on the refrigerant pipe; a regulating valve UNW3 is installed between the liquid storage tank (9) and the evaporator (10); The parameters that need to be controlled for the evaporator under test include: valve inlet pressure PSE5: controlled by the condenser (6) during subcritical testing and by the regulating valve UNW5 during supercritical testing; valve inlet temperature TIS5: controlled by the second air cooler (7) and the oil heater (8); evaporator outlet pressure PSE7: controlled by the auxiliary regulating valve UNW3; evaporator outlet temperature TIS7: controlled by the main regulating valve UNW1. The parameters that need to be controlled for the condenser of the test component include: the inlet pressure of the condenser PSE7: controlled by the condenser (6) during subcritical testing and by the regulating valve UNW5 during supercritical testing; the inlet temperature of the condenser TIS7: controlled by the second air cooler (7) and the oil heater (8); and the outlet temperature of the condenser TIS6: controlled by the main regulating valve UNW1.

2. The testing device for supercritical and subcritical heat exchangers according to claim 1, characterized in that, When testing the evaporator of the test component under supercritical conditions as per R744, the first-stage compressor (1) and the second-stage compressor (2) are kept in parallel. At the same time, the pneumatic ball valves UNS29, UNS14, UNS17, UNS1, and UNS15 are closed. After the refrigerant passes through the first-stage compressor (1) and the second-stage compressor (2) in parallel, the oil separator (4) is used to separate the compressor oil in the refrigerant discharged by the two compressors. After passing through the oil separator (4), the refrigerant is divided into two liquid paths. In one liquid path, the refrigerant flows sequentially through the second air cooler (7), the oil heater (8), the pressure control point PSE5, the temperature control point TIS5, the evaporator of the test component, the temperature control point TIS7, the pressure control point PSE7 until the gas separator (5) completes a loop. In the other liquid path, the refrigerant flows sequentially through the regulating valve UNW5, the condenser (6), the liquid storage tank (9), the evaporator (10) until the gas separator (5) completes a loop.

3. The testing device for supercritical and subcritical heat exchangers according to claim 2, characterized in that, When testing the condenser of the test component under supercritical conditions as per R744, the first-stage compressor (1) and the second-stage compressor (2) are kept in parallel, and the pneumatic ball valves UNS21, UNS19 and UNS20 are closed. The refrigerant is divided into two liquid paths after passing through the oil separator (4). In one liquid path, the refrigerant flows sequentially through the second air cooler (7), the oil heater (8), the pneumatic ball valve UNS14, the pressure control point PSE7, the temperature control point TIS7, the condenser of the test component, the pneumatic ball valve UNS15, the pneumatic ball valve UNS16, the evaporator (10) and finally to the gas separator (5) to complete a loop. In the other liquid path, the refrigerant flows sequentially through the regulating valve UNW5, the condenser (6), the liquid storage tank (9), the evaporator (10) and finally to the gas separator (5) to complete a loop.

4. The testing device for supercritical and subcritical heat exchangers meeting the requirements of claim 3, characterized in that, When testing the evaporator of the test component under subcritical conditions of R744, the first-stage compressor (1) and the second-stage compressor (2) are kept in parallel, and the regulating valve UNW5, pneumatic ball valve UNS13, pneumatic ball valve UNS14, pneumatic ball valve UNS15, pneumatic ball valve UNS16 and pneumatic ball valve UNS17 are closed. The refrigerant discharged from the compressor passes through the oil separator (4), pneumatic ball valve UNS28, condenser (6) and liquid tank (9) in sequence and is divided into two liquid paths. In one liquid path, the refrigerant flows through the pneumatic ball valve UNS29, the second air cooler (7), the oil heater (8), the pneumatic ball valve UNS18, the pneumatic ball valve UNS19, the pneumatic ball valve UNS20, the evaporator of the test component, the pneumatic ball valve UNS21 until the gas separator (5) to complete one loop. In the other liquid path, the refrigerant flows through the evaporator (10) until the gas separator (5) to complete one loop.

5. The testing device for supercritical and subcritical heat exchangers according to claim 4, characterized in that, When testing the condenser of the test component under subcritical conditions of R744, the first-stage compressor (1) and the second-stage compressor (2) are kept in parallel, and the regulating valve UNW5, pneumatic ball valve UNS29, pneumatic ball valve UNS18, pneumatic ball valve UNS19, pneumatic ball valve UNS20 and pneumatic ball valve UNS21 are closed. The refrigerant discharged from the compressor passes through the oil separator (4) and is divided into two liquid paths. In one liquid path, the refrigerant flows sequentially through the second air cooler (7), oil heater (8), pneumatic ball valve UNS14, the condenser of the test component, pneumatic ball valve UNS15, pneumatic ball valve UNS16, pneumatic ball valve UNS17, evaporator (10) until the gas separator (5) completes a loop. In the other liquid path, the refrigerant flows sequentially through the pneumatic ball valve UNS28, condenser (6), liquid storage tank (9), evaporator (10) until the gas separator (5) completes a loop.

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