Simulation method for hydrogen absorption / desorption process of titanium-based hydrogen storage block packed bed

Abstract

The invention discloses a method for simulating a hydrogen absorption / desorption process of a titanium-based hydrogen storage block accumulation bed, and relates to the technical field of hydrogen storage, the method comprises the following steps: step 1, constructing a random accumulation three-dimensional model of blocks with specified sizes under the action of gravity; 2, aiming at the hydrogen storage capacity of the maximum accumulation bed volume, setting and optimizing different block sizes by taking the bed void ratio as a target; and step 3, aiming at the hydrogen absorption / desorption process of the target titanium-based hydrogen storage block accumulation bed, constructing a three-dimensional multi-physical field thermal mass coupling model for the titanium-based hydrogen storage block accumulation bed. According to the method, the influence distribution model of random accumulation of the hydrogen storage blocks on heat and mass transfer is considered, the heat and mass transfer coupling model method is established, and the accuracy of the heat and mass transfer model in the hydrogen absorption / desorption process is improved. In addition, according to the method, the size of the optimized block is optimized, so that the volume hydrogen storage density of the titanium-based solid hydrogen storage device is effectively improved.

Description

Technical Field

[0001] The invention relates to the technical field of hydrogen storage, and in particular to a method for simulating a hydrogen absorption / desorption process of a titanium-based hydrogen storage block stacking bed. Background Art

[0002] Metal hydride hydrogen storage technology is an important supporting technology for commercial hydrogen storage and transportation due to its high volumetric hydrogen storage density and safety. Among the many solid-state hydrogen storage routes, titanium-based solid-state hydrogen storage devices with titanium-based hydrogen storage materials as the core have the advantages of abundant resource reserves, low cost, and room temperature hydrogen absorption and release. They are currently the most promising technology for commercial application. However, existing titanium-based hydrogen storage devices have problems such as poor operating performance, uneven temperature / pressure distribution, and high energy consumption, which will seriously affect the efficiency and operational flexibility of the device in the application scenarios of renewable energy consumption and mobile hydrogen storage. At present, there are some studies on the stacked bed and hydrogen storage block of hydrogen storage units. The research on hydrogen storage units is often simulated by establishing a homogenized thermal-mass coupling model. Since the models all assume that the hydrogen storage materials are uniform, but the materials in the actual hydrogen storage devices are pressed into blocks, they cannot reflect the complex thermal and mass flow of the block bed; the research on blocks often focuses on microscopic properties such as powder diameter, block porosity, and material defects, and lacks the simulation of the block stacking in the stacked bed and the optimization of the block size. It is still a challenge to integrate and optimize the block size to establish a thermal-mass coupling model based on the block stacked bed hydrogen storage unit, so as to accurately simulate various indicators of the hydrogen storage unit.

[0003] Therefore, technicians in this field are committed to developing a simulation method for the hydrogen absorption / desorption process of a titanium-based hydrogen storage block stacked bed. Summary of the invention

[0004] In view of the above-mentioned defects of the prior art, the technical problem to be solved by the present invention is that the thermal and mass coupling model of the titanium-based hydrogen storage unit for hydrogen absorption / desorption of the existing block stacking bed model cannot be determined, the stacking condition of the blocks of the hydrogen storage device cannot be simulated and determined, and the optimal geometric dimensions of the blocks of the hydrogen storage device cannot be determined.

[0005] To achieve the above object, the present invention provides a method for simulating the hydrogen absorption / desorption process of a titanium-based hydrogen storage block stacked bed, the method comprising the following steps:

[0006] Step 1: construct a three-dimensional model of random stacking of blocks of specified size under gravity;

[0007] Step 2: for the maximum stacked bed volume hydrogen storage capacity, with the bed void ratio as the target, different block sizes are set and optimized;

[0008] Step 3: Aiming at the hydrogen absorption / desorption process of the target titanium-based hydrogen storage block stacked bed, a three-dimensional multi-physics field thermal-mass coupling model for the titanium-based hydrogen storage block stacked bed is constructed.

[0009] Furthermore, the step 1 specifically constructs a three-dimensional random stacking model of blocks of specified sizes under gravity based on the open source discrete element software yade.

[0010] Furthermore, the random stacking three-dimensional model in step 1 specifically includes a block contact model and a position update model.

[0011] Furthermore, the step 2 is specifically as follows: different block diameters and thicknesses are selected to simulate and obtain the corresponding stacked bed void fraction, and the block size corresponding to the minimum bed void fraction is selected as the optimal value.

[0012] Furthermore, the specific method for optimization in step 2 is: based on the random stacking three-dimensional model of step 1, simulate the random stacking of a large number of blocks in a cylindrical area under the action of gravity, take minimizing the space not occupied by blocks in the cylindrical area per unit volume as the optimization goal, and optimize the block size by changing the block diameter and thickness.

[0013] Furthermore, the step 3 is specifically as follows: based on the block stacking three-dimensional model mentioned in the step 1 and the optimal block size in the step 2, a multi-physics coupling model for the titanium-based hydrogen storage block stacking bed is constructed using finite element multi-physics simulation software.

[0014] Furthermore, the step 3 specifically includes:

[0015] Step 3.1, obtain the corresponding material including bulk thermal conductivity and material hydrogen absorption / desorption thermodynamic model;

[0016] Step 3.2, based on step 2, obtaining an optimal stacked bed three-dimensional model and constructing a grid;

[0017] Step 3.3, construct a three-dimensional multi-physics thermal-mass coupling model of the bulk stacking bed;

[0018] Step 3.4: Calculate the model to obtain hydrogen absorption / desorption process information of the hydrogen storage unit.

[0019] Furthermore, the three-dimensional multi-physics field heat-mass coupling model of the block packed bed in step 3.3 is established based on the porous medium mass transfer equation, the porous medium heat transfer equation, the thermal conductivity equation and the material thermal / kinetic equation.

[0020] Furthermore, the three-dimensional multi-physics field thermal-mass coupling model in step 3.3 is constructed and calculated using the finite element multi-physics field software COMSOL.

[0021] Furthermore, the hydrogen absorption / desorption process information of the hydrogen storage unit in step 3.4 includes the stacked bed temperature, pressure, hydrogen content and heat flux.

[0022] Compared with the prior art, the present invention has the following beneficial technical effects:

[0023] 1. In order to solve the problem that the heat and mass coupling model of hydrogen absorption / desorption in titanium-based hydrogen storage units based on the block stacked bed model cannot be determined, this paper proposes a simulation method for heat and mass coupling of hydrogen absorption / desorption based on a three-dimensional stacked bed model with optimized block size. Compared with the traditional homogenized assumption model, it can effectively improve the model accuracy and simulate flow field changes.

[0024] 2. In order to solve the problem that the block stacking condition of the hydrogen storage device cannot be simulated and determined, the present invention establishes a block stacking bed model that is randomly stacked under the action of gravity based on discrete element software, accurately simulates the block stacking condition in the stacking bed, and provides a three-dimensional model basis for subsequent modeling work.

[0025] 3. In order to solve the problem that the optimal geometric dimensions of the hydrogen storage device blocks cannot be determined, the present invention optimizes the dimensions of the hydrogen storage blocks with the goal of minimizing the void ratio of the stacked bed, thereby significantly reducing the void ratio of the stacked bed, increasing the volumetric hydrogen storage capacity of the block stacked bed, and being able to improve the capacity of the corresponding hydrogen storage device.

[0026] Compared with the existing methods, the present invention proposes a simulation method that considers the distribution model of the random stacking of hydrogen storage blocks on the heat and mass transfer, and establishes a heat and mass transfer coupling model method, thereby improving the accuracy of the heat and mass transfer model of the hydrogen absorption / desorption process. In addition, the method effectively improves the volume hydrogen storage density of the titanium-based solid-state hydrogen storage device by optimizing the optimized block size.

[0027] The concept, specific structure and technical effects of the present invention will be further described below in conjunction with the accompanying drawings to fully understand the purpose, characteristics and effects of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a schematic flow diagram of a method for simulating the hydrogen absorption / desorption process of a titanium-based hydrogen storage block stacked bed of the present invention;

[0029] Figure 2 The block stacking bed void ratio and block size correspondence in the embodiment of the present invention;

[0030] Figure 3 is the block stacking condition when the block size is optimal in the embodiment of the present invention;

[0031] Figure 4 is the grid division result corresponding to the optimal stacking condition in the embodiment of the present invention;

[0032] Figure 5 It is a comparison of external heat flux at different virtual startup times in an embodiment of the present invention;

[0033] Figure 6 is a comparison of the highest, average and lowest hydrogen contents at different virtual start-up times in the embodiment of the present invention;

[0034] Figure 7 is a comparison of the highest, average and lowest pressures at different virtual start-up times in an embodiment of the present invention;

[0035] Figure 8 It is a comparison of the highest, average and lowest temperatures at different virtual startup times in the embodiment of the present invention. DETAILED DESCRIPTION

[0036] The following describes several preferred embodiments of the present invention with reference to the drawings in the specification, so that the technical content is clearer and easier to understand. The present invention can be embodied in many different forms of embodiments, and the protection scope of the present invention is not limited to the embodiments mentioned in the text.

[0037] In the drawings, components with the same structure are indicated by the same numerical reference numerals, and components with similar structures or functions are indicated by similar numerical reference numerals. The size and thickness of each component shown in the drawings are arbitrarily shown, and the present invention does not limit the size and thickness of each component. In order to make the illustration clearer, the thickness of the components is appropriately exaggerated in some places in the drawings.

[0038] like Figure 1 As shown, a method for simulating the hydrogen absorption / desorption process of a titanium-based hydrogen storage block stacked bed, the method specifically comprises the following steps:

[0039] Step 1: construct a three-dimensional model of random stacking of blocks of specified size under gravity;

[0040] Step 2: for the maximum stacked bed volume hydrogen storage capacity, with the bed void ratio as the target, different block sizes are set and optimized;

[0041] Step 3: Aiming at the hydrogen absorption / desorption process of the target titanium-based hydrogen storage block stacked bed, a three-dimensional multi-physics field thermal-mass coupling model for the titanium-based hydrogen storage block stacked bed is constructed.

[0042] This embodiment is aimed at the hydrogen release process of a hydrogen storage unit formed by stacking compressed blocks of a certain titanium-based hydrogen storage material. The main parameters of the material and the blocks are shown in Table 1.

[0043] Table 1. Main working parameters of titanium-based materials and blocks in this example

[0044]

[0045] The block diameter and block thickness are the optimization results of yade software simulation. The optimization method is to select different block diameters and thicknesses to simulate the corresponding stacking bed void fraction, and select the block size corresponding to the minimum bed void fraction as the optimal value. In the embodiment, after defining parameters such as block density, Young's modulus and friction angle, the PotentialBlock command is used to define the block, the cylindricalPlates and inCylinder commands are used to construct the cylindrical area, and the makeCloud command is used to randomly generate 1000 blocks in the cylindrical area, and then a random stacking simulation is performed under the action of gravity. The time step is 0.00001 seconds, and the simulation is simulated for a total of 10 seconds. The optimization goal is to minimize the space not occupied by the block in the cylindrical area per unit volume. The optimization results are as follows: Figure 2 As shown in the figure, when the porosity of the stacked bed is the lowest, the block diameter is 10 mm, the thickness is 8 mm, and the porosity of the stacked bed is 40%. Thus, the optimal stacked bed three-dimensional model is obtained, and the stacking situation is as follows Figure 3 Then, the position information of each block at the last moment is saved as a vtk format file using VTKExporter.

[0046] First, the corresponding materials including block thermal conductivity and material hydrogen absorption / desorption thermodynamic model are obtained. Then, the finite element multi-physics software COMSOL is used to simulate the model construction and calculation. Based on the above vtk file, a Python script is written to obtain the angle normal vector and center point position of each block, and converted into a csv format file. COMSOL with Matlab is used to read the block position information file and write a script to establish the corresponding cylinder of each block, and a multi-physics coupling model for titanium-based hydrogen storage block stacking bed is constructed. The parameters of the constructed model are shown in Table 1. After importing the geometry module, the mesh result is as follows: Figure 4 As shown. Finally, the model is calculated to obtain the hydrogen absorption / desorption process information of the hydrogen storage unit. The virtual desorption time t' is set to 15000s and 1500s respectively, and the model is solved to obtain the heat flux, hydrogen content, pressure and temperature results at the corresponding time t', as shown respectively. Figures 5 to 8 As shown. According to the results, when t'=1500s, the stacked bed rapidly releases hydrogen for a period of time; at this time, the external heat flux is negative and the absolute value continues to increase, indicating that the temperature of the outermost layer continues to decrease; the pressure, temperature and hydrogen content all decrease. Then it enters the bottleneck. Since the pressure distribution is relatively uniform, it can be inferred that the temperature is the limiting factor at this time. Due to the rapid release of hydrogen and heat absorption by the stacked bed, the temperature drops too fast. Although the outer wall is at a constant temperature, it is restricted by the porous medium and hydrogen and cannot effectively supply heat to the unit. The device cannot completely release the hydrogen and enters the bottleneck. When t'=15000s, the hydrogen release rate is reduced, the hydrogen release time is extended, but the amount of hydrogen released is greater.

[0047] In summary, this embodiment simulates the dehydrogenation process of a titanium-based hydrogen storage material block stacked bed, optimizes the block size, and simulates different dehydrogenation rate processes. The results show that the block size optimization and hydrogen absorption / dehydrogenation process simulation method for titanium-based hydrogen storage block stacked bed proposed in the present invention can significantly improve the volume hydrogen storage capacity of the stacked bed and accurately reflect the changes in various physical quantities in the hydrogen absorption / dehydrogenation process.

[0048] The preferred specific embodiments of the present invention are described in detail above. It should be understood that ordinary technicians in the field can make many modifications and changes based on the concept of the present invention without creative work. Therefore, all technical solutions that can be obtained by technicians in the technical field based on the concept of the present invention through logical analysis, reasoning or limited experiments on the basis of the prior art should be within the scope of protection determined by the claims.

Claims

1. A method for simulating the hydrogen absorption / desorption process of a titanium-based hydrogen storage block stacked bed, characterized in that: The method comprises the following steps: Step 1: construct a three-dimensional model of random stacking of blocks of specified size under gravity; Step 2: for the maximum stacked bed volume hydrogen storage capacity, with the bed void ratio as the target, different block sizes are set and optimized; Step 3: Aiming at the hydrogen absorption / desorption process of the target titanium-based hydrogen storage block stacked bed, a three-dimensional multi-physics field thermal-mass coupling model for the titanium-based hydrogen storage block stacked bed is constructed.

2. The method for simulating the hydrogen absorption / desorption process of the titanium-based hydrogen storage block stacked bed according to claim 1, characterized in that: The step 1 specifically involves constructing a three-dimensional random stacking model of blocks of specified sizes under gravity based on the open source discrete element software yade.

3. The method for simulating the hydrogen absorption / desorption process of the titanium-based hydrogen storage block stacked bed according to claim 1, characterized in that: The random stacking three-dimensional model in step 1 specifically includes a block contact model and a position update model.

4. The method for simulating the hydrogen absorption / desorption process of the titanium-based hydrogen storage block stacked bed according to claim 1, characterized in that: The step 2 specifically includes: selecting different block diameters and thicknesses to simulate and obtain the corresponding stacked bed void ratio, and selecting the block size corresponding to the minimum bed void ratio as the optimal value.

5. The method for simulating the hydrogen absorption / desorption process of the titanium-based hydrogen storage block stacked bed according to claim 1, characterized in that: The specific method for optimization in step 2 is: based on the random stacking three-dimensional model of step 1, simulate the random stacking of a large number of blocks in a cylindrical area under the action of gravity, take the minimum space not occupied by blocks in the cylindrical area per unit volume as the optimization goal, and optimize the block size by changing the block diameter and thickness.

6. The method for simulating the hydrogen absorption / desorption process of the titanium-based hydrogen storage block stacked bed according to claim 1, characterized in that: The step 3 is specifically as follows: based on the block stacking three-dimensional model mentioned in the step 1 and the optimal block size in the step 2, a multi-physics coupling model for the titanium-based hydrogen storage block stacking bed is constructed using finite element multi-physics simulation software.

7. The method for simulating the hydrogen absorption / desorption process of a titanium-based hydrogen storage block stacked bed according to claim 1, characterized in that: The step 3 specifically includes: Step 3.1, obtain the corresponding material including bulk thermal conductivity and material hydrogen absorption / desorption thermodynamic model; Step 3.2, based on step 2, obtaining an optimal stacked bed three-dimensional model and constructing a grid; Step 3.3, construct a three-dimensional multi-physics thermal-mass coupling model of the bulk stacking bed; Step 3.4: Calculate the model to obtain hydrogen absorption / desorption process information of the hydrogen storage unit.

8. The method for simulating the hydrogen absorption / desorption process of the titanium-based hydrogen storage block stacked bed according to claim 7, characterized in that: The three-dimensional multi-physics field heat-mass coupling model of the block stacking bed in step 3.3 is established based on the porous medium mass transfer equation, the porous medium heat transfer equation, the thermal conductivity equation and the material thermal / kinetic equation.

9. The method for simulating the hydrogen absorption / desorption process of a titanium-based hydrogen storage block stacked bed according to claim 7, characterized in that: The three-dimensional multi-physics field thermal-mass coupling model in step 3.3 is constructed and calculated using the finite element multi-physics field software COMSOL.

10. The method for simulating the hydrogen absorption / desorption process of a titanium-based hydrogen storage block stacked bed according to claim 7, characterized in that: The hydrogen absorption / desorption process information of the hydrogen storage unit in step 3.4 includes the stacked bed temperature, pressure, hydrogen content and heat flux.

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