Method and system for testing flow and heat transfer performance of integrated heat exchanger

Abstract

The present application relates to the technical field of electronic special gas, hydrogen energy and low temperature refrigeration, and particularly relates to a test method and system for flow and heat transfer performance of an integrated heat exchanger; the present application first determines the hydrogen flow, inlet and outlet temperatures, pressure, and para-hydrogen concentration in the integrated heat exchanger, and determines the flow, inlet and outlet temperatures, and pressure of other channels, so as to obtain the heat exchange capacity of the measured heat exchanger; then, according to the heat exchange capacity of the measured heat exchanger and the structural size of the measured heat exchanger, the relationship among the Colburn heat transfer factor J, the Fanning friction factor f, and the empty tower Re in the integrated channel is obtained, so as to obtain the heat transfer characteristics and flow characteristics of the integrated channel of the measured heat exchanger.

Description

Technical Field

[0001] This invention relates to the fields of electronic specialty gases, hydrogen energy, and cryogenic refrigeration technology, and particularly to a method and system for testing the flow and heat transfer performance of an integrated heat exchanger. Background Technology

[0002] Liquid hydrogen is widely used in aerospace, electronic specialty gases, fine chemicals and hydrogen energy. Hydrogen exists in two forms: orthohydrogen and parahydrogen. The equilibrium content of parahydrogen varies at different temperatures. At room temperature, the equilibrium concentration of parahydrogen is 25%, while at the liquid hydrogen temperature (20K), the equilibrium concentration of parahydrogen reaches 99.8%. If the liquefaction process only involves cooling without the conversion of orthohydrogen to parahydrogen, 18% of the liquid hydrogen produced will evaporate on the first day. Therefore, in the hydrogen liquefaction process, the conversion of orthohydrogen to parahydrogen must be carried out simultaneously with cooling.

[0003] Early hydrogen liquefaction plants separated the heat exchanger from the ortho- and para-hydrogen converter, such as the Ingolstadt liquid hydrogen plant in Germany. However, more recently constructed liquid hydrogen plants use integrated heat exchangers for both heat exchange and ortho- and para-hydrogen conversion, such as the Ruina liquid hydrogen plant in Germany. The conversion from ortho- and para-hydrogen is exothermic, so performing this conversion during liquefaction cooling increases energy consumption. The heat of conversion increases as temperature decreases, and the exergy required for the same amount of heat increases as temperature decreases. Since cooling is exothermic, adiabatic conversion raises the hydrogen temperature. Therefore, the conversion from ortho- and para-hydrogen during liquefaction should ideally occur at higher temperatures. However, due to the equilibrium concentration of para-hydrogen at various temperatures, the conversion from ortho- and para-hydrogen during liquefaction is difficult to complete at room temperature or before the temperature drops to liquid nitrogen temperature. Therefore, using an integrated heat exchanger that combines cooling and conversion is more energy-efficient than using a conventional heat exchanger with adiabatic and isothermal or para-hydrogen converter.

[0004] Because a catalyst is inserted into the integrated channel of the integrated heat exchanger, the flow and heat transfer characteristics of the integrated channel change. J(Re,Pr) and f(Re,Pr) of ordinary empty tower channels are no longer applicable. After the addition of the catalyst, the hydrogen gas in the integrated channel changes from flowing inside the tube to flowing around a porous medium in a confined space. Current theoretical models for studying gas flowing around a porous medium in a confined space are based on the flow mechanism and use the characteristic dimensions of the porous medium itself as the characteristic dimensions, and the theoretical models themselves have certain errors. However, heat exchanger design needs to use the characteristic dimensions of the channel as the characteristic dimensions. Therefore, it is necessary to experimentally determine the flow and heat transfer characteristics of hydrogen gas in the integrated heat exchange channel. Summary of the Invention

[0005] The main technical problem solved by this invention is to provide a testing method for the flow and heat transfer performance of an integrated heat exchanger. This method measures the hydrogen flow rate, inlet and outlet temperatures, pressures, and secondary hydrogen concentration in the integrated heat exchanger, as well as the flow rate, inlet and outlet temperatures, and pressures of other channels, thereby obtaining the heat transfer capacity of the heat exchanger under test. Based on the heat transfer capacity and structural dimensions of the heat exchanger under test, the relationship between the Kolper heat transfer factor J, the Fanning friction factor f, and the empty tower Re within the integrated channel is derived, thus obtaining the heat transfer and flow characteristics of the integrated channel of the heat exchanger under test. The invention also provides a testing system for the flow and heat transfer performance of the integrated heat exchanger.

[0006] To solve the above-mentioned technical problems, one technical solution adopted by the present invention is: providing a method for testing the flow and heat transfer performance of an integrated heat exchanger, comprising the following steps:

[0007] Step S1: After depressurizing the high-purity hydrogen in the high-pressure cylinder, it is introduced into the hydrogen compression module for compression. At the same time, the hydrogen flow rate, inlet and outlet temperature, pressure and secondary hydrogen concentration in the integrated channel are measured.

[0008] Step S2: Then, the compressed hydrogen gas is passed into the hydrogen purification module for purification.

[0009] Step S3: Pass purified hydrogen into the test module and measure the flow rate, inlet and outlet temperature and pressure of other channels to obtain measurement data. Based on the measurement data, the heat exchange capacity of the heat exchanger under test can be determined.

[0010] Step S4: Based on the heat exchanger's heat transfer capacity and structural dimensions, the relationship between the Körber heat transfer factor J, the Fanning friction factor f, and the empty tower Re within the integrated channel is obtained, thereby acquiring the heat transfer and flow characteristics of the integrated channel of the heat exchanger under test.

[0011] As an improvement of the present invention, in step S3, the heat exchanger under test is a two-stream heat exchanger, and the two channels are a hydrogen channel and a low-temperature gas channel, respectively. The surface heat transfer coefficient between the low-temperature gas channel and the partition wall is greater than the surface heat transfer coefficient between the hydrogen channel and the partition wall, thus constructing a low-temperature isobaric boundary.

[0012] As a further improvement of the present invention, in step S2, the hydrogen is purified to make the hydrogen purity not less than 7N ultrapure hydrogen.

[0013] As a further improvement of the present invention, in step S3, the purified hydrogen is divided into two parts: a main path and a bypass path. The ultrapure hydrogen in the main path enters the pre-cooling heat exchanger and is cooled by the circulating reflux hydrogen. The ultrapure hydrogen in the bypass path bypasses the pre-cooling heat exchanger and, without cooling, directly mixes and dilutes with the ultrapure hydrogen in the main path at the high-pressure outlet of the pre-cooling heat exchanger, thereby obtaining different inlet temperatures of the heat exchangers under test. The mixed ultrapure hydrogen passes through the heat exchanger under test, realizing the integrated conversion of positive hydrogen to secondary hydrogen and cooling.

[0014] A testing system for the flow and heat transfer performance of an integrated heat exchanger, employing any of the testing methods described above, comprising:

[0015] Hydrogen compression module, used to compress hydrogen;

[0016] Hydrogen purification module, used to purify hydrogen;

[0017] The test module is used to pre-cool hydrogen gas and then introduce it into the heat exchanger under test to obtain the performance parameter data of the heat exchanger under test.

[0018] Other modules.

[0019] As an improvement of the present invention, the hydrogen compression module includes:

[0020] A compressor is used to compress hydrogen gas, thereby creating a pressure differential to complete the cycle;

[0021] A water chiller is used to cool compressed hydrogen gas to room temperature.

[0022] A dryer is used to dry compressed hydrogen gas.

[0023] Oil filter, used to filter oil vapors inside hydrogen gas.

[0024] As a further improvement of the present invention, the hydrogen purification module includes:

[0025] A denitrifier is used to remove nitrogen from hydrogen gas.

[0026] A deoxygenator is used to remove oxygen from hydrogen gas.

[0027] As a further improvement of the present invention, the test module includes:

[0028] Low-temperature vacuum cold box, used for multi-layer vacuum insulation;

[0029] Precooling heat exchanger;

[0030] The heat exchanger under test;

[0031] A flow meter is used to measure the flow rate of each stream within a heat exchanger being tested.

[0032] Temperature sensors are used to measure the inlet and outlet temperatures of each stream within the heat exchanger under test.

[0033] Pressure sensors are used to measure the inlet and outlet pressures of each stream within the heat exchanger under test.

[0034] A gas chromatograph is used to determine the concentration of secondary hydrogen at the inlet and outlet of the hydrogen channel of the heat exchanger under test.

[0035] As a further improvement of the present invention, the precooling heat exchanger includes:

[0036] Hydrogen precooling channel, used for hydrogen precooling;

[0037] Hydrogen rewarming channel, used for hydrogen rewarming;

[0038] The hydrogen reheating channel is filled with a catalyst for the conversion of secondary hydrogen to positive hydrogen during the reheating process, thereby restoring the secondary hydrogen concentration to 25%.

[0039] As a further improvement of the present invention, the other modules include:

[0040] An ambient temperature reheater is used for reheating refluxed hydrogen gas.

[0041] A regulating valve is used to regulate flow and reduce pressure.

[0042] High-pressure gas cylinder assembly, used for gas replenishment.

[0043] The beneficial effects of this invention are as follows: Compared with the prior art, this invention first measures the hydrogen flow rate, inlet and outlet temperatures, pressures, and secondary hydrogen concentration in the integrated heat exchanger, and measures the flow rate, inlet and outlet temperatures, and pressures of other channels, thereby obtaining the heat transfer capacity of the heat exchanger under test. Then, based on the heat transfer capacity and structural dimensions of the heat exchanger under test, the relationship between the Kolper heat transfer factor J, the Fanning friction factor f, and the empty tower Re in the integrated channel is obtained, thereby obtaining the heat transfer characteristics and flow characteristics of the integrated channel of the heat exchanger under test. Attached Figure Description

[0044] Figure 1 This is a schematic diagram of the test platform of the present invention;

[0045] Figure 2 This is a schematic diagram illustrating the principle of this invention for testing the relationship between the Kolber heat transfer factor J, the Fanning friction factor f, and the empty tower Re.

[0046] Attached label: 1-Compressor, 2-Water chiller, 3-Dryer, 4-Oil filter, 5-Denitrifier, 6-Deaerator, 7-Low-temperature vacuum chamber, 8-Pre-cooling heat exchanger, 9-Heat exchanger under test, 10-Flow meter, 11-Ambient temperature recovery device, 12-Pressure reducing valve, 13-High-pressure gas cylinder group, T-Thermometer, p-Pressure sensor, pH-Gas chromatograph, I-Hydrogen compression module, II-Hydrogen purification module, III-Testing module, IV-Other modules. Detailed Implementation

[0047] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0048] Please refer to Figures 1 to 2 The method for testing the flow and heat transfer performance of the integrated heat exchanger of the present invention includes the following steps:

[0049] Step S1: After depressurizing the high-purity hydrogen in the high-pressure cylinder, it is introduced into the hydrogen compression module for compression. At the same time, the hydrogen flow rate, inlet and outlet temperature, pressure and secondary hydrogen concentration in the integrated channel are measured.

[0050] Step S2: Then, the compressed hydrogen gas is passed into the hydrogen purification module for purification.

[0051] Step S3: Pass purified hydrogen into the test module and measure the flow rate, inlet and outlet temperature and pressure of other channels to obtain measurement data. Based on the measurement data, the heat exchange capacity of the heat exchanger under test can be determined.

[0052] Step S4: Based on the heat exchanger's heat transfer capacity and structural dimensions, the relationship between the Körber heat transfer factor J, the Fanning friction factor f, and the empty tower Re within the integrated channel is obtained, thereby acquiring the heat transfer and flow characteristics of the integrated channel of the heat exchanger under test.

[0053] In steps S3 and S4, the heat exchanger under test is a liquid nitrogen siphon type two-stream heat exchanger, one stream is hydrogen and the other stream is liquid nitrogen, and the hydrogen channel is filled with an iron-based ortho-parahydrogen conversion catalyst.

[0054] In this invention, the hydrogen flow rate q in the integrated channel of the integrated heat exchanger is first measured. m1 Inlet and outlet temperatures T 1,in With T 2out Pressure p 1in With p 1out and secondary hydrogen concentration pH in and pH out Then, the flow rate, inlet and outlet temperatures, and pressures of other channels are measured to obtain measurement data. Based on the measurement data, the heat transfer capacity φ of the heat exchanger under test is obtained. Based on the heat transfer capacity and structural dimensions of the heat exchanger under test, the relationship between the Körber heat transfer factor J, the Fanning friction factor f, and the empty tower Re in the integrated channel is obtained.

[0055] This invention requires constructing a low-temperature environment and isothermal boundary conditions for the hydrogen channel (integrated channel). Besides measuring the flow rate, inlet and outlet temperatures, and pressures of each stream, it also requires determining the secondary hydrogen concentration at the inlet and outlet of the integrated channel. In step S3, the heat exchanger under test is a two-stream heat exchanger, with the two channels being a hydrogen channel and a low-temperature gas channel. The surface heat transfer coefficient between the low-temperature gas channel and the partition wall is greater than that between the hydrogen channel and the partition wall, thus constructing a low-temperature isothermal boundary. Specifically, the heat exchanger under test is a two-stream heat exchanger, one stream being hydrogen, and the other being a low-temperature liquid such as LNG or liquid nitrogen, or a low-temperature gas such as low-temperature helium. Figure 1 As shown; the hydrogen channel is filled with iron-based or other positive and negative hydrogen conversion catalysts to achieve the conversion of positive hydrogen to negative hydrogen while the hydrogen is cooling; the other stream, if it is a cryogenic liquid such as LNG or liquid nitrogen, uses a siphon heat exchanger; if it is a cryogenic gas such as cryogenic helium, the cryogenic helium flow rate is much greater than the hydrogen flow rate, q m2 >>q m1 This ensures that the surface heat transfer coefficient between the stream and the partition wall is much greater than that on the hydrogen side, thus creating a low-temperature isobaric boundary condition. Such a boundary condition makes the heat transfer coefficient of the heat exchanger approximately equal to the surface heat transfer coefficient of the integrated channel, U≈U 氢通道 .

[0056] When calculating the heat exchanger's heat transfer capacity, it is necessary to consider not only the enthalpy change caused by the decrease in hydrogen temperature, but also the heat release from the conversion of orthohydrogen to secondary hydrogen, φ=φ 降温 +φ 转化 In the heat exchanger under test, the conversion of orthohydrogen to parahydrogen and the cooling of hydrogen occur simultaneously; therefore, a method is adopted to convert φ 转化 The method for converting to equivalent specific heat is shown in the following formula:

[0057]

[0058]

[0059] Among them, c p,当量 =c p，降温 +c p，转化 , where c p，降温 =c p，正仲氢混合物，T =[c p,正氢 (1-α 仲氢,T )+c p,仲氢 α 仲氢,T ], α 仲氢,T c represents the actual content of secondary hydrogen at various temperatures. p，转化 =η{c p，平衡氢 -[c p,正氢 (1-α 仲氢0,T )+c p,仲氢 α 仲氢0,T ]}, α 仲氢0,T This represents the equilibrium content of secondary hydrogen at various temperatures. Among them,

[0060]

[0061] It should be noted that, because α 仲氢,Tin <α 仲氢0,Tin η may be greater than 1, meaning that η is not the conversion rate.

[0062] Moreover, the measurement of secondary hydrogen concentration is based on the difference in thermal conductivity between normal hydrogen and secondary hydrogen, and methods such as gas chromatography are used. Since impurities such as nitrogen and oxygen in hydrogen will cause a large deviation in the thermal conductivity measurement, ultrapure hydrogen with a volume purity of not less than 7N must be used for measurement.

[0063] In step S3, the purified hydrogen is divided into a main path and a bypass path. The ultrapure hydrogen in the main path enters the pre-cooling heat exchanger and is cooled by the circulating reflux hydrogen. The ultrapure hydrogen in the bypass path bypasses the pre-cooling heat exchanger and is directly mixed with the ultrapure hydrogen in the main path at the high-pressure outlet of the pre-cooling heat exchanger without cooling, thereby obtaining different inlet temperatures of the heat exchangers under test. The mixed ultrapure hydrogen passes through the heat exchanger under test, realizing the integrated conversion of positive hydrogen to secondary hydrogen and cooling.

[0064] The workflow of this invention is as follows: High-pressure high-purity hydrogen gas from a high-purity hydrogen cylinder (pressure 15-25 MPa) is reduced to 2-3 MPa by a pressure reducing valve and then combined with hydrogen gas from the compressor outlet. The combined hydrogen gas then passes through a dryer, oil filter, and other equipment before entering a purifier for denitrification and deoxygenation to ensure a purity of not less than 7N. The purified hydrogen gas is then divided into two streams entering the cold box: the main stream (flow rate approximately 90-99%) is cooled to approximately 80K by a pre-cooling heat exchanger, while the bypass stream (flow rate approximately 1-10%) does not undergo pre-cooling heat exchange. In this device, two streams of hydrogen gas converge at the outlet of the pre-cooling heat exchanger for temperature exchange. After temperature exchange, the hydrogen temperature is approximately 80–110 K. The combined and temperature-exchanged hydrogen gas then enters the heat exchanger under test for cooling. In this example, the heat exchanger under test is a liquid nitrogen siphon heat exchanger, thus the hydrogen temperature drops to approximately 78 K after passing through it. The heat exchanger under test is a two-stream heat exchanger integrating ortho- and para-hydrogen conversion and heat exchange. One stream is hydrogen gas, which needs to undergo ortho- and para-hydrogen conversion simultaneously with cooling to reduce the para-hydrogen concentration from the room temperature equilibrium concentration of 25%. The hydrogen concentration rises to approximately 49% at the equilibrium temperature of liquid nitrogen, with another stream being liquid nitrogen. The cooled hydrogen gas flows back to the reflux channel of the pre-cooling heat exchanger, while the nitrogen gas formed after the liquid nitrogen evaporates enters the nitrogen channel of the pre-cooling heat exchanger. Because the secondary hydrogen concentration rises from 25% to approximately 49% within the tested heat exchanger, if the secondary hydrogen concentration is not restored, after a certain period of cycling, the secondary hydrogen concentration in the entire test system will be 49%, and the tested heat exchanger will no longer be an integrated heat exchanger. This will severely affect the heat transfer characteristics of the integrated heat exchanger. The accuracy of the measurement renders the test meaningless. Therefore, in addition to rewarming, the reflux hydrogen in the precooling heat exchanger must also have its secondary hydrogen concentration restored from approximately 49% to 25%. The restoration of secondary hydrogen to positive hydrogen is an endothermic process with a self-cooling effect. As a result, the reflux hydrogen is not sufficiently rewarmed in the precooling heat exchanger. Therefore, after flowing out of the precooling heat exchanger, the reflux hydrogen needs to be rewarmed through an ambient air vaporizer. After being rewarmed, the hydrogen is depressurized to atmospheric pressure and then enters the hydrogen compressor for pressurization. The pressurized hydrogen is then combined with new hydrogen from the high-pressure cylinder to complete the cycle.

[0065] Specifically, the high-purity hydrogen source is typically high-pressure high-purity hydrogen with a cylinder pressure of 15 MPa or a torpedo tank pressure of 20–25 MPa. This pressure is higher than the circulating high pressure (2–3 MPa) of this testing system. Therefore, the new hydrogen from the high-purity hydrogen source is reduced in pressure by a pressure reducing valve to match the circulating high pressure (2–3 MPa) of this testing system. It is then mixed with the circulating hydrogen that has been compressed by a compressor and then passed through a dryer and oil filter. After passing through a denitrification and purification unit to become ultra-pure hydrogen with a purity of not less than 7N, it is divided into two paths: the main ultra-pure hydrogen enters the pre-cooling heat exchanger and is cooled by the circulating return hydrogen; the bypass ultra-pure hydrogen bypasses the pre-cooling heat exchanger and, without cooling, mixes directly with the main ultra-pure hydrogen at the high-pressure outlet of the pre-cooling heat exchanger to achieve temperature matching, thereby obtaining… The test involves different inlet temperatures of the heat exchanger under test. The mixed ultrapure hydrogen passes through the heat exchanger under test, achieving integrated conversion of positive hydrogen to secondary hydrogen and cooling. To ensure the accuracy of the test, the heat exchanger under test adopts a two-stream heat exchanger, one for the ultrapure hydrogen to be cooled and the other for cooling the ultrapure hydrogen, without an ultrapure hydrogen return channel. The heat exchanger under test is usually a liquid nitrogen siphon heat exchanger, or a hydrogen-helium heat exchanger with a cold helium mass flow rate at least 40 times greater than the ultrapure hydrogen mass flow rate, to achieve near-isothermal boundary conditions. When the ultrapure hydrogen mass flow rate, cold helium mass flow rate, and cold helium inlet temperature remain constant (or the liquid nitrogen pressure used in the liquid nitrogen siphon heat exchanger remains constant), different ultrapure hydrogen inlet temperatures correspond to different empty tower Reynolds numbers Re.

[0066] By measuring the mass flow rate, inlet and outlet temperatures, pressure, and secondary hydrogen content of ultrapure hydrogen in the tested heat exchanger, the heat transfer capacity and pressure loss of the integrated channel can be obtained. Then, by measuring the mass flow rate, inlet and outlet temperatures, and pressure of the cooling flow, the logarithmic mean temperature difference of the heat exchanger can be obtained. The heat transfer capacity and empty tower Re of the heat exchanger can then be verified. Based on the heat transfer capacity, logarithmic mean temperature difference, and structural dimensions of the tested heat exchanger, the heat transfer coefficient, and thus the total thermal resistance, can be obtained. The heat transfer process of the heat exchanger is heat transfer from the hot fluid surface to the metal wall, and then to the cold fluid surface. This can be considered as the thermal resistance of the hot fluid surface, the thermal resistance of the metal wall, and the thermal resistance of the cold fluid surface connected in series. The heat exchanger under test is usually a liquid nitrogen siphon heat exchanger, or a hydrogen-helium heat exchanger in which the mass flow rate of cold helium is at least 20 times greater than that of ultrapure hydrogen. Therefore, the surface heat transfer resistance of the hydrogen side (the surface heat transfer resistance of the hot fluid) is much greater than the surface heat transfer resistance of the liquid nitrogen evaporation side or the low-temperature helium side (the surface heat transfer resistance of the cold fluid). The heat exchanger under test is made of metal (usually all-aluminum plate and fin), and the metal walls between the flow layers are extremely thin. The fluid velocity within the heat exchanger channels is very low, typically less than 10 m / s or even less than 5 m / s. Therefore, the thermal resistance of the metal walls is much lower than the surface thermal resistance of the hot and cold fluids. Thus, the total thermal resistance of the heat exchanger under test is approximately equal to the surface thermal resistance of the hydrogen side, meaning the total heat transfer coefficient of the heat exchanger is approximately equal to the surface heat transfer coefficient of the hydrogen side. After obtaining the surface heat transfer coefficient of the hydrogen side, and combining it with the structural dimensions of the heat exchanger under test and the physical properties of hydrogen, the Nusselt number and Kolper heat transfer factor J on the hydrogen side can be obtained. By varying the mass flow rate and inlet temperature on the hydrogen side of the heat exchanger under test, different empty tower Re values ​​and their corresponding J factors are obtained. The heat transfer characteristics of the integrated heat exchange channel under test are then fitted using these J factors and empty tower Re values. The flow characteristics are obtained by measuring the inlet and outlet pressures on the hydrogen side, calculating the inlet and outlet pressure drops, and combining the hydrogen flow rate and the structural dimensions of the heat exchanger under test to obtain the Fanning friction factor f and Re values ​​of the integrated heat exchange channel under test. By varying the mass flow rate and inlet temperature on the hydrogen side of the heat exchanger under test, different empty tower Re values ​​and their corresponding f factors are obtained. The flow characteristics of the integrated heat exchange channel under test are then fitted using these f factors and empty tower Re values.

[0067] The tested heat exchanger is an integrated heat exchanger. Its hydrogen inlet concentration is 25%, and its outlet concentration is close to the equilibrium concentration of 49% at 78K. If the secondary hydrogen concentration is not reduced back to 25% during reheating without a catalyst, after several cycles, the secondary hydrogen content of all hydrogen will become 49%, and the tested heat exchanger will no longer have an integrated function. Therefore, catalytic conversion must be performed during reheating to convert secondary hydrogen into positive hydrogen. Thus, the hydrogen cooled by the tested heat exchanger and after the conversion between secondary and positive hydrogen is... When the hydrogen is returned to the precooling heat exchanger for rewarming, the secondary hydrogen content needs to be reduced from about 49% back to 25%. This is achieved by inserting a positive-to-secondary hydrogen conversion catalyst into the return channel of the precooling heat exchanger. The process of converting secondary hydrogen to positive hydrogen is an endothermic and self-cooling process. Therefore, after the hydrogen is cooled to liquid nitrogen temperature in the heat exchanger being tested, it will experience insufficient rewarming in the precooling heat exchanger (returning to about -50°C). Therefore, after the reflux hydrogen is rewarmed in the precooling heat exchanger, it must pass through an ambient temperature rewarmer for further rewarming.

[0068] The integrated heat exchanger of the present invention has a test system for flow and heat transfer performance, which employs the test method described in any of the above-mentioned methods. The test system includes a hydrogen compression module, a hydrogen purification module, a test module, and other modules.

[0069] The hydrogen compression module includes:

[0070] Compressor 1 is used to compress hydrogen gas, thereby creating a pressure differential to complete the cycle;

[0071] Water chiller 2 is used to cool the compressed hydrogen gas to room temperature;

[0072] Dryer 3 is used to dry the compressed hydrogen gas;

[0073] Oil filter 4 is used to filter oil and gas inside hydrogen.

[0074] The hydrogen purification module includes:

[0075] Denitrifier 5 is used for denitrification of hydrogen gas;

[0076] Deoxygenator 6 is used to remove oxygen from hydrogen gas.

[0077] The test module includes:

[0078] Low-temperature vacuum cold box 7, used for multi-layer vacuum insulation;

[0079] Precooling heat exchanger 8 includes:

[0080] Hydrogen precooling channel, used for hydrogen precooling;

[0081] Hydrogen rewarming channel, used for hydrogen rewarming;

[0082] The hydrogen reheating channel is filled with a catalyst for the conversion of secondary hydrogen to positive hydrogen during the reheating process, thereby restoring the secondary hydrogen concentration to 25%.

[0083] The heat exchanger under test, 9, is a liquid nitrogen siphon integrated two-stream heat exchanger. One stream is hydrogen gas and the other stream is liquid nitrogen. The heat exchanger is completely immersed in a liquid nitrogen cold box, which is built into a low-temperature vacuum cold box. The liquid nitrogen level is higher than the upper surface of the heat exchanger and the liquid level is kept in balance by continuously replenishing liquid nitrogen.

[0084] Flow meter 10 is used to measure the flow rate of each stream in the heat exchanger under test;

[0085] Temperature sensor T is used to measure the inlet and outlet temperatures of each stream within the heat exchanger under test.

[0086] Pressure sensor p is used to measure the inlet and outlet pressures of each stream within the heat exchanger under test.

[0087] The pH value of the gas chromatograph is used to determine the concentration of secondary hydrogen at the inlet and outlet of the hydrogen channel of the heat exchanger under test.

[0088] In addition, other modules include:

[0089] The ambient temperature reheater 11 is used for reheating refluxed hydrogen gas.

[0090] Regulating valve 12 is used to regulate flow and reduce pressure;

[0091] High-pressure gas cylinder group 13 is used for gas replenishment.

[0092] In this invention, a liquid nitrogen siphon heat exchanger is used to address the isothermal boundary condition problem; gas chromatography is used to determine the thermal conductivity to address the problem of secondary hydrogen concentration measurement; and the equivalent specific heat method is used to calculate the continuous conversion heat of positive and secondary hydrogen. This invention constructs isothermal boundary conditions, measures parameters such as the flow rate, inlet and outlet temperatures, and inlet and outlet secondary hydrogen concentrations of the hydrogen channel, measures the heat transfer capacity of the tested heat exchanger, and finally calculates the relationship between the J and f factors and the empty tower Re in the integrated channel of the tested heat exchanger, thereby obtaining the heat transfer and flow characteristics of the integrated channel of the tested heat exchanger.

[0093] The above description is merely an embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made based on the content of the present invention specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A method for testing the flow and heat transfer performance of an integrated heat exchanger, characterized in that, Includes the following steps: Step S1: After depressurizing the high-purity hydrogen in the high-pressure cylinder, it is introduced into the hydrogen compression module for compression. At the same time, the hydrogen flow rate, inlet and outlet temperature, pressure and secondary hydrogen concentration in the integrated channel are measured. Step S2: Then, the compressed hydrogen gas is passed into the hydrogen purification module for purification. Step S3: Pass purified hydrogen into the test module and measure its flow rate, inlet and outlet temperatures and pressures to obtain measurement data. Based on the measurement data, determine the heat exchange capacity of the heat exchanger under test. Step S4: Based on the heat transfer capacity and structural dimensions of the heat exchanger under test, the relationship between the Körber heat transfer factor J, the Fanning friction factor f, and the empty tower Re within the integrated channel is obtained, thereby obtaining the heat transfer characteristics and flow characteristics of the integrated channel of the heat exchanger under test.

2. The method for testing the flow and heat transfer performance of the integrated heat exchanger according to claim 1, characterized in that, In step S3, the heat exchanger under test is a two-stream heat exchanger, with the two channels being a hydrogen channel and a cryogenic gas channel, respectively. The surface heat transfer coefficient between the cryogenic gas channel and the partition wall is greater than that between the hydrogen channel and the partition wall, thus constructing a cryogenic isobaric boundary.

3. The method for testing the flow and heat transfer performance of the integrated heat exchanger according to claim 2, characterized in that, In step S2, the hydrogen is purified to make it ultrapure hydrogen with a purity of not less than 7N.

4. The method for testing the flow and heat transfer performance of the integrated heat exchanger according to claim 3, characterized in that, In step S3, the purified hydrogen is divided into a main path and a bypass path. The ultrapure hydrogen in the main path enters the pre-cooling heat exchanger and is cooled by the circulating reflux hydrogen. The ultrapure hydrogen in the bypass path bypasses the pre-cooling heat exchanger and is directly mixed with the ultrapure hydrogen in the main path at the high-pressure outlet of the pre-cooling heat exchanger without cooling, thereby obtaining different inlet temperatures of the heat exchangers under test. The mixed ultrapure hydrogen passes through the heat exchanger under test, realizing the integrated conversion of positive hydrogen to secondary hydrogen and cooling.

5. A testing system for the flow and heat transfer performance of an integrated heat exchanger, characterized in that, The testing system, employing the testing method as described in claim 4, comprises: Hydrogen compression module, used to compress hydrogen; Hydrogen purification module, used to purify hydrogen; The test module is used to pre-cool hydrogen gas and then introduce it into the heat exchanger under test to obtain the performance parameter data of the heat exchanger under test. Other modules include: An ambient temperature reheater is used for reheating refluxed hydrogen gas. A regulating valve is used to regulate flow and reduce pressure. High-pressure gas cylinder assembly, used for gas replenishment.

6. The testing system for the flow and heat transfer performance of the integrated heat exchanger according to claim 5, characterized in that, The hydrogen compression module includes: A compressor is used to compress hydrogen gas, thereby creating a pressure differential to complete the cycle; A water chiller is used to cool compressed hydrogen gas to room temperature. A dryer is used to dry compressed hydrogen gas. Oil filter, used to filter oil vapors inside hydrogen gas.

7. The testing system for the flow and heat transfer performance of the integrated heat exchanger according to claim 5, characterized in that, The hydrogen purification module includes: A denitrifier is used to remove nitrogen from hydrogen gas. A deoxygenator is used to remove oxygen from hydrogen gas.

8. The testing system for the flow and heat transfer performance of the integrated heat exchanger according to claim 5, characterized in that, The testing module includes: Low-temperature vacuum cold box, used for multi-layer vacuum insulation; Precooling heat exchanger; The heat exchanger under test; A flow meter is used to measure the flow rate of each stream within a heat exchanger being tested. Temperature sensors are used to measure the inlet and outlet temperatures of each stream within the heat exchanger under test. Pressure sensors are used to measure the inlet and outlet pressures of each stream within the heat exchanger under test. A gas chromatograph is used to determine the concentration of secondary hydrogen at the inlet and outlet of the hydrogen channel of the heat exchanger under test.

9. The testing system for the flow and heat transfer performance of the integrated heat exchanger according to claim 8, characterized in that, The precooling heat exchanger includes: Hydrogen precooling channel, used for hydrogen precooling; Hydrogen rewarming channel, used for hydrogen rewarming; The hydrogen reheating channel is filled with a catalyst for the conversion of secondary hydrogen to positive hydrogen during the reheating process, thereby restoring the secondary hydrogen concentration to 25%.

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