A method for simulating phase change porous medium thermal fluid-solid coupling multiphase percolation

Abstract

The application discloses a kind of porous medium heat flow solidification coupling multiphase percolation simulation methods containing phase change, the method comprises the following steps: using ICEM modeling software to establish the grid model of porous medium pore structure, and according to actual working condition, the boundary condition of the grid model is set;Construct multiphase fluid heat and mass transfer mathematical model, and the multiphase fluid heat and mass transfer mathematical model is embedded into Fluent software;The grid model of the fluid domain and the grid model of phase change solid domain are assembled, and are imported into Fluent software;Based on the boundary condition of the grid model, numerical simulation analysis is carried out using Fluent software.This method can not only study the dynamics mechanism of phase change-chemical reaction in porous medium and the evolution law of its pore structure characteristics, but also can obtain the distribution law of multiphase fluid in porous medium, velocity field, temperature field distribution and each phase permeability evolution curve in real time, and has wide application prospect.

Description

Technical Field

[0001] This invention relates to the field of multiphase fluid seepage, and more specifically to a multiphase seepage simulation method involving thermal flow solidification coupling of porous media with phase change. Background Technology

[0002] In engineering practices such as natural gas hydrate extraction, acid fracturing of carbonate oil and gas reservoirs, CO2 geological storage, and prediction and remediation of underground pollutant transport, dynamic coupling problems such as formation pore blockage or expansion caused by chemical reaction products and multiphase fluid seepage are often encountered. Coupled with the complexity and opacity of the pore structure of natural porous media, this leads to a variety of engineering challenges. Although these engineering challenges face different engineering geological and hydrogeological conditions (reservoir conditions), and their engineering manifestations and conditions also differ, they are essentially a complex heat and mass transfer problem in porous media involving the coupling of phase transitions, dynamic boundaries, chemical kinetics, and multiphase fluid seepage.

[0003] Existing simulation methods often simplify chemical reaction products into multi-component transport processes in a single-phase fluid, neglecting the seepage mechanism of multiphase fluids. In addition, the pixel volume method (VOP) used for phase change processes in chemical reactions only transforms into fluid nodes after the solid reaction at the computation node is complete, which cannot reflect the real-time evolution characteristics of phase change chemical reactions on the pore structure of porous media.

[0004] Therefore, existing technologies still need to be improved and developed. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a multiphase percolation simulation method for porous media with phase change thermal flow solidification coupling, which addresses the above-mentioned deficiencies of the prior art. The aim is to solve the problems in the prior art that ignore the percolation mechanism of multiphase fluids and cannot reflect the real-time evolution characteristics of the pore structure of porous media caused by phase change chemical reactions.

[0006] The technical solution adopted by this invention to solve the technical problem is as follows:

[0007] In a first aspect, the present invention provides a method for simulating multiphase percolation coupled with thermal flow solidification in porous media containing phase change, characterized in that the method comprises:

[0008] A mesh model of the porous medium pore structure was established using ICEM modeling software, and the boundary conditions of the mesh model were set according to the actual working conditions; wherein, the mesh model includes: a mesh model of the fluid domain and a mesh model of the phase change solid domain;

[0009] A mathematical model for heat and mass transfer in multiphase fluids is constructed and embedded into Fluent software.

[0010] The mesh models of the fluid domain and the phase change solid domain are assembled and imported into Fluent software.

[0011] Numerical simulation analysis was performed using Fluent software based on the boundary conditions of the mesh model.

[0012] In one implementation, constructing a multiphase fluid heat and mass transfer mathematical model and embedding the multiphase fluid heat and mass transfer mathematical model into Fluent software includes:

[0013] Construct a mathematical model of the chemical reaction to obtain the mass source term;

[0014] The enthalpy change-porosity method is used to track the fluid and solid phase interfaces in chemical reaction regions involving phase change in order to obtain the momentum source term;

[0015] Based on the basic equations of the North and South, a mathematical model of multiphase fluid seepage and an enthalpy change model of chemical reaction are constructed to obtain the energy source term;

[0016] Based on the mass source term, the momentum source term, and the energy source term, the mathematical model for heat and mass transfer in the multiphase fluid is obtained.

[0017] The mathematical model of multiphase fluid heat and mass transfer is embedded into the Fluent software.

[0018] In one implementation, constructing a mathematical model of the chemical reaction to obtain mass source terms includes:

[0019] The reaction process for phase change to generate gas within the porous medium is obtained based on the chemical reaction equation.

[0020] Based on the Arrhenius chemical kinetic model, the formation rate of the reaction products is as follows:

[0021]

[0022] Among them, A r It is a reaction factor, E r It is the activation energy of the reaction, R is the universal gas constant, T is the temperature, and β is the activation energy of the reaction. r It is the temperature index, M r Let r be the molar molecular mass of the reaction product r;

[0023] A mathematical model of the chemical reaction is obtained based on the reaction process and the generation rate, and the mathematical model of the chemical reaction is compiled to obtain the mass source term.

[0024] In one implementation, the use of the enthalpy change-porosity method to track the fluid-solid phase interface in a chemical reaction region involving phase change to obtain the momentum source term includes:

[0025] The porosity φ of the chemical reaction region containing the phase change is determined to be...

[0026] φ=1-α h ,

[0027] Where, α h It is the volume fraction of hydrate in the grid cells of the grid model;

[0028] The enthalpy of the material in the chemical reaction region containing the phase transition is determined to be...

[0029]

[0030] Where h is the visible enthalpy, ΔH is the heat of reaction, and h ref It is the reference enthalpy, T ref This is the reference temperature, C. p It is a constant pressure specific heat;

[0031] The heat of reaction in the chemical reaction region containing the phase change is determined to be...

[0032] ΔH=φΔH d ,

[0033] Where, ΔH d The latent heat of a chemical reaction;

[0034] The flow of the multiphase fluid in the chemical reaction region containing the phase change is determined according to the classical Darcy's law;

[0035] Determine the momentum source term as

[0036]

[0037] Among them, K e The effective porosity of the chemical reaction region containing the phase change follows the classical Carman-Koseny equation. It is a velocity vector, A pseudo It is the porous medium constant, which determines the damping amplitude during the process of fluid velocity dropping to 0.

[0038] In one implementation, the establishment of a multiphase fluid seepage mathematical model based on the fundamental equations of the North Face (NS) to obtain the energy source term includes:

[0039] Based on the aforementioned NS fundamental equations, the governing equations for mass conservation, momentum conservation, and energy conservation are obtained as follows:

[0040]

[0041]

[0042]

[0043] Where μ and ρ are the volume average viscosity and density of each phase fluid in the unit grid, and α i , ρ i , Let be the volume fraction, density, and velocity vector of the i-th phase fluid, respectively. It is a velocity vector, m ij It is the mass transport source term from the i-th phase fluid to the j-th phase fluid. S is the acceleration due to gravity. m It is the mass source term caused by the decomposition reaction of hydrates, and H is the enthalpy change of the multiphase fluid;

[0044] Determine the enthalpy change of a multiphase fluid

[0045]

[0046] Among them, H i S is the enthalpy of the i-th phase fluid in the cell grid. E This is an energy source term resulting from the decomposition reaction of hydrates;

[0047] The energy source term is determined to be

[0048] S E =-m r ΔH d ,

[0049] Among them, H d It is the latent heat of a chemical reaction.

[0050] In one implementation, the numerical simulation analysis based on the boundary conditions of the mesh model using Fluent software includes:

[0051] In the Fluent software, the model interface is defined as the interior boundary condition;

[0052] Based on the boundary conditions of the mesh model, the boundary and computational domain temperature, pressure and flow boundary conditions are set in the Fluent software;

[0053] The heat and mass transfer mechanism of multiphase fluids was numerically simulated and analyzed using Fluent software.

[0054] In one implementation, the method further includes:

[0055] The porosity of the solid region where no phase change has occurred is determined to be 0, and the fluid flow rate is determined to be 0.

[0056] Secondly, the present invention provides a multiphase percolation simulation device for porous media with phase change thermal flow solidification coupling, characterized in that the device comprises:

[0057] The mesh model and boundary condition acquisition module is used to establish a mesh model of the porous structure of the porous medium using ICEM modeling software, and to set the boundary conditions of the mesh model according to the actual working conditions.

[0058] The model building module is used to build a mathematical model of multiphase fluid heat and mass transfer and embed the mathematical model of multiphase fluid heat and mass transfer into Fluent software;

[0059] The mesh model assembly module is used to assemble the mesh models of the fluid domain and the phase change solid domain and import them into Fluent software.

[0060] The simulation analysis module is used to perform numerical simulation analysis using Fluent software based on the boundary conditions of the mesh model.

[0061] Thirdly, the present invention provides a smart terminal, characterized in that the smart terminal includes a memory, a processor, and a numerical simulation program for multiphase fluid heat and mass transfer stored in the memory and executable on the processor. When the processor executes the simulation program for multiphase flow coupled with thermal flow solidification of porous media containing phase change, it implements the steps of the simulation method for multiphase flow coupled with thermal flow solidification of porous media containing phase change as described in any of the above claims.

[0062] Fourthly, the present invention provides a computer-readable storage medium, characterized in that the computer-readable storage medium stores a simulation program for thermal flow solidification coupled multiphase flow of porous media containing phase change, wherein when the simulation program for thermal flow solidification coupled multiphase flow of porous media containing phase change is executed by a processor, the steps of the simulation method for thermal flow solidification coupled multiphase flow of porous media containing phase change as described in any of the preceding claims are implemented.

[0063] Beneficial Effects: Compared with existing technologies, this invention provides a multiphase permeation simulation method for porous media with phase change involving thermal-fluid-solidification coupling. First, a mesh model of the porous media's pore structure is established using ICEM modeling software, and boundary conditions are set according to actual working conditions. Then, a multiphase fluid heat and mass transfer mathematical model is constructed and embedded into Fluent software. Next, the mesh models of the fluid domain and the phase change solid domain are assembled and imported into Fluent software. Finally, based on the boundary conditions of the mesh model, numerical simulation analysis is performed using Fluent software. This method can study the kinetic mechanism of phase change-chemical reactions within porous media and the evolution of their pore structure characteristics. It can also acquire in real-time the distribution patterns of multiphase fluids, velocity fields, temperature fields, and permeability evolution curves of each phase within the porous media, showing broad application prospects. Attached Figure Description

[0064] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0065] Figure 1 This is a flowchart of a multiphase percolation simulation method for porous media with phase change thermal flow solidification coupling provided in an embodiment of the present invention.

[0066] Figure 2 This is an example diagram of the porous media pore mesh model and boundary conditions provided in the embodiments of the present invention.

[0067] Figure 3 These are examples of phase equilibrium curves for decomposition reactions and initial-simulation temperature and pressure conditions in the computational domain of porous media provided in embodiments of the present invention.

[0068] Figure 4 These are curves showing the change in the content of reactants in the phase change-decomposition reaction over time, provided in the embodiments of the present invention, and comparison curves with simulated values ​​from the literature.

[0069] Figure 5 This is a cloud map showing the content and distribution of reactants at different time steps within a porous medium, provided in an embodiment of the present invention.

[0070] Figure 6 This is a cloud map showing the fluid velocity distribution at different time steps within a porous medium, provided in an embodiment of the present invention.

[0071] Figure 7 This is a temperature field distribution cloud map of a porous medium at different time steps provided in an embodiment of the present invention.

[0072] Figure 8 The absolute permeability (K) within the porous medium provided in the embodiments of the present invention N ) and aqueous phase (K Nw Evolution curve of saturation of non-aqueous fluid.

[0073] Figure 9 This is a schematic diagram of the numerical simulation device for multiphase fluid heat and mass transfer provided in an embodiment of the present invention.

[0074] Figure 10 This is a block diagram illustrating the internal structure of a smart terminal provided in an embodiment of the present invention. Detailed Implementation

[0075] To make the objectives, technical solutions, and effects of this invention clearer and more explicit, 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 of the invention and are not intended to limit the invention.

[0076] In engineering practices such as natural gas hydrate extraction, acid fracturing of carbonate oil and gas reservoirs, CO2 geological storage, and prediction and remediation of underground pollutant transport, dynamic coupling problems such as formation pore blockage or expansion caused by chemical reaction products and multiphase fluid seepage are often encountered. Coupled with the complexity and opacity of the pore structure of natural porous media, this leads to various engineering challenges. Although these engineering challenges face different engineering geological and hydrogeological conditions (reservoir conditions), and their engineering manifestations and conditions also differ, they are essentially a complex heat and mass transfer problem in porous media involving the coupling of phase transitions, dynamic boundaries, chemical kinetics, and multiphase fluid seepage. Existing simulation methods often simplify chemical reaction products into multi-component transport processes in a single-phase fluid, neglecting the seepage mechanism of multiphase fluids. Furthermore, the pixel volume method (VOP) used for phase transition processes in chemical reactions only transforms into fluid nodes after the solid reaction at the computational node is complete, failing to reflect the real-time evolution characteristics of the phase transition chemical reaction on the pore structure of the porous media.

[0077] Therefore, to address the aforementioned issues, this embodiment provides a method for simulating multiphase permeation in porous media involving phase change through thermal-fluid-solidification coupling. This method allows for the study of the kinetic mechanism of phase change-chemical reactions within porous media and the evolution of their pore structure characteristics. It also enables real-time acquisition of the multiphase fluid distribution, velocity field, temperature field distribution, and permeability evolution curves of each phase within the porous media. Specifically, this embodiment first uses ICEM modeling software to establish a mesh model of the porous media's pore structure and sets the boundary conditions of the mesh model according to actual operating conditions. Next, a multiphase fluid heat and mass transfer mathematical model is constructed and embedded into Fluent software. The mesh models of the fluid domain and the phase change solid domain are then assembled and imported into Fluent software. Finally, based on the boundary conditions of the mesh model, numerical simulation analysis is performed using Fluent software. This allows for the simulation of the kinetic mechanism of phase change-chemical reactions within porous media.

[0078] Exemplary methods

[0079] This embodiment provides a method for simulating multiphase percolation coupled with thermal flow solidification in porous media containing phase change. For example... Figure 1 As shown, the method includes the following steps:

[0080] Step S100: Use ICEM modeling software to establish a mesh model of the porous medium pore structure, and set the boundary conditions of the mesh model according to the actual working conditions; wherein, the mesh model includes: a mesh model of the fluid domain and a mesh model of the phase change solid domain;

[0081] Porous media refer to solids containing a large number of pores, with the solid framework permeating the volume space occupied by the porous medium. The pores within a porous medium are extremely small. Generally, the pores in a porous medium are interconnected, or they may be partially connected and partially disconnected. Due to the inherent inhomogeneity, randomness, and complexity of the geometric topology of porous media, their internal permeability characteristics and fluid transport processes are difficult to measure experimentally. Therefore, computer-aided microscopic modeling of porous media can be used to obtain relevant structural parameters through calculation. Seepage refers to the flow of fluid within a porous medium. Seepage phenomena are widely observed in man-made materials and in nature.

[0082] ICEM is a professional CAE preprocessing software that includes functions such as geometry creation, mesh generation, preprocessing condition setting, and post-processing. It has a more prominent advantage in the field of CFD (Computational Fluid Dynamics) mesh generation and is a standard meshing software that works well with fluid dynamics simulation software.

[0083] Specifically, such as Figure 2 As shown, this embodiment combines the geometric characteristics of the porous structure of the porous medium to be studied with ICEM modeling software to establish a mesh model of the pore structure, namely a mesh model of the fluid domain and a mesh model of the phase change solid domain, and sets the boundary conditions of the model according to the actual working conditions such as temperature and pressure.

[0084] Step S200: Construct a multiphase fluid heat and mass transfer mathematical model and embed the multiphase fluid heat and mass transfer mathematical model into Fluent software;

[0085] Fluent is a commercial CFD software package applicable to industries related to fluid dynamics, heat transfer, and chemical reactions. It features rich physical models, advanced numerical methods, and powerful pre- and post-processing capabilities, finding wide application in aerospace, automotive design, oil and gas, and turbine design. Fluent employs a finite volume method based on a fully unstructured mesh and features gradient algorithms based on mesh nodes and mesh cells.

[0086] Specifically, in this embodiment of the invention, a mathematical model for multiphase fluid heat and mass transfer is first constructed, and the mathematical model is then embedded into Fluent software to perform simulation of multiphase fluid heat and mass transfer.

[0087] In one implementation, step S200 specifically includes:

[0088] Step S201: Construct a mathematical model of the chemical reaction to obtain the mass source term;

[0089] Fluent source terms are generally user-defined. Their generation and effect on the flow field are from the inside out. The generation mechanism of the source term needs to be defined by the user according to the actual physical process. It can be a heat source term for self-heating, a mass source term for the generation of chemical reaction substances, a mass source term for the two-phase mass transfer of substances during phase change, a momentum source term for the flow resistance effect of porous media, or a momentum source term for some special media subjected to special forces from outside the flow field, etc.

[0090] Specifically, in this embodiment of the invention, the mass source term is first obtained by constructing a mathematical model of a chemical reaction.

[0091] In one implementation, step S201 specifically includes:

[0092] Step S2011: Obtain the reaction process for phase change to generate gas within the porous medium based on the chemical reaction equation;

[0093] Step S2012: Based on the Arrhenius chemical kinetic model, the formation rate of the reaction products is obtained as follows:

[0094]

[0095] Among them, A r It is a reaction factor, E r It is the activation energy of the reaction, R is the universal gas constant, T is the temperature, and β is the activation energy of the reaction. r It is the temperature index, M r denoted as r, representing the molar molecular mass of the reaction product r.

[0096] Step S2013: Obtain a chemical reaction mathematical model based on the reaction process and the generation rate, and compile the chemical reaction mathematical model to obtain the mass source term.

[0097] Specifically, this embodiment takes the phase change chemical reaction in a porous medium, specifically the decomposition of hydrates, as an example. The reaction process follows the CH4·N h H₂O → CH₄ + 5.75H₂O, where the generated methane gas follows the Peng-Robinson equation. The formation rate of the reaction products follows the Arrhenius chemical kinetic model. Among them, A r =3.75×10 5 m 2 / m 3 , mol / m2 ·Pa·s, E r =81.08×10 3 J. The above mathematical model was implemented and compiled using the C language, and then embedded into the Fluent software as a quality source term.

[0098] Step S202: Use the enthalpy change-porosity method to track the fluid and solid phase interface in the chemical reaction region containing phase change, so as to obtain the momentum source term;

[0099] The porosity φ of the chemical reaction region containing the phase change is determined to be...

[0100] φ=1-α h ,

[0101] Where, α h It is the volume fraction of hydrate in the grid cells of the grid model;

[0102] The enthalpy of the material in the chemical reaction region containing the phase transition is determined to be...

[0103]

[0104] Where h is the visible enthalpy, ΔH is the heat of reaction, and h ref It is the reference enthalpy, T ref This is the reference temperature, C. p It is a constant pressure specific heat;

[0105] The heat of reaction in the chemical reaction region containing the phase change is determined to be...

[0106] ΔH=φΔH d ,

[0107] Where, ΔH d The latent heat of a chemical reaction;

[0108] The flow of the multiphase fluid in the chemical reaction region containing the phase change was determined according to the classical Darcy's law; the momentum source term was determined as follows.

[0109]

[0110] Among them, K e The effective porosity of the chemical reaction region containing the phase change follows the classical Carman-Koseny equation. It is a velocity vector, A pseudo The porous medium constant determines the damping amplitude during the process of the fluid velocity decreasing to 0.

[0111] Step S203: Construct a mathematical model of multiphase fluid seepage and an enthalpy change model of chemical reaction based on the basic equations of the North Face and South, and obtain the energy source term;

[0112] Based on the aforementioned NS fundamental equations, the governing equations for mass conservation, momentum conservation, and energy conservation are obtained as follows:

[0113]

[0114]

[0115]

[0116] Where μ and ρ are the volume average viscosity and density of each phase fluid in the unit grid, and α i , ρ i , Let be the volume fraction, density, and velocity vector of the i-th phase fluid, respectively. It is a velocity vector, m ij It is the mass transport source term from the i-th phase fluid to the j-th phase fluid. S is the acceleration due to gravity. m It is the mass source term caused by the decomposition reaction of hydrates, and H is the enthalpy change of the multiphase fluid;

[0117] Determine the enthalpy change of a multiphase fluid

[0118]

[0119] Among them, H i S is the enthalpy of the i-th phase fluid in the cell grid. E This is an energy source term resulting from the decomposition reaction of hydrates;

[0120] The energy source term is determined to be

[0121] S E =-m r ΔH d ,

[0122] Among them, H d It is the latent heat of a chemical reaction.

[0123] Step S204: Embed the mass source term, the momentum source term, and the energy source term into the Fluent software.

[0124] Specifically, by embedding the compiled mass source term, momentum source term, and energy source term into the Fluent software, numerical simulations of heat and mass transfer in multiphase fluids can be performed.

[0125] Step S300: Assemble the mesh model of the fluid domain and the mesh model of the phase change solid domain, and import them into Fluent software;

[0126] Specifically, if each component is meshed separately, it can be assembled in other meshing software and then imported into Fluent. In this embodiment, the mesh models of the fluid domain and the phase change solid domain of the porous medium pore structure created in ICEM modeling software are assembled and then imported into Fluent software.

[0127] Step S400: Based on the boundary conditions of the mesh model, numerical simulation analysis is performed using Fluent software.

[0128] In one implementation, step S400 specifically includes:

[0129] Step S401: In the Fluent software, define the model interface as interior boundary conditions;

[0130] Step S402: Based on the boundary conditions of the mesh model, set the boundary and computational domain temperature, pressure and flow boundary conditions in the Fluent software;

[0131] Step S403: Numerical simulation analysis of the heat and mass transfer mechanism of multiphase fluids is performed using Fluent software.

[0132] Specifically, in this embodiment of the invention, the mesh models of the divided fluid domain and the phase change solid domain are assembled, and the models are imported into Fluent software. For example... Figure 3 As shown, the model interface is defined as interior boundary conditions, and boundary and computational domain temperature, pressure, and flow boundary conditions are set to conduct a numerical simulation study on the heat and mass transfer mechanism of multiphase fluids containing phase change-chemical reactions in porous media. The fluid and solid particle densities, fluid and thermodynamic parameters used in this embodiment are shown in Table 1.

[0133] Table 1. Fluid and solid particulate property parameters used in the examples

[0134]

[0135]

[0136] This embodiment simulates the kinetic mechanism of phase transition-chemical reaction inside porous media. The obtained curves showing the change in the content of reactants in the phase transition-decomposition reaction over time, and the comparison curves with simulated values ​​from the literature, are shown below. Figure 4 As shown, the evolution of pore structure characteristics was studied, and reactant content and distribution cloud maps at different time steps within the porous medium were obtained, such as... Figure 5 As shown. Real-time acquisition of the multiphase fluid distribution and velocity field within the porous medium yields fluid velocity distribution cloud maps at different time steps within the porous medium, as shown. Figure 6As shown. The temperature field of the multiphase fluid inside the porous medium is obtained, resulting in temperature field distribution cloud maps at different time steps within the porous medium, as shown. Figure 7 As shown. The distribution and permeability evolution curves of each phase are obtained to determine the absolute permeability (K) within the porous medium. N ) and aqueous phase (K Nw The evolution curve of saturation of non-aqueous fluids, as shown in the figure. Figure 8 As shown.

[0137] Step M100: Determine that the porosity of the solid region where no phase change has occurred is 0, and the fluid velocity is 0.

[0138] Specifically, the pasty region where phase change occurs is treated as a porous medium, and the flow of the multiphase fluid follows the classical Darcy law; the porosity of the solid region where phase change does not occur is 0, and the flow velocity of the fluid in this region is 0.

[0139] Exemplary device

[0140] like Figure 9 As shown in the illustration, this embodiment also provides a numerical simulation device for multiphase fluid heat and mass transfer, the device comprising:

[0141] The mesh model and boundary condition acquisition module 10 is used to establish a mesh model of the porous medium pore structure using ICEM modeling software, and to set the boundary conditions of the mesh model according to the actual working conditions.

[0142] The model building module 20 is used to build a multiphase fluid heat and mass transfer mathematical model and embed the multiphase fluid heat and mass transfer mathematical model into Fluent software;

[0143] The mesh model assembly module 30 is used to assemble the mesh model of the fluid domain and the mesh model of the phase change solid domain and import them into Fluent software.

[0144] The simulation analysis module 40 is used to perform numerical simulation analysis using Fluent software based on the boundary conditions of the mesh model.

[0145] In one implementation, the model building module 20 includes:

[0146] The mass source term acquisition unit is used to construct a mathematical model of a chemical reaction in order to obtain the mass source term.

[0147] The momentum source term acquisition unit is used to track the fluid and solid phase interface in a chemical reaction region containing phase change using the enthalpy change-porosity method in order to obtain the momentum source term.

[0148] The energy source term acquisition unit is used to construct a mathematical model of multiphase fluid seepage and an enthalpy change model of chemical reaction based on the basic equations of the North Face and South (NS) to obtain the energy source term.

[0149] The model acquisition unit is used to obtain the multiphase fluid heat and mass transfer mathematical model based on the mass source term, the momentum source term, and the energy source term.

[0150] An embedding unit is used to embed the multiphase fluid heat and mass transfer mathematical model into the Fluent software.

[0151] In one implementation, the quality source item acquisition unit includes:

[0152] A reaction process simulation unit is used to obtain the reaction process of phase change gas generation in the porous medium based on chemical reaction equations.

[0153] The reaction product formation rate acquisition unit is used to obtain the reaction product formation rate based on the Arrhenius chemical kinetic model.

[0154]

[0155] Among them, A r It is a reaction factor, E r It is the activation energy of the reaction, R is the universal gas constant, T is the temperature, and β is the activation energy of the reaction. r It is the temperature index, M r Let r be the molar molecular mass of the reaction product r;

[0156] The mass source term acquisition unit is used to obtain a chemical reaction mathematical model based on the reaction process and the generation rate, and to compile the chemical reaction mathematical model to obtain the mass source term.

[0157] In one implementation, the momentum source term acquisition unit includes:

[0158] A porosity acquisition unit is used to determine the porosity φ of the chemical reaction region containing phase change.

[0159] φ=1-α h ,

[0160] Where, α h It is the volume fraction of hydrate in the grid cells of the grid model;

[0161] The enthalpy simulation unit for materials is used to determine the enthalpy of the material in the chemical reaction region containing the phase transition.

[0162]

[0163] Where h is the visible enthalpy, ΔH is the heat of reaction, and h ref It is the reference enthalpy, T ref This is the reference temperature, C. p It is a constant pressure specific heat;

[0164] The reaction heat simulation unit is used to determine the reaction heat of the chemical reaction region containing the phase change.

[0165] ΔH=φΔH d ,

[0166] Where, ΔH d The latent heat of a chemical reaction;

[0167] The flow simulation unit is used to determine the flow of multiphase fluids in the chemical reaction region containing phase change according to the classical Darcy's law;

[0168] The momentum source term acquisition unit is used to determine the momentum source term as...

[0169]

[0170] Among them, K e The effective porosity of the chemical reaction region containing the phase change follows the classical Carman-Koseny equation. It is a velocity vector, A pseudo It is the porous medium constant, which determines the damping amplitude during the process of fluid velocity dropping to 0.

[0171] In one implementation, the energy source acquisition unit includes:

[0172] The governing equation acquisition unit is used to obtain the governing equations for mass conservation, momentum conservation, and energy conservation based on the NS fundamental equations.

[0173]

[0174]

[0175]

[0176] Where μ and ρ are the volume average viscosity and density of each phase fluid in the unit grid, and α i , ρ i , Let be the volume fraction, density, and velocity vector of the i-th phase fluid, respectively. It is a velocity vector, m ij It is the mass transport source term from the i-th phase fluid to the j-th phase fluid. S is the acceleration due to gravity. m It is the mass source term caused by the decomposition reaction of hydrates, and H is the enthalpy change of the multiphase fluid;

[0177] Enthalpy change acquisition unit, used to determine the enthalpy change of multiphase fluid.

[0178]

[0179] Among them, H i S is the enthalpy of the i-th phase fluid in the cell grid. E This is an energy source term resulting from the decomposition reaction of hydrates;

[0180] Energy source term acquisition unit, used to determine the energy source term as

[0181] S E =-m r ΔH d ,

[0182] Among them, H d It is the latent heat of a chemical reaction.

[0183] In one implementation, the simulation analysis module 40 includes:

[0184] The model interface definition unit is used to define the model interface as the interior boundary condition in the Fluent software.

[0185] The setting unit is used to set the boundary and computational domain temperature, pressure and flow boundary conditions in the Fluent software based on the boundary conditions of the mesh model.

[0186] The numerical simulation analysis unit is used to perform numerical simulation analysis of the heat and mass transfer mechanism of multiphase fluids using Fluent software.

[0187] In one implementation, the apparatus further includes:

[0188] The solid region simulation unit is used to determine that the porosity of the solid region where no phase change has occurred is 0 and the fluid flow rate is 0.

[0189] Based on the above embodiments, the present invention also provides a smart terminal, the principle block diagram of which can be as follows: Figure 10 As shown, the intelligent terminal includes a processor, memory, network interface, display screen, and temperature sensor connected via a system bus. The processor provides computing and control capabilities. The memory includes a non-volatile storage medium and internal memory. The non-volatile storage medium stores the operating system and computer programs. The internal memory provides the environment for the operation of the operating system and computer programs in the non-volatile storage medium. The network interface is used to communicate with external terminals via a network connection. When the computer program is executed by the processor, it implements a multiphase percolation simulation method involving thermal flow solidification coupling in porous media with phase change. The display screen can be an LCD screen or an e-ink screen. The temperature sensor is pre-installed inside the intelligent terminal to detect the operating temperature of internal devices.

[0190] Those skilled in the art will understand that Figure 10 The block diagram shown is merely a partial structural diagram related to the present invention and does not constitute a limitation on the smart terminal to which the present invention is applied. A specific smart terminal may include more or fewer components than those shown in the figure, or combine certain components, or have different component arrangements.

[0191] Those skilled in the art will understand that all or part of the processes in the methods of the above embodiments can be implemented by a computer program instructing related hardware. The computer program can be stored in a non-volatile computer-readable storage medium. When executed, the computer program can include the processes of the embodiments of the above methods. Any references to memory, storage, operational databases, or other media used in the embodiments provided by this invention can include non-volatile and / or volatile memory. Non-volatile memory may include read-only memory (ROM), programmable ROM (PROM), electrically programmable ROM (EPROM), electrically erasable programmable ROM (EEPROM), or flash memory. Volatile memory may include random access memory (RAM) or external cache memory. By way of illustration and not limitation, RAM is available in a variety of forms, such as static RAM (SRAM), dynamic RAM (DRAM), synchronous DRAM (SDRAM), dual operating data rate SDRAM (DDRSDRAM), enhanced SDRAM (ESDRAM), synchronous link DRAM (SLDRAM), RAMbus direct RAM (RDRAM), direct memory bus dynamic RAM (DRDRAM), and memory bus dynamic RAM (RDRAM), etc.

[0192] In summary, this invention discloses a method for simulating multiphase permeation in porous media involving phase change coupled with thermal-fluid-solidification coupling. The method includes: establishing a mesh model of the porous media's pore structure using ICEM modeling software, and setting boundary conditions for the mesh model based on actual operating conditions; constructing a multiphase fluid heat and mass transfer mathematical model, and embedding the multiphase fluid heat and mass transfer mathematical model into Fluent software; assembling the mesh model of the fluid domain and the mesh model of the phase change solid domain, and importing them into Fluent software; and performing numerical simulation analysis using Fluent software based on the boundary conditions of the mesh model. This method can not only study the kinetic mechanism of phase change-chemical reactions within porous media and the evolution of their pore structure characteristics, but also obtain real-time data on the distribution of multiphase fluids, velocity fields, temperature fields, and permeability evolution curves within porous media, showing broad application prospects.

[0193] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for simulating multiphase percolation coupled with thermal flow solidification in porous media containing phase change, characterized in that, The method includes: A mesh model of the porous medium pore structure was established using ICEM modeling software, and the boundary conditions of the mesh model were set according to the actual working conditions; wherein, the mesh model includes: a mesh model of the fluid domain and a mesh model of the phase change solid domain; A mathematical model for heat and mass transfer in multiphase fluids is constructed and embedded into Fluent software. The construction of a multiphase fluid heat and mass transfer mathematical model and the embedding of the multiphase fluid heat and mass transfer mathematical model into Fluent software include: Construct a mathematical model of the chemical reaction to obtain the mass source term; The enthalpy change-porosity method is used to track the fluid and solid phase interfaces in chemical reaction regions involving phase change in order to obtain the momentum source term; Based on the basic equations of the North and South, a mathematical model of multiphase fluid seepage and an enthalpy change model of chemical reaction are constructed to obtain the energy source term; Based on the mass source term, the momentum source term, and the energy source term, the mathematical model for heat and mass transfer in the multiphase fluid is obtained. The multiphase fluid heat and mass transfer mathematical model is embedded into the Fluent software; The method employing enthalpy change-porosity to track the fluid-solid phase interface in a chemical reaction region involving phase change, in order to obtain the momentum source term, includes: Determine the porosity of the chemical reaction region containing the phase change. for ， in, It is the volume fraction of hydrate in the grid cells of the grid model; The enthalpy of the material in the chemical reaction region containing the phase transition is determined to be... ， in, It is enthalpy. It is the heat of reaction. It is the reference enthalpy. This is a reference temperature. It is a constant pressure specific heat; The heat of reaction in the chemical reaction region containing the phase change is determined to be... ， in, The latent heat of a chemical reaction; The flow of the multiphase fluid in the chemical reaction region containing the phase change is determined according to the classical Darcy's law; Determine the momentum source term as ， in, The effective porosity of the chemical reaction region containing the phase change follows the classical Carman-Koseny equation. It is a velocity vector. It is the porous medium constant, which determines the damping amplitude during the process of fluid velocity dropping to 0; The mesh models of the fluid domain and the phase change solid domain are assembled and imported into Fluent software. Numerical simulation analysis was performed using Fluent software based on the boundary conditions of the mesh model.

2. The numerical simulation method for multiphase fluid heat and mass transfer according to claim 1, characterized in that, The construction of a mathematical model for a chemical reaction to obtain mass source terms includes: The reaction process for phase change to generate gas within the porous medium is obtained based on the chemical reaction equation. Based on the Arrhenius chemical kinetic model, the formation rate of the reaction products is as follows: ， in, It is a reaction factor. It is the activation energy of the reaction. It is the universal gas constant. It's temperature. It is a temperature index. The reaction product The molar molecular mass; A mathematical model of the chemical reaction is obtained based on the reaction process and the generation rate, and the mathematical model of the chemical reaction is compiled to obtain the mass source term.

3. The numerical simulation method for multiphase fluid heat and mass transfer according to claim 1, characterized in that, The mathematical model for multiphase fluid seepage established based on the fundamental equations of the North Face and South Face is used to obtain the energy source term, including: Based on the aforementioned NS fundamental equations, the governing equations for mass conservation, momentum conservation, and energy conservation are obtained as follows: ， ， ， in, and It represents the volume average viscosity and density of each phase fluid within a single cell grid. , , For are respectively the first Volume fraction, density, and velocity vector of the phase fluid. It is a velocity vector. It is the first Phase fluid to the first Mass transport source term of phase fluid, It is the acceleration due to gravity. This is a mass source term resulting from the hydrate decomposition reaction. It is the enthalpy change of a multiphase fluid; Determine the enthalpy change of a multiphase fluid ， in, It is the first in the cell mesh Enthalpy of a phase fluid This is an energy source term resulting from the decomposition reaction of hydrates; The energy source term is determined to be ， in, It is the latent heat of a chemical reaction.

4. The method for simulating multiphase percolation coupled with thermal flow solidification in porous media containing phase change according to claim 1, characterized in that, The boundary conditions based on the mesh model are analyzed numerically using Fluent software, including: In the Fluent software, the model interface is defined as the interior boundary condition; Based on the boundary conditions of the mesh model, the boundary and computational domain temperature, pressure and flow boundary conditions are set in the Fluent software; The heat and mass transfer mechanism of multiphase fluids was numerically simulated and analyzed using Fluent software.

5. The method for simulating multiphase percolation coupled with thermal flow solidification in porous media containing phase change according to claim 1, characterized in that, The method further includes: The porosity of the solid region where no phase change has occurred is determined to be 0, and the fluid flow rate is determined to be 0.

6. A multiphase percolation simulation device for porous media with phase change thermal flow solidification coupling, characterized in that, The device includes: The mesh model and boundary condition acquisition module is used to establish a mesh model of the porous structure of the porous medium using ICEM modeling software, and to set the boundary conditions of the mesh model according to the actual working conditions. The model building module is used to build a mathematical model of multiphase fluid heat and mass transfer and embed the mathematical model of multiphase fluid heat and mass transfer into Fluent software; The mesh model assembly module is used to assemble the mesh models of the fluid domain and the phase change solid domain and import them into Fluent software. The simulation analysis module is used to perform numerical simulation analysis using Fluent software based on the boundary conditions of the mesh model. The model building module includes: The mass source term acquisition unit is used to construct a mathematical model of a chemical reaction in order to obtain the mass source term. The momentum source term acquisition unit is used to track the fluid and solid phase interface in a chemical reaction region containing phase change using the enthalpy change-porosity method in order to obtain the momentum source term. The energy source term acquisition unit is used to construct a mathematical model of multiphase fluid seepage and an enthalpy change model of chemical reaction based on the NS basic equations in order to obtain the energy source term. The model acquisition unit is used to obtain the multiphase fluid heat and mass transfer mathematical model based on the mass source term, the momentum source term, and the energy source term. An embedding unit is used to embed the multiphase fluid heat and mass transfer mathematical model into the Fluent software; The momentum source term acquisition unit includes: A porosity acquisition unit is used to determine the porosity of the chemical reaction region containing the phase change. for ， in, It is the volume fraction of hydrate in the grid cells of the grid model; The enthalpy simulation unit for materials is used to determine the enthalpy of the material in the chemical reaction region containing the phase transition. ， in, It is enthalpy. It is the heat of reaction. It is the reference enthalpy. This is a reference temperature. It is a constant pressure specific heat; The reaction heat simulation unit is used to determine the reaction heat of the chemical reaction region containing the phase change. ， in, The latent heat of a chemical reaction; The flow simulation unit is used to determine the flow of multiphase fluids in the chemical reaction region containing phase change according to the classical Darcy's law; The momentum source term acquisition unit is used to determine the momentum source term as... ， in, The effective porosity of the chemical reaction region containing the phase change follows the classical Carman-Koseny equation. It is a velocity vector. It is the porous medium constant, which determines the damping amplitude during the process of fluid velocity dropping to 0.

7. A smart terminal, characterized in that, The intelligent terminal includes a memory, a processor, and a multiphase flow simulation program for porous media with phase change thermal flow solidification coupled with multiphase flow, which is stored in the memory and can run on the processor. When the processor executes the multiphase flow simulation program for porous media with phase change thermal flow solidification coupled with multiphase flow, it implements the steps of the multiphase flow simulation method for porous media with phase change thermal flow solidification coupled with multiphase flow as described in any one of claims 1-5.

8. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores a simulation program for thermal flow solidification coupled multiphase flow of porous media with phase change. When the simulation program is executed by a processor, it implements the steps of the simulation method for thermal flow solidification coupled multiphase flow of porous media with phase change as described in any one of claims 1-5.

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