Sand-dust environment foam metal heat dissipation performance evaluation method

Abstract

The application provides a kind of sand-dust environment foam metal heat dissipation performance evaluation method, mainly including adopting foam metal structure basic unit to build physical model, and the simulation model of foam metal structure basic unit is obtained by numerical solution method;According to the operation environment of the vehicle foam metal radiator under sand-dust environment, the continuous phase is air, and the discrete phase is sand-dust particulate matter, and the discrete phase model and the continuous phase model are constructed by algebraic equation;According to the actual working condition, the sand-dust particulate matter parameters are determined, and the deposition model and the erosion model of sand-dust particulate matter are constructed;The simulation calculation of sand-dust particulate matter to foam metal structure is carried out.The sand-dust environment performance analysis method of the foam metal provided by the application can reduce the pollution blockage of heat exchanger pores, improve the heat exchange performance of foam metal, prevent the impact and wear of sand-dust particles on foam metal skeleton, and prolong the service life of foam metal.

Description

Technical Field

[0001] This invention relates to a compact heat exchange technology, specifically, to a method for evaluating the heat dissipation performance of foamed metal in a dusty environment. Background Technology

[0002] Due to its high specific surface area, high porosity, high thermal conductivity, high strength, high toughness, and light weight, open-cell foamed metal can be used as a heat exchange medium to replace the compact heat exchangers in traditional military vehicles. However, because the working environment of military vehicles is much harsher than that of civilian vehicles, especially in dusty environments, high-speed flowing sand can impact and clog the framework of the foamed metal radiator, as well as affect the flow pattern of the heat exchange fluid.

[0003] Currently, research on foamed metal structures mainly focuses on enhancing heat transfer, reducing resistance, and processing technology. However, there are few publicly available reports on measuring the heat transfer performance of foamed metals in dusty environments. Therefore, there is an urgent need for an evaluation method to measure the heat dissipation performance of foamed metals in dusty environments. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a method for evaluating the heat dissipation performance of foamed metal in dusty environments. This method can analyze the adhesion and blockage of particulate matter concentration and pollutants on the foamed metal skeleton, as well as the impact and wear of high-speed flowing particulate matter on the foamed metal skeleton, thereby obtaining the influence law of gas-solid two-phase fluid on the heat transfer performance of foamed metal in dusty environments.

[0005] This invention provides a method for evaluating the heat dissipation performance of foamed metal in dusty environments, comprising the following steps:

[0006] Step S1: Simplify the physical model of the actual foam metal structure;

[0007] Step S2: Construct a physical model using basic foam metal structure units, and obtain a simulation model of the basic foam metal structure units through numerical solution method;

[0008] Step S3: Based on the operating environment of the automotive foam metal radiator in a sandstorm environment, the continuous phase is air and the discrete phase is sand and dust particles. The discrete phase model and the continuous phase model are constructed through algebraic equations.

[0009] Step S4: Determine the dust particle parameters based on the actual working conditions. The dust particle parameters include the dust particle injection area, dust particle velocity, injection point density, and dust particle diameter.

[0010] Step S5: Calculate the simulation model of the basic unit of the foam metal structure to ensure the effectiveness of the foam metal structure simulation model. If the result converges, proceed to step S6; if the result does not converge, proceed to step S2 to re-mesh the simulation model and correct the solution method.

[0011] Step S6: Construct sedimentation and erosion models for dust particles;

[0012] Step S7: Obtain the dimensionless parameters of the foam metal structure based on the simulation model of the basic unit of the foam metal structure. The dimensionless parameters include the heat transfer factor. and resistance factor The overall heat transfer performance index is j / f, where Re is the Reynolds number, Nu is the Nusselt number, and the equivalent diameter of the foam metal is... V is the fluid flow volume, A is the wetted surface area, Δp is the pressure drop per unit length, ρ is the fluid density, v is the fluid velocity, and Pr is the Prandtl number.

[0013] Step S8: Perform simulation calculations on the blockage and wear of the foam metal structure by sand and dust particles; start the CFD software to perform the calculation. If the calculation converges, proceed to step S9. If the calculation does not converge, proceed to step S2 to re-mesh the simulation model of the basic unit of the foam metal structure and correct the solution method.

[0014] Step S9: Compare and verify the test results of foam metal radiators in dusty environments;

[0015] Step S10: Using the simulation model of foam metal structure in a sandstorm environment verified by the above experiments, analyze and calculate the influence mechanism of sandstorm particle size, sandstorm concentration and sandstorm flow velocity on the wear and blockage of the foam metal structure.

[0016] Furthermore, the simplification in step S1 includes selecting basic units of the foam metal structure instead of the actual foam metal structure.

[0017] Furthermore, in step S2: the physical problem of convective heat transfer in the foam metal structure is solved numerically, replacing the original continuous physical quantity field in time and space coordinates with a set of numerical values ​​of a finite number of discrete points.

[0018] Furthermore, in step S3: the continuous phase control equations satisfy the continuity equation, momentum equation, and energy equation, which are uniformly expressed as differential form equations:

[0019]

[0020] Among them, Γ φ Let φ be the generalized diffusion coefficient, ρ be the density, and t be the time. For the gradient, the first term The second term is the time term. For convection, the third term The fourth term, S(φ), is the source term. In the continuity equation, φ is 1. In the momentum equation, φ is the vector velocity u. In the energy equation, φ is the temperature.

[0021] The equation of motion for discrete phase particles is:

[0022]

[0023] Where, m p Let v represent particle mass, t represent time, and v represent the particle mass. p F represents the instantaneous particle velocity. s It is the resultant force of the forces acting on the particle surface, F. b It is the resultant force of volume forces.

[0024] Furthermore, in step S6: when the sand and dust particles collide with the wall, the critical rebound velocity is... Where, d s Let be the diameter of the solid particle, ζ be the coefficient of restitution, and E be Young's modulus.

[0025] When the incident angle of dust particles is greater than the critical adhesion angle, it is corrected to θ′=θ+ζΔγ, where θ is the particle incident angle, Δγ is the roughness correction angle, θ′ is the corrected incident angle, and ζ is a Gaussian random number.

[0026] An erosion model of dust particles is constructed, and the damage caused by each particle impact to the wall, baffle, and contact boundary is calculated. Among them, A f This refers to the area of ​​the wall, baffle, and contact boundary surfaces. e represents the mass flow rate of particles impacting the wall, baffle, and contact boundary surfaces in the particle beam π. r The erosion rate is calculated by summing the values ​​of all particle beams that impact the surface during the calculation time step.

[0027] The Lagrange method was used to track the movement of dust particles. Based on the collision, rebound, erosion and deposition of dust particles, deposition and erosion models of dust particles were constructed.

[0028] Furthermore, in step S9: under the same inlet air temperature, wind speed, altitude, and heat flux density, the air-side outlet temperature measured by the test and simulation are compared.

[0029] The dust environment performance analysis method for foamed metal provided by this invention can reduce the clogging of heat exchanger pores by pollutants, improve the heat exchange performance of foamed metal, and at the same time prevent dust particles from impacting and wearing the foamed metal skeleton, thereby extending the service life of foamed metal.

[0030] The method for evaluating the heat dissipation performance of foamed metal in a dusty environment provided by this invention has the following advantages:

[0031] The method for analyzing the performance of foamed metal in dusty environments provided by this invention is more targeted in predicting the heat dissipation performance of foamed metal in dusty and particulate environments.

[0032] Based on the flow and heat dissipation characteristics of foamed metal obtained by this method, it can provide methodological guidance for the design of composite multi-group foamed metal heat exchangers. In the future, through structural optimization, the heat exchange performance of foamed metal can be improved while preventing the impact and wear of sand and dust particles on the foamed metal skeleton, thereby extending the service life of foamed metal.

[0033] This invention can reduce the requirements for computer hardware, realize the efficient solution of multiphase flow heat transfer in compact heat exchange structures in dusty environments, and at the same time, the heat dissipation evaluation index does not change much. Attached Figure Description

[0034] Figure 1 This is a flowchart of a method for evaluating the heat dissipation performance of foam metal in a dusty environment, according to an embodiment of the present invention. Detailed Implementation

[0035] To better understand the purpose, technical solution, and function of this invention, the following description is in conjunction with the appendix. Figure 1 The present invention will be described in further detail below, but it may be implemented in many different ways as defined and covered by the claims. The accompanying drawings, which form part of this application, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention.

[0036] The method of the present invention includes obtaining a foam metal simulation model and dust particle parameters; obtaining a foam metal structure simulation model to realize the test and analysis of the flow and heat transfer characteristics of the foam metal structure and optimize the simulation analysis process.

[0037] like Figure 1 As shown, this invention proposes a method for evaluating the heat dissipation performance of foamed metal in dusty environments, comprising:

[0038] Step S1: Simplify the physical model of the actual foam metal structure;

[0039] Preferably, using foam metal structural basic units to construct the physical model can reduce the number of meshes, save computing resources to a great extent, and not place too high demands on computer hardware and computing.

[0040] Specifically, basic units of foam metal structures can be selected to replace actual foam metal structures. This can reduce unnecessary calculations while ensuring that the accuracy and reliability of the simulated structure are not affected.

[0041] Step S2: Construct a physical model using basic foam metal structure units, and obtain a simulation model of the basic foam metal structure units through numerical solution method;

[0042] Specifically, the physical problem of convective heat transfer in foam metal structures is solved numerically, replacing the original continuous physical quantity field in time and space coordinates with a set of numerical values ​​of a finite number of discrete points.

[0043] The present invention preferably uses a continuous phase model and a discrete phase model (DPM) to set the simulation parameters of the foam metal structure.

[0044] Step S3: Based on the operating environment of the automotive foam metal radiator in a dusty environment, the continuous phase is air and the discrete phase is dust particles. The discrete phase model and the continuous phase model are constructed through algebraic equations.

[0045] Specifically, the control equations for the continuous phase satisfy the continuity equation, momentum equation, and energy equation. The equations uniformly expressed in differential form are as follows: Γ φ Let ρ be the generalized diffusion coefficient, φ be the generalized variable, ρ be the density, and t be the time. For the gradient, the first term The second term is the time term. For convection, the third term The term S is the diffusion term, and the fourth term S(φ) is the source term. In the continuity equation, φ is 1; in the momentum equation, φ is the vector velocity u; and in the energy equation, φ is the temperature.

[0046] The equation of motion for discrete phase particles is Where, m p Let v represent particle mass, t represent time, and v represent the particle mass. p F represents the instantaneous particle velocity. s It is the resultant force of the forces acting on the particle surface, F. b It is the resultant force of volume forces;

[0047] The parameters of dust particles include flow rate, concentration, particle size specification, and particle quantity; the simulation parameters include the following: dust particle injection area, injection point density, particle flow rate, particle diameter, etc.; preferably, the air inlet area of ​​the basic unit structure of the foam metal radiator is set as the particle injection area.

[0048] Step S4: Determine the dust particle parameters based on the actual working conditions. The dust particle parameters include: dust particle injection area, dust particle velocity, injection point density, and dust particle diameter.

[0049] Step S5: Calculate the simulation model of the basic unit of the foam metal structure to ensure the effectiveness of the foam metal structure simulation model. If the result converges, proceed to step S6; if the result does not converge, proceed to step S2 to re-mesh the simulation model and correct the solution method.

[0050] Step S6: Construct a deposition model and an erosion model for sand and dust particles to ensure the effectiveness of the foam metal structure simulation model;

[0051] Specifically, the deposition of solid particles depends on the normal velocity and incident angle of the sand particles colliding with the surface. When the normal velocity of a particle impacting the wall is too high, it will bounce off the wall and will not be deposited on the solid wall surface. The critical bounce velocity is... Where, d s Let be the diameter of the solid particle, ζ be the coefficient of restitution, and E be Young's modulus.

[0052] When the incident angle of the particles is greater than the critical adhesion angle, the particles will slide and roll on the deposition surface until they leave the deposition surface. When there is dirt on the wall surface that the particles collide with, the incident angle will change, and this will be corrected to... Where θ is the particle incident angle, Δγ is the roughness correction angle, θ′ is the corrected incident angle, and ζ is a Gaussian random number.

[0053] Specifically, an erosion model of dust particles is constructed, and the damage caused by each particle impact to the wall, baffle, and contact boundary is calculated. Among them: A f This refers to the area of ​​the wall, baffle, and contact boundary surfaces. e represents the mass flow rate of particles impacting the wall, baffle, and contact boundary surfaces in the particle beam π. r The erosion rate is the sum of all particle beams that impact the surface during the calculation time step.

[0054] This invention employs the Lagrange method to track dust particles. Due to the small particle size of dust particles, drag, inertial force, and Saverman lift cannot be ignored in the force analysis. By constructing deposition and erosion models for the particles, actual physical phenomena such as particle collision, impact, erosion, and deposition are considered.

[0055] Specifically, the Lagrange method is used to track the movement of dust particles, as these particles are subject to drag, inertial force, Brownian force, and Saverman lift. Furthermore, based on the actual physical phenomena of dust particle collision, rebound, erosion, and deposition, deposition and erosion models are constructed.

[0056] Step S7: Obtain the dimensionless parameters of the foam metal structure and the dimensionless heat transfer factor based on the simulation model of the basic unit of the foam metal structure. and resistance factor The overall heat transfer performance index is j / f, where Re is the Reynolds number, Nu is the Nusselt number, and the equivalent diameter of the foam metal is... V is the fluid flow volume, A is the wetted surface area, Δp is the pressure drop per unit length, ρ is the fluid density, v is the fluid velocity, and Pr is the Prandtl number.

[0057] The present invention preferably uses computational fluid dynamics (CFD) methods to construct a foam metal simulation model.

[0058] Step S8: Conduct simulation calculations on the blockage and wear of the foam metal structure by sand and dust particles; start the CFD software to perform the calculation. If the calculation converges, proceed to step S9. If the calculation does not converge, proceed to step S2 to re-mesh the simulation model of the basic unit of the foam metal structure and correct the solution method.

[0059] Step S9 involves comparative verification based on the experimental results of the foam metal radiator in a dusty environment. Specifically, under the same inlet air temperature, wind speed, altitude, and heat flux density, the air-side outlet temperature measured by experiments and simulations is compared. This ensures the effectiveness of the foam metal structure simulation model in a dusty environment.

[0060] Step S10: Using the simulation model of foam metal structure in a sandy environment verified by the above experiments, analyze and calculate the influence mechanism of sand particle size, sand concentration and sand flow velocity on the wear and blockage of foam metal structure, as a conclusion on the adaptability of foam metal structure in sandy environment, and finally form a universal simulation method for foam metal structure in sandy environment.

[0061] The above embodiments are merely preferred embodiments of the present invention. Therefore, all equivalent changes or modifications made to the structure, features and principles described in the claims of this patent application are included within the scope of this patent application.

Claims

1. A method for evaluating the heat dissipation performance of foamed metal in a dusty environment, characterized in that, Includes the following steps: Step S1: Simplify the physical model of the actual foam metal structure; Step S2: Construct a physical model using basic foam metal structure units, and obtain a simulation model of the basic foam metal structure units through numerical solution method; Step S3: Based on the operating environment of the automotive foam metal radiator in a sandstorm environment, the continuous phase is air and the discrete phase is sand and dust particles. The discrete phase model and the continuous phase model are constructed through algebraic equations. Step S4: Determine the dust particle parameters based on the actual working conditions. The dust particle parameters include the dust particle injection area, dust particle velocity, injection point density, and dust particle diameter. Step S5: Calculate the simulation model of the basic unit of the foam metal structure to ensure the effectiveness of the foam metal structure simulation model. If the result converges through the solution calculation, proceed to step S6. If the result does not converge, proceed to step S2 to re-mesh the simulation model and correct the solution method; Step S6: Construct sedimentation and erosion models for dust particles; Step S7: Obtain the dimensionless parameters of the foam metal structure based on the simulation model of the basic unit of the foam metal structure. The dimensionless parameters include the heat transfer factor. and resistance factor The overall heat transfer performance index is j / f, where Re is the Reynolds number, Nu is the Nusselt number, and the equivalent diameter of the foam metal is... V is the fluid flow volume, A is the wetted surface area, Δp is the pressure drop per unit length, ρ is the fluid density, v is the fluid velocity, and Pr is the Prandtl number. Step S8: Perform simulation calculations on the blockage and wear of the foam metal structure by sand and dust particles; start the CFD software to perform the calculation. If the calculation converges, proceed to step S9. If the calculation does not converge, proceed to step S2 to re-mesh the simulation model of the basic unit of the foam metal structure and correct the solution method. Step S9: Compare and verify the test results of foam metal radiators in dusty environments; Step S10: Using the simulation model of foam metal structure in a sandstorm environment verified by the above experiments, analyze and calculate the influence mechanism of sandstorm particle size, sandstorm concentration and sandstorm flow velocity on the wear and blockage of the foam metal structure.

2. The method for evaluating the heat dissipation performance of foamed metal in a sand and dust environment according to claim 1, characterized in that, The simplification in step S1 includes selecting basic units of the foam metal structure to replace the actual foam metal structure.

3. The method for evaluating the heat dissipation performance of foamed metal in a dusty environment according to claim 2, characterized in that, In step S2: The physical problem of convective heat transfer in foam metal structure is solved numerically by replacing the original continuous physical quantity field in time and space coordinates with a set of numerical values ​​of a finite number of discrete points.

4. The method for evaluating the heat dissipation performance of foamed metal in a dusty environment according to claim 3, characterized in that, In step S3: the continuous phase control equations satisfy the continuity equation, momentum equation, and energy equation, which are uniformly expressed as differential form equations: Among them, Γ φ Let φ be the generalized diffusion coefficient, ρ be the density, and t be the time. For the gradient, the first term The second term is the time term. For convection, the third term The fourth term, S(φ), is the source term. In the continuity equation, φ is 1. In the momentum equation, φ is the vector velocity u. In the energy equation, φ is the temperature. The equation of motion for discrete phase particles is: Where, m p Let v represent particle mass, t represent time, and v represent the particle mass. p F represents the instantaneous particle velocity. s It is the resultant force of the forces acting on the particle surface, F. b It is the resultant force of volume forces.

5. The method for evaluating the heat dissipation performance of foamed metal in a sand and dust environment according to claim 4, characterized in that, In step S6: when sand and dust particles collide with the wall, the critical rebound velocity is... Where, d s Let be the diameter of the solid particle, ζ be the coefficient of restitution, and E be Young's modulus. When the incident angle of dust particles is greater than the critical adhesion angle, it is corrected to Where θ is the particle incident angle, Δγ is the roughness correction angle, θ' is the corrected incident angle, and ζ is a Gaussian random number. An erosion model of dust particles is constructed, and the damage caused by each particle impact to the wall, baffle, and contact boundary is calculated. Among them, A f This refers to the area of ​​the wall, baffle, and contact boundary surfaces. e represents the mass flow rate of particles impacting the wall, baffle, and contact boundary surfaces in the particle beam π. r The erosion rate is calculated by summing the values ​​of all particle beams that impact the surface during the calculation time step. The Lagrange method was used to track the movement of dust particles. Based on the collision, rebound, erosion and deposition of dust particles, deposition and erosion models of dust particles were constructed.

6. The method for evaluating the heat dissipation performance of foamed metal in a dusty environment according to claim 5, characterized in that, In step S9: Under the same inlet air temperature, wind speed, altitude, and heat flux density, the air-side outlet temperature measured by the test and simulation are compared.

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