Low-temperature fluid mass flow calibration device and calibration method based on dynamic evaporation rate

Abstract

The invention provides a low-temperature fluid mass flow calibration device and method based on a dynamic evaporation rate, the low-temperature fluid mass flow calibration device based on the dynamic evaporation rate comprises a liquid collection container, a test pipeline, a flow regulating valve, a weighing module, a gas pipeline and a gas flowmeter, the liquid collection container is a closed container, the liquid collection container is used for collecting test fluid; one end of the test pipeline is communicated with an inner cavity of the liquid collection container, and the other end of the test pipeline is connected with a test fluid source; the flow regulating valve is used for regulating the flow of the test fluid in the test pipeline; the liquid collecting container is arranged on the weighing module, and the weighing module weighs the liquid collecting container and the test fluid in the liquid collecting container; one end of the gas pipeline communicates with the top of the inner cavity of the liquid collection container; the gas flow meter is used for detecting the gas flow in the gas pipeline. By means of the arrangement, the problem that errors are large when the mass flow rate of the low-temperature fluid is calibrated through a weighing method in the prior art is solved.

Description

Technical Field

[0001] This invention relates to the field of flow metering technology, and in particular to a cryogenic fluid mass flow rate calibration device and calibration method based on dynamic evaporation rate. Background Technology

[0002] High-precision cryogenic fluid mass flow rate measurement is a key technology in cutting-edge fields such as aerospace propulsion, liquefied natural gas trade, and large-scale scientific engineering projects. The accuracy of its measurement directly affects the performance and economic benefits of related systems. In flow measurement systems, the gravimetric method is recognized as the calibration method with the highest accuracy level. Its principle is to collect fluid over a certain period of time, measure the mass increment through a precision weighing system, and thus determine the average mass flow rate.

[0003] However, when applying the weighing method to cryogenic fluids such as liquid helium, the phase change evaporation of the fluid presents an insurmountable technical bottleneck. Due to factors such as environmental heat leakage and fluid injection disturbances, the cryogenic liquid inside the fluid collection tank will continuously vaporize, leading to excessive pressure within the tank. Since it is difficult to achieve a perfect seal in the fluid collection tank, excessive pressure can cause gas to escape through the tank's welds or structural connections. This results in the weighing system measuring a mass change rate that is not the true liquid inflow rate, but rather the difference between the inflow rate and the evaporation rate, leading to a significant error in the measured mass change rate.

[0004] To address the evaporation interference problem in gravimetric calibration applied to cryogenic fluids, some techniques employ a static evaporation rate correction method. This involves measuring the static evaporation rate before and after flow measurement and using the average value as the correction for the entire dynamic measurement process. This method assumes a constant evaporation rate, completely ignoring the drastic dynamic changes in evaporation rate caused by fluid impact, flash evaporation, and pressure fluctuations during fluid injection. The correction model deviates significantly from physical reality, resulting in a large error between the correction and the actual evaporation loss.

[0005] Therefore, how to solve the problem of large errors in calibrating the mass flow rate of cryogenic fluids using the weighing method has become an important technical problem for those skilled in the art. Summary of the Invention

[0006] This invention provides a calibration device and method for calibrating the mass flow rate of cryogenic fluids based on dynamic evaporation rate, in order to solve the problem of large errors in the calibration of the mass flow rate of cryogenic fluids using the weighing method in related technologies.

[0007] This invention provides a cryogenic fluid mass flow rate calibration device based on dynamic evaporation rate, comprising: The liquid collection container is a closed container used to collect test fluid. A test pipeline is used to connect to the mass flow meter to be calibrated. One end of the test pipeline is connected to the inner cavity of the liquid collection container, and the other end of the test pipeline is used to connect to the test fluid source. A flow regulating valve is installed in the test pipeline, and the flow regulating valve is used to regulate the flow rate of the test fluid in the test pipeline; A weighing module, wherein the liquid collection container is disposed on the weighing module, and the weighing module is used to weigh the liquid collection container and the test fluid inside it; A gas pipeline, one end of which is connected to the top of the inner cavity of the liquid collection container; A gas flow meter is installed in the gas pipeline and is used to detect the gas flow rate in the gas pipeline.

[0008] A cryogenic fluid mass flow rate calibration device based on dynamic evaporation rate according to the present invention further includes: A gas collection container, with the other end of the gas pipeline connected to the inner cavity of the gas collection container.

[0009] A cryogenic fluid mass flow rate calibration device based on dynamic evaporation rate according to the present invention further includes: The control system includes at least the weighing module and the gas flow meter, which are electrically connected to the control system. The control system collects the weighing data of the weighing module and the flow detection data of the gas flow meter at a preset frequency, and determines the mass flow rate calibration value of the test fluid in the test pipeline based on the weighing data, the flow detection data and a preset algorithm.

[0010] A cryogenic fluid mass flow rate calibration device based on dynamic evaporation rate according to the present invention further includes: A temperature sensing element is used to detect the temperature of the gas inside the liquid collection container; A pressure detection element is used to detect the pressure of the gas inside the liquid collection container; Both the temperature sensing element and the pressure sensing element are electrically connected to the control system. The control system also collects temperature detection data from the temperature sensing element and pressure detection data from the pressure sensing element at the preset frequency, and corrects the preset algorithm based on the temperature detection data and the pressure detection data.

[0011] According to the present invention, a cryogenic fluid mass flow rate calibration device based on dynamic evaporation rate is provided, wherein the gas flow meter includes one of a cryogenic ultrasonic gas flow meter, a thermal gas mass flow meter, and a cryogenic Coriolis gas mass flow meter.

[0012] According to the present invention, a cryogenic fluid mass flow rate calibration device based on dynamic evaporation rate is provided, wherein the weighing module includes a precision balance; Alternatively, the weighing module may include: A support platform is used to support the liquid collection container; A load cell is installed at the bottom of the support platform.

[0013] According to the present invention, a cryogenic fluid mass flow rate calibration device based on dynamic evaporation rate is provided, wherein the liquid collection container has at least one of a vacuum jacket and a multi-layer insulation layer.

[0014] The present invention also provides a method for calibrating the mass flow rate of cryogenic fluids based on dynamic evaporation rate, based on the aforementioned device for calibrating the mass flow rate of cryogenic fluids based on dynamic evaporation rate, wherein the method includes: Adjust the flow rate of the test fluid in the test pipeline until the reading of the mass flow meter to be calibrated is the target mass flow rate value; The fluid mass and gas flow rate are acquired at a first preset frequency, wherein the fluid mass is the mass of the test fluid in the liquid collection container and the gas flow rate is the flow rate of the gas in the gas pipeline. The mass change rate of the test fluid in the collection container and the gas mass flow rate in the gas pipeline are determined based on the fluid mass and the gas flow rate. The real-time actual mass flow rate of the test fluid in the test pipeline is determined based on the mass change rate and the gas mass flow rate. The real-time actual mass flow rate is subjected to time-weighted averaging to obtain the mass flow rate calibration value corresponding to the target mass flow rate value.

[0015] According to the present invention, a method for calibrating the mass flow rate of a cryogenic fluid based on dynamic evaporation rate, before adjusting the flow rate of the test fluid in the test pipeline until the reading of the mass flow meter to be calibrated is the target mass flow rate value, further includes: The cryogenic fluid mass flow rate calibration device based on dynamic evaporation rate is pre-cooled; The sealing performance of the cryogenic fluid mass flow rate calibration device based on dynamic evaporation rate was tested.

[0016] According to the present invention, a method for calibrating the mass flow rate of a cryogenic fluid based on a dynamic evaporation rate is provided, wherein precooling the cryogenic fluid mass flow rate calibration device based on the dynamic evaporation rate includes: A preset amount of test fluid is introduced into the liquid collection container to pre-cool the test pipeline and the inner cavity of the liquid collection container using the test fluid; The sealing test of the cryogenic fluid mass flow rate calibration device based on dynamic evaporation rate includes: Adjust the test pipeline to the cut-off state; Within a preset time period, the fluid mass and the gas flow rate are acquired at a second preset frequency. The mass change rate of the test fluid in the collection container and the gas mass flow rate in the gas pipeline are determined based on the fluid mass and the gas flow rate. The sealing performance of the cryogenic fluid mass flow rate calibration device based on the mass change rate is determined according to the mass change rate and the gas mass flow rate.

[0017] This invention provides a cryogenic fluid mass flow rate calibration device based on dynamic evaporation rate, comprising a collection container, a test pipeline, a flow regulating valve, a weighing module, a gas pipeline, and a gas flow meter. One end of the test pipeline is connected to the inner cavity of the collection container, and the other end is connected to a test fluid source. Liquid from the test fluid source can be injected into the collection container through the test pipeline, and the collection container is used to collect the test fluid. The flow regulating valve is located in the test pipeline and is used to regulate the flow rate of the test fluid in the test pipeline. The test pipeline is used to connect to the mass flow meter to be calibrated. The reading of the mass flow meter to be calibrated is the result of its measurement of the mass flow rate of the test fluid in the test pipeline. Changes in the flow rate of the test fluid in the test pipeline will cause changes in the reading of the mass flow meter to be calibrated. By adjusting the flow rate of the test fluid in the test pipeline, the mass flow meter to be calibrated can be calibrated at different mass flow rate points. The collection container is located in the weighing module, which is used to weigh the collection container and the test fluid inside it. One end of the gas pipeline connects to the top of the inner cavity of the liquid collection container, and a gas flow meter is installed in the gas pipeline. The liquid collection container is a closed container; after the test fluid inside evaporates, the gas can be discharged through the gas pipeline, and the gas flow meter is used to detect the gas flow rate in the gas pipeline. The mass of the test fluid in the liquid collection container and the gas flow rate in the gas pipeline are acquired at a preset frequency, and the mass change rate of the test fluid in the liquid collection container and the gas mass flow rate in the gas pipeline are calculated. According to the principle of mass conservation, the sum of the mass change rate of the test fluid in the liquid collection container and the gas mass flow rate in the gas pipeline is the mass flow rate of the test fluid injected into the liquid collection container, which is the calibration value of the mass flow rate of the test fluid in the test pipeline. By comparing this calibrated mass flow rate value with the reading of the mass flow meter to be calibrated, the measurement error of the mass flow meter to be calibrated can be determined, thus completing the calibration of the mass flow meter at one mass flow rate point. With this setup, when calibrating the mass flow meter to be calibrated using the cryogenic fluid mass flow rate calibration device based on dynamic evaporation rate provided by this invention, the gas flow meter can measure the dynamic evaporation of the test fluid in real time. The gas mass flow rate in the gas pipeline is the dynamic evaporation rate of the test fluid, which is the evaporation rate calculated by actual measurement. It comprehensively considers the influence of fluid impact, flash evaporation, pressure fluctuations, etc. on the evaporation rate during the injection of the test fluid, which helps to reduce calibration errors and improve calibration accuracy. It solves the problem of large errors in the calibration of the mass flow rate of cryogenic fluids using the weighing method in related technologies. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in this invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0019] Figure 1 This is a schematic diagram of the structure of the cryogenic fluid mass flow rate calibration device based on dynamic evaporation rate provided by the present invention.

[0020] Figure 2 This is a flowchart of the cryogenic fluid mass flow rate calibration method based on dynamic evaporation rate provided by the present invention.

[0021] Figure label: 1. Liquid collection container; 2. Test pipeline; 3. Flow regulating valve; 4. Weighing module; 5. Gas pipeline; 6. Gas flow meter; 7. Gas collection container; 8. Control module; 9. Temperature detection element; 10. Pressure detection element. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0023] The following is combined Figures 1 to 2 The present invention describes a cryogenic fluid mass flow rate calibration device based on dynamic evaporation rate.

[0024] like Figures 1 to 2 As shown, the cryogenic fluid mass flow rate calibration device based on dynamic evaporation rate provided in this embodiment of the invention includes a liquid collection container 1, a test pipeline 2, a flow regulating valve 3, a weighing module 4, a gas pipeline 5, and a gas flow meter 6.

[0025] Specifically, one end of the test pipe 2 is connected to the inner cavity of the liquid collection container 1, and the other end of the test pipe 2 is used to connect to the test fluid source. The liquid from the test fluid source can be injected into the liquid collection container 1 through the test pipe 2, and the liquid collection container 1 is used to collect the test fluid.

[0026] It should be noted that the test fluid mentioned above can be a cryogenic or conventional cryogenic fluid, including but not limited to liquid helium, liquid hydrogen, liquid nitrogen, liquid oxygen, liquefied natural gas, liquefied petroleum gas, etc., which are cryogenic or highly volatile fluids that may evaporate during the measurement process due to environmental heat leakage or pressure changes. In this embodiment, the cryogenic fluid liquid helium is used as an example.

[0027] A flow regulating valve 3 is installed in the test line 2 and is used to regulate the flow rate of the test fluid within the test line 2. The test line 2 is connected to the mass flow meter to be calibrated. The reading of the mass flow meter is its measurement of the mass flow rate of the test fluid within the test line 2. Changes in the flow rate of the test fluid within the test line 2 will cause changes in the reading of the mass flow meter to be calibrated. By adjusting the flow rate of the test fluid within the test line 2, the mass flow meter to be calibrated can be calibrated at different mass flow rate points.

[0028] A liquid collection container 1 is mounted on a weighing module 4, which is used to weigh the liquid collection container 1 and the test fluid inside it. One end of a gas pipeline 5 is connected to the top of the inner cavity of the liquid collection container 1, and a gas flow meter 6 is mounted on the gas pipeline 5. The liquid collection container 1 is a closed container; after the test fluid inside evaporates, the gas can be discharged through the gas pipeline 5, and the gas flow meter 6 is used to detect the gas flow rate in the gas pipeline 5.

[0029] The mass of the test fluid in the collection container 1 and the gas flow rate in the gas pipeline 5 are acquired at a preset frequency, and the mass change rate of the test fluid in the collection container 1 and the gas mass flow rate in the gas pipeline 5 are calculated. According to the principle of mass conservation, the sum of the mass change rate of the test fluid in the collection container 1 and the gas mass flow rate in the gas pipeline 5 is the mass flow rate of the test fluid injected into the collection container 1, which is the calibration value of the mass flow rate of the test fluid in the test pipeline 2. By comparing this calibrated mass flow rate value with the reading of the mass flow meter to be calibrated, the measurement error of the mass flow meter to be calibrated can be determined, thereby completing the calibration of the mass flow meter to be calibrated at one mass flow rate point.

[0030] With this configuration, when calibrating the mass flow meter to be calibrated using the cryogenic fluid mass flow rate calibration device based on dynamic evaporation rate provided in this embodiment of the invention, the gas flow meter can measure the dynamic evaporation of the test fluid in real time. The gas mass flow rate in the gas pipeline 5 is the dynamic evaporation rate of the test fluid, which is the evaporation rate calculated by actual measurement. It comprehensively considers the influence of fluid impact, flash evaporation, pressure fluctuations, etc. on the evaporation rate during the injection of the test fluid, which helps to reduce calibration error and improve calibration accuracy. It solves the problem of large error in the calibration of the mass flow rate of cryogenic fluid using the weighing method in related technologies.

[0031] It should be noted that the above calibration process is for calibrating the mass flow rate of the mass flow meter to be calibrated at one of the mass flow rate points. By adjusting the flow rate of the test fluid in the test pipeline 2 through the flow regulating valve 3 and repeating the above calibration process, the calibration of the remaining mass flow rate points can be completed, thereby obtaining multiple pairs of coordinates between the indicated value of the mass flow meter to be calibrated and the mass flow rate calibration value, and thus obtaining a calibration curve with the indicated value of the mass flow meter to be calibrated on the horizontal axis and the mass flow rate calibration value on the vertical axis.

[0032] The cryogenic fluid mass flow rate calibration device based on dynamic evaporation rate provided in this embodiment achieves accurate measurement of instantaneous flow rate, obtains high-resolution instantaneous real flow rate curves, and can be used for the study of dynamic characteristics of flow meters, thus expanding the functionality of the cryogenic fluid mass flow rate calibration device based on dynamic evaporation rate.

[0033] In this embodiment, the cryogenic fluid mass flow rate calibration device based on dynamic evaporation rate also includes a gas collection container 7, with the other end of the gas pipeline 5 connected to the inner cavity of the gas collection container 7. Gas in the liquid collection container 1 can enter the gas collection container 7 after passing through the gas pipeline 5.

[0034] The gas flowing through the gas flow meter 6 is collected by the gas collection container 7. This avoids the direct discharge of the test fluid into the external environment, effectively improving the safety and environmental friendliness of the calibration process. Especially when the test fluid is an expensive, flammable, or toxic gas, it not only enables the recycling of the test fluid and reduces testing costs but also eliminates safety hazards and environmental pollution. On the other hand, it also provides a stable back pressure environment for gas discharge, avoiding interference from atmospheric fluctuations on the measurement stability of the gas flow meter 6, further ensuring the accuracy of gas flow measurement.

[0035] In this embodiment, the cryogenic fluid mass flow rate calibration device based on dynamic evaporation rate also includes a control module 8, and at least the weighing module 4 and the gas flow meter 6 are electrically connected to the control module 8. The control module 8 can synchronously collect the weighing data of the weighing module 4 and the flow detection data of the gas flow meter 6 at a preset frequency. Through synchronous real-time acquisition, it can simultaneously obtain the net mass change in the liquid collection container 1 due to the combined effects of fluid injection and evaporation, as well as the amount of gas discharged due to phase change evaporation, providing real-time and corresponding basic data for subsequent accurate calculations.

[0036] The control module 8 can also determine the mass flow rate calibration value of the test fluid in the test pipeline 2 based on weighing data, flow detection data and preset algorithms.

[0037] The preset algorithm is based on the principle of mass conservation. It superimposes the mass change rate in the liquid collection container 1 measured by the weighing module 4 with the gas mass flow rate measured by the gas flow meter 6, so as to accurately calculate the real-time actual mass flow rate of the test fluid injected into the liquid collection container 1, which is the real-time actual mass flow rate of the test fluid in the test pipeline 2.

[0038] In a further embodiment, the cryogenic fluid mass flow rate calibration device based on dynamic evaporation rate also includes a temperature detection element 9 and a pressure detection element 10. The temperature detection element 9 is used to detect the temperature of the gas in the liquid collection container 1, and the pressure detection element 10 is used to detect the pressure of the gas in the liquid collection container 1. By combining the detection results of the temperature detection element 9 and the pressure detection element 10, the real-time thermodynamic state of the gas in the liquid collection container 1 can be determined.

[0039] Both the temperature sensing element 9 and the pressure sensing element 10 are electrically connected to the control module 8. The control module 8 can also collect the temperature detection data of the temperature sensing element 9 and the pressure detection data of the pressure sensing element 10 at a preset frequency, and correct the preset algorithm based on the temperature detection data and the pressure detection data.

[0040] The control module 8 is pre-loaded with cryogenic fluid property databases such as NIST REFPROP. By real-time monitoring of the temperature and pressure of the evaporating gas in the collection container 1, and combining this with cryogenic fluid property databases such as NIST REFPROP, key physical property parameters such as gas density, compressibility factor, and specific heat capacity can be calculated more accurately.

[0041] When calculating the gas mass flow rate based on the gas flow rate measured by gas flow meter 6, key physical property parameters such as gas density, compressibility factor, and specific heat capacity are involved. After determining the key physical property parameters such as gas density based on the gas temperature and pressure, the accuracy of the calculated gas mass flow rate can be improved, which means the accuracy of the obtained dynamic evaporation rate can be improved.

[0042] The temperature sensing element 9 is a thermometer, and the pressure sensing element 10 is a pressure gauge.

[0043] In this embodiment, the gas flow meter 6 includes at least one of a cryogenic ultrasonic gas flow meter, a thermal gas mass flow meter, and a cryogenic Coriolis gas mass flow meter.

[0044] The cryogenic ultrasonic gas flow meter measures volumetric flow rate. When using a cryogenic ultrasonic gas flow meter as the gas flow meter 6, it is necessary to correct and compensate for the gas temperature and pressure when determining the gas mass flow rate. Specifically, based on the gas density determined above according to the gas temperature and pressure, the volumetric flow rate is converted into mass flow rate in real time.

[0045] The thermal gas mass flow meter measures the mass flow rate. However, when using a thermal gas mass flow meter as the gas flow meter 6, it is necessary to correct and compensate for the gas temperature and pressure when determining the gas mass flow rate. Specifically, the output coefficient of the gas flow meter 6 is dynamically compensated based on the specific heat capacity determined above according to the gas temperature and pressure.

[0046] The low-temperature Coriolis gas mass flow meter measures the mass flow rate. When a low-temperature Coriolis gas mass flow meter is selected as the gas flow meter 6, no correction or compensation is required.

[0047] In some embodiments of the present invention, the weighing module 4 includes a precision balance. By using a precision balance, the mass of the liquid collection container 1 and the test fluid inside it can be measured with high precision, providing accurate weighing data for subsequent calculations, thereby ensuring the reliability of the entire calibration device as a high-accuracy calibration method.

[0048] In other embodiments of the present invention, the weighing module 4 includes a support platform and a weighing sensor.

[0049] The support platform is used to support the liquid collection container 1. The support platform provides stable support for the liquid collection container 1, ensuring stability during the weighing process and avoiding interference caused by shaking of the mass to be measured, thus creating the necessary conditions for the weighing sensor to perform accurate measurements.

[0050] The load cell is located at the bottom of the support platform. The load cell is used to detect the total mass of the support platform, the liquid collection container 1 and the test fluid inside in real time and accurately, and converts the mass signal into an electrical signal output. This facilitates continuous data acquisition and processing by the control module 8, thereby realizing accurate monitoring of dynamic changes in mass and providing a basis for calculating the mass change rate.

[0051] Specifically, at least two load cells are evenly arranged around the geometric center of the load-bearing platform to achieve accurate measurement of mass.

[0052] The liquid collection container 1 can be connected to the gas pipeline 5 and the test pipeline 2 through a flexible low-temperature corrugated pipe or a non-contact gas seal structure to achieve mechanical decoupling and minimize the impact of external connection pipelines on the balancing accuracy.

[0053] In this embodiment, the liquid collection container 1 has at least one of a vacuum jacket and a multi-layer heat insulation layer to provide excellent heat insulation performance for the liquid collection container 1, effectively reduce the transfer of external environmental heat to the interior of the liquid collection container 1, reduce environmental heat leakage, and reduce the amount of evaporation of the test fluid due to environmental heat leakage.

[0054] By reducing unnecessary phase changes at the source, not only can test fluid be saved, but a more stable and low-disturbance measurement environment can also be provided for accurately measuring the true mass change and dynamic evaporation rate caused by the injection of test fluid, ultimately improving the accuracy and stability of the entire calibration device.

[0055] Specifically, the above-mentioned liquid collection container 1 and collection container 7 can be, but are not limited to, double-walled high-vacuum insulated Dewar jars made of 304L stainless steel.

[0056] Multiple layers of insulation can also be wrapped around the outside of the test pipe 2 to provide excellent insulation performance for the test pipe 2, reduce the transfer of heat from the external environment to the inside of the test pipe 2, reduce environmental heat leakage, and further reduce the amount of evaporation of the test fluid due to environmental heat leakage.

[0057] On the other hand, the present invention also provides a calibration method for a cryogenic fluid mass flow rate calibration device based on dynamic evaporation rate provided in any of the above embodiments. The cryogenic fluid mass flow rate calibration method based on dynamic evaporation rate described below can be referred to in correspondence with the cryogenic fluid mass flow rate calibration device based on dynamic evaporation rate described above.

[0058] like Figure 2 As shown, the cryogenic fluid mass flow rate calibration method based on dynamic evaporation rate provided in this embodiment of the invention includes steps 110 to 150.

[0059] Step 110: Adjust the flow rate of the test fluid in the test pipeline until the reading of the mass flow meter to be calibrated is the target mass flow rate value.

[0060] When calibrating a mass flow meter, it is necessary to perform calibration at multiple mass flow rate points. The target mass flow rate value mentioned above is one of these mass flow rate points. By adjusting the flow rate in the test pipeline 2 to different values ​​using the flow regulating valve 3, the mass flow meter can be calibrated at different mass flow rate points.

[0061] Step 120: Obtain the fluid mass and gas flow rate according to the first preset frequency. The fluid mass is the mass of the test fluid in the liquid collection container, and the gas flow rate is the flow rate of the gas in the gas pipeline.

[0062] By synchronously collecting the mass change in the liquid collection container 1 and the gas flow rate discharged due to phase change evaporation, real-time and corresponding basic data are provided for the subsequent accurate calculation of the mass flow rate of the test fluid injected into the liquid collection container 1.

[0063] Step 130: Determine the rate of change of the test fluid in the collection container and the mass flow rate of the gas in the gas pipeline based on the fluid mass and gas flow rate.

[0064] The fluid mass is obtained at a first preset frequency, and multiple pairs of fluid mass and gas flow rate can be obtained within a preset time period.

[0065] The rate of change of the test fluid's mass can be obtained by differentiating the continuously collected fluid masses. Specifically, the interval between two consecutive fluid mass acquisitions is fixed, and the rate of change of the test fluid in collection container 1 can be calculated based on the ratio of the difference between the two fluid masses to the time interval.

[0066] The above fluid mass is used m This indicates that the fluid masses obtained in two consecutive measurements were respectively m 1 and m 2. The times of two consecutive fluid mass acquisitions are respectively t 1 and t 2. The rate of change of mass of the test fluid mentioned above is used... express, .

[0067] The first preset frequency can be 10 Hz. By acquiring data at a high frequency, the mass change rate of the test fluid is equivalent to the instantaneous change rate.

[0068] If the gas flow rate is measured using a volumetric flow meter, the gas mass flow rate needs to be calculated based on the gas density. During calibration, the temperature and pressure of the gas in the collection container 1 can also be acquired simultaneously to determine the real-time gas density and improve the accuracy of the calculated gas mass flow rate.

[0069] If the gas flow rate is measured by a mass flow meter, no conversion is required. It should be noted that, to improve the accuracy of the gas mass flow rate, in some cases, the temperature and pressure of the gas in the collection container 1 can be simultaneously acquired during calibration to determine the specific heat capacity of the gas, and dynamic compensation can be performed based on the specific heat capacity.

[0070] Gas mass flow rate q b ( t )express.

[0071] Step 140: Determine the real-time actual mass flow rate of the test fluid in the test pipeline based on the mass change rate and the gas mass flow rate.

[0072] This step is based on the principle of mass conservation, and the mass change rate measured by the weighing module 4 is superimposed with the dynamic evaporation rate measured by the gas flow meter 6.

[0073] The steps 120 and 130 above obtain multiple mass change rates and gas mass flow rates corresponding to different times. First, the average of these multiple mass change rates is calculated to obtain... The average value of multiple gas mass flow rates is then calculated to obtain... .

[0074] The real-time actual mass flow rate of the test fluid in the aforementioned test pipeline 2 is used q ( t ) indicates that .

[0075] Step 150: Perform time-weighted averaging on the real-time actual mass flow rate to obtain the mass flow rate calibration value corresponding to the target mass flow rate value.

[0076] When the control module 8 acquires sufficient data or the liquid level in the collection container 1 reaches the preset upper limit, it adjusts the flow regulating valve 3 to the shut-off state to stop injecting test fluid into the collection container 1. Then, the control module 8 performs time-weighted averaging on the real-time actual mass flow rate for data processing.

[0077] Specifically, the weighted average processing involves integrating each of the above real-time actual quality flow rates over a preset time period and then calculating the average value.

[0078] The preset time period is the calibration time, denoted by T. The mass flow calibration value corresponding to the target mass flow rate is used as... q Indicate, then .

[0079] The derivation process of the beneficial effects of the cryogenic fluid mass flow rate calibration method based on dynamic evaporation rate in this embodiment of the invention is largely similar to the derivation process of the beneficial effects of the cryogenic fluid mass flow rate calibration device based on dynamic evaporation rate described above, so it will not be repeated here.

[0080] In this embodiment of the invention, before adjusting the flow rate of the test fluid in the test pipeline 2 to the target mass flow rate value, it is necessary to pre-cool the cryogenic fluid mass flow rate calibration device based on dynamic evaporation rate and test the sealing performance of the cryogenic fluid mass flow rate calibration device based on dynamic evaporation rate.

[0081] The purpose of pre-cooling the cryogenic fluid mass flow rate calibration device based on dynamic evaporation rate is to lower the temperature of the test pipeline 2 and the liquid collection container 1 to near the temperature of the test fluid in advance. This effectively reduces the violent evaporation and phase change of the cryogenic fluid caused by temperature difference at the beginning of calibration, creates a stable thermodynamic environment for subsequent flow measurement, avoids huge measurement errors caused by cooling and heat absorption in the initial stage, and improves the stability and accuracy of calibration.

[0082] Testing the sealing performance of the cryogenic fluid mass flow rate calibration device based on dynamic evaporation rate ensures that no test fluid leaks into the environment through paths other than the gas pipeline 5 during calibration, and also prevents external air from entering the calibration device. This guarantees that all test fluid entering the collection container 1 is measured by the weighing module 4 and the gas flow meter 6, ensuring the authenticity and reliability of the calibration results calculated based on the principle of mass conservation, and avoiding systematic errors caused by leakage.

[0083] In this embodiment, when precooling the cryogenic fluid mass flow rate calibration device based on dynamic evaporation rate, a preset amount of test fluid can be introduced into the liquid collection container 1 to precool the test pipeline 2 and the inner cavity of the liquid collection container 1 using the sensible heat and latent heat of vaporization of the test fluid, and to discharge the generated gas.

[0084] After the temperature of the cryogenic fluid mass flow rate calibration device based on dynamic evaporation rate stabilizes, the sealing performance of the device is tested. The test steps include steps 101 to 104.

[0085] Step 101: Adjust the test pipeline to the cut-off state.

[0086] Adjust the flow regulating valve 3 to the fully closed state, so that the test pipeline 2 is in the cut-off state, stopping the injection of test fluid into the liquid collection container 1. The entire system is in a closed state, with only pure static evaporation caused by ambient heat leakage. Constructing the cryogenic fluid mass flow rate calibration device based on dynamic evaporation rate into a closed system provides the necessary prerequisite for subsequent accurate determination of whether mass leakage exists.

[0087] Step 102: Within a preset time period, obtain the fluid mass and gas flow rate at a second preset frequency.

[0088] Step 103: Determine the rate of change of the test fluid in the collection container and the mass flow rate of the gas in the gas pipeline based on the fluid mass and gas flow rate.

[0089] By monitoring these two key parameters in real time, the mass change within the closed system can be directly quantified. Under ideal sealing conditions, the rate of mass reduction caused by natural evaporation in the liquid collection container 1 due to factors such as environmental heat leakage should theoretically be equal to the mass flow rate of the gas discharged through the gas pipeline 5.

[0090] Step 104: Determine the sealing performance of the cryogenic fluid mass flow rate calibration device based on the mass change rate and gas mass flow rate.

[0091] By comparing the two independent measurements, the rate of change of mass and the gas mass flow rate, it is possible to accurately and quantitatively determine whether a leak exists in the device and assess the severity of the leak. If the two values ​​are essentially equal but opposite in sign, it indicates that the device is well-sealed; if the rate of change of mass is significantly greater than the gas mass flow rate, it indicates that there is an unmeasured leak.

[0092] This testing step can effectively identify potential equipment malfunctions before formal calibration, avoid major systemic deviations in calibration results due to leakage, and fundamentally ensure the reliability of the entire calibration work and the validity of the final data.

[0093] After calibration, the test fluid collected in collection container 1 evaporates naturally and is then collected in gas collection container 7 via gas pipeline 5 and gas flow meter 6 for recycling, ensuring operational safety and environmental protection. The system then naturally warms up to ambient temperature in preparation for the next calibration task.

[0094] In summary, the cryogenic fluid mass flow rate calibration device and calibration method based on dynamic evaporation rate provided in this embodiment of the invention introduces real-time direct measurement of dynamic evaporation rate to replace model estimation, thereby achieving precise decoupling between the mass flow rate of the test fluid injected into the collection container 1 and the dynamic evaporation rate, fundamentally eliminating the error introduced by dynamic evaporation, and improving the calibration accuracy of the cryogenic fluid mass flow rate calibration device based on dynamic evaporation rate.

[0095] Moreover, it enables accurate measurement of instantaneous mass flow rate, expands the functionality of the calibration device, and can obtain high-resolution instantaneous real flow curves for the study of flow meter dynamic characteristics.

[0096] A self-diagnostic system with a closed data loop has also been built, which improves the reliability of the calibration device. By comparing parameters such as fluid quality changes and gas quality in real time, the system status can be monitored in real time, and faults such as vacuum leaks can be detected immediately, resulting in high reliability.

[0097] In addition, it simplifies the measurement process and improves calibration efficiency, integrating multiple discrete steps before, during, and after measurement in traditional methods into a continuous and automated measurement and calculation process, which is easy to operate.

[0098] It should be noted that the cryogenic fluid mass flow rate calibration device based on dynamic evaporation rate provided in this embodiment can be used as an independent, high-level metrological calibration device for periodically calibrating other secondary flow standards or field flow meters. Alternatively, it can be designed as an online, compact module and integrated into a large-scale cryogenic fluid transport system for real-time online calibration and verification of flow measurements at critical trade junctions, thereby greatly improving the system's reliability and the credibility of its metrological measurements.

[0099] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A cryogenic fluid mass flow rate calibration device based on dynamic evaporation rate, characterized in that, include: The liquid collection container (1) is a closed container used to collect test fluid; Test line (2) is used to connect to the mass flow meter to be calibrated. One end of the test line (2) is connected to the inner cavity of the liquid collection container (1), and the other end of the test line (2) is used to connect to the test fluid source. A flow regulating valve (3) is installed in the test pipeline (2), and the flow regulating valve (3) is used to regulate the flow rate of the test fluid in the test pipeline (2); Weighing module (4), the liquid collection container (1) is disposed on the weighing module (4), the weighing module (4) is used to weigh the liquid collection container (1) and the test fluid inside it; Gas pipeline (5), one end of which is connected to the top of the inner cavity of the liquid collection container (1); A gas flow meter (6) is installed in the gas pipeline (5) and is used to detect the gas flow rate in the gas pipeline (5).

2. The cryogenic fluid mass flow rate calibration device based on dynamic evaporation rate according to claim 1, characterized in that, Also includes: The gas collection container (7) has its other end connected to the inner cavity of the gas pipeline (5).

3. The cryogenic fluid mass flow rate calibration device based on dynamic evaporation rate according to claim 1, characterized in that, Also includes: The control module (8) is electrically connected to at least the weighing module (4) and the gas flow meter (6). The control module (8) collects the weighing data of the weighing module (4) and the flow detection data of the gas flow meter (6) at a preset frequency, and determines the mass flow rate calibration value of the test fluid in the test pipeline (2) based on the weighing data, the flow detection data and the preset algorithm.

4. The cryogenic fluid mass flow rate calibration device based on dynamic evaporation rate according to claim 3, characterized in that, Also includes: Temperature detection element (9) is used to detect the temperature of the gas inside the liquid collection container (1); Pressure detection element (10) is used to detect the pressure of the gas inside the liquid collection container (1); The temperature detection element (9) and the pressure detection element (10) are both electrically connected to the control module (8). The control module (8) also collects the temperature detection data of the temperature detection element (9) and the pressure detection data of the pressure detection element (10) according to the preset frequency, and corrects the preset algorithm based on the temperature detection data and the pressure detection data.

5. The cryogenic fluid mass flow rate calibration device based on dynamic evaporation rate according to claim 1, characterized in that, The gas flow meter (6) includes one of a cryogenic ultrasonic gas flow meter (6), a thermal gas mass flow meter, and a cryogenic Coriolis gas mass flow meter.

6. The cryogenic fluid mass flow rate calibration device based on dynamic evaporation rate according to claim 1, characterized in that, The weighing module (4) includes a precision balance; Alternatively, the weighing module (4) may include: A support platform is used to support the liquid collection container (1). A load cell is installed at the bottom of the support platform.

7. The cryogenic fluid mass flow rate calibration device based on dynamic evaporation rate according to claim 1, characterized in that, The liquid collection container (1) has at least one of a vacuum jacket and a multilayer heat insulation layer.

8. A method for calibrating the mass flow rate of cryogenic fluids based on dynamic evaporation rate, characterized in that, Based on the cryogenic fluid mass flow rate calibration device based on dynamic evaporation rate as described in any one of claims 1 to 7, the cryogenic fluid mass flow rate calibration method based on dynamic evaporation rate includes: Adjust the flow rate of the test fluid in the test pipeline until the reading of the mass flow meter to be calibrated is the target mass flow rate value; The fluid mass and gas flow rate are acquired at a first preset frequency, wherein the fluid mass is the mass of the test fluid in the liquid collection container and the gas flow rate is the flow rate of the gas in the gas pipeline. The mass change rate of the test fluid in the collection container and the gas mass flow rate in the gas pipeline are determined based on the fluid mass and the gas flow rate. The real-time actual mass flow rate of the test fluid in the test pipeline is determined based on the mass change rate and the gas mass flow rate. The real-time actual mass flow rate is subjected to time-weighted averaging to obtain the mass flow rate calibration value corresponding to the target mass flow rate value.

9. The method for calibrating the mass flow rate of cryogenic fluids based on dynamic evaporation rate according to claim 8, characterized in that, The process of adjusting the flow rate of the test fluid in the test pipeline until the reading of the mass flow meter to be calibrated is the target mass flow rate value also includes: The cryogenic fluid mass flow rate calibration device based on dynamic evaporation rate is pre-cooled; The sealing performance of the cryogenic fluid mass flow rate calibration device based on dynamic evaporation rate was tested.

10. The method for calibrating the mass flow rate of cryogenic fluids based on dynamic evaporation rate according to claim 9, characterized in that, The precooling of the cryogenic fluid mass flow rate calibration device based on dynamic evaporation rate includes: A preset amount of test fluid is introduced into the liquid collection container to pre-cool the test pipeline and the inner cavity of the liquid collection container using the test fluid; The sealing test of the cryogenic fluid mass flow rate calibration device based on dynamic evaporation rate includes: Adjust the test pipeline to the cut-off state; Within a preset time period, the fluid mass and the gas flow rate are acquired at a second preset frequency. The mass change rate of the test fluid in the collection container and the gas mass flow rate in the gas pipeline are determined based on the fluid mass and the gas flow rate. The sealing performance of the cryogenic fluid mass flow rate calibration device based on the mass change rate is determined according to the mass change rate and the gas mass flow rate.

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