R744 supercritical and subcritical heat exchanger testing device

Abstract

The invention discloses a testing device meeting R744 supercritical and subcritical heat exchangers, and relates to the technical field of air conditioner heat exchanger testing. The system comprises a first-stage compressor and a second-stage compressor, wherein the first-stage compressor and the second-stage compressor are arranged between a gas component and an oil component in parallel through a refrigerant pipeline; the first-stage compressor and the second-stage compressor are further connected through a refrigerant pipeline and a first air cooler, and the oil separator is connected with the first-stage compressor and the second-stage compressor through two oil return pipelines. The refrigerant outlet end of the oil component is connected with an upper inlet of the condenser and an upper inlet of the second air cooler through a tee joint, a lower outlet of the condenser is connected with the liquid storage tank, the liquid storage tank is connected with the evaporator through a refrigerant pipeline, and the liquid outlet end of the evaporator is connected with the air component. By arranging the adjusting valve, the opening response is fast, and the mode is faster and more direct compared with an original mode of adjusting the temperature or flow of a water path of the condenser.

Description

Technical Field

[0001] The invention belongs to the technical field of air-conditioning heat exchanger testing, and in particular relates to a testing device that meets the requirements of R744 supercritical and subcritical heat exchangers. Background Art

[0002] With the development of the global environmentally friendly refrigerant replacement process, the natural refrigerant R744 (carbon dioxide) has begun to be widely used in large supermarkets, cold storage and new energy vehicles. However, since its operating pressure is 5-10 times higher than that of conventional refrigerants, the operating pressure range can reach 5~15MPa, and the exhaust temperature can reach 130℃, all components in the refrigeration system need to be newly developed. As one of the important components of the refrigeration system, the heat exchanger's heat exchange performance, flow resistance state, and diversion conditions have a great impact on the overall system energy efficiency. Therefore, it is also urgently needed to test it with comprehensive functions and high stability test equipment.

[0003] At present, there are few application scenarios using carbon dioxide as a refrigerant, so the corresponding test equipment is mainly built based on the actual use system, such as Figure 1 The following is the schematic diagram of the test system for the performance test of heat exchangers with carbon dioxide as the refrigerant. First, the flow control of the tested part is adjusted in real time by the frequency conversion of the compressor. Due to the limited frequency conversion range of the compressor and the large adjustment range, the flow control range is small and the stability is poor. If the return oil is not handled properly, the compressor is also easily damaged. Second, the high pressure is controlled by the water volume or water temperature on the air cooler side: However, since the critical temperature of R744 is about 31°C, the refrigerant state is supercritical after exceeding this temperature. At this time, the temperature and saturation pressure cannot correspond, which will cause poor control stability. At the same time, due to the strong thermal inertia of the water circuit, the control speed will be slow. Third, the compressor is operated alone: ​​using one compressor, due to the limited operating range of a single compressor, the overall test system control operating range will be small, and some high pressure ratio conditions cannot be controlled. Fourth, the evaporator-condenser switch requires the expansion valve flow direction and position to be turned: Since the sample flow direction will be different when testing the evaporator and condenser, when this method is used, it will be necessary to turn the expansion valve flow and position when testing different sample types, resulting in low test efficiency and the inability to automatically switch between defrosting conditions. Fifth, the condenser inlet temperature control depends on the compressor exhaust temperature control: When testing the inlet high temperature condition, the inlet temperature depends on the compressor exhaust temperature control, and the exhaust temperature depends on the compressor suction superheat, resulting in stability deviation and narrow control range.

[0004] The existing R744 supercritical and subcritical heat exchanger test device has poor stability and a narrow control range when testing the heat exchanger. The high pressure required for the test is only provided by the condenser, which makes the test speed slow. At the same time, the single operation of the compressor leads to a small operating condition control range and cannot test the high pressure ratio condition. When switching the test evaporator or condenser, the expansion valve needs to be turned, resulting in the inability to achieve automatic switching of the tested component and the low test efficiency. Therefore, the present invention proposes a R744 supercritical and subcritical heat exchanger test device. Summary of the invention

[0005] The purpose of the present invention is to provide a test device that meets the requirements of R744 supercritical and subcritical heat exchangers, so as to solve the problems that the existing test devices have poor stability and narrow control range when testing the heat exchanger, and the high pressure required for the test is only provided by the condenser, which makes the test speed slow. At the same time, the single operation of the compressor leads to a small operating condition control range and the inability to test the high pressure ratio condition. When switching the test evaporator or condenser, the expansion valve needs to be turned, resulting in the inability to achieve automatic switching of the tested component and the relatively low test efficiency.

[0006] In order to solve the above technical problems, the present invention is achieved through the following technical solutions: The present invention is a test device for supercritical and subcritical heat exchangers meeting R744, comprising a primary compressor and a secondary compressor, wherein the primary compressor and the secondary compressor are arranged in parallel between a gas separator and an oil separator through a refrigerant pipeline; the primary compressor and the secondary compressor are also connected through a first air cooler by using a refrigerant pipeline, and the oil separator is respectively connected to the primary compressor and the secondary compressor through two return oil pipelines; the refrigerant outlet end of the oil separator is respectively connected to an upper inlet of a condenser and an upper inlet of a second air cooler through a tee, the lower outlet of the condenser is connected to a liquid storage tank, the liquid storage tank is connected to an evaporator through a refrigerant pipeline, and the liquid outlet end of the evaporator is connected to the gas separator; the lower outlet of the second air cooler is connected to an upper inlet of an oil heater, the lower outlet of the oil heater is connected to a gas separator position through a tee through a refrigerant pipeline at one end, and is connected to a tested component at the other end, and one end of the tested component is connected to the gas separator.

[0007] Preferably, the gas separator outlet end is respectively provided with a pressure measurement and control point PSE1 and a temperature measurement and control point TIS1; the first-stage compressor inlet end is respectively provided with a temperature measurement and control point TWS1 and a pneumatic ball valve UNS1; and the first-stage compressor outlet end is provided with a pneumatic ball valve UNS2 and a temperature measurement and control point TWS2; the second-stage compressor inlet end is respectively provided with a temperature measurement and control point TWS3 and a pneumatic ball valve UNS4; and the second-stage compressor outlet end is provided with a pneumatic ball valve UNS5 and a temperature measurement and control point TWS4; the first air cooler lower inlet position is provided with a pneumatic ball valve UNS25, and the first air cooler upper outlet position is provided with a pneumatic ball valve UNS26.

[0008] 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 liquid storage tank is connected to the inlet position of the second air cooler through a refrigerant pipeline, and a pneumatic ball valve UNS29 is installed on the refrigerant pipeline; a pneumatic ball valve UNS13 is arranged near the inlet end of the second air cooler, a pneumatic ball valve UNS14 is arranged on the refrigerant pipeline connected to the gas separator at the lower outlet of the oil heater, and a pneumatic ball valve UNS14 is arranged on the refrigerant pipeline connected to one end of the test piece at the lower outlet of the oil heater. There are pneumatic ball valve UNS18, connecting system hose LHS1, pneumatic ball valve UNS19, pressure measurement and control point PSE5, temperature measurement and control point TIS5, regulating valve UNW1, pneumatic ball valve UNS20, connecting system hose LHS2, pressure measurement and control point PSE6 and temperature measurement and control point TIS6; a pneumatic ball valve UNS15 is connected in parallel between the liquid inlet end of the temperature measurement and control point TIS5 and the liquid outlet end of the pneumatic ball valve UNS20; a pneumatic ball valve UNS16 is connected in parallel between the liquid inlet end of the pneumatic ball valve UNS19 and the liquid outlet end of the regulating valve UNW1.

[0009] Preferably, the refrigerant pipeline connected to the gas separator at the other end of the measured object is connected in sequence with a temperature measurement and control point TIS7, a pressure measurement and control point PSE7, a connecting system hose LHS3 and a pneumatic ball valve UNS21; wherein, the pressure measurement and control point PSE7 and the pressure measurement and control point PSE6 are connected through a differential pressure measurement and control point.

[0010] Preferably, a refrigerant pipe extends outward from the refrigerant pipe between the pneumatic ball valve UNS18 and the connecting system hose LHS1 and is connected to the liquid inlet end of the evaporator, and a pneumatic ball valve UNS17 is provided on the refrigerant pipe; a regulating valve UNW3 is provided between the liquid storage tank and the evaporator.

[0011] Preferably, when the evaporator is tested under the supercritical state of R744, the primary compressor and the secondary compressor are kept in parallel, and the pneumatic ball valve UNS29, pneumatic ball valve UNS14, pneumatic ball valve UNS17, pneumatic ball valve UNS1 and pneumatic ball valve UNS15 are closed at the same time. After the refrigerant passes through the primary compressor and the secondary compressor in parallel, the oil separator is used to separate the compressor oil in the refrigerant discharged from the two compressors. The refrigerant is divided into two liquid paths after the oil separator, one of which is a liquid path refrigerant that flows through the second air cooler, the oil heater, the pressure measurement and control point PSE5, the temperature measurement and control point TIS5, the evaporator of the tested device, the temperature measurement and control point TIS7, and the pressure measurement and control point PSE7 in sequence until the gas separation completes a circuit, and the other liquid path refrigerant flows through the regulating valve UNW5, the condenser, and the evaporator in sequence until the gas separation completes a circuit.

[0012] Preferably, when the condenser is tested under the supercritical state of R744, the first-stage compressor and the second-stage compressor are kept in parallel, and the pneumatic ball valve UNS21, pneumatic ball valve UNS19 and pneumatic ball valve UNS20 are closed at the same time; the refrigerant is divided into two liquid circuits after oil separation, in which the refrigerant in one liquid circuit flows through the second air cooler, oil heater, pneumatic ball valve UNS14, pressure measurement and control point PSE7, temperature measurement and control point TIS7, condenser of the tested part, pneumatic ball valve UNS15, pneumatic ball valve UNS16, evaporator in sequence until the gas separation completes a circuit; the refrigerant in the other liquid circuit flows through the regulating valve UNW5, condenser, liquid storage tank, evaporator in sequence until the gas separation completes a circuit; wherein the liquid outlet end of the liquid storage tank is connected to the liquid inlet end of the second air cooler by a refrigerant pipeline.

[0013] Preferably, when the evaporator is tested under the subcritical state of R744, the first-stage compressor and the second-stage 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 at the same time. The refrigerant is discharged from the compressor and passes through the oil separator, pneumatic ball valve UNS28, condenser and liquid storage tank in sequence and is divided into two liquid circuits. The refrigerant in one liquid circuit flows through the pneumatic ball valve UNS29, the second air cooler, the oil heater, the pneumatic ball valve UNS18, the pneumatic ball valve UNS19, the pneumatic ball valve UNS20, the evaporator of the tested part and the pneumatic ball valve UNS21 in sequence until the gas separator completes a circuit, and the refrigerant in the other liquid circuit flows through the evaporator in sequence until the gas separator completes a circuit.

[0014] Preferably, when the condenser is tested under the subcritical state of R744, the first-stage compressor and the second-stage compressor are kept in parallel, and the regulating valve UNW5, pneumatic ball valve UNS9, pneumatic ball valve UNS18, pneumatic ball valve UNS19, pneumatic ball valve UNS20 and pneumatic ball valve UNS21 are closed at the same time. The refrigerant is discharged from the compressor and is divided into two liquid circuits after passing through the oil separator. The refrigerant in one liquid circuit flows through the second air cooler, the oil heater, the pneumatic ball valve UNS14, the condenser of the tested part, the pneumatic ball valve UNS15, the pneumatic ball valve UNS16, the pneumatic ball valve UNS17, and the evaporator in sequence until the gas separator completes a circuit; the refrigerant in the other liquid circuit flows through the pneumatic ball valve UNS28, the condenser, the liquid storage tank, and the evaporator in sequence until the gas separator completes a circuit.

[0015] Preferably, the parameters to be controlled for the evaporator test sample of the tested part include: valve front pressure PSE5: controlled by the condenser during subcritical testing and controlled by the regulating valve UNW5 during supercritical testing; valve front temperature TIS5: controlled by the second air cooler and the oil heater; evaporator outlet pressure PSE7: controlled by the auxiliary regulating valve UNW3; evaporator outlet temperature TIS7: controlled by the main regulating valve UNW1; The parameters to be controlled for the condenser test sample of the tested device 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. The evaporator and condenser of the present invention are the test mechanisms in the test device, and the evaporator and condenser of the tested device are the tested devices.

[0016] The present invention has the following beneficial effects: The present invention tests the evaporator under test by controlling four parameters, namely, the pre-valve temperature, the pre-valve pressure, the evaporator outlet temperature and the evaporator outlet pressure on the refrigerant side of the evaporator. 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 capacity on the refrigerant side of the evaporator under test is obtained by multiplying the inlet and outlet enthalpy values ​​by the flow rate.

[0017] The present invention tests the condenser of the tested device, controls three parameters of the condenser inlet temperature, condenser inlet pressure, and condenser outlet temperature on the refrigerant side of the condenser, and the four parameters plus the measured condenser outlet pressure correspond to the inlet and outlet enthalpy values ​​of the condenser of the tested device respectively. When the operating conditions are stable, the heat exchange capacity on the refrigerant side of the condenser of the tested device is obtained by multiplying the inlet and outlet enthalpy values ​​by the flow rate.

[0018] The present invention controls the refrigerant flow of the test path by assisting the first-stage compressor and the second-stage compressor in frequency conversion and the auxiliary path flow regulating valve UNW3 to shunt the refrigerant flow. The first-stage compressor and the second-stage compressor select high, medium and low frequency operation to fix the approximate total refrigerant flow of the system, and then shunts the refrigerant flow through the auxiliary path regulating valve UNW3 to achieve precise control of the refrigerant flow of the test path.

[0019] The present invention controls the compressor exhaust section pressure by adjusting the opening of the valve UNW5, thereby controlling the valve front pressure PSE5 during the evaporator test and the inlet pressure PSE7 during the condenser test. Since the regulating valve opening responds quickly, it is faster and more direct than the original method of adjusting the condenser water path temperature or flow. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for describing the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying creative work.

[0021] Figure 1 This is the test schematic diagram of the original supercritical heat exchanger; Figure 2 The general diagram of the R744 supercritical and subcritical heat exchanger testing device provided by the present invention; Figure 3 A diagram of the parallel operation of compressors provided by the present invention; Figure 4 A diagram of the series operation of compressors provided by the present invention; Figure 5 A test operation diagram of a subcritical evaporator provided by the present invention; Figure 6 A test operation diagram of a subcritical condenser provided by the present invention; Figure 7 A test operation diagram of a supercritical evaporator provided by the present invention; Figure 8 This is a test operation diagram of the supercritical condenser provided by the present invention.

[0022] In the accompanying drawings, the components represented by the reference numerals are listed as follows: 1. First-stage compressor; 2. Second-stage compressor; 3. First air cooler; 4. Oil separator; 5. Gas separator; 6. Condenser; 7. Second air cooler; 8. Oil heater; 9. Evaporator; 10. Liquid storage tank. DETAILED DESCRIPTION

[0023] In order to make the technical means, creative features, objectives and effects achieved by the present invention easy to understand, the present invention is further explained below in conjunction with specific implementation methods.

[0024] See also Figure 1-3 The present invention is a test device for R744 supercritical and subcritical heat exchangers, comprising a primary compressor 1 and a secondary compressor 2, which are arranged in parallel between a gas separator 5 and an oil separator 4 through a refrigerant pipeline; the primary compressor 1 and the secondary compressor 2 are also connected through a first air cooler 3 by a refrigerant pipeline, and the oil separator 4 is respectively connected to the primary compressor 1 and the secondary compressor 2 through two return oil pipelines; the refrigerant outlet end of the oil separator 4 is respectively connected to the upper inlet of the condenser 6 and the upper inlet of the second air cooler 7 through a tee, the lower outlet of the condenser 6 is connected to a liquid storage tank 10, the liquid storage tank 10 is connected to an evaporator 9 through a refrigerant pipeline, and the liquid outlet end of the evaporator 9 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, and the lower outlet of the oil heater 8 is connected to the gas separator 5 through a tee, one end of which is connected to the position of the gas separator 5 through a refrigerant pipeline, and the other end is connected to the tested piece. The first auxiliary compressor and the second auxiliary compressor are used to provide the refrigerant flow of the test system and establish the system operating pressure difference; the first air cooler is used to control the suction temperature of the secondary compressor when the compressors are connected in series; the oil separator is used to separate the compressor oil in the refrigerant discharged from the auxiliary compressor and return it to the compressor again through the pipeline; the gas separator ensures that the compressor suction is free of liquid; all the starting ball valves are used to switch the system refrigerant flow path; the regulating valve is used to adjust the refrigerant flow of the corresponding flow path and control the temperature and pressure measurement points in the system; the condenser controls the intermediate pressure of the system under the supercritical state and the high pressure of the system under 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 storage tank is used to store the refrigerant in the buffer system; the connecting system hose is used to connect the moving parts and the test samples.

[0025] Among them, the outlet end of the gas separator 5 is respectively provided with a pressure measurement and control point PSE1 and a temperature measurement and control point TIS1; the air inlet end of the first-stage compressor 1 is respectively provided with a temperature measurement and control point TWS1 and a pneumatic ball valve UNS1; and the air outlet end of the first-stage compressor 1 is provided with a pneumatic ball valve UNS2 and a temperature measurement and control point TWS2; the air inlet end of the second-stage compressor 2 is respectively provided with a temperature measurement and control point TWS3 and a pneumatic ball valve UNS4; and the air outlet end of the second-stage compressor 2 is provided with a pneumatic ball valve UNS5 and a temperature measurement and control point TWS4; the lower inlet position of the first air cooler 3 is provided with a pneumatic ball valve UNS25, and the upper outlet position of the first air cooler 3 is provided with a pneumatic ball valve UNS26.

[0026] Among them, 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; the liquid outlet of the liquid storage tank 10 is connected to the inlet position of the second air cooler 7 through a refrigerant pipeline, and a pneumatic ball valve UNS29 is installed on the refrigerant pipeline; a pneumatic ball valve UNS13 is set near the inlet end of the second air cooler 7, a pneumatic ball valve UNS14 is set on the refrigerant pipeline connected to the gas separator 5 at the lower outlet of the oil heater 8, and pneumatic ball valves UNS14 are set on the refrigerant pipeline connected to one end of the test piece at the lower outlet of the oil heater 8. Pneumatic ball valve UNS18, connecting system hose LHS1, pneumatic ball valve UNS19, pressure measuring and control point PSE5, temperature measuring and control point TIS5, regulating valve UNW1, pneumatic ball valve UNS20, connecting system hose LHS2, pressure measuring and control point PSE6 and temperature measuring and control point TIS6; a pneumatic ball valve UNS15 is connected in parallel between the liquid inlet end of the temperature measuring and control point TIS5 and the liquid outlet end of the pneumatic ball valve UNS20; a pneumatic ball valve UNS16 is connected in parallel between the liquid inlet end of the pneumatic ball valve UNS19 and the liquid outlet end of the regulating valve UNW1.

[0027] Among them, the refrigerant pipeline connected to the gas separator 5 at the other end of the tested piece is connected with the temperature measurement and control point TIS7, the pressure measurement and control point PSE7, the connecting system hose LHS3 and the pneumatic ball valve UNS21 in sequence; among them, the pressure measurement and control point PSE7 and the pressure measurement and control point PSE6 are connected through the pressure difference measurement and control point.

[0028] Among them, a refrigerant pipe extends outward from the refrigerant pipe between the pneumatic ball valve UNS18 and the connecting system hose LHS1 and is connected to the liquid inlet end of the evaporator 9, and a pneumatic ball valve UNS17 is provided on the refrigerant pipe; a regulating valve UNW3 is provided between the liquid storage tank 10 and the evaporator 9.

[0029] Among them, the parameters that need to be controlled for the evaporator test sample of the tested device include: valve front pressure PSE5: controlled by condenser 6 during subcritical test, and controlled by regulating valve UNW5 during supercritical test; valve front 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; The parameters that need to be controlled for the condenser test sample of the tested device include: condenser inlet pressure PSE7: controlled by condenser 6 during subcritical testing and controlled by regulating valve UNW5 during supercritical testing; condenser inlet temperature TIS7: controlled by the second air cooler 7 and the oil heater 8; condenser outlet temperature TIS6: controlled by the main regulating valve UNW1.

[0030] Among them, since a single compressor has its own operating range limitations, and when operating under supercritical conditions, under some heat pump conditions, the operating pressure ratio required for the test of the tested part will exceed the operating range of the compressor. In order to avoid excessively high exhaust temperature of the compressor and reliable operation of the compressor, two auxiliary compressors are connected in series to operate. At this time, auxiliary compressor MCM1 is a first-stage compressor (low-pressure stage), and auxiliary compressor MCM2 (high-pressure stage). The exhaust of 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.

[0031] Example 1: See Figure 7 When the evaporator is tested under the supercritical state of R744, the first-stage compressor 1 and the second-stage compressor 2 are kept in parallel, and the pneumatic ball valve UNS29, pneumatic ball valve UNS14, pneumatic ball valve UNS17, pneumatic ball valve UNS1 and pneumatic ball valve UNS15 are closed at the same time. 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. The refrigerant is divided into two liquid paths after passing through the oil separator 4. The refrigerant in one liquid path flows through the second air cooler 7, the oil heater 8, the pressure measurement and control point PSE5, the temperature measurement and control point TIS5, the evaporator of the tested device, the temperature measurement and control point TIS7, the pressure measurement and control point PSE7 in turn until the gas separator 5 completes a circuit. The refrigerant in the other liquid path flows through the regulating valve UNW5, the condenser 6, the evaporator 9 in turn until the gas separator 5 completes a circuit.

[0032] Example 2: See Figure 8 When the condenser is tested under the supercritical state of R744, the first-stage compressor 1 and the second-stage compressor 2 are kept in parallel, and the pneumatic ball valve UNS21, the pneumatic ball valve UNS19 and the pneumatic ball valve UNS20 are closed at the same time; the refrigerant is divided into two liquid circuits after the oil separator 4, in which the refrigerant in one liquid circuit flows through the second air cooler 7, the oil heater 8, the pneumatic ball valve UNS14, the pressure measurement and control point PSE7, the temperature measurement and control point TIS7, the condenser of the tested device, the pneumatic ball valve UNS15, the pneumatic ball valve UNS16, the evaporator 9 until the air separator 5 completes a circuit; the refrigerant in the other liquid circuit flows through the regulating valve UNW5, the condenser 6, the liquid storage tank 10, the evaporator 9 until the gas separator 5 completes a circuit; the liquid outlet of the liquid storage tank 10 is connected to the liquid inlet of the second air cooler 7 through a refrigerant pipeline.

[0033] Example 3: See Figure 5When testing the evaporator under the subcritical state 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 at the same time. The refrigerant is discharged from the compressor and passes through the oil separator 4, pneumatic ball valve UNS28, condenser 6, and liquid storage tank 10 in turn, and is divided into two liquid circuits. The refrigerant in one liquid circuit 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 tested device, and the pneumatic ball valve UNS21 until the gas separator 5 completes a circuit. The refrigerant in the other liquid circuit flows through the evaporator 9 in turn until the gas separator 5 completes a circuit.

[0034] Example 4: See Figure 6 When testing the condenser under the subcritical state 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 UNS9, pneumatic ball valve UNS18, pneumatic ball valve UNS19, pneumatic ball valve UNS20 and pneumatic ball valve UNS21 are closed at the same time. The refrigerant is discharged from the compressor and passes through the oil separator 4 and is divided into two liquid circuits. The refrigerant in one liquid circuit flows through the second air cooler 7, the oil heater 8, the pneumatic ball valve UNS14, the condenser of the tested device, the pneumatic ball valve UNS15, the pneumatic ball valve UNS16, the pneumatic ball valve UNS17, the evaporator 9 until the gas separator 5 completes a circuit; the refrigerant in the other liquid circuit flows through the pneumatic ball valve UNS28, the condenser 6, the liquid storage tank 10, the evaporator 9 until the gas separator 5 completes a circuit.

[0035] When the refrigerant system is running for different test types, the ball valves UNS15, UNS16, UNS19 and UNS20 are switched on and off accordingly according to the evaporation test and condensation test of the tested device. When the evaporator of the tested device is tested, UNS15 and UNS16 are closed, and UNS19 and UNS20 are opened. When the condenser of the tested device is tested, UNS15 and UNS16 are opened, and UNS19 and UNS20 are closed. This can ensure that the flow direction of the expansion valve remains unchanged and realize automatic switching of the condenser and evaporator operating conditions.

[0036] The condenser inlet temperature is controlled by the second air cooler and the oil heater.

[0037] The above shows and describes the basic principles and main features of the present invention and the advantages of the present invention. It should be understood by those skilled in the art that the present invention is not limited to the above embodiments. The above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, which fall within the scope of the present invention to be protected. The scope of protection of the present invention is defined by the attached claims and their equivalents.

Claims

1. A test device that meets the requirements of R744 supercritical and subcritical heat exchangers, characterized in that: The invention comprises a primary compressor (1) and a secondary compressor (2), wherein the primary compressor (1) and the secondary compressor (2) are arranged in parallel between an air separator (5) and an oil separator (4) via a refrigerant pipeline; the primary compressor (1) and the secondary compressor (2) are also connected via a refrigerant pipeline through a first air cooler (3); the oil separator (4) is respectively connected to the primary compressor (1) and the secondary compressor (2) via two oil return pipelines; the refrigerant outlet end of the oil separator (4) is respectively connected to a condenser (5) via a tee. The upper inlet of the condenser (6) is connected to the upper inlet of the second air cooler (7); the lower outlet of the condenser (6) is connected to the liquid storage tank (10); the liquid storage tank (10) is connected to the evaporator (9) through a refrigerant pipeline; the liquid outlet of the evaporator (9) 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 of which is connected to the gas separator (5) through a refrigerant pipeline, and the other end is connected to the device under test; one end of the device under test is connected to the gas separator (5).

2. The R744 supercritical and subcritical heat exchanger testing device according to claim 1 is characterized in that: The outlet of the gas separator (5) is provided with a pressure measurement and control point PSE1 and a temperature measurement and control point TIS1; The air inlet end of the first-stage compressor (1) is provided with a temperature measurement and control point TWS1 and a pneumatic ball valve UNS1; and the air outlet end of the first-stage compressor (1) is provided with a pneumatic ball valve UNS2 and a temperature measurement and control point TWS2; the air inlet end of the second-stage compressor (2) is provided with a temperature measurement and control point TWS3 and a pneumatic ball valve UNS4; and the air outlet end of the second-stage compressor (2) is provided with a pneumatic ball valve UNS5 and a temperature measurement and control point TWS4; the lower inlet position of the first air cooler (3) is provided with a pneumatic ball valve UNS25, and the upper outlet position of the first air cooler (3) is provided with a pneumatic ball valve UNS26.

3. The R744 supercritical and subcritical heat exchanger testing device according to claim 2 is characterized in that: The liquid inlet of the condenser (6) is provided with a regulating valve UNW5, and a pneumatic ball valve UNS28 is connected in parallel to the regulating valve UNW5; the liquid outlet of the liquid storage tank (10) is connected to the inlet position of the second air cooler (7) through a refrigerant pipeline, and a pneumatic ball valve UNS29 is installed on the refrigerant pipeline; a pneumatic ball valve UNS13 is provided near the inlet end of the second air cooler (7), a pneumatic ball valve UNS14 is provided on the refrigerant pipeline connected to the gas separator (5) at the lower outlet of the oil heater (8), and the lower outlet of the oil heater (8) is connected to the outlet of the test piece at one end. The refrigerant pipeline is sequentially provided with a pneumatic ball valve UNS18, a connecting system hose LHS1, a pneumatic ball valve UNS19, a pressure measuring and control point PSE5, a temperature measuring and control point TIS5, a regulating valve UNW1, a pneumatic ball valve UNS20, a connecting system hose LHS2, a pressure measuring and control point PSE6 and a temperature measuring and control point TIS6; a pneumatic ball valve UNS15 is connected in parallel between the liquid inlet end of the temperature measuring and control point TIS5 and the liquid outlet end of the pneumatic ball valve UNS20; a pneumatic ball valve UNS16 is connected in parallel between the liquid inlet end of the pneumatic ball valve UNS19 and the liquid outlet end of the regulating valve UNW1.

4. The R744 supercritical and subcritical heat exchanger testing device according to claim 3 is characterized in that: The other end of the measured object is connected to the refrigerant pipeline of the gas separator (5), which is connected in sequence with a temperature measurement and control point TIS7, a pressure measurement and control point PSE7, a connecting system hose LHS3 and a pneumatic ball valve UNS21; wherein the pressure measurement and control point PSE7 and the pressure measurement and control point PSE6 are connected via a pressure difference measurement and control point.

5. The R744 supercritical and subcritical heat exchanger testing device according to claim 4, characterized in that: A refrigerant pipe extends outward from the refrigerant pipe between the pneumatic ball valve UNS18 and the connecting system hose LHS1 and is connected to the liquid inlet end of the evaporator (9), and a pneumatic ball valve UNS17 is provided on the refrigerant pipe; a regulating valve UNW3 is provided between the liquid storage tank (10) and the evaporator (9).

6. The R744 supercritical and subcritical heat exchanger testing device according to claim 5, characterized in that: When the evaporator is tested under the supercritical state of R744, the first-stage compressor (1) and the second-stage compressor (2) are kept in parallel, and the pneumatic ball valve UNS29, the pneumatic ball valve UNS14, the pneumatic ball valve UNS17, the pneumatic ball valve UNS1 and the pneumatic ball valve 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 the refrigerant passes through the oil separator (4), it is divided into two liquid paths. The refrigerant in one liquid path flows through the second air cooler (7), the oil heater (8), the pressure measurement and control point PSE5, the temperature measurement and control point TIS5, the evaporator of the device under test, the temperature measurement and control point TIS7, the pressure measurement and control point PSE7 in sequence until the gas separator (5) completes a loop. The refrigerant in the other liquid path flows through the regulating valve UNW5, the condenser (6), the evaporator (9) in sequence until the gas separator (5) completes a loop.

7. The R744 supercritical and subcritical heat exchanger testing device according to claim 6, characterized in that: When the condenser is tested under the supercritical state of R744, the first-stage compressor (1) and the second-stage compressor (2) are kept in parallel, and the pneumatic ball valve UNS21, the pneumatic ball valve UNS19 and the pneumatic ball valve UNS20 are closed at the same time; the refrigerant is divided into two liquid paths after passing through the oil separator (4), wherein the refrigerant in one liquid path flows in sequence through the second air cooler (7), the oil heater (8), the pneumatic ball valve UNS14, the pressure measurement and control point PSE7, the temperature measurement and control point TIS7, the condenser of the tested device, the pneumatic ball valve UNS15, the pneumatic ball valve UNS16, the evaporator (9) until the air separator (5) completes a circuit; and the refrigerant in the other liquid path flows in sequence through the regulating valve UNW5, the condenser (6), the liquid storage tank (10), the evaporator (9) until the air separator (5) completes a circuit; wherein the liquid outlet of the liquid storage tank (10) and the liquid inlet of the second air cooler (7) are connected via a refrigerant pipeline.

8. The R744 supercritical and subcritical heat exchanger testing device according to claim 7, characterized in that: When the evaporator is tested under the subcritical state of R744, the first-stage compressor (1) and the second-stage compressor (2) are kept in parallel, and the regulating valve UNW5, the pneumatic ball valve UNS13, the pneumatic ball valve UNS14, the pneumatic ball valve UNS15, the pneumatic ball valve UNS16 and the pneumatic ball valve UNS17 are closed at the same time. The refrigerant discharged from the compressor passes through the oil separator (4), the pneumatic ball valve UNS28, the condenser (6) and the liquid storage tank (10) in sequence and is divided into two liquid paths. The refrigerant in one of the liquid paths flows in sequence 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 tested device and the pneumatic ball valve UNS21 until the gas separator (5) completes a circuit. The refrigerant in the other liquid path flows in sequence through the evaporator (9) until the gas separator (5) completes a circuit.

9. The R744 supercritical and subcritical heat exchanger testing device according to claim 8, characterized in that: When the condenser is tested under the subcritical state of R744, the first-stage compressor (1) and the second-stage compressor (2) are kept in parallel, and the regulating valve UNW5, the pneumatic ball valve UNS9, the pneumatic ball valve UNS18, the pneumatic ball valve UNS19, the pneumatic ball valve UNS20 and the pneumatic ball valve UNS21 are closed at the same time. The refrigerant is discharged from the compressor and passes through the oil separator (4) and is divided into two liquid paths. The refrigerant in one liquid path flows in sequence through the second air cooler (7), the oil heater (8), the pneumatic ball valve UNS14, the condenser of the tested device, the pneumatic ball valve UNS15, the pneumatic ball valve UNS16, the pneumatic ball valve UNS17, the evaporator (9) until the air separator (5) completes a circuit; the refrigerant in the other liquid path flows in sequence through the pneumatic ball valve UNS28, the condenser (6), the liquid storage tank (10), the evaporator (9) until the air separator (5) completes a circuit.

10. The R744 supercritical and subcritical heat exchanger testing device according to claim 9, characterized in that: The parameters to be controlled for the evaporator test sample of the test piece include: the valve front pressure PSE5: controlled by the condenser (6) during subcritical testing, and controlled by the regulating valve UNW5 during supercritical testing; the valve front temperature TIS5: controlled by the second air cooler (7) and the oil heater (8); the evaporator outlet pressure PSE7: controlled by the auxiliary regulating valve UNW3; the evaporator outlet temperature TIS7: controlled by the main regulating valve UNW1; The parameters to be controlled for the condenser test sample of the test piece include: condenser inlet pressure PSE7: controlled by the condenser (6) during subcritical testing and controlled by the regulating valve UNW5 during supercritical testing; condenser inlet temperature TIS7: controlled by the second air cooler (7) and the oil heater (8); condenser outlet temperature TIS6: controlled by the main regulating valve UNW1.

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