CN115329616A - Multi-phase seepage simulation method for heat flow solidification coupling of porous medium containing phase change - Google Patents
Multi-phase seepage simulation method for heat flow solidification coupling of porous medium containing phase change Download PDFInfo
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Abstract
The invention discloses a multi-phase seepage simulation method for heat flow solidification coupling of a porous medium containing phase change, which comprises the following steps: establishing a grid model of a porous medium pore structure by using ICEM modeling software, and setting boundary conditions of the grid model according to actual working conditions; constructing a multi-phase fluid heat and mass transfer mathematical model, and embedding the multi-phase fluid heat and mass transfer mathematical model into Fluent software; assembling the grid model of the fluid domain and the grid model of the phase-change solid domain, and introducing the assembled grid models into Fluent software; and carrying out numerical simulation analysis by adopting Fluent software based on the boundary conditions of the grid model. The method can be used for researching a dynamic mechanism of phase change-chemical reaction in the porous medium and a pore structure characteristic evolution rule thereof, and can also be used for acquiring a multi-phase fluid distribution rule, a speed field, a temperature field distribution and each phase permeability evolution curve in the porous medium in real time, so that the method has a wide application prospect.
Description
Technical Field
The invention relates to the field of multiphase fluid seepage, in particular to a phase-change-containing porous medium heat flow solidification coupling multiphase seepage simulation method.
Background
In engineering practices such as natural gas hydrate exploitation, carbonate oil and gas reservoir acidizing fracturing, CO2 geological storage, prediction and treatment of underground pollutant migration and the like, dynamic coupling problems such as stratum pore blocking or expansion, multiphase fluid seepage and the like caused by chemical reaction products are often encountered, and in addition, the complexity and the opacity of the pore structure characteristics of the natural porous medium cause various engineering problems. Although the engineering geological and hydrogeological conditions (reservoir conditions), engineering performance and engineering conditions of the engineering difficult problems are different, the engineering difficult problems are essentially a complex phase change, a dynamic boundary, chemical kinetics and a porous medium heat and mass transfer problem with mutual coupling of multi-phase fluid seepage.
The existing simulation method usually simplifies chemical reaction products into a multi-component transportation process in a single-phase fluid, and ignores a seepage mechanism of a multi-phase fluid; in addition, a pixel volume method (VOP) adopted in the phase change process in the chemical reaction is converted into a fluid node only after the solid reaction on the calculation node is complete, and the real-time evolution characteristic of the phase change chemical reaction on the porous medium pore structure cannot be reflected.
Accordingly, the prior art is yet to be improved and developed.
Disclosure of Invention
The technical problem to be solved by the present invention is to provide a method for simulating multi-phase seepage by coupling thermal flow solidification of a porous medium containing phase change, aiming at solving the problems in the prior art that the seepage mechanism of a multi-phase fluid is neglected and the real-time evolution characteristics of the phase change chemical reaction on the pore structure of the porous medium cannot be reflected.
The technical scheme adopted by the invention for solving the technical problem is as follows:
in a first aspect, the invention provides a method for simulating heat flow solidification coupling multiphase seepage of a porous medium containing phase change, which is characterized by comprising the following steps:
establishing a grid model of a porous medium pore structure by using ICEM modeling software, and setting boundary conditions of the grid model according to actual working conditions; wherein the mesh model comprises: a mesh model of the fluid domain and a mesh model of the phase-change solid domain;
constructing a multi-phase fluid heat and mass transfer mathematical model, and embedding the multi-phase 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 introducing the assembled mesh models into Fluent software;
and carrying out numerical simulation analysis by adopting Fluent software based on the boundary condition of the grid model.
In one implementation, the constructing and embedding the multi-phase fluid heat and mass transfer mathematical model into Fluent software includes:
constructing a chemical reaction mathematical model to obtain a quality source item;
tracking the interface of a fluid phase and a solid phase in a chemical reaction area containing phase change by adopting an enthalpy change-porosity method to obtain a momentum source item;
constructing a multiphase fluid seepage mathematical model and an enthalpy change model of chemical reaction based on an NS basic equation set to obtain an energy source term;
obtaining the heat and mass transfer mathematical model of the multi-phase fluid based on the mass source term, the momentum source term and the energy source term;
embedding the multi-phase fluid heat and mass transfer mathematical model into the Fluent software.
In one implementation, the constructing a mathematical model of a chemical reaction to derive a source of mass term includes:
obtaining a reaction process of the phase-change generated gas in the porous medium based on a chemical reaction equation;
the generation rate of the reaction product obtained based on the Arrhenius chemical kinetics model is
Wherein, A r Is a reaction factor, E r Is the activation energy of the reaction, R is the universal gas constant, T is the temperature, beta r Is a temperature index, M r Is the molar mass of the reaction product r;
and obtaining a chemical reaction mathematical model according to the reaction process and the generation rate, and compiling the chemical reaction mathematical model to obtain the quality source item.
In one implementation, the tracing of fluid and solid phase interfaces of a chemical reaction zone containing a phase change using an enthalpy change-porosity method to obtain a momentum source term, comprises:
determining the porosity phi of the chemical reaction zone containing the phase change to be
φ＝1-α h ，
Wherein alpha is h Is the volume fraction of hydrates in the grid cells in the grid model;
determining the enthalpy of the material of the chemical reaction zone containing the phase change to
Wherein H is sensible enthalpy,. DELTA.H is heat of reaction, H ref Is the reference enthalpy, T ref Is a reference temperature, C p Is constant pressure specific heat;
determining the heat of reaction of the chemical reaction zone containing the phase change as
ΔH＝φΔH d ，
Wherein, Δ H d Is the latent heat of chemical reaction;
determining the flow of the multiphase fluid containing the phase-change chemical reaction region according to classical Darcy's law;
determining the momentum source term as
Wherein, K e To be an effective porosity of the chemical reaction region containing the phase transition, the classical Carman-Koseny equation was followed,
is a velocity vector, A pseudo Is the porous medium constant and determines the damping amplitude during the fluid velocity drop to 0.
In one implementation, the establishing a mathematical model of multiphase fluid seepage based on NS fundamental equations to derive an energy source term includes:
based on the NS basic equation set, the control equations of conservation of mass, conservation of momentum and conservation of energy are obtained in turn
Where μ and ρ are the volume average values of the viscosity and density of the respective phase fluids in the cell grid, α i ，ρ i ，
Volume fraction, density and velocity vector of the ith phase fluid respectively,
is a velocity vector, m ij Is the source term of mass transfer from the ith phase fluid to the jth phase fluid,
as acceleration of gravity, S m Is a mass source term due to hydrate decomposition reactions, and H is the enthalpy change of the multiphase fluid;
determining an enthalpy change of a multiphase fluid as
Wherein H i Is the enthalpy, S, of the ith phase fluid in the cell grid E Is an energy source term due to the decomposition reaction of the hydrate;
determining the energy source term as
S E ＝-m r ΔH d ，
Wherein H d Is the latent heat of chemical reaction.
In one implementation, the performing, based on the boundary conditions of the mesh model, a numerical simulation analysis using Fluent software includes:
defining a model interface as an interface boundary condition in the Fluent software;
setting boundary and calculating domain temperature, pressure and flow boundary conditions in the Fluent software based on the boundary conditions of the grid model;
and (3) carrying out numerical simulation analysis on the heat and mass transfer mechanism of the multi-phase fluid by adopting Fluent software.
In one implementation, the method further comprises:
the porosity of the solid region where no phase change occurred was determined to be 0, and the flow rate of the fluid was determined to be 0.
In a second aspect, the invention provides a heat flow solidification coupled multiphase seepage simulation device for a porous medium containing phase change, which is characterized by comprising:
the system comprises a grid model and boundary condition acquisition module, a data acquisition module and a data acquisition module, wherein the grid model and the boundary condition acquisition module are used for establishing a grid model of a porous medium pore structure by adopting ICEM modeling software and setting the boundary condition of the grid model according to the actual working condition;
the model building module is used for building a multi-phase fluid heat and mass transfer mathematical model and embedding the multi-phase fluid heat and mass transfer mathematical model into Fluent software;
the grid model assembling module is used for assembling the grid model of the fluid domain and the grid model of the phase-change solid domain and guiding the assembled grid models into Fluent software;
and the simulation analysis module is used for carrying out numerical simulation analysis by adopting Fluent software based on the boundary condition of the grid model.
In a third aspect, the present invention provides an intelligent terminal, which is characterized in that the intelligent terminal includes a memory, a processor and a numerical simulation program for multi-phase fluid heat and mass transfer, which is stored in the memory and is operable on the processor, and when the processor executes the phase-change-containing porous medium heat flow solidification coupling multi-phase seepage simulation program, the steps of the phase-change-containing porous medium heat flow solidification coupling multi-phase seepage simulation method as described in any one of the above are implemented.
In a fourth aspect, the present invention provides a computer-readable storage medium, where a porous medium heat flow solidification coupling multi-phase seepage simulation program containing a phase change is stored on the computer-readable storage medium, and when the porous medium heat flow solidification coupling multi-phase seepage simulation program containing the phase change is executed by a processor, the steps of the porous medium heat flow solidification coupling multi-phase seepage simulation method containing the phase change as described in any one of the above are implemented.
Has the beneficial effects that: compared with the prior art, the invention provides a heat flow solidification coupling multiphase seepage simulation method for porous media containing phase change, which comprises the steps of firstly, establishing a grid model of a porous media pore structure by using ICEM modeling software, setting boundary conditions of the grid model according to actual working conditions, then establishing a multiphase fluid heat and mass transfer mathematical model, embedding the multiphase fluid heat and mass transfer mathematical model into Fluent software, then assembling the grid model of a fluid domain and the grid model of a phase change solid domain, introducing the assembled grid model into Fluent software, and finally, carrying out numerical simulation analysis by using Fluent software based on the boundary conditions of the grid model. The method can be used for researching the dynamic mechanism of the phase change-chemical reaction in the porous medium and the evolution rule of the pore structure characteristics of the dynamic mechanism, and can also be used for acquiring the distribution rule, the velocity field, the temperature field distribution and the evolution curve of the permeability of each phase in the porous medium in real time, so that the application prospect is wide.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the embodiments or the description of the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments described in the present invention, and it is also possible for those skilled in the art to obtain other drawings based on the drawings without creative efforts.
FIG. 1 is a flow chart of a method for simulating heat flow solidification coupled multiphase seepage of a porous medium containing phase change according to an embodiment of the present invention.
FIG. 2 is a diagram of a porous medium pore grid model and boundary conditions provided by an embodiment of the present invention.
FIG. 3 is a phase equilibrium curve of decomposition reaction and an exemplary graph of initial-simulated temperature and pressure conditions for a computational domain of porous media provided by an embodiment of the present invention.
FIG. 4 is a graph showing the time-dependent change of the contents of the reactants in the phase change-decomposition reaction according to the embodiment of the present invention, and a comparison graph with a literature simulation value.
FIG. 5 is a cloud of the concentration and distribution of reactants at different time steps within a porous media according to an embodiment of the present invention.
FIG. 6 is a cloud of fluid velocity profiles at different time steps within a porous medium, according to an embodiment of the present invention.
FIG. 7 is a cloud graph of temperature field distributions at different time steps within a porous medium according to an embodiment of the present invention.
FIG. 8 is a graph of absolute permeability (K) in porous media provided by an embodiment of the present invention N ) And an aqueous phase (K) Nw ) Evolution curve with non-aqueous phase fluid saturation.
Fig. 9 is a schematic block diagram of a numerical simulation apparatus for mass and heat transfer of a multiphase fluid according to an embodiment of the present invention.
Fig. 10 is a schematic block diagram of an internal structure of an intelligent terminal according to an embodiment of the present invention.
Detailed Description
In order to make the objects, technical solutions and effects of the present invention clearer and clearer, the present invention is further described in detail below with reference to the accompanying drawings and examples. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
In natural gas hydrate exploitation, carbonate oil and gas reservoir acid fracturing, CO 2 In engineering practices such as geological sequestration, prediction and treatment of underground pollutant migration and the like, dynamic coupling problems such as stratum pore blockage or expansion, multiphase fluid seepage and the like caused by chemical reaction products are often encountered, and in addition, the complexity and the opacity of the pore structure characteristics of a natural porous medium cause various engineering problems. Although the engineering geological and hydrogeological conditions (reservoir conditions), engineering performance and engineering conditions of the engineering difficult problems are different, the engineering difficult problems are essentially a complex phase change, a dynamic boundary, chemical kinetics and a porous medium heat and mass transfer problem with mutual coupling of multi-phase fluid seepage. The existing simulation method usually simplifies chemical reaction products into a multi-component transportation process in a single-phase fluid, and ignores a seepage mechanism of a multi-phase fluid; in addition, a pixel volume method (VOP) adopted in the phase change process in the chemical reaction is converted into a fluid node only after the solid reaction on the calculation node is complete, and the real-time evolution characteristic of the phase change chemical reaction on the porous medium pore structure cannot be reflected.
Therefore, in order to solve the above problems, the present embodiment provides a method for simulating multi-phase seepage by solidifying heat flow of a porous medium containing phase change. By the method, not only can the dynamic mechanism of the phase change-chemical reaction in the porous medium and the evolution rule of the pore structure characteristic be researched, but also the distribution rule of the multi-phase fluid, the velocity field, the temperature field distribution and the permeability evolution curve of each phase in the porous medium can be obtained in real time. In specific implementation, the embodiment firstly adopts ICEM modeling software to establish a grid model of a porous medium pore structure, and sets boundary conditions of the grid model according to actual working conditions. And then, establishing a multi-phase fluid heat and mass transfer mathematical model, embedding the multi-phase fluid heat and mass transfer mathematical model into Fluent software, assembling the grid model of the fluid domain and the grid model of the phase-change solid domain, and introducing the assembled grid models into Fluent software. And finally, performing numerical simulation analysis by adopting Fluent software based on the boundary conditions of the grid model. In this way, simulation of the kinetic mechanism of the phase transition-chemical reaction inside the porous medium can be achieved.
Exemplary method
The embodiment provides a multi-phase seepage simulation method for solidification coupling of heat flow of a porous medium containing phase change. As shown in fig. 1, the method comprises the steps of:
s100, establishing a grid model of a porous medium pore structure by using ICEM modeling software, and setting boundary conditions of the grid model according to actual working conditions; wherein the mesh model comprises: a mesh model of the fluid domain and a mesh model of the phase-change solid domain;
porous media refers to solids that contain a large number of voids within, with the solid framework spanning the volume space occupied by the porous media. The voids within the porous media are extremely small. Generally, the voids of the porous medium are communicated, or may be partially communicated or partially not communicated. Due to the non-uniformity, randomness and complexity of geometric topological structure of the porous medium, the internal permeability characteristics, the fluid transfer process and the like of the porous medium are difficult to measure. Therefore, the computer can be used for micro-modeling the porous medium and obtaining relevant construction parameters of the porous medium through calculation. Seepage refers to the flow of fluid within a porous medium. Seepage phenomena occur widely in man-made materials and in nature.
The ICEM is a professional CAE preprocessing software, comprises functions of geometric creation, grid division, preprocessing condition setting, post-processing and the like, has more remarkable advantages in the field of CFD (Computational Fluid Dynamics) grid generation, and is standard grid software which is better matched with Fluid mechanics simulation software.
Specifically, as shown in fig. 2, in this embodiment, a mesh model of a pore structure is established by combining geometric characteristics of a pore structure of a porous medium to be researched and by combining an ICEM modeling software, the mesh model is a mesh model of a fluid domain and a mesh model of a phase-change solid domain, and boundary conditions of the models are set according to conditions such as temperature and pressure of an actual working condition.
S200, constructing a multi-phase fluid heat and mass transfer mathematical model, and embedding the multi-phase fluid heat and mass transfer mathematical model into Fluent software;
fluent is a commercially available CFD software package and is used by industries related to fluids, heat transfer, and chemical reactions. The method has rich physical models, advanced numerical methods and strong pre-and post-processing functions, and is widely applied to the aspects of aerospace, automobile design, petroleum and natural gas design, turbine design and the like. Fluent software employs a finite volume method based on a completely unstructured grid, and has a gradient algorithm based on grid nodes and grid cells.
Specifically, the embodiment of the invention firstly constructs a mathematical model of the heat and mass transfer of the multi-phase fluid, and embeds the mathematical model into Fluent software to carry out the simulation and simulation of the heat and mass transfer of the multi-phase fluid.
In an implementation manner, the step S200 specifically includes:
step S201, constructing a chemical reaction mathematical model to obtain a quality source item;
the Fluent source item is generally generated by user self-definition, the generation of the Fluent source item and the action on the flow field are from inside to outside, and the generation mechanism of the source item needs to be defined by a user according to the actual physical process, and can be a self-heating heat source item, a mass source item generated by chemical reaction substances, a mass source item of two-phase mass transfer of substance phase change, a momentum source item of the flow blocking effect of a porous medium, or momentum source items of special media subjected to special force from outside the flow field, and the like.
Specifically, in the embodiment of the present invention, a mass source term is obtained by constructing a mathematical model of a chemical reaction.
In one implementation manner, the step S201 specifically includes:
step S2011, obtaining a reaction process of phase change generated gas in the porous medium based on a chemical reaction equation;
step S2012, obtaining the generation rate of the reaction product based on the Arrhenius chemical kinetic model
Wherein, A r Is a reaction factor, E r Is the activation energy of the reaction, R is the universal gas constant, T is the temperature, beta r Is a temperature index, M r Is the molar mass of the reaction product r.
And S2013, obtaining a chemical reaction mathematical model according to the reaction process and the generation rate, and compiling the chemical reaction mathematical model to obtain the quality source item.
Specifically, in the embodiment, the phase change chemical reaction in the porous medium is exemplified by the decomposition of hydrate, and the reaction process follows CH 4 ·N h H 2 O→CH 4 +5.75H 2 O, wherein the methane gas produced follows the Peng-Robinson equation. The rate of formation of the reaction product follows the Arrhenius chemical kinetics model:
wherein A is r ＝3.75×10 5 m 2 /m 3 ，
mol/m 2 ·Pa·s，E r ＝81.08×10 3 J. The above mathematical model is compiled by C language, and is embedded into Fluent software in the form of quality source item.
S202, tracking a fluid and solid phase interface of a chemical reaction area containing phase change by adopting an enthalpy change-porosity method to obtain a momentum source item;
determining the porosity phi of the chemical reaction zone containing the phase change to
φ＝1-α h ，
Wherein alpha is h Is the volume fraction of hydrates in the grid cells in the grid model;
determining the enthalpy of the material of the chemical reaction zone containing the phase change to
Wherein H is sensible enthalpy,. DELTA.H is heat of reaction, H ref Is a reference enthalpy, T ref Is a reference temperature, C p Is constant pressure specific heat;
determining the heat of reaction of the chemical reaction zone containing the phase change as
ΔH＝φΔH d ，
Wherein, Δ H d Latent heat of chemical reaction;
determining the flow of the multiphase fluid containing the phase-changed chemical reaction region according to classical Darcy's law; determining the momentum source term as
Wherein, K e To be an effective porosity of the chemical reaction region containing the phase transition, the classical Carman-Koseny equation was followed,
is a velocity vector, A pseudo Is a porous medium constant, and determines the damping amplitude of the fluid in the process of reducing the velocity to 0
S203, constructing a multiphase fluid seepage mathematical model and an enthalpy change model of chemical reaction based on an NS basic equation set, and obtaining an energy source item;
based on the NS fundamental equation set, obtaining control equations of conservation of mass, conservation of momentum and conservation of energy in sequence as
Where μ and ρ are the volume average values of the viscosity and density of the respective phase fluids in the cell grid, α i ，ρ i ，
Volume fraction, density and velocity vector of the ith phase fluid respectively,
is a velocity vector, m ij Is the source term of mass transfer from the ith phase fluid to the jth phase fluid,
as acceleration of gravity, S m Is a mass source term due to hydrate decomposition reactions, and H is the enthalpy change of the multiphase fluid;
determining an enthalpy change of a multiphase fluid as
Wherein H i Is the enthalpy of the ith phase fluid in the cell grid, S E Due to hydrate decompositionEnergy source terms caused by the reaction;
determining the energy source term as
S E ＝-m r ΔH d ，
Wherein H d Is the latent heat of chemical reaction.
And S204, embedding the mass source item, the momentum source item and the energy source item into the Fluent software.
Specifically, the mass source item, the momentum source item and the energy source item which are obtained by compiling are embedded into the Fluent software, and numerical simulation can be carried out on the heat and mass transfer of the multi-phase fluid.
Step S300, assembling the grid model of the fluid domain and the grid model of the phase-change solid domain, and importing the assembled grid models into Fluent software;
specifically, if each component is separately meshed, the import Fluent can be assembled in other mesh software. In this embodiment, the mesh model of the fluid domain of the porous medium pore structure and the mesh model of the phase-change solid domain, which are established in the ICEM modeling software, are assembled and then introduced into the Fluent software.
And S400, performing numerical simulation analysis by adopting Fluent software based on the boundary condition of the grid model.
In one implementation, the step S400 specifically includes:
step S401, defining a model interface as an interface boundary condition in the Fluent software;
step S402, setting boundary and calculating domain temperature, pressure and flow boundary conditions in Fluent software based on the boundary conditions of the grid model;
and S403, performing numerical simulation analysis on the heat and mass transfer mechanism of the multiphase fluid by adopting Fluent software.
Specifically, the embodiment of the invention assembles the divided mesh models of the fluid domain mesh and the phase-change solid domain, and introduces the models into Fluent software. As shown in fig. 3, the model interface is defined as the interface boundary condition, the boundary and the calculated domain temperature, pressure and flow boundary conditions are set, and a numerical simulation study is performed on the heat and mass transfer mechanism of the multi-phase fluid containing the phase change-chemical reaction in the porous medium. The fluid and solid particle densities, fluid and thermodynamic parameters used in this example are shown in table 1.
TABLE 1 table of the physical properties of the fluids and solids used in the examples
In this example, the kinetic mechanism of the phase transition-chemical reaction inside the porous medium is simulated, and the obtained curve of the content of the phase transition-decomposition reaction reactant with time and the comparison curve with the literature simulation value are shown in fig. 4. And (3) researching the evolution rule of pore structure characteristics to obtain the reactant content and distribution cloud charts of the porous medium at different time steps, as shown in figure 5. The distribution rule and the velocity field of the multi-phase fluid in the porous medium are obtained in real time, and fluid velocity distribution cloud charts of different time steps in the porous medium are obtained, as shown in fig. 6. And acquiring the temperature field of the multiphase fluid in the porous medium to obtain temperature field distribution cloud charts of different time steps in the porous medium, as shown in fig. 7. Obtaining the distribution and each phase permeability evolution curve to obtain the absolute permeability (K) in the porous medium N ) And an aqueous phase (K) Nw ) The evolution curve with the saturation of the fluid in the non-aqueous phase is shown in fig. 8.
Step M100, determining that the porosity of the solid region without phase change is 0, and the flow rate of the fluid is 0.
Specifically, the pasty region where the phase change occurs is regarded as a porous medium, and the flow of the multiphase fluid follows the classic darcy law; the porosity of the solid region where no phase change occurred was 0, and the flow rate of the fluid in this region was 0.
Exemplary devices
As shown in fig. 9, the present embodiment also provides a numerical simulation apparatus for heat and mass transfer of a multiphase fluid, the apparatus comprising:
the grid model and boundary condition acquisition module 10 is used for establishing a grid model of a porous medium pore structure by using ICEM modeling software and setting boundary conditions of the grid model according to actual working conditions;
the model building module 20 is used for building a multi-phase fluid heat and mass transfer mathematical model and embedding the multi-phase fluid heat and mass transfer mathematical model into Fluent software;
the grid model assembling module 30 is used for assembling the grid model of the fluid domain and the grid model of the phase-change solid domain and guiding the assembled grid models into Fluent software;
and the simulation analysis module 40 is used for performing numerical simulation analysis by adopting Fluent software based on the boundary conditions of the grid model.
In one implementation, the model building module 20 includes:
the quality source item acquisition unit is used for constructing a chemical reaction mathematical model to obtain a quality source item;
the momentum source item acquisition unit is used for realizing the interface tracking of a fluid phase and a solid phase in a chemical reaction area containing phase change by adopting an enthalpy change-porosity method so as to obtain a momentum source item;
the system comprises an energy source item acquisition unit, a data processing unit and a data processing unit, wherein the energy source item acquisition unit is used for constructing a multiphase fluid seepage mathematical model and an enthalpy change model of chemical reaction based on an NS basic equation set so as to obtain an energy source item;
the model acquisition unit is used for obtaining the heat and mass transfer mathematical model of the multiphase fluid based on the mass source item, the momentum source item and the energy source item;
and the embedding unit is used for embedding the multi-phase fluid heat and mass transfer mathematical model into the Fluent software.
In one implementation, the quality source item obtaining unit includes:
the reaction process simulation unit is used for obtaining the reaction process of the phase change generated gas in the porous medium based on a chemical reaction equation;
a generation rate obtaining unit of the reaction product, which is used for obtaining the generation rate of the reaction product based on the Arrhenius chemical kinetic model
Wherein, A r Is a reaction factor, E r Is the activation energy of the reaction, R is the universal gas constant, T is the temperature, beta r Is a temperature index, M r Is the molar mass of the reaction product r;
and the quality source item acquisition unit is used for obtaining a chemical reaction mathematical model according to the reaction process and the generation rate, and compiling the chemical reaction mathematical model to obtain the quality source item.
In one implementation, the momentum source item acquiring unit includes:
a porosity obtaining unit for determining a porosity φ of the chemical reaction region containing the phase transition to
φ＝1-α h ，
Wherein alpha is h Is the volume fraction of hydrates in the grid cells in the grid model;
an enthalpy simulation unit of the material for determining the enthalpy of the material containing the phase-changed chemical reaction region as
Wherein H is sensible enthalpy,. DELTA.H is heat of reaction, H ref Is the reference enthalpy, T ref Is a reference temperature, C p Is constant pressure specific heat;
a reaction heat simulation unit for determining the reaction heat of the chemical reaction region containing the phase change
ΔH＝φΔH d ，
Wherein, Δ H d Latent heat of chemical reaction;
a flow simulation unit for determining a flow of the multiphase fluid including the phase-change chemical reaction region according to a classic darcy's law;
a momentum source item acquisition unit for determining momentum source items as
Wherein, K e To be an effective porosity of the chemical reaction region containing the phase transition, the classical Carman-Koseny equation was followed,
is a velocity vector, A pseudo Is the porous medium constant and determines the damping amplitude during the fluid velocity drop to 0.
In one implementation, the energy source item acquisition unit includes:
a control equation obtaining unit for obtaining control equations of conservation of mass, conservation of momentum and conservation of energy based on the NS fundamental equation set
Wherein mu and rho are volume average values of viscosity and density of each phase fluid in the cell grid, alpha i ，ρ i ，
Volume fraction, density and velocity vector of the ith phase fluid respectively,
is a velocity vector, m ij Is the source term of mass transfer from the ith phase fluid to the jth phase fluid,
as acceleration of gravity, S m Is a mass source term due to hydrate decomposition reactions, and H is the enthalpy change of the multiphase fluid;
an enthalpy change acquisition unit for determining an enthalpy change of the multiphase fluid as
Wherein H i Is the enthalpy of the ith phase fluid in the cell grid, S E Is an energy source term due to hydrate decomposition reaction;
an energy source item acquisition unit for determining the energy source item as
S E ＝-m r ΔH d ，
Wherein H d Is the latent heat of chemical reaction.
In one implementation, the simulation analysis module 40 includes:
the model interface definition unit is used for defining a model interface as an interface boundary condition in the Fluent software;
the setting unit is used for setting boundary and calculation domain temperature, pressure and flow boundary conditions in the Fluent software based on the boundary conditions of the grid model;
and the numerical simulation analysis unit is used for carrying out numerical simulation analysis on the heat and mass transfer mechanism of the multiphase fluid by adopting Fluent software.
In one implementation, the apparatus further comprises:
and the solid area simulation unit is used for determining that the porosity of the solid area without phase change is 0 and the flow rate of the fluid is 0.
Based on the above embodiments, the present invention further provides an intelligent terminal, and a schematic block diagram thereof may be as shown in fig. 10. The intelligent terminal comprises a processor, a memory, a network interface, a display screen and a temperature sensor which are connected through a system bus. Wherein, the processor of the intelligent terminal is used for providing calculation and control capability. The memory of the intelligent terminal comprises a nonvolatile storage medium and an internal memory. The non-volatile storage medium stores an operating system and a computer program. The internal memory provides an environment for the operating system and the computer program to run on the non-volatile storage medium. The network interface of the intelligent terminal is used for being connected and communicated with an external terminal through a network. The computer program is executed by a processor to realize a multi-phase seepage simulation method for heat flow solidification coupling of the porous medium containing phase change. The display screen of the intelligent terminal can be a liquid crystal display screen or an electronic ink display screen, and the temperature sensor of the intelligent terminal is arranged inside the intelligent terminal in advance and used for detecting the operating temperature of internal equipment.
It will be understood by those skilled in the art that the block diagram of fig. 10 is only a block diagram of a portion of the structure associated with the inventive arrangements, and does not limit the intelligent terminal to which the inventive arrangements are applied, as a particular intelligent terminal may include more or less components than those shown, or may combine certain components, or have a different arrangement of components.
It will be understood by those skilled in the art that all or part of the processes of the methods of the embodiments described above may be implemented by hardware instructions of a computer program, which may be stored in a non-volatile computer-readable storage medium, and when executed, may include the processes of the embodiments of the methods described above. Any reference to memory, storage, operational databases, or other media used in embodiments provided herein may include non-volatile and/or volatile memory. Non-volatile memory can include read-only memory (ROM), programmable ROM (PROM), electrically Programmable ROM (EPROM), electrically Erasable Programmable ROM (EEPROM), or flash memory. Volatile memory can 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), double-rate SDRAM (DDRSDRAM), enhanced SDRAM (ESDRAM), synchronous Link DRAM (SLDRAM), rambus (Rambus) direct RAM (RDRAM), direct Rambus Dynamic RAM (DRDRAM), and Rambus Dynamic RAM (RDRAM).
In summary, the invention discloses a method for simulating multi-phase seepage coupled with heat flow solidification of a porous medium containing phase change, which comprises the following steps: establishing a grid model of a porous medium pore structure by using ICEM modeling software, and setting boundary conditions of the grid model according to actual working conditions; constructing a multi-phase fluid heat and mass transfer mathematical model, and embedding the multi-phase fluid heat and mass transfer mathematical model into Fluent software; assembling the grid model of the fluid domain and the grid model of the phase-change solid domain, and introducing the assembled grid models into Fluent software; and carrying out numerical simulation analysis by adopting Fluent software based on the boundary condition of the grid model. The method can be used for researching a dynamic mechanism of phase change-chemical reaction in the porous medium and a pore structure characteristic evolution rule thereof, and can also be used for acquiring a multi-phase fluid distribution rule, a speed field, a temperature field distribution and each phase permeability evolution curve in the porous medium in real time, so that the method has a wide application prospect.
Finally, it should be noted that: the above examples are only intended to illustrate the technical solution of the present invention, but not to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions of the embodiments of the present invention.
Claims (10)
1. A heat flow solidification coupling multiphase seepage simulation method for a porous medium containing phase change is characterized by comprising the following steps:
establishing a grid model of a porous medium pore structure by using ICEM modeling software, and setting boundary conditions of the grid model according to actual working conditions; wherein the mesh model comprises: a mesh model of the fluid domain and a mesh model of the phase-change solid domain;
constructing a multi-phase fluid heat and mass transfer mathematical model, and embedding the multi-phase 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 introducing the assembled mesh models into Fluent software;
and carrying out numerical simulation analysis by adopting Fluent software based on the boundary condition of the grid model.
2. The method for simulating heat flow solidification coupling multiphase seepage flow of the porous medium containing the phase change according to claim 1, wherein the step of constructing a mathematical model of heat and mass transfer of the multiphase fluid and the step of embedding the mathematical model of heat and mass transfer of the phase fluid into Fluent software comprises the following steps:
constructing a chemical reaction mathematical model to obtain a quality source item;
tracking the interface of a fluid phase and a solid phase in a chemical reaction area containing phase change by adopting an enthalpy change-porosity method to obtain a momentum source item;
constructing a multiphase fluid seepage mathematical model and an enthalpy change model of chemical reaction based on an NS basic equation set to obtain an energy source term;
obtaining the heat and mass transfer mathematical model of the multi-phase fluid based on the mass source term, the momentum source term and the energy source term;
embedding the multi-phase fluid heat and mass transfer mathematical model into the Fluent software.
3. A method for numerical simulation of mass and heat transfer in a multi-phase fluid as set forth in claim 2, wherein the constructing a mathematical model of chemical reactions to derive a mass source term comprises:
obtaining a reaction process of phase-change generated gas in the porous medium based on a chemical reaction equation;
based on the Arrhenius chemical kinetics model, the generation rate of the reaction product is
Wherein A is r Is a reaction factor, E r Is the activation energy of the reaction, R is the universal gas constant, T is the temperature, beta r Is a temperature index, M r Is the molar mass of the reaction product r;
and obtaining a chemical reaction mathematical model according to the reaction process and the generation rate, and compiling the chemical reaction mathematical model to obtain the quality source item.
4. A method for numerical simulation of mass and heat transfer of a multiphase fluid as recited in claim 3 wherein said tracing of the fluid and solid phase interface of the chemical reaction zone containing the phase change using an enthalpy change-porosity method to obtain momentum source terms comprises:
determining the porosity phi of the chemical reaction zone containing the phase change to
φ＝1-α h ，
Wherein alpha is h Is the volume fraction of hydrates in the grid cells in the grid model;
determining the enthalpy of the material of the chemical reaction zone containing the phase change to
Wherein H is sensible enthalpy,. DELTA.H is heat of reaction, H ref Is a reference enthalpy, T ref Is a reference temperature, C p Is constant pressure specific heat;
determining the heat of reaction of the chemical reaction zone containing the phase change as
ΔH＝φΔH d ，
Wherein, Δ H d Is the latent heat of chemical reaction;
determining the flow of the multiphase fluid containing the phase-change chemical reaction region according to classical Darcy's law;
determining a momentum source term of
Wherein, K e To be the effective porosity of the chemical reaction zone containing the phase transition, following the classical Carman-Koseny equation,
is a velocity vector, A pseudo Is the porous medium constant and determines the damping amplitude during the fluid velocity drop to 0.
5. The method of claim 4, wherein the establishing a mathematical model of multi-phase fluid seepage based on the NS fundamental equation set to obtain an energy source term comprises:
based on the NS fundamental equation set, obtaining control equations of conservation of mass, conservation of momentum and conservation of energy in sequence as
Where μ and ρ are the volume average values of the viscosity and density of the respective phase fluids in the cell grid, α i ，ρ i ，
Volume fraction, density and velocity vector of the ith phase fluid respectively,
is a velocity vector, m ij Is the source term of mass transfer from the ith phase fluid to the jth phase fluid,
as acceleration of gravity, S m Is a mass source term due to hydrate decomposition reactions, and H is the enthalpy change of the multiphase fluid;
determining an enthalpy change of a multiphase fluid as
Wherein H i Is the enthalpy of the ith phase fluid in the cell grid, S E Is an energy source term due to hydrate decomposition reaction;
determining the energy source term as
S E ＝-m r ΔH d ，
Wherein H d Is the latent heat of chemical reaction.
6. The method for simulating heat flow solidification coupling multiphase seepage of the porous medium containing phase change according to claim 1, wherein numerical simulation analysis is performed by adopting Fluent software based on the boundary conditions of the grid model, and the method comprises the following steps:
defining a model interface as an interface boundary condition in the Fluent software;
setting boundary and calculating domain temperature, pressure and flow boundary conditions in the Fluent software based on the boundary conditions of the grid model;
and (3) performing numerical simulation analysis on the heat and mass transfer mechanism of the multiphase fluid by adopting Fluent software.
7. The method for simulating heat flow solidification coupled multiphase seepage of a porous medium containing phase change according to claim 4, further comprising:
the porosity of the solid region where no phase change occurred was determined to be 0, and the flow rate of the fluid was determined to be 0.
8. A heat flow solidification coupled multiphase seepage simulation device for a porous medium containing phase change is characterized by comprising:
the system comprises a grid model and boundary condition acquisition module, a data acquisition module and a data processing module, wherein the grid model and the boundary condition acquisition module are used for establishing a grid model of a porous medium pore structure by using ICEM modeling software and setting the boundary condition of the grid model according to the actual working condition;
the model building module is used for building a multi-phase fluid heat and mass transfer mathematical model and embedding the multi-phase fluid heat and mass transfer mathematical model into Fluent software;
the grid model assembling module is used for assembling the grid model of the fluid domain and the grid model of the phase-change solid domain and guiding the assembled grid models into Fluent software;
and the simulation analysis module is used for carrying out numerical simulation analysis by adopting Fluent software based on the boundary condition of the grid model.
9. An intelligent terminal, characterized in that the intelligent terminal comprises a memory, a processor and a porous medium heat flow solidification coupling multi-phase seepage simulation program containing phase change stored in the memory and capable of running on the processor, and the processor executes the porous medium heat flow solidification coupling multi-phase seepage simulation program containing phase change to realize the steps of the porous medium heat flow solidification coupling multi-phase seepage simulation method containing phase change according to any one of claims 1 to 7.
10. A computer-readable storage medium, wherein the computer-readable storage medium stores a phase-change-containing porous medium heat flow solidification coupled multiphase seepage simulation program, and when the phase-change-containing porous medium heat flow solidification coupled multiphase seepage simulation program is executed by a processor, the steps of the phase-change-containing porous medium heat flow solidification coupled multiphase seepage simulation method according to any one of claims 1-7 are implemented.
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