Condensation test unit for transcritical homogeneous carbon dioxide test equipment

Abstract

The utility model provides a condensation test unit for transcritical homogeneous carbon dioxide test equipment, which solves the test measurement problem of transcritical carbon dioxide condensation phenomenon, inhibits carbon dioxide condensation and further improves the refrigeration efficiency of a compressor. The characteristic parameters of the transcritical carbon dioxide condensation phenomenon are directly collected, the technical problem that difference exists between the flow working condition of supercritical carbon dioxide simulated by a similar modeling method and the actual operation working condition is solved, and corresponding temperature, pressure, flow and other sensors are arranged in the compressor; the characteristic parameters of the transcritical carbon dioxide condensation phenomenon are collected to serve as the reaction threshold value of each sensor element in the compressor, the refrigeration efficiency of the compressor can be effectively improved by adjusting the temperature, pressure, flow and the like in the compressor and avoiding the condensation phenomenon, and the equipment practicability is high.

Description

Technical Field

[0001] The utility model relates to the technical field of carbon dioxide refrigeration, in particular to a condensation test unit used for transcritical homogeneous carbon dioxide test equipment. Background Art

[0002] Transcritical CO2 refrigeration cycle is widely used in automotive air conditioning, with advantages such as high compression operation efficiency, large volumetric refrigeration capacity and small system size. In the transcritical refrigeration cycle, CO2 gas undergoes a change from a subcritical state to a supercritical state, and the properties of the fluid will also change accordingly.

[0003] When carbon dioxide vapor flows under high pressure in a compressor, carbon dioxide will condense. The condensed carbon dioxide droplets will damage the blades of the compressor, thereby affecting the operating efficiency of the entire compressor. The existing technology cannot directly measure the condensation of carbon dioxide in the compressor.

[0004] For example, a similarity modeling method for supercritical carbon dioxide compressor testing disclosed in a Chinese invention patent with an application publication date of 2020.04.24 and an application publication number of CN 111062124 A, first, according to the geometric similarity criterion, the geometric parameters of the test model are obtained by year-on-year scaling. Then, based on the flow similarity criterion between different working fluids, the main criterion numbers are guaranteed to be consistent, and the operating parameters such as the speed, inlet pressure, inlet temperature, and flow rate of the air working fluid compressor are obtained, and experimental research is carried out to obtain experimental data. Secondly, the performance parameters such as the pressure ratio, isentropic efficiency, stress load, and leakage flow of the supercritical carbon dioxide compressor are derived according to the performance conversion criterion. Finally, the operating conditions are changed to evaluate the comprehensive performance of the supercritical carbon dioxide compressor under different operating conditions, and the variable operating condition performance of the supercritical carbon dioxide compressor is verified. The above technical scheme simulates and evaluates the comprehensive performance of the compressor through geometric structure modeling, fluidity modeling, and compressor performance conversion, improves the compressor blades, and thus improves the refrigeration efficiency. The similarity modeling method is used to reduce the scale, replace carbon dioxide with air, simulate the flow conditions of supercritical carbon dioxide, and simulate the structural parameters of the blades. However, there are differences between the actual operating conditions and the characteristics of the condensation phenomenon of carbon dioxide cannot be directly collected and analyzed, and the refrigeration efficiency of the compressor cannot be effectively improved. Utility Model Content

[0005] Aiming at the technical problem that there is a difference between the flow condition of supercritical carbon dioxide simulated by a similar modeling method and the actual operating condition, the utility model proposes a condensation test unit for a transcritical homogeneous carbon dioxide test equipment.

[0006] In order to solve the above technical problems, the technical solution of the utility model is:

[0007] A condensation test unit for a transcritical homogeneous carbon dioxide test device includes a carbon dioxide condensation test unit, wherein the carbon dioxide condensation test unit includes a high-pressure gas storage tank, a mass flow meter, a light-transmissive nozzle and a passive recovery tank connected in sequence, and the nozzle is connected to a temperature measurement module, a pressure measurement module and an optical measurement module.

[0008] This technical solution stores high-pressure carbon dioxide in a high-pressure gas storage tank, and then under the action of pressure difference, carbon dioxide flows from the high-pressure part to the passive recovery tank. During the flow of carbon dioxide, non-equilibrium condensation occurs in the nozzle. The mass flowmeter reacts to the flow rate of the carbon dioxide fluid, the pressure measurement module monitors the discrete point pressure of the fluid in the nozzle, and the optical measurement module measures the condensed droplets in the nozzle, so as to obtain data such as the location of the condensed droplets, the size of the droplets, and the growth of the droplets. By measuring the pressure, temperature, the location and size of the droplets generated, and the flow rate (flow rate) of the fluid when carbon dioxide undergoes non-equilibrium condensation, the critical conditions for carbon dioxide condensation are obtained. And using the parameters of the obtained critical conditions, the corresponding sensor response threshold is set in the compressor to avoid the condensation of carbon dioxide and reduce the refrigeration cycle efficiency of the compressor.

[0009] Furthermore, the nozzle includes an arc panel that is symmetrical up and down, and the arc panel is connected to a light-transmitting panel on the left and right. The cross-sectional shape of the nozzle along the flow direction of carbon dioxide is rectangular, and the area of ​​the rectangle gradually shrinks and then gradually expands. The light-transmitting panel of the nozzle can facilitate the observation and measurement of the condensation phenomenon of carbon dioxide, and the upper and lower arc panels of the nozzle and the left and right light-transmitting panels together form a sealed tube, leaving only an inlet and an outlet for carbon dioxide to flow therein. The shape of the nozzle first contracts and then expands along the flow direction of carbon dioxide, which facilitates carbon dioxide to reach a transcritical state, and then a non-equilibrium condensation process occurs.

[0010] Furthermore, the temperature measurement module of the nozzle includes an inlet temperature measurement module and an outlet temperature measurement module, wherein the inlet temperature measurement module includes a constant temperature module connected to the high-pressure gas storage tank, and the outlet temperature measurement module includes a temperature pressure sensor connected to the outlet of the passive recovery tank. When non-equilibrium condensation of carbon dioxide occurs in the nozzle, the temperature in the nozzle will change. Measuring the temperature in the nozzle cannot timely reflect the critical conditions for condensation of carbon dioxide. Therefore, the temperature of the nozzle inlet and the nozzle outlet are measured respectively to obtain the critical temperature when carbon dioxide condenses. The reaction threshold of the temperature sensor in the compressor is set to be consistent with the inlet temperature of carbon dioxide condensation measured by the above-mentioned device, so that the temperature sensor in the compressor can react in advance.

[0011] Furthermore, the nozzle includes expansion parts at both ends and a contraction part in the middle, and a plurality of pressure measurement modules are provided, each of which is evenly connected to the contraction part. Carbon dioxide is in different pressure states in the expansion part and the contraction part, respectively, so that carbon dioxide can reach a transcritical state, thereby causing condensation, and each pressure measurement module can measure the critical conditions of the condensation phenomenon.

[0012] Furthermore, the pressure measurement modules are evenly spaced and inserted into the upper and lower symmetrical arc panels, and the depths of each pressure measurement module inserted into the arc panel are different. The pressure measurement modules are respectively connected to the upper and lower arc panels and are staggeredly distributed so as to measure the pressure of each discrete point of the condensation phenomenon. The measurement area of ​​the pressure measurement module should be larger than the area where the condensation phenomenon occurs, that is, the distribution length of the pressure measurement module along the nozzle should be slightly larger than the length of the contraction portion.

[0013] Furthermore, the measuring direction of the optical measurement module is perpendicular to the light-transmitting panel. The laser of the optical measurement module can pass through the light-transmitting panel, and the laser is perpendicular to the light-transmitting panel, which is convenient for measuring and recording the carbon dioxide in the entire nozzle. When condensed droplets of carbon dioxide appear, the light signal reflected by the laser passing through the light-transmitting panel will change because the laser encounters the condensed droplets.

[0014] Further, the optical measurement module includes a laser transmitter, a laser attenuator, a beam expander, and a collimating lens connected in sequence to one side of the nozzle, and the laser emission direction is perpendicular to the flow direction of carbon dioxide in the nozzle; the other side of the nozzle is connected in sequence to a 50% beam splitter, a reflector, and a camera, and the 50% beam splitter and the reflector are arranged in pairs. The laser transmitter, laser attenuator, beam expander, and collimating lens are connected in sequence to the left side of the nozzle, and the 50% beam splitter, reflector, and camera are connected in sequence to the right side of the nozzle. After the laser transmitter emits the laser, the laser power is attenuated by the laser attenuator, and then refracted by the beam expander and collimating lens, and then the laser is vertically irradiated to the light-transmitting panel of the nozzle. After the laser passes through the nozzle, it is irradiated to the 50% beam splitter, and then divided into two beams, and then reflected twice, resulting in position offset and interference phenomenon. The interference pattern is recorded by the camera, and different refractive index data can be obtained by analyzing the pattern, which is converted into density data. The optical measurement module measures the different refractive indices of carbon dioxide in its gas and liquid states. The camera can measure different light interference fringes. When the interference fringes measured by the camera change significantly, it means that carbon dioxide has begun to condense. The pressure, temperature, flow rate, etc. at this time are recorded to derive the characteristics of the condensation phenomenon. The pressure, temperature, flow rate and other parameters at this time are used as the reaction threshold of the corresponding sensor in the compressor to prevent carbon dioxide condensation from affecting the refrigeration efficiency.

[0015] Furthermore, the high-pressure gas storage tank is connected to a constant pressure module for pressure control. The constant pressure module is connected to the outlet of the high-pressure gas storage tank, and controls the pressure of carbon dioxide in the high-pressure gas storage tank by controlling the start and stop of the plunger pump to maintain the state of carbon dioxide at a high pressure. The constant pressure module includes a pressure sensor.

[0016] Furthermore, the outlet of the passive recovery tank is connected to a vacuum pump for equipment pressure relief. The vacuum pump is used to purge the entire test equipment after the test is completed, and collect carbon dioxide for subsequent reuse while avoiding environmental pollution.

[0017] Furthermore, the inlet and outlet connections of the high-pressure gas storage tank are respectively provided with valve switch 2 and valve switch 3, and valve switch 4 is provided between the nozzle and the passive recovery tank. The valve switch can control the flow rate of carbon dioxide as a switch, control the opening and closing of the condensation test unit, and can divide the measuring components of each part during measurement, so that carbon dioxide is in the high pressure or normal pressure state required for the experiment. The high-pressure gas storage tank is provided with a gas storage tank valve, and the pipeline is provided with valve switch 2 for controlling the entry into the gas storage tank and valve switch 3 for controlling the outflow from the gas storage tank. The flow direction of carbon dioxide is controlled by the cooperation of the gas storage tank valve and valve switch 2 and valve switch 3.

[0018] The test equipment of the utility model directly collects the characteristic parameters of the transcritical carbon dioxide condensation phenomenon, thereby avoiding the technical problem that there is a difference between the flow condition of supercritical carbon dioxide simulated by a similar modeling method and the actual operating condition, and sets corresponding temperature and pressure sensors, flow meters and other sensors in the compressor, and collects the characteristic parameters of the transcritical carbon dioxide condensation phenomenon as the reaction threshold of each sensor element in the compressor. By adjusting the temperature, pressure, flow rate and the like in the compressor and avoiding the occurrence of condensation, the refrigeration efficiency of the compressor can be effectively improved, and the equipment is highly practical. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the embodiments of the utility model or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the utility model. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0020] Figure 1 It is a schematic diagram of the structure of the utility model;

[0021] Figure 2 for Figure 1 Schematic diagram of the structure of the optical measurement part;

[0022] Figure 3 for Figure 1 Schematic diagram of the nozzle structure.

[0023] In the figure, 1 carbon dioxide atmospheric pressure gas storage tank, 21 valve switch one, 22 valve switch two, 23 valve switch three, 24 valve switch four, 25 valve switch five, 26 valve switch six, 3 plunger pump, 4 air compressor, 5 high-pressure gas storage tank, 6 constant temperature module, 7 constant pressure module, 8 mass flow meter, 9 nozzle, 901 light-transmitting panel, 10 pressure measurement module, 11 optical measurement module, 1101 laser transmitter, 1102 laser attenuator, 1103 beam expander, 1104 collimating lens, 1105 50% beam splitter, 1106 reflector, 1107 camera, 12 passive recovery tank, 13 temperature and pressure sensor, 14 vacuum pump. DETAILED DESCRIPTION

[0024] The following will be combined with the drawings in the embodiments of the utility model to clearly and completely describe the technical solutions in the embodiments of the utility model. Obviously, the described embodiments are only part of the embodiments of the utility model, not all of the embodiments. Based on the embodiments in the utility model, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the utility model.

[0025] like Figure 1 As shown, the transcritical homogeneous carbon dioxide test equipment includes a gas storage part: a carbon dioxide atmospheric pressure gas storage tank 1, a high-pressure gas storage tank 5, and a passive recovery tank 12; a booster part: a plunger pump 3 and an air compressor 4; a flow control part: a mass flow meter 8, valve switches at each node; a nozzle part: a nozzle 9, a pressure measurement module 10, and an optical measurement module 11; a temperature and pressure measurement module: a constant temperature module 6, a constant pressure module 7, and a temperature and pressure sensor 13; and a vacuum pump 14.

[0026] The condensation test unit for the transcritical homogeneous carbon dioxide test equipment includes a high-pressure gas storage tank 5, a mass flow meter 8, a light-transmissive nozzle 9 and a passive recovery tank 12 connected in sequence, and the nozzle 9 is connected to a temperature measurement module, a pressure measurement module 10 and an optical measurement module 11.

[0027] The inlet of the condensation test unit is intermittently connected with a carbon dioxide atmospheric pressure gas storage tank 1, a plunger pump 3 and an air compressor 4 for generating high-pressure carbon dioxide. After high-pressure compression, the carbon dioxide flows from the high-pressure part to the low-pressure gas storage tank, i.e., the passive recovery tank 12, under the action of the pressure difference. During the flow of carbon dioxide, non-equilibrium condensation occurs in the nozzle 9. The mass flowmeter 8 reflects the flow rate of the carbon dioxide fluid. The pressure measurement module 10 on the nozzle 9 monitors the discrete point pressure of the fluid in the nozzle 9. The optical measurement module 11 measures the condensed droplets in the nozzle 9 by injecting light laterally into the nozzle 9. The different refractive indices cause the received light signal to change, and the position of the condensed droplets, the size of the droplets, the growth of the droplets and other data can be obtained. By measuring the pressure, temperature, position, size and flow rate of the droplets generated when the carbon dioxide undergoes non-equilibrium condensation, the critical conditions for the condensation of carbon dioxide are obtained.

[0028] Based on the above embodiments, as a preferred implementation, Figure 2 As shown, the optical measurement module 11 includes a laser emitter 1101, a laser attenuator 1102, a beam expander 1103, a collimating lens 1104, a 50% beam splitter 1105, a reflector 1106, and a camera 1107. The laser emitter 1101, the laser attenuator 1102, the beam expander 1103, and the collimating lens 1104 are connected in sequence and are located on the left side of the nozzle 9. The 50% beam splitter 1105, the reflector 1106, and the camera 1107 are connected in sequence and are located on the right side of the nozzle 9. Two 50% beam splitters 1105 and two reflectors 1106 are respectively provided. After the laser beam passes through the 50% beam splitter 1105 and the transmitting mirror 1106, it is finally irradiated on the camera 1107.

[0029] After the laser emitter 1101 emits the laser, it is attenuated by the laser attenuator 1102 to reduce the laser power, and then expanded by 1103 and refracted by the collimating lens 1104. Then the laser is vertically irradiated on the light-transmitting panel 901 of the nozzle 9. After the laser passes through the nozzle 9, it is irradiated on the 50% beam splitter 1105, and then divided into two beams. After two reflections, position offset occurs, and interference occurs. The interference pattern is recorded by the camera 1107. Different refractive index data can be obtained by analyzing the pattern and converted into density data. The optical measurement module 11 measures according to the different refractive indices of carbon dioxide in gas and liquid states. The camera 1107 can measure different light interference fringes. When the interference fringes measured by the camera 1107 change significantly, it means that carbon dioxide has begun to condense. The pressure, temperature, flow rate, etc. at this time are recorded to obtain the characteristics of the condensation phenomenon. The pressure, temperature, flow rate and other parameters at this time are used as the reaction threshold of the corresponding sensor in the compressor to prevent carbon dioxide condensation from affecting the refrigeration efficiency.

[0030] Based on the above embodiments, as a preferred implementation, Figure 3 As shown, the nozzle 9 includes an arc panel that is symmetrical up and down, and the arc panel is connected to the light-transmitting panel 901 on the left and right. The cross-sectional shape of the nozzle 9 along the flow direction of carbon dioxide is a rectangle, and the area of ​​the rectangle gradually decreases and then gradually expands.

[0031] Specifically, the nozzle 9 includes expansion parts at both ends and a contraction part in the middle, and the pressure measurement module 10 is evenly connected to the contraction part. The pressure measurement modules are evenly spaced and inserted into the upper and lower symmetrical arc panels, and the depths of each pressure measurement module inserted into the arc panel are different. During the test, the volume of carbon dioxide expands inside the nozzle 9 and non-equilibrium condensation occurs. The pressure measurement modules 10 are evenly arranged inside the nozzle 9. The pressure measurement modules 10 are respectively connected to the upper and lower arc panels and are staggered so as to measure the pressure of each discrete point of the condensation phenomenon. The distribution length of the pressure measurement module 10 along the nozzle 9 should be slightly greater than the length of the contraction part. The pressure measurement module 10 can be a pressure sensor, and the pressure in the nozzle 9 is measured by the pressure sensor. The above pressure is the critical pressure for the condensation of carbon dioxide. The reaction threshold of the pressure sensor in the compressor is kept consistent with the pressure measured by the above pressure sensor, so as to avoid the condensation of carbon dioxide in the compressor.

[0032] On the basis of the above embodiment, as a preferred implementation, the temperature measurement module of the nozzle 9 includes an inlet temperature measurement module and an outlet temperature measurement module, the inlet temperature measurement module includes a constant temperature module 6 connected to the high-pressure gas storage tank 5, and the outlet temperature measurement module includes a temperature and pressure sensor 13 connected to the outlet of the passive recovery tank 12. The constant temperature module 6 and the temperature and pressure sensor 13 are both sensitive sensors, the constant temperature module 6 is a temperature sensor, the constant temperature module 6 and the temperature and pressure sensor 13 are respectively arranged before and after the inlet and outlet of the nozzle 9, and measure the initial temperature of carbon dioxide condensation and the temperature after condensation. The above initial temperature and the temperature after condensation are both used as critical conditions for carbon dioxide condensation, and the temperature sensor in the compressor needs to be set consistent with the above initial temperature and the temperature after condensation.

[0033] Based on the above embodiment, as a preferred implementation, the optical measurement module 11 includes a laser emitter 1101, a laser attenuator 1102, a beam expander 1103, and a collimating lens 1104 connected in sequence to one side of the nozzle 9, and the laser emission direction is perpendicular to the flow direction of carbon dioxide in the nozzle 9; the other side of the nozzle is connected in sequence to a 50% beam splitter 1105, a reflector 1106, and a camera 1107, and the 50% beam splitter 1105 and the reflector 1106 are arranged in pairs. Figure 2As shown, the optical measurement module 11 includes two pairs of adjacently arranged 50% beam splitters 1105 and reflectors 1106, and each pair of 50% beam splitters 1105 and reflectors 1106 is vertically arranged.

[0034] Based on the above embodiment, as a preferred implementation, the measuring direction of the optical measurement module 11 is perpendicular to the light-transmitting panel 901. The light-transmitting panels 901 are symmetrically arranged on the left and right sides of the nozzle 9. The laser emitted by the optical measurement module 11 passes through the light-transmitting panel 901, and then the camera 1107 of the optical measurement module 11 measures and records the droplets in the nozzle 9.

[0035] Based on the above embodiment, as a preferred implementation, the high-pressure gas storage tank 5 is connected to a constant pressure module 7 for pressure control. The constant pressure module 7 is connected to the outlet of the high-pressure gas storage tank 5, and controls the pressure of carbon dioxide in the high-pressure gas storage tank 5 by controlling the opening and closing of the plunger pump 3. The constant pressure module 7 includes a pressure sensor.

[0036] On the basis of the above embodiments, as a preferred implementation, a valve switch 1 21 is provided between the carbon dioxide atmospheric pressure gas storage tank 1 and the plunger pump 3, a valve switch 2 22 and a valve switch 3 23 are provided at the inlet and outlet connections of the high-pressure gas storage tank 5, a valve switch 4 24 is provided between the nozzle 9 and the passive recovery tank 12, and a valve switch 5 25 for vacuuming and a valve switch 6 26 for venting are connected to the inlet of the vacuum pump 14. The valve switch not only controls the flow rate of carbon dioxide as a switch, but also divides the test equipment into a front-end test part and a tail purge part. The high-pressure gas storage tank 5 is provided with a gas storage tank valve, and a valve switch 2 22 for controlling the entry into the gas storage tank and a valve switch 3 23 for controlling the outflow of the gas storage tank are provided on the pipeline. The flow direction of carbon dioxide is controlled by the cooperation of the gas storage tank valve and the valve switch 2 22 and the valve switch 3 23.

[0037] Based on the above embodiment, as a preferred implementation, the outlet of the passive recovery tank 12 is connected to a vacuum pump 14 for equipment pressure relief. The vacuum pump 14 is used to purge the entire test equipment after the test is completed, and collect carbon dioxide for subsequent reuse, while avoiding environmental pollution.

[0038] Based on the above embodiment, as a preferred implementation, the method for improving the efficiency of a refrigeration cycle using the transcritical homogeneous carbon dioxide test equipment comprises the following steps:

[0039] (1) Close valve switch 22 and valve switch 6 26, open the remaining valve switches, and use the vacuum pump 14 to adjust the pressure in the carbon dioxide condensation test unit to a suitable pressure;

[0040] (2) Close all valve switches, open valve switch 1 21, inject the carbon dioxide in the carbon dioxide atmospheric pressure gas storage tank 1 into the high-pressure gas storage tank 5 through the plunger pump, and control the carbon dioxide in the high-pressure gas storage tank 5 to reach the set temperature and pressure through the constant temperature module 6 and the constant pressure module 7;

[0041] (3) Open valve switch three 23 and valve switch four 24, and close other valve switches. Carbon dioxide flows from the high-pressure gas storage tank 5 to the passive recovery tank 12. The mass flow meter 8, the inlet temperature measurement module, the outlet temperature measurement module, the pressure measurement module 10 and the optical measurement module 11 are used to measure and record the position and size of the droplets generated when the carbon dioxide condenses, and the critical conditions such as the flow rate, pressure and temperature of the carbon dioxide condensation are obtained;

[0042] (4) Excess carbon dioxide is extracted through the vacuum pump 14, or the gas is released through the valve switch 26 to keep it consistent with the atmospheric pressure;

[0043] (5) A temperature and pressure sensor is provided in the compressor, and a carbon dioxide flow meter is provided in the carbon dioxide refrigeration cycle system. The temperature and pressure sensor and the carbon dioxide flow meter are connected to the control system. When the temperature, pressure and flow rate in the compressor reach the critical conditions for carbon dioxide condensation measured in the step, the operating power of the compressor is adjusted by the control system or the flow rate of carbon dioxide is adjusted by the flow valve to avoid carbon dioxide condensation, thereby avoiding a reduction in the efficiency of the compressor refrigeration cycle system.

[0044] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. Condensation test unit for transcritical homogeneous carbon dioxide test equipment, It is characterized in that The invention comprises a carbon dioxide condensation test unit, wherein the carbon dioxide condensation test unit comprises a high-pressure gas storage tank (5), a mass flow meter (8), a light-transmissive nozzle (9) and a passive recovery tank (12) which are connected in sequence, and the nozzle (9) is connected to a temperature measurement module, a pressure measurement module (10) and an optical measurement module (11).

2. The condensation test unit for a transcritical homogeneous carbon dioxide test apparatus according to claim 1, It is characterized in that The nozzle (9) comprises a vertically symmetrical curved panel, the curved panel being connected to light-transmitting panels (901) on the left and right sides, and the cross-sectional shape of the nozzle (9) along the flow direction of carbon dioxide is a rectangle, and the area of ​​the rectangle first gradually decreases and then gradually increases.

3. The condensation test unit for a transcritical homogeneous carbon dioxide test apparatus according to claim 2, It is characterized in that The temperature measurement module of the nozzle (9) comprises an inlet temperature measurement module and an outlet temperature measurement module, the inlet temperature measurement module comprises a constant temperature module (6) connected to the high-pressure gas storage tank (5), and the outlet temperature measurement module comprises a temperature and pressure sensor (13) connected to the outlet of the passive recovery tank (12).

4. The condensation test unit for a transcritical homogeneous carbon dioxide test apparatus according to claim 3, It is characterized in that The nozzle (9) comprises expansion parts at both ends and a contraction part in the middle, and a plurality of pressure measurement modules (10) are provided, and each pressure measurement module (10) is evenly connected to the contraction part.

5. The condensation test unit for a transcritical homogeneous carbon dioxide test apparatus according to claim 4, It is characterized in that The pressure measurement modules (10) are inserted into the vertically symmetrical curved panel at even intervals, and the depths of insertion of the pressure measurement modules (10) into the curved panel are different.

6. The condensation test unit for a transcritical homogeneous carbon dioxide test apparatus according to claim 5, It is characterized in that The measuring direction of the optical measurement module (11) is perpendicular to the light-transmitting panel (901).

7. The condensation test unit for a transcritical homogeneous carbon dioxide test apparatus according to claim 6, It is characterized in that The optical measurement module (11) comprises a laser emitter (1101), a laser attenuator (1102), a beam expander (1103), and a collimating lens (1104) which are sequentially connected to one side of the nozzle (9); the laser emission direction of the laser emitter (1101) is perpendicular to the flow direction of carbon dioxide in the nozzle (9); the other side of the nozzle (9) is sequentially connected to a 50% beam splitter (1105), a reflector (1106), and a camera (1107); the 50% beam splitter and the reflector are arranged in pairs.

8. The condensation test unit for a transcritical homogeneous carbon dioxide test apparatus according to claim 7, It is characterized in that The high-pressure gas storage tank (5) is connected to a constant pressure module (7) for pressure control.

9. The condensation test unit for a transcritical homogeneous carbon dioxide test apparatus according to claim 8, It is characterized in that The outlet of the passive recovery tank (12) is connected to a vacuum pump (14) for depressurizing the equipment.

10. The condensation test unit for a transcritical homogeneous carbon dioxide test apparatus according to claim 9, It is characterized in that The inlet and outlet connections of the high-pressure gas storage tank (5) are respectively provided with valve switch 2 (22) and valve switch 3 (23), and valve switch 4 (24) is provided between the nozzle (9) and the passive recovery tank (12).

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