CN110470364B - A device and method for volume calibration of standard container by pVTt method - Google Patents

Abstract

The embodiments of the present application provide a device and method for calibrating the volume of a standard container by the pVTt method. The device includes a liquid nitrogen container for holding liquid nitrogen; a weighing device for weighing the liquid nitrogen container; The pVTt method standard container connected to the liquid nitrogen container adopts the scheme in this application, and the liquid nitrogen container is used for the volume calibration of the pVTt method standard container, which can better improve the accuracy of the pVTt method standard container volume calibration.

Description

A device and method for volume calibration of standard container by pVTt method

technical field

The present application relates to gas flow measurement technology, in particular, to a device and method for calibrating the volume of a standard container by the pVTt method.

Background technique

The pVTt method gas flow standard device is a standard device for indirectly measuring mass flow. It calculates the standard mass flow by measuring the gas pressure p, volume V, temperature T and time t in the standard container. It is the current accuracy level for obtaining standard flow. One of the highest methods.

In this measurement method, the calibration of the standard container volume is the most important verification item of the pVTt method device, and the result has a great influence on the accuracy of the pVTt method device. At present, there are several volume calibration methods for standard containers. According to the different media used for calibration, they can be divided into two categories: gas calibration method and water calibration method. Compared with the gas calibration method, the water calibration method is affected by many factors such as residual water in the container before the standardization, residual gas in the process, gas in water, and different media from the actual use. Therefore, the pVTt method with high accuracy level generally requires The volume calibration was carried out by the gas calibration method.

However, when the conventional gas standard method is used for calibration, nitrogen is generally used. After the nitrogen cylinder is deflated, the temperature drops sharply, so a layer of water is often condensed on the outer surface of the nitrogen cylinder. In this case, it is necessary to wait for the temperature of the nitrogen cylinder to return to the ambient temperature, and even to dry its surface by means of blowing, heating, etc., and then balance and weigh the balance. The waiting time is long, often a few cubic The total time required for gas calibration on a standard container of rice takes several days, and it is not easy to ensure the repeatability of calibration, so this weighing method greatly affects the calibration accuracy. In addition, due to the low density of the gas medium, when weighing the high-pressure nitrogen cylinder, the net mass of the effective gas is much less important than the tare of the nitrogen cylinder. Generally, the high-pressure nitrogen cylinder of 15MPa has a tare weight of about 50kg, while the gas The mass is only about 5kg, and this phenomenon of large mass and small weighing is extremely detrimental to the accuracy of gas mass weighing.

SUMMARY OF THE INVENTION

The embodiments of the present application provide a device and method for calibrating the volume of a standard container by the pVTt method, which can better improve the accuracy of the volume calibration of the standard container by the pVTt method.

According to a first aspect of the embodiments of the present application, a device for calibrating the volume of a standard container by the pVTt method is provided, including: a liquid nitrogen container for holding liquid nitrogen; a scale for weighing the liquid nitrogen container Measuring equipment; pVTt method standard container connected to the liquid nitrogen container.

According to a second aspect of the embodiments of the present application, a method for calibrating the volume of a standard container by the pVTt method is provided. The method is implemented based on liquid nitrogen, and includes: obtaining a first pressure value after the pressure and temperature in the standard container are stabilized before the standard container is inflated. and the first temperature value; obtain the second pressure value and the second temperature value after the pressure and temperature in the container are stabilized after the standard container is inflated, as well as the weight mass value of the weighing equipment, the container main valve of the liquid nitrogen container and the inlet valve of the vaporizer The first volume value of the emptying of the pipe section between; the cumulative flow meter on the liquid nitrogen container indicates that it is used to connect between the gasifier inlet valve and the standard container inlet valve of the gasifier of the standard container and the liquid nitrogen container the second volume value of the pipe section; according to the first pressure value, the second pressure value, the mass value of the weight and the first volume value, determine the mass value of the evacuated nitrogen in the pipe section between the main valve of the container and the inlet valve of the gasifier; according to The nitrogen mass value, the second volume value, the first temperature, the second temperature, and the cumulative flow meter indicate the standard volume of the standard container.

The device for calibrating the volume of a standard container by the pVTt method provided in the examples of this application is used for a liquid nitrogen container for holding liquid nitrogen; a weighing device for weighing the liquid nitrogen container; and the liquid nitrogen container Connected pVTt standard container. Realizing gas calibration based on liquid nitrogen, avoiding the disadvantage of large tare weight and small weighing, and using a liquid nitrogen container to complete the inflation of the standard container, avoiding the frequent replacement of gas cylinders in the middle and repeated tare and re-weighing steps , which is beneficial to improve the weighing accuracy and improve the accuracy of the final result.

Description of drawings

The drawings described herein are used to provide further understanding of the present application and constitute a part of the present application. The schematic embodiments and descriptions of the present application are used to explain the present application and do not constitute an improper limitation of the present application. In the attached image:

Figure 1 is a schematic diagram of the structure of the device for volume calibration of standard containers by the pVTt method under normal circumstances;

2 is a schematic diagram of the structure of the device for the volume calibration of the standard container by the pVTt method proposed in the embodiment of the present invention;

FIG. 3 is a flowchart of a method for calibrating the volume of a standard container by the pVTt method proposed in an embodiment of the present invention.

Detailed ways

In the process of realizing this application, the principle of the conventional gas standard solution is shown in Figure 1, including a vacuum pump 1 for vacuuming, a stop valve 2 connecting the vacuum pump 1 and a standard container 3, and the standard container 3 contains a vacuum pump 1 for measuring The pressure sensor 4 and temperature sensor 6 of the standard container 3 are connected to the stop valve 2 6 , the quick connector 7 and the stop valve 3 8 of the standard container 3 and the high-pressure nitrogen cylinder 9 , the balance 10 and the balance tray 11 for weighing.

Under normal circumstances, nitrogen medium with a purity of 99.999% is generally selected, and its specific treatment method is as follows:

First, perform the cleaning procedure. Turn on the vacuum pump, pump out the air in the standard container, fill it with nitrogen, then use the vacuum pump to pump out the gas in the standard container, and then fill it with nitrogen, repeat this several times until the air in the standard container is considered to be swept away. Open the stop valve one, start the vacuum pump, pump out the nitrogen in the standard container, until the pressure in the standard container reaches the predetermined pressure p _e , close the stop valve one and the vacuum pump.

After the nitrogen temperature in the standard container is stable, the pressure _pe and temperature _Te are measured. Place the high pressure nitrogen cylinder on the balance and adjust the balance to balance. Connect the nitrogen bottle to the standard container, and open the second stop valve and the third stop valve, so that the nitrogen of the high-pressure nitrogen bottle is filled into the standard container. Then close stop valve two and stop valve three, and disconnect the quick connector. Add a substitute weight to the end of the balance where the high-pressure nitrogen bottle is placed to make the balance re-balance, and record the mass m ₁ of the substitute weight during the first nitrogen filling. Nitrogen charging is repeated until the kth time, the pressure in the standard container reaches the predetermined pressure, and in this way, m ₂ , m ₃ , ... m _k are obtained again. After the nitrogen temperature in the standard container is stable, its pressure P _f and temperature T _f are measured.

According to the above, the standard container is calibrated for the second time, the third time, and the nth time.

Then use the corresponding formula to calculate the standard volume value.

The inventor found that the disadvantages of the conventional gas standard scheme are as follows:

(1) After the nitrogen cylinder is deflated, its temperature drops sharply, so a layer of water is often condensed on the outer surface of the nitrogen cylinder. In this case, it is necessary to wait for the temperature of the nitrogen cylinder to return to the ambient temperature, and even to dry its surface by means of blowing, heating, etc., and then balance and weigh the balance. The waiting time is long, often a few cubic The total time required for gas calibration on a standard container of rice takes several days, and it is not easy to ensure the repeatability of calibration, so this weighing method greatly affects the calibration accuracy.

(2) Due to the low density of the gas medium, when weighing the high-pressure nitrogen cylinder, the net mass of the effective gas is much smaller than the tare of the nitrogen cylinder. Generally, the high-pressure nitrogen cylinder of 15MPa has a tare weight of about 50kg, while The gas mass is only about 5kg, and this phenomenon of "large mass and small weighing" is extremely detrimental to the accuracy of gas mass weighing.

In view of the above problems, the embodiments of the present application provide a device and method for calibrating the volume of a standard container by the pVTt method. The device includes a liquid nitrogen container for holding liquid nitrogen; a weighing device for weighing the liquid nitrogen container Equipment; pVTt method standard vessel connected to liquid nitrogen vessel. In the technical solution proposed in the embodiment of the present application, it is proposed to use the method based on liquid nitrogen weighing and liquid nitrogen gasification to carry out the gas standard, so as to convert the weighing of the gas mass into the weighing of the liquid medium, which reduces the difficulty of weighing and reduces the difficulty of weighing. Improved weighing accuracy. The solutions in the embodiments of the present application may be implemented in various computer languages, for example, the object-oriented programming language Java and the literal translation scripting language JavaScript, and the like.

In order to make the technical solutions and advantages of the embodiments of the present application more clear, the exemplary embodiments of the present application will be described in further detail below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present application, and Not all embodiments are exhaustive. It should be noted that the embodiments in the present application and the features of the embodiments may be combined with each other in the case of no conflict.

The embodiment of the present application proposes a device for calibrating the volume of a standard container by the pVTt method, as shown in FIG. 2 , including:

A liquid nitrogen container 2 for holding liquid nitrogen; the liquid nitrogen container contains a pressured valve 5, and an accumulation flowmeter 6 connected to the pressured valve 5 for measuring the accumulated flow; the liquid nitrogen container 2 contains a pressured valve 5 for measuring The pressure gauge 7 for the pressure of the liquid nitrogen container 2, and the thermometer 8 for measuring the temperature of the liquid nitrogen container 2; The connected gas flow pipeline 10; the liquid nitrogen container 2 includes a liquid nitrogen flow control valve 15 arranged in parallel with the gas flow control valve 9, and the liquid nitrogen flow control valve 15 is used to adjust the liquid nitrogen flow in the liquid nitrogen container 2; The nitrogen flow regulating valve 15 is provided on the liquid flow line 14 .

When in use, the liquid nitrogen container 2 is filled with liquid nitrogen 3 and nitrogen gas 4.

In the technical solution proposed in the embodiment of the present application, a pressure and temperature monitoring device is arranged on the top of the liquid nitrogen container, and the pressure and temperature of the gas in the container can be checked in real time.

In the embodiment of the present application, a pressured valve 5 is set between the accumulating flow meter 6 and the liquid nitrogen container 2 to set the upper limit of the pressure of the liquid nitrogen container. When the pressure in the liquid nitrogen container 2 is caused by the volatilization of the liquid nitrogen When it rises to the set value, the liquid nitrogen container is actively deflated and the amount of deflation is measured by the cumulative flowmeter at the rear, so as to ensure that the liquid nitrogen container 2 will not be overpressured.

Set up two overflow pipelines of liquid flow branch and gas flow branch, among which the liquid flow branch is the main overflow pipeline. When the gas flow control valve is closed, due to the self-generated pressurization of the liquid nitrogen container, the liquid nitrogen will flow from the top. The action of air pressure leads the liquid nitrogen into the liquid flow branch, and enters the vaporizer through the liquid chlorine flow control valve, the main valve of the container and the inlet valve of the vaporizer. When the gas circuit stop valve is opened, the liquid flow branch stops due to the balance of pressure. When it overflows, the gas will enter the vaporizer due to the internal pressure of the container, and the overflow and overflow of the liquid or air flow can be controlled by the cooperation of the three valves: the flow regulating valve, the gas flow regulating valve and the main valve of the container.

The liquid nitrogen container 2 includes a 2-container main valve 11 for controlling the liquid nitrogen container, and the container main valve 1 is respectively connected in series with the liquid nitrogen flow regulating valve 15 and the gas flow regulating valve 9 .

The apparatus comprises a weighing device 1 for weighing the liquid nitrogen container.

In the specific implementation, the required amount of liquid nitrogen can be calculated according to the volume design value of the standard container to be marked and the pressure value of the final gas standard state, and a liquid nitrogen container with a volume margin and a high-resolution electronic balance with a corresponding range are selected as the weighing equipment .

The pVTt method standard vessel 20 is connected to the liquid nitrogen vessel 2 through the vaporizer 16 for vaporizing the liquid nitrogen.

The vaporizer 16 is connected to the liquid nitrogen container 2 through the quick connector 13 and the vaporizer inlet valve 12. After the quick connector 13 is connected to the main valve 11 of the liquid nitrogen container 2, it is connected to the vaporizer through the vaporizer inlet valve 12. device 16.

The vaporizer 16 is connected to the standard vessel 20 through the instantaneous flowmeter 17 , the second quick connector 18 , and the standard vessel inlet valve 19 .

In the technical solution proposed in the embodiment of the present application, a quick connector 2 is set at the main valve of the container and the inlet of the vaporizer to quickly disconnect the weighing part and the vaporizer part, and the weighing part is independently weighed, so that it does not Influenced by external plumbing connections.

The standard container 20 includes a pressure sensor 21 for detecting the pressure of the standard container 20 and a temperature sensor 22 for detecting the temperature of the standard container 20; the standard container 20 is also connected to a vacuum pump 24 for evacuation through the standard container air release valve 25; the standard container A standard container air release valve 25 for opening the standard container 20 for air release is also provided on 20 .

In the technical solution proposed in the embodiment of the present application, the quick joint and pipeline between the main valve of the container and the inlet valve of the gasifier should be as short and small as possible to reduce the influence of the additional volume of the pipeline. The vaporizer is a water bath heat exchange system, and the coiled heat exchange pipeline is thin and long, which not only increases the heat exchange area but also minimizes the gas capacity, reducing the influence of the additional pipeline volume on the gas standard of the standard container. An instantaneous flow measurement device is installed after the vaporizer to monitor the gas flow into the standard container.

In the technical solution proposed in the embodiment of the present application, the liquid nitrogen container 2 adopts a vacuum interlayer insulation container, which can better avoid condensation or frost on the outer wall of the liquid nitrogen container due to the action of low temperature, and improve the weighing accuracy.

In the technical solution proposed in the embodiment of the present application, the size of the liquid nitrogen container 2 and the amount of liquid nitrogen are calculated according to the size and pressure of the standard container 20 to be marked, so as to avoid the problem of waste caused by too much or too little liquid nitrogen.

The liquid nitrogen weighing method adopts the weight substitution method, and combines the cumulative overflow mass obtained by the cumulative flowmeter to obtain the standard mass value. The cumulative flowmeter is used to measure the nitrogen overflow when the set pressure value is exceeded in the liquid nitrogen container. , the cumulative mass value is a small amount relative to the mass change of the overall liquid nitrogen, and this measurement method ensures the accuracy of mass weighing.

Based on the device shown in FIG. 2 , an embodiment of the present application also proposes a method for calibrating the volume of a standard container by the pVTt method, as shown in FIG. 3 , and its specific processing flow is as follows:

Step 31: Obtain the first pressure value and the first temperature value after the pressure and temperature in the standard container are stabilized before the standard container is inflated.

Inject liquid nitrogen into the liquid nitrogen container until it is full, the nitrogen at the top of the liquid nitrogen container is discharged to the outside of the liquid nitrogen container through the vaporizer and the second quick connector, and adjust the pressure of the pressure valve so that the pipeline where the pressure valve is located is pre-discharged When the pre-exhaust of all pipelines is completed and the self-evaporation rate of the liquid nitrogen container is uniform, connect the quick connector 2 in sequence, close the inlet valve of the vaporizer, close the main valve of the liquid nitrogen container, and open the inlet valve of the standard container; and disconnect the quick Connector 1, the user isolates the liquid nitrogen container from other equipment;

When the pressure and temperature in the standard container are stable, the first pressure value and the first temperature value of the standard container are obtained.

Step 32: Obtain the second pressure value and the second temperature value after the standard vessel is inflated and the pressure and temperature in the vessel are stabilized, as well as the weight mass value of the weighing device, the pipe section between the main vessel valve of the liquid nitrogen vessel and the inlet valve of the vaporizer The value of the first volume of venting; the cumulative flow rate indication on the liquid nitrogen container, the second volume of the pipe section between the gasifier inlet valve and the standard container inlet valve of the gasifier used to connect the standard container and the liquid nitrogen container value.

Step 33 , according to the first pressure value, the second pressure value, the mass value of the weight and the first volume value, determine the mass value of the vented nitrogen in the pipe section between the main valve of the container and the inlet valve of the gasifier.

Step 34: Determine the standard volume of the standard container according to the nitrogen mass value, the second volume value, the first temperature, the second temperature and the indication of the cumulative flow meter.

In the specific implementation, according to the following formula 1, determine the nitrogen mass value of the venting of the pipe section between the main valve of the container and the inlet valve of the gasifier:

Wherein, m _K is the nitrogen mass value, p _f is the second pressure value, p _e is the first pressure value, and V _K is the first volume value.

In the specific implementation: According to the following formula 2, determine the standard volume of the standard container:

Among them, V _N is the standard volume of the standard container; C _p ' is the pressure correction coefficient, C _θ ' is the temperature correction coefficient; p _N is the standard pressure of the standard container in the standard state, and Z _e is the nitrogen gas in the standard container before nitrogen filling Compression coefficient, Z _f is the nitrogen compression coefficient after nitrogen filling in the standard container, Z _N is the nitrogen compression coefficient of the standard container in the standard state, Z _N = _0.99978 ; Te is the first temperature, T _f is the second temperature, T _N is the standard temperature in the standard container in the standard state; ρ _N is the density of nitrogen in the standard state, ρ _N =1.1648kg/m3; C _b is the air buoyancy correction coefficient; m _b is the mass value of the weight; m _L is the cumulative flow indication; V _q is the second volume.

In the specific implementation, before injecting liquid nitrogen into the liquid nitrogen container, it also includes: calculating the required amount of liquid nitrogen according to the standard container volume design value and the pressure value of the final gas standard state; and turning on the vacuum pump to extract the air in the standard container ; And open the gas flow control valve on the liquid nitrogen container, the main valve of the container and the inlet valve of the vaporizer for connecting the liquid nitrogen container and the liquid nitrogen container, disconnect the quick connector two, and close the liquid nitrogen flow control valve.

Optionally, after obtaining the first pressure value and the first temperature value after the pressure and temperature in the standard container are stabilized before the standard container is inflated, before obtaining the second pressure value and the second temperature value after the standard container is inflated after the pressure and temperature are stabilized. , and also includes: adjusting the pressure of the pressure valve to the required multiple value of the gas standard pressure, clearing the accumulated flow meter when the indication value of the weighing device is stable, and obtaining the indication value of the weighing device; connecting the quick connectors in turn 1. Open the inlet valve of the vaporizer, nitrogen is charged into the standard container through the vaporizer, the flow rate of the intake air is monitored by the instantaneous flowmeter, and the opening of the liquid nitrogen flow control valve and the gas path control valve is adjusted to keep the gas volume entering the standard container. The set flow value, wherein the pressure in the liquid nitrogen container does not exceed the set value of the pressured valve; when the standard container pressure reaches the pressure value of the gas standard state, close the liquid nitrogen flow control valve and open the gas circuit control valve, Nitrogen is injected into the vaporizer. When the liquid nitrogen medium no longer exists in the circulation pipeline, close the main valve of the container, open the gas flow control valve and the liquid nitrogen flow control valve, and close the inlet valve of the vaporizer; disconnect the quick connector one, independent For liquid nitrogen container, when there is no flow overflow at the back pressure valve and the reading of the weighing device is stable, load the standard weight on the platform of the weighing device to the initial value before the gas standard.

A preferred implementation manner, the embodiment of the present application is based on the device shown in FIG. 2 , and provides a method for calibrating the volume of a standard container by the pVTt method. The pressure value is used to calculate the required amount of liquid nitrogen, and the liquid nitrogen container 2 with the volume margin and the high-resolution electronic balance of the corresponding range are selected as the weighing equipment. The specific processing flow is as follows:

Step 1: Turn on the vacuum pump, pump out the air in the standard container, fill it with nitrogen, and then use the vacuum pump to pump out the gas. Repeat this several times until the influence of the air in the standard container is considered negligible.

The second step is to clean the air.

As shown in Figure 2, connect the equipment and pipelines, open the gas flow control valve, the main valve of the container and the inlet valve of the vaporizer, disconnect the quick connector 2, and close the liquid nitrogen flow control valve.

Step 3: Pre-exhaust the pipeline.

Fill the liquid nitrogen container with liquid nitrogen to the full, so that the nitrogen at the top of the liquid nitrogen container is discharged to the outside through the vaporizer and the second quick connector, and adjust the pressure of the pressure valve to pre-exhaust the pipeline where the pressure valve is located. When the pre-exhausting of all pipelines is completed and the self-evaporation rate of the liquid nitrogen container is uniform, connect the quick connector two in sequence, close the inlet valve of the vaporizer, close the main valve of the liquid nitrogen container, and open the inlet valve of the standard container.

Step 4, disconnect the quick connector 1, so that the weighing part is independent from the influence of the connecting pipeline.

Step 5: After the pressure and temperature in the standard container are stabilized, measure and record the first pressure value and the first temperature value of the standard container.

The first pressure value is the initial pressure value of the standard container, and the first temperature value is the initial temperature value of the standard container.

In a specific implementation, the first pressure value is represented by pe, and the first temperature value is represented by T _{e .}

Step 6: Quickly adjust the pressure of the pressure valve to a value 1.2 times the required gas standard pressure. When the indication value of the weighing equipment is stable, clear the accumulated flow rate indication and record the indication value of the weighing equipment at this time.

Step 7, connect the quick connectors in sequence 1. Slowly open the inlet valve of the vaporizer, the nitrogen in the standard container is charged into the standard container through the vaporizer, the flow rate of the intake air is monitored by the instantaneous flowmeter, and the liquid nitrogen flow control valve and the gas path control valve are adjusted. The size of the opening can keep the gas volume entering the standard container at an appropriate flow value, and at the same time keep the pressure in the liquid nitrogen container not exceeding the set value of the pressure valve.

Step 8: When the pressure of the standard container is about to reach the pressure value of the gas standard state, close the liquid nitrogen flow control valve, open the gas path control valve with a certain opening, and only inject nitrogen into the gasifier, and there is no more liquid in the circulation pipeline. When nitrogen medium is used, close the main valve of the container, open the gas flow control valve and the liquid nitrogen flow control valve, and close the inlet valve of the vaporizer.

Step 9: Disconnect the quick connector 1, and make the weighing part independent again. When there is no flow overflow at the back pressure valve and the reading of the weighing device is stable, load the standard weight on the platform of the weighing device to the initial value before the gas standard. .

The mass value of the weight is represented by m _b , and the cumulative flow indication is represented by m _L.

Step 10: After the pressure and temperature in the standard container are stable, measure and record the pressure and temperature values of the standard container.

At this time, the pressure value of the standard container is taken as the second pressure value, represented by p _f , and the temperature value is taken as the second temperature value, represented by T _f .

Step 11: Obtain the vented volume value V _K of the pipe section between the main valve of the vessel and the inlet valve of the gasifier, and the value of the volume value V _q of the pipe section between the gasifier inlet valve and the standard vessel inlet valve by geometric measurement.

Among them, in order to facilitate the distinction and elaboration, in the above-mentioned step eleven, the volume value of the vented pipe section between the main valve of the container and the inlet valve of the gasifier is taken as the first volume value, which is represented by V _K , the inlet valve of the gasifier and the standard container The volume value of the pipe section between the inlet valves is used as the second volume value, which is represented by V _q .

Step 12: According to the following formula, determine the mass value of the vented nitrogen in the pipe section between the main valve of the vessel and the inlet valve of the gasifier:

Among them, m _K is the nitrogen mass value, p _f is the second pressure value, p _e is the first pressure value, V _K is the venting volume value of the pipe section between the main valve of the vessel and the inlet valve of the gasifier, that is, the first volume value , in cubic meters.

Determine the standard volume of the standard container according to the following formula:

Among them, V _N is the standard volume of the standard container, the unit is cubic meter; C _p ' is the pressure correction coefficient, C _θ ' is the temperature correction coefficient; p _N is the absolute pressure value of the standard state, p _N = _101325Pa ; Ze is the standard The nitrogen compression coefficient of the container before nitrogen filling, Z _f is the nitrogen compression coefficient of the standard container after nitrogen filling, Z _N is the nitrogen compression coefficient of the standard container in the standard state, Z _N = 0.99978; T _e is the first temperature, T _f is the second temperature, T _N is the standard temperature in the standard container in the standard state; ρ _N is the density of nitrogen in the standard state, ρ _N =1.1648kg/m3; C _b is the air buoyancy correction coefficient; m _b is The mass value of the weight; m _L is the nitrogen overflow monitored by the cumulative flowmeter during the gas standard process, that is, the cumulative flowmeter indication; V _q is the volume value of the pipe section between the inlet valve of the gasifier and the inlet valve of the standard container, that is, the first Two volumes.

Step 12: Repeat the above eleven steps six times, and take the average value:

According to the above steps, the standard container is measured 6 times and averaged, as shown in the following formula, to obtain the standard volume value of the standard container.

——标准容积的标准容积的测量结果，m³；V_i——第i次测量得到的标准容器的标准容积，m³。in,

——the measurement result of the standard volume of the standard volume, m ³ ; Vi —— the standard volume of the standard container obtained by the _i -th measurement, m ³ .

By adopting the technical solution proposed above in the embodiment of the present application, the disadvantage of large tare weight and small weighing can be avoided, and the standard container can be inflated by using one liquid nitrogen container, which avoids repeated tare removal by frequent replacement of gas exchange cylinders in the middle. The re-weighing step is beneficial to improve the weighing accuracy. After analysis, the mass weighing accuracy of the scheme combined with the weight substitution method can reach 0.005%, and the gas standard volume accuracy can reach 0.015%. Therefore, the accuracy of the standard container volume gas standard can be better improved. It avoids the lengthy gas standard process of the traditional gas standard method, also shortens the entire gas standard time, and also avoids the influence of other uncertain factors such as micro-leakage of each pipeline valve interface, which is also conducive to improving the accuracy of the gas standard. . Using liquid nitrogen gasification to pressurize the standard container to the standard pressure value at one time, the entire gas standard process can be shortened to within 8 hours, which is a great improvement over the traditional method and significantly improves the efficiency of the gas standard.

As will be appreciated by those skilled in the art, the embodiments of the present application may be provided as a method, a system, or a computer program product. Accordingly, the present application may take the form of an entirely hardware embodiment, an entirely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present application may take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, etc.) having computer-usable program code embodied therein.

The present application is described with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the present application. It will be understood that each process and/or block in the flowchart illustrations and/or block diagrams, and combinations of processes and/or blocks in the flowchart illustrations and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to the processor of a general purpose computer, special purpose computer, embedded processor or other programmable data processing device to produce a machine such that the instructions executed by the processor of the computer or other programmable data processing device produce Means for implementing the functions specified in a flow or flow of a flowchart and/or a block or blocks of a block diagram.

These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory result in an article of manufacture comprising instruction means, the instructions The apparatus implements the functions specified in the flow or flow of the flowcharts and/or the block or blocks of the block diagrams.

These computer program instructions can also be loaded on a computer or other programmable data processing device to cause a series of operational steps to be performed on the computer or other programmable device to produce a computer-implemented process such that The instructions provide steps for implementing the functions specified in the flow or blocks of the flowcharts and/or the block or blocks of the block diagrams.

While the preferred embodiments of the present application have been described, additional changes and modifications to these embodiments may occur to those skilled in the art once the basic inventive concepts are known. Therefore, the appended claims are intended to be construed to include the preferred embodiment and all changes and modifications that fall within the scope of this application.

Obviously, those skilled in the art can make various changes and modifications to the present application without departing from the spirit and scope of the present application. Thus, if these modifications and variations of the present application fall within the scope of the claims of the present application and their equivalents, the present application is also intended to include these modifications and variations.

Claims (11)

1. A device for calibrating the volume of a standard container by a pVTt method is characterized by comprising:

the liquid nitrogen container is used for containing liquid nitrogen, and comprises a pressure-controlled valve and an accumulation flowmeter which is connected with the pressure-controlled valve and is used for measuring the accumulated flow;

the weighing device is used for weighing the liquid nitrogen container;

the standard container is connected with the liquid nitrogen container through a gasifier for gasifying the liquid nitrogen, and comprises a pressure sensor for detecting the pressure of the standard container and a temperature sensor for detecting the temperature of the standard container.

2. The apparatus of claim 1,

the liquid nitrogen container comprises a pressure gauge for measuring the pressure of the liquid nitrogen container and a thermometer for measuring the temperature of the liquid nitrogen container;

the liquid nitrogen container comprises a gas path flow regulating valve for regulating gas path flow and an air flow pipeline connected with the gas path flow regulating valve;

the liquid nitrogen container comprises a liquid nitrogen flow regulating valve which is arranged in parallel with the gas circuit flow regulating valve, and the liquid nitrogen flow regulating valve is used for regulating the flow of liquid nitrogen in the liquid nitrogen container;

the liquid nitrogen container is provided with a container main valve used for controlling the liquid nitrogen container, and the container main valve is respectively connected with the liquid nitrogen flow regulating valve and the gas path flow regulating valve in series.

3. The apparatus of claim 1, wherein the vaporizer is connected to the liquid nitrogen container through a first quick connector and a vaporizer inlet valve, and the first quick connector is connected to the liquid nitrogen container and then connected to the vaporizer through a second quick connector.

4. The apparatus of claim 1, wherein the vaporizer is connected to a standard vessel via an instantaneous flow meter, a quick-connect second, and a standard vessel inlet valve, the instantaneous flow meter being connected to the vaporizer, the standard vessel inlet valve being disposed on the standard vessel.

5. The apparatus of claim 1,

the standard container is also connected with a vacuum pump for vacuumizing through a standard container air release valve;

and the standard container is also provided with a standard container deflation valve for opening the standard container to deflate.

6. A method for calibrating the volume of a standard container by a pVTt method is realized based on liquid nitrogen, and comprises the following steps:

acquiring a first pressure value and a first temperature value after the pressure and the temperature in the container are stable before the standard container is inflated;

acquiring a second pressure value and a second temperature value after the pressure and the temperature in the container are stable after the standard container is inflated, and a weight mass value of the weighing equipment and a first volume value of emptying of a pipe section between a container main valve and a gasifier inlet valve of the liquid nitrogen container; a cumulative flow meter reading on the liquid nitrogen container for a second volume value of a tube segment between a vaporizer inlet valve and a standard container inlet valve of a vaporizer connecting the standard container and the liquid nitrogen container;

determining the nitrogen mass value of the emptying of the pipe section between the main valve of the container and the inlet valve of the gasifier according to the first pressure value, the second pressure value, the mass value of the weight and the first volume value;

a standard volume of a standard vessel is determined based on the nitrogen mass value, the second volume value, the first temperature, the second temperature, and the cumulative flow meter indication.

7. The method of claim 6, wherein the mass value for nitrogen for the vent in the pipe section between the vessel header valve and the gasifier inlet valve is determined according to the following equation:

wherein m is_KIs the value of the mass of nitrogen, p_fIs the second pressure value, p_eIs a first pressure value, V_KIs the first volume value.

8. The method of claim 7, wherein the standard volume of the standard container is determined according to the following formula:

wherein, V_NIs the standard volume of a standard container; c_p' is a pressure correction factor, C_θ' is a temperature correction coefficient; p is a radical of_NIs the absolute pressure value in the standard state, p_N1111325 aa; standard pressure of standard container in standard state, Z_eIs the compression coefficient of nitrogen before filling nitrogen in a standard container, Z_fIs the compression coefficient of nitrogen gas, Z, after filling nitrogen in a standard container_NIs the nitrogen compression factor, Z, of a standard vessel in the standard state_N11.99978；T_eIs a first temperature; t is_fIs a second temperature; t is_NIs a standard state thermodynamic temperature value, T_N1273.15K；ρ_NIs the density of nitrogen in the standard state, p_N11.1648kg/m3；C_bIs the air buoyancy correction factor; m is_bIs the weight mass value; m is_LIs a cumulative flow meter reading; v_qIs the second volume.

9. The method of claim 6, wherein obtaining the first pressure value and the first temperature value after the pressure temperature in the vessel has stabilized before the standard vessel is inflated comprises:

injecting liquid nitrogen into the liquid nitrogen container to full, discharging nitrogen at the top in the liquid nitrogen container to the outside of the liquid nitrogen container through the gasifier and the quick connector II, adjusting the pressure of the pressure-controlled valve to pre-exhaust the pipeline where the pressure-controlled valve is located, and when the pre-exhaust of all the pipelines is finished and the self-volatilization speed of the liquid nitrogen container is uniform, sequentially connecting the quick connector II, closing an inlet valve of the gasifier, closing a main valve of the liquid nitrogen container and opening an inlet valve of a standard container; disconnecting the first quick connector, and isolating the liquid nitrogen container from other equipment by a user;

and when the pressure and the temperature in the standard container are stable, acquiring a first pressure value and a first temperature value of the standard container.

10. The method of claim 9, further comprising, prior to injecting liquid nitrogen into the liquid nitrogen container:

calculating the required liquid nitrogen amount according to the design value of the standard container volume and the pressure value of the final gas standard state; starting a vacuum pump to pump out air in the standard container; and opening a gas path flow regulating valve and a container main valve on the liquid nitrogen container and a gasifier inlet valve for connecting the liquid nitrogen container and the liquid nitrogen container, disconnecting the second quick connector and closing the liquid nitrogen flow regulating valve.

11. The method of claim 6, wherein after obtaining the first pressure value and the first temperature value after the pressure and temperature inside the container are stabilized before the standard container is inflated, and before obtaining the second pressure value and the second temperature value after the pressure and temperature inside the container are stabilized after the standard container is inflated, further comprising:

adjusting the pressure of the pressure-to-be-pressed valve to a required set air mark pressure multiple value, resetting the accumulated flow meter reading when the reading of the weighing equipment is stable, and obtaining the reading of the weighing equipment;

sequentially connecting a first quick connector and opening an inlet valve of a gasifier, filling nitrogen into a standard container through the gasifier, monitoring the size of the flow of inlet air by using an instantaneous flowmeter, and adjusting the opening sizes of a liquid nitrogen flow regulating valve and a gas path regulating valve to keep the amount of the air entering the standard container at a set flow value, wherein the pressure in the liquid nitrogen container does not exceed the set value of a pressure valve;

when the pressure of the standard container reaches the pressure value of the gas standard state, closing the liquid nitrogen flow regulating valve, opening the gas path regulating valve, injecting nitrogen into the gasifier, closing the container main valve, opening the gas path flow regulating valve and the liquid nitrogen flow regulating valve and closing the gasifier inlet valve when the liquid nitrogen medium no longer exists in the circulating pipeline;

and (4) disconnecting the quick connector I and the independent liquid nitrogen container, and loading a standard weight to the initial indicating value before the gas mark on the weighing equipment platform when no flow overflows at the back pressure valve and the reading of the weighing equipment is stable.

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