Hydrogen liquefaction device cold box liquid level evaluation method, device and storage medium

Abstract

This invention relates to the field of energy technology and discloses a method, apparatus, and storage medium for assessing the liquid level of a cold box in a hydrogen liquefaction unit. This invention combines the instantaneous rate curve of liquid hydrogen production with multiple preset experimental sampling logics, utilizing a preset cold box testing device to differentially obtain multiple sets of physical property parameters corresponding to the cold box during the hydrogen liquefaction process. Furthermore, by using a preset cold release convection heat transfer coefficient relationship, the target cold release convection heat transfer coefficient is determined, providing support for determining the defrosting frequency. This avoids frequent fixed-cycle defrosting operations and can more accurately guide the defrosting operation of the dynamic process combining the evaporation of the working fluid in the hydrogen liquefaction cold box and the injection of the working fluid into the cold box, thereby improving the technical and economic efficiency of liquid hydrogen production to a certain extent. Furthermore, by combining the determined defrosting frequency with the liquid level assessment results of the cold box in the hydrogen liquefaction unit, the operational efficiency of the dynamic process combining the evaporation of the working fluid in the cold box and the injection of the refrigerant into the cold box is improved.

Description

Technical Field

[0001] This invention relates to the field of energy technology, and specifically to a method, apparatus, and storage medium for assessing the liquid level in a cold box used in a hydrogen liquefaction device. Background Technology

[0002] With the development of the hydrogen energy market, the demand for liquid hydrogen in the civilian market is gradually increasing. Compared with high-pressure gaseous hydrogen, cryogenic liquid hydrogen has a higher hydrogen carrying capacity, lower long-distance transportation costs, and smaller equipment and system size during transfer and storage. It is the optimal choice for large-scale, long-distance commercial applications of hydrogen-electric coupling. Hydrogen liquefaction technology is a key link in the application of hydrogen energy as a potential medium for large-scale, dense energy storage in the power sector. Reducing energy consumption is an urgent need for the construction and demonstration application of hydrogen liquefaction stations. In the pre-cooling and isentropic expansion stages of liquid hydrogen production, the refrigerant used in liquid hydrogen production will spontaneously evaporate during the process of entering the corresponding cold box and then being stored. This will inevitably cause frost formation, including frost formation in general cooling (temperature > 120K) and frost formation in deep cooling (temperature 120K to 0.3K). The frost is equivalent to external heating resistance, which will adversely affect the energy consumption of liquid hydrogen production.

[0003] Current defrosting or frost-suppressing technologies for hydrogen liquefaction processes in cryogenic temperatures are mostly geared towards liquid hydrogen vaporization and subsequent pressurization. They lack defrosting and frost-suppressing technologies for the dynamic process combining the evaporation of the working fluid in the cold box and the injection of refrigerant into the cold box in cryogenic temperatures. Furthermore, existing defrosting or frost-suppressing technologies for hydrogen liquefaction processes in cryogenic temperatures are mostly based on the heat and mass transfer principles of the frosting process in ordinary cold temperatures. They derive the thermal conductivity of frost from the physical properties of frost in ordinary cold temperatures, thus providing a reference for customizing physical defrosting structures for the environment in which the hydrogen liquefaction system operates. However, hydrogen liquefaction systems are space-constrained, thus having strong limitations. Alternatively, they involve frequent defrosting operations at fixed intervals, but such operations lack accuracy and transfer the cost of energy savings in the liquid hydrogen production process to the cost of blindly using defrosting and frost-suppressing media, without substantially improving the technical and economic benefits. Summary of the Invention

[0004] In view of this, the present invention provides a liquid level assessment method, apparatus and storage medium for a cold box in a hydrogen liquefaction unit, to solve the problem that existing delayed frosting or defrosting technologies for hydrogen liquefaction processes in cryogenic temperature ranges are limited by the compact space of the hydrogen liquefaction system, and the accuracy of frequent fixed-cycle defrosting operations is insufficient. Furthermore, the cost of energy savings in the liquid hydrogen production process is transferred to the cost of blindly using anti-frost and defrosting media, thus resulting in no substantial improvement in technical and economic benefits.

[0005] In a first aspect, the present invention provides a method for assessing the liquid level in a cold box for a hydrogen liquefaction unit, the method comprising:

[0006] The instantaneous rate curve of liquid hydrogen production in the hydrogen liquefaction unit is obtained within the first time period, which reflects the time period adjacent to but shorter than the target time. Based on the instantaneous rate curve and multiple preset experimental sampling logics, multiple sets of physical property parameters corresponding to the cold box used in the hydrogen liquefaction process are obtained using a preset cold box test device. Based on the multiple sets of physical property parameters, the target cold release convection heat transfer coefficient is obtained after processing with a preset cold release convection heat transfer coefficient relationship. Based on the target cold release convection heat transfer coefficient and the refrigerant type of the hydrogen liquefaction unit, the defrosting frequency is determined. Based on the defrosting frequency, the liquid level assessment result of the cold box used in the hydrogen liquefaction unit is determined.

[0007] The liquid level assessment method for the cold box of a hydrogen liquefaction device provided by this invention, when assessing defrosting in the hydrogen liquefaction process under cryogenic temperatures, refers to the heat and mass transfer principles of the frosting process in cryogenic temperatures. It combines the instantaneous rate curve of liquid hydrogen production with multiple preset experimental sampling logics, and uses a preset cold box testing device to differentially obtain multiple sets of physical property parameters corresponding to the cold box during the hydrogen liquefaction process. Furthermore, by determining the target cold release convection heat transfer coefficient through a preset cold release convection heat transfer coefficient relationship, it provides support for determining the defrosting frequency, avoiding frequent fixed-cycle defrosting operations. This method can more accurately guide the defrosting operation of the dynamic process combining the evaporation of the working fluid in the hydrogen liquefaction cold box and the injection of the working fluid into the cold box, thereby improving the technical and economic benefits of liquid hydrogen production to a certain extent. Furthermore, by combining the determined defrosting frequency with the liquid level assessment results of the cold box used in the hydrogen liquefaction unit, a simple and practical selection reference is provided for delaying and suppressing frost in the hydrogen liquefaction unit, which to some extent improves the operational efficiency of the dynamic process combining the evaporation of the working fluid in the cold box and the injection of the refrigerant into the cold box.

[0008] In one optional implementation, based on the instantaneous rate curve and multiple preset test sampling logics, a preset cold box testing device is used to obtain a set of multiple physical property parameters corresponding to the cold box during the hydrogen liquefaction process of the hydrogen liquefaction device, including:

[0009] The refrigeration section of the hydrogen liquefaction unit is obtained; based on the refrigeration section and the type of refrigerant, a preset ratio is determined; based on the instantaneous rate curve, the time when the instantaneous rate of liquid hydrogen preparation in the hydrogen liquefaction unit is greater than the preset ratio of the rated rate of liquid hydrogen preparation is identified and statistically analyzed to obtain the identification and statistical results; based on the identification and statistical results and multiple preset test sampling logics, multiple physical property parameter sets corresponding to the cold box in the hydrogen liquefaction process are obtained using a preset cold box test device.

[0010] The present invention provides a liquid level assessment method for a cold box in a hydrogen liquefaction device. This method identifies and statistically analyzes the time when the instantaneous rate of liquid hydrogen production exceeds a preset proportion of the rated liquid hydrogen production rate, based on the refrigeration section, refrigerant type, and instantaneous rate curve of the hydrogen liquefaction device. Furthermore, based on the identification and statistical results, and combined with multiple preset experimental sampling logics, a preset cold box testing device can differentially obtain multiple sets of physical property parameters corresponding to the cold box during the hydrogen liquefaction process.

[0011] In one optional implementation, based on identification statistical results and multiple preset experimental sampling logics, a preset cold box testing device is used to obtain a set of multiple physical property parameters corresponding to the cold box during the hydrogen liquefaction process of the hydrogen liquefaction device, including:

[0012] Based on the identification and statistical results, the number of tests is determined. Based on the number of tests and multiple preset test sampling logics, during the second time period, the preset cold box test device is used to test the temperature, absolute humidity, convection velocity and surface temperature of the incoming gas passing over the test contact cold plate surface of the cold box when the cold source enters the cold box during the hydrogen liquefaction process. Multiple sets of physical property parameters are obtained. The second time period reflects the time period that is adjacent to the target time and longer than the target time.

[0013] The liquid level assessment method for the cold box of the hydrogen liquefaction device provided by this invention can determine the number of tests by identifying statistical results. Furthermore, by combining multiple preset test sampling logics, within the number of tests, a preset cold box test device is used to test the temperature, absolute humidity, convection velocity, and surface temperature of the incoming gas passing over the test contact cold plate surface of the cold box when the cold source enters the cold box during the hydrogen liquefaction process. This allows for the differential acquisition and obtaining of multiple sets of physical property parameters corresponding to the cold box in the hydrogen liquefaction process.

[0014] In one optional implementation, based on multiple sets of physical property parameters, and after processing with a preset formula for the cold release convection heat transfer coefficient, the target cold release convection heat transfer coefficient is obtained, including:

[0015] Based on the refrigeration section and the type of refrigerant, the limit ratio of stable frost release convective heat transfer is determined. Based on the limit ratio of stable frost release convective heat transfer, the release convective heat transfer coefficient corresponding to each set of physical property parameters is calculated sequentially using the preset release convective heat transfer coefficient relationship, until the target release convective heat transfer coefficient that meets the conditions is obtained.

[0016] The liquid level assessment method for the cold box of the hydrogen liquefaction device provided by this invention, combined with different current refrigeration sections and refrigerant types, can determine the stable defrosting condensation heat transfer limit ratio value. Then, combined with the preset condensation condensation heat transfer coefficient relationship, the target condensation condensation heat transfer coefficient that meets the conditions can be calculated, which provides support for determining the defrosting frequency.

[0017] In one optional implementation, based on the stable frost-induced condensation heat transfer limit ratio, the condensation heat transfer coefficient corresponding to each set of physical property parameters is calculated sequentially using a preset condensation heat transfer coefficient relationship, until the target condensation heat transfer coefficient that meets the conditions is obtained, including:

[0018] Using a preset formula for the cold release convection heat transfer coefficient, the first cold release convection heat transfer coefficient corresponding to the first set of physical property parameters and the second cold release convection heat transfer coefficient corresponding to the second set of physical property parameters are calculated respectively. Based on the first and second cold release convection heat transfer coefficients, a target value is calculated. The target value is compared with the stable frost cold release convection heat transfer limit ratio. When the target value is less than the stable frost cold release convection heat transfer limit ratio, the second cold release convection heat transfer coefficient is determined as the target cold release convection heat transfer coefficient. When the target value is greater than the stable frost cold release convection heat transfer limit ratio, the cold release convection heat transfer coefficient corresponding to each set of physical property parameters is calculated sequentially using the preset formula for the cold release convection heat transfer coefficient and iterated repeatedly until the target cold release convection heat transfer coefficient that meets the conditions is obtained.

[0019] The method for assessing the liquid level of a cold box in a hydrogen liquefaction device provided by this invention calculates the cold convection heat transfer coefficient corresponding to each set of physical property parameters sequentially by using a preset cold release convection heat transfer coefficient relationship. By combining this with the stable frost cold convection heat transfer limit ratio, the target cold release convection heat transfer coefficient that meets the conditions can be determined, providing support for determining the defrosting frequency.

[0020] In one alternative implementation, the method further includes:

[0021] When the cold convection heat transfer coefficient corresponding to each set of physical property parameters is calculated sequentially using the preset cold convection heat transfer coefficient relationship and iterated repeatedly until the last cold convection heat transfer coefficient still does not meet the condition, the last cold convection heat transfer coefficient is determined as the target cold convection heat transfer coefficient.

[0022] The method for assessing the liquid level of a cold box in a hydrogen liquefaction device provided by this invention determines the final target cold convection heat transfer coefficient as the last calculated cold convection heat transfer coefficient if no cold convection heat transfer coefficient that meets the conditions has been calculated after all the cold convection heat transfer coefficients corresponding to the set of physical property parameters have been calculated.

[0023] In a second aspect, the present invention provides a liquid level assessment device for a cold box in a hydrogen liquefaction unit, the device comprising:

[0024] The first acquisition module is used to acquire the instantaneous rate curve of liquid hydrogen production in the hydrogen liquefaction device within a first time period, where the first time period reflects the time period adjacent to but shorter than the target time. The second acquisition module is used to acquire multiple sets of physical property parameters corresponding to the cold box used by the hydrogen liquefaction device during the hydrogen liquefaction process, based on the instantaneous rate curve and multiple preset test sampling logics, using a preset cold box test device. The processing module is used to obtain the target cold release convection heat transfer coefficient based on the multiple sets of physical property parameters and processed by a preset cold release convection heat transfer coefficient relationship. The first determination module is used to determine the defrosting frequency based on the target cold release convection heat transfer coefficient and the refrigerant type of the hydrogen liquefaction device. The second determination module is used to determine the liquid level assessment result of the cold box used by the hydrogen liquefaction device based on the defrosting frequency.

[0025] Thirdly, the present invention provides a computer device, comprising: a memory and a processor, the memory and the processor being communicatively connected to each other, the memory storing computer instructions, and the processor executing the computer instructions to perform the liquid level assessment method for a cold box in a hydrogen liquefaction apparatus as described in the first aspect or any corresponding embodiment thereof.

[0026] Fourthly, the present invention provides a computer-readable storage medium storing computer instructions for causing a computer to execute the liquid level assessment method for a cold box in a hydrogen liquefaction apparatus according to the first aspect or any corresponding embodiment described above.

[0027] Fifthly, the present invention provides a computer program product, including computer instructions for causing a computer to execute the liquid level assessment method for a cold box in a hydrogen liquefaction apparatus according to the first aspect or any corresponding embodiment thereof. Attached Figure Description

[0028] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0029] Figure 1 This is a schematic flowchart of a liquid level assessment method for a cold box in a hydrogen liquefaction device according to an embodiment of the present invention.

[0030] Figure 2 This is a schematic diagram of the instantaneous rate curve according to an embodiment of the present invention;

[0031] Figure 3 This is a schematic diagram of the structure of a preset cold box testing device according to an embodiment of the present invention;

[0032] Figure 4A This is a schematic diagram of the distribution of the T-type thermometer in the test contact cold plate plane according to an embodiment of the present invention;

[0033] Figure 4B This is a schematic diagram of the distribution of the T-type thermometer in the normal direction of the test contact cold plate plane according to an embodiment of the present invention;

[0034] Figure 5 This is a schematic flowchart of a liquid level assessment method for a cold box in a hydrogen liquefaction device according to another embodiment of the present invention.

[0035] Figure 6 This is a schematic flowchart of a liquid level assessment method for a cold box in a hydrogen liquefaction device according to another embodiment of the present invention.

[0036] Figure 7 This is a structural block diagram of a liquid level assessment device for a cold box in a hydrogen liquefaction apparatus according to an embodiment of the present invention;

[0037] Figure 8 This is a schematic diagram of the hardware structure of a computer device according to an embodiment of the present invention. Detailed Implementation

[0038] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0039] Currently, most defrosting methods refer to the defrosting principle under the general cooling temperature range. Under the general cooling temperature range, the air around the hydrogen liquefaction cold box, which has reached a certain humidity, comes into contact with the temperature below its dew point and undergoes heat exchange. Condensate droplets first form on the outer periphery of the liquefaction cold box, and then the droplets gradually freeze and eventually frost. Under this condition, the frost growth rate is relatively slow, and it is mostly in the form of blocky frost layers, so the frost density is relatively high. The frosting mechanism in the cryogenic temperature zone differs from that in the general cold temperature zone: a smaller volume fraction of the air surrounding the cold box first forms flake-like frost on the surface. As the frequency of frost separation gradually increases, the dispersed flake-like frost acts as a small cold source, causing most of the subsequent air surrounding the cold box to undergo sublimation due to sudden cooling between the cold box periphery and the flake-like frost. Consequently, a pseudo-blocky frost layer, resembling a blocky frost layer but with a relatively low density, grows in the contact area between the cold box periphery and the bottom layer of the accumulated dispersed flake-like frost. This layer will frequently regenerate, and the frosting frequency gradually increases as the refrigerant temperature decreases, resulting in significant adverse effects.

[0040] According to an embodiment of the present invention, a method for assessing the liquid level of a cold box for a hydrogen liquefaction device is provided. It should be noted that the steps shown in the flowchart in the accompanying drawings can be executed in a computer system such as a set of computer-executable instructions. Furthermore, although a logical order is shown in the flowchart, in some cases, the steps shown or described may be executed in a different order than that shown here.

[0041] This embodiment provides a method for assessing the liquid level in a cold box of a hydrogen liquefaction device, which can be used in electronic devices such as computers, mobile phones, and tablets. Figure 1 This is a flowchart of a liquid level assessment method for a cold box in a hydrogen liquefaction device according to an embodiment of the present invention, such as... Figure 1 As shown, the process includes the following steps:

[0042] Step S101: Obtain the instantaneous rate curve of liquid hydrogen preparation in the hydrogen liquefaction device during the first time period.

[0043] The first time period reflects the time period that is adjacent to the target time and is shorter than the target time.

[0044] Specifically, at the target time t0, the instantaneous rate curve of liquid hydrogen production by the hydrogen liquefaction unit in the hour preceding that time is obtained.

[0045] For example, the instantaneous rate curve is as follows: Figure 2 As shown.

[0046] Step S102: Based on the instantaneous rate curve and multiple preset test sampling logics, the preset cold box test device is used to obtain a set of multiple physical property parameters corresponding to the cold box in the hydrogen liquefaction process of the hydrogen liquefaction device.

[0047] Each set of physical property parameters may include the incoming gas temperature T. a Absolute humidity of incoming air ω a Incoming air convection velocity u a Test the surface temperature T of the contact cold plate. tcs .

[0048] Furthermore, the preset test sampling logic is the test sampling logic for physical property parameters. Specifically, the incoming gas temperature T a Absolute humidity of incoming air ω a Incoming air convection velocity u a Test the surface temperature T of the contact cold plate. tcs The experimental sampling logic is to test the surface temperature T of the contact cold plate. tcs The highest priority variable is the surface temperature T in contact with the cold plate. tcs Within the upper and lower limit range of the test values, the test is divided equally according to the upper limit number of the specified test group, and then the surface temperature T of the contact cold plate is tested. tcsThe sampling is performed from the upper limit to the lower limit in sequence with the incoming gas temperature T. a Lower limit of value, absolute humidity of incoming air ω a Lower limit of value, incoming air convection velocity u a Combined with the upper limit of the value.

[0049] Furthermore, the incoming gas temperature T a The next highest priority among variables is the incoming gas temperature T. a Within the upper and lower limit range of the test values, the test group is divided equally according to the upper limit number of the specified test group, and then the incoming gas temperature T is... a The sampling is performed from the minimum value that can be obtained at this time (tests that have already been carried out will not be repeated) to the upper limit, sequentially corresponding to the surface temperature T of the cold plate in contact with the test. tcs Upper limit of value, absolute humidity of incoming air ω a Lower limit of value, incoming air convection velocity u a Combined with the upper limit of the value.

[0050] Furthermore, the absolute humidity ω of the surrounding air a The next highest priority among variables is the absolute humidity ω of the incoming air. a Within the upper and lower limit range of the test values, the test group is divided equally according to the upper limit number of the specified test group, and then the absolute humidity ω of the incoming air is... a The sampling is performed from the minimum value that can be obtained at this time (tests that have already been carried out will not be repeated) to the upper limit, sequentially corresponding to the surface temperature T of the cold plate in contact with the test. tcs Upper limit of value, absolute humidity of incoming air ω a Lower limit of value, incoming air convection velocity u a Combined with the upper limit of the value.

[0051] Furthermore, the incoming air convection velocity u a As the last variable in priority, the incoming air convection velocity u a The test values ​​are divided equally within the upper and lower limit range according to the upper limit number of the specified test group, and then the incoming air convection velocity u is... a The sampling is performed from the maximum value that can be obtained at this point (tests that have already been conducted will not be repeated) to the lower limit, sequentially with the surface temperature T of the cold plate in contact with the refrigeration test. tcs Upper limit of value, absolute humidity of incoming air ω a Lower limit of value, incoming air convection velocity u a Combined with the upper limit of the value.

[0052] Specifically, when a certain refrigerant enters the cold box of the hydrogen liquefaction unit during the hydrogen liquefaction process, the temperature and humidity control device of the cold box continuously and stably blows air onto the test contact cold plate of the cold box, so that the temperature of the incoming gas passing over the surface of the test contact cold plate of the cold box is T. a In T a1 ~Ta2 Range, absolute humidity of incoming air ω a At ω a1 ~ω a2 Range, incoming air convection velocity u a In u a1 ~u a2 Range, test surface temperature T of the cold plate tcs In T tcs1 ~T tcs2 scope.

[0053] Furthermore, by combining the obtained instantaneous rate curves and multiple preset experimental sampling logics, a set of multiple physical property parameters of the hydrogen liquefaction device during the hydrogen liquefaction process is obtained using a preset cold box testing device.

[0054] Furthermore, a pre-set cold box testing device, such as Figure 3 As shown, it includes: a test contact cold plate 1; a defrost temperature measuring baffle 2; a heat flux and liquid level sensing plate 3; a heat flux and liquid level sensing buffer sleeve 4; a liquid level measuring rod 5; a heat flux measuring rod 6; a cold box shell 7; a cold box insulation layer 8; a data transmission line 9; a cold source inlet 10; and an evaporation gas outlet 11.

[0055] Specifically, the side of the incoming airflow passing over the test contact cold plate 1 is a superhydrophobic layer treated surface. This surface is treated by sandblasting a type II metal (such as copper, bronze alloy, brass alloy) surface with oxide type I metal (such as tin, vanadium, titanium, aluminum) particles, followed by treatment with a fluoride liquid containing a mass fraction of Γ. fl (Γ fl Amorphous polytetrafluoroethylene fluoropolymer (range: 0.5–1.2 wt%) was used at a rotation speed of ω. tf (ω tf Spin coating is performed at rotation speeds ranging from 220 to 600 r / min. Furthermore, the side of the defrosting temperature measuring baffle 2 in contact with the surface is made of a Class II metal (such as copper, bronze alloy, or brass alloy). Furthermore, the materials of other parts of the test contact cold plate 1 can be selected from any metal based on economic principles.

[0056] Furthermore, on the side of the test contact cold plate 1 that is swept by the incoming airflow, five T-type calorimeters were installed at points A to E on this surface to record the temperature T of the frost layer in contact with the test contact cold plate 1. f,surf and humidity w f,surf The temperature T of the frost layer in contact with the test contact cold plate 1 f,surf and humidity w f,surf The value is the average of the readings measured by the T-type calorimeter at five points A to E. The distribution of the T-type calorimeter on the test contact cold plate 1 plane and along the normal direction of the test contact cold plate 1 plane are as follows: Figure 4A and Figure 4B As shown.

[0057] Furthermore, such as Figure 4A As shown, on the plane of the test contact cold plate 1, the center of calorimeter E coincides with the center of the test contact cold plate 1. The centers of calorimeters A, C, and E are on a straight line, and the horizontal distance L between the centers of calorimeters A and C and the center of calorimeter E is... M =0.3L p (L p (To test the length of contact cold plate 1); the centers of calorimeters B, D, and E are on a straight line, and the vertical distance W between the centers of calorimeters B and D and the center of calorimeter E is... M =0.35W p (W p (To test the width of contact cold plate 1).

[0058] Furthermore, such as Figure 4B As shown, regarding the normal direction of the test contact cold plate 1 plane, the calorimeter 12 is located on the side where the incoming gas passes, and the distance T between its top and the test contact cold plate 1 plane is... S =α1T P (T P (To test the thickness of the contact cold plate 1), α1 is the average distribution coefficient of the frost layer, which is related to the refrigerant.

[0059] The potential refrigeration sections for the hydrogen liquefaction unit may include a precooling section and an isentropic expansion section. Potential cold sources (refrigerants) for the precooling section include LN2 (liquid nitrogen) and azeotropic refrigerants, while the potential cold source for the isentropic expansion section is LN2 (liquid hydrogen). Furthermore, "potential" means that it may exist, but is not guaranteed to exist. Therefore, the specific values ​​of α1 are as follows:

[0060] (1) If the section being addressed is the pre-cooling section of hydrogen liquefaction and the cold source is LN2 (liquid nitrogen), then the value of α1 is 0.255.

[0061] (2) If the section being addressed is the pre-cooling section of hydrogen liquefaction, and the cold source is a certain azeotropic mixture refrigerant suitable for cryogenic temperature range, then the value of α1 is 0.116.

[0062] (3) If the section being addressed is the isentropic expansion section of hydrogen liquefaction and the cold source is LH2 (liquid hydrogen), then the value of α1 is 0.084.

[0063] Furthermore, the material of the defrosting temperature measurement barrier 2 is an inorganic non-metallic material with poor thermal conductivity and high hardness. This barrier serves two purposes: firstly, it facilitates the insertion of a temperature sensor between itself and the test contact cold plate 1 to detect the surface temperature of the test contact cold plate 1; secondly, it protects the heat flux and liquid level sensing plate 3 from direct contact with the test contact cold plate 1, thereby ensuring the measurement accuracy of the heat flux and liquid level sensing plate 3.

[0064] Furthermore, the heat flux and liquid level sensing plate 3 is embedded with a heat flux sensor and a liquid level sensor for recording and processing heat flux and liquid level data.

[0065] Furthermore, the heat flux and liquid level sensing buffer sleeve 4 can flexibly connect the heat flux and liquid level sensing plate 3, the liquid level measuring rod 5, and the heat flux measuring rod 6.

[0066] Furthermore, the liquid level measuring rod 5 can sense the surface of the working fluid liquid level and connect the liquid level surface inside the cold box with the heat flux and liquid level sensing plate 3, which facilitates the measurement of the refrigerant liquid level.

[0067] Furthermore, the heat flux measuring rod 6 can be connected to the refrigerant and heat flux sensor plate 3 inside the cold box, which facilitates the measurement of the heat flux of frost release.

[0068] Furthermore, the cold box shell 7 can provide a place to store the refrigerant after it has been injected into the cold box.

[0069] Furthermore, the cold box insulation layer 8 can keep the refrigerant cold after it is injected into the cold box, minimizing the evaporation of the refrigerant.

[0070] Furthermore, data transmission line 9 can transmit heat flux data during the frost release process after the incoming airflow passes over the surface of the test contact cold plate 1, temperature and humidity data of the frost layer on the surface of the test contact cold plate 1, and liquid level data of the cold box.

[0071] Furthermore, the cold source inlet 10 is used to inject cold source into the cold box for storage.

[0072] Furthermore, the evaporation outlet 11 can transfer the refrigerant injected into the cold box to the hydrogen liquefaction unit, or evaporate and be discharged from the cold box during the cold storage process of the refrigerant in the cold box.

[0073] Step S103: Based on multiple sets of physical property parameters, the target condensation heat transfer coefficient is obtained by processing the preset condensation heat transfer coefficient relationship.

[0074] Specifically, the pre-defined relationship for the heat transfer coefficient of the cold release convection is shown in the following equation (1):

[0075]

[0076] In the formula: Q represents the heat flux (W / m²) during the evaporation and cooling process of the cold source, when the frost produced in contact with the cold plate 1 in the cold box undergoes heat exchange with the cold plate 1 in the cold box. 2 The heat flux can be measured by combining the heat flux in the pre-set cold box test device with the liquid level sensor plate 3 and the heat flux measuring rod 6; T f,surf The temperature (K) of the frost layer in contact with the test contact cold plate 1 can be measured by a calorimeter on the test contact cold plate 1;a The velocity of the incoming airflow (m / s); w a Indicates the absolute humidity of the incoming air (kg / kg) a );w f,surf This indicates the humidity (kg / kg) of the frost layer in contact with the test contact cold plate 1. a The result can be obtained by measuring the calorimeter on the test contact cold plate 1; The cold release kinetic factor in the cryogenic temperature range is a dimensionless number used to characterize the degree of frost formation on the surface of the cold plate 1 in the cold box test as a function of temperature difference, as shown in the following equation (2):

[0077]

[0078] In the formula: T a Indicates the temperature of the incoming airflow (K); T tp The value of T represents the triple point (K) of H₂O, which is 273.16 K; tca This indicates the surface temperature (K) of the test contact cold plate 1.

[0079] Specifically, the data obtained from the frost temperature measurement baffle 2 inside the pre-set cold box test device can be combined with the data processed by the heat flux and liquid level sensor 3 for display. The value of .

[0080] Step S104: Determine the defrosting frequency based on the target condensation heat transfer coefficient and the type of refrigerant in the hydrogen liquefaction device.

[0081] Specifically, under a specified refrigerant type and a specified target condensation heat transfer coefficient between the frost layer and the incoming gas, the defrosting frequency of the potential refrigerant in the hydrogen liquefaction unit is shown in Table 1:

[0082] Table 1. Defrosting frequency values ​​of the potential working fluid before the hydrogen liquefaction unit under the maximum and weighted average range of different target condensation heat transfer coefficients.

[0083]

[0084]

[0085] Step S105: Determine the liquid level assessment result of the cold box for the hydrogen liquefaction unit based on the defrosting frequency.

[0086] Specifically, by combining the obtained defrosting frequency, it can be determined whether the existing refrigerant level change pattern in the cold box is charging or transferring, and the corresponding rate of change, as shown in Table 2:

[0087] Table 2. Changes in liquid level filling / transfer mode and process rate in hydrogen liquefaction cold box under different defrosting frequencies and liquid levels.

[0088]

[0089]

[0090] The liquid level assessment method for the cold box of the hydrogen liquefaction unit provided in this embodiment, when assessing defrosting in the hydrogen liquefaction process under cryogenic temperatures, refers to the heat and mass transfer principles of the frosting process under cryogenic temperatures. It combines the instantaneous rate curve of liquid hydrogen production with multiple preset experimental sampling logics, and uses a preset cold box testing device to differentially obtain multiple sets of physical property parameters corresponding to the cold box in the hydrogen liquefaction process. Furthermore, by determining the target cold release convection heat transfer coefficient through a preset cold release convection heat transfer coefficient relationship, it provides support for determining the defrosting frequency, avoiding frequent fixed-cycle defrosting operations. This method can more accurately guide the defrosting operation of the dynamic process combining the evaporation of the working fluid in the hydrogen liquefaction cold box and the injection of the working fluid into the cold box, thereby improving the technical and economic benefits of liquid hydrogen production to a certain extent. Furthermore, by combining the determined defrosting frequency with the liquid level assessment results of the cold box used in the hydrogen liquefaction unit, a simple and practical selection reference is provided for delaying and suppressing frost in the hydrogen liquefaction unit, which to some extent improves the operational efficiency of the dynamic process combining the evaporation of the working fluid in the cold box and the injection of the refrigerant into the cold box.

[0091] This embodiment provides a method for assessing the liquid level in a cold box of a hydrogen liquefaction device, which can be used in electronic devices such as computers, mobile phones, and tablets. Figure 5 This is a flowchart of a liquid level assessment method for a cold box in a hydrogen liquefaction device according to an embodiment of the present invention, such as... Figure 5 As shown, the process includes the following steps:

[0092] Step S501: Obtain the instantaneous rate curve of liquid hydrogen production from the hydrogen liquefaction unit during the first time period. For details, please refer to [link to relevant documentation]. Figure 1 Step S101 of the illustrated embodiment will not be described again here.

[0093] Step S502: Based on the instantaneous rate curve and multiple preset test sampling logics, the preset cold box test device is used to obtain a set of multiple physical property parameters corresponding to the cold box in the hydrogen liquefaction process of the hydrogen liquefaction device.

[0094] Specifically, step S502 above includes:

[0095] Step S5021: Obtain the refrigeration section of the hydrogen liquefaction unit.

[0096] Specifically, as described in step S102 above, the refrigeration section of the hydrogen liquefaction unit may include a precooling section and an isentropic expansion section.

[0097] Step S5022: Determine the preset ratio based on the refrigeration section and the type of refrigerant.

[0098] The type of refrigerant is described in step S102 above.

[0099] Specifically, the preset ratio P LHer The value of reflects the spontaneity of evaporation and frosting of the working fluid after it enters the cold box, and is related to the type of refrigerant in the hydrogen liquefaction unit. The proportion P LHer The smaller the value, the stronger the spontaneous frosting of the refrigerant. Specific values ​​are as follows:

[0100] (1) If the section being addressed is the pre-cooling section of hydrogen liquefaction, and the cold source is LN2 (liquid nitrogen), then P LHer The value is 0.682.

[0101] (2) If the section being addressed is the pre-cooling section for hydrogen liquefaction, and the cold source is an azeotropic refrigerant suitable for cryogenic temperatures, then P LHer The value is 0.268.

[0102] (3) If the section being treated is an isentropic expansion section of hydrogen liquefaction, and the cold source is LH2 (liquid hydrogen), then P LHer The value is 0.226.

[0103] Step S5023: Based on the instantaneous rate curve, identify and statistically analyze the time when the instantaneous rate of liquid hydrogen preparation in the hydrogen liquefaction device is greater than a preset proportion of the rated rate of liquid hydrogen preparation, and obtain the identification and statistical results.

[0104] Specifically, the instantaneous rate curve is used to measure the instantaneous rate V of liquid hydrogen preparation in the hydrogen liquefaction unit. LHi Exceeding the rated liquid hydrogen production rate The proportion P LHer Time t LHer Identification and statistics are performed.

[0105] Where M represents the rated daily hydrogen production capacity of the hydrogen liquefaction unit.

[0106] Step S5024: Based on the identification statistics and multiple preset test sampling logics, the preset cold box test device is used to obtain a set of multiple physical property parameters corresponding to the cold box in the hydrogen liquefaction process of the hydrogen liquefaction device.

[0107] Specifically, based on the combination of identification statistical results and multiple pre-set experimental sampling logics, and utilizing methods such as... Figure 3 The preset cold box test device shown acquires a set of multiple physical property parameters corresponding to the cold box in the hydrogen liquefaction process of the hydrogen liquefaction device.

[0108] In some optional implementations, step S5024 above includes:

[0109] Step a1: Determine the number of trials based on the identification statistics.

[0110] Step a2: Based on the number of tests and multiple preset test sampling logics, during the second time period, the preset cold box test device is used to test the temperature of the incoming gas, absolute humidity of the incoming gas, convection velocity of the incoming gas and surface temperature of the cold plate surface of the cold box when the cold source enters the cold box during the hydrogen liquefaction process, and obtain multiple sets of physical property parameters.

[0111] The second time period reflects the time period that is adjacent to the target time and longer than the target time.

[0112] Specifically, based on the identification and statistical results, the temperature T of the incoming air flowing across the surface of the cold plate 1 tested by the preset cold box test device can be determined. a Absolute humidity of incoming air ω a Incoming air convection velocity u a Test the surface temperature T of the contact cold plate 1 tcs The maximum number of test groups is as follows:

[0113] (1) If it exceeds the proportion P LHer Time t LHer The proportion of the time in the sampling hour P Lhter If the content of the cold source is ≥0% and <7.5%, then the potential threat of frost formation on the outer periphery of the cold box is relatively small when a cold source enters the cold box during the hydrogen liquefaction process. Therefore, the temperature T of the incoming gas blown out by the temperature and humidity control device should not be activated temporarily. a absolute humidity ω a Convection velocity u a And test the surface temperature T of the contact cold plate 1 tcs The test sampling.

[0114] (2) If it exceeds the proportion P LHer Time t LHer The proportion of the time in the sampling hour P Lhter If the concentration of hydrogen liquefaction gas is ≥7.5% and <20%, then the temperature T of the incoming gas when a cold source enters the cold box during the hydrogen liquefaction process is... a absolute humidity ω a Convection velocity u a And test the surface temperature T of the contact cold plate 1 tcs The upper limit of the number of test groups was set at 2, 2, 1, and 1, respectively.

[0115] (3) If it exceeds the proportion P LHer Time t LHer The proportion of time P within the sampling hour LHter If the concentration of hydrogen is ≥20% and <45%, then the temperature T of the incoming gas when a cold source enters the cold box during the hydrogen liquefaction process is... a absolute humidity ωa Convection velocity u a And test the surface temperature T of the contact cold plate 1 tcs The upper limit of the number of test groups was set at 2, 2, 2, and 2, respectively.

[0116] (4) If it exceeds the proportion P LHer Time t LHer The proportion of time P within the sampling hour LHter If the concentration of hydrogen liquefaction gas is ≥45% and ≤100%, then the temperature T of the incoming gas when a cold source enters the cold box during the hydrogen liquefaction process is... a absolute humidity ω a Convection velocity u a And test the surface temperature T of the contact cold plate 1 tcs The maximum number of experimental groups was set at 3, 3, 2, and 2, respectively.

[0117] Furthermore, the temperature and humidity control device activates the blower operation, and the incoming airflow sweeps across the surface of the test contact cold plate 1. After a certain moment t0, it undergoes a transition period t1 between sheet-like frost and blocky frost. fsml That is, the physical property parameters required to be measured by the cold box testing device are obtained in the second time period.

[0118] Specifically, when obtaining physical property parameters using a preset cold box testing device, the preset test sampling logic described in step S102 above is used for testing and acquisition.

[0119] Furthermore, the transition period t between flaky and blocky frost fsml The value of is related to the type of refrigerant in the hydrogen liquefaction unit, as detailed below:

[0120] (1) If the section being treated is the pre-cooling section of hydrogen liquefaction, and the cold source is LN2 (liquid nitrogen), then t fsml The value is 35 minutes.

[0121] (2) If the section being addressed is the pre-cooling section for hydrogen liquefaction, and the cold source is an azeotropic refrigerant suitable for cryogenic temperatures, then t fsml The value is 10 minutes.

[0122] (3) If the section being treated is an isentropic expansion section of hydrogen liquefaction, and the cold source is LH2 (liquid hydrogen), then t fsml The value is 6 minutes.

[0123] Step S503: Based on multiple sets of physical property parameters, and after processing using a preset formula for the cold release convection heat transfer coefficient, the target cold release convection heat transfer coefficient is obtained. For details, please refer to [link to relevant documentation]. Figure 1 Step S103 of the illustrated embodiment will not be described again here.

[0124] Step S504: Determine the defrosting frequency based on the target cold release convection heat transfer coefficient and the type of refrigerant in the hydrogen liquefaction unit. For details, please refer to [link to relevant documentation]. Figure 1 Step S104 of the illustrated embodiment will not be described again here.

[0125] Step S505: Based on the defrosting frequency, determine the liquid level assessment result of the cold box used in the hydrogen liquefaction unit. For details, please refer to [link to relevant documentation]. Figure 1 Step S105 of the illustrated embodiment will not be described again here.

[0126] The liquid level assessment method for the cold box of the hydrogen liquefaction device provided in this embodiment refers to the heat and mass transfer principle of the frosting process in the cryogenic temperature zone when conducting defrosting assessment for the hydrogen liquefaction process. By analyzing the refrigeration section, refrigerant type, and instantaneous rate curve of the hydrogen liquefaction device, it identifies and statistically analyzes the time when the instantaneous rate of liquid hydrogen production in the hydrogen liquefaction device exceeds a preset proportion of the rated rate of liquid hydrogen production. The identification and statistical results then determine the number of tests. Furthermore, combining multiple preset test sampling logics, within the number of tests, a preset cold box testing device is used to test the temperature, absolute humidity, convection velocity, and surface temperature of the incoming gas passing over the test contact cold plate surface of the cold box when the cold source enters the cold box during the hydrogen liquefaction process. This allows for the differentiated acquisition and obtaining of multiple sets of physical property parameters corresponding to the cold box in the hydrogen liquefaction process. Furthermore, by pre-setting the relationship between the cooling release and convection heat transfer coefficients, the target cooling release and convection heat transfer coefficient is determined, providing support for determining the defrosting frequency. This avoids frequent, fixed-cycle defrosting operations and can more accurately guide the defrosting operation of the dynamic process combining the evaporation of the working fluid in the hydrogen liquefaction cold box and the injection of the working fluid into the cold box, thereby improving the technical and economic benefits of liquid hydrogen production to a certain extent. Furthermore, by combining the determined defrosting frequency with the liquid level assessment results of the cold box used in the hydrogen liquefaction unit, a simple and practical selection reference is provided for delaying and suppressing frost formation in the hydrogen liquefaction unit, further improving the operational efficiency of the dynamic process combining the evaporation of the working fluid in the cold box and the injection of the refrigerant into the cold box.

[0127] This embodiment provides a method for assessing the liquid level in a cold box of a hydrogen liquefaction device, which can be used in electronic devices such as computers, mobile phones, and tablets. Figure 6 This is a flowchart of a liquid level assessment method for a cold box in a hydrogen liquefaction device according to an embodiment of the present invention, such as... Figure 6 As shown, the process includes the following steps:

[0128] Step S601: Obtain the instantaneous rate curve of liquid hydrogen production from the hydrogen liquefaction unit during the first time period. For details, please refer to [link to relevant documentation]. Figure 1 Step S101 of the illustrated embodiment will not be described again here.

[0129] Step S602: Based on the instantaneous rate curve and multiple preset test sampling logics, a set of multiple physical property parameters corresponding to the cold box used in the hydrogen liquefaction process are obtained using a preset cold box testing device. For details, please refer to [link to relevant documentation]. Figure 5 Step S501 of the illustrated embodiment will not be described again here.

[0130] Step S603: Based on multiple sets of physical property parameters, the target condensation heat transfer coefficient is obtained by processing the preset condensation heat transfer coefficient relationship.

[0131] Specifically, step S603 includes:

[0132] Step S6031: Determine the stable defrosting and cooling convection heat transfer limit ratio based on the refrigeration section and the type of refrigerant.

[0133] Specifically, the limiting ratio of stable frost-releasing convective heat transfer is C. Lch The limiting ratio of stable frost-release convective heat transfer is related to the type of refrigerant in the hydrogen liquefaction unit. Lch The smaller the value, the stronger the spontaneous frosting property of the refrigerant. Specific values ​​are as follows:

[0134] (1) If the section being addressed is the pre-cooling section of hydrogen liquefaction, and the cold source is LN2 (liquid nitrogen), then C Lch The value is 3.5%.

[0135] (2) If the section being addressed is the pre-cooling section of hydrogen liquefaction, and the cold source is an azeotropic refrigerant suitable for cryogenic temperatures, then C Lch The value is 1.2%.

[0136] (3) If the section being treated is an isentropic expansion section of hydrogen liquefaction, and the cold source is LH2 (liquid hydrogen), then C Lch The value is 0.8%.

[0137] Step S6032: Based on the stable frost release convective heat transfer limit ratio, calculate the release convective heat transfer coefficient corresponding to each set of physical property parameters sequentially using the preset release convective heat transfer coefficient relationship, until the target release convective heat transfer coefficient that meets the conditions is obtained.

[0138] Specifically, the value of the condensation heat transfer coefficient between the frost layer and the incoming air is not taken for all incoming air temperatures T under the upper limit of the test group. a Absolute humidity of incoming air ω a Incoming air convection velocity u a Test the surface temperature T of the contact cold plate 1 tcsInstead of iterating through all the frost-bottom layer-incoming air cooling convection heat transfer coefficients obtained from the data sample points, the system sequentially calculates the cooling convection heat transfer coefficients corresponding to each set of physical property parameters using a preset cooling convection heat transfer coefficient relationship until the target cooling convection heat transfer coefficient that meets the conditions is obtained.

[0139] In some optional implementations, step S6032 above includes:

[0140] Step b1: Using the preset cold release convection heat transfer coefficient relationship, calculate the first cold release convection heat transfer coefficient corresponding to the first set of physical property parameters and the second cold release convection heat transfer coefficient corresponding to the second set of physical property parameters.

[0141] Step b2: Calculate the target value based on the first and second condensation heat transfer coefficients.

[0142] Step b3: Compare the target value with the stable frost release convective heat transfer limit ratio value.

[0143] Step b4: When the target value is less than the stable frost release convective heat transfer limit ratio, the second frost release convective heat transfer coefficient is determined as the target frost release convective heat transfer coefficient.

[0144] Step b5: When the target value is greater than the stable frost release convective heat transfer limit ratio, continue to use the preset frost release convective heat transfer coefficient relationship to calculate the frost release convective heat transfer coefficient corresponding to each set of physical property parameters in turn and iterate repeatedly until the target frost release convective heat transfer coefficient that meets the conditions is obtained.

[0145] Specifically, the value of the condensation heat transfer coefficient between the frost layer and the incoming airflow is determined by a criterion, which is as follows: Under the specified experimental sampling logic, the previously obtained condensation heat transfer coefficient between the frost layer and the incoming airflow is compared with the currently obtained condensation heat transfer coefficient between the frost layer and the incoming airflow. If the following conditions are met:

[0146] (1) The absolute value of the difference between the previously obtained frost-bottom layer-incoming air heat transfer coefficient (first frost-bottom layer-incoming air heat transfer coefficient) and the currently obtained frost-bottom layer-incoming air heat transfer coefficient (second frost-bottom layer-incoming air heat transfer coefficient), divided by the currently obtained frost-bottom layer-incoming air heat transfer coefficient (target value), is less than the limiting proportion C of stable frost frost frost frost convective heat transfer. Lch If the calculated condensation heat transfer coefficient between the frost layer and the incoming air is determined to be the specified condensation heat transfer coefficient between the frost layer and the incoming air, the next condensation heat transfer coefficient between the frost layer and the incoming air will not be calculated, and the next step of judgment will be performed.

[0147] (2) If the absolute value of the difference between the previously obtained frost-bottom layer-incoming air heat transfer coefficient and the currently obtained frost-bottom layer-incoming air heat transfer coefficient is greater than or equal to the current frost-bottom layer-incoming air heat transfer coefficient, then the result obtained by dividing the frost-bottom layer-incoming air heat transfer coefficient by the current frost-bottom layer-incoming air heat transfer coefficient is greater than or equal to the steady-state frost frost convective heat transfer limiting ratio C. Lch If the frost layer and the incoming air flow are satisfied, the next solution for the condensation heat transfer coefficient between the frost layer and the incoming air flow will be obtained. The comparison will continue according to the above criteria until the judgment conditions are met and the target condensation heat transfer coefficient is obtained.

[0148] Furthermore, step S6032 above also includes:

[0149] Step b6: When the cold convection heat transfer coefficient corresponding to each set of physical property parameters is calculated sequentially using the preset cold convection heat transfer coefficient relationship and iterated repeatedly until the last cold convection heat transfer coefficient still does not meet the condition, the last cold convection heat transfer coefficient is determined as the target cold convection heat transfer coefficient.

[0150] Specifically, if the specified conditions are not met even after obtaining the condensation heat transfer coefficient between the frost layer and the incoming air under all completed test groups, i.e., the last condensation heat transfer coefficient is calculated, then the last condensation heat transfer coefficient obtained between the frost layer and the incoming air is taken as the specified condensation heat transfer coefficient between the frost layer and the incoming air, i.e., the target condensation heat transfer coefficient.

[0151] Step S604: Determine the defrosting frequency based on the target cold release convection heat transfer coefficient and the type of refrigerant in the hydrogen liquefaction unit. For details, please refer to [link to relevant documentation]. Figure 1 Step S104 of the illustrated embodiment will not be described again here.

[0152] Step S605: Based on the defrosting frequency, determine the liquid level assessment result of the cold box used in the hydrogen liquefaction unit. For details, please refer to [link to relevant documentation]. Figure 1 Step S105 of the illustrated embodiment will not be described again here.

[0153] The liquid level assessment method for the cold box of the hydrogen liquefaction device provided in this embodiment refers to the heat and mass transfer principle of the frosting process in the cryogenic temperature zone when conducting defrosting assessment for the hydrogen liquefaction process. It combines the instantaneous rate curve of liquid hydrogen production and multiple preset test sampling logics, and uses a preset cold box testing device to differentially obtain multiple sets of physical property parameters corresponding to the cold box in the hydrogen liquefaction process. Furthermore, by combining different current refrigeration sections and refrigerant types, the stable frost release convection heat transfer limit ratio can be determined. Then, the release convection heat transfer coefficient corresponding to each set of physical property parameters is calculated sequentially through a preset release convection heat transfer coefficient relationship. By combining this with the stable frost release convection heat transfer limit ratio, the target release convection heat transfer coefficient that meets the conditions can be determined, providing support for determining the defrosting frequency. This avoids frequent fixed-cycle defrosting operations and can more accurately guide the defrosting operation of the dynamic process combining refrigerant evaporation in the hydrogen liquefaction cold box and refrigerant injection into the cold box, thereby improving the technical and economic benefits of liquid hydrogen production to a certain extent. Furthermore, by combining the determined defrosting frequency with the liquid level assessment results of the cold box used in the hydrogen liquefaction unit, a simple and practical selection reference is provided for delaying and suppressing frost in the hydrogen liquefaction unit, which to some extent improves the operational efficiency of the dynamic process combining the evaporation of the working fluid in the cold box and the injection of the refrigerant into the cold box.

[0154] In one example, a hydrogen liquefaction plant has a rated daily hydrogen production capacity of M = 1000 kg / d and is designed for the pre-cooling process section of liquid hydrogen production. The cold box accepts LN2 (liquid nitrogen) as the refrigerant for pre-cooling the liquid hydrogen.

[0155] When a certain refrigerant enters the cold box during the hydrogen liquefaction process, the temperature and humidity control device of the cold box continuously and stably blows air onto the test contact cold plate 1 of the cold box, so that the temperature of the incoming air passing over the surface of the test contact cold plate 1 is T. a The temperature range is 25-15℃, and the absolute humidity of the incoming air is ω. a The inflow gas convection velocity is in the range of 5.4–9 g / kga. a The surface temperature T of the test contact cold plate 1 is within the range of 2 to 4 m / s. tcs It is in the range of 110K to 90K.

[0156] After the temperature and humidity control device of the cold box continuously and stably blows air onto the test contact cold plate 1 of the cold box, the incoming air flows over the test contact cold plate 1 of the cold box and continuously frosts as the working fluid inside the cold box evaporates. The specific description of the cooling effect of the frost and the evaluation steps of the subsequent defrosting and liquid level change process operation inside the cold box is as follows:

[0157] The first step is to obtain the instantaneous rate curve of liquid hydrogen production from the hydrogen liquefaction unit during the period from 12:05:00 to 13:04:59 at 13:05:00 on a certain day, and to analyze the instantaneous rate V of liquid hydrogen production.LHi Exceeding the rated liquid hydrogen production rate The proportion P LHer Time t LHer Identification and statistical analysis were performed to determine the surface temperature T of the cold box testing device in contact with the cold plate 1. tcs The upper limit of the number of test groups.

[0158] Furthermore, since the section being addressed is the pre-cooling section for hydrogen liquefaction, and the cold source is LN2 (liquid nitrogen), then P LHer The value is 0.682.

[0159] Furthermore, such as Figure 2 As shown, due to exceeding the proportion P LHer Time t LHer proportion of the sampling hour And ≤100%, then when a cold source enters the cold box during the hydrogen liquefaction process, the temperature T of the incoming gas is... a absolute humidity ω a Convection velocity u a And test the surface temperature T of the contact cold plate 1 tcs The maximum number of experimental groups was set at 3, 3, 2, and 2, respectively.

[0160] The second step involves activating the temperature and humidity control device to blow air across the surface of the test contact cold plate 1. Since the section being tested is the pre-cooling section for hydrogen liquefaction, the cold source is LN2 (liquid nitrogen). The transition period from sheet-like frost to blocky frost is t... fsml =35 minutes, that is, the physical property parameters required to be measured by the cold box test device should be obtained at 13:40:00. The measured physical property parameters should be combined and the condensation heat transfer coefficient h between the frost bottom layer and the incoming air should be obtained by referring to the specified formula for the condensation heat transfer coefficient between the frost bottom layer and the incoming air.

[0161] Specifically, regarding the test contact cold plate 1 on the side swept by the incoming airflow, five T-type calorimeters were installed on this surface at points A to E respectively. The frost layer temperature T measured at points A, B, C, D, and E was... f,surfA T f,surfB T f,surfC T f,surfD T f,surfE The average temperature can be obtained from the values ​​of 142.2K, 142.1K, 142.4K, 142.2K, and 142.1K. Points A, B, C, D, and E: frost layer humidity w f,surfA w f,surfB w f,surfC w f,surfD w f,surfE They are 0.0011 kg / kg respectively. a0.0010kg / kg a 0.0012kg / kg a 0.0011kg / kg a 0.0011kg / kg a The average humidity can be obtained.

[0162] Furthermore, the surface temperature T of the test contact cold plate 1 is measured by a temperature sensor inserted between the defrost temperature measuring baffle 2 and the test contact cold plate 1. tcs It is 110K.

[0163] Furthermore, using the heat flux and liquid level sensing plate 3 and the heat flux measuring rod 6, the heat flux Q1 = 1276 W / m during the frost release process between the frost bottom layer and the incoming airflow was measured. 2 ,

[0164] Furthermore, the measured physical properties are compared with the temperature T of the incoming air flowing across the surface of the test contact cold plate 1 of the preset cold box test device via the temperature and humidity control device. a =15℃, absolute humidity of incoming air ω a =5.4g / kg a Incoming air convection velocity u a =4m / s Combining these factors and referring to the specified formula for the condensation heat transfer coefficient between the frost layer and the incoming airflow, the condensation heat transfer coefficient h1 between the frost layer and the incoming airflow is calculated to be 9.079 W / (m²). 2 ·K).

[0165] Furthermore, due to the temperature T of the incoming air... a absolute humidity ω a Convection velocity u a And test the surface temperature T of the contact cold plate 1 tcs The experimental sampling logic for obtaining data is to test the surface temperature T of the contact cold plate 1. tcs The highest priority variable is the surface temperature T of the contact cold plate 1. tcs Within the upper and lower limit range of the test values, the test group is divided into equal parts according to the upper limit number of the specified test group, and then the surface temperature T of the contact cold plate 1 is tested. tcs The sampling is performed from the upper limit to the lower limit in sequence with the incoming gas temperature T. a Lower limit of value, absolute humidity of incoming air ω a Lower limit of value, incoming air convection velocity u a The upper limit of the value is combined. Therefore, at the temperature T of the incoming gas... a absolute humidity ω a Convection velocity u aWhen all values ​​remain constant, adjust the defrost temperature measuring baffle 2 so that the surface temperature T of the test contact cold plate 1 measured by the defrost temperature measuring baffle 2 is constant. tcs The reading is set to 100K, and after it stabilizes, the frost layer temperature T at points A to E on the side of the test contact cold plate 1 where the incoming airflow passes is measured. f,surfA T f,surfB T f,surfC T f,surfD T f,surfE The average temperatures were 136.9K, 136.9K, 137.0K, 136.9K, and 136.8K, respectively. Humidity at points A, B, C, D, and E (w) f,surfA w f,surfB w f,surfC w f,surfD w f,surfE They were 0.0009 kg / kg. a 0.0009kg / kg a 0.0010kg / kg a 0.0008kg / kg a 0.0009kg / kg a Average humidity Regarding the heat flux and liquid level sensor plate 3 and heat flux measuring rod 6, the heat flux Q2 during the frost release process between the frost bottom layer and the incoming airflow was measured to be 1181 W / m. 2 Then, the measured physical properties are compared with the temperature T of the incoming air flowing across the surface of the test contact cold plate 1 of the cold box controlled by the cold box temperature and humidity control device. a =15℃, absolute humidity of incoming air ω a =5.4g / kg a Incoming air convection velocity u a =4m / s Combining these factors and referring to the specified formula for the condensation heat transfer coefficient between the frost layer and the incoming airflow, the condensation heat transfer coefficient h2 between the frost layer and the incoming airflow is calculated to be 7.844 W / (m²). 2 ·K).

[0166] Furthermore, since the section being addressed is the pre-cooling section for hydrogen liquefaction, and the cold source is LN2 (liquid nitrogen), the limiting ratio of stable frost-release convective heat transfer is C. Lch The value is 3.5%.

[0167] Furthermore, comparing the obtained condensation heat transfer coefficient h2 between the frost layer and the incoming air with the currently obtained condensation heat transfer coefficient h1 between the frost layer and the incoming air, it was found that the difference between the previously obtained condensation heat transfer coefficient between the frost layer and the incoming air, divided by the obtained condensation heat transfer coefficient between the frost layer and the incoming air, yielded a value of 13.6%, which is greater than C. Lch =3.5%, proceed to the next step of solving for the condensation heat transfer coefficient between the frost layer and the incoming airflow.

[0168] Similarly, the heat flux Q3 = 1066 W / m is obtained by measuring the heat flux during the frost release process between the frost layer and the incoming airflow using the liquid level sensor plate 3 and the heat flux measuring rod 6. 2 The surface temperature T of the test contact cold plate 1 was measured by the defrosting temperature measuring baffle 2. tcs The temperature T of the incoming airflow passing over the surface of the cold plate 1 will be 90K. a =15℃, absolute humidity of incoming air ω a =5.4g / kg a Incoming air convection velocity u a =4m / s

[0169] Furthermore, the frost layer temperature T at points A to E on the surface of the contact cold plate 1 on the side swept by the incoming airflow was tested. f,surfA T f,surfB T f,surfC T f,surfD T f,surfE The average temperatures were 131.7K, 131.8K, 131.8K, 131.6K, and 131.6K, respectively. Humidity at points A, B, C, D, and E (w) f,surfA w f,surfB w f,surfC w f,surfD w f,surfE They were 0.0009 kg / kg. a 0.0008kg / kg a 0.0007kg / kg a 0.0008kg / kg a 0.0008kg / kg a Average humidity Combining the measured parameters, we obtain h3 = 6.836 W / (m²). 2 ·K).

[0170] Furthermore, since the section being addressed is the pre-cooling section for hydrogen liquefaction, and the cold source is LN2 (liquid nitrogen), the limiting ratio of stable frost-release convective heat transfer is C.Lch The value is 3.5%.

[0171] Furthermore, comparing the obtained condensation heat transfer coefficient h3 between the frost layer and the incoming air with the currently obtained condensation heat transfer coefficient h2 between the frost layer and the incoming air, it was found that the difference between the previously obtained condensation heat transfer coefficient and the obtained condensation heat transfer coefficient between the frost layer and the incoming air, divided by the obtained condensation heat transfer coefficient between the frost layer and the incoming air, yielded a value of 12.2%, which is greater than C. Lch =3.5%, proceed to the next step of solving for the condensation heat transfer coefficient between the frost layer and the incoming airflow.

[0172] Similarly, the heat flux and liquid level sensing plate 3 and the heat flux and liquid level sensing buffer sleeve 4 measured the heat flux Q4 = 1236 W / m during the frost release process between the frost bottom layer and the incoming airflow. 2 The surface temperature T of the test contact cold plate 1 was measured by the defrosting temperature measuring baffle 2. tcs The temperature T of the incoming gas flowing across the surface of the cold plate 1 will be 110K. a =20℃, absolute humidity of incoming air ω a =5.4g / kg a Incoming air convection velocity u a =4m / s

[0173] Furthermore, the frost layer temperature T at points A to E on the surface of the contact cold plate 1 on the side swept by the incoming airflow was tested. f,surfA T f,surfB T f,surfC T f,surfD T f,surfE The average temperatures were 146.4K, 146.6K, 146.5K, 146.5K, and 146.5K, respectively. Humidity at points A, B, C, D, and E (w) f,surfA w f,surfB w f,surfC w f,surfD w f,surfE They were 0.0009 kg / kg. a 0.0009kg / kg a 0.0010kg / kg a 0.0008kg / kg a 0.0009kg / kg a Average humidity Combining the measured parameters, we obtain h4 = 8.315 W / (m 2 ·K).

[0174] Furthermore, since the section being addressed is the pre-cooling section for hydrogen liquefaction, and the cold source is LN2 (liquid nitrogen), the limiting ratio of stable frost-release convective heat transfer is C. Lch The value is 3.5%.

[0175] Comparing the calculated condensation heat transfer coefficient h4 between the frost layer and the incoming air with the currently calculated condensation heat transfer coefficient h3, we find that the difference between the previously calculated and the current condensation heat transfer coefficient between the frost layer and the incoming air, divided by the current condensation heat transfer coefficient, yields a value of 17.9%, which is greater than C. Lch =3.5%, proceed to the next step of solving for the condensation heat transfer coefficient between the frost layer and the incoming airflow.

[0176] Similarly, the heat flux Q5 = 1136 W / m² was measured by the liquid level sensor plate 3 and the heat flux measuring rod 6 during the frost release process between the frost layer and the incoming airflow. 2 The surface temperature T of the test contact cold plate 1 was measured by the defrosting temperature measuring baffle 2. tcs The temperature T of the incoming gas flowing across the surface of the cold plate 1 will be 100K. a =20℃, absolute humidity of incoming air ω a =5.4g / kg a Incoming air convection velocity u a =4m / s

[0177] Furthermore, the frost layer temperature T at points A to E on the surface of the contact cold plate 1 on the side swept by the incoming airflow was tested. f,surfA T f,surfB T f,surfC T f,surfD T f,surfE The average temperatures were 139.7K, 139.6K, 139.6K, 139.5K, and 139.6K, respectively. Humidity at points A, B, C, D, and E (w) f,surfA w f,surfB w f,surfC w f,surfD w f,surfE They were 0.0009 kg / kg. a 0.0008kg / kg a 0.0010kg / kg a 0.0009kg / kg a 0.0009kg / kg a Average humidity Combining the measured parameters, we obtain h5 = 7.320 W / (m²).2 ·K).

[0178] Furthermore, since the section being addressed is the pre-cooling section for hydrogen liquefaction, and the cold source is LN2 (liquid nitrogen), the limiting ratio of stable frost-release convective heat transfer is C. Lch The value is 3.5%.

[0179] Furthermore, comparing the obtained condensation heat transfer coefficient h5 between the frost layer and the incoming air with the currently obtained condensation heat transfer coefficient h4, it was found that the difference between the previously obtained condensation heat transfer coefficient and the obtained condensation heat transfer coefficient between the frost layer and the incoming air, divided by the obtained condensation heat transfer coefficient between the frost layer and the incoming air, yielded a value of 12.6%, which is greater than C. Lch =3.5%, proceed to the next step of solving for the condensation heat transfer coefficient between the frost layer and the incoming airflow.

[0180] Similarly, the heat flux Q6 = 1042 W / m is obtained by measuring the heat flux during the frost release process between the frost layer and the incoming airflow using the liquid level sensor plate 3 and the heat flux measuring rod 6. 2 The surface temperature T of the test contact cold plate 1 was measured by the defrosting temperature measuring baffle 2. tcs The temperature T of the incoming airflow passing over the surface of the cold plate 1 will be 90K. a =20℃, absolute humidity of incoming air ω a =5.4g / kg a Incoming air convection velocity u a =4m / s

[0181] Furthermore, the frost layer temperature T at points A to E on the surface of the contact cold plate 1 on the side swept by the incoming airflow was tested. f,surfA T f,surfB T f,surfC T f,surfD T f,surfE The average temperatures were 135.4K, 135.3K, 135.3K, 135.2K, and 135.3K, respectively. Humidity at points A, B, C, D, and E (w) f,surfA w f,surfB W f,surfC w f,surfD w f,surfE They were 0.0008 kg / kg respectively. a 0.0007kg / kg a 0.0008kg / kg a 0.0008kg / kg a 0.0009kg / kg aAverage humidity Combining the measured parameters, we obtain h6 = 6.692 W / (m 2 ·K).

[0182] Furthermore, since the section being addressed is the pre-cooling section for hydrogen liquefaction, and the cold source is LN2 (liquid nitrogen), the limiting ratio of stable frost-release convective heat transfer is C. Lch The value is 3.5%.

[0183] Furthermore, comparing the obtained condensation heat transfer coefficient h6 between the frost layer and the incoming air with the currently obtained condensation heat transfer coefficient h5 between the frost layer and the incoming air, it was found that the difference between the previously obtained condensation heat transfer coefficient and the obtained condensation heat transfer coefficient between the frost layer and the incoming air, divided by the obtained condensation heat transfer coefficient between the frost layer and the incoming air, yielded a value of 8.6%, which is greater than C. Lch =3.5%, proceed to the next step of solving for the condensation heat transfer coefficient between the frost layer and the incoming airflow.

[0184] Similarly, the heat flux Q7 = 1172 W / m² was measured by the liquid level sensor plate 3 and the heat flux measuring rod 6 during the frost release process between the frost layer and the incoming airflow. 2 The surface temperature T of the test contact cold plate 1 was measured by the defrosting temperature measuring baffle 2. tcs The temperature T of the incoming gas flowing across the surface of the cold plate 1 will be 110K. a =25℃, absolute humidity of incoming air ω a =5.4g / kg a Incoming air convection velocity u a =4m / s

[0185] Furthermore, the frost layer temperature T at points A to E on the surface of the contact cold plate 1 on the side swept by the incoming airflow was tested. f,surfA T f,surfB T f,surfC T f,surfD T f,surfE The average temperatures were 143.0 K, 142.9 K, 143.0 K, 143.1 K, and 143.0 K, respectively. Humidity at points A, B, C, D, and E (w) f,surfA w f,surfB w f,surfC w f,surfD w f,surfE They were 0.0008 kg / kg respectively. a 0.0007kg / kg a 0.0008kg / kg a0.0008kg / kg a 0.0009kg / kg a Average humidity Combining the measured parameters, we obtain h7 = 7.571 W / (m²). 2 ·K).

[0186] Furthermore, since the section being addressed is the pre-cooling section for hydrogen liquefaction, and the cold source is LN2 (liquid nitrogen), the limiting ratio of stable frost-release convective heat transfer is C. Lch The value is 3.5%.

[0187] Furthermore, comparing the obtained condensation heat transfer coefficient h7 between the frost layer and the incoming air with the currently obtained condensation heat transfer coefficient h6 between the frost layer and the incoming air, it was found that the difference between the previously obtained condensation heat transfer coefficient and the obtained condensation heat transfer coefficient between the frost layer and the incoming air, divided by the obtained condensation heat transfer coefficient between the frost layer and the incoming air, yielded a value of 13.1%, which is greater than C. Lch =3.5%, proceed to the next step of solving for the condensation heat transfer coefficient between the frost layer and the incoming airflow.

[0188] Similarly, the heat flux Q8 = 1088 W / m² was measured by the liquid level sensor plate 3 and the heat flux measuring rod 6 during the frost release process between the frost layer and the incoming airflow. 2 The surface temperature T of the test contact cold plate 1 was measured by the defrosting temperature measuring baffle 2. tcs The temperature T of the incoming gas flowing across the surface of the cold plate 1 will be 100K. a =25℃, absolute humidity of incoming air ω a =5.4g / kg a Incoming air convection velocity u a =4m / s

[0189] Furthermore, the frost layer temperature t at points A to E on the surface of the contact cold plate 1 on the side swept by the incoming airflow was tested. f,surfA T f,surfB T f,surfC T f,surfD T f,surfE The average temperatures were 140.8K, 140.8K, 140.6K, 140.7K, and 140.6K, respectively. Humidity at points A, B, C, D, and E (w) f,surfA w f,surfB w f,surfC w f,surfD w f,surfE They were 0.0009 kg / kg. a0.0008kg / kg a 0.0007kg / kg a 0.0008kg / kg a 0.0008kg / kg a Average humidity Combining the measured parameters, we obtain h8 = 6.905 W / (m²). 2 ·K).

[0190] Furthermore, since the section being addressed is the pre-cooling section for hydrogen liquefaction, and the cold source is LN2 (liquid nitrogen), the limiting ratio of stable frost-release convective heat transfer is C. Lch The value is 3.5%.

[0191] Furthermore, comparing the calculated condensation heat transfer coefficient h8 between the frost layer and the incoming air with the currently calculated condensation heat transfer coefficient h7, we find that the difference between the previously calculated and the current condensation heat transfer coefficient between the frost layer and the incoming air, divided by the current condensation heat transfer coefficient, yields a value of 8.8%, which is greater than C. Lch =3.5%, proceed to the next step of solving for the condensation heat transfer coefficient between the frost layer and the incoming airflow.

[0192] Similarly, the heat flux Q9 = 1026 W / m is obtained by measuring the heat flux during the frost release process between the frost layer and the incoming airflow using the liquid level sensor plate 3 and the heat flux measuring rod 6. 2 The surface temperature T of the test contact cold plate 1 was measured by the defrosting temperature measuring baffle 2. tcs The temperature T of the incoming airflow passing over the surface of the cold plate 1 will be 90K. a =25℃, absolute humidity of incoming air ω a =5.4g / kg a Incoming air convection velocity u a =4m / s

[0193] Furthermore, the frost layer temperature T at points A to E on the surface of the contact cold plate 1 on the side swept by the incoming airflow was tested. f,surfA T f,surfB T f,surfC T f,surfD T f,surfE The average temperatures were 137.6K, 137.6K, 137.6K, 137.5K, and 137.7K, respectively. Humidity at points A, B, C, D, and E (w) f,surfA w f,surfB w f,surfC w f,surfDw f,surfE They were 0.0008 kg / kg respectively. a 0.0008kg / kg a 0.0008kg / kg a 0.0008kg / kg a 0.0008kg / kg a Average humidity Combining the measured parameters, we obtain h9 = 6.684 W / (m 2 ·K).

[0194] Furthermore, since the section being addressed is the pre-cooling section for hydrogen liquefaction, and the cold source is LN2 (liquid nitrogen), the limiting ratio of stable frost-release convective heat transfer is C. Lch The value is 3.5%.

[0195] Furthermore, comparing the obtained condensation heat transfer coefficient h9 between the frost layer and the incoming air with the currently obtained condensation heat transfer coefficient h8 between the frost layer and the incoming air, it was found that the difference between the previously obtained condensation heat transfer coefficient and the obtained condensation heat transfer coefficient between the frost layer and the incoming air, divided by the obtained condensation heat transfer coefficient between the frost layer and the incoming air, yielded a value of 6.1%, which is greater than C. Lch =3.5%, proceed to the next step of solving for the condensation heat transfer coefficient between the frost layer and the incoming airflow.

[0196] Similarly, the heat flux Q during the frost release process between the frost layer and the incoming airflow is measured by the liquid level sensor plate 3 and the heat flux measuring rod 6. 10 =1062W / m 2 The surface temperature T of the test contact cold plate 1 was measured by the defrosting temperature measuring baffle 2. tcs The temperature T of the incoming gas flowing across the surface of the cold plate 1 will be 110K. a =15℃, absolute humidity of incoming air ω a =9g / kg a Incoming air convection velocity u a =4m / s

[0197] Furthermore, the frost layer temperature T at points A to E on the surface of the contact cold plate 1 on the side swept by the incoming airflow was tested. f,surfA T f,surfB T f,surfC T f,surfD T f,surfE The average temperatures were 142.6K, 142.8K, 142.5K, 142.7K, and 142.4K, respectively. Humidity at points A, B, C, D, and E (w)f,surfA w f,surfB w f,surfC w f,surfD w f,surfE They are 0.0015 kg / kg respectively. a 0.0014 kg / kg a 0.0014 kg / kg a 0.0013kg / kg a 0.0015kg / kg a Average humidity By combining the measured parameters, we can obtain h. 10 =7.383W / (m 2 ·K).

[0198] Furthermore, since the section being addressed is the pre-cooling section for hydrogen liquefaction, and the cold source is LN2 (liquid nitrogen), the limiting ratio of stable frost-release convective heat transfer is C. Lch The value is 3.5%.

[0199] Furthermore, the obtained convective heat transfer coefficient h between the frost layer and the incoming airflow is... 10 Comparing the calculated convective heat transfer coefficient h9 between the frost layer and the incoming air, it was found that the difference between the previously calculated and the current calculated convective heat transfer coefficient between the frost layer and the incoming air, divided by the current calculated convective heat transfer coefficient, yielded a value of 9.4%, which is greater than C. Lch =3.5%, proceed to the next step of solving for the condensation heat transfer coefficient between the frost layer and the incoming airflow.

[0200] Similarly, the heat flux Q during the frost release process between the frost layer and the incoming airflow is measured by the liquid level sensor plate 3 and the heat flux measuring rod 6. 11 =1033W / m 2 The surface temperature T of the test contact cold plate 1 was measured by the defrosting temperature measuring baffle 2. tcs The temperature T of the incoming gas flowing across the surface of the cold plate 1 will be 100K. a =15℃, absolute humidity of incoming air ω a =9g / kg a Incoming air convection velocity u a =4m / s

[0201] Furthermore, the frost layer temperature T at points A to E on the surface of the contact cold plate 1 on the side swept by the incoming airflow was tested. f,surfA T f,surfB T f,surfC T f,surfD T f,surfEThe average temperatures were 138.9K, 138.9K, 139.0K, 138.8K, and 138.9K, respectively. Humidity at points A, B, C, D, and E (w) f,surfA w f,surfB w f,surfC w f,surfD w f,surfE They are 0.0014 kg / kg respectively. a 0.0013kg / kg a 0.0013kg / kg a 0.0012kg / kg a 0.0013kg / kg a Average humidity By combining the measured parameters, we can obtain h. 11 =6.918W / (m 2 ·K).

[0202] Furthermore, since the section being addressed is the pre-cooling section for hydrogen liquefaction, and the cold source is LN2 (liquid nitrogen), the limiting ratio of stable frost-release convective heat transfer is C. Lch The value is 3.5%.

[0203] Furthermore, the obtained convective heat transfer coefficient h between the frost layer and the incoming airflow is... 11 The obtained condensation heat transfer coefficient h between the frost layer and the incoming airflow is compared with the value of the condensation heat transfer coefficient h. 10 Comparing the two, it was found that the difference between the previously calculated condensation heat transfer coefficient between the frost layer and the incoming air and the calculated condensation heat transfer coefficient between the frost layer and the incoming air, divided by the calculated condensation heat transfer coefficient between the frost layer and the incoming air, yielded a value of 5.4%, which is greater than C. Lch =3.5%, proceed to the next step of solving for the condensation heat transfer coefficient between the frost layer and the incoming airflow.

[0204] Similarly, the heat flux Q during the frost release process between the frost layer and the incoming airflow is measured by the liquid level sensor plate 3 and the heat flux measuring rod 6. 12 =1007W / m 2 The surface temperature T of the test contact cold plate 1 was measured by the defrosting temperature measuring baffle 2. tcs The temperature T of the incoming airflow passing over the surface of the cold plate 1 will be 90K. a =15℃, absolute humidity of incoming air ω a =9g / kg a Incoming air convection velocity u a =4m / s

[0205] Furthermore, the frost layer temperature T at points A to E on the surface of the contact cold plate 1 on the side swept by the incoming airflow was tested. f,surfA T f,surfB T f,surfC T f,surfD T f,surfE The average temperatures were 133.1K, 133.2K, 133.2K, 133.2K, and 133.3K, respectively. Humidity at points A, B, C, D, and E (w) f,surfA w f,surfB w f,surfC w f,surfD w f,surfE They are 0.0013 kg / kg respectively. a 0.0013kg / kg a 0.0013kg / kg a 0.0013kg / kg a 0.0012kg / kg a Average humidity By combining the measured parameters, we can obtain h. 12 =6.663W / (m 2 ·K).

[0206] Furthermore, since the section being addressed is the pre-cooling section for hydrogen liquefaction, and the cold source is LN2 (liquid nitrogen), the limiting ratio of stable frost-release convective heat transfer is C. Lch The value is 3.5%.

[0207] Furthermore, the obtained convective heat transfer coefficient h between the frost layer and the incoming airflow is... 12 The obtained condensation heat transfer coefficient h between the frost layer and the incoming airflow is compared with the value of the condensation heat transfer coefficient h. 11 Comparing the two, it was found that the difference between the previously calculated frost-bottom layer-incoming air heat transfer coefficient and the calculated frost-bottom layer-incoming air heat transfer coefficient, divided by the calculated frost-bottom layer-incoming air heat transfer coefficient, yielded a value of 3.7%, which is greater than C. Lch =3.5%, proceed to the next step of solving for the condensation heat transfer coefficient between the frost layer and the incoming airflow.

[0208] Similarly, the heat flux Q during the frost release process between the frost layer and the incoming airflow is measured by the liquid level sensor plate 3 and the heat flux measuring rod 6. 13 =974W / m 2 The surface temperature T of the test contact cold plate 1 was measured by the defrosting temperature measuring baffle 2. tcs The temperature T of the incoming gas flowing across the surface of the cold plate 1 will be 110K. a =20℃, absolute humidity of incoming air ω a=9g / kg a Incoming air convection velocity u a =4m / s

[0209] Furthermore, the frost layer temperature T at points A to E on the surface of the contact cold plate 1 on the side swept by the incoming airflow was tested. f,surfA T f,surfB T f,surfC T f,surfD T f,surfE The temperatures were 148.9K, 148.8K, 148.9K, 149.0K, and 148.9K, respectively, with average temperatures. Humidity at points A, B, C, D, and E (w) f,surfA w f,surfB w f,surfC w f,surfD w f,surfE They are 0.0014 kg / kg respectively. a 0.0014 kg / kg a 0.0012kg / kg a 0.0012kg / kg a 0.0013kg / kg a Average humidity By combining the measured parameters, we can obtain h. 13 =6.870W / (m 2 ·K).

[0210] Furthermore, since the section being addressed is the pre-cooling section for hydrogen liquefaction, and the cold source is LN2 (liquid nitrogen), the limiting ratio of stable frost-release convective heat transfer is C. Lch The value is 3.5%.

[0211] Furthermore, the obtained convective heat transfer coefficient h between the frost layer and the incoming airflow is... 13 The obtained condensation heat transfer coefficient h between the frost layer and the incoming airflow is compared with the value of the condensation heat transfer coefficient h. 12 Comparing the two, it was found that the difference between the previously calculated frost-bottom layer-incoming air heat transfer coefficient and the calculated frost-bottom layer-incoming air heat transfer coefficient, divided by the calculated frost-bottom layer-incoming air heat transfer coefficient, yielded a value of 3.1%, which is less than C. Lch =3.5%, then the calculated convective heat transfer coefficient h between the frost layer and the incoming air is considered to be 3.5%. 13 =6.870W / (m 2 K) is the specified condensation heat transfer coefficient between the frost bottom layer and the incoming air, and the condensation heat transfer coefficient between the next frost bottom layer and the incoming air is not solved, and the next step is determined.

[0212] The third step is to determine the defrosting frequency by combining the specified condensation heat transfer coefficient between the frost layer and the incoming airflow and the type of refrigerant.

[0213] When targeting the precooling section and specifying LN2 (liquid nitrogen) as the refrigerant type, the specified convective heat transfer coefficient h between the frost layer and the incoming air is used. 13 =6.870W / (m 2 According to Table 1, the recommended defrosting frequency for the LN2 (liquid nitrogen) working fluid in the precooling section of the hydrogen liquefaction unit is 10 times per minute.

[0214] Fourth, when facing the pre-cooling section, the refrigerant type is specified as LN2 (liquid nitrogen), and the obtained defrosting frequency recommendation is 10 times per minute, which is in the case of 8 to 12 times per minute. Therefore, the liquid level filling / transfer mode is "fillable and cold storage". In this mode, it should also be noted that if it is necessary to fill the cold box in the hydrogen liquefaction unit, the rate should be 90% of the rated rate.

[0215] This embodiment also provides a liquid level assessment device for a cold box in a hydrogen liquefaction unit. This device is used to implement the above embodiments and preferred embodiments, and details already described will not be repeated. As used below, the term "module" can refer to a combination of software and / or hardware that performs a predetermined function. Although the devices described in the following embodiments are preferably implemented in software, hardware implementation, or a combination of software and hardware, is also possible and contemplated.

[0216] This embodiment provides a liquid level assessment device for a cold box used in a hydrogen liquefaction unit, such as... Figure 7 As shown, the device includes:

[0217] The first acquisition module 701 is used to acquire the instantaneous rate curve of liquid hydrogen production by the hydrogen liquefaction device within a first time period, wherein the first time period reflects the time period that is adjacent to the target time and shorter than the target time.

[0218] The second acquisition module 702 is used to acquire a set of multiple physical property parameters corresponding to the cold box in the hydrogen liquefaction process of the hydrogen liquefaction device based on the instantaneous rate curve and multiple preset test sampling logic, using a preset cold box test device.

[0219] The processing module 703 is used to obtain the target condensation heat transfer coefficient based on multiple sets of physical property parameters and through the processing of a preset condensation heat transfer coefficient relationship.

[0220] The first determining module 704 is used to determine the defrosting frequency based on the target cold release convection heat transfer coefficient and the type of refrigerant in the hydrogen liquefaction device.

[0221] The second determining module 705 is used to determine the liquid level assessment result of the cold box for the hydrogen liquefaction unit based on the defrosting frequency.

[0222] In some alternative implementations, the second acquisition module 702 includes:

[0223] The first acquisition submodule is used to acquire the refrigeration section of the hydrogen liquefaction unit.

[0224] The first determining submodule is used to determine the preset ratio based on the refrigeration section and the type of refrigerant.

[0225] The identification and statistics submodule is used to identify and statistically analyze the time when the instantaneous rate of liquid hydrogen production in the hydrogen liquefaction unit exceeds a preset proportion of the rated rate of liquid hydrogen production, based on the instantaneous rate curve, and obtain the identification and statistics results.

[0226] The second acquisition submodule is used to acquire a set of multiple physical property parameters corresponding to the cold box in the hydrogen liquefaction process of the hydrogen liquefaction device based on the identification statistical results and multiple preset experimental sampling logic, using a preset cold box test device.

[0227] In some optional implementations, the second acquisition submodule includes:

[0228] The first determining unit is used to determine the number of trials based on the identification statistics.

[0229] The acquisition unit is used to test the temperature, absolute humidity, convection velocity, and surface temperature of the incoming gas passing over the test contact cold plate surface of the cold box when the cold source enters the cold box during the hydrogen liquefaction process, based on the number of tests and multiple preset test sampling logics, and obtain multiple sets of physical property parameters. The second time period reflects the time period that is adjacent to the target time and longer than the target time.

[0230] In some alternative implementations, the processing module 703 includes:

[0231] The second determination submodule is used to determine the stable defrosting condensation heat transfer limit ratio based on the refrigeration section and the type of refrigerant.

[0232] The calculation submodule is used to calculate the condensation heat transfer coefficient corresponding to each set of physical property parameters sequentially based on the stable frost condensation heat transfer limit ratio value and the preset condensation heat transfer coefficient relationship, until the target condensation heat transfer coefficient that meets the conditions is obtained.

[0233] In some alternative implementations, the computation submodule includes:

[0234] The first calculation unit is used to calculate the first condensation heat transfer coefficient corresponding to the first set of physical property parameters and the second condensation heat transfer coefficient corresponding to the second set of physical property parameters, respectively, using the preset condensation heat transfer coefficient relationship.

[0235] The second calculation unit is used to calculate the target value based on the first and second condensation heat transfer coefficients.

[0236] The comparison unit is used to compare the target value with the stable frost-release convective heat transfer limit ratio value.

[0237] The second determining unit is used to determine the second condensation heat transfer coefficient as the target condensation heat transfer coefficient when the target value is less than the stable frost condensation heat transfer limit ratio.

[0238] The iterative unit is used to calculate the cold convection heat transfer coefficient corresponding to each set of physical property parameters in turn using the preset cold convection heat transfer coefficient relationship when the target value is greater than the stable frost cold convection heat transfer limit ratio value, and iterates repeatedly until the target cold convection heat transfer coefficient that meets the conditions is obtained.

[0239] In some optional implementations, the computation submodule further includes:

[0240] The third determining unit is used to determine the last refrigeration convection heat transfer coefficient as the target refrigeration convection heat transfer coefficient when the refrigeration convection heat transfer coefficient corresponding to each set of physical property parameters is calculated sequentially using the preset refrigeration convection heat transfer coefficient relationship and iterated repeatedly until the last refrigeration convection heat transfer coefficient still does not meet the condition.

[0241] Further functional descriptions of the above modules and units are the same as those in the corresponding embodiments described above, and will not be repeated here.

[0242] In this embodiment, the liquid level assessment device for the cold box of the hydrogen liquefaction device is presented in the form of a functional unit. Here, a unit refers to an ASIC (Application Specific Integrated Circuit) circuit, a processor and memory that execute one or more software or fixed programs, and / or other devices that can provide the above functions.

[0243] This invention also provides a computer device having the above-described features. Figure 7 The hydrogen liquefaction unit shown uses a liquid level assessment device for its cold box.

[0244] Please see Figure 8 , Figure 8 This is a schematic diagram of the structure of a computer device provided in an optional embodiment of the present invention, such as... Figure 8As shown, the computer device includes one or more processors 10, memory 20, and interfaces for connecting the components, including high-speed interfaces and low-speed interfaces. The components communicate with each other via different buses and can be mounted on a common motherboard or otherwise installed as needed. The processors can process instructions executed within the computer device, including instructions stored in or on memory to display graphical information of a GUI on external input / output devices (such as display devices coupled to the interfaces). In some alternative implementations, multiple processors and / or multiple buses can be used with multiple memories and multiple memory modules, if desired. Similarly, multiple computer devices can be connected, each providing some of the necessary operations (e.g., as a server array, a group of blade servers, or a multiprocessor system). Figure 8 Take a processor 10 as an example.

[0245] Processor 10 may be a central processing unit, a network processor, or a combination thereof. Processor 10 may further include a hardware chip. The hardware chip may be an application-specific integrated circuit (ASIC), a programmable logic device (PLD), or a combination thereof. The programmable logic device may be a complex programmable logic device (CAMP), a field-programmable gate array (FPGA), a general-purpose array logic (GDA), or any combination thereof.

[0246] The memory 20 stores instructions executable by at least one processor 10 to cause at least one processor 10 to perform the method shown in the above embodiments.

[0247] The memory 20 may include a program storage area and a data storage area. The program storage area may store the operating system and applications required for at least one function; the data storage area may store data created based on the use of the computer device. Furthermore, the memory 20 may include high-speed random access memory and may also include non-transitory memory, such as at least one disk storage device, flash memory device, or other non-transitory solid-state storage device. In some alternative embodiments, the memory 20 may optionally include memory remotely located relative to the processor 10, and these remote memories may be connected to the computer device via a network. Examples of such networks include, but are not limited to, the Internet, intranets, local area networks, mobile communication networks, and combinations thereof.

[0248] The memory 20 may include volatile memory, such as random access memory; the memory may also include non-volatile memory, such as flash memory, hard disk or solid-state drive; the memory 20 may also include a combination of the above types of memory.

[0249] The computer device also includes a communication interface 30 for communicating with other devices or communication networks.

[0250] This invention also provides a computer-readable storage medium. The methods described above according to embodiments of the invention can be implemented in hardware or firmware, or implemented as computer code that can be recorded on a storage medium, or implemented as computer code downloaded via a network and originally stored on a remote storage medium or a non-transitory machine-readable storage medium and then stored on a local storage medium. Thus, the methods described herein can be processed by software stored on a storage medium using a general-purpose computer, a dedicated processor, or programmable or dedicated hardware. The storage medium can be a magnetic disk, optical disk, read-only memory, random access memory, flash memory, hard disk, or solid-state drive, etc.; further, the storage medium can also include combinations of the above types of memory. It is understood that computers, processors, microprocessor controllers, or programmable hardware include storage components capable of storing or receiving software or computer code, which, when accessed and executed by the computer, processor, or hardware, implements the methods shown in the above embodiments.

[0251] A portion of this invention can be applied as a computer program product, such as computer program instructions, which, when executed by a computer, can invoke or provide the methods and / or technical solutions according to the invention through the operation of the computer. Those skilled in the art will understand that the forms in which computer program instructions exist in a computer-readable medium include, but are not limited to, source files, executable files, installation package files, etc. Correspondingly, the ways in which computer program instructions are executed by a computer include, but are not limited to: the computer directly executing the instructions, or the computer compiling the instructions and then executing the corresponding compiled program, or the computer reading and executing the instructions, or the computer reading and installing the instructions and then executing the corresponding installed program. Here, the computer-readable medium can be any available computer-readable storage medium or communication medium accessible to a computer.

[0252] Although embodiments of the invention have been described in conjunction with the accompanying drawings, those skilled in the art can make various modifications and variations without departing from the spirit and scope of the invention, and such modifications and variations all fall within the scope defined by the appended claims.

Claims

1. A method for assessing the liquid level in a cold box of a hydrogen liquefaction unit, characterized in that, The method includes: Obtain the instantaneous rate curve of liquid hydrogen production from the hydrogen liquefaction device within a first time period, wherein the first time period reflects the time period adjacent to the target time but shorter than the target time. Based on the instantaneous rate curve and multiple preset test sampling logics, a preset cold box test device is used to obtain multiple sets of physical property parameters corresponding to the cold box during the hydrogen liquefaction process of the hydrogen liquefaction device. Each set of physical property parameters includes incoming gas temperature, incoming gas absolute humidity, incoming gas convection velocity, and surface temperature of the test contact cold plate. The preset test sampling logic is the test sampling logic for the physical property parameters. The multiple preset test sampling logics perform test sampling in the following order: the surface temperature of the test contact cold plate as a variable has the highest priority, followed by the incoming gas temperature, then the absolute humidity of the surrounding gas, and finally the incoming gas convection velocity. Based on the aforementioned set of multiple physical property parameters, the target condensation heat transfer coefficient is obtained after processing with a preset formula for the condensation heat transfer coefficient. The defrosting frequency is determined based on the target condensation heat transfer coefficient and the type of refrigerant in the hydrogen liquefaction device. Based on the defrosting frequency, the liquid level assessment result of the cold box of the hydrogen liquefaction unit is determined. The liquid level assessment result is used to characterize the pattern and corresponding rate of change of the existing refrigerant liquid level in the cold box under the defrosting frequency. The preset cold release convection heat transfer coefficient relationship is expressed as follows: In the formula: Indicates the target heat transfer coefficient for heat release and convection; This represents the heat flux, in W / m², during the evaporation and cooling process of the cold source, when the frost produced in contact with the cold plate in the cold box undergoes heat exchange with the cold plate. 2 ; Indicates the temperature of the incoming airflow, in K; Indicates the temperature of the frost layer in contact with the test contact cold plate, in K; The velocity of the incoming airflow is expressed in m / s. Indicates the absolute humidity of the incoming air, kg / kg a ; This indicates the humidity of the frost layer in contact with the cold plate being tested, in kg / kg. a ; The cold release kinetic factor represents the cold temperature range and is a dimensionless number used to characterize the degree of frost formation on the surface of the cold plate in contact with the cold box as a function of temperature difference.

2. The method of claim 1, wherein, Based on the instantaneous rate curve and multiple preset test sampling logics, a set of multiple physical property parameters corresponding to the cold box during the hydrogen liquefaction process of the hydrogen liquefaction device are obtained using a preset cold box testing device, including: Obtain the refrigeration section of the hydrogen liquefaction unit; Based on the refrigeration section and the type of refrigerant, a preset ratio is determined; Based on the instantaneous rate curve, the time when the instantaneous rate of liquid hydrogen production in the hydrogen liquefaction device is greater than the preset proportion of the rated rate of liquid hydrogen production is identified and statistically analyzed to obtain the identification and statistical results. Based on the identification statistics and the multiple preset test sampling logic, the multiple physical property parameter sets corresponding to the cold box in the hydrogen liquefaction process of the hydrogen liquefaction device are obtained using the preset cold box test device.

3. The method of claim 2, wherein, Based on the identification statistics and the multiple preset test sampling logics, the multiple physical property parameter sets corresponding to the cold box in the hydrogen liquefaction process of the hydrogen liquefaction device are obtained using a preset cold box testing device, including: Based on the identification and statistical results, the number of trials is determined; Based on the number of tests and the multiple preset test sampling logics, during the second time period, the preset cold box test device is used to test the incoming gas temperature, absolute humidity, convection velocity, and surface temperature of the cold box when the cold source enters the cold box during the hydrogen liquefaction process, and obtain the multiple sets of physical property parameters. The second time period reflects the time period that is adjacent to the target time and longer than the target time.

4. The method of claim 2, wherein, Based on the aforementioned sets of physical property parameters, and after processing with a preset formula for the cold release convection heat transfer coefficient, the target cold release convection heat transfer coefficient is obtained, including: Based on the refrigeration section and the type of refrigerant, determine the limiting ratio of stable frost-release convective heat transfer. Based on the stable frost release convective heat transfer limit ratio, the release convective heat transfer coefficient corresponding to each of the physical property parameter sets is calculated sequentially using the preset release convective heat transfer coefficient relationship, until the target release convective heat transfer coefficient that meets the conditions is obtained.

5. The method of claim 4, wherein, Based on the stable frost release convective heat transfer limit ratio, the release convective heat transfer coefficient corresponding to each of the aforementioned physical property parameter sets is calculated sequentially using the preset release convective heat transfer coefficient relationship, until the target release convective heat transfer coefficient that meets the conditions is obtained, including: Using the preset cold release convection heat transfer coefficient relationship, calculate the first cold release convection heat transfer coefficient corresponding to the first set of physical property parameters and the second cold release convection heat transfer coefficient corresponding to the second set of physical property parameters. Calculate the target value based on the first and second cold release convective heat transfer coefficients. Compare the target value with the stable frost-release convective heat transfer limit ratio value; When the target value is less than the stable frost release convective heat transfer limit ratio, the second frost release convective heat transfer coefficient is determined as the target frost release convective heat transfer coefficient. When the target value is greater than the stable frost release convective heat transfer limit ratio, the release convective heat transfer coefficient corresponding to each set of physical property parameters is calculated sequentially using the preset release convective heat transfer coefficient relationship and iterated repeatedly until the target release convective heat transfer coefficient that meets the conditions is obtained.

6. The method of claim 5, wherein, The method further includes: When the preset cold release convection heat transfer coefficient relationship is used to calculate the cold release convection heat transfer coefficient corresponding to each set of physical property parameters in turn and iterates repeatedly until the last cold release convection heat transfer coefficient still does not meet the condition, the last cold release convection heat transfer coefficient is determined as the target cold release convection heat transfer coefficient.

7. A liquid level assessment device for a cold box in a hydrogen liquefaction unit, characterized in that, The device includes: The first acquisition module is used to acquire the instantaneous rate curve of liquid hydrogen production by the hydrogen liquefaction device within a first time period, wherein the first time period reflects the time period adjacent to the target time and shorter than the target time. The second acquisition module is used to acquire multiple sets of physical property parameters corresponding to the cold box in the hydrogen liquefaction process of the hydrogen liquefaction device based on the instantaneous rate curve and multiple preset test sampling logics, using a preset cold box test device. Each set of physical property parameters includes incoming gas temperature, incoming gas absolute humidity, incoming gas convection velocity, and surface temperature of the test contact cold plate. The preset test sampling logic is the test sampling logic for the physical property parameters. The multiple preset test sampling logics perform test sampling in the following order: the surface temperature of the test contact cold plate as a variable has the highest priority, followed by the incoming gas temperature as a variable, then the absolute humidity of the surrounding gas as a variable, and finally the incoming gas convection velocity as a variable. The processing module is used to obtain the target refrigeration convection heat transfer coefficient based on the multiple sets of physical property parameters and through the processing of the preset refrigeration convection heat transfer coefficient relationship. The first determining module is used to determine the defrosting frequency based on the target cold release convection heat transfer coefficient and the type of refrigerant in the hydrogen liquefaction device; The second determining module is used to determine the liquid level assessment result of the cold box of the hydrogen liquefaction device based on the defrosting frequency. The liquid level assessment result is used to characterize the pattern and corresponding rate of change of the existing refrigerant liquid level in the cold box under the defrosting frequency. The preset cold release convection heat transfer coefficient relationship is expressed as follows: In the formula: Indicates the target heat transfer coefficient for heat release and convection; This represents the heat flux, in W / m², during the evaporation and cooling process of the cold source, when the frost produced in contact with the cold plate in the cold box undergoes heat exchange with the cold plate. 2 ; Indicates the temperature of the incoming airflow, in K; Indicates the temperature of the frost layer in contact with the test contact cold plate, in K; The velocity of the incoming airflow is expressed in m / s. Indicates the absolute humidity of the incoming air, kg / kg a ; This indicates the humidity of the frost layer in contact with the cold plate being tested, in kg / kg. a ; The cold release kinetic factor represents the cold temperature range and is a dimensionless number used to characterize the degree of frost formation on the surface of the cold plate in contact with the cold box as a function of temperature difference.

8. A computer device, comprising: include: A memory and a processor are communicatively connected, the memory storing computer instructions, and the processor executing the computer instructions to perform the liquid level assessment method for a cold box in a hydrogen liquefaction device as described in any one of claims 1 to 6.

9. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores computer instructions for causing the computer to execute the liquid level assessment method for the cold box of the hydrogen liquefaction device according to any one of claims 1 to 6.

10. A computer program product, characterised in that, Includes computer instructions for causing a computer to execute the liquid level assessment method for a cold box in a hydrogen liquefaction apparatus as described in any one of claims 1 to 6.

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