Method for simultaneously measuring multiple thermophysical properties of refrigerant / lubricating oil mixture

Abstract

The invention discloses a method for simultaneously measuring various thermophysical properties of a refrigerant / lubricating oil mixture, which comprises the following steps of: vacuumizing a vibrating wire device, controlling the pressure and the temperature to be a set value, and achieving a constant-temperature and constant-pressure state; calibrating the volume of the cavity and the volume of the pipeline of the vibrating wire device to obtain the volume of the cavity and the volume of the pipeline; lubricating oil and a refrigerant are filled into the vibrating wire device; measuring the density and viscosity of the mixture under the test temperature and pressure by using a vibrating string method; measuring the pressure in the current state, wherein the pressure is the saturated vapor pressure of the refrigerant and lubricating oil mixture; and calculating the solubility of the refrigerant in the lubricating oil under the test temperature and pressure according to the obtained data. The invention provides a simple method for simultaneously measuring various physical properties such as density, viscosity, saturated vapor pressure, solubility and the like without repeatedly filling a sample, so that the previous measurement steps are simplified, the application amount of the sample is saved, the experimental data of the required physical properties can be quickly obtained, and the measurement efficiency is improved.

Description

Technical Field

[0001] The present invention relates to the field of fluid thermophysical property measurement, and particularly to a method for simultaneously measuring multiple thermophysical properties of a refrigerant / lubricant mixture, which can be used for the actual teaching of relevant courses on thermophysical property testing, and can also be used for the measurement of relevant physical properties in actual production, life and scientific research. Background Art

[0002] Density, viscosity, saturation pressure, and solubility are all very important thermophysical properties and are also parameters that need to be obtained in the fields of energy science and chemical engineering. These physical properties of different substances are all different and will change with the change of temperature. During the operation of a compression refrigeration system, the refrigerant inevitably comes into contact with and mixes with the lubricating oil and enters the system cycle together. The participation of the lubricating oil has a very important impact on the performance of the compressor, the flow and heat transfer in the heat exchanger, and the throttling process in the capillary tube. Since the thermophysical properties of the refrigerant and the lubricating oil are very different, after the circulating working fluid changes from a pure refrigerant to a refrigerant / lubricant mixture, the thermophysical properties of the mixture will change drastically, thus affecting the cycle performance of the refrigeration system.

[0003] The influence of the lubricating oil entering the heat exchange equipment with the refrigerant on the refrigeration system is related to the mutual solubility of the refrigerant and the lubricating oil. If the mutual solubility between the two is poor, the lubricating oil in the compressor gradually decreases, resulting in oil shortage in the compressor and a decline in lubrication and cooling effects; too much lubricating oil accumulates in the evaporator and condenser, blocking the pipeline and reducing its heat transfer performance. When the solubility is relatively large, the "pooling" phenomenon will not occur in the heat exchanger, which is beneficial to the return of oil to the compressor. However, too high solubility will cause the viscosity of the lubricating oil to decrease, and it cannot play a sufficient lubricating role for the bearings and moving parts of the compressor. In addition, the mixing of the lubricating oil and the refrigerant will cause the density of the refrigerant to decrease, and the flow rate of the refrigerant entering the compressor interior to decrease, thereby reducing the refrigeration efficiency. Therefore, determining the physical properties after the mixing of the refrigerant and the lubricating oil, especially the key factors such as solubility, saturated vapor pressure, density and viscosity properties that affect the performance of the compressor, is very crucial for improving the cycle efficiency and service life of the refrigeration system.

[0004] There are many current studies on the solubility, density, and viscosity measurements of refrigerant and lubricant mixtures. In terms of solubility, Jia et al. measured the solubility of R32 in POE, PVE, and PAG oils using the equal-volume saturation method; Morais et al. measured the solubility of R143a, R125, and R32 in VG32 at temperatures from 248.15 K to 348.15 K by the weighing method. In terms of density and viscosity studies, Cavestri et al. measured the solubility, density, and viscosity of the R134a and VG32 mixture using an oscillating body viscometer; Tomoaki et al. measured the density and viscosity of the R134a / POE VG32 and R134a / PAG VG32 mixtures at relatively low concentrations (refrigerant mass fraction less than 15%) in the temperature range of 278.15 K to 288.15 K using a glass tube densitometer and a vibrating cup viscometer, respectively.

[0005] From the above studies, it can be found that although there are many studies on the physical properties of refrigerant and lubricant mixtures, 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 it requires repeated sample filling, resulting in a large consumption of reagents. There is a lack of a convenient method to obtain multiple thermophysical properties using a single set of devices. Summary of the Invention

[0006] In order to solve the technical problems of the complex process of measuring the physical properties of mixtures and the large consumption of reagents in the prior art, the purpose of the present invention is to provide a method for simultaneously measuring multiple thermophysical properties of refrigerant / lubricant mixtures. This method can simultaneously measure multiple physical properties such as density, viscosity, saturation vapor pressure, and solubility without repeated sample filling, simplifies the measurement steps, saves the application amount of samples, is conducive to quickly obtaining the experimental data of the required physical properties, and improves the measurement efficiency.

[0007] To achieve the above object, the present invention adopts the following technical solutions:

[0008] A method for simultaneously measuring multiple thermophysical properties of refrigerant / lubricant mixtures, comprising the following steps:

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

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

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

[0012] Step S4: After the temperature and pressure are stabilized again, use the vibrating string method to measure the density and viscosity of the mixture at the test temperature and pressure;

[0013] Step S5: Measure the pressure in the current state, where the pressure is the saturated vapor pressure of the refrigerant-lubricant mixture.

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

[0015] Furthermore, in Step S1, the vibrating string device includes a sampling port for the lubricant and refrigerant, a pressure sensor, a lock-in amplifier, a temperature sensor, a flange, a constant-temperature bath drain port, a constant-temperature bath cavity, a constant-temperature bath inlet port, a sampling port, an aluminum alloy weight, a vibrating string, a pressure cavity, a magnet, a vibrating string clamp, and a magnet holder.

[0016] The upper part of the constant-temperature bath cavity is provided with a constant-temperature bath drain port, the lower part is provided with a constant-temperature bath inlet port, a pressure cavity is arranged inside the constant-temperature bath cavity, a sampling port is arranged at the bottom of the pressure cavity, a flange is arranged at the top of the pressure cavity, the sampling port is communicated with the pressure cavity, and a pressure sensor, a lock-in amplifier, and a temperature sensor are inserted into the pressure cavity; a magnet holder is arranged at the top inside the pressure cavity, a vibrating string clamp and two magnets are arranged on the magnet holder, one end of the vibrating string is fixed to the vibrating string clamp, the other end is suspended with an aluminum alloy weight, and the vibrating string is placed between the two magnets.

[0017] Furthermore, the magnet is a neodymium iron boron magnet.

[0018] Furthermore, in Step S1, the constant temperature and pressure state means that after evacuation, the pressure inside the device drops below 10 Pa, and the temperature is controlled 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 three calibrations to obtain the volume of the pressure cavity and the pipeline.

[0020] Furthermore, in Step S3, the lubricant filled into the pressure cavity just covers the top end of the vibrating string tungsten wire.

[0021] Furthermore, in Step S3, when the temperature fluctuation remains within ±5 mK within 30 min and the pressure fluctuation is within ±2 kPa, the refrigerant is dissolved in the lubricant.

[0022] Furthermore, in Step S5, the liquid level of the refrigerant-lubricant mixture covers the vibrating string.

[0023] Furthermore, in Step S6, the solubility of the refrigerant in the lubricant is calculated by the following formula:

[0024]

[0025] In the formula, w is the solubility of the refrigerant in the lubricant; m oilis the total mass of the lubricating oil filled into the experimental chamber; V mix is the volume of the liquid-phase mixture in the experimental chamber; ρ mix is the density of the liquid-phase mixture in the experimental chamber.

[0026] Furthermore, the volume of the liquid-phase mixture in the experimental chamber is calculated by the following formula:

[0027]

[0028] In the formula, m R is the total mass of the refrigerant filled into the experimental chamber; ρ R is the density of the gaseous phase of the refrigerant under experimental conditions; V 0 is the total volume of the calibrated experimental chamber and pipeline.

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

[0030] The present invention adopts a vibrating string device, and one set of device can complete the measurement of the above four thermophysical properties, solving the limitation that most current devices can only measure one thermophysical property, simplifying the measurement steps, and optimizing the experimental process; the method for simultaneously measuring multiple thermophysical properties of the present invention can obtain the density, viscosity, saturation vapor pressure, solubility, etc. of the refrigerant-lubricant mixture with one sample filling, saving the usage amount of reagents, being simple and fast to operate, and being conducive to application in actual production, life and teaching; the method of the present invention can also adopt the method of cyclic sample filling, advancing the experiment from low ratio to high ratio, ensuring that the mass of the lubricating oil filled for the first time remains unchanged, only changing the mass of the refrigerant filled, and being more conducive to exploring the change law of the solubility of the refrigerant in the lubricating oil.

[0031] Furthermore, the lubricating oil just covers the top of the vibrating string tungsten wire. Excessive lubricating oil will affect the dissolution of the refrigerant, while too little lubricating oil cannot cover the tungsten wire, affecting the measurement accuracy.

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

[0033] Furthermore, the calculation formula for solubility is simple, only involving physical quantities such as density and mass measured by the same set of device and being easy to obtain, improving the accuracy of the calculation result. Brief Description of the Drawings

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

[0035] Figure 2 is a flow chart of the method for simultaneously measuring multiple thermophysical properties of the refrigerant / lubricant mixture of the present invention;

[0036] In the figure, 1 is the sampling port for lubricating oil and refrigerant, 2 is the pressure sensor, 3 is the phase-locked amplifier, 4 is the temperature sensor, 5 is the stainless steel O-ring, 6 is the flange, 7 is the drain port of the thermostatic bath, 8 is the thermostatic bath cavity, 9 is the inlet port of the thermostatic bath, 10 is the sampling outlet, 11 is the aluminum alloy weight, 12 is the vibrating string, 13 is the pressure cavity, 14 is the magnet, 15 is the vibrating string clamp, and 16 is the magnet holder. Specific embodiments

[0037] To facilitate the understanding of the present invention, the present invention will be described more comprehensively below with reference to the relevant drawings. The preferred embodiments of the present invention are shown in the drawings. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, these embodiments are provided to make the disclosure of the present invention more thorough and comprehensive.

[0038] In addition, an element in the present invention is referred to as "fixed to" or "disposed on" another element, and it can be directly on the other element or there can also be an intermediate element. When an element is considered to be "connected" to another element, it can be directly connected to the other element or there may be an intermediate element at the same time. The terms "vertical", "horizontal", "left", "right" and similar expressions used herein are only for the purpose of illustration and do not represent the only embodiments.

[0039] See Figure 1 , the single-ended vibrating string device adopted in the present invention includes a sampling port 1 for lubricating oil and refrigerant, a pressure sensor 2, a phase-locked amplifier 3, a temperature sensor 4, a stainless steel O-ring 5, a flange 6, a drain port 7 of the thermostatic bath, a thermostatic bath cavity 8, an inlet port 9 of the thermostatic bath, a sampling outlet 10, an aluminum alloy weight 11, a vibrating string 12, a pressure cavity 13, a magnet 14, a vibrating string clamp 15 and a magnet holder 16; wherein the magnet 14 is a neodymium iron boron magnet.

[0040] A drain port 7 of the thermostatic bath is provided at the upper part of the thermostatic bath cavity 8, an inlet port 9 of the thermostatic bath is provided at the lower part, a pressure cavity 13 is provided inside the thermostatic bath cavity 8, a sampling outlet 10 is provided at the bottom of the pressure cavity 13, a flange 6 is provided at the top, a stainless steel O-ring 5 is provided on the flange 6, the sampling port 1 is communicated with the pressure cavity 13, and a pressure sensor 2, a phase-locked amplifier 3 and a temperature sensor 4 are inserted into the pressure cavity 13. A magnet holder 16 is provided at the top inside the pressure cavity 13, a vibrating string clamp 15 is provided on the magnet holder 16, a vibrating string clamp 15 and two magnets 14 are provided on the magnet holder 16, one end of the vibrating string 12 is fixed to the vibrating string clamp 15, the other end is suspended with an aluminum alloy weight 11, and the vibrating string 12 is placed between the two magnets 14.

[0041] See Figure 2, a method for simultaneously measuring multiple thermophysical properties of a refrigerant / lubricant mixture, measures density and viscosity through the buoyancy of a heavy object in the substance to be measured and the principle of a vibrating string, and calculates the solubility of the refrigerant in the lubricant through 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 reaching a 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, fill in a certain mass of lubricant, and then fill in a certain amount of refrigerant with a determined mass according to the ratio to dissolve the refrigerant in the lubricant.

[0045] Step S4: After the temperature and pressure of the system are stable again, use the vibrating string method to measure the density and viscosity of the mixture at this temperature and pressure.

[0046] Step S5: At the current state, since the refrigerant has been fully dissolved in the lubricant, the gas-phase refrigerant still fills the space between the liquid level of the mixture and the top of the pressure vessel. Therefore, the pressure measured by the pressure sensor at this time is the saturated vapor pressure of the refrigerant-lubricant mixture.

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

[0048] Step S7: After measuring the thermophysical properties of each ratio, use the cyclic sampling method to continue sampling until the next ratio is reached, and then repeat the above steps to continue the measurement.

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

[0050] Specifically, in step S2, to ensure the accuracy of the calibration, take the average value after three calibrations to obtain the volume V of the pressure cavity and pipeline. 0 ;

[0051] Specifically, in step S3, the mass of the lubricant filled into the pressure cavity is m. oil , and it must be ensured that it just covers the top of the vibrating string tungsten wire. Excessive lubricant will affect the dissolution of the refrigerant, and too little lubricant will not cover the tungsten wire, affecting the measurement accuracy.

[0052] Specifically, in step S3, the mass m of the refrigerant filled after filling the lubricant. R, it can be obtained by weighing the mass difference of the filling tank before and after filling with a precision balance. When the mixture submerges the vibrating wire tungsten wire, there is still a part of gaseous refrigerant left between the liquid level of the mixture and the top of the pressure chamber. To ensure that the refrigerant is completely dissolved in the lubricating oil, the filling tank can be removed only when the temperature fluctuation of the system remains within ±5 mK and the pressure fluctuation is within ±2 kPa within 30 minutes.

[0053] Specifically, in step S4, by using the vibrating wire method, the density and viscosity of the refrigerant-lubricating oil mixture can be obtained. The measurement principle of density is as follows: One end of the metal wire is fixed, and the other end is suspended with a heavy object to keep it in a tensioned state. The whole device is immersed in the fluid to be measured. Since the fluid exerts a buoyant force on the heavy object, the tension force on the metal wire will change accordingly, which will have a relatively obvious impact on the resonance frequency of the metal wire. By measuring the frequency, the density ρ of the mixture to be measured can be obtained. mix The measurement principle of viscosity is as follows: The fluid around the metal wire will have a damping effect on the vibration of the wire. By measuring the vibration of the wire, the measurement of the fluid viscosity can be realized according to the working equation of the metal wire vibration.

[0054] Specifically, in step S5, after the refrigerant is fully dissolved in the lubricating oil, it is necessary to ensure that the liquid level of the mixture still submerges the vibrating wire.

[0055] Specifically, in step S6, according to the following formula:

[0056]

[0057] In the formula, w is the solubility of the refrigerant in the lubricating oil; V mix is the volume of the liquid-phase mixture in the experimental cavity; ρ mix is the density of the liquid-phase mixture in the experimental cavity, obtained from step S4; m R is the total mass of the refrigerant filled into the experimental cavity, obtained from step S3; m oil is the total mass of the lubricating oil filled into the experimental cavity, obtained from step S3; ρ R is the density of the gaseous phase of the refrigerant under the experimental conditions, which can be calculated under the conditions of known temperature and pressure according to the state equation of the refrigerant; V 0 is the total volume of the calibrated experimental cavity and pipeline, obtained from step S2;

[0058] Specifically, in step S6, when the temperature and pressure are stable (the temperature fluctuation remains within ±5 mK and the pressure fluctuation is within ±2 kPa), from the above formulas (1) and (2) and the density ρ of the mixture measured in step S4 mix the mass fraction of the refrigerant at this temperature, that is, the solubility, can be calculated inversely.

[0059] Specifically, in step S7, after measuring the density, viscosity, saturation vapor pressure, and solubility of a group of refrigerant lubricants, the cyclic sampling method is adopted. Starting from the refrigerant ratio with a low mass fraction in the lubricant, after a group of ratio experiments are completed, the mass of the refrigerant required to reach the next ratio is calculated and filled into the device through the sampling port to reach the next ratio.

[0060] The present invention can measure multiple physical properties such as density, viscosity, saturation vapor pressure, and solubility simultaneously without repeated sampling, simplifies the measurement steps, saves the application amount of samples, is conducive to quickly obtaining experimental data of the required physical properties, and improves the measurement efficiency.

[0061] In the present invention, only the physical quantities m R , m oil , V 0 etc. need to be measured, and the solubility of the refrigerant in the lubricant can be obtained according to the formula. The required physical quantities are few and the experimental operation is simple.

[0062] Example 1: Measurement of the solubility of R134a in lubricant POE VG68

[0063] Refer to Figure 1 , evacuate the vibrating string device, control the pressure and temperature to reach constant temperature and constant 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 cavity to vacuum (below 10 Pa); 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 discharge port 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 is stable (the temperature change is within ±5 mK);

[0064] Calibration process: Calibrate the volume of the cavity and pipeline of the vibrating string device. The specific process is as follows: Use the R134a calibration device to calibrate the total volume of the pressure cavity and the external pipeline. At a temperature of 298.15 K, fill in a certain amount of R134a. After the temperature and pressure in the cavity are stable, record the temperature and pressure values at this time. Calculate the density of R134a at this time according to the state equation of R134a. The ratio of the mass of the filled refrigerant to the density is the total volume of the pressure cavity and the upper pipeline. Repeat this step three times, and take the average value of the three calculation results as the final result V 0 ;

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

[0066] Collection of lubricant: Weigh the mass m 1 of the beaker and the lubricant, and then fill it into the pressure cavity through the sampling port 1. Note that the flow rate of the valve should be adjusted to slowly suck in the lubricant. After the sampling is completed, weigh the total weight m 2 of the beaker and the remaining lubricant, subtract the two to calculate the mass m of the lubricating oil in the suction cavity oil ; the mass of the lubricating oil charged into the pressure cavity is m oil , it is necessary to ensure that the top of the vibrating string tungsten wire is just covered. Excessive lubricating oil will affect the dissolution of the refrigerant, and too little lubricating oil will not be able to cover the tungsten wire, affecting the measurement accuracy;

[0067] Collection of refrigerant: Calculate the required amount of refrigerant according to the actual amount of lubricating oil charged. Collect the required refrigerant in the sampling tank, and weigh the total mass m of the sampling tank and the refrigerant at this time 3 . Connect the sampling tank to the filling port 1 and then open the valve for sampling. Judge the sampling volume and time according to the system pressure. Remove the sampling tank and weigh it to get the mass m 4 , subtract the two to get the total mass m of the refrigerant actually charged into the experimental cavity R . To ensure the complete dissolution of the refrigerant and the lubricating oil, heat up to above 323.15K and keep it for at least three hours after sampling;

[0068] After sampling is completed, use the vibrating string method to measure the density and viscosity of the mixture, and obtain the density ρ of the refrigerant and lubricating oil mixture mix , and read the indication of the pressure sensor 2 at this time, which is the saturated vapor pressure of the mixture;

[0069] According to the measured physical quantities, use the following formula:

[0070]

[0071] In the formula, w is the solubility of the refrigerant in the lubricating oil; V mix is the volume of the liquid-phase mixture in the experimental cavity; ρ mix is the density of the liquid-phase mixture in the experimental cavity; m R is the total mass of the refrigerant charged into the experimental cavity; m oil is the total mass of the lubricating oil charged into the experimental cavity; ρ R is the gas-phase density of the refrigerant under the experimental conditions, which can be calculated according to the state equation of the refrigerant under the known temperature and pressure conditions; V 0 is the total volume of the calibrated experimental cavity and pipeline; from this, the solubility of the refrigerant in the lubricating oil at a temperature of 323.15K can be calculated;

[0072] After measuring this temperature, adjust the set temperature of the constant temperature bath. 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 measuring all temperature points of this ratio, the cyclic filling method is adopted to calculate the mass of refrigerant required to reach the new ratio, and the steps after refrigerant collection are repeated to continue the experimental measurement.

[0074] According to the above experimental method, the solubility, saturated vapor pressure, density and viscosity data of R134a in POE VG68 were measured under the conditions of temperature range 298.15 - 393.15K and pressure range 0.1 - 4.4MPa. The experimental results are shown in Table 1.

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

[0076]

[0077] It can be seen from Table 1 the relationships between solubility and temperature and pressure: as the temperature increases, the solubility of R134a in POE VG68 gradually decreases. At the same time, as the pressure increases, the solubility also increases. This conforms to the general dissolution rule, that is, the higher the temperature, the lower the solubility; the greater the pressure, the higher the solubility.

[0078] The relationship between saturated vapor pressure and temperature: as the temperature increases, the saturated vapor pressure of the R134a + POE VG68 mixture gradually increases.

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

[0080] The relationships between viscosity and temperature and pressure: as the temperature increases, the viscosity of the mixture gradually decreases. This is because the increase in temperature will increase the thermal motion of molecules, weaken the intermolecular interaction, and thus reduce the viscosity. At the same time, the influence of pressure on viscosity is not obvious.

[0081] The above only illustrates the best embodiments of the present invention, but it cannot be understood as a limitation to the claims. The present invention is not limited to the above embodiments, and its specific structure allows changes. Any changes made within the protection scope of the independent claims of the present invention are within the protection scope of the present invention.

[0082] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the technical field to which the present invention belongs. The terms used in the specification of the present invention herein are only for the purpose of describing specific embodiments, and are not intended to limit the present invention. The term "and / or" used herein includes any and all combinations of one or more of the related listed items.

Claims

1. A method for simultaneously measuring multiple thermophysical properties of a refrigerant / lubricant mixture, characterized in that: The following steps are involved: Step S1, evacuate the vibrating string device, control the pressure and temperature to set values, and achieve a constant temperature and pressure state; Step S2, calibrating the volume of the cavity and the pipeline of the vibrating string device to obtain the volume of the cavity and the pipeline; Step S3, filling lubricating oil and refrigerant into the vibrating string device; Step S4, after the temperature and pressure are stabilized again, the density and viscosity of the mixture under the test temperature and pressure are measured using the vibrating string method; Step S5, measuring the pressure in the current state, where the pressure is the saturated vapor pressure of the mixture of the refrigerant and the lubricating oil; Step S6: Calculate the solubility of the refrigerant in the lubricating oil at the test temperature and pressure according to the volume of the cavity and the pipeline, the mass of the refrigerant, the mass of the lubricating oil and the density of the mixture.

2. The method for simultaneously measuring multiple thermophysical properties of a refrigerant / lubricant mixture according to claim 1, characterized in that: In step S1, the vibrating string device includes a sample filling port (1) for lubricating oil and refrigerant, a pressure sensor (2), a phase-locked amplifier (3), a temperature sensor (4), a flange (6), a constant temperature bath discharge port (7), a constant temperature bath cavity (8), a constant temperature bath inlet (9), a sample discharge port (10), an aluminum alloy weight (11), a vibrating string (12), a pressure cavity (13), a magnet (14), a vibrating string clamp (15) and a magnet frame (16); The constant temperature bath cavity (8) is provided with a constant temperature bath discharge port (7) at the top and a constant temperature bath inlet port (9) at the bottom. A pressure cavity (13) is provided in the constant temperature bath cavity (8). A sample discharge port (10) is provided at the bottom of the pressure cavity (13). A flange (6) is provided at the top of the pressure cavity (13). The sample filling port (1) is connected to the pressure cavity (13). A pressure sensor (2), a phase-locked amplifier (3) and a temperature sensor (4) are inserted into the pressure cavity (13). A magnet frame (16) is provided at the top of the pressure cavity (13). A 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 an aluminum alloy weight (11) is hung at the other end. The vibration string (12) is placed between the two magnets (14).

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

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

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

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

7. The method for simultaneously measuring multiple thermophysical properties of a refrigerant / lubricant mixture according to claim 1, characterized in that: In step S3, when the temperature fluctuation is maintained at ±5 mK and the pressure fluctuation is maintained at ±2 kPa within 30 minutes, the refrigerant is dissolved in the lubricating oil.

8. The method for simultaneously measuring multiple thermophysical properties of a refrigerant / lubricant mixture according to claim 2, characterized in that: In step S5, the liquid level of the refrigerant and lubricating oil mixture is above the vibrating string.

9. The method for simultaneously measuring multiple thermophysical properties of a refrigerant / lubricant mixture according to claim 1, characterized in that: In step S6, the solubility of the refrigerant in the lubricating oil is calculated by the following formula: Where, w is the solubility of refrigerant in lubricating oil; m oil is the total mass of lubricating oil filled into the experimental cavity; V mix is the volume of the liquid mixture in the experimental chamber; ρ mix is the density of the liquid mixture in the experimental chamber.

10. The method for simultaneously measuring multiple thermophysical properties of a refrigerant / lubricant mixture according to claim 9, characterized in that: The volume of the liquid mixture in the experimental chamber is calculated by the following formula: In the formula, m R is the total mass of refrigerant charged into the experimental cavity; ρ R is the gas phase density of the refrigerant under experimental conditions; V0 is the total volume of the calibrated experimental cavity and pipeline.

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