An apparatus and method for cryogenic liquid flowmeter testing

Abstract

The application provides a device and method for cryogenic liquid flowmeter test, which comprises a main liquid storage tank, a liquid measuring tank I, a liquid measuring tank II, a hydraulic pump, valves and a control system; the main liquid storage tank is connected with three branches through a main pipeline, two branches far away from the main liquid storage tank are respectively connected with the liquid measuring tank I and the liquid measuring tank II in one-to-one correspondence, and the remaining branch is connected with the main liquid storage tank; valves are arranged on the three branches; a cryogenic liquid flowmeter to be tested is arranged on the main pipeline, and hydraulic pumps are arranged on both sides of the cryogenic liquid flowmeter to be tested; the liquid measuring tank I and the liquid measuring tank II are respectively connected with the main liquid storage tank through return liquid pipelines, and valves are arranged on the two return liquid pipelines; the control system is used for controlling the valve switching to realize pipeline precooling, liquid inflow or outflow of the liquid measuring tank I and the liquid measuring tank II and adjustment of the hydraulic pump. The application can realize high-precision test of the cryogenic liquid flowmeter, simultaneously realize liquid circulation and recovery, and reduce test cost.

Description

Technical Field

[0001] This invention relates to the field of cryogenic flow measurement technology, and specifically to an apparatus and method for testing cryogenic liquid flow meters. Background Technology

[0002] Cryogenic liquids (such as liquid nitrogen, liquid oxygen, and liquefied natural gas) are increasingly widely used in energy, chemical, and aerospace industries, and the accuracy of their flow measurement directly affects the safety, stability, and economy of process operation. To ensure the accuracy of cryogenic flow meters, regular calibration is necessary. However, due to the characteristics of cryogenic liquids, such as easy evaporation, specific temperature ranges, and stringent storage and transportation requirements, traditional calibration methods have many limitations in practical applications.

[0003] Currently, common methods for calibrating cryogenic flow meters mainly include: 1. Static Weighing Method: This method involves weighing the cryogenic liquid collected in a container using a balance and calculating the flow rate based on time parameters. This method is cumbersome, requiring interruptions in the process for liquid collection and weighing. Furthermore, the cryogenic liquid experiences significant evaporation losses during transfer and weighing, introducing substantial errors.

[0004] 2. Volumetric method: This method uses a standard container of known volume (such as a calibration tank) for calibration, and calculates the flow rate by measuring the time it takes for the liquid to fill the fixed volume. This method requires continuous liquid discharge to complete multiple measurements, and the liquid cannot be recycled, resulting in significant waste of cryogenic liquid and high operating costs.

[0005] 3. Online Comparison Method: The standard flow meter and the flow meter under test are connected in series in the pipeline, and calibration is achieved by comparing their readings. Although online measurement is possible, the standard flow meter itself is expensive, and its reliability decreases under long-term low-temperature conditions, requiring frequent maintenance or recalibration, which increases the cost and complexity of use.

[0006] The existing methods mentioned above generally suffer from the following common problems: the testing operation is complex, the cycle is long, and the efficiency is low; the utilization rate of cryogenic liquid is low, resulting in serious waste and poor economic efficiency; liquid evaporation leads to insufficient stability of test data, affecting calibration accuracy; and there is a lack of continuous and automated testing schemes, making it difficult to meet the needs of modern industry for efficient and accurate calibration.

[0007] Therefore, there is an urgent need to develop a low-temperature flow meter testing device and method to overcome the shortcomings of existing technologies and improve calibration efficiency, accuracy and economy. Summary of the Invention

[0008] In view of this, the present invention provides an apparatus and method for testing cryogenic liquid flow meters, which can achieve high-precision testing of cryogenic liquid flow meters, while realizing liquid circulation and recovery, and reducing testing costs.

[0009] The technical solution adopted in this invention is as follows: An apparatus for testing cryogenic liquid flow meters includes a main storage tank, a measuring tank I, a measuring tank II, a hydraulic pump, valves, and a control system. The main liquid storage tank is connected to three branch lines via a main pipeline. Two of these branch lines, located away from the main liquid storage tank, are respectively connected to measuring tank I and measuring tank II. The remaining branch line is connected to the main liquid storage tank. Each of the three branch lines is equipped with a valve. A cryogenic liquid flow meter is installed on the main pipeline, and hydraulic pumps are installed on both sides of the cryogenic liquid flow meter. Measuring tank I and measuring tank II are both connected to the main liquid storage tank via return lines, and both return lines are equipped with valves. The control system is used to control valve switching to achieve pipeline precooling, liquid inlet or outlet of liquid tank I and liquid tank II, and to regulate the hydraulic pump.

[0010] Furthermore, the main liquid storage tank has a U-shaped cross-section, and the main pipeline is located on the protruding parts on both sides of the U-shape, so that the outlet of the remaining branch pipeline and the inlet of the main pipeline are located on both sides of the main liquid storage tank. The cryogenic liquid flow meter to be tested and the hydraulic pumps on both sides are located on the pipeline between the two protrusions; the main pipeline located in the main storage tank is above the liquid level.

[0011] Furthermore, the volumetric tank I and volumetric tank II are located on the same side of the main storage tank, and the valves on the three branches are at the same horizontal height.

[0012] Furthermore, the device also includes two liquid level sensors, which are used to monitor the liquid level in volumetric tank I and volumetric tank II, respectively.

[0013] The present invention also provides a method for testing cryogenic liquid flow meters, using the above-described apparatus for testing cryogenic liquid flow meters, and the method steps are as follows: Step 1: Under the control of the control system, close the valves on the branch lines connected to measuring tank I and measuring tank II, as well as the valves on the two return lines, and open the valves on the remaining branch lines; start the two hydraulic pumps to allow the cryogenic liquid to flow through the measured cryogenic liquid flow meter into the main storage tank, thereby achieving pipeline precooling; Step 2: Close the valves on the remaining branches and open the valve on the branch connected to the measuring tank I, so that the cryogenic liquid flows through the measured cryogenic liquid flow meter into the measuring tank I. The measured cryogenic liquid flow meter records the instantaneous flow rate in real time and accumulates the flow rate data. When the measuring tank I reaches the set liquid level, close the valve on the branch connected to the measuring tank I. Step 3: Open the valve on the return pipe connecting volumetric liquid tank I and the main storage tank to return the liquid in volumetric liquid tank I to the main storage tank; after the liquid level change in volumetric liquid tank I has been measured, close the valve on the return pipe connecting volumetric liquid tank I and the main storage tank, and simultaneously open the valve on the branch pipe connected to volumetric liquid tank II to allow the cryogenic liquid to flow through the cryogenic liquid flow meter being measured into volumetric liquid tank II. The cryogenic liquid flow meter being measured records the instantaneous flow rate in real time and accumulates the flow rate data; when volumetric liquid tank II reaches the set liquid level, close the valve on the branch pipe connected to volumetric liquid tank II. Step 4: Open the valve on the return line connecting the volumetric liquid tank II and the main storage tank to drain the liquid in the volumetric liquid tank II back to the main storage tank; after the liquid level change in the volumetric liquid tank II has been discharged, close the valve on the return line connecting the volumetric liquid tank II and the main storage tank. Step 5: Repeat steps 2 to 4, alternating between volumetric tank I and volumetric tank II, to achieve continuous measurement of cryogenic liquids; Step six: Compare the cumulative flow data of the cryogenic liquid flow meter under test with the standard volume or mass of measuring tank I or measuring tank II; calculate the error of the cryogenic liquid flow meter under test by comparison and evaluate its accuracy.

[0014] Furthermore, the hydraulic pump was adjusted and tested multiple times to obtain calibration curves under different flow rates and pressure conditions.

[0015] Beneficial effects: 1. This invention employs alternating measurement with dual liquid tanks. While liquid tank I is being filled, liquid tank II can be emptied and recycled, thereby ensuring the continuity of the testing process and fundamentally reducing the interference of factors such as temperature fluctuations, flow field instability, and phase changes on the testing accuracy. This provides a reliable guarantee for the accurate calibration and performance evaluation of cryogenic liquid flow meters.

[0016] 2. In this invention, the measuring tank I and the measuring tank II are located on the same side of the main liquid storage tank, which reduces the length of the pipeline exposed to the outside and reduces the impact of temperature on the liquid in the pipeline.

[0017] 3. In this invention, the outlet of the remaining branch (as a return pipeline) and the inlet of the main pipeline are located on opposite sides of the main storage tank. This fundamentally avoids direct collision, short circuit, or vortex formation between the return liquid and the filling liquid within the tank. The flow field inside the main storage tank is free from abrupt changes and interference, and the liquid velocity and flow rate output from the drain port are stable, providing ideal steady-state flow field conditions for flow meter testing and completely solving the measurement error caused by flow field instability. It also avoids the problem of uneven liquid temperature distribution within the tank caused by the mixing of return liquid and filling liquid in local areas when the outlet of the remaining branch and the inlet of the main pipeline are arranged on the same side, forming a local temperature gradient (such as a sudden temperature rise near the inlet and a sudden temperature drop near the return outlet). This further ensures the accuracy of the test. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the device composition of the present invention.

[0019] Among them, 1-main storage tank, 2-volume tank I, 3-volume tank II, 4-cryogenic liquid flow meter to be tested, 5-main pipeline, 6-hydraulic pump A, 7-hydraulic pump B, 8-valve I, 9-valve II, 10-valve III, 11-valve IV, 12-valve V. Detailed Implementation

[0020] The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0021] This invention provides a device for testing cryogenic liquid flow meters, suitable for the measurement and calibration of cryogenic fluids such as liquid nitrogen, liquid helium, and liquefied natural gas (LNG). The device includes a main storage tank 1, a measuring tank I 2, a measuring tank II 3, a hydraulic pump, valves, and a control system. The internal volumes of measuring tank I 2 and measuring tank II 3 are calibrated and used to collect the mass or volume of the cryogenic liquid flowing through them.

[0022] The main liquid storage tank 1 is used to store cryogenic liquids and is equipped with a pressure relief port to regulate the internal pressure and ensure stable liquid output.

[0023] The main storage tank 1 is connected to three branches via the main pipeline 5. The ends of two branches away from the main storage tank 1 are respectively connected to the measuring tank I2 and measuring tank II3. The remaining branch (as a return pipeline) is connected to the main storage tank 1. Each of the three branches is equipped with a valve. The valve on the branch connected to measuring tank I2 is valve II9; the valve on the branch connected to measuring tank II3 is valve III10; and the valve on the return pipeline is valve I8.

[0024] The main pipeline 5 is equipped with a cryogenic liquid flow meter 4 to be tested. Hydraulic pumps, namely hydraulic pump A6 and hydraulic pump B7, are installed on both sides of the cryogenic liquid flow meter 4 to regulate the flow rate and pressure of the liquid in the pipeline and simulate the flow rate under different working conditions. The measuring tanks I2 and II3 are connected to the main storage tank 1 through the return liquid pipeline, thereby forming a cryogenic liquid circulation loop.

[0025] Both return lines are equipped with valves. The valve on the return line connecting the measuring tank I2 to the main storage tank 1 is valve IV11, and the valve on the return line connecting the measuring tank II3 to the main storage tank 1 is valve V12.

[0026] The control system is used to control valve switching to achieve pipeline precooling, liquid inlet or outlet of liquid measuring tank I2 and liquid measuring tank II3, and to regulate the hydraulic pump.

[0027] In one embodiment, the outlet of the remaining branch (return pipeline) and the inlet of the main pipeline 5 are located on the same side of the main storage tank 1, and the cryogenic liquid flow meter 4 to be tested is installed on the main pipeline 5 on this side. The hydraulic pump A6 and the hydraulic pump B7 are respectively installed at both ends of the cryogenic liquid flow meter 4 to be tested.

[0028] In this embodiment, as Figure 1 As shown, the main storage tank 1 has a U-shaped cross-section. The main storage tank 1 can be a cylinder with a cylindrical groove penetrating the end face inside, or it can be a cuboid with a through groove penetrating opposite end faces at the top. The main pipeline 5 is located on the protruding parts on both sides of the U-shape, so that the outlet of the remaining branch (return pipeline) and the inlet of the main pipeline 5 are located on opposite sides of the main storage tank 1. The cryogenic liquid flow meter 4 under test and the hydraulic pumps on both sides are located on the pipeline between the two protruding parts. The main pipeline 5, located inside the main storage tank 1, is above the liquid surface inside the tank. This optimizes the flow field distribution, eliminates mutual interference between fluids, ensures steady-state flow, and achieves uniform heat exchange and temperature distribution of the cryogenic liquid inside the tank. It eliminates instantaneous pressure fluctuations, prevents nonlinear measurement errors caused by phase changes, further ensures the continuity of the testing process, and fundamentally reduces the generation and accumulation of testing errors, enabling efficient, accurate, and continuous testing of the cryogenic flow meter.

[0029] Preferably, measuring tanks I2 and II3 are located on the same side of the main storage tank 1. Valves I8, II9, and III10 are located at the same horizontal height. Installing them at the same horizontal height ensures that the local resistance loss generated by the fluid flowing through these three branch valve sections is basically the same when the valves are fully open. When switching valves, the consistent valve resistance makes the fluid flow state (such as pressure and velocity) highly repeatable and comparable, reducing the systematic error introduced by differences in pipeline configuration and making the conditions of the two measurements as consistent as possible.

[0030] The device also includes two liquid level sensors, which are used to monitor the liquid level in volumetric tank I2 and volumetric tank II3, respectively.

[0031] This invention also provides a method for testing cryogenic liquid flow meters. Using the aforementioned device for testing cryogenic liquid flow meters, and under the control of a control system, one-button operation is achieved through valve switching and hydraulic pump adjustment, resulting in a high degree of automation. The steps of this method are as follows: Step 1: Perform system precooling. Specifically: close valves II9, III10, IV11, and V12, and open valve I8; start hydraulic pumps A6 and B7 to allow the cryogenic liquid to flow through the cryogenic liquid flow meter to the main storage tank 1, thereby achieving pipeline precooling. Step 2: Close valve I8 and open valve II9 to allow the cryogenic liquid to flow through the cryogenic liquid flow meter and into the measuring tank I2. The cryogenic liquid flow meter records the instantaneous flow rate and accumulates the flow data in real time. When the measuring tank I2 reaches the set liquid level, close valve II9. Step 3: Open valve IV11 to return the liquid in measuring tank I2 to the main storage tank 1; after the liquid level change of measuring tank I2 (i.e., the flow rate into measuring tank I2) is completed, close valve IV11 and simultaneously open valve III10 to allow the cryogenic liquid to flow through the measured cryogenic liquid flow meter into measuring tank II3. The measured cryogenic liquid flow meter records the instantaneous flow rate in real time and accumulates the flow data; when measuring tank II3 reaches the set liquid level, close valve III10. Step 4: Open valve V12 to discharge the liquid in volumetric tank II3 back to main storage tank 1; after the liquid level change in volumetric tank II3 (i.e. the flow rate into volumetric tank II3) has been completed, close valve V12. Step 5: Repeat steps 2 to 4, alternating between volumetric tank I2 and volumetric tank II3, to achieve continuous measurement of cryogenic liquids; Step 6: Compare the cumulative flow data of the cryogenic liquid flow meter under test (the system will record the number of inflows) with the standard volume or mass of the measuring tank I2 or measuring tank II3; by comparing and calculating the error of the cryogenic liquid flow meter under test, its accuracy is evaluated.

[0032] By adjusting the hydraulic pump and conducting multiple tests, calibration curves were obtained under different flow rates and pressure conditions.

[0033] The device of this invention adopts a fully enclosed circulation to reduce the risk of cryogenic liquid leakage; it uses a standard volumetric liquid tank for comparison to avoid relying on expensive standard flow meters and ensure measurement accuracy; the liquid in the volumetric liquid tank can be recycled to the main storage tank 1 to reduce waste and lower operating costs; the hydraulic pump can adjust the flow rate and pressure to meet the calibration requirements of various cryogenic flow meters.

[0034] In summary, the above are merely preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A device for testing cryogenic liquid flow meters, characterized in that, Includes main storage tank, volumetric tank I, volumetric tank II, hydraulic pump, valves and control system; The main liquid storage tank is connected to three branch lines via a main pipeline. Two of these branch lines, located away from the main liquid storage tank, are respectively connected to measuring tank I and measuring tank II. The remaining branch line is connected to the main liquid storage tank. Each of the three branch lines is equipped with a valve. A cryogenic liquid flow meter is installed on the main pipeline, and hydraulic pumps are installed on both sides of the cryogenic liquid flow meter. Measuring tank I and measuring tank II are both connected to the main liquid storage tank via return lines, and both return lines are equipped with valves. The control system is used to control valve switching to achieve pipeline precooling, liquid inlet or outlet of liquid tank I and liquid tank II, and to regulate the hydraulic pump.

2. The apparatus for testing cryogenic liquid flow meters as described in claim 1, characterized in that, The main storage tank has a U-shaped cross section, and the main pipeline is located on the protruding parts on both sides of the U-shaped cross section, so that the outlet of the remaining branch pipeline and the inlet of the main pipeline are located on both sides of the main storage tank. The cryogenic liquid flow meter to be tested and the hydraulic pumps on both sides are located on the pipeline between the two protrusions; the main pipeline located in the main storage tank is above the liquid level.

3. The apparatus for testing cryogenic liquid flow meters as described in claim 1, characterized in that, The volumetric liquid tanks I and II are located on the same side of the main storage tank, and the valves on the three branch lines are at the same horizontal level.

4. The apparatus for testing cryogenic liquid flow meters as described in any one of claims 1-3, characterized in that, The device also includes two liquid level sensors, which are used to monitor the liquid level in volumetric tank I and volumetric tank II, respectively.

5. A method for testing cryogenic liquid flow meters, characterized in that, Using the apparatus for testing cryogenic liquid flow meters as described in claim 1, the method steps are as follows: Step 1: Under the control of the control system, close the valves on the branch lines connected to measuring tank I and measuring tank II, as well as the valves on the two return lines, and open the valves on the remaining branch lines; start the two hydraulic pumps to allow the cryogenic liquid to flow through the measured cryogenic liquid flow meter into the main storage tank, thereby achieving pipeline precooling; Step 2: Close the valves on the remaining branches and open the valve on the branch connected to the measuring tank I, so that the cryogenic liquid flows through the measured cryogenic liquid flow meter into the measuring tank I. The measured cryogenic liquid flow meter records the instantaneous flow rate in real time and accumulates the flow rate data. When the measuring tank I reaches the set liquid level, close the valve on the branch connected to the measuring tank I. Step 3: Open the valve on the return pipe connecting volumetric liquid tank I and the main storage tank to return the liquid in volumetric liquid tank I to the main storage tank; after the liquid level change in volumetric liquid tank I has been measured, close the valve on the return pipe connecting volumetric liquid tank I and the main storage tank, and simultaneously open the valve on the branch pipe connected to volumetric liquid tank II to allow the cryogenic liquid to flow through the cryogenic liquid flow meter being measured into volumetric liquid tank II. The cryogenic liquid flow meter being measured records the instantaneous flow rate in real time and accumulates the flow rate data; when volumetric liquid tank II reaches the set liquid level, close the valve on the branch pipe connected to volumetric liquid tank II. Step 4: Open the valve on the return pipeline connecting the volumetric liquid tank II and the main storage tank to drain the liquid in volumetric liquid tank II back to the main storage tank. After the liquid level change in measuring tank II has been discharged, close the valve on the return pipeline connecting measuring tank II and the main storage tank. Step 5: Repeat steps 2 to 4, alternating between volumetric tank I and volumetric tank II, to achieve continuous measurement of cryogenic liquids; Step six: Compare the cumulative flow data of the cryogenic liquid flow meter under test with the standard volume or mass of measuring tank I or measuring tank II; calculate the error of the cryogenic liquid flow meter under test by comparison and evaluate its accuracy.

6. The method for testing cryogenic liquid flow meters as described in claim 5, characterized in that, The hydraulic pump was adjusted and tested multiple times to obtain calibration curves under different flow rates and pressure conditions.

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