Flow boiling heat transfer experiment test system and test method

Abstract

The invention discloses a test system and a test method for a flow boiling heat transfer experiment, and aims to provide a test system and a test method for accurately controlling the content of lubricating oil. The system comprises a working medium circulation subsystem, an electric heating subsystem and a data acquisition subsystem, the working medium circulation subsystem comprises a refrigerant branch, a lubricating oil branch and a test branch; the refrigerant branch comprises a condenser, and the refrigerant outlet end of the condenser is sequentially connected with a refrigerant liquid storage device, a working medium pump, a fourth valve, a heat exchanger and a refrigerant flow meter. The lubricating oil branch comprises a lubricating oil separator; a lubricating oil outlet of the lubricating oil separator, a lubricating oil reservoir, a lubricating oil pump and a lubricating oil flowmeter are connected in sequence; the test branch comprises a mixer, outlets of the refrigerant flow meter and the lubricating oil flow meter are connected to an inlet of the mixer, and an outlet of the mixer is sequentially connected with inlets of the preheating section, the visual flow boiling test section, the overheating section and the throttling valve. The system can accurately control the content of lubricating oil.

Description

Technical Field

[0001] The present invention relates to the field of measurement technology, and more specifically to a refrigerant flow boiling heat transfer experimental test system and a test method capable of adjusting the lubricating oil content. Background Art

[0002] With the rapid development of the national economy and the improvement of people's living standards, people have higher and higher requirements for environmental comfort. In terms of regulating environmental comfort, steam compression refrigeration and heat pump products (such as household air conditioners) have become an indispensable part of people's lives. In addition to the civil field, steam compression refrigeration and heat pump products have also been widely used in industrial and commercial fields, such as medical and pharmaceutical, supermarket refrigeration, cold chain transportation and food processing. Although the use of refrigeration and heat pump products has improved people's living standards and quality, it has also brought huge energy consumption. Therefore, the development of green and efficient refrigeration and heat pump technology and the improvement of the efficiency of refrigeration and heat pump systems are of great importance and significance in reducing building energy consumption and achieving the "dual carbon" goals.

[0003] In existing research, researchers usually optimize the design of the flow heat transfer process of pure working fluid in the heat exchanger with the goal of improving the performance and efficiency of the heat exchanger. However, in actual refrigeration and heat pump systems, a certain amount of lubricating oil is usually added to the compressor to promote lubrication, enhance heat dissipation, prevent leakage and reduce noise. Therefore, it is not the pure refrigerant that participates in the flow heat transfer process in the heat exchanger, but a mixture of refrigerant and a small amount of lubricating oil. As the system circulates, a small amount of lubricating oil in the compressor will be carried by the refrigerant and enter the various components of the system. The mixing of lubricating oil will inevitably change the thermal properties of the refrigerant, thereby affecting the flow heat transfer process in the heat exchanger. Therefore, the study of the flow boiling heat transfer of oil-containing refrigerant in the evaporator is more urgent, which is of great significance to the improvement of evaporator performance and system efficiency.

[0004] At present, the experimental systems used in the literature that consider the influence of lubricating oil are all pure refrigerant experimental systems. The lubricating oil is manually injected multiple times and the area where the lubricating oil is injected is evacuated. After the system has been running for several hours, the lubricating oil sampling section is removed and weighed to determine the lubricating oil content of the system. This method is cumbersome to operate, takes a long time, and consumes a large amount of refrigerant. In addition, if the refrigerant is replaced and the effect of lubricating oil content on the heat transfer of the refrigerant is studied again, the system must be cleaned with dichloromethane. Dichloromethane is on the list of Class 2A carcinogens and pollutes the air.

[0005] The patent document with the patent number of 200910050459.1 and the invention name of "CO2-oil mixture transcritical cycle heat transfer measurement device" discloses a refrigerant-lubricant oil mixed working medium heat transfer measurement device, which is driven by a compressor. The compressor usually uses an oil system, which inevitably causes oil to mix into the refrigerant, making it difficult to accurately control the oil content. Therefore, it is necessary to design a flow boiling heat transfer experimental test system that can adjust the lubricant content, which helps to reveal the flow boiling heat transfer mechanism of refrigerants and refrigerant-lubricant oil mixtures, and also helps to provide basic data for the development of flow boiling heat transfer prediction models. Summary of the invention

[0006] The purpose of the present invention is to provide a refrigerant flow boiling heat transfer experimental test system with adjustable lubricant oil content in order to address the technical defects existing in the prior art, so as to accurately control the lubricant oil content and provide a basis for revealing the flow boiling heat transfer mechanism of refrigerants and refrigerant-lubricant oil mixtures.

[0007] Another object of the present invention is to provide a test method for refrigerant flow boiling heat transfer experiment with adjustable lubricant content, so as to accurately control the lubricant content and help reveal the flow boiling heat transfer mechanism of refrigerants and refrigerant-lubricant mixtures.

[0008] The technical solution adopted to achieve the purpose of the present invention is: A flow boiling heat transfer experimental test system includes a working fluid circulation subsystem, an electric heating subsystem and a data acquisition subsystem; the working fluid circulation subsystem includes a refrigerant branch, a lubricating oil branch and a test branch; The refrigerant branch includes a condenser, the refrigerant outlet of the condenser is connected to the refrigerant reservoir, the working fluid pump, the fourth valve, the heat exchanger and the refrigerant flow meter in sequence, the heat exchanger is placed in a constant temperature liquid tank, and the cooling water system provides coldness for the condenser and the constant temperature liquid tank; a refrigerant filling / vacuuming port is provided on the top of the refrigerant reservoir; a bypass branch is provided between the refrigerant inlet of the condenser and the working fluid pump outlet, a bypass valve is provided on the bypass branch, and the bypass branch is used to achieve flow cooling of the refrigerant gas during testing to reduce the flow resistance in the pipeline; The lubricating oil branch includes a lubricating oil separator, the lubricating oil outlet of the lubricating oil separator is connected to the lubricating oil reservoir, the lubricating oil pump and the lubricating oil flow meter in sequence, and the top of the lubricating oil reservoir is provided with a lubricating oil filling / vacuuming port; the refrigerant outlet end of the lubricating oil separator is connected to the refrigerant inlet end of the condenser through a refrigerant shunt branch, and a third valve is provided on the refrigerant shunt branch; the outlet end of the lubricating oil flow meter is installed with a fifth valve; The test branch includes a mixer, the outlets of the refrigerant flow meter and the lubricating oil flow meter are connected to the inlet of the mixer, the outlet of the mixer is connected to the inlet of the preheating section, the visualized flow boiling test section, the superheating section and the throttle valve in sequence, the outlet of the throttle valve is connected to the inlet of the first valve and the second valve respectively, the outlet of the first valve is connected to the refrigerant inlet end of the condenser; the outlet of the second valve is connected to the inlet of the lubricating oil separator.

[0009] The data acquisition subsystem includes a test section wall temperature sensor, a differential pressure transmitter arranged at the inlet and outlet of the visualized flow boiling test section for measuring the working fluid pressure drop, and temperature sensors and pressure sensors respectively installed at the inlet and outlet positions of the preheating section, the outlet position of the visualized flow boiling test section, and the outlet positions of the refrigerant flow meter and the lubricating oil flow meter.

[0010] The visualized flow boiling test section is placed in a transparent air duct, and the temperature in the transparent air duct is controlled by an air temperature control module; the electric heating subsystem includes a preheating section voltage regulator, a test section voltage regulator, an overheating section voltage regulator, a preheating section power meter, a test section power meter, an overheating section power meter, a preheating section electric heater, an overheating section electric heater and a test section electric heater; the preheating section electric heater is connected to a power supply through the preheating section power meter and the preheating section voltage regulator; the test section electric heater is connected to a power supply through the test section power meter and the test section voltage regulator; the overheating section electric heater is connected to a power supply through the overheating section power meter and the overheating section voltage regulator.

[0011] The visualization part corresponding to the visualization flow boiling test section is equipped with a video collector for photographing the flow pattern of the working medium under boiling state and a light source for providing illumination for the video collector.

[0012] In the test of the refrigerant-lubricant oil mixed working medium, the working medium pump and the lubricant oil pump are turned on, the throttle valve, the second valve, the third valve, the fourth valve and the fifth valve are turned on, and the first valve is turned off; In the refrigerant branch, the refrigerant liquid in the refrigerant reservoir enters the heat exchanger placed in the constant temperature liquid tank under the drive of the working fluid pump; the refrigerant liquid is further cooled in the heat exchanger and becomes a refrigerant liquid in a supercooled state; the refrigerant liquid in a supercooled state enters the refrigerant flow meter for refrigerant flow measurement; wherein, the temperature of the liquid in the constant temperature liquid tank is lower than the required evaporation temperature, ensuring that the refrigerant is in a supercooled state after flowing out of the heat exchanger placed in the constant temperature liquid tank, and will not be throttled and evaporated into a gas-liquid mixture after passing through the refrigerant flow meter; In the lubricating oil branch, the lubricating oil liquid in the lubricating oil separator enters the lubricating oil reservoir, and under the action of the lubricating oil pump enters the lubricating oil flow meter to measure the lubricating oil flow; The refrigerant liquid in the supercooled state in the refrigerant branch and the lubricating oil in the lubricating oil branch enter the mixer and are fully mixed in the mixer to form a refrigerant-lubricating oil mixture liquid; the refrigerant-lubricating oil mixture liquid is heated in the preheating section and becomes a refrigerant-lubricating oil mixture with a specific dryness; the refrigerant-lubricating oil mixture with a specific dryness enters the visualized flow boiling test section and is heated in the visualized flow boiling test section to produce flow boiling; the refrigerant-lubricating oil mixture that has passed the visualized flow boiling test section enters the superheating section to be heated, and the refrigerant The refrigerant-lubricant mixture is completely evaporated; the gaseous refrigerant-lubricant mixture is throttled and depressurized by the throttle valve, and then enters the lubricant separator through the second valve; it is separated into lubricant liquid and refrigerant gas in the lubricant separator; the refrigerant gas enters the condenser through the third valve, is condensed into refrigerant liquid by the condenser, and then enters the refrigerant liquid storage tank, completing the circulation of the refrigerant-lubricant mixed working medium; when the lubricant content needs to be adjusted, the refrigerant flow rate and the lubricant flow rate are adjusted by adjusting the speed of the working medium pump and the lubricant pump, thereby adjusting the lubricant content.

[0013] When conducting a pure refrigerant flow boiling test, the fifth valve and the lubricating oil pump are closed; after the lubricating oil separator separates all the lubricating oil entering the lubricating oil separator, the second valve and the third valve are closed, and the first valve is opened; in the refrigerant branch, the refrigerant liquid in the refrigerant reservoir enters the heat exchanger placed in the constant temperature liquid tank under the drive of the working fluid pump; the refrigerant liquid is further cooled in the heat exchanger and becomes a refrigerant liquid in a supercooled state; the refrigerant liquid in a supercooled state enters the refrigerant flowmeter for refrigerant flow measurement; thereafter The refrigerant liquid in the supercooled state enters the preheating section after passing through the mixer, and is heated in the preheating section to become a refrigerant with a specific dryness; the refrigerant with a specific dryness enters the visualized flow boiling test section, and is heated in the visualized flow boiling test section to produce flow boiling; the refrigerant that has passed the visualized flow boiling test section enters the superheating section for heating, and all the refrigerant is evaporated; the gaseous refrigerant is throttled and depressurized by the throttle valve, and then enters the condenser through the first valve, is condensed into refrigerant liquid by the condenser, and then enters the refrigerant liquid storage tank to complete the refrigerant cycle.

[0014] A lubricating oil sight glass is installed at the inlet end of the lubricating oil pump, and a filter and a working fluid sight glass are installed at the inlet end of the working fluid pump; the lubricating oil separator is a cyclone separator, and the electric heating rod at the bottom of the lubricating oil separator is used to heat the lubricating oil to remove the refrigerant dissolved in the lubricating oil and reduce the viscosity of the lubricating oil; a visual liquid level gauge is installed on the outside of the refrigerant reservoir.

[0015] A test method for conducting a refrigerant-lubricant mixed working fluid experiment using the flow boiling heat transfer test system comprises the following steps: (1) Start the cooling water system and adjust the temperature of the liquid in the constant temperature liquid tank to the required evaporation temperature; close the first valve, the third valve and the fourth valve, open the bypass valve and the working fluid pump, and the refrigerant flows in the bypass cycle composed of the refrigerant liquid reservoir, the working fluid pump, the bypass valve and the condenser; when the refrigerant temperature drops to the required evaporation temperature, open the third valve and the fourth valve, close the bypass valve, and allow the refrigerant to enter the test branch; adjust the temperature of the liquid in the constant temperature liquid tank to a temperature 20°C-30°C lower than the required refrigerant evaporation temperature, ensure that the refrigerant is in a supercooled state after flowing out of the heat exchanger in the constant temperature liquid tank, and will not be throttled and evaporated into a gas-liquid mixture when passing through the refrigerant flow meter; (2) Opening the fifth valve and the lubricating oil pump to allow the lubricating oil to enter the test branch; and at the same time, opening the lubricating oil separator; (3) Turn on the preheating section voltage regulator, the test section voltage regulator and the overheating section voltage regulator in sequence; (4) Turning on the air temperature control module to make the air temperature in the transparent air duct consistent with the evaporation temperature; (5) Comprehensively adjusting the speed of the working fluid pump, the speed of the lubricating oil pump, the temperature of the cooling water system, the throttle valve opening and the output voltage of the preheating section voltage regulator to obtain the required evaporation pressure, mass flow rate, preheating section outlet dryness, and lubricating oil concentration under the working conditions; realizing the refrigerant-lubricating oil mixed working fluid cycle; (6) When the system reaches a stable state, data collection is performed.

[0016] The basis for judging whether the system operation has reached a stable state in step (5) is that the temperature value measured by the temperature sensor at each position changes within 2 minutes by ≤0.1°C.

[0017] After the data collection is completed, the video collector and the light source are turned on to shoot the flow pattern in the flow boiling process; Repeat step (5) to adjust the next set of test conditions until all test conditions are completed.

[0018] Compared with the prior art, the present invention has the following beneficial effects: 1. The flow boiling heat transfer experimental test system of the present invention is not driven by a compressor. Through the design of the refrigerant branch, the lubricating oil branch and the test branch, the lubricating oil content in the refrigerant can be easily adjusted by adjusting the speed of the working fluid pump and the lubricating oil pump. The refrigerant and the lubricating oil are fully separated by the superheating section and the lubricating oil separator to ensure that there is no lubricating oil in the refrigerant branch. There is no need to use cleaning fluids such as dichloromethane to clean the experimental test system, and then the refrigerant flow boiling heat transfer experiment under different lubricating oil contents can be carried out. The refrigerant and the lubricating oil can be fully mixed by the mixer to ensure the uniformity of the lubricating oil content.

[0019] 2. In the test system of the present invention, the visualized flow boiling test section is placed in a transparent air duct, and a structural design similar to an air curtain is used to ensure heat exchange between the test section and the external environment when the visualized flow boiling test section is visually observed, thereby preventing the flow pattern of the refrigerant-lubricant mixture from being affected, and contributing to the accuracy of the development of the flow boiling heat transfer prediction model.

[0020] 3. The test system of the present invention uses a working fluid pump instead of a refrigeration compressor, which can easily meet the requirements of the refrigerant mass flow rate, especially when the visual flow boiling test section is a microchannel heat exchanger, it can meet the requirements of the microchannel heat exchanger for a small refrigerant flow rate. In addition, the pump usually does not require lubrication, thereby reducing the possibility of oil contamination in the system and can relatively accurately control the oil content.

[0021] 4. The test system of the present invention can obtain the heat transfer and pressure drop data of the refrigerant-lubricant oil mixture in real time, and it is convenient for the operator to adjust the inlet temperature, pressure, heat flux density, dryness, lubricant oil content, mass flow rate and other data of the test section, and the experiment is simple.

[0022] 5. In the test system of the present invention, the mixer can promote the mixing of the refrigerant and the lubricating oil, greatly shortening the time required to operate the system for fully mixing the refrigerant and the lubricating oil.

[0023] 6. The testing method of the present invention can realize the flow boiling heat transfer experiment of the refrigerant-lubricant mixture under different lubricant contents, can accurately control the lubricant content, help to reveal the flow boiling heat transfer mechanism of the refrigerant and the refrigerant-lubricant mixture, and provide basic data for the development of the flow boiling heat transfer prediction model. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 Shown is a schematic diagram of the flow boiling heat transfer experimental test system of the present invention. DETAILED DESCRIPTION

[0025] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0026] Figure 1The schematic diagram of the flow boiling heat transfer experimental test system of the present invention is shown, which includes a working medium circulation subsystem, an electric heating subsystem and a data acquisition subsystem. The working medium circulation subsystem includes a refrigerant branch, a lubricating oil branch and a test branch.

[0027] The refrigerant branch includes a condenser 10, the refrigerant outlet of the condenser 10 is connected to a refrigerant reservoir 11, a working fluid pump 14, a fourth valve 15, a heat exchanger 17 and a refrigerant flowmeter 18 in sequence, the heat exchanger 17 is placed in a constant temperature liquid tank 16, and a cooling water system provides cooling for the condenser 10 and the constant temperature liquid tank 16. A refrigerant filling / vacuuming port is provided at the top of the refrigerant reservoir 11 for filling refrigerant and vacuuming. A bypass branch is provided between the refrigerant inlet of the condenser 10 and the outlet of the working fluid pump 14, and a bypass valve 23 is provided on the bypass branch. The bypass branch is used to realize the flow cooling of the refrigerant gas during testing and reduce the flow resistance in the pipeline. The function of the refrigerant reservoir 11 is, on the one hand, to buffer the liquid working fluid flowing out of the condenser and stabilize the circulation system, and on the other hand, to separate the gas-liquid two-phase working fluid, prevent the gas from entering the working fluid pump 14, and avoid gas plugging of the gear-type working fluid pump. The condenser 10 is preferably a shell-and-tube condenser. The heat exchanger 17 is preferably a coiled-tube heat exchanger.

[0028] The lubricating oil branch includes a lubricating oil separator 24, the lubricating oil outlet of the lubricating oil separator 24 is connected to the lubricating oil reservoir 37, the lubricating oil pump 25 and the lubricating oil flow meter 26 in sequence, and the top of the lubricating oil reservoir 37 is provided with a lubricating oil filling / vacuuming port 37a for filling lubricating oil and vacuuming. The refrigerant outlet of the lubricating oil separator 24 is connected to the refrigerant inlet of the condenser 10 through a refrigerant shunt branch, and the refrigerant shunt branch is provided with a third valve 9. The outlet of the lubricating oil flow meter 26 is installed with a fifth valve 27.

[0029] The test branch includes a mixer 19, the outlets of the refrigerant flow meter 18 and the lubricating oil flow meter 26 are connected to the inlet of the mixer 19, the outlet of the mixer 19 is connected to the inlet of the preheating section 20, the visual flow boiling test section 1, the superheating section 4 and the throttle valve 6 in sequence, the outlet of the throttle valve 6 is connected to the inlet of the first valve 7 and the second valve 8 respectively, the outlet of the first valve 7 is connected to the refrigerant inlet end of the condenser 10; the outlet of the second valve 8 is connected to the inlet of the lubricating oil separator 24. By adjusting the opening of the throttle valve 6, the flow rate of the working fluid and the evaporation pressure of the working fluid can be adjusted. The function of the condenser 10 in the refrigerant branch is, on the one hand, to condense the refrigerant vapor generated in the preheating section and the visual flow boiling test section, and on the other hand, it can also play a role in adjusting the evaporation pressure of the working fluid.

[0030] The composition of the data acquisition subsystem can be set according to the needs of the data required for the test. In this embodiment, the data acquisition subsystem includes a test section wall temperature sensor, a differential pressure transmitter 22 arranged at the inlet and outlet of the visual flow boiling test section 1 for measuring the pressure drop of the working fluid, and a temperature sensor 28 and a pressure sensor 29 respectively installed at the inlet and outlet positions of the preheating section 20, the outlet position of the visual flow boiling test section 1, the refrigerant flow meter 18, and the outlet position of the lubricating oil flow meter 26.

[0031] The working fluid pump 14 is preferably a magnetic gear pump, and the lubricating oil pump 25 is preferably a plunger pump. The bypass valve 23 is a ball valve. The working fluid pump 14 is externally connected to a servo motor, through which the gear pump speed can be accurately adjusted, thereby adjusting the working fluid flow in the system, and cooperating with the opening of the bypass valve 23 to control the flow and inlet pressure of the refrigerant.

[0032] Furthermore, the visualized flow boiling test section 1 is placed in a transparent air duct 2, and the temperature in the transparent air duct is controlled by an air temperature control module 3. The air temperature control module 3 adopts a solution of the prior art.

[0033] In this embodiment, the electric heating subsystem includes a preheating section voltage regulator 21, a test section voltage regulator 33, an overheating section voltage regulator 5, a preheating section power meter 34, a test section power meter 35, an overheating section power meter 36, a preheating section electric heater 38, an overheating section electric heater 39 and a test section electric heater 40. The preheating section electric heater 38 is connected to a power source through the preheating section power meter 34 and the preheating section voltage regulator 21; the test section electric heater 40 is connected to a power source through the test section power meter 35 and the test section voltage regulator 33; and the overheating section electric heater 39 is connected to a power source through the overheating section power meter 36 and the overheating section voltage regulator 5.

[0034] In order to facilitate the observation of the flow pattern, a video collector 31 for shooting the flow pattern of the working medium under boiling state and a light source 32 for providing illumination for the video collector are installed in the visualization part corresponding to the visualization flow boiling test section 1. The video collector of this embodiment is a high-speed camera, the shooting frame number of the high-speed camera is set to 4000fps, and the image resolution is 1024×1024 pixels. The light source is a 65W high-brightness optical fiber cold light source.

[0035] In the test of the refrigerant-lubricant mixed working fluid, the working fluid pump 14 and the lubricant pump 25 are turned on, the throttle valve 6, the second valve 8, the third valve 9, the fourth valve 15 and the fifth valve 27 are turned on, and the first valve 7 is turned off. In the refrigerant branch, the refrigerant liquid in the refrigerant liquid reservoir 11 enters the heat exchanger 17 placed in the constant temperature liquid tank 16 under the drive of the working fluid pump 14; the refrigerant liquid is further cooled in the heat exchanger 17 and becomes a refrigerant liquid in a supercooled state; the refrigerant liquid in a supercooled state enters the refrigerant flow meter 18 for refrigerant flow measurement. Among them, the temperature of the liquid in the constant temperature liquid tank 16 is lower than the required evaporation temperature, ensuring that the refrigerant is in a supercooled state after flowing out of the heat exchanger 17 placed in the constant temperature liquid tank, and will not be throttled and evaporated into a gas-liquid mixture after passing through the refrigerant flow meter 18. In the lubricating oil branch, the lubricating oil liquid in the lubricating oil separator 24 enters the lubricating oil reservoir 37, and enters the lubricating oil flow meter 26 to measure the lubricating oil flow under the action of the lubricating oil pump 25. The refrigerant liquid in the supercooled state in the refrigerant branch and the lubricating oil in the lubricating oil branch enter the mixer 19, and are fully mixed in the mixer 19 to form a refrigerant-lubricating oil mixture liquid. The refrigerant-lubricating oil mixture liquid is heated in the preheating section 20 and becomes a refrigerant-lubricating oil mixture with a specific dryness; the refrigerant-lubricating oil mixture with a specific dryness enters the visualized flow boiling test section 1, and is heated in the visualized flow boiling test section to produce flow boiling. The refrigerant-lubricating oil mixture that has passed through the visualized flow boiling test section 1 enters the superheating section 4 for heating, and completely evaporates the refrigerant; the gaseous refrigerant-lubricating oil mixture is throttled and depressurized by the throttle valve 6, and then enters the lubricating oil separator 24 through the second valve 8. Under the action of the lubricating oil separator 24, it is separated into lubricating oil liquid and refrigerant gas. The refrigerant gas enters the condenser 10 through the third valve 9, is condensed into refrigerant liquid through the condenser 10, and then enters the refrigerant liquid storage tank 11, completing the cycle of the refrigerant-lubricating oil mixed working medium.

[0036] The refrigerant flow rate and the lubricating oil flow rate are adjusted by adjusting the rotation speed of the working fluid pump 14 and the lubricating oil pump 25, thereby adjusting the lubricating oil content.

[0037] When the pure refrigerant flow boiling test is performed, the fifth valve 27 and the lubricating oil pump 25 are closed; after the lubricating oil separator 24 separates all the lubricating oil entering the lubricating oil separator, the second valve 8 and the third valve 9 are closed, and the first valve 7 is opened. In the refrigerant branch, the refrigerant liquid in the refrigerant liquid reservoir 11 enters the heat exchanger 17 placed in the constant temperature liquid tank 16 under the drive of the working fluid pump 14. The refrigerant liquid is further cooled in the heat exchanger 17 and becomes a refrigerant liquid in a supercooled state; the refrigerant liquid in a supercooled state enters the refrigerant flow meter 18 for refrigerant flow measurement. Afterwards, the refrigerant liquid in the supercooled state enters the preheating section 20 after the mixer 19, is heated in the preheating section 20, and becomes a refrigerant with a specific dryness; the refrigerant with a specific dryness enters the visualized flow boiling test section 1, is heated in the visualized flow boiling test section to produce flow boiling; the refrigerant passing through the visualized flow boiling test section 1 enters the superheating section 4 for heating, and all the refrigerant is evaporated; the gaseous refrigerant is throttled and reduced in pressure by the throttle valve 6, and then enters the condenser 10 through the first valve 7, is condensed into refrigerant liquid by the condenser 10, and then enters the refrigerant liquid storage tank 11, completing the pure refrigerant cycle.

[0038] In order to prevent the influence of impurities in the refrigerant and to facilitate observation of whether the refrigerant contains gas, a filter 12 and a working fluid sight glass 13 are installed at the inlet end of the working fluid pump 14. In order to facilitate observation of whether the lubricating oil contains gas, a lubricating oil sight glass 30 is installed at the inlet end of the lubricating oil pump. Whether there is gas is observed through the working fluid sight glass 13 and the lubricating oil sight glass 30 to ensure the safe operation of the working fluid pump 14 and the lubricating oil pump 25.

[0039] In this embodiment, the lubricating oil separator 24 is a cyclone separator, and the electric heating rod at the bottom of the lubricating oil separator 24 is used to heat the lubricating oil to remove the refrigerant dissolved in the lubricating oil and reduce the viscosity of the lubricating oil. The refrigerant flow meter 18 and the lubricating oil flow meter 26 are Coriolis mass flow meters.

[0040] A visual liquid level gauge 11 b is installed outside the refrigerant liquid reservoir 11 , and the liquid level in the refrigerant liquid reservoir 11 can be determined by observing the liquid level of the liquid level gauge.

[0041] The preheating section 20, the visualized flow boiling test section 1 and the overheating section 4 in the present invention can all adopt the structures in the prior art. In the present embodiment, the preheating section 20 and the overheating section 4 are both copper tubes. A layer of high temperature resistant insulating tape is wrapped around the outside of the copper tube, a resistance wire is wrapped around the outside of the insulating tape, and a layer of high temperature resistant insulating tape is also wrapped around the outside of the resistance wire. Then, the preheating section 20 and the overheating section 4 are fixed with plaster. If the visualized flow boiling test section is a round tube, heat transfer is performed by wrapping the resistance wire around the round tube. If the visualized flow boiling test section is a flat channel, a ceramic heating plate can be attached to the heat transfer block for heat transfer, or a heating rod can be inserted into the heat transfer block for heat transfer.

[0042] In this embodiment, the first valve 7 , the second valve 8 , the third valve 9 , the fourth valve 15 and the fifth valve 27 may all be stop valves.

[0043] In utilizing the present invention Figure 1 Before testing the flow boiling heat transfer experimental test system shown, preliminary preparations need to be done: (1) The lubricating oil is weighed using a precision scale and heated to remove the water in the lubricating oil. Then, a certain mass of lubricating oil is injected into the lubricating oil branch through the lubricating oil filling / vacuuming port 37a.

[0044] (2) Connect the refrigerant charging / vacuuming port 11a to the vacuum pump interface through the refrigerant charging pipe, and turn on the vacuum pump to evacuate the system. Since there are many valves in the system, all valves must be opened during vacuuming. The vacuuming time is 2 hours to 4 hours.

[0045] (3) After the vacuuming is completed, the second valve 8, the third valve 9 and the fifth valve 27 are closed. Refrigerant is charged into the system through the refrigerant charging / vacuuming port 11a. The refrigerant charging status can be observed through the visual liquid level gauge 11b of the refrigerant accumulator 11. When the refrigerant liquid level reaches two-thirds of the height of the refrigerant accumulator 11, the refrigerant charging is stopped and the valve of the refrigerant charging / vacuuming port 11a is closed.

[0046] After the preliminary preparation work is completed, the test is carried out. The test method of the refrigerant-lubricant mixed working medium of the present invention comprises the following steps: (1) Turn on the cooling water system and adjust the temperature of the liquid in the constant temperature liquid tank 16 to the required evaporation temperature. Close the first valve 7, the third valve 9 and the fourth valve 15, open the bypass valve 23 and the working fluid pump 14, and the refrigerant flows in the bypass cycle composed of the refrigerant liquid reservoir 11, the working fluid pump 14, the bypass valve 23 and the condenser 10, so that the refrigerant is cooled from room temperature to near the evaporation temperature as quickly as possible. When the refrigerant temperature drops to near the required evaporation temperature, the third valve 9 and the fourth valve 15 can be opened, and the bypass valve 23 can be closed to allow the refrigerant to enter the test branch. If the refrigerant is not cooled by flowing in the bypass cycle, the system pipeline is filled with refrigerant gas, the flow resistance in the pipeline is large, and it is difficult to circulate the refrigerant through the pump. The liquid temperature in the constant temperature liquid tank 16 is adjusted to a temperature 20°C-30°C lower than the required refrigerant evaporation temperature to ensure that the refrigerant is in a supercooled state after flowing out of the heat exchanger 17 placed in the constant temperature liquid tank, and will not be throttled and evaporated into a gas-liquid mixture when passing through the refrigerant flow meter 18.

[0047] (2) Open the fifth valve 27 and the lubricating oil pump 25 to allow the lubricating oil to enter the test circuit. At the same time, open the lubricating oil separator 24 to separate the lubricating oil from the refrigerant.

[0048] (3) The preheating section voltage regulator 21, the test section voltage regulator 33 and the superheating section voltage regulator 5 are turned on in sequence.

[0049] (4) Turn on the air temperature control module 3 to make the air temperature in the transparent air duct 2 consistent with the evaporation temperature.

[0050] (5) Comprehensively adjust the speed of the working fluid pump 14, the speed of the lubricating oil pump 25, the temperature of the cooling water system, the opening of the throttle valve 6 and the output voltage of the preheating section voltage regulator 21 to obtain the required evaporation pressure, mass flow rate, preheating section outlet dryness, and lubricating oil concentration. At this time, a refrigerant-lubricant mixed working medium cycle is formed: in the refrigerant branch, the refrigerant liquid in the refrigerant reservoir 11 enters the heat exchanger 17 placed in the constant temperature liquid tank 16 under the drive of the working medium pump 14; the refrigerant liquid is further cooled in the heat exchanger 17 and becomes a refrigerant liquid in a supercooled state; the refrigerant liquid in a supercooled state enters the refrigerant flowmeter 18 for refrigerant flow measurement. Among them, the temperature of the liquid in the constant temperature liquid tank 16 is lower than the required evaporation temperature, ensuring that the refrigerant is in a supercooled state after flowing out of the heat exchanger 17 placed in the constant temperature liquid tank, and will not be throttled and evaporated into a gas-liquid mixture after passing through the refrigerant flowmeter 18. In the lubricating oil branch, the lubricating oil liquid in the lubricating oil separator 24 enters the lubricating oil reservoir 37, and enters the lubricating oil flowmeter 26 under the action of the lubricating oil pump 25 for lubricating oil flow measurement. The refrigerant liquid in the supercooled state in the refrigerant branch and the lubricating oil in the lubricating oil branch enter the mixer 19, and are fully mixed in the mixer 19 to form a refrigerant-lubricating oil mixture liquid. The refrigerant-lubricating oil mixture liquid is heated in the preheating section 20 and becomes a refrigerant-lubricating oil mixture with a specific dryness; the refrigerant-lubricating oil mixture with a specific dryness enters the visualized flow boiling test section 1, and is heated in the visualized flow boiling test section to produce flow boiling. The refrigerant-lubricating oil mixture that has passed the visualized flow boiling test section 1 enters the superheating section 4 for heating, and all the refrigerant is evaporated; the gaseous refrigerant-lubricating oil mixture is throttled and depressurized by the throttle valve 6, and then enters the lubricating oil separator 24 through the second valve 8. Under the action of the lubricating oil separator 24, it is separated into lubricating oil liquid and refrigerant gas. The refrigerant gas enters the condenser 10 through the third valve 9, is condensed into refrigerant liquid through the condenser 10, and then enters the refrigerant liquid storage tank 11, completing the cycle of the refrigerant-lubricating oil mixed working medium.

[0051] (6) Under this condition, when the system reaches a stable state, that is, the temperature value measured by all temperature sensors changes by ≤0.1°C within 2 minutes, data collection is performed.

[0052] In this embodiment, the temperature values ​​collected by the temperature sensors installed at the inlet and outlet positions of the preheating section 20, the outlet position of the visual flow boiling test section 1, the refrigerant flow meter 18 and the outlet position of the lubricating oil flow meter, the pressure value collected by the pressure sensor, the pressure drop of the differential pressure transmitter 22, the power value of the test section power meter 35, the power values ​​of the preheating section power meter 21 and the superheating section power meter 5, the mass flow rates of the refrigerant flow meter 18 and the lubricating oil flow meter 26, and the test section wall temperature are collected and recorded.

[0053] After the data collection is completed, the video collector 31 and the light source 32 are turned on to shoot the flow pattern during the flow boiling process.

[0054] (7) Repeat step (5) to adjust and obtain the next set of test conditions until all test conditions are completed.

[0055] When the lubricating oil content needs to be adjusted, the rotation speeds of the working fluid pump 14 and the lubricating oil pump 25 are adjusted to adjust the refrigerant flow rate and the lubricating oil flow rate, thereby adjusting the lubricating oil content.

[0056] The flow boiling heat transfer test system of the present invention can easily adjust the lubricating oil content in the refrigerant through the design of the refrigerant branch, the lubricating oil branch and the test branch, and there is no need to use a cleaning fluid such as dichloromethane to clean the test system, so as to carry out the refrigerant flow boiling heat transfer experiment under different lubricating oil contents. At the same time, the test system uses a working fluid pump instead of a refrigeration compressor, thereby reducing the possibility of oil contamination in the system and being able to control the oil content relatively accurately.

[0057] The above is only a preferred embodiment of the present invention. It should be pointed out that, for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A flow boiling heat transfer experimental test system, characterized in that: It includes a working fluid circulation subsystem, an electric heating subsystem and a data acquisition subsystem; the working fluid circulation subsystem includes a refrigerant branch, a lubricating oil branch and a test branch; The refrigerant branch includes a condenser, the refrigerant outlet of the condenser is connected to the refrigerant reservoir, the working fluid pump, the fourth valve, the heat exchanger and the refrigerant flow meter in sequence, the heat exchanger is placed in a constant temperature liquid tank, and the cooling water system provides coldness for the condenser and the constant temperature liquid tank; a refrigerant filling / vacuuming port is provided on the top of the refrigerant reservoir; a bypass branch is provided between the refrigerant inlet of the condenser and the working fluid pump outlet, a bypass valve is provided on the bypass branch, and the bypass branch is used to achieve flow cooling of the refrigerant gas during testing to reduce the flow resistance in the pipeline; The lubricating oil branch includes a lubricating oil separator, the lubricating oil outlet of the lubricating oil separator is connected to the lubricating oil reservoir, the lubricating oil pump and the lubricating oil flow meter in sequence, and the top of the lubricating oil reservoir is provided with a lubricating oil filling / vacuuming port; the refrigerant outlet end of the lubricating oil separator is connected to the refrigerant inlet end of the condenser through a refrigerant shunt branch, and a third valve is provided on the refrigerant shunt branch; the outlet end of the lubricating oil flow meter is installed with a fifth valve; The test branch includes a mixer, the outlets of the refrigerant flow meter and the lubricating oil flow meter are connected to the inlet of the mixer, the outlet of the mixer is connected to the inlet of the preheating section, the visualized flow boiling test section, the superheating section and the throttle valve in sequence, the outlet of the throttle valve is connected to the inlet of the first valve and the second valve respectively, the outlet of the first valve is connected to the refrigerant inlet end of the condenser; the outlet of the second valve is connected to the inlet of the lubricating oil separator.

2. The flow boiling heat transfer experimental test system according to claim 1, characterized in that: The data acquisition subsystem includes a test section wall temperature sensor, a differential pressure transmitter arranged at the inlet and outlet of the visualized flow boiling test section for measuring the working fluid pressure drop, and temperature sensors and pressure sensors respectively installed at the inlet and outlet positions of the preheating section, the outlet position of the visualized flow boiling test section, and the outlet positions of the refrigerant flow meter and the lubricating oil flow meter.

3. The flow boiling heat transfer experimental test system according to claim 2, characterized in that: The visualized flow boiling test section is placed in a transparent air duct, and the temperature in the transparent air duct is controlled by an air temperature control module; the electric heating subsystem includes a preheating section voltage regulator, a test section voltage regulator, an overheating section voltage regulator, a preheating section power meter, a test section power meter, an overheating section power meter, a preheating section electric heater, an overheating section electric heater and a test section electric heater; the preheating section electric heater is connected to a power supply through the preheating section power meter and the preheating section voltage regulator; the test section electric heater is connected to a power supply through the test section power meter and the test section voltage regulator; the overheating section electric heater is connected to a power supply through the overheating section power meter and the overheating section voltage regulator.

4. The flow boiling heat transfer experimental test system according to claim 3, characterized in that: The visualization part corresponding to the visualization flow boiling test section is equipped with a video collector for photographing the flow pattern of the working medium under boiling state and a light source for providing illumination for the video collector.

5. The flow boiling heat transfer experimental test system according to claim 3, characterized in that: In the test of the refrigerant-lubricant oil mixed working medium, the working medium pump and the lubricant oil pump are turned on, the throttle valve, the second valve, the third valve, the fourth valve and the fifth valve are turned on, and the first valve is closed; In the refrigerant branch, the refrigerant liquid in the refrigerant liquid reservoir enters the heat exchanger placed in the constant temperature liquid tank under the drive of the working fluid pump; The refrigerant liquid is further cooled in the heat exchanger to become a refrigerant liquid in a supercooled state; the refrigerant liquid in a supercooled state enters the refrigerant flowmeter for refrigerant flow measurement; wherein the temperature of the liquid in the constant temperature liquid tank is lower than the required evaporation temperature, ensuring that the refrigerant is in a supercooled state after flowing out of the heat exchanger placed in the constant temperature liquid tank, and will not be throttled and evaporated into a gas-liquid mixture after passing through the refrigerant flowmeter; In the lubricating oil branch, the lubricating oil liquid in the lubricating oil separator enters the lubricating oil reservoir, and under the action of the lubricating oil pump enters the lubricating oil flow meter to measure the lubricating oil flow; The refrigerant liquid in the supercooled state in the refrigerant branch and the lubricating oil in the lubricating oil branch enter the mixer and are fully mixed in the mixer to form a refrigerant-lubricating oil mixture liquid; the refrigerant-lubricating oil mixture liquid is heated in the preheating section and becomes a refrigerant-lubricating oil mixture with a specific dryness; the refrigerant-lubricating oil mixture with a specific dryness enters the visualized flow boiling test section and is heated in the visualized flow boiling test section to produce flow boiling; the refrigerant-lubricating oil mixture that has passed the visualized flow boiling test section enters the superheating section to be heated, and the refrigerant The refrigerant-lubricant mixture is completely evaporated; the gaseous refrigerant-lubricant mixture is throttled and depressurized by the throttle valve, and then enters the lubricant separator through the second valve; it is separated into lubricant liquid and refrigerant gas in the lubricant separator; the refrigerant gas enters the condenser through the third valve, is condensed into refrigerant liquid by the condenser, and then enters the refrigerant liquid storage tank, completing the circulation of the refrigerant-lubricant mixed working medium; when the lubricant content needs to be adjusted, the refrigerant flow rate and the lubricant flow rate are adjusted by adjusting the speed of the working medium pump and the lubricant pump, thereby adjusting the lubricant content.

6. The flow boiling heat transfer experimental test system according to claim 3, characterized in that: When conducting a pure refrigerant flow boiling test, the fifth valve and the lubricating oil pump are closed; after the lubricating oil separator separates all the lubricating oil entering the lubricating oil separator, the second valve and the third valve are closed, and the first valve is opened; in the refrigerant branch, the refrigerant liquid in the refrigerant liquid reservoir enters the heat exchanger placed in the constant temperature liquid tank under the drive of the working fluid pump; The refrigerant liquid is further cooled in the heat exchanger and becomes a refrigerant liquid in a supercooled state; the refrigerant liquid in a supercooled state enters the refrigerant flowmeter to measure the refrigerant flow; thereafter, the refrigerant liquid in a supercooled state enters the preheating section after passing through the mixer, is heated in the preheating section, and becomes a refrigerant with a specific dryness; Refrigerant with a specific dryness enters the visualized flow boiling test section, where it is heated to produce flow boiling; the refrigerant that has passed the visualized flow boiling test section enters the superheating section for heating, and all the refrigerant is evaporated; the gaseous refrigerant is throttled and depressurized by the throttle valve, and then enters the condenser through the first valve, where it is condensed into refrigerant liquid, and then enters the refrigerant liquid storage tank, completing the refrigerant cycle.

7. The flow boiling heat transfer experimental test system according to claim 4, characterized in that: A lubricating oil sight glass is installed at the inlet end of the lubricating oil pump, and a filter and a working fluid sight glass are installed at the inlet end of the working fluid pump; the lubricating oil separator is a cyclone separator, and the electric heating rod at the bottom of the lubricating oil separator is used to heat the lubricating oil to remove the refrigerant dissolved in the lubricating oil and reduce the viscosity of the lubricating oil; a visual liquid level gauge is installed on the outside of the refrigerant reservoir.

8. A test method for conducting a refrigerant-lubricant mixed working fluid experiment using the flow boiling heat transfer test system of claim 4, characterized in that: The steps include: (1) Start the cooling water system and adjust the temperature of the liquid in the constant temperature liquid tank to the required evaporation temperature; close the first valve, the third valve and the fourth valve, open the bypass valve and the working fluid pump, and the refrigerant flows in the bypass cycle composed of the refrigerant liquid reservoir, the working fluid pump, the bypass valve and the condenser; when the refrigerant temperature drops to the required evaporation temperature, open the third valve and the fourth valve, close the bypass valve, and allow the refrigerant to enter the test branch; adjust the temperature of the liquid in the constant temperature liquid tank to a temperature 20°C-30°C lower than the required refrigerant evaporation temperature, ensure that the refrigerant is in a supercooled state after flowing out of the heat exchanger in the constant temperature liquid tank, and will not be throttled and evaporated into a gas-liquid mixture when passing through the refrigerant flow meter; (2) Opening the fifth valve and the lubricating oil pump to allow the lubricating oil to enter the test branch; and at the same time, opening the lubricating oil separator; (3) Turn on the preheating section voltage regulator, the test section voltage regulator and the overheating section voltage regulator in sequence; (4) Turning on the air temperature control module to make the air temperature in the transparent air duct consistent with the evaporation temperature; (5) Comprehensively adjusting the speed of the working fluid pump, the speed of the lubricating oil pump, the temperature of the cooling water system, the throttle valve opening, and the output voltage of the preheating section voltage regulator to obtain the required evaporation pressure, mass flow rate, preheating section outlet dryness, and lubricating oil concentration under the working conditions; Realize the refrigerant-lubricant mixed working medium cycle; (6) When the system reaches a stable state, data collection is performed.

9. The testing method according to claim 8, characterized in that: The basis for judging whether the system operation has reached a stable state in step (5) is that the temperature value measured by the temperature sensor at each position changes within 2 minutes by ≤0.1°C.

10. The testing method according to claim 8 or 9, characterized in that: After the data collection is completed, the video collector and the light source are turned on to shoot the flow pattern during the flow boiling process; step (5) is repeated to adjust the next set of test conditions until all test conditions are completed.

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