Metal hydride hydrogen storage system equipped with composite heat exchanger and control method

Abstract

The present invention relates to a metal hydride hydrogen storage system equipped with a composite heat exchanger, comprising a hydrogen quantity prediction system, a composite heat exchanger, and a metal hydride storage tank. The composite heat exchanger comprises an external heat exchanger and an internal heat exchanger. The external heat exchanger comprises a phase change material and metal foam, and the phase change material and metal foam are arranged in the form of a jacket on the outside of the metal hydride storage tank. The internal heat exchanger comprises a tubular heat exchanger and metal fins built into the metal hydride hydrogen storage tank. The hydrogen quantity prediction system is used to predict the hydrogen demand of hydrogen-using equipment under different operating conditions. In the present invention, when the hydrogen demand is small or during a cold start, the metal hydride hydrogen storage system is heated solely by the external heat exchanger to meet the heat required during the metal hydride dehydrogenation process. When the hydrogen demand is large, the metal hydride hydrogen storage system is heated jointly by the external heat exchanger and the internal heat exchanger to meet the heat required during the metal hydride dehydrogenation process.

Description

Technical Field

[0001] The present invention relates to the field of energy, and more particularly to a metal hydride hydrogen storage system equipped with a composite heat exchanger and a control method thereof. Background Art

[0002] A metal hydride hydrogen storage system uses a hydrogen storage material as a hydrogen storage medium to provide a hydrogen supply. It functions as both a reactor and a heat exchanger. The hydrogen storage material releases heat when absorbing hydrogen and must obtain heat externally during dehydrogenation. The resulting thermal effects can cause the system temperature to rise or fall sharply, hindering the rapid absorption and dehydrogenation process. The significant thermal effects during the absorption and dehydrogenation process of metal hydrides severely impact their hydrogen storage performance and reaction rates.

[0003] The integrated design and performance control of metal hydride hydrogen storage systems are crucial for achieving safe and efficient hydrogen storage and are a key research direction for the future. The integrated design of metal hydride hydrogen storage systems is primarily related to the tank structure and heat exchanger layout, while performance control is closely linked to the reaction rate. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a metal hydride hydrogen storage system equipped with a composite heat exchanger and a control method. Through numerical simulation and BP neural network data analysis, the corresponding relationship between the hydrogen supply rate of the metal hydride device equipped with a composite heat exchanger and different operating conditions is established, the hydrogen supply rate can be predicted, and the hydrogen demand under different working conditions can be met.

[0005] The technical solution adopted by the present invention to solve its technical problems is: constructing a metal hydride hydrogen storage system equipped with a composite heat exchanger, including a hydrogen quantity prediction system, a composite heat exchanger and a metal hydride storage tank, the composite heat exchanger including an external heat exchanger and an internal heat exchanger, the external heat exchanger including a phase change material and metal foam, the phase change material and metal foam are arranged in the form of a jacket on the outside of the metal hydride storage tank, the internal heat exchanger includes a tubular heat exchanger and metal fins built into the metal hydride hydrogen storage tank, the hydrogen quantity prediction system is used to predict the hydrogen demand of hydrogen-using equipment under different operating conditions.

[0006] According to the above solution, the hydrogen quantity prediction system includes a controller based on BP neural network.

[0007] According to the above scheme, the metal foam is metal nickel with high permeability, high specific surface area and capillary force; the phase change material is commercial paraffin RT35; a coolant is set in the tubular heat exchanger, and the coolant is water; the metal fins are metal sheets with a smooth surface and a large specific surface area.

[0008] The present invention also provides a control method for a metal hydride hydrogen storage system equipped with a composite heat exchanger, comprising the following steps:

[0009] S1. Establish a numerical model of metal hydride hydrogen storage system;

[0010] S2. Compare the simulated values ​​of the monitoring point temperature in the metal hydride bed and the system hydrogen storage capacity with the experimental data to verify the validity of the numerical model;

[0011] S3. Based on the verified metal hydride hydrogen storage model, a metal hydride hydrogen storage model equipped with a composite heat exchanger is constructed;

[0012] S4. Select operating parameters, conduct parameter research, and analyze the evolution of the hydrogen supply rate of the metal hydride hydrogen storage system equipped with a composite heat exchanger under different operating parameter conditions;

[0013] S5. Based on the results of parameter research, a data set is constructed; the data set is divided into a training set, a test set, and a validation set, and the accuracy of the data set is verified while training the BP neural network model; a BP neural network model is constructed, with the above-mentioned operating conditions as input and the hydrogen supply rate as output, and the BP neural network is trained using the existing data set to establish the corresponding relationship between different operating conditions and the hydrogen supply rate, thereby realizing the prediction of the hydrogen supply rate of the metal hydride hydrogen storage system.

[0014] According to the above scheme, in step S1, the numerical model is established based on the multi-physics field simulation software COMSOL for the size and experimental conditions of the metal hydride hydrogen storage system, the physical properties of the built-in metal hydride, the physical properties of hydrogen, as well as the law of conservation of mass, the law of conservation of momentum, the law of conservation of energy, the metal hydride reaction kinetics equation, the equilibrium pressure equation and the ideal gas state equation.

[0015] According to the above solution, in step S3, in the metal hydride hydrogen storage model, a spiral tube heat exchanger is added inside the metal hydride storage tank, and a phase change material heat exchanger is added outside the metal hydride storage tank.

[0016] According to the above solution, in step S4, the operating parameters selected include heat transfer coefficient, circulating water temperature, and tank internal pressure.

[0017] According to the above scheme, in step S5, the data set is divided into a training set, a test set, and a validation set, and the training set, the test set, and the validation set are classified in a ratio of 0.70:0.15:0.15.

[0018] According to the above scheme, the training set is used to train the data set of model parameters; the validation set is used to check the state and convergence of the model during the training process; and the test set is used to evaluate the generalization ability of the model.

[0019] According to the above solution, in step S5, the BP neural network is divided into: an input layer, a hidden layer, and an output layer; the number of hidden layers is 3; the number of neurons is the input amount*2+1, which is 13 in total.

[0020] The metal hydride hydrogen storage system and control method equipped with a composite heat exchanger according to the present invention have the following beneficial effects:

[0021] 1. The present invention is equipped with a composite heat exchange system, which can achieve a wide range of hydrogen supply rate control;

[0022] 2. The phase change material of the present invention can absorb the heat released during the hydrogen absorption process of the metal hydride and use it in the dehydrogenation process, thereby realizing heat recovery and utilization;

[0023] 3. The present invention relates to a dehydrogenation rate prediction method based on a BP neural network model. According to different control condition parameters, the dehydrogenation rate can be predicted within seconds. For the same metal hydride hydrogen storage system, the numerical model established by COMSOL software takes at least several hours to calculate the dehydrogenation rate, which greatly improves the calculation efficiency.

[0024] 4. The hydrogen consumption prediction model based on BP neural network in the present invention has a certain universality and is applicable to different types of hydrogen-using equipment and hydrogen storage systems of different capacities. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The present invention will be further described below with reference to the accompanying drawings and embodiments, in which:

[0026] Figure 1 Schematic diagram of the structure of the metal hydride hydrogen storage system equipped with a composite heat exchanger of the present invention;

[0027] Figure 2 The numerical model of the present invention calculates the temperature, metal hydride density and phase change material liquid phase fraction cloud map;

[0028] Figure 3 Graph showing the change in dehydrogenation rate under different conditions of the present invention: a represents different heat transfer coefficients and circulating water temperatures, b represents different tank pressures and circulating water temperatures, and c represents the same tank pressure and heat transfer coefficient.

[0029] Figure 4 It is a flow chart of the method for controlling the dehydrogenation rate of a metal hydride hydrogen storage system of the present invention. DETAILED DESCRIPTION

[0030] In order to have a clearer understanding of the technical features, purposes and effects of the present invention, specific embodiments of the present invention are now described in detail with reference to the accompanying drawings.

[0031] like Figure 1-4As shown, the metal hydride hydrogen storage system equipped with a composite heat exchanger of the present invention includes a hydrogen quantity prediction system and a metal hydride hydrogen storage system. The composite heat exchanger comprises an external heat exchanger and an internal heat exchanger. The external heat exchanger is composed of a phase change material and metal foam jacketed outside the metal hydride storage tank, while the internal heat exchanger is composed of a tubular heat exchanger and metal fins embedded within the metal hydride hydrogen storage tank. The hydrogen quantity prediction system is used to predict the hydrogen demand of hydrogen-using equipment under different operating conditions and is composed of a controller based on a BP neural network. The metal hydride hydrogen storage system consists of a metal hydride and a composite heat exchanger. The hydrogen storage alloy is used to store hydrogen, and the composite heat exchanger is used to provide heat for metal hydride dehydrogenation. Hydrogen first decomposes catalytically on the surface of the hydrogen storage alloy into atomic hydrogen. These hydrogen atoms then diffuse into the voids within the material's crystal lattice and are stored atomically within the metal crystal points, forming a metal hydride, where the hydrogen is stored. When the metal hydride is heated, it decomposes into the hydrogen storage alloy and hydrogen, releasing the hydrogen. The hydrogen absorption and dehydrogenation processes of the hydrogen storage alloy are reversible, enabling the use of hydrogen storage alloys for hydrogen storage. The metal foam is nickel, a material with high air permeability, high specific surface area, and capillary strength. The phase change material is commercial paraffin wax RT35. The tubular heat exchanger contains water as a coolant. The metal fins are thin, smooth metal sheets with a large specific surface area.

[0032] The metal hydride hydrogen storage system equipped with a composite heat exchanger includes a hydrogen consumption prediction system and a metal hydride hydrogen storage system. The hydrogen consumption prediction system is a hydrogen consumption prediction model based on a BP neural network. A multi-physics field COMSOL numerical model verified by laboratory data is constructed to clarify the evolution of the hydrogen supply rate of the metal hydride hydrogen storage system under different operating parameters, including initial temperature, ambient temperature, initial pressure, outlet pressure, circulating water temperature, circulating water flow rate, etc. The BP neural network model is used to establish the correspondence between the hydrogen supply rate and the above operating parameters, thereby realizing real-time prediction of the fuel demand of hydrogen-using equipment. The metal hydride hydrogen storage system consists of a composite heat exchanger and metal hydride. The composite heat exchanger consists of an external heat exchanger and an internal heat exchanger. The external heat exchanger is composed of phase change material and metal foam, and the internal heat exchanger is composed of a tubular heat exchanger and metal fins. When the hydrogen demand is small or during cold start, the metal hydride hydrogen storage system is heated by the external heat exchanger alone to meet the heat required in the metal hydride dehydrogenation process; when the hydrogen demand is large, the metal hydride hydrogen storage system is heated by both the external heat exchanger and the internal heat exchanger to meet the heat required in the metal hydride dehydrogenation process.

[0033] The present invention also provides a method for controlling a metal hydride hydrogen storage system equipped with a composite heat exchanger. During the dehydrogenation process of the metal hydride hydrogen storage system, i.e., the process of supplying hydrogen to hydrogen-using equipment, the metal hydride is converted into a hydrogen storage alloy and hydrogen gas. The specific steps of the method for controlling the hydrogen supply rate of the metal hydride hydrogen storage system are as follows:

[0034] S1. A numerical model of the metal hydride hydrogen storage system is established based on the multi-physics simulation software COMSOL, considering the dimensions and experimental conditions of the metal hydride hydrogen storage system, the physical properties of the built-in metal hydride, the physical properties of hydrogen, as well as the laws of conservation of mass, conservation of momentum, conservation of energy, the metal hydride reaction kinetics equation, the equilibrium pressure equation, and the ideal gas state equation.

[0035] S2. Compare the simulated values ​​of the monitoring point temperature in the metal hydride bed and the system hydrogen storage capacity with the experimental data to verify the effectiveness of the numerical model.

[0036] S3. Based on the verified metal hydride hydrogen storage model, a spiral tube heat exchanger is added inside the metal hydride storage tank, and a phase change material heat exchanger is added outside the metal hydride storage tank to construct a metal hydride hydrogen storage model equipped with a composite heat exchanger.

[0037] S4. Select operating parameters, including heat transfer coefficient, circulating water temperature, tank pressure, etc., conduct parameter research, and analyze the evolution of the hydrogen supply rate of the metal hydride hydrogen storage system equipped with a composite heat exchanger under different operating parameter conditions.

[0038] S5. Based on the results of parameter research, a data set including operating conditions and hydrogen supply rate was constructed; the data set was divided into training set, test set, and validation set at a ratio of 0.70:0.15:0.15, and its accuracy was verified while training the BP neural network model; a BP neural network model was constructed, with the above operating conditions as input and the hydrogen supply rate as output, and the BP neural network was trained using the existing data set to establish the corresponding relationship between different operating conditions and hydrogen supply rate, so as to realize the prediction of the hydrogen supply rate of the metal hydride hydrogen storage system; the BP neural network was divided into three layers: input layer, hidden layer, and output layer; the number of hidden layers was 3; the number of neurons was input*2+1, for a total of 13.

[0039] The training set is a dataset used to train model parameters. The validation set is used to test the model's performance and convergence during training. The validation set is often used to adjust hyperparameters, determining which set of hyperparameters yields the best performance based on the performance of several models on the validation set. The test set is used to evaluate the model's generalization ability. This means that the model's hyperparameters are determined using the validation set, then adjusted using the training set. Finally, a never-before-seen dataset is used to determine the reliability of the model. The dataset is divided into these three categories proportionally, and the BP neural network is trained, validated, and tested sequentially to achieve optimal performance.

[0040] In a preferred embodiment of the present invention, the outer tank wall, phase change material heat exchanger, inner tank wall, metal hydride, and spiral tube heat exchanger are included. In the numerical model, the outer tank wall, inner tank wall, and spiral tube wall are ignored. The three-dimensional spiral tube is simplified to a two-dimensional spiral ring tube, thereby simplifying the complex three-dimensional model into a two-dimensional axisymmetric model and reducing the computational complexity of the numerical model. To ensure the accuracy of the simplified model, the number of spiral tubes is generally greater than eight.

[0041] A model of the metal hydride hydrogen storage system was constructed using the multiphysics simulation software COMSOL, based on the structural parameters of the metal hydride hydrogen storage system, the physical properties of LaNi5 hydride, the physical properties of hydrogen, the laws of conservation of mass, momentum, and energy, the LaNi5 hydride reaction kinetics, the equilibrium pressure equation, and the ideal gas equation. The validity of the basic LaNi5 hydride hydrogen storage numerical model was verified by comparing experimental and simulated values ​​for the temperature at monitoring points within the storage tank and the system's hydrogen storage mass.

[0042] Based on the verified numerical model of the LaNi5 hydrogen hydride storage system, commercial paraffin wax RT35 is used as the phase change material. Together with nickel foam metal with high air permeability, high specific surface area, and capillary force, it forms an external heat exchanger, which is installed on the outside of the LaNi5 hydrogen hydride storage system model. An internal heat exchanger, composed of a composite tubular heat exchanger and metal fins, is added internally to meet the heat transfer requirements of the metal hydride hydrogen storage system under different operating conditions. The complex three-dimensional model is simplified into a two-dimensional axisymmetric model. By setting initial and boundary conditions, COMSOL software can be used to simulate the internal fluid flow, heat and mass transfer phenomena, and system performance parameters of the metal hydride hydrogen storage system equipped with a composite heat exchanger, such as the distribution cloud of the metal hydride hydrogen storage system temperature, density, and phase change material liquid fraction at different times.

[0043] Through the numerical model of the metal hydride hydrogen storage system equipped with a composite heat exchanger, a parameter study was carried out to analyze the effects of different operating parameters such as heat transfer coefficient, circulating water temperature and tank pressure on the dehydrogenation rate of the device. The simulation results are as follows: Figure 3 shown.

[0044] Based on the results of parameter research, a data set including different operating parameters and dehydrogenation rates was constructed. The data set was divided into training set, test set, and validation set at a ratio of 0.70:0.15:0.15, and its accuracy was verified while training the BP neural network model. The BP neural network model contains three layers: input layer, hidden layer, and output layer; the number of hidden layers is 3; the number of neurons is the input * 2 + 1, a total of 13. The BP neural network model uses operating parameters such as heat transfer coefficient, circulating water temperature, and tank pressure as input, and the dehydrogenation rate of the metal hydride hydrogen storage system equipped with a composite heat exchanger as output. The trained and verified BP neural network model can predict the dehydrogenation rate according to different operating conditions, and can also query the operating conditions based on the dehydrogenation rate, establish the corresponding relationship between different operating conditions and dehydrogenation rate, and achieve precise control of the dehydrogenation rate.

[0045] The embodiments of the present invention are described above in conjunction with the accompanying drawings, but the present invention is not limited to the above-mentioned specific implementation methods. The above-mentioned specific implementation methods are merely illustrative and not restrictive. Under the guidance of the present invention, ordinary technicians in this field can also make many forms without departing from the scope of protection of the present invention and the claims, all of which are protected by the present invention.

Claims

1. A control method for a metal hydride hydrogen storage system equipped with a composite heat exchanger, comprising a hydrogen quantity prediction system, a composite heat exchanger, and a metal hydride storage tank. The composite heat exchanger comprises an external heat exchanger and an internal heat exchanger. The external heat exchanger comprises a phase change material and a metal foam, which are disposed in the form of a jacket on the outside of the metal hydride storage tank. The internal heat exchanger comprises a tubular heat exchanger and metal fins built into the metal hydride hydrogen storage tank. The hydrogen quantity prediction system is used to predict the hydrogen demand of hydrogen-using equipment under different operating conditions, and is characterized in that: The following steps are involved: S1. Establish a numerical model of metal hydride hydrogen storage system; The numerical model is established based on the multi-physics simulation software COMSOL, targeting the size and experimental conditions of the metal hydride hydrogen storage system, the physical properties of the built-in metal hydride, the physical properties of hydrogen, as well as the law of conservation of mass, the law of conservation of momentum, the law of conservation of energy, the metal hydride reaction kinetics equation, the equilibrium pressure equation, and the ideal gas state equation; S2. Compare the simulated values ​​of the temperature at the monitoring points in the metal hydride bed and the hydrogen storage capacity of the system with the experimental data to verify the validity of the numerical model of the metal hydride hydrogen storage system; S3. Based on the verified numerical model of the metal hydride hydrogen storage system, a metal hydride hydrogen storage model equipped with a composite heat exchanger is constructed; S4. Select operating parameters, conduct parameter research, and analyze the evolution of the hydrogen supply rate of the metal hydride hydrogen storage system equipped with a composite heat exchanger under different operating parameter conditions; The selected operating parameters include heat transfer coefficient, circulating water temperature, and tank pressure; S5. Based on the results of the parameter study, a data set is constructed; the data set is divided into a training set, a test set, and a validation set, and the accuracy of the data set is verified while training the BP neural network model; a BP neural network model is constructed, with the above-mentioned operating parameter conditions as input and the hydrogen supply rate as output, and the BP neural network is trained using the existing data set to establish the corresponding relationship between different operating parameter conditions and the hydrogen supply rate, thereby realizing the prediction of the hydrogen supply rate of the metal hydride hydrogen storage system.

2. The control method of the metal hydride hydrogen storage system equipped with a composite heat exchanger according to claim 1, characterized in that: In step S3, in the metal hydride hydrogen storage model, a spiral tube heat exchanger is added inside the metal hydride storage tank, and a phase change material heat exchanger is added outside the metal hydride storage tank.

3. The control method of the metal hydride hydrogen storage system equipped with a composite heat exchanger according to claim 1, characterized in that: In step S5, the data set is divided into a training set, a test set, and a validation set, and the training set, the test set, and the validation set are classified in a ratio of 0.70:0.15:0.

15.

4. The control method of the metal hydride hydrogen storage system equipped with a composite heat exchanger according to claim 3, characterized in that: The training set is a data set used to train the parameters within the model; the validation set is used to check the state and convergence of the model during the training process; and the test set is used to evaluate the generalization ability of the model.

5. The control method of the metal hydride hydrogen storage system equipped with a composite heat exchanger according to claim 1, characterized in that: In step S5, the BP neural network is divided into: an input layer, a hidden layer, and an output layer; the number of hidden layers is 3.

6. The control method of the metal hydride hydrogen storage system equipped with a composite heat exchanger according to claim 1, characterized in that: The hydrogen quantity prediction system includes a controller based on BP neural network.

7. The control method of the metal hydride hydrogen storage system equipped with a composite heat exchanger according to claim 1, characterized in that: The metal foam is nickel metal with high air permeability, high specific surface area and capillary force; the phase change material is commercial paraffin RT35; a coolant is provided in the tubular heat exchanger, and the coolant is water; the metal fins are metal sheets with smooth surfaces and large specific surface area.

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