A high-temperature saturated gas-liquid phase density measurement device and method

Abstract

The application discloses a high-temperature saturated gas-liquid phase density measuring device and method, which comprises a high-temperature temperature control system, a saturated gas phase density measuring cavity, a saturated liquid phase density measuring cavity, a temperature measuring system and a vacuum system. The experimental measuring cavity adopts a double-layer electric heating wire winding mode to realize accurate temperature control in a wide temperature range; the effective volumes of the gas phase cavity and the liquid phase cavity are calibrated by using standard substances respectively, and the saturated gas-liquid phase densities of the fluid to be measured are obtained by measuring the sample mass difference of the experimental measuring cavity before and after expansion. The application can realize accurate measurement of the saturated gas-liquid phase density under extremely harsh conditions, has the advantages of simple test method and good stability, and has a wide applicable temperature and pressure range, and can be used not only for high-temperature saturated gas-liquid phase density measurement of industrial electrolyte solutions, mixed fuels and lubricating oils and other fluids, but also for teaching of energy power related professional course experiments.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of thermophysical property measurement of fluid, and particularly relates to a high-temperature saturated gas-liquid phase density measuring device and method. BACKGROUND

[0002] Saturated gas-liquid phase density is one of the most important thermophysical properties of fluid working medium, and is also indispensable basic data for researching other thermophysical properties (kinetic viscosity, surface / interface tension, thermal conductivity coefficient, etc.) under the condition of gas-liquid phase equilibrium. The saturated gas-liquid phase density data has important applications in the fields of basic scientific research and industrial process design optimization. At present, reliable saturated gas-liquid phase density data mainly comes from experimental measurement. The experimental measurement methods mainly include magnetic suspension method, vibrating string method and vibrating tube method. For different test conditions of the fluid to be measured, the methods need to be reasonably selected according to the measurement accuracy and applicable range of each method. The basic principle of the magnetic suspension method is Archimedes' buoyancy law. The buoyancy force received by the object completely immersed in the fluid to be measured is equal to the weight of the object that displaces the fluid, and then the density of the liquid can be expressed as:

[0003]

[0004] Wherein: m s —mass of the float in vacuum / kg, m * s —mass of the float completely immersed in the fluid to be measured / kg, V s —volume of the float / m 3 .

[0005] The magnetic suspension method is to realize the accurate measurement of the mass of the float by using the interaction force generated by the magnetic material under non-contact condition, so as to avoid the direct contact between the sample to be measured and the external components, facilitate the sealing of the experimental device and have extremely high measurement accuracy. However, due to the demagnetization phenomenon of the magnetic force coupling system under high temperature condition, the overall measurement accuracy of the experimental system sharply decreases, and the saturated gas-liquid phase density measurement research under high temperature harsh condition cannot be realized. Moreover, the structure design, operation process and complexity of the experimental system further limit the popularization and use of the method.

[0006] The vibrating string method is to change the tension degree of the string by the buoyancy of the tension weight of the string in the fluid to be measured, so as to affect the resonance frequency of the string, and the saturated liquid density of the fluid to be measured can be obtained according to the measurement of the resonance frequency signal of the string and the iterative calculation of the working equation; the vibrating tube method is to inject the fluid to be measured into the experimental device, so that the saturated liquid phase of the fluid fills the working area of the vibrating tube, and the vibrating tube is approximated as a complete and independent vibrating system, the density of the fluid to be measured will cause the mass of the vibrating system to change, and then affect the resonance frequency of the vibrating system, and the saturated liquid density of the fluid to be measured can be obtained according to the measurement of the resonance frequency of the vibrating system and the calculation of the working equation. The two methods are also affected by the demagnetization problem of the magnet under high temperature conditions, so that the saturated gas-liquid density measurement under high temperature and harsh conditions cannot be realized.

[0007] In summary, the saturated gas-liquid density measurement method in the prior art cannot meet the fluid saturated gas-liquid density measurement under high temperature and extreme harsh conditions. SUMMARY

[0008] In order to solve the problems in the prior art, the present application provides a high temperature saturated gas-liquid density measurement device and method, which can realize saturated gas-liquid density measurement under high temperature and harsh conditions, and has simple experimental operation and high measurement precision.

[0009] In order to achieve the above purpose, the present application provides the following technical scheme:

[0010] A high temperature saturated gas-liquid density measurement device, comprising a high temperature temperature control system and a saturated gas-liquid density measurement system;

[0011] The high temperature temperature control system comprises a temperature controller, a temperature control platinum resistance thermometer, a heating wire and a constant temperature sleeve;

[0012] The platinum resistance thermometer is connected with the temperature controller and is arranged in the side wall of the constant temperature sleeve; the platinum resistance thermometer measures the temperature of the constant temperature sleeve in real time and feeds back to the temperature controller; the heating wire is arranged in the constant temperature sleeve, and the temperature controller controls the heating temperature of the heating wire;

[0013] The saturated gas-liquid density measurement system comprises a measurement cavity and a temperature measurement platinum resistance thermometer, and the measurement cavity comprises a saturated gas density measurement cavity and a saturated liquid density measurement cavity; the saturated gas density measurement cavity is located above the saturated liquid density measurement cavity, and the saturated gas density measurement cavity and the saturated liquid density measurement cavity are connected through a valve; the saturated gas density measurement cavity and the saturated liquid density measurement cavity are respectively arranged in the constant temperature sleeve;

[0014] The temperature measuring platinum resistance thermometer is arranged at the top of the saturated gas phase density measuring cavity and the saturated liquid phase density measuring cavity respectively, and is connected with a high-precision temperature measuring instrument to measure the saturation temperature of the sample to be measured.

[0015] Preferably, the heating wire has a double-layer structure, the outer layer heating wire is in a continuous heating state, and the inner layer heating wire is in an intermittent heating state.

[0016] Preferably, the high-temperature temperature control system and the saturated gas-liquid phase density measuring system are externally provided with a shell and filled with glass fiber thermal insulation cotton.

[0017] Preferably, the bottom of the saturated liquid phase density measuring cavity is provided with a constant temperature sleeve support.

[0018] Preferably, the bottom of the saturated gas phase density measuring cavity is provided with a heat insulation asbestos pad.

[0019] Preferably, the saturated gas phase density measuring cavity and the saturated liquid phase density measuring cavity are connected through high-temperature resistant valves; the number of the high-temperature resistant valves is three; two high-temperature resistant valves are arranged on the saturated gas phase density measuring cavity and the saturated liquid phase density measuring cavity respectively, and the other high-temperature resistant valve is arranged between the two high-temperature resistant valves.

[0020] Further, the high-temperature resistant valve is communicated with a valve extension rod, and the valve extension rod extends to the outside of the shell.

[0021] Preferably, the wall thickness of the saturated gas phase density measuring cavity is 1-3 mm, and the wall thickness of the saturated liquid phase density measuring cavity is 3-5 mm.

[0022] Preferably, the end of the constant temperature sleeve is provided with two semicircular end covers, and a circular through hole is formed at the center position of the two semicircular end covers to connect the pipeline and the temperature measuring platinum resistance thermometer lead wire.

[0023] A high-temperature saturated gas-liquid phase density measuring method comprises the following steps,

[0024] Step 1, the measurement cavity to be calibrated is subjected to vacuumizing treatment, and a high-precision analytical balance is used to weigh the mass m 10 , a fluid with known density data is selected as standard substance for volume calibration of the measuring cavity; the standard substance fills the cavity to be calibrated and is heated to a calibration temperature, and after equilibrium and stabilization, the corresponding measurement temperature T is recorded, and the valve is closed, the cavity to be calibrated is disassembled and cooled to room temperature, and the mass m1 is weighed, the saturated liquid phase density of the standard substance at this temperature is p0, and the volume V of the cavity to be calibrated is calculated.

[0025] Multiple volume calibration experiments are carried out at each temperature to obtain the average value of volume calibration, the cavity volume at different temperatures is calibrated by changing the measurement temperature, and the cavity volume is fitted into a single value function of temperature;

[0026] In step 2, when the saturated liquid phase density is measured, the saturated liquid phase density cavity is vacuumized, the mass m of the saturated liquid phase density cavity is measured by using a high-precision analytical balance 20 The saturated liquid phase density cavity is filled with the sample to be measured, is heated to the measured temperature, is balanced for a certain time, the temperature T is recorded, the valve is closed, the saturated liquid phase density cavity is disassembled, is cooled to room temperature, the mass m2 of the saturated liquid phase density cavity is measured, and the volume V of the saturated liquid phase density cavity at the temperature T is calculated according to the relationship between the volume calibration and the temperature. L Therefore, the saturated liquid phase density of the sample to be measured at the temperature is ρ L ;

[0027] When the saturated gas phase density is measured, the saturated gas phase density cavity is vacuumized, the mass m of the saturated gas phase density cavity is measured by using a high-precision analytical balance 30 According to the measured saturated liquid phase density data, the maximum filling mass of the sample in the saturated liquid phase density cavity is calculated, then 1 / 2-2 / 3 of the mass of the sample to be measured is filled into the saturated liquid phase density cavity, the temperature is heated to the measured temperature, is balanced for a certain time, the temperature T is recorded, the valve is closed, the saturated gas phase density cavity is disassembled, is cooled to room temperature, the mass m3 of the saturated gas phase density cavity is measured, and the volume V of the saturated gas phase density cavity at the temperature T is calculated according to the relationship between the volume calibration and the temperature. V Therefore, the saturated gas phase density of the sample to be measured at the temperature is ρ V .

[0028] Compared with the prior art, the present application has the following beneficial technical effects:

[0029] The present application provides a high-temperature saturated gas-liquid phase density measuring device, in the experimental measurement process, in order to reduce the influence of the change of the cavity volume with temperature on the measurement accuracy of the saturated gas-liquid phase density, the cavity volume at different temperatures is calibrated by taking the standard substance as a reference, and the calibrated cavity volume is fitted into a single value function of temperature to meet the experimental requirements at different temperatures.

[0030] In order to balance the contradiction between the saturated gas-liquid phase density measurement accuracy and the cavity pressure-bearing capacity, the experimental measurement of the saturated gas phase density is carried out by using cavities with different wall thicknesses, so that the reliability of the saturated gas phase density measurement and the safety of the experimental operation are ensured.

[0031] In order to ensure that the saturated gas does not condense backflow after entering the saturated gas phase cavity, an electric heating wire + high-precision temperature controller + adjustable power supply is used to realize high-precision temperature control in a wide temperature range, and the same temperature control mode is used for the saturated gas-liquid phase cavity to ensure the consistency of the temperature.

[0032] In order to balance the sealing property of the saturated gas-liquid phase cavity and the accuracy of temperature measurement, the platinum resistance thermometer is placed on the upper wall of the cavity through the hole, so that the accuracy of temperature measurement is ensured.

[0033] The application realizes accurate measurement of the saturated gas-liquid phase density of fluid under high temperature conditions, and the device has good stability, and the obtained experimental data is the basis for supporting the experimental research of other thermophysical properties of fluid and the development of state equation, and has good scientific research application prospect; the application can also be used for saturated gas-liquid phase density measurement of oil products under high temperature conditions, so as to meet the research needs of the fireproof performance application of oil products, and also has good industrial application prospect.

[0034] The application can realize accurate measurement of the saturated gas-liquid phase density under extreme harsh conditions, has the advantages of simple test method and good stability, and has a wide applicable temperature and pressure range, and can be used for high-temperature saturated gas-liquid phase density measurement of industrial electrolyte solution, mixed fuel and lubricating oil and other fluids, and can also be used for teaching of energy power related professional course experiments. BRIEF DESCRIPTION OF DRAWINGS

[0035] Figure 1 It is a device structure design drawing of the application.

[0036] Figure 2 It is an end part drawing of the aluminum / copper constant temperature sleeve.

[0037] Figure 3 It is a measurement cavity filling schematic view.

[0038] In the drawings: 1 is a constant temperature sleeve support, 2 is an outer shell, 3 is a heating wire, 4 is a temperature control platinum resistance thermometer, 5 is a high-temperature resistant valve, 6 is a heat insulation asbestos pad, 7 is a valve extension rod, 8 is a temperature measuring platinum resistance thermometer, 9 is a constant temperature sleeve, 10 is a measurement cavity, 11 is an end cover. DETAILED DESCRIPTION

[0039] The application will be further described in detail below in combination with specific embodiments, which are an explanation but not a limitation of the application.

[0040] The application is a device for measuring high-temperature saturated gas-liquid phase density of fluid, which comprises a high-temperature temperature control system and a saturated gas-liquid phase density measurement system.

[0041] The high-temperature temperature control system comprises a temperature controller, an adjustable AC power supply, a platinum resistance thermometer, double-layer heating wires and a thermostat sleeve, the platinum resistance thermometer is connected with the temperature controller and is arranged in the wall of the thermostat sleeve, the temperature of the thermostat sleeve is measured in real time and is fed back to the temperature controller, the temperature controller adjusts the heating power of the double-layer heating wires through the connected adjustable AC power supply, the outer heating wire is in a continuous heating state and is used for offsetting heat exchange between the experimental device and the surrounding environment, and the inner heating wire is in an intermittent heating state, so that precise temperature control of the experimental device is realized.

[0042] The saturated gas-liquid phase density measurement system comprises a saturated gas phase density measurement cavity, a saturated liquid phase density measurement cavity, high-temperature resistant valves, platinum resistance thermometers, high-precision thermometers, a vacuum pump and a high-precision analytical balance, the saturated gas phase density measurement cavity is located above the saturated liquid phase density measurement cavity, the two cavities are connected by using the high-temperature resistant valves, the two cavities are arranged in the thermostat sleeves, the two platinum resistance thermometers are connected with the high-precision thermometers, and the platinum resistance thermometers are arranged at the top positions of the saturated gas phase density measurement cavity and the saturated liquid phase density measurement cavity and are used for measuring the saturated temperature of the sample to be measured, and the vacuum pump is connected with the saturated gas phase density measurement cavity through the high-temperature resistant valves and is used for vacuumizing the saturated gas phase density measurement cavity.

[0043] In the application, the saturated gas phase density cavity and the saturated liquid phase density cavity are both cylindrical cavities welded by 304 stainless steel, and the relative positions are axial up-down structures, the volumes are between 100 and 200 ml, the inner wall surfaces are subjected to fine polishing treatment, and the saturated gas phase density measurement cavity adopts a thin-wall cavity with a thickness of 1-3 mm, so that the saturated gas phase fluid mass in the cavity can be accurately obtained.

[0044] In the application, the saturated gas-liquid phase density measurement cavities are arranged in aluminum / copper thermostat sleeves, the wall thickness of the thermostat sleeves is 15-20 mm, so as to reduce the temperature uniformity of the saturated gas-liquid phase density measurement cavities, two layers of heating wires are wound on the outer wall of the thermostat sleeve, the outer heating wire is in a continuous heating state and is used for offsetting heat exchange between the experimental device and the surrounding environment, and the inner heating wire is in an intermittent heating state, so that precise temperature control in a wide temperature range (room temperature-500 DEG C) is realized.

[0045] In the application, a mechanical vacuum pump or a molecular vacuum pump is used to vacuumize the saturated gas phase density measurement cavity, the vacuum degree of the measurement cavity is required to be below 5 Pa, a high-precision analytical balance with a resolution of 0.1 mg is used to weigh the sample mass in the measurement cavity, and the accurate saturated gas-liquid phase density of the sample to be measured is obtained.

[0046] The saturated gas phase density cavity of the application is insulated by using heat insulation asbestos gaskets between the saturated gas phase density cavity and the fixed aluminum plate, the lower end of the saturated liquid phase density cavity is supported by three aluminum rods with a diameter of 10 mm, and a semi-circular cover is used to divide the end of the constant temperature sleeve, which not only facilitates the measurement of the cavity taken out of the constant temperature sleeve, but also further reduces the heat loss influence of the two ends of the constant temperature sleeve.

[0047] The application adopts aluminum profiles to design high-temperature-resistant valve fixing parts on the basis of the outer frame structure of the experimental device, avoids damage and leakage of the high-temperature-resistant valve during opening and closing, and designs and processes corresponding valve extension rods in combination with the geometric size of the valve rod, thereby facilitating valve opening and closing operation during high-temperature experiments.

[0048] The saturated gas phase density cavity and the saturated liquid phase density cavity are arranged in the same vertical direction, so that the saturated gas phase density cavity can be used as a saturated gas phase density measuring cavity and an expansion cavity for measuring saturated liquid phase density; similarly, the saturated liquid phase density cavity can be used as a saturated liquid phase density measuring cavity and a gas-liquid equilibrium cavity for measuring saturated gas phase density.

[0049] The application discloses a measuring method of a fluid high-temperature saturated gas-liquid phase density device.

[0050] Step 1: volume calibration of the saturated gas-liquid phase density cavity.

[0051] The measuring cavity to be calibrated is cleaned, dried, and vacuumized to below 5 Pa by using a mechanical vacuum pump, a high-precision analytical balance is used to weigh the mass m 10 A fluid with known density data is selected as standard substance for volume calibration of the measuring cavity, and the standard substance should have the characteristics of high density, high boiling point and accurate equation of state, the standard substance is filled in the cavity to be calibrated and heated to a calibration temperature, the corresponding measuring temperature T is recorded after balance and stabilization, the high-temperature-resistant valves 5 and 8 are closed, the cavity to be calibrated is cooled to room temperature, the mass m1 is weighed, the saturated liquid phase density of the standard substance at this temperature is p0, and the volume V of the cavity to be calibrated is calculated as follows:

[0052]

[0053] Multiple volume calibration experiments are performed at each temperature to obtain the average value of the volume calibration, the cavity volume is fitted into a single valued function of temperature by changing the measuring temperature for cavity volume calibration at different temperatures.

[0054] Step 2: saturated liquid phase density measurement.

[0055] The saturated liquid phase density cavity is cleaned, dried, and vacuumed to below 5 Pa by using a mechanical vacuum pump, and the mass m of the saturated liquid phase density cavity is measured by using a high-precision analytical balance 20 The saturated liquid phase density cavity is filled with the sample to be measured, heated to the temperature to be measured, and kept stable for a certain period of time to record the temperature T, and the high-temperature resistant valves 5 and 8 are closed, the saturated liquid phase density cavity is disassembled and cooled to room temperature, and the mass m2 of the saturated liquid phase density cavity is measured, and the volume V of the saturated liquid phase density cavity at the temperature T is calculated according to the volume calibration and temperature relationship formula L The saturated liquid phase density of the sample to be measured at the temperature is calculated as follows: L

[0056]

[0057] Step 3: Measurement of saturated gas phase density.

[0058] When measuring the saturated gas phase density of the fluid, the saturated gas phase density cavity is cleaned, dried, and vacuumed to below 5 Pa by using a mechanical vacuum pump, and the mass m of the saturated gas phase density cavity is measured by using a high-precision analytical balance 30 According to the measured saturated liquid phase density data, the maximum filling mass of the sample in the saturated liquid phase density cavity is calculated, then 1 / 2-2 / 3 of the mass of the sample to be measured is filled into the saturated liquid phase density cavity, the temperature is heated to the temperature to be measured, and kept stable for a certain period of time to record the temperature T, and the high-temperature resistant valves 5 and 8 are closed, the saturated gas phase density cavity is disassembled and cooled to room temperature, and the mass m3 is measured, and the volume V of the saturated gas phase density cavity at the temperature T is calculated according to the volume calibration and temperature relationship formula V The saturated gas phase density of the sample to be measured at the temperature is calculated as follows: V

[0059]

[0060] The selection of the thickness specification of the saturated gas phase density cavity needs to refer to the experimental measurement results of the saturated vapor pressure, and generally, a measurement cavity with a thinner wall thickness in the pressure range is selected.

[0061] In the experimental measurement process of the present application, in order to reduce the influence of the change of the cavity volume with temperature on the measurement accuracy of the saturated gas-liquid phase density, a standard substance is used as a reference to calibrate the cavity volume at different temperatures, and the calibrated cavity volume is fitted into a single-valued function of temperature to meet the experimental requirements at different temperatures.

[0062] ​​In order to balance the contradiction between the accuracy of saturated gas-liquid phase density measurement and the pressure bearing capacity of the cavity, the experimental measurement of the saturated gas phase density of the fluid is carried out by using cavities with different wall thicknesses, so as to ensure the reliability of the saturated gas phase density measurement and the safety of the experimental operation. In order to ensure that the saturated gas does not condense back after entering the saturated gas phase cavity, an electric heating wire + high-precision temperature controller + adjustable power supply is used to realize high-precision temperature control in a wide temperature range, and the same method is used for temperature control of the saturated gas-liquid phase cavity to ensure the consistency of the temperature.

[0063] In order to balance the sealing of the saturated gas-liquid phase cavity and the accuracy of the temperature measurement, a platinum resistance thermometer is placed on the upper wall of the cavity through a hole, so as to ensure the accuracy of the temperature measurement.

[0064] The application realizes the accurate measurement of the saturated gas-liquid phase density of the fluid under high temperature conditions, and the device has good stability, and the obtained experimental data is the basis for supporting the experimental research of other thermal physical properties of the fluid and the development of the equation of state, and has good scientific research application prospect; the application can also be used for the saturated gas-liquid phase density measurement of oil products under high temperature conditions, so as to meet the research needs of the fireproof performance application of the oil products, and also has good industrial application prospect.

[0065] The application uses standard substances to calibrate the effective volumes of the gas phase cavity and the liquid phase cavity respectively, and obtains the saturated gas-liquid phase density of the measured fluid by measuring the sample mass difference of the experimental measurement cavity before and after expansion. The application can realize the accurate measurement of the saturated gas-liquid phase density under extreme harsh conditions, has the advantages of simple test method and good stability, and has a wide temperature and pressure range, which can be used not only for the high-temperature saturated gas-liquid phase density measurement of industrial electrolyte solution, mixed fuel and lubricating oil and other fluids, but also for the teaching of energy power related professional course experiments.

[0066] Embodiment

[0067] Reference Figure 1 The application comprises a high-temperature temperature control system and a saturated gas-liquid phase density measurement system; wherein the high-temperature temperature control system mainly comprises a temperature controller, an adjustable alternating current power supply, a temperature control platinum resistance thermometer 4, a double-layer heating wire 3 and a constant temperature sleeve 9, the temperature controller is provided by Shanghai Sani Precision Instrument Co., Ltd., the model is SCM-SP4RNA, the temperature control range is-200-850 DEG C, the temperature control accuracy is 0.001 DEG C in the range of-25-235 DEG C, the temperature control accuracy of the rest temperature range is 0.01 DEG C, and the temperature controller is arranged outside the saturated gas-liquid phase density experimental device.

[0068] The temperature control platinum resistance thermometer 4 is manufactured by Changsha Fushaid Automation Technology Co., Ltd., the model is 7104 / 574-PT100, the applicable temperature range is 0-500℃, it is an industrial second-level precision platinum resistance thermometer, and a first-class standard platinum resistance thermometer is used for calibration and calibration of the temperature control platinum resistance thermometer 4. The temperature control platinum resistance thermometer 4 is connected with the temperature controller and is placed in the thick-walled center position of the constant temperature sleeve 9, and the temperature of the constant temperature sleeve 9 is measured in real time and fed back to the temperature controller.

[0069] The adjustable AC power supply is manufactured by Shanghai Langge Electrical Co., Ltd., the model is STG-500W, the output voltage range is 0-300V, the corresponding output voltage can be precisely adjusted, and the AC power supply can simultaneously output two identical control voltages. One of the voltages is directly connected with the outer heating wire 3 through the temperature controller and is in a continuous heating state during the experiment temperature control process, which is used to offset the heat exchange between the experimental device and the surrounding environment; and the other voltage is connected with the inner heating wire 3 through the AC relay, and the on-off of the AC relay is precisely controlled according to the temperature control feedback signal of the temperature controller, so that the inner heating wire 3 is in an intermittent heating state, thereby realizing precise temperature control of the experimental device.

[0070] Referring to Figure 1 and Figure 2 , the constant temperature sleeve 9 is made of aluminum material with good thermal conductivity. The wall thickness of the constant temperature sleeve 9 is 15mm, one end of the constant temperature sleeve 9 is provided with two semicircular special end covers 11 for constant temperature, and a circular hole with a diameter of 10mm is formed in the center of the semicircular end cover 11 for connecting the pipeline and arranging the lead wire of the temperature measuring platinum resistance thermometer 4, and the experimental measurement cavity 10 can be easily taken out from the constant temperature sleeve 9 for quality measurement; a temperature measuring blind hole with a diameter of 4.5mm and a depth of 150mm is processed in the center position of the circumferential wall of the constant temperature sleeve 9, and the temperature control platinum resistance thermometer 4 is placed in the blind hole for monitoring the temperature change process of the constant temperature sleeve 9.

[0071] Referring to Figure 1 , the saturated gas-liquid phase density measurement system mainly comprises a keysight 970A digital instrument, a temperature measuring platinum resistance thermometer 8, a high-temperature resistant valve 5, a valve extension rod 7 and a saturated gas-liquid phase density measurement cavity 10. The temperature measuring platinum resistance thermometer 8 is manufactured by North China Sensor Instrument Co., Ltd., the model is WZPK-PT100, the use temperature range is 0-550℃, and it is an industrial A-level precision platinum resistance thermometer. The temperature measuring platinum resistance thermometer 8 is placed in the temperature measuring blind hole of the saturated gas-liquid phase density measurement cavity 10, and is connected with the keysight 970A digital instrument, which is used for precise measurement of the temperature of the saturated gas-liquid phase density cavity 10.

[0072] The saturated gas-liquid phase density measuring cavity 10 is a cylindrical cavity made of 304 stainless steel, and the outer wall size is kept in clearance fit with the inner wall size of the thermostatic sleeve 9, and the inner wall surface is finely polished. The wall thickness of the saturated liquid phase density cavity 10 is 5 mm, and the wall thickness of the saturated gas phase density cavity 10 is 1-3 mm, which is convenient for accurately obtaining the saturated gas phase fluid mass in the experimental cavity. The stainless steel connecting pipeline is welded at the center position of the lower end cover of the saturated gas phase density cavity 10, and the temperature measuring blind hole with an outer diameter of 8 mm, an inner diameter of 5 mm and a depth of 80 mm is welded at the center position of the upper end cover, while the stainless steel connecting pipeline is welded at the center position of the upper end cover of the saturated liquid phase density cavity 10, and the same size temperature measuring blind hole is welded at a position 20 mm away from it.

[0073] The saturated gas phase density cavity 10 is located directly above the saturated liquid phase density cavity 10, and the two are connected by 1 / 16 inch high-pressure stainless steel pipes and high-temperature resistant valves 5. The distance between the high-temperature resistant valve 5 and the saturated gas-liquid phase density measuring cavity 10 should be kept within 60 mm to reduce the influence of uneven temperature distribution of the pipeline on the experimental measurement results. The high-temperature resistant valves 5 in the vertical direction are connected to the vacuum pipeline through a tee, and a high-temperature resistant valve 5 is installed in the middle of the vacuum pipeline for vacuum sealing of the pipeline under high temperature conditions.

[0074] The saturated gas-liquid phase density measuring cavity 10 is located inside the aluminum profile frame shell 2 and is effectively fixed in position by a fixing member. The liquid phase thermostatic sleeve 9 is triangularly fixed and supported by three stainless steel rods with a diameter of 10 mm. The gas phase thermostatic sleeve 9 and the high-temperature resistant valve are fixed in position by a 5 mm thick perforated aluminum plate. The valve extension rod 7 extends the handle of the high-temperature resistant valve 5 to the outside of the aluminum profile frame shell 2, and a 3 mm thick aluminum plate is fixed outside the aluminum profile frame shell 2, with the inside gap filled with thermal insulation cotton.

[0075] The effective volume of the saturated gas-liquid phase density measuring cavity is calibrated. The wall thickness of the gas phase cavity is 1 mm, 1.5 mm and 3 mm respectively, and the wall thickness of the liquid phase cavity is 5 mm. Before the calibration experiment, the saturated gas-liquid phase density cavity is cleaned and vacuumed several times with organic solvents such as petroleum ether, acetone and alcohol to remove oil stains, debris and dust left on the inner wall of the cavity during processing. In the temperature range of 298.15-473.15 K, the effective volume of the saturated gas-liquid phase density measuring cavity is calibrated using ultrapure water, with a temperature interval of 50 K, and the calibrated volume is fitted as a single-valued function of temperature.

[0076] The mass of the saturated gas-liquid phase cavity is weighed by using a high-precision weighing balance, and the cavity is cleaned and vacuumized before weighing. After the sealing test of the experimental device is completed, the saturated liquid phase cavity is filled with samples, and the pressure of the saturated liquid phase cavity is ensured to be below 10 Pa during filling. A special syringe is used to fill the sample to ensure that the filled sample does not contain impurity gas. The schematic diagram during filling is shown in FIG. 5. Figure 3 After filling is completed, the gas-liquid phase cavity is connected through a high-temperature resistant valve 5, and then the experimental system is heated and temperature controlled. When the system temperature rises to the experimental temperature and the temperature fluctuation is less than 30 mK, the valve 5 is opened, and the saturated gas enters the gas phase cavity. After the system reaches equilibrium again, the gas cavity is removed, and the mass of the cavity is measured. Finally, the saturated gas phase density of the sample is calculated by combining the calibrated volume.

[0077] Specific implementation case: saturated gas-liquid phase density measurement of n-hexadecane.

[0078] The n-hexadecane with a high-precision Helmholtz special state equation is used as a test sample, and the sample reagent is purchased from Merck Sigma International Co., Ltd. The sample quality purity is better than 99%, and the test sample is degassed twice at -10°C before the experiment to reduce the influence of dissolved air in the test sample on the experimental measurement accuracy.

[0079] In the temperature range of 373.15-673.15 K, the saturated gas-liquid phase density of n-hexadecane is experimentally studied by using the device. The experimental measurement temperature interval is 50 K, and the detailed experimental results are shown in Table 1. In order to further verify the reliability of the experimental measurement results of the device, the experimental measurement results are compared and analyzed with the Helmholtz special state equation. The relative deviation of the device for measuring the saturated liquid phase density is within ±0.5%, and for the smaller saturated gas phase density, the relative deviation of the measurement is also basically within ±4%, which indicates that the device has good accuracy and reliability.

[0080] Table 1: saturated gas-liquid phase density measurement results of Example 1

[0081]

[0082]

[0083] In the table, m0 is the cavity mass under vacuum condition, m1 is the cavity mass filled with saturated samples, Δm is the mass of the saturated samples in the experimental cavity, V is the volume of the experimental cavity at the measurement temperature, ρ exp is the saturated gas-liquid phase density data measured in the experiment, ρ cal is the calculated value of the standard equation in Refprop, and Δ is the relative deviation between the experimental value and the calculated value.

Claims

1. A method for measuring the density of a high-temperature saturated gas-liquid phase, characterized in that, A high-temperature saturated gas-liquid phase density measuring device is used, the measuring device comprising: a high-temperature temperature control system and a saturated gas-liquid phase density measuring system; The high-temperature temperature control system includes a temperature controller, a temperature-controlled platinum resistance thermometer (4), a heating wire (3), and a constant temperature sleeve (9). The temperature-controlled platinum resistance thermometer (4) is connected to the temperature controller and placed in the side wall of the constant temperature sleeve (9); the temperature-controlled platinum resistance thermometer (4) measures the temperature of the constant temperature sleeve (9) in real time and feeds it back to the temperature controller; the heating wire (3) is set on the outer wall of the constant temperature sleeve (9), and the temperature controller controls the heating temperature of the heating wire (3). The saturated gas-liquid density measurement system includes a measuring chamber (10) and a temperature-measuring platinum resistance thermometer (8). The measuring chamber (10) includes a saturated gas density measuring chamber and a saturated liquid density measuring chamber. The saturated gas density measuring chamber is located above the saturated liquid density measuring chamber. The saturated gas density measuring chamber and the saturated liquid density measuring chamber are connected by a valve. The saturated gas density measuring chamber and the saturated liquid density measuring chamber are respectively placed in a constant temperature sleeve (9). The temperature measuring platinum resistance thermometer (8) is respectively installed at the top of the saturated gas phase density measuring chamber and the saturated liquid phase density measuring chamber; the temperature measuring platinum resistance thermometer (8) is connected to a high-precision thermometer for measuring the saturation temperature of the sample to be tested; The method includes: Step 1: Vacuum the measuring cavity to be calibrated, and weigh it using a high-precision analytical balance to obtain its mass. m 10 A fluid with known density data is selected as the standard substance for calibrating the volume of the measuring chamber; the standard substance is filled into the chamber to be calibrated and heated to the calibration temperature. After equilibrium is reached, the corresponding measurement temperature is recorded. T Then close the valve, disassemble the cavity to be calibrated, cool it to room temperature, and weigh it to obtain its mass. m 1. The saturated liquid phase density of the standard substance at this temperature is: ρ 0, calculate the volume of the cavity to be calibrated. V ; Multiple volume calibration experiments were conducted at each temperature, and the average value of the volume calibration was obtained. The cavity volume was calibrated at different temperatures by changing the measurement temperature, and the cavity volume was fitted as a single-valued function of temperature. Step 2: When measuring the density of the saturated liquid phase, the saturated liquid phase density chamber is evacuated, and its mass is measured using a high-precision analytical balance. m 20 The saturated liquid phase density chamber is filled with the sample to be tested. The temperature is raised to the test temperature and stabilized for a certain period of time; the temperature is then recorded. T Then close the valve, disassemble the saturated liquid phase density chamber, cool it to room temperature, and weigh it to obtain its mass. m 2. The temperature is calculated based on the relationship between volume calibration and temperature. T The volume of the saturated liquid phase density cavity at that time is V L The density of the saturated liquid phase of the sample at that temperature is then determined. ρ L for: ; When measuring the density of the saturated gas phase, the saturated gas phase density chamber is evacuated, and its mass is determined using a high-precision analytical balance. m 30 Based on the measured saturated liquid density data, the maximum mass of sample to be filled into the saturated liquid density chamber is calculated. Then, 1 / 2 to 2 / 3 of this mass of sample is filled into the saturated liquid density chamber, and the temperature is raised to the test temperature and stabilized for a certain period of time. The temperature is then recorded. T Close the valve, disassemble the saturated gas phase density chamber and cool it to room temperature, then weigh out the mass of... m 3. The temperature is calculated based on the relationship between volume calibration and temperature. T The volume of the saturated gas phase density cavity at that time is V V The saturated gas phase density of the sample at that temperature is then... ρ V for: .

2. The method for measuring the density of a high-temperature saturated gas-liquid phase according to claim 1, characterized in that, The heating wire (3) has a double-layer structure. The outer heating wire is in a continuous heating state, while the inner heating wire is in an intermittent heating state.

3. The method for measuring the density of a high-temperature saturated gas-liquid phase according to claim 1, characterized in that, The high-temperature temperature control system and the saturated gas-liquid phase density measurement system are equipped with an outer shell (2) and filled with glass fiber insulation cotton.

4. The method for measuring the density of a high-temperature saturated gas-liquid phase according to claim 1, characterized in that, The bottom of the saturated liquid phase density measuring chamber is provided with a constant temperature sleeve support (1).

5. The method for measuring the density of a high-temperature saturated gas-liquid phase according to claim 1, characterized in that, The bottom of the saturated gas phase density measuring chamber is provided with a heat-insulating asbestos pad (6).

6. The method for measuring the density of a high-temperature saturated gas-liquid phase according to claim 1, characterized in that, The saturated gas phase density measuring chamber and the saturated liquid phase density measuring chamber are connected by a high-temperature resistant valve (5); there are three high-temperature resistant valves (5); two of the high-temperature resistant valves (5) are respectively set on the saturated gas phase density measuring chamber and the saturated liquid phase density measuring chamber, and the other high-temperature resistant valve (5) is set between the two high-temperature resistant valves (5).

7. The method for measuring the density of a high-temperature saturated gas-liquid phase according to claim 6, characterized in that, The high-temperature resistant valve (5) is connected to a valve extension rod (7), which extends to the outside of the housing.

8. The method for measuring the density of a high-temperature saturated gas-liquid phase according to claim 1, characterized in that, The wall thickness of the saturated gas phase density measuring chamber is 1~3 mm, and the wall thickness of the saturated liquid phase density measuring chamber is 3~5 mm.

9. The method for measuring the density of a high-temperature saturated gas-liquid phase according to claim 1, characterized in that, The thermostatic sleeve (9) has two semi-circular end caps (11) at its end. The center of the two semi-circular end caps (11) forms a circular through hole for connecting the pipeline and the lead wire of the temperature measuring platinum resistance thermometer (8).

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