Sensor arrangement optimization and detection method of pVTt gas flow standard device

Abstract

The invention discloses a sensor arrangement optimization and detection method of a pVTt gas flow standard device. The method comprises the following steps: acquiring a CFD simulation calculation model pre-constructed based on a three-dimensional model of a to-be-calibrated spray pipe and a three-dimensional model of a to-be-used standard container; obtaining temperature values of the standard container three-dimensional model under different grids, which are calculated by the CFD simulation calculation model after the to-be-calibrated spray pipe three-dimensional model is inflated into the to-be-used standard container three-dimensional model under a preset air inlet flow working condition; calculating a temperature correlation coefficient of each grid according to the temperature values under different grids; acquiring position information of a plurality of grids with relatively high temperature correlation coefficients; and arranging a temperature sensor in the standard container to be used according to the position information. The method has the advantages that the arrangement number of the temperature measuring point sensors is reasonably optimized through CFD simulation calculation and correlation coefficient analysis, so that the purposes of saving the time cost of nozzle calibration and improving the working efficiency of the airflow calibration device are achieved.

Description

Technical Field

[0001] The present invention relates to a sensor arrangement optimization and detection method for a pVTt gas flow standard device, belonging to the technical field of flow calibration of a flow standard container. Background Art

[0002] In recent years, with the global shortage of energy resources, the social requirements for flow measurement testing technologies have been continuously increasing. Gases such as air and natural gas are used in departments such as petroleum, chemical industry, metallurgy, machinery, national defense, science and technology, as well as in people's daily lives. In order to use gases scientifically and save resources, equipment for calibrating gas flow meters established for the accuracy of gas flow meters is commonly used. With the rapid development of China's economy, higher requirements have been put forward for the types of media, state parameters, flow ranges, measurement accuracies, etc. of gas flow measurements in industrial, civil, and housing purchase departments. Gas metering has received increasing attention. Therefore, the development of gas flow meters has become the focus of the development of China's flow measurement instruments, and establishing a high-accuracy flow standard device is of utmost importance for the research and manufacture of flow meters.

[0003] The pVTt method gas flow standard device is a primary gas flow standard device for indirectly measuring mass flow, mainly used for calibrating critical flow nozzles and other gas flow meters. The critical flow nozzle is generally used as a secondary standard device to transfer the quantity value to the working flow meter. The pVTt method gas flow standard device has a relatively high accuracy, and the device equipment is simple and easy to construct and maintain. Its application is relatively extensive and its status is very important both at home and abroad. The pVTt standard device mostly uses a horizontal standard container. When calibrating the sonic nozzle, the container needs to be evacuated and filled with gas. After the gas filled during the calibration process undergoes a natural convection process in the container for a relatively long time, the gas temperature and pressure in the container reach stability and uniformity.

[0004] At present, China's pVTt method gas flow standard device generally uses the water bath cooling method to shorten the time for the temperature field in the standard container to reach a stable and uniform state. Ensure that the ambient temperature is stable at about 20°C to eliminate the influence of seasons and ambient temperature, and at the same time ensure that the uncertainty of the device is better than 0.05% (k = 2); however, this method cannot completely avoid the influence of temperature non-uniformity caused by the intake air and the gas cooling process in the tank. At the same time, during this process, it is necessary to ensure that all measuring point temperature sensors in the standard container reach a stable state before flow calibration can be carried out, which also makes the current calibration stable time about 30 - 120 minutes, and sometimes even exceeds 2 hours, seriously restricting the production capacity effect of the pVTt standard device. In view of this, researching and constructing a pVTt method gas flow standard device with high accuracy and high working efficiency has very important engineering application significance. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to overcome the defects of the prior art and provide a method for optimizing the sensor arrangement and detection of a pVTt gas flow standard device.

[0006] To solve the above technical problem, the present invention provides a method for optimizing the sensor arrangement of a pVTt gas flow standard container, including:

[0007] Obtain a CFD simulation calculation model pre-constructed based on the three-dimensional model of the nozzle to be calibrated and the three-dimensional model of the standard container to be used;

[0008] Obtain the temperature values of different meshes of the three-dimensional model of the standard container calculated by the CFD simulation calculation model after inflating the three-dimensional model of the standard container to be used with the three-dimensional model of the nozzle to be calibrated under the preset inlet gas flow conditions;

[0009] Calculate the temperature correlation coefficient of each mesh according to the temperature values of different meshes;

[0010] Obtain the position information of several meshes with higher temperature correlation coefficients;

[0011] Arrange temperature sensors in the standard container to be used according to the position information.

[0012] Further, the obtaining of the CFD simulation calculation model pre-constructed based on the three-dimensional model of the nozzle to be calibrated and the three-dimensional model of the standard container to be used includes:

[0013] Obtain the information of the nozzle to be calibrated and the standard container to be used, input the information of the nozzle to be calibrated and the standard container to be used into three-dimensional software to establish the three-dimensional model of the nozzle to be calibrated and the three-dimensional model of the standard container to be used, and connect the three-dimensional model of the nozzle to be calibrated and the three-dimensional model of the standard container to be used to construct a CFD simulation calculation model.

[0014] Further, the preset inlet gas flow conditions include several different inlet gas flow conditions.

[0015] Further, the calculation formula of the temperature correlation coefficient is:

[0016]

[0017] Among them, Correl(T,T0) is the temperature correlation coefficient, T is the temperature value of each mesh at different times, and T0 is the average temperature of all meshes at the corresponding time.

[0018] Further, the different meshes of the three-dimensional model of the standard container are several preset temperature acquisition points.

[0019] A detection method for a pVTt gas flow standard device includes:

[0020] Arrange temperature sensors and pressure sensors in a corresponding standard container according to the sensor layout optimization method;

[0021] Vacuum the standard container. When the gas in the standard container reaches the initial equilibrium state, measure the initial pressure P1 and temperature T1;

[0022] Inflate the standard container through the nozzle to be calibrated. When the preset inflation time t is reached, stop inflating. After the gas in the standard container reaches equilibrium, measure the pressure P2 and temperature T2 at the equilibrium final state;

[0023] Calculate the mass flow rate of the gas flowing into the standard container by combining the initial pressure P1 and temperature T1, and the pressure P2 and temperature T2 at the equilibrium final state.

[0024] Furthermore, the formula for calculating the mass flow rate of the gas flowing into the standard container is:

[0025]

[0026] In the formula, q m is the gas mass flow rate, V is the volume of the standard container, R is the universal gas constant, and M is the gas molecular weight.

[0027] Furthermore, the temperature T1 and temperature T2 are respectively the average values of all temperature sensors in the corresponding states.

[0028] Furthermore, the initial pressure P1 and pressure P2 are respectively the average values of all pressure sensors in the corresponding states

[0029] Furthermore, the judgment process for the gas in the standard container to reach equilibrium is as follows:

[0030] Calculate the difference between the maximum value and the minimum value measured by the temperature sensors at the current moment. When the difference is less than the preset threshold, it is confirmed that equilibrium has been reached.

[0031] The beneficial effects achieved by the present invention:

[0032] 1. Based on the pVTt measurement principle, under the requirement of ensuring measurement accuracy, the present invention rationally optimizes the number of temperature measurement point sensors through CFD simulation calculation and correlation coefficient analysis, so as to achieve the purpose of saving the time cost of nozzle calibration and improving the working efficiency of the air flow calibration device. This method is simple to operate, applicable to pVTt measurement devices of different models, greatly reduces the measurement cost, and improves the verification efficiency;

[0033] 2. This method has a high measurement accuracy level, low investment, and a wide range of applicable applications;

[0034] 3. The present invention can also play a positive guiding role in the improvement of pVTt measurement devices. Description of the Drawings

[0035] Figure 1 is the working principle of the pVTt method gas flow standard device;

[0036] Figure 2 is the prediction process of the standard container state parameters;

[0037] Figure 3 is the research flow chart of the efficient temperature measurement point scheme for the standard container;

[0038] Figure 4 is the processing flow chart of the measured point temperature data;

[0039] Figure 5 is the standard container device model and main parameters;

[0040] Figure 6 is the schematic diagram of the sensor arrangement inside the standard container;

[0041] Figure 7 is the schematic diagram of the computational grid of the standard container;

[0042] Figure 8 is the graph of the average pressure change of the container after the intake ends;

[0043] Figure 9 is the graph of the average temperature change of the container after the intake ends;

[0044] Figure 10 is the distribution diagram of temperature sensors with relatively good overall correlation inside the standard container. Detailed Implementation Manner

[0045] The present invention will be further described below with reference to the drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present invention and cannot be used to limit the protection scope of the present invention.

[0046] Embodiment 1:

[0047] A method for optimizing the sensor arrangement of a pVTt gas flow standard device shown in the present invention, and its specific technical implementation method includes the following steps:

[0048] Calibrate the throat diameter of the nozzle as needed, and establish a model of the nozzle to be measured through 3D software. Combine the nozzle model to be measured with a standard container so that the nozzle to be calibrated is connected to the standard container, achieving the purpose of filling the standard container with gas through the nozzle opening. During the CFD simulation calculation, control the mass flow rate of the gas filled into the standard container by changing different nozzle models. Calculate and analyze the simulation conditions through an engineering thermodynamics model to predict the distribution laws of the pressure field and temperature field in the standard container; combine the existing experimental data, compare and analyze the simulation results with the existing experimental data to determine the accuracy of the simulation process (if the accuracy of the simulation results is lower than the required value, reset the boundary conditions and recalculate iteratively until a matching calculation result is obtained). The specific simulation calculation process is as Figure 2 shown.

[0049] Regarding the variation characteristics of the gas flow and temperature distribution (internal and external heat exchange) in the standard container after the intake, establish a computational fluid dynamics and heat exchange model, and conduct numerical calculation simulations under fine grids based on typical conditions to study the unsteady law of the temperature distribution in the container, and clarify the effectiveness and rationality of the current temperature sensor measurement point layout; study the relationship between the temperature change laws of each measurement point in the container and the change laws of the average state of the standard container, and find typical temperature monitoring points where the temperature and pressure can stabilize quickly and can reflect the average state of the entire pressure vessel. That is, the key is to find reasonable typical temperature measurement points that can converge and stabilize quickly, thereby significantly reducing the current detection and calibration waiting time. The specific implementation process is as Figure 3 shown.

[0050] In this embodiment, according to the layout of the sensors in the existing pVTt gas flow standard device, calculate the temperature points at the corresponding positions during the CF D simulation calculation, number them one by one, and sort out the temperature data of various sensors measured under different intake flow conditions. By means of the Pearson correlation coefficient analysis method, analyze the change laws of the average temperature of the pVTt standard container and the temperatures of each measurement point after the intake. The entire data processing process is as Figure 4 shown.

[0051] Pearson correlation coefficient, and the calculation formula for this correlation coefficient is:

[0052]

[0053] where T is the temperature measurement value of each sensor at different times, and T0 is the average temperature of all sensors at the corresponding time.

[0054] The correlation coefficient reflects the degree of correlation between these two sets of parameters. This value ranges between -1 and +1. The closer the absolute value is to 1, the higher the degree of correlation between the two; the closer it is to 0, the lower the degree of correlation between the two. The positive or negative sign of the symbol determines whether the relationship between the two sets of data is positive correlation or negative correlation. By calculating the correlation coefficient, the degree of approximation between the temperature measurement levels of each sensor and the average temperature can be generally reflected. The range of the variable correlation strength parameter is shown in Table 1, the table of the variable correlation strength parameter range.

[0055] Table 1:

[0056] Range of correlation coefficient values Strength of variable correlation 0.8-1.0 Very strong correlation 0.6-0.8 Strong correlation 0.4-0.6 Moderate correlation 0.2-0.4 Weak correlation 0.0-0.2 Very weak correlation or no correlation

[0057] According to the results of the correlation analysis, several groups of sensors with relatively high correlation between the sensor temperature and the average temperature under each working condition are listed separately. For sensors with good correlation, it proves that the temperature change of the sensor is similar to the average temperature, or rather, the correlation with the average temperature change is very high. Therefore, in the actual process of arranging temperature sensors, those with good correlation with the average temperature can be selected for arrangement; in this way, the number of temperature sensors in the standard container can be reasonably reduced, so as to screen out some representative sensors. Under the premise of meeting the average temperature measurement accuracy requirements of all sensors in the pVTt device, the measured temperature values of these sensors can converge quickly, so as to achieve the purpose of saving the time cost of nozzle calibration and improving the working efficiency of the gas flow calibration device. Pressure sensors are also arranged at the same position of the temperature sensors.

[0058] Example 2:

[0059] This example introduces a detection method for a pVTt gas flow standard device, including the following process:

[0060] The pVTt method gas flow standard device uses a critical flow nozzle as a control element, and determines the actual mass flow value of the gas of the meter under test by measuring the gas pressure and temperature in the standard container before and after inflation in the device. Compare it with the displayed value of the meter under test to calculate the indication error of the meter under test. In the pVTt method, p represents the gas pressure in the standard container, V represents the volume of the standard container, T represents the gas temperature in the standard container, and t represents time. As Figure 1 shown, it shows a schematic diagram of the working principle of the pVTt method gas flow standard device.

[0061] The working principle of the pVTt method gas flow standard device is as follows: First, evacuate the standard container. When the gas in the container reaches the initial equilibrium state, calculate the initial pressure P i and the temperature T of each sensor i, then open the solenoid valve to inflate the standard container. When the pre-set inflation time, i.e., the calibration time t, is reached, the photoelectric pulse signal converter will control the solenoid valve to close automatically. After the gas in the container reaches equilibrium, measure the pressure P at the final equilibrium state f and the temperature T of each sensor f , the function of the control element critical flow nozzle is to ensure that within the calibration time t, the mass flow rate of the gas injected into the standard container is constant. Without considering the compression factor and container temperature correction, according to the ideal gas state equation, the mass flow rate of the gas flowing into the standard container can be calculated as follows:

[0062]

[0063] In the formula, R is the universal gas constant; M is the molecular weight of the gas, so VM / R is a constant. Thus, can qualitatively represent the mass of the gas in the container.

[0064]

[0065]

[0066]

[0067]

[0068] In the current calibration practice, by arranging n temperature sensors in the standard container, performing arithmetic mean processing on the n temperature sensors, and substituting the obtained P1, P2, T1, and T2 into the formula to calculate the gas mass.

[0069] When the gas temperature in the container reaches uniformity, calculating the gas mass using the arithmetic mean temperature can obtain a sufficiently accurate gas mass; when the temperature in the container has not reached uniformity, performing arithmetic mean processing on the n temperature sensors is meaningless. Therefore, during the actual test process, we also simultaneously monitor the deviation situation (the difference between the maximum value and the minimum value) of the stability of the n measurement points. When the deviation value is less than 0.5 °C, the above formula is used to calculate the temperature.

[0070] Example 3, verification process:

[0071] Select a horizontal pVTt standard container with a total volume of approximately 34 m 3 , the intake pipe diameter is 150 mm, located on the side of the horizontal tank, and the model is approximately 9600 mm in total length. Taking the intake flow rate Q = 256 m 3 / h working condition (Q256 working condition, the corresponding nozzle diameter is D0 = 21.64 mm, where D = 150 mm, L = 240 mm) as an example. Simplify the intake control valve, connect the nozzle to the intake pipe, and the container model and main geometric parameters are as Figure 5As shown in the figure, 40 temperature sensors (T102 - T141) are set in the standard container to monitor the temperature change in the container in real time during the air intake and stabilization processes, such as Figure 6 shown

[0072] The present invention uses CFD simulation to calculate the ventilation and internal homogenization processes of the pVTt standard container under Q256 flow rate, including the air intake process and the natural convection process of the gas in the container after the control valve is closed, Figure 7 The figure shows the schematic diagram of the calculation grid division. We often focus on the flow process after the ventilation ends, so the end moment of air intake is taken as the initial state of the natural convection process. According to the ideal gas state equation, under the conditions of a temperature of 20°C and an atmospheric pressure of 1 atm, when the gas temperature deviation is 0.5°C, the calculation error of the gas mass will be 0.17%, and when the pressure deviation is 10 Pa, the calculation error of the gas mass will be 0.02%. In order to shorten the calculation time and keep in line with the measured standard at the same time, during numerical simulation, when the average temperature difference in the container is less than 0.5°C (the pressure difference is generally less than 10 Pa), it is taken as the calculation end condition, that is, it is regarded that the average temperature and pressure in the container have reached a uniform state. Figure 8 and Figure 9 represent the schematic diagrams of the calculation results of the average temperature and average pressure in the standard container under the Q256 working condition. Similarly, the gas state parameters in the standard container of each group at different air intake moments can be calculated.

[0073] According to the measured data of the 40 temperature sensors (numbered TT102 - TT141) of the existing 34m 3 standard container, by analyzing the Pearson correlation coefficient, by analyzing the change laws of the average temperature of the standard container and the temperature at each measuring point after the air intake ends, the correlation coefficients between the temperature of each sensor and the average temperature in different groups of data are obtained. According to the correlation analysis results, several sensors with relatively high correlation between the sensor temperature and the average temperature in each group are selected, and the intersection and union are calculated respectively to obtain two groups of sensor types. The sensor type numbers obtained are shown in Table 2 for the selected sensor types and the corresponding quantities and numbers.

[0074] Table 2:

[0075]

[0076] The maximum value, minimum value, average value and range of each temperature measurement moment of each group of sensors are calculated as follows:

[0077]

[0078] In the formula, is the average temperature at each moment, t iis the actual measured temperature value, and n is the number of sensors taken in different groups. This average value can reflect the average temperature measurement level of the sensors in this group under the corresponding working conditions.

[0079] At=Max{t1,t2,...,t n}-Min{t1,t2,...,t n}

[0080] In the formula, Δt is the within-group range at each moment, and n is the number of sensors taken in different groups. This range can reflect the fluctuation of the temperature measurement of the sensors in this group at different moments under the corresponding working conditions.

[0081] Taking the data corresponding to the two groups of sensors under the selected Q256 working condition as an example, by taking the parameter indicators (temperature average value and temperature range) of the sensors in each group at different moments and the time taken to reach this indicator in a certain calibration data, it can be found that the average temperature measurement results and fluctuation conditions of different numbers of sensors selected under the Q256 working condition are in good agreement compared with all 40 sensors. The comparison of the parameter changes corresponding to 22 sensors and 40 sensors is as Figure 10 shown.

[0082] Taking the existing 40 sensors as a reference group, setting T max -T min <0.5℃ as the stable range of temperature measurement, according to the processed data, when t0 = 25 min, the temperature range ΔT0 at this moment is 0.5℃, and the corresponding average temperature value T ave0 = 21.14℃. Overall, the temperature measurement range of all 40 sensors completely includes the temperature measurement range of the second group of sensors (22 temperature points), which indicates that their average temperature values, that is, the overall temperature measurement levels, are very close. And for the second group of sensors (22 temperature points), when t1 = 17 min, the temperature range ΔT0 at this moment is 0.5℃, and the error between the corresponding average temperature value and the average temperature value of the 40 sensors is within the allowable 1% range. At the same time, from the perspective of the degree of fluctuation and stability, since the change range of the latter is smaller, this shows that the temperature measured by the selected second group of sensors (22 temperature points) has higher stability and can enter the stable stage of temperature measurement faster.

[0083] In view of this, the method of optimizing and reasonably arranging the temperature measurement points with the second group of sensors (22 temperature points) can be adopted, so that the time for the pVTt calibration device to reach the stable state is greatly reduced, the calibration time of the pVTt gas flow device can be effectively reduced, and the working efficiency of the pVTt gas flow standard device can be improved.

[0084] Those skilled in the art should understand that the embodiments of the present invention can be provided as a method, a system, or a computer program product. Therefore, the present invention can take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware aspects. Moreover, the present invention can take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk memory, CD-ROM, optical memory, etc.) that contain computer-usable program code.

[0085] The present invention is described with reference to the flowcharts and / or block diagrams of methods, apparatuses (systems), and computer program products according to embodiments of the present invention. It should be understood that each flow and / or block in the flowchart and / or block diagram can be implemented by computer program instructions, and the combination of flows and / or blocks in the flowchart and / or block diagram can also be implemented by computer program instructions. These computer program instructions can be provided to the processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing devices to generate a machine, so that the instructions executed by the processor of the computer or other programmable data processing devices generate means for implementing the functions specified in one Figure 1 one flow or multiple flows and / or blocks Figure 1 one block or multiple blocks.

[0086] These computer program instructions can also be stored in a computer-readable memory that can direct a computer or other programmable data processing device to work in a specific manner, so that the instructions stored in the computer-readable memory generate a manufactured article including instruction means, and the instruction means implements the functions specified in one Figure 1 one flow or multiple flows and / or blocks Figure 1 one block or multiple blocks.

[0087] These computer program instructions can also be loaded onto a computer or other programmable data processing device, so that a series of operation steps are executed on the computer or other programmable device to generate a computer-implemented process, and the instructions executed on the computer or other programmable device provide steps for implementing the functions specified in one Figure 1 one flow or multiple flows and / or blocks Figure 1 one block or multiple blocks.

[0088] The above is only the preferred embodiment of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the technical principle of the present invention, several improvements and modifications can be made, and these improvements and modifications should also be regarded as the protection scope of the present invention.

Claims

1. An optimization method for the sensor arrangement of a pVTt gas flow standard device, characterized in that Including: Obtain a CFD simulation calculation model pre - constructed based on the three - dimensional model of the nozzle to be calibrated and the three - dimensional model of the standard container to be used; Obtain the temperature values of different meshes of the three - dimensional model of the standard container calculated by the CFD simulation calculation model after the three - dimensional model of the nozzle to be calibrated inflates the three - dimensional model of the standard container to be used under the preset inlet air flow condition; Calculate the temperature correlation coefficient of each mesh according to the temperature values of different meshes; Obtain the position information of several meshes with higher temperature correlation coefficients; Arrange sensors in the standard container to be used according to the position information.

2. The optimization method for the sensor arrangement of a pVTt gas flow standard device according to claim 1, characterized in that The obtaining of the CFD simulation calculation model pre - constructed based on the three - dimensional model of the nozzle to be calibrated and the three - dimensional model of the standard container to be used includes: Obtain the information of the nozzle to be calibrated and the information of the standard container to be used, input the information of the nozzle to be calibrated and the information of the standard container to be used into three - dimensional software to establish the three - dimensional model of the nozzle to be calibrated and the three - dimensional model of the standard container to be used, and connect the three - dimensional model of the nozzle to be calibrated and the three - dimensional model of the standard container to be used to construct a CFD simulation calculation model.

3. The optimization method for the sensor arrangement of a pVTt gas flow standard device according to claim 1, characterized in that The preset inlet air flow condition includes several different inlet air flow conditions.

4. The optimization method for the sensor arrangement of a pVTt gas flow standard device according to claim 1, characterized in that The calculation formula of the temperature correlation coefficient is: Among them, Correl(T,T0) is the temperature correlation coefficient, T is the temperature value of each mesh at different times, and T0 is the average temperature of all meshes at the corresponding time.

5. The optimization method for the sensor arrangement of a pVTt gas flow standard device according to claim 1, characterized in that The different meshes of the three - dimensional model of the standard container are several preset temperature acquisition points.

6. A detection method for a pVTt gas flow standard device, characterized in that Including: Arrange temperature sensors and pressure sensors in the corresponding standard container according to the sensor arrangement optimization method described in any one of claims 1 - 5; Vacuum the standard container. When the gas in the standard container reaches the initial equilibrium state, measure the initial pressure P1 and temperature T1; Inflate the standard container through the nozzle to be calibrated. When the preset inflation time t is reached, stop inflation. After the gas in the standard container reaches equilibrium, measure the equilibrium final pressure P2 and temperature T2; Calculate the mass flow rate of the gas flowing into the standard container by combining the initial pressure P1 and temperature T1, and the equilibrium final pressure P2 and temperature T2.

7. The detection method for a pVTt gas flow standard device according to claim 6, characterized in that The formula for calculating the mass flow rate of the gas flowing into the standard container is: where q m is the gas mass flow rate, V is the volume of the standard container, R is the universal gas constant, and M is the molecular weight of the gas.

8. The detection method for a pVTt gas flow standard device according to claim 6, characterized in that The temperature T1 and temperature T2 are respectively the average values of all temperature sensors in the corresponding states.

9. The detection method for a pVTt gas flow standard device according to claim 6, characterized in that The initial pressure P1 and pressure P2 are respectively the average values of all pressure sensors in the corresponding states.

10. The detection method for a pVTt gas flow standard device according to claim 6, characterized in that The judgment process for the gas in the standard container to reach equilibrium is: Calculate the difference between the maximum value and the minimum value measured by the temperature sensor at the current moment. When the difference is less than the preset threshold, it is confirmed that equilibrium is reached.

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