A method for simultaneously measuring a plurality of thermophysical properties of a refrigerant / lubricant mixture

Abstract

This invention discloses a method for simultaneously measuring multiple thermophysical properties of a refrigerant / lubricating oil mixture. The method involves evacuating a vibrating string device, controlling the pressure and temperature to a set value to achieve a constant temperature and pressure state; calibrating the volume of the cavity and pipelines of the vibrating string device; filling the vibrating string device with lubricating oil and refrigerant; measuring the density and viscosity of the mixture at the test temperature and pressure using the vibrating string method; measuring the pressure under the current state, which is the saturated vapor pressure of the refrigerant and lubricating oil mixture; and calculating the solubility of the refrigerant in the lubricating oil at the test temperature and pressure based on the obtained data. This invention provides a simple method for simultaneously measuring multiple physical properties such as density, viscosity, saturated vapor pressure, and solubility without repeated sample filling, simplifying past measurement steps, saving sample usage, facilitating rapid acquisition of experimental data for desired physical properties, and improving measurement efficiency.

Description

Technical Field

[0001] This invention relates to the field of fluid thermophysical property measurement, and in particular to a method for simultaneously measuring multiple thermophysical properties of refrigerant / lubricating oil mixtures. This method can be used for practical teaching of courses related to thermophysical property testing, and can also be used for measuring related properties in actual production, daily life, and scientific research. Background Technology

[0002] Density, viscosity, saturation pressure, and solubility are all crucial thermophysical properties, parameters essential for energy science and chemical engineering. These properties vary among different substances and change with temperature. During the operation of a compression refrigeration system, the refrigerant inevitably comes into contact with and mixes with the lubricating oil, entering the system circulation together. The participation of the lubricating oil significantly impacts compressor performance, flow and heat transfer in the heat exchanger, and the throttling process in the capillary tube. Due to the significant differences in thermophysical properties between refrigerant and lubricating oil, the thermophysical properties of the mixture change drastically when the circulating working fluid changes from pure refrigerant to a refrigerant / lubricating oil mixture, thus affecting the refrigeration system's cycle performance.

[0003] The impact of lubricating oil entering heat exchange equipment with refrigerant on the refrigeration system is related to the miscibility of the refrigerant and lubricating oil. If the miscibility is poor, the lubricating oil in the compressor gradually decreases, leading to oil shortage and reduced lubrication and cooling efficiency. Excessive lubricating oil accumulation in the evaporator and condenser can clog pipes and reduce heat transfer performance. Higher solubility prevents pooling in the heat exchanger, facilitating oil return from the compressor. However, excessively high solubility can decrease the viscosity of the lubricating oil, failing to adequately lubricate the compressor's bearings and moving parts. Furthermore, the mixing of lubricating oil and refrigerant reduces the refrigerant density, decreasing the refrigerant flow into the compressor and thus lowering refrigeration efficiency. Therefore, determining the physical properties of the refrigerant and lubricating oil mixture, especially key factors affecting compressor performance such as solubility, saturated vapor pressure, density, and viscosity, is crucial for improving the refrigeration system's cycle efficiency and service life.

[0004] Currently, there are many studies on the measurement of solubility, density, and viscosity of refrigerant and lubricating oil mixtures. Regarding solubility, Jia et al. used the isovolute saturation method to measure the solubility of R32 in POE, PVE, and PAG oils; Morais et al. measured the solubility of R143a, R125, and R32 in VG32 at temperatures ranging from 248.15 K to 348.15 K using the gravimetric method. Regarding density and viscosity studies, Cavestri et al. used an oscillating viscometer to measure the solubility, density, and viscosity of R134a and VG32 mixtures; Tomoaki et al. used a glass tube densitometer and a vibrating cup viscometer, respectively, at temperatures ranging from 278.15 K to 288.15 K to measure the density and viscosity of R134a / POE VG32 and R134a / PAG VG32 mixtures at relatively low concentrations (refrigerant mass fraction less than 15%).

[0005] The above studies show that although there are many studies on the properties of mixtures of refrigerants and lubricating oils, most of them use different experimental methods and devices to study solubility, density and viscosity separately. The process of obtaining all the required thermophysical properties is very cumbersome and requires repeated sample filling, resulting in a large consumption of reagents. There is a lack of convenient methods that can obtain multiple thermophysical properties using a single device. Summary of the Invention

[0006] To address the technical problems of complex measurement processes and high reagent consumption in existing technologies for measuring the physical properties of mixtures, the present invention aims to provide a method for simultaneously measuring multiple thermophysical properties of refrigerant / lubricating oil mixtures. This method can simultaneously measure multiple physical properties such as density, viscosity, saturated vapor pressure, and solubility without repeated sample filling, simplifying the measurement steps, saving sample usage, facilitating the rapid acquisition of experimental data for the desired physical properties, and improving measurement efficiency.

[0007] To achieve the above objectives, the present invention employs the following technical solution:

[0008] A method for simultaneously measuring multiple thermophysical properties of a refrigerant / lubricating oil mixture includes the following steps:

[0009] Step S1: Evacuate the vibrating string device, control the pressure and temperature to the set value, and achieve a constant temperature and pressure state.

[0010] Step S2: Calibrate the volume of the cavity and pipeline of the vibrating string device to obtain the volume of the cavity and pipeline;

[0011] Step S3: Fill the vibrating string device with lubricating oil and refrigerant;

[0012] Step S4: After the temperature and pressure have stabilized again, the density and viscosity of the mixture at the test temperature and pressure are measured using the vibrating string method.

[0013] Step S5: Measure the pressure under the current condition. The pressure is the saturated vapor pressure of the refrigerant and lubricating oil mixture.

[0014] Step S6: Calculate the solubility of the refrigerant in the lubricating oil at the test temperature and pressure based on the volume of the cavity and pipeline, the mass of the refrigerant, the mass of the lubricating oil, and the density of the mixture.

[0015] Furthermore, in step S1, the vibrating string device includes a sample filling port for lubricating oil and refrigerant, a pressure sensor, a lock-in amplifier, a temperature sensor, a flange, a constant temperature bath drain port, a constant temperature bath chamber, a constant temperature bath inlet, a sample discharge port, an aluminum alloy weight, a vibrating string, a pressure chamber, a magnet, and a vibrating string clamp and magnet holder.

[0016] The constant temperature bath chamber is provided with a constant temperature bath drain port at the top and a constant temperature bath inlet at the bottom. A pressure chamber is provided inside the constant temperature bath chamber. A sample discharge port is provided at the bottom of the pressure chamber. A flange is provided at the top of the pressure chamber. The sample filling port is connected to the pressure chamber. A pressure sensor, a lock-in amplifier and a temperature sensor are inserted into the pressure chamber. A magnet frame is provided at the top of the pressure chamber. A vibrating string clamp and two magnets are provided on the magnet frame. One end of the vibrating string is fixed to the vibrating string clamp, and an aluminum alloy weight is suspended at the other end. The vibrating string is placed between the two magnets.

[0017] Furthermore, neodymium iron boron magnets are used.

[0018] Furthermore, in step S1, the constant temperature and pressure state means that after vacuuming, the pressure inside the device drops below 10 Pa, and the temperature is controlled to be within ±5 mK of the set value.

[0019] Furthermore, in step S2, the calibration is performed three times, and the average value is taken after the three calibrations to obtain the volume of the pressure chamber and pipeline.

[0020] Furthermore, in step S3, the lubricating oil filled into the pressure chamber is just enough to cover the top of the tungsten wire of the vibrating string.

[0021] Furthermore, in step S3, when the temperature fluctuation remains within ±5mK and the pressure fluctuation is within ±2kPa within 30 minutes, the refrigerant dissolves in the lubricating oil.

[0022] Furthermore, in step S5, the liquid level of the refrigerant and lubricating oil mixture submerges above the vibrating string.

[0023] Furthermore, in step S6, the solubility of the refrigerant in the lubricating oil is calculated using the following formula:

[0024]

[0025] In the formula, w represents the solubility of the refrigerant in the lubricating oil; m oilV represents the total mass of the lubricating oil filling the experimental chamber. mix ρ is the volume of the liquid mixture inside the experimental chamber; mix This represents the density of the liquid mixture within the experimental chamber.

[0026] Furthermore, the volume of the liquid mixture within the experimental chamber is calculated using the following formula:

[0027]

[0028] In the formula, m R The total mass of refrigerant charged into the experimental chamber; ρ R V0 represents the gaseous density of the refrigerant under experimental conditions; V0 is the total volume of the calibrated experimental chamber and piping.

[0029] Compared with existing technologies, the present invention has the following advantages:

[0030] This invention employs a vibrating string device, allowing a single device to measure all four thermophysical properties, overcoming the limitation of most current devices that can only measure one thermophysical property. This simplifies the measurement steps and optimizes the experimental process. The method for simultaneously measuring multiple thermophysical properties allows for the acquisition of density, viscosity, saturated vapor pressure, and solubility of a refrigerant-lubricating oil mixture with a single sample filling, saving reagent usage. The simple and quick operation facilitates application in practical production, daily life, and teaching. Furthermore, the method can utilize cyclic filling, progressing from a low to a high mixture ratio, ensuring that the mass of the lubricating oil added in the first filling remains constant while only the mass of the refrigerant is changed. This method is more conducive to exploring the changing patterns of refrigerant solubility in the lubricating oil.

[0031] Furthermore, the lubricating oil should just cover the tip of the tungsten wire of the vibrating string. Too much lubricating oil will affect the dissolution of the refrigerant, while too little lubricating oil will not cover the tungsten wire, affecting the measurement accuracy.

[0032] Furthermore, by ensuring that the refrigerant and lubricating oil completely submerge the vibrating string, the accuracy of the obtained density data is guaranteed.

[0033] Furthermore, the formula for calculating solubility is simple, involving only readily available physical quantities such as density and mass measured by the same set of equipment, thus improving the accuracy of the calculation results. Attached Figure Description

[0034] Figure 1 This is a simplified structural diagram of the device, showing only the main structure and omitting details and external instruments.

[0035] Figure 2 A flowchart of the method for simultaneously measuring multiple thermophysical properties of a refrigerant / lubricating oil mixture according to the present invention;

[0036] In the diagram, 1 is the sample filling port for lubricating oil and refrigerant, 2 is the pressure sensor, 3 is the lock-in amplifier, 4 is the temperature sensor, 5 is the stainless steel O-ring seal, 6 is the flange, 7 is the constant temperature bath drain port, 8 is the constant temperature bath chamber, 9 is the constant temperature bath inlet, 10 is the sample discharge port, 11 is the aluminum alloy weight, 12 is the vibrating string, 13 is the pressure chamber, 14 is the magnet, 15 is the vibrating string clamp, and 16 is the magnet holder. Detailed Implementation

[0037] To facilitate understanding of the present invention, a more complete description will be given below with reference to the accompanying drawings. Preferred embodiments of the invention are shown in the drawings. However, the invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a thorough and complete understanding of the disclosure of the invention.

[0038] Furthermore, elements in this invention are referred to as being "fixed to" or "set on" another element, which may be directly on the other element or may also include an intervening element. When an element is considered to be "connected" to another element, it may be directly connected to the other element or may also include an intervening element. The terms "vertical," "horizontal," "left," "right," and similar expressions used herein are for illustrative purposes only and do not represent the only possible implementations.

[0039] See Figure 1 The single-ended vibrating string device used in this invention includes a sample filling port 1 for lubricating oil and refrigerant, a pressure sensor 2, a lock-in amplifier 3, a temperature sensor 4, a stainless steel O-ring seal 5, a flange 6, a constant temperature bath drain port 7, a constant temperature bath chamber 8, a constant temperature bath inlet 9, a sample discharge port 10, an aluminum alloy weight 11, a vibrating string 12, a pressure chamber 13, a magnet 14, a vibrating string clamp 15, and a magnet frame 16; wherein the magnet 14 is a neodymium iron boron magnet.

[0040] The constant temperature bath chamber 8 is provided with a constant temperature bath drain port 7 at the top and a constant temperature bath inlet port 9 at the bottom. A pressure chamber 13 is provided inside the constant temperature bath chamber 8. A sample discharge port 10 is provided at the bottom of the pressure chamber 13 and a flange 6 is provided at the top. A stainless steel O-ring seal 5 is provided on the flange 6. The sample filling port 1 is connected to the pressure chamber 13. A pressure sensor 2, a lock-in amplifier 3, and a temperature sensor 4 are inserted into the pressure chamber 13. A magnet frame 16 is provided at the top of the pressure chamber 13. A vibration string clamp 15 is provided on the magnet frame 16. The vibration string clamp 15 and two magnets 14 are provided on the magnet frame 16. One end of the vibration string 12 is fixed to the vibration string clamp 15, and the other end is suspended by an aluminum alloy weight 11. The vibration string 12 is placed between the two magnets 14.

[0041] See Figure 2This invention discloses a method for simultaneously measuring multiple thermophysical properties of a refrigerant / lubricating oil mixture. The method measures density and viscosity using the buoyancy of a weight in the test substance and the principle of a vibrating string, and calculates the solubility of the refrigerant in the lubricating oil using a formula. The operation steps are as follows:

[0042] Step S1: Evacuate the vibrating string device, control the pressure and temperature, and start the experiment after achieving constant temperature and pressure.

[0043] Step S2: Calibrate the volume of the cavity and pipeline of the vibrating string device to obtain the volume of the cavity and pipeline;

[0044] Step S3: First, add a certain amount of lubricating oil, then add a certain amount of refrigerant according to the specified ratio, so that the refrigerant dissolves in the lubricating oil.

[0045] Step S4: After the temperature and pressure of the system have stabilized again, the density and viscosity of the mixture at that temperature and pressure are measured using the vibrating string method.

[0046] Step S5: In the current state, since the refrigerant has been fully dissolved in the lubricating oil, the space between the liquid surface of the mixture and the top of the pressure vessel is still filled with gaseous refrigerant. Therefore, the pressure measured by the pressure sensor at this time is the saturated vapor pressure of the refrigerant and lubricating oil mixture.

[0047] Step S6: Based on the measured physical quantities (volume of cavity and pipeline, refrigerant mass, lubricating oil mass and density of mixture), calculate the solubility of refrigerant in lubricating oil at this temperature and pressure.

[0048] Step S7: After measuring all thermophysical properties under this ratio, continue filling the sample using the cyclic filling method to reach the next ratio, and then repeat the above steps to continue the measurement.

[0049] Specifically, in step S1, the constant temperature and pressure state means that after vacuuming, the pressure inside the device is reduced to below 10 Pa, and the temperature is controlled to be within ±5 mK of the difference from the given temperature.

[0050] Specifically, in step S2, to ensure the accuracy of the calibration, the average value is taken after three calibrations to obtain the volume V0 of the pressure chamber and pipeline.

[0051] Specifically, in step S3, the mass of lubricating oil injected into the pressure chamber is m. oil It is essential to ensure that the lubricating oil just covers the tip of the tungsten wire of the vibrating string. Too much lubricating oil will affect the dissolution of the refrigerant, while too little lubricating oil will not cover the tungsten wire, thus affecting the measurement accuracy.

[0052] Specifically, in step S3, the mass m of refrigerant added after the lubricating oil is added. RThe mass difference of the filling vessel before and after filling can be obtained by weighing it with a precision balance. When the mixture does not cover the vibrating tungsten wire, a part of the gaseous refrigerant is still left on the liquid surface of the mixture and the top of the pressure chamber. In order to ensure that the refrigerant is completely dissolved in the lubricating oil, the filling vessel can be removed when the temperature fluctuation of the system is kept within ±5mK and the pressure fluctuation is within ±2kPa within 30 minutes.

[0053] Specifically, in step S4, the density and viscosity of the refrigerant and lubricating oil mixture can be obtained using the vibrating wire method. The density measurement principle is as follows: one end of a metal wire is fixed, and a weight is suspended at the other end to keep it taut. The entire device is immersed in the fluid to be measured. Due to the buoyancy of the fluid on the weight, the tension force on the metal wire changes accordingly, which in turn has a significant impact on the resonant frequency of the metal wire. The density ρ of the mixture to be measured can be obtained by measuring the frequency. mix The principle of viscosity measurement is as follows: the fluid around the metal wire will dampen the vibration of the wire. By measuring the vibration of the wire, the viscosity of the fluid can be measured according to the working equation of the metal wire vibration.

[0054] Specifically, in step S5, after the refrigerant has fully dissolved in the lubricating oil, it is necessary to ensure that the liquid level of the mixture still does not exceed the vibrating string;

[0055] Specifically, in step S6, the following formula is used:

[0056]

[0057] In the formula, w represents the solubility of the refrigerant in the lubricating oil; V mix ρ is the volume of the liquid mixture inside the experimental chamber; mix The density of the liquid mixture within the experimental chamber is obtained from step S4; m R The total mass of refrigerant charged into the experimental chamber is obtained from step S3; m oil The total mass of lubricating oil filled into the experimental chamber is obtained from step S3; ρ R V0 is the gaseous density of the refrigerant under experimental conditions. It can be calculated based on the refrigerant's equation of state under known temperature and pressure conditions. V0 is the total volume of the calibrated experimental chamber and pipelines, obtained from step S2.

[0058] Specifically, in step S6, after the temperature and pressure stabilize (temperature fluctuations are maintained within ±5 mK, and pressure fluctuations within ±2 kPa), the mixture density ρ obtained from the above formulas (1) and (2) and the measurement in step S4 is... mix The mass fraction of the refrigerant at that temperature, i.e., its solubility, can be calculated.

[0059] Specifically, in step S7, after the density, viscosity, saturated vapor pressure and solubility of a set of refrigerant lubricating oils are measured, the cyclic filling method is used to start the experiment from the refrigerant ratio with a low mass fraction in the lubricating oil. After the experiment of a set of ratios is completed, the mass of refrigerant required to achieve the next ratio is calculated, and the refrigerant is filled into the device from the filling port to achieve the next ratio.

[0060] This invention allows for the simultaneous measurement of multiple physical properties such as density, viscosity, saturated vapor pressure, and solubility without repeated sample filling. This simplifies the measurement process, saves on sample usage, facilitates the rapid acquisition of experimental data for the desired physical properties, and improves measurement efficiency.

[0061] In this invention, only m needs to be measured. R m oil The solubility of refrigerant in lubricating oil can be calculated using physical quantities such as V0 according to the formula. The required physical quantities are small and the experimental operation is simple.

[0062] Example 1: Solubility measurement of R134a in lubricating oil POE VG68

[0063] See Figure 1 The vibrating string device is evacuated, and the pressure and temperature are controlled to achieve constant temperature and pressure. The specific process is as follows: turn on the lock-in amplifier 3, connect the vacuum pump to the sample discharge port 10, and evacuate the pressure in the pressure chamber to a vacuum (below 10Pa); connect the liquid outlet of the constant temperature bath to the liquid inlet 9 of the constant temperature bath, connect the liquid inlet of the constant temperature bath to the liquid outlet 7 of the constant temperature bath, set the temperature, connect the pressure sensor 2 to the temperature sensor 4 and the computer, and start the experiment after the temperature change curve stabilizes (the temperature change is within ±5mK).

[0064] Calibration process: The volume of the vibrating string device cavity and pipeline is calibrated. The specific process is as follows: The total volume of the pressure cavity and external pipeline of the calibration device is calibrated using R134a. A certain amount of R134a is charged at a temperature of 298.15K. After the temperature and pressure in the cavity stabilize, the temperature and pressure values ​​are recorded. The density of R134a at this time is calculated according to the state equation of R134a. The ratio of the mass of the charged refrigerant to its density is the total volume of the pressure cavity and the upper pipeline. This step is repeated three times, and the average of the three calculation results is taken as the final result V0.

[0065] To ensure the accuracy of the calibration, the average value was taken after three calibrations.

[0066] Lubricating oil collection: Weigh the beaker and the mass of the lubricating oil, m1, and then fill the pressure chamber through the sample filling port 1. Note that the flow rate of the valve should be adjusted to allow the lubricating oil to be slowly drawn in. After filling, weigh the beaker and the remaining lubricating oil, m2, and subtract the two to calculate the mass m of the lubricating oil drawn into the chamber. oil The mass of lubricating oil filled into the pressure chamber is m.oil It is essential to ensure that the lubricating oil just covers the tip of the tungsten wire of the vibrating string. Too much lubricating oil will affect the dissolution of the refrigerant, while too little lubricating oil will not cover the tungsten wire, thus affecting the measurement accuracy.

[0067] Refrigerant Collection: Calculate the required amount of refrigerant based on the actual amount of lubricating oil charged. Collect the required refrigerant in the injection tank and weigh the total mass of the injection tank and refrigerant at this point, m3. Connect the injection tank to the No. 1 injection port and open the valve to inject the sample. Determine the injection volume and time based on the system pressure. Remove the injection tank and weigh it to obtain its mass m4. Subtract the mass m4 from the mass m5 to obtain the total mass m of refrigerant actually charged into the experimental chamber. R To ensure complete dissolution of the refrigerant and lubricating oil, the temperature should be raised to above 323.15K after sample filling and maintained for at least three hours.

[0068] After the sample filling was completed, the density and viscosity of the mixture were measured using the vibrating string method to obtain the density ρ of the refrigerant and lubricating oil mixture. mix And read the reading of pressure sensor 2 at this time, which is the saturated vapor pressure of the mixture;

[0069] Based on the measured physical quantities, use the following formula:

[0070]

[0071] In the formula, w represents the solubility of the refrigerant in the lubricating oil; V mix ρ is the volume of the liquid mixture inside the experimental chamber; mix The density of the liquid mixture within the experimental chamber; m R The total mass of the refrigerant charged into the experimental chamber; m oil ρ is the total mass of the lubricating oil filled into the experimental chamber. R Let V be the gaseous density of the refrigerant under experimental conditions. Based on the refrigerant's equation of state, under known temperature and pressure conditions, V0 can be calculated. V0 is the total volume of the calibrated experimental chamber and pipelines. From this, the solubility of the refrigerant in the lubricating oil at a temperature of 323.15 K can be calculated.

[0072] After the temperature measurement is completed, adjust the temperature setting of the constant temperature bath, and after the temperature stabilizes, continue to measure the density, viscosity, saturated vapor pressure of the refrigerant and lubricating oil mixture and the solubility of the refrigerant in the lubricating oil at the new temperature.

[0073] After all temperature points for this formulation have been measured, the refrigerant mass required to achieve the new formulation is calculated using the cyclic sampling method. The steps following refrigerant collection are repeated, and the experimental measurements are continued.

[0074] Following the experimental method described above, the solubility, saturated vapor pressure, density, and viscosity of R134a in POE VG68 were measured under temperature ranges of 298.15–393.15 K and pressure ranges of 0.1–4.4 MPa. The experimental results are shown in Table 1.

[0075] Table 1. Experimental data on the solubility w, saturated vapor pressure p, density ρ, and viscosity η of R134a+POE VG68

[0076]

[0077] Table 1 shows the relationship between solubility and temperature and pressure: as temperature increases, the solubility of R134a in POEVG68 gradually decreases. Simultaneously, as pressure increases, solubility also increases. This conforms to the general law of solubility: the higher the temperature, the lower the solubility; the greater the pressure, the higher the solubility.

[0078] Relationship between saturated vapor pressure and temperature: As the temperature increases, the saturated vapor pressure of the R134a+POEVG68 mixture gradually increases.

[0079] The relationship between density and temperature and pressure: The density of the mixture decreases slightly as the temperature increases, which may be due to the increase in intermolecular distance caused by the increase in temperature.

[0080] The relationship between viscosity and temperature and pressure: As temperature increases, the viscosity of a mixture gradually decreases. This is because increased temperature increases the thermal motion of molecules, weakening the intermolecular interactions and thus reducing viscosity. Meanwhile, pressure has little effect on viscosity.

[0081] The above description is only of the preferred embodiment of the present invention and should not be construed as limiting the scope of the claims. The present invention is not limited to the above embodiments, and variations in its specific structure are permitted. All variations made within the scope of the independent claims of the present invention are also within the scope of protection of the present invention.

[0082] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

Claims

1. A method for simultaneously measuring multiple thermophysical properties of a refrigerant / lubricating oil mixture, characterized in that, Includes the following steps: Step S1: Evacuate the vibrating string device, control the pressure and temperature to the set values, and achieve a constant temperature and pressure state; the vibrating string device includes a lubricating oil and refrigerant filling port (1), a pressure sensor (2), a lock-in amplifier (3), a temperature sensor (4), a flange (6), a constant temperature bath drain port (7), a constant temperature bath chamber (8), a constant temperature bath inlet (9), a sample discharge port (10), an aluminum alloy weight (11), a vibrating string (12), a pressure chamber (13), a magnet (14), a vibrating string clamp (15), and a magnet holder (16); the constant temperature bath chamber (8) is provided with a constant temperature bath drain port (7) at the top and a constant temperature bath inlet port (9) at the bottom. A pressure chamber (13) is set inside the constant temperature bath chamber (8). A sample outlet (10) is set at the bottom of the pressure chamber (13). A flange (6) is set at the top of the pressure chamber (13). The sample filling port (1) is connected to the pressure chamber (13). A pressure sensor (2), a lock-in amplifier (3), and a temperature sensor (4) are inserted inside the pressure chamber (13). A magnet frame (16) is set at the top of the pressure chamber (13). A vibration string clamp (15) and two magnets (14) are set on the magnet frame (16). One end of the vibration string (12) is fixed to the vibration string clamp (15), and the other end is suspended by an aluminum alloy weight (11). The vibration string (12) is placed between the two magnets (14). Step S2: Calibrate the volume of the cavity and pipeline of the vibrating string device to obtain the volume of the cavity and pipeline; Step S3: Fill the vibrating string device with lubricating oil and refrigerant; Step S4: After the temperature and pressure have stabilized again, the density and viscosity of the mixture at the test temperature and pressure are measured using the vibrating string method. Step S5: Measure the pressure under the current condition. The pressure is the saturated vapor pressure of the refrigerant and lubricating oil mixture. Step S6: Based on the volume of the cavity and pipeline, the mass of the refrigerant, the mass of the lubricating oil, and the density of the mixture, calculate the solubility of the refrigerant in the lubricating oil at the test temperature and pressure; the solubility is calculated using the following formula: （1） In the formula, w This refers to the solubility of the refrigerant in lubricating oil. m oil The total mass of the lubricating oil filled into the experimental chamber; V mix This represents the volume of the liquid mixture within the experimental chamber. ρ mix The density of the liquid mixture inside the experimental chamber; The volume of the liquid mixture inside the experimental chamber is calculated using the following formula: （2） In the formula, m R This refers to the total mass of the refrigerant that was filled into the experimental chamber. ρ R The density of the refrigerant in the gaseous phase under experimental conditions; V 0 represents the total volume of the calibrated experimental chamber and pipelines.

2. The method for simultaneously measuring multiple thermophysical properties of a refrigerant / lubricating oil mixture according to claim 1, characterized in that, The magnet (14) is a neodymium iron boron magnet.

3. The method for simultaneously measuring multiple thermophysical properties of a refrigerant / lubricating oil mixture according to claim 1, characterized in that, In step S1, the constant temperature and pressure state means that after vacuuming, the pressure inside the device drops below 10 Pa, and the temperature is controlled to be within ±5 mK of the set value.

4. The method for simultaneously measuring multiple thermophysical properties of a refrigerant / lubricating oil mixture according to claim 1, characterized in that, In step S2, the calibration is performed three times, and the average value is taken after the three calibrations to obtain the volume of the pressure chamber and pipeline.

5. The method for simultaneously measuring multiple thermophysical properties of a refrigerant / lubricating oil mixture according to claim 1, characterized in that, In step S3, the lubricating oil filled into the pressure chamber is just enough to cover the top of the tungsten wire of the vibrating string.

6. The method for simultaneously measuring multiple thermophysical properties of a refrigerant / lubricating oil mixture according to claim 1, characterized in that, In step S3, if the temperature fluctuation remains within ±5 mK and the pressure fluctuation is within ±2 kPa within 30 minutes, the refrigerant will dissolve in the lubricating oil.

7. The method for simultaneously measuring multiple thermophysical properties of a refrigerant / lubricating oil mixture according to claim 1, characterized in that, In step S5, the liquid level of the refrigerant and lubricating oil mixture submerges above the vibrating string.

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