A low-temperature adiabatic container static evaporation rate test system and test method

Abstract

The application discloses a kind of low-temperature adiabatic container static evaporation rate test system and test method, the low-temperature adiabatic container static evaporation rate test system includes connecting pipeline, the connecting pipeline has import and export, the import is to connect the discharge port of low-temperature adiabatic container, the export is to directly communicate with atmospheric environment;Between the import and the export on the connecting pipeline, pressure measuring device, flow regulating device and mass flow meter are sequentially arranged, the pressure measuring device is to measure the gas pressure of the discharge port of low-temperature adiabatic container, the flow regulating device is to regulate the gas discharge flow of the connecting pipeline, and the mass flow meter is to measure the gas mass flow of the connecting pipeline.The technical scheme provided by the application shortens the low-temperature adiabatic container static evaporation rate measurement process, and the gas emission loss is small, so that the low-temperature adiabatic container can be quickly put into use after inspection, and the measurement efficiency is improved and the inspection cost is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of special equipment, and in particular to a static evaporation rate testing system and testing method for a low-temperature thermal insulation container. Background Art

[0002] Thermal insulation is a key performance characteristic of cryogenic insulated containers (including cryogenic insulated gas cylinders). It ensures the stable storage and transportation of refrigerated liquefied gases such as liquid nitrogen, liquid oxygen, liquid argon, and liquid helium. Poor or lost insulation can lead to the violent vaporization of the cryogenic liquefied gases, resulting in excessive release and loss. In severe cases, this can cause overpressure accidents in the container or cylinder. Because the insulation of cryogenic insulated containers (including cryogenic insulated gas cylinders) is not completely insulating, external heat can still enter as a very small heat flow, causing the cryogenic liquefied gases to slowly and continuously evaporate. If the container or cylinder remains closed, the boil-off gas accumulates, causing the pressure inside the container to rise. The better the container's insulation, the slower the pressure increase. If the container or cylinder remains vented (with a large vent aperture and no significant flow restriction), the boil-off gas will maintain a steady flow rate (regardless of the influence of ambient temperature and humidity). The better the container's insulation, the smaller the continuous overflow rate. The static evaporation rate is the ratio of the mass of gas continuously evaporating over a 24-hour period (daily evaporation) to the effective volume of the container or cylinder while maintaining thermal stability. The lower the static evaporation rate, the better the thermal insulation performance of the container or cylinder.

[0003] The national standard GB / T 18443.5, "Performance Test Methods for Vacuum Insulated Cryogenic Equipment - Part 5: Measurement of Static Evaporation Rate," specifies methods for testing and calculating the static evaporation rate of cryogenically insulated containers (including cryogenically insulated gas cylinders). Current static evaporation rate test equipment is designed and manufactured in accordance with the principles and methods of GB / T 18443.5-2010, "Performance Test Methods for Vacuum Insulated Cryogenic Equipment - Part 5: Measurement of Static Evaporation Rate": The equipment under test is filled with liquid nitrogen to the rated fill rate, allowed to stand for sufficient time to reach thermal equilibrium, and the mass of cryogenic gas lost through natural evaporation over 24 hours is measured as a percentage of the mass of cryogenic liquid in the container's effective volume. This is then converted to an evaporation rate under standard conditions (20°C, standard atmospheric pressure) in units of % / day.

[0004] Current testing technologies primarily focus on the rate of evaporation loss from cryogenic liquefied gas within a container due to natural heat leakage, including gravimetric and flow meter methods. The gravimetric method uses a scale to measure the weight change of a container over a period of time after it is filled with cryogenic liquid. This method is limited by the scale's range and accuracy, as well as the container's geometric dimensions. It is commonly used to test the static evaporation rate of cryogenic insulated gas cylinders with a volume of less than 200L. Vehicle-mounted liquefied natural gas cylinders and fixed vacuum-insulated cryogenic pressure vessels are already fixed to a bracket or base, making the gravimetric method impractical for static evaporation rate testing.

[0005] The flowmeter method uses a mass flowmeter to measure the gas flow rate of evaporating cryogenic liquids within a container. This method is not restricted by container geometry, volume, or weight, and has a wide range of applications. The standard test procedure for the flowmeter method, as outlined in GB / T 18443.5, begins by filling a cryogenically insulated container or cylinder. After the discharge valve is opened and the container or cylinder is allowed to stand for a sufficient period of time, a flowmeter is connected to the discharge port to measure the flow rate of naturally evaporating gas within the container or cylinder. Recording intervals are no less than hourly. The ratio of the 24-hour evaporation mass to the mass filled within the container or cylinder's effective volume is calculated to yield the test evaporation rate (% / day). To eliminate the effects of internal container or cylinder pressure and ambient temperature on cryogenic liquefied gas during testing, GB / T 18443.5 also provides a correction formula to yield the static evaporation rate. While the flowmeter method offers advantages of wide applicability and high accuracy, it also presents challenges such as a lengthy measurement process, significant discharge losses, and the inability to quickly return the container to service after testing. A complete test requires at least four days: a 48-hour stand-by period before testing, a 24-hour test, and a 24-hour retest. For a 400L container, a single test must release at least 50kg of cryogenically cooled liquefied gas, resulting in a waste of resources. The container (including the gas cylinder) undergoes a period of slow pressurization before it is ready for use (reaching the operating pressure). Summary of the Invention

[0006] The main purpose of the present invention is to provide a static evaporation rate test system and test method for a low-temperature insulated container, aiming to shorten the static evaporation rate measurement process of the low-temperature insulated container, reduce gas emission losses, and enable the low-temperature insulated container to be quickly put into use after inspection, thereby improving measurement efficiency and reducing inspection costs.

[0007] To achieve the above-mentioned objectives, the present invention proposes a static evaporation rate testing system for a low-temperature insulated container, wherein the static evaporation rate testing system for a low-temperature insulated container includes a connecting pipeline, wherein the connecting pipeline has an inlet and an outlet, wherein the inlet is used to connect to the discharge port of the low-temperature insulated container, and the outlet is used to directly connect to the atmospheric environment; on the connecting pipeline, a pressure measuring device, a flow regulating device and a mass flow meter are sequentially arranged between the inlet and the outlet, wherein the pressure measuring device is used to measure the gas pressure at the discharge port of the low-temperature insulated container, the flow regulating device is used to regulate the gas discharge flow of the connecting pipeline, and the mass flow meter is used to measure the gas mass flow of the connecting pipeline.

[0008] Optionally, the low-temperature insulation container static evaporation rate testing system further includes:

[0009] Temperature measuring device, used to detect the gas temperature at the discharge port of the low-temperature insulation container.

[0010] Optionally, the pressure measuring device includes a precision pressure gauge or a precision pressure transmitter.

[0011] Optionally, the flow regulating device includes a metering valve or a fine needle valve.

[0012] Optionally, the flow regulating device includes a throttling hole and a solenoid valve, the connecting pipeline has a flow regulating section located between the pressure measuring device and the mass flow meter, and the flow regulating section includes a plurality of flow regulating branches arranged in parallel with each other; in the direction from the pressure measuring device to the mass flow meter, each of the flow regulating branches is sequentially provided with a solenoid valve and a throttling hole, the apertures of the plurality of throttling holes are different, and each throttling hole corresponds to a flow range, so as to realize full-range control of the gas emission flow of the connecting pipeline.

[0013] Optionally, the apertures of the plurality of throttling holes range from 0.05 to 1.00 mm.

[0014] Optionally, the low-temperature insulation container static evaporation rate test system also includes a manual stop valve arranged on the connecting pipeline, and the manual stop valve is used to be arranged between the discharge port of the low-temperature insulation container and the pressure measuring device to control the connection or closing of the connecting pipeline.

[0015] Optionally, the low-temperature insulation container static evaporation rate testing system further includes a controller, which is electrically connected to the pressure measuring device, the flow regulating device and the mass flow meter respectively.

[0016] The present invention also provides a method for testing the static evaporation rate of a low-temperature thermally insulated container based on the above-mentioned static evaporation rate testing system for a low-temperature thermally insulated container. The method comprises:

[0017] Control the connecting pipeline to the initial flow rate Q under working pressure x1 Exhaust gas, obtain the measured exhaust flow rate Q1 of the connecting pipeline and the pressure change rate P(t)1 in the low-temperature insulation container;

[0018] Control the connecting pipeline at multiple flow rates Q under working pressure x2 ~Q xn Exhaust gas, obtain multiple measured exhaust flow rates Q2~Q n and multiple pressure change rates P(t)2~P(t) in the low-temperature insulation container n ;

[0019] According to the measured discharge flow rate Q1, multiple measured discharge flow rates Q2~Q n , pressure change rate P(t)1 and multiple pressure change rates P(t)2~P(t) n, obtain the k value and b value in the linear relationship Q=k*P(t)+b of the actual discharge flow rate Q and the pressure change rate P(t).

[0020] Optionally, the measured discharge flow rate Q1, multiple measured discharge flow rates Q2 to Q n , pressure change rate P(t)1 and multiple pressure change rates P(t)2~P(t) n The steps of obtaining the k value and the b value in the linear relationship Q=k*P(t)+b of the actual discharge flow Q and the pressure change rate P(t) specifically include the following steps: n , pressure change rate P(t)1 and multiple pressure change rates P(t)2~P(t) n , the k value and b value in the linear relationship Q=k*P(t)+b of the actual discharge flow Q and the pressure change rate P(t) are obtained by linear fitting or iteration method.

[0021] In the technical solution of the present invention, the connecting pipeline is controlled by a flow regulating device to discharge gas at different discharge flow rates, and the mass flowmeter is used to measure and obtain the actual discharge flow rate of the connecting pipeline under different flow control, and the corresponding gas pressure and pressure change rate are measured by the pressure measuring device. At the same time, the flow regulating device is used to adjust the gas flow rate of the connecting pipeline and the actual evaporation flow rate to a smaller value, so that the temperature (temperature field) in the low-temperature insulation container is approximately stable, so that the actual discharge flow rate Q and the pressure change rate P(t) conform to an approximate linear relationship. After obtaining the linear relationship, the pressure change rate P(t) is taken as zero, and the corresponding actual discharge flow rate Q is calculated as the deep-cold liquid evaporation flow value Qx, and then the static evaporation rate of the low-temperature insulation container is calculated based on the evaporation flow value Qx. The static evaporation rate test system for a low-temperature insulated container has the function of directly detecting the static evaporation rate under the working pressure of the low-temperature insulated container. There is no need to discharge the low-temperature insulated container from the working pressure to zero pressure (gauge pressure) in advance. The flow rate is kept stable during the measurement process. Unlike obtaining the continuous evaporation flow of the low-temperature insulated container under a stable working pressure, there is no need for a pressure stabilization device. This system measures the pressure change rate of the inner cavity of the low-temperature insulated container under multiple stable discharge flow rates, and obtains the static evaporation rate by calculation. The static evaporation rate is the static evaporation rate of the low-temperature insulated container at a certain point in time, not the average static evaporation rate of 24 hours (1 day). However, since the static process before the test does not require operation, the actual detection time is very short, thereby shortening the static evaporation rate measurement process of the low-temperature insulated container, reducing gas emission losses, and the low-temperature insulated container can be quickly put into use after inspection, thereby improving measurement efficiency and reducing inspection costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying any creative work.

[0023] Figure 1 A schematic structural diagram of an embodiment of a low-temperature insulation container static evaporation rate testing system provided by the present invention;

[0024] Figure 2 This is a schematic flow chart of an embodiment of a method for testing the static evaporation rate of a low-temperature insulated container provided by the present invention.

[0025] Description of Figure Numbers:

[0026] Label name Label name 100 Cryogenic Insulated Container Static Evaporation Rate Test System 3 Flow regulating device 200 Low temperature insulated container 31 throttle hole 1 Connecting pipes 32 solenoid valve 11 import 4 Mass flow meter 12 exit 5 Manual stop valve 2 Pressure measuring device 6 Controller

[0027] The purpose, features and advantages of the present invention will be further described with reference to the accompanying drawings and in conjunction with the embodiments. DETAILED DESCRIPTION

[0028] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0029] It should be noted that if the embodiments of the present invention involve directional indications (such as up, down, left, right, front, back, etc.), the directional indications are only used to explain the relative position relationship, movement status, etc. between the various components under a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indications will also change accordingly.

[0030] In addition, if there are descriptions involving "first", "second", etc. in the embodiments of the present invention, the descriptions of "first", "second", etc. are only for descriptive purposes and cannot be understood as indicating or suggesting their relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of such features. In addition, the meaning of "and / or" appearing throughout the text includes three parallel schemes. Taking "A and / or B" as an example, it includes scheme A, or scheme B, or a scheme in which A and B are satisfied at the same time. In addition, the technical solutions between the various embodiments can be combined with each other, but it must be based on the ability of ordinary technicians in this field to implement. When the combination of technical solutions is mutually contradictory or cannot be implemented, it should be deemed that such a combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0031] The static evaporation rate test methods for cryogenic insulated containers (including cryogenic insulated gas cylinders) include the gravimetric method and the flowmeter method, both of which focus on the rate of evaporation loss of cryogenic liquefied gas in the container due to natural heat leakage. Among them, the gravimetric method uses a scale to measure the weight change of the container within a cycle after it is filled with cryogenic liquid. The gravimetric method is limited by the scale's range and accuracy, as well as the container's geometric dimensions. It is commonly used for static evaporation rate testing of cryogenic insulated gas cylinders with a volume of less than 200L. Vehicle-use liquefied natural gas cylinders and fixed vacuum insulated cryogenic pressure vessels are already fixed to a bracket or base, and the above gravimetric method cannot be used to achieve static evaporation rate testing.

[0032] The flowmeter method uses a mass flowmeter to measure the gas flow rate of evaporating cryogenic liquids within a container. This method is not restricted by container geometry, volume, or weight, and has a wide range of applications. The standard test procedure for the flowmeter method, as outlined in GB / T 18443.5, begins by filling a cryogenically insulated container or cylinder. After the discharge valve is opened and the container or cylinder is allowed to stand for a sufficient period of time, a flowmeter is connected to the discharge port to measure the flow rate of naturally evaporating gas within the container or cylinder. Recording intervals are no less than hourly. The ratio of the 24-hour evaporation mass to the mass filled within the container or cylinder's effective volume is calculated to yield the test evaporation rate (% / day). To eliminate the effects of internal container or cylinder pressure and ambient temperature on cryogenic liquefied gas during testing, GB / T 18443.5 also provides a correction formula to yield the static evaporation rate. While the flowmeter method offers advantages of wide applicability and high accuracy, it also presents challenges such as a lengthy measurement process, significant discharge losses, and the inability to quickly return the container to service after testing. A complete test requires at least four days: a 48-hour stand-by period before testing, a 24-hour test, and a 24-hour retest. For a 400L container, a single test must release at least 50kg of cryogenically cooled liquefied gas, resulting in a waste of resources. The container (including the gas cylinder) undergoes a period of slow pressurization before it is ready for use (reaching the operating pressure).

[0033] In view of this, the present invention provides a static evaporation rate testing system and method for a low-temperature insulated container, aiming to shorten the static evaporation rate measurement process of the low-temperature insulated container, reduce gas emission losses, and enable the low-temperature insulated container to be quickly put into use after inspection, thereby improving measurement efficiency and reducing inspection costs. Figure 1 This is an embodiment of the static evaporation rate testing system for a low-temperature insulated container provided by the present invention. Figure 2 This is an embodiment of the static evaporation rate testing method for a low-temperature insulated container provided by the present invention.

[0034] In the embodiment of the present invention, please refer to Figure 1 The present invention proposes a static evaporation rate testing system 100 for a low-temperature insulated container, which includes a connecting pipeline 1 having an inlet 11 and an outlet 12. The inlet 11 is used to connect to the discharge port of the low-temperature insulated container 200, and the outlet 12 is used to directly connect to the atmospheric environment. On the connecting pipeline 1, a pressure measuring device 2, a flow regulating device 3 and a mass flowmeter 4 are sequentially arranged between the inlet 11 and the outlet 12. The pressure measuring device 2 is used to measure the gas pressure at the discharge port of the low-temperature insulated container 200, the flow regulating device 3 is used to regulate the gas discharge flow of the connecting pipeline 1, and the mass flowmeter 4 is used to measure the gas mass flow of the connecting pipeline 1.

[0035] In the technical solution of the present invention, the flow regulating device 3 is used to control the connecting pipeline 1 to discharge gas at different discharge flow rates, and the mass flowmeter 4 is used to measure and obtain the actual discharge flow rate of the connecting pipeline 1 at different discharge flow rates, and the corresponding gas pressure is measured by the pressure measuring device 2 to obtain the corresponding pressure change rate. At the same time, the flow regulating device 3 is used to adjust the difference between the gas flow rate of the connecting pipeline 1 and the estimated gas evaporation flow rate or the theoretical or reasonable evaporation gas flow rate to a smaller value, so that the temperature (temperature field) in the low-temperature insulation container 200 fluctuates in a very small range, so that the actual discharge flow rate Q and the pressure change rate P(t) conform to an approximate linear relationship. After obtaining the linear relationship, the pressure change rate P(t) is taken as zero, and the corresponding actual discharge flow rate Q is calculated as the deep-cold liquid evaporation flow value Qx, and then the static evaporation rate of the low-temperature insulation container 200 is calculated based on the evaporation flow value Qx. The low-temperature insulated container static evaporation rate test system 100 has the function of directly detecting the static evaporation rate under the working pressure of the low-temperature insulated container 200. There is no need to discharge the low-temperature insulated container 200 from the working pressure to zero pressure (gauge pressure) in advance. The flow rate is kept stable during the measurement process. Different from obtaining the continuous evaporation flow of the low-temperature insulated container 200 under the condition of stable working pressure, there is no need for a pressure stabilization device. This system measures the pressure change rate of the inner cavity of the low-temperature insulated container 200 under multiple stable discharge flow rates, and obtains the static evaporation rate by calculation. The static evaporation rate is the static evaporation rate of the low-temperature insulated container 200 at a certain point in time, not the average static evaporation rate of 24 hours (1 day). However, since the static process before the test does not require operation, the actual detection time is very short, thereby shortening the static evaporation rate measurement process of the low-temperature insulated container 200, and the gas emission loss is small. After the inspection, the low-temperature insulated container 200 can be put into use quickly, thereby improving measurement efficiency and reducing inspection costs.

[0036] It should be noted that according to the ideal gas formula pV=nRT, p is the pressure (Pa), V is the gas volume (m 3), T is the temperature (K), n is the amount of gas (mol), and R is the molar gas constant (J / (mol.K)). The volume of the sealed cryogenically insulated container 200 (including the cryogenically insulated gas cylinder) remains constant, the temperature or temperature field is essentially stable, and the continuous evaporation of liquid into gas causes a continuous increase in pressure. Therefore, Δp is approximately proportional to the volume of evaporated gas or the flow rate of the evaporated gas. Therefore, by making the gas phase space within the cryogenically insulated container 200 (including the cryogenically insulated gas cylinder) resemble an ideal gas, the pressure change can be approximately proportional to the evaporation flow rate. The flow regulating device 3 is used to adjust the gas flow of the connecting pipeline 1 to be controlled at the flow corresponding to the estimated static evaporation rate and to maintain stability (fluctuation does not exceed 1%), and the pressure change in the low-temperature insulation container 200 during the current flow discharge is measured, and the gas flow of the connecting pipeline 1 is adjusted. The adjustment direction is opposite to the direction of pressure change (i.e., when the pressure increases, the flow decreases, and when the pressure decreases, the flow increases). The flow adjustment amount is controlled within the range of 20% to 100%, which can make the temperature (temperature field) in the low-temperature insulation container 200 approximately stable, so that the actual discharge flow Q and the pressure change rate P(t) conform to an approximate linear relationship.

[0037] In this embodiment, the low-temperature insulated container static evaporation rate test system 100 also includes a temperature measuring device (not shown in the figure) for detecting the gas temperature at the exhaust port of the low-temperature insulated container 200, thereby performing real-time detection of the gas temperature to ensure and verify that the temperature (temperature field) fluctuation range of the exhaust port of the low-temperature insulated container 200 meets the requirements. Specifically, the temperature measuring device includes an infrared temperature measuring device, which can conveniently measure the temperature of the exhaust port of the low-temperature insulated container 200.

[0038] Furthermore, the pressure measurement device 2 includes a precision pressure gauge or precision pressure transmitter for accurately measuring the gas pressure at the discharge port of the cryogenic insulated container 200. Specifically, the precision pressure gauge or precision pressure transmitter has an accuracy level of no less than 0.05 to meet pressure measurement and control requirements. Similarly, to meet measurement accuracy requirements, the mass flowmeter 4 has an accuracy level of no less than 0.5.

[0039] In this embodiment, the flow regulating device 3 includes a metering valve or a fine needle valve, which is convenient for accurately regulating the gas exhaust flow of the connecting pipeline 1.

[0040] Furthermore, the flow regulating device 3 includes a throttling hole 31 and a solenoid valve 32, and the connecting pipeline 1 has a flow regulating section located between the pressure measuring device 2 and the mass flow meter 4, and the flow regulating section includes a plurality of flow regulating branches arranged in parallel with each other; in the direction from the pressure measuring device 2 to the mass flow meter 4, each of the flow regulating branches is sequentially provided with a solenoid valve 32 and a throttling hole 31, and the apertures of the plurality of throttling holes 31 are different, and each throttling hole 31 corresponds to a flow range to achieve full-scale control of the gas emission flow of the connecting pipeline 1, and the closing or flow of the corresponding throttling hole 31 is controlled by the solenoid valve 32, and the gas emission flow of the connecting pipeline 1 is accurately and reliably regulated by the combination of throttling holes 31 with different apertures and different numbers of throttling holes 31.

[0041] In this embodiment, the apertures of the plurality of throttle holes 31 range from 0.05 to 1.00 mm and can be combined to precisely adjust a relatively small gas discharge flow rate. Specifically, the throttle holes 31 include at least eight apertures, with apertures of 0.05 mm, 0.10 mm, 0.15 mm, 0.20 mm, 0.25 mm, 0.30 mm, 0.35 mm, 0.40 mm, and 0.45 mm. At an operating pressure of 1.0 MPa, the standard flow rate can be controlled within a range of 0.5 L / min to 10 L / min.

[0042] Furthermore, the low-temperature insulated container static evaporation rate test system 100 also includes a manual stop valve 5 provided on the connecting pipeline 1. The manual stop valve 5 is used to be provided between the discharge port of the low-temperature insulated container 200 and the pressure measuring device 2 to control the connection or closing of the connecting pipeline 1, thereby facilitating overall control of the connecting pipeline 1.

[0043] In this embodiment, the low-temperature insulated container static evaporation rate testing system 100 further includes a controller 6, which is electrically connected to the pressure measuring device 2, the flow regulating device 3, and the mass flowmeter 4, respectively. Specifically, when the flow regulating device 3 includes a throttle orifice 31 and a solenoid valve 32, the controller 6 is electrically connected to the solenoid valve 32. The controller 6 automatically controls the gas discharge flow rate of the connecting pipeline 1 and has data acquisition, storage, calculation, and feedback functions, thereby improving testing efficiency. Specifically, the controller 6 includes a computer or mobile phone, a program controller, a signal collector, etc.

[0044] The present invention also provides a method for testing the static evaporation rate of a low-temperature thermally insulated container based on the above-mentioned static evaporation rate testing system 100. The method comprises:

[0045] Step S100: Control the connecting pipeline 1 to flow at an initial flow rate Q under working pressure. x1 Exhaust gas, obtain the measured exhaust flow rate Q1 of the connecting pipeline 1 and the pressure change rate P(t)1 in the low-temperature insulation container 200;

[0046] Step S200: Control the connecting pipeline 1 to flow at multiple flow rates Q under working pressure. x2 ~Q xn Exhaust gas, obtain multiple measured exhaust flow rates Q2~Q n and multiple pressure change rates P(t)2 to P(t) in the low-temperature insulation container 200 n ;

[0047] Step S300: Based on the measured discharge flow Q1, multiple measured discharge flow rates Q2-Q n , pressure change rate P(t)1 and multiple pressure change rates P(t)2~P(t) n , obtain the k value and b value in the linear relationship Q=k*P(t)+b of the actual discharge flow rate Q and the pressure change rate P(t).

[0048] Furthermore, the measured discharge flow rate Q1, multiple measured discharge flow rates Q2 to Q n , pressure change rate P(t)1 and multiple pressure change rates P(t)2~P(t) n The step S300 of obtaining the k value and the b value in the linear relationship Q=k*P(t)+b of the actual discharge flow Q and the pressure change rate P(t) specifically includes: according to the measured discharge flow Q1, multiple measured discharge flow rates Q2~Q n , pressure change rate P(t)1 and multiple pressure change rates P(t)2~P(t) n , the k value and b value in the linear relationship Q=k*P(t)+b of the actual discharge flow Q and the pressure change rate P(t) are obtained by linear fitting or iteration method.

[0049] Specifically, the low-temperature insulation container 200 is allowed to stand for 12 to 24 hours before testing, depending on the volume of the container. The manual stop valve 5 is opened, and the exhaust gas flow rate is controlled by the flow regulating device 3 to be the flow rate corresponding to the estimated static evaporation rate, that is, the initial flow rate Q x1 The gas flow rate is adjusted to another value Q1, which is the actual discharge flow rate. The corresponding gas pressure is measured by the pressure measuring device 2, thereby obtaining the corresponding pressure change in the container cavity, that is, the pressure change rate P(t)1, which lasts for about 10 minutes. i , Q i The value is Q i-1+ΔQ, ΔQ ranges from (-50% to 50%) × Q i-1 Set within the range; measure the pressure change rate P(t) inside the container or cylinder again i , repeat several times in sequence to obtain more than 3 discharge flow rates Q i (i.e. Q1~Q n ) and the corresponding pressure change rate P(t) i (i.e. P(t)1~P(t) n ). Linear fitting is used to obtain the linear relationship between the discharge flow rate Q and the pressure change rate P(t). The discharge flow rate Q (P(x) = 0) corresponding to the pressure change rate of zero (P(t) = 0) is calculated as the evaporation flow rate under pressure. The test evaporation rate a0 and the static evaporation rate a are calculated based on the evaporation flow rate, the average pressure in the container cavity, the gas density at the average temperature of the discharge gas, and other auxiliary parameters. 20 Since the static process does not require any operation, it can be done during off-peak hours or at night, so the actual detection time is about 30 minutes.

[0050] You can also estimate the evaporation flow rate under the static evaporation rate, that is, the initial flow rate Q x1 , measure the test evaporation flow rate, and then iterate with the measured evaporation flow rate, repeatedly measure the measured evaporation flow rate until the estimated value is close to the measured value (within a certain allowable deviation range, such as 5% according to specific requirements). The measurement plan is as follows: connect the measuring equipment, and according to the parameters such as the cylinder volume, working pressure, and estimated test evaporation rate, initially set the evaporation flow rate Qx1 under a working pressure, open the flow regulating device 3 to initially set the flow rate to continuously and stably release gas, and record the measured flow rate Q for 10 to 30 minutes through the mass flow meter 4 and the pressure measuring device 2. i and the measured pressure change P(t) i ; Manually or automatically adjust the flow rate, adjust Q based on the initial flow rate xi ±△Q, release gas continuously and stably, record Q in the next stage i and the measured pressure P(t) i According to the approximate ideal gas equation, evaporation flow Q = kP (t) + b is calculated as b for the test evaporation flow Q x1 ; Set the test evaporation flow rate to Q x1 Replace Q x , manual or automatic adjustment of Q x1 ±△Q, the controller 6 calculates the stable flow value Q of the low-temperature insulation container 200 or the gas cylinder under the working pressure x2 . Adjust multiple times in sequence, Q xn With Q x(n-1) Less than the standard allowable deviation range, then Q xn Recorded as the evaporation flow rate of low-temperature insulated cryogenic containers or gas cylinders under actual working pressure.

[0051] It should be noted that the controller 6 in the low-temperature insulated container static evaporation rate test system 100 includes a memory and a processor and a control program stored in the memory and executable on the processor, and the control program is configured to implement the steps of the above-mentioned low-temperature insulated container static evaporation rate test method.

[0052] The static evaporation rate test system 100 for low-temperature insulated containers and the test method provided by the present invention are used to compare and verify vehicle-use LNG cylinders. A vehicle-use LNG cylinder manufactured by Zhangjiagang Furui Special Equipment Co., Ltd., model: CDPW600-450-1.59, volume: 450L, filling medium: LNG, nominal working pressure: 1.59MPa, actual working pressure 0.6MPa~1.59MPa is selected.

[0053] Example 1: According to the conventional static evaporation rate detection method

[0054] (1) According to the conventional static evaporation rate detection method, after filling with liquid and releasing the pressure to zero, it was left to stand for 48 hours and connected to the mass flow meter for measurement for 24 hours. The test results were: average evaporation flow rate Qx = 2.16L / min, atmospheric pressure 101.39KPa, ambient temperature 32℃, that is, T1 = 305.15K.

[0055] (2) Check the physical property table. The saturated liquid temperature of natural gas at atmospheric pressure of 101.39 kPa is T2 = 111.97 K, and the latent heat of vaporization is h = 497.0986 kJ / kg. The saturated liquid temperature at standard atmospheric pressure is TS = 111.63 K, and the latent heat of vaporization is hfg = 497.1045 kJ / kg. The liquid density is ρ1 = 433.53 kg / m3, and the gas density is ρ2 = 0.716 kg / m3. The flowmeter calibration coefficient is 1.

[0056] (3) According to q m =ρ2×Q X ×1440 and According to the formula, we can calculate that α0 = 1.14% / d.

[0057] In order to facilitate the comparison of the static evaporation rate test results under working pressure and the static evaporation rate test results under ambient atmospheric pressure, the test ambient temperature remains unchanged. After ignoring the influence of ambient temperature, the a20 calculation formula of GB / T18443.5 is adjusted to

[0058] Calculate α from this 20 =1.14% / d.

[0059] 2. Test using the low-temperature insulation container static evaporation rate test system 100 provided by the present invention

[0060] (1) using the device of the application, after filling, closing the discharge valve, standing for 24 hours, connecting the device of the application, the internal pressure is 1.0 MPa, the ambient temperature is 32℃, that is, T1=305.15K, the measured data table is as follows: discharge flow 1.8L / min (standard state), P(t)=0.0510kPa / min, discharge flow 2.2L / min (standard state), P(t)=0.0281kPa / min, discharge flow 2.5L / min (standard state), P(t)=0.0110kPa / min.

[0061] The relationship between the discharge flow and the pressure change is calculated as Q=kP(t)+b, and thus the measured evaporation flow Q x =2.69L / min at 1.0MPa;

[0062] (2) According to the property table, the absolute pressure of the gas is 1.0MPa, the corresponding liquid saturation temperature T2=149.11K, the latent heat of vaporization h=410.4017kJ / kg; the saturation liquid temperature at standard atmospheric pressure TS=111.63K, the latent heat of vaporization hfg=497.1045kJ / kg, the liquid density ρ1=433.53kg / m3, the gas density ρ2=0.716kg / m3, and the flowmeter calibration coefficient is taken as 1.

[0063] (3) According to q m =ρ2×Q X ×1440 and formula, it can be calculated that α0=1.42% / d; according to , it can be calculated that α 20 =1.17% / d.

[0064] 3. Comparison of results

[0065] The error of the test results of the low-temperature adiabatic container static evaporation rate test system 100 and the conventional test results is 3.0%, and the error of the static evaporation rate obtained by the standard test method can be controlled within 5%. According to the provisions of GB / T18443.5-2010 "Vacuum adiabatic cryogenic equipment performance test method Part 5 Static evaporation rate measurement" 7.1.6, the allowable deviation of two measurement results is 5%. The deviation of two measurements by different detection methods is lower than the running deviation of two parallel tests by the same method, which fully verifies the accuracy of the measurement results obtained by the method and system of the application.

[0066] The above is only a preferred embodiment of the application, and does not limit the patent scope of the application, and any equivalent structural transformation made on the basis of the concept of the application, or direct / indirect application in other related technical fields is included in the patent protection scope of the application.

Claims

1. A method for testing the static evaporation rate of a low-temperature insulated container in a low-temperature insulated container static evaporation rate testing system, characterized in that: The static evaporation rate test system for a low-temperature insulated container includes a connecting pipeline having an inlet and an outlet, the inlet being connected to the discharge port of the low-temperature insulated container, and the outlet being directly connected to the atmospheric environment; a pressure measuring device, a flow regulating device, and a mass flow meter are sequentially provided on the connecting pipeline between the inlet and the outlet, the pressure measuring device being used to measure the gas pressure at the discharge port of the low-temperature insulated container, the flow regulating device being used to regulate the gas discharge flow rate of the connecting pipeline, and the mass flow meter being used to measure the gas mass flow rate of the connecting pipeline; The static evaporation rate test method of the low-temperature insulation container includes: Control the connecting pipeline to the initial flow rate Q under working pressure x1 Exhaust gas, obtain the measured exhaust flow rate Q1 of the connecting pipeline and the pressure change rate P(t)1 in the low-temperature insulation container; Control the connecting pipeline at multiple flow rates Q under working pressure x2 ~Q xn Exhaust gas, obtain multiple measured exhaust flow rates Q2~Q n and multiple pressure change rates P(t)2~P(t) in the low-temperature insulation container n ; According to the measured discharge flow rate Q1, multiple measured discharge flow rates Q2~Q n , pressure change rate P(t)1 and multiple pressure change rates P(t)2~P(t) n , obtain the k value and b value in the linear relationship Q=k*P(t)+b of the actual discharge flow rate Q and the pressure change rate P(t).

2. The method for testing the static evaporation rate of a low-temperature insulated container of the static evaporation rate testing system of low-temperature insulated container according to claim 1, characterized in that: The low-temperature insulation container static evaporation rate testing system also includes: Temperature measuring device, used to detect the gas temperature at the discharge port of the low-temperature insulation container.

3. The method for testing the static evaporation rate of a low-temperature thermally insulated container of the static evaporation rate testing system of low-temperature thermally insulated container according to claim 1, characterized in that: The pressure measuring device includes a precision pressure gauge or a precision pressure transmitter.

4. The method for testing the static evaporation rate of a low-temperature thermally insulated container of the static evaporation rate testing system of claim 1, characterized in that: The flow regulating device includes a metering valve or a fine needle valve.

5. The method for testing the static evaporation rate of a low-temperature thermally insulated container of the static evaporation rate testing system of low-temperature thermally insulated container according to claim 1, characterized in that: The flow regulating device includes a throttling hole and a solenoid valve. The connecting pipeline has a flow regulating section located between the pressure measuring device and the mass flow meter. The flow regulating section includes multiple flow regulating branches arranged in parallel with each other. In the direction from the pressure measuring device to the mass flow meter, each of the flow regulating branches is sequentially provided with a solenoid valve and a throttling hole. The apertures of the multiple throttling holes are different, and each throttling hole corresponds to a flow range to achieve full-range control of the gas emission flow of the connecting pipeline.

6. The method for testing the static evaporation rate of a low-temperature thermally insulated container of the static evaporation rate testing system of low-temperature thermally insulated container according to claim 5, characterized in that: The apertures of the plurality of throttling holes range from 0.05 to 1.00 mm.

7. The method for testing the static evaporation rate of a low-temperature thermally insulated container of the static evaporation rate testing system of low-temperature thermally insulated container according to claim 1, characterized in that: The low-temperature insulated container static evaporation rate test system also includes a manual stop valve arranged on the connecting pipeline. The manual stop valve is used to be arranged between the discharge port of the low-temperature insulated container and the pressure measuring device to control the connection or closing of the connecting pipeline.

8. The method for testing the static evaporation rate of a low-temperature thermally insulated container of the static evaporation rate testing system for a low-temperature thermally insulated container according to any one of claims 1 to 7, characterized in that: The low-temperature insulation container static evaporation rate testing system further includes a controller, which is electrically connected to the pressure measuring device, the flow regulating device, and the mass flowmeter respectively.

9. The method for testing the static evaporation rate of a low-temperature thermally insulated container of the static evaporation rate testing system of low-temperature thermally insulated container according to claim 1, characterized in that: The step of obtaining the k value and b value in the linear relationship Q=k*P(t)+b of the actual discharge flow Q and the pressure change rate P(t) based on the measured discharge flow Q1, multiple measured discharge flow rates Q2~Qn, the pressure change rate P(t)1 and multiple pressure change rates P(t)2~P(t)n specifically includes obtaining the k value and b value in the linear relationship Q=k*P(t)+b of the actual discharge flow Q and the pressure change rate P(t) through linear fitting or iterative method based on the measured discharge flow Q1, multiple measured discharge flow rates Q2~Qn, the pressure change rate P(t)1 and multiple pressure change rates P(t)2~P(t)n.

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