Method and device for calculating heating performance of vehicle high-pressure heater and medium

Abstract

The invention discloses a method and equipment for calculating the heating performance of a vehicle high-pressure heater and a medium. The method comprises the steps that a heater model extracts a flow channel, all areas of the heater model are divided, and all boundaries are named; grid division is carried out on the heater model; and performing simulation calculation on the grid model, obtaining an output value through simulation, and further determining the heat transfer efficiency of the heater based on the output value. Compared with a common method for obtaining the heating performance of the vehicle high-pressure heater, namely theoretical calculation and physical test, the calculation method for the heating performance of the vehicle high-pressure heater, provided by the invention, is higher in calculation precision than theoretical calculation; compared with a physical test, the calculation process is simple, the speed is high, and the heating performance of the vehicle-used high-pressure heater under different working conditions can be directly calculated.

Description

Technical Field

[0001] The present invention relates to the technical field related to the performance simulation of vehicle high - voltage heaters, and more specifically, to a calculation method, device, and medium for the heating performance of vehicle high - voltage heaters. Background Art

[0002] Common methods for obtaining the heating performance of vehicle high - voltage heaters are usually theoretical calculations and physical tests. The theoretical calculations are based on empirical formulas, and the obtained results have low accuracy; in physical tests, the measuring instruments are expensive, and when measuring multiple working conditions, there are also problems such as cumbersome test processes and excessive time consumption. Summary of the Invention

[0003] In order to solve at least one of the problems existing in the prior art, the present invention provides a calculation method for the heating performance of vehicle high - voltage heaters. Compared with theoretical calculations, the accuracy of the obtained results is high; compared with physical tests, the heating performance of the heater under different working conditions can be directly obtained, and the determination process is simple and fast.

[0004] To achieve the object of the present invention, a calculation method for the heating performance of vehicle high - voltage heaters provided by the present invention includes the following steps:

[0005] Extract the flow channels of the vehicle high - voltage heater model, divide each region of the vehicle high - voltage heater model, and name each boundary;

[0006] Perform mesh division on the vehicle high - voltage heater model, add boundary - layer meshes, and encrypt the fluid - domain meshes;

[0007] Perform simulation calculations on the mesh model of the heater, and obtain output values through simulation. The output values include the inlet liquid temperature T in and the outlet liquid temperature T out , where, during simulation, the heat transfer is simulated by the thermal - fluid - solid coupling method, the resistance region is set as the heat source, representing the input of heat, the heat is transferred to the heating plate in the heating - plate assembly, and then the heating plate transfers the heat to the fluid;

[0008] Determine the heat transfer efficiency of the heater based on the output values obtained through simulation.

[0009] Preferably, a pre - processing software is used to extract the flow channels of the vehicle high - voltage heater model.

[0010] For the vehicle high - voltage heater model, the mass conservation in fluid flow is described by the continuity equation:

[0011]

[0012] In the formula: ρ is the fluid density; u is the fluid velocity; t is the time.

[0013] Preferably, a surface mesh, a volume mesh, and a boundary layer mesh are added to the heater model using meshing software, and the fluid domain mesh needs to be refined. The boundary layer thickness can be calculated as follows:

[0014]

[0015] In the formula: L is the characteristic length; Re is the Reynolds number.

[0016] Preferably, the main heat transfer mode of the vehicle high-voltage heater model is heat conduction, and its formula is:

[0017]

[0018] In the formula: ρ is the density of the substance; c p is the specific heat capacity; T is the temperature; k is the thermal conductivity; Q is the internal heat source term.

[0019] Preferably, due to the inlet effect and outlet effect in fluid simulation software, in order to accurately obtain parameters, the lengths of the liquid inlet section and the liquid outlet section need to be increased before extracting the flow channel, and the increased lengths should be large enough so that the fluid can reach a stable state before entering the main flow region. The lengths of the liquid inlet section and the liquid outlet section are calculated by the following formula:

[0020]

[0021] In the formula: L in is the length of the liquid inlet section; L out is the length of the liquid outlet section; D in is the diameter of the liquid inlet; D out is the diameter of the liquid outlet.

[0022] Preferably, when performing mesh division, shared topology makes the interface meshes between regions of the heater model share nodes.

[0023] Preferably, when performing simulation, the k-ε model is selected for the turbulence model, and the corresponding turbulence model formula is as follows:

[0024]

[0025] In the formula: G k is the turbulent kinetic energy caused by the mean velocity gradient; G b is used for the generation of turbulent kinetic energy caused by buoyancy effects; Y M is the factor for the influence of compressible velocity turbulent pulsation expansion on the total dissipation rate; μ t is the turbulent viscosity coefficient, μ t = ρC μ k 2 / ε.

[0026] Select the mass flow rate inlet for the inlet condition. Select the pressure outlet for the outlet condition. The formula is:

[0027] P out = P atm (7)

[0028] In the formula: P out is the pressure at the liquid outlet, and P atm is the standard atmospheric pressure.

[0029] Preferably, the formula for determining the heat transfer efficiency of the vehicle high-pressure heater is:

[0030]

[0031] The present invention also provides a computer device, including a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, it implements the foregoing calculation method for the heating performance of a vehicle high-pressure heater.

[0032] The present invention also provides a computer-readable storage medium. The computer-readable storage medium stores a computer program, and when the computer program is executed by a processor, it implements the foregoing calculation method for the heating performance of a vehicle high-pressure heater.

[0033] Compared with the prior art, the present invention has at least the following beneficial effects:

[0034] Compared with the common methods for obtaining the heating performance of a vehicle high-pressure heater: theoretical calculation and physical experiment, the present invention has higher accuracy than theoretical calculation, and the determination process is simpler, faster than physical experiment, and can directly obtain the heating performance of the heater under different working conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 It is a schematic diagram of the appearance structure of a vehicle high-pressure heater model in an embodiment of the present invention.

[0036] Figure 2 It is a schematic diagram of the internal structure of a vehicle high-pressure heater model in an embodiment of the present invention.

[0037] Figure 3 It is a diagram of the processing result of the heater model by the preprocessing software in an embodiment of the present invention.

[0038] Figure 4 It is a grid diagram of the heater model divided by the grid division software in an embodiment of the present invention.

[0039] Figure 5 It is a temperature contour map of the heating plate assembly in the heater model obtained by the fluid simulation software in an embodiment of the present invention.

[0040] Figure 6 This is the velocity streamline diagram of the fluid in the heater model obtained by the fluid simulation software in the embodiment of the present invention.

[0041] Figure 7 It is the step flow chart of a calculation method for the heating performance of a vehicle-mounted high-voltage heater provided by the embodiment of the present invention.

[0042] In the figure: metal housing 1; liquid inlet pipe 2; liquid outlet pipe 3; high-voltage connection plug 4; low-voltage connection plug 5; cover 6; heating plate assembly 7; resistance area 7.1; controller assembly 8. Detailed implementation manners

[0043] To make the objectives, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Apparently, the described embodiments are some but not all of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts are within the scope of protection of the present invention.

[0044] Please refer to Figure 1 , in the figure, an external structure diagram of a vehicle-mounted high-voltage heater model is shown, Figure 2 showing an internal structure diagram of a vehicle-mounted high-voltage heater model. The vehicle-mounted high-voltage heater includes a housing 1, a liquid inlet pipe 2, a liquid outlet pipe 3, a high-voltage connection plug 4, a low-voltage connection plug 5, a cover 6, a heating plate assembly 7, and a controller assembly 8. The gap area between the housing 1 and the heating plate assembly 7 is a flow channel, and the resistance area 7.1 is brazed in the heating plate assembly 7.

[0045] The heating plate assembly 7 and the flow channel form a simulation domain.

[0046] Figure 3 showing the preprocessing of the heater model by the preprocessing software: increasing the lengths of the liquid inlet section and the liquid outlet section, extracting the flow channel, dividing each area of the heater model (such as the liquid inlet, the liquid outlet, and the interface between the fluid and the solid), naming each boundary, and facilitating the subsequent setting of boundary conditions and calculations.

[0047] Please refer to Figure 6 , a calculation method for the heating performance of a vehicle-mounted high-voltage heater provided by the present invention includes the following steps:

[0048] Step 1: Use the preprocessing software to extract the flow channel of the vehicle-mounted high-voltage heater model, divide each area of the heater model, and name each boundary.

[0049] In some embodiments of the present invention, each area includes a liquid inlet, a liquid outlet, and an interface between the fluid and the solid.

[0050] In computational fluid dynamics (CFD), the extraction of flow channels and the naming of boundaries are the basis for model establishment. In some embodiments of the present invention, for the vehicle high-pressure heater model, the inlet, outlet, and fluid inflow direction are set in the SPACECLAIM software to obtain accurate flow channels. The accurate extraction of the geometric characteristics of the flow channels can ensure the accuracy of simulation calculations.

[0051] The mass conservation in fluid flow is described by the continuity equation:

[0052]

[0053] In the formula: ρ is the density of the fluid; u is the velocity of the fluid; t is the time. is the divergence, which is a quantity describing the fluid source or sink, indicating whether the fluid is generated or disappears in space. For fluid flow, the divergence measures the net inflow or outflow rate of the fluid per unit volume.

[0054] Since there are inlet effects and outlet effects in fluid simulation software, in order to accurately obtain parameters, in some embodiments of the present invention, the lengths of the inlet section and the outlet section are appropriately increased before extracting the flow channels to reduce the influence of the inlet effect and the outlet effect on the calculation results, and appropriate lengths of the inlet section and the outlet section are added to the heater model. The lengths of the increased inlet section and outlet section should ensure that before the fluid enters the main flow region, parameters such as flow velocity and temperature can reach a stable state, avoiding the influence of the initial disturbance of the fluid on the simulation results. Among them, the lengths of the inlet section and the outlet section are calculated by the following formula:

[0055]

[0056] In the formula: L in is the length of the inlet section; L out is the length of the outlet section; D in is the diameter of the inlet; D out is the diameter of the outlet.

[0057] The main flow region refers to the part where the fluid mainly flows in the pipeline or flow channel. Usually, after the fluid has undergone sufficient stable development, the flow characteristics are no longer affected by the inlet and outlet. In this region, the velocity distribution, pressure distribution, and temperature field of the fluid have tended to be stable and reflect the typical flow characteristics of the pipeline or flow channel.

[0058] Step 2: Use the mesh generation software to divide the surface mesh and volume mesh of the vehicle high-pressure heater model, add boundary layer meshes, and perform encryption processing on the fluid domain mesh to obtain the mesh model of the heater.

[0059] Mesh generation is an important step in computational fluid dynamics (CFD) simulations, which determines the accuracy of the numerical solution and the computational efficiency. The boundary layer mesh is used to capture the flow details near the solid surface, and the boundary layer thickness can be calculated as follows:

[0060]

[0061] where: L is the characteristic length; Re is the Reynolds number; C is an empirical constant used to adjust and specify the actual situation of fluid flow. The value of C is related to factors such as the flow type, the geometry of the flow, and the physical properties of the fluid. In some embodiments of the present invention, if the fluid flow type is laminar, C takes an empirical value of 5; if the fluid flow type is turbulent, then C takes an empirical value of 0.37.

[0062] In some embodiments of the present invention, to improve the simulation accuracy of the model, the fluid domain mesh of the vehicle high-pressure heater model can be refined; to make the interface meshes between different regions of the heater model share the same nodes, the topology of the vehicle high-pressure heater model can be shared.

[0063] In some embodiments of the present invention, Figure 4 shows the mesh diagram of the heater model divided by the mesh software.

[0064] Step 3: Use fluid simulation software to perform simulation calculations on the mesh model of the heater, and obtain the output values through the simulation. The output values include the inlet temperature T in and the outlet temperature T out . Among them, when performing the simulation, the heat transfer is simulated by the thermal-fluid-solid coupling method. The resistance region is set as the heat source, representing the input of heat, and the heat is transferred to the heating plate in the heating plate assembly, and then the heating plate transfers the heat to the fluid.

[0065] The thermal-fluid-solid coupling method is used to simulate the multi-physics field coupling and can accurately predict the temperature distribution and fluid flow inside the heater. The main heat transfer method of the vehicle heater model is heat conduction, and the formula for heat conduction is as follows:

[0066]

[0067] where: ρ is the density of the fluid; c p is the specific heat capacity of the fluid; T is the temperature; k is the thermal conductivity; Q is the internal heat source term.

[0068] In this step, the k-ε model is selected as the turbulence model, and the corresponding turbulence model formula is as follows:

[0069]

[0070] where: G k is the turbulent kinetic energy caused by the mean velocity gradient; G bFor the generation of turbulent kinetic energy caused by buoyancy effects; Y M Is the factor for the influence of compressible turbulent pulsation expansion on the total dissipation rate; μ t Is the turbulent viscosity coefficient, μ t = ρC μ k 2 / ε, C μ Is the number that adjusts the relationship between the turbulent viscosity coefficient and the turbulent kinetic energy; x i Is the spatial coordinate direction, used to describe the position of the fluid; μ is the dynamic viscosity of the fluid; σ k Is a dimensionless number that measures the relative magnitude between the diffusion rate of turbulent kinetic energy and the dissipation rate of turbulent energy; ε is the dissipation rate of turbulent kinetic energy; C 1g 、C 3g 、C 2g Are the numbers used to adjust the influence of buoyancy on turbulence in the turbulence model.

[0071] The inlet condition selects the mass flow rate inlet, and the outlet condition selects the pressure outlet. The formula is:

[0072] P out = P atm (7)

[0073] In the formula: P out Is the pressure at the liquid outlet; P atm Is the standard atmospheric pressure. In some embodiments of the present invention, P out Is set as a constant, which can ensure that the fluid leaves the outlet of the computational domain at a stable pressure and enables the fluid to be discharged from the computational area smoothly.

[0074] In some embodiments of the present invention, in step 3, during the numerical solution process, when the difference between the calculated physical quantities (such as velocity, pressure, turbulent kinetic energy, etc.) and their theoretical or previously calculated values that should be satisfied in the equation, that is, the residual value, is less than a preset value (such as 10 to the power of -3), it can be considered that convergence is achieved.

[0075] In some embodiments of the present invention, the temperature contour map of the heating plate assembly in the vehicle high-pressure heater model obtained by the fluid simulation software is as Figure 5 shown. Through the temperature contour map, the temperature changes in different regions of the vehicle high-pressure heater can be observed, and it can be judged whether the heat is evenly distributed, whether there are overheating or heat concentration regions, and it can reveal the heat transfer efficiency, the location of hot spots, and the possible thermal failure risks.

[0076] The velocity streamline map of the fluid in the vehicle high-pressure heater model obtained by the fluid simulation software is as Figure 6As shown. Through the velocity streamline diagram, it can help to understand the flow situation of the fluid in the heater. The streamline diagram can show the flow path of the fluid, the magnitude of the flow velocity and its distribution, and then analyze whether the fluid flows smoothly and whether there are flow uneven phenomena such as dead zones and vortices. Through this diagram, it can also be judged whether the fluid flow effectively takes away the heat from the heater surface to optimize the heating efficiency.

[0077] Step 4: Based on the inlet temperature T obtained from the simulation in and the outlet temperature T out , the heat transfer efficiency of the vehicle high-pressure heater is obtained through the calculation formula.

[0078] In this step, the fluid density ρ, the specific heat capacity C of the fluid p , the fluid volume flow rate the heating electric power P are known. Combining with the inlet temperature T obtained after the simulation is completed in and the outlet temperature T out , then the heat transfer efficiency η of the heater is:

[0079]

[0080] In some embodiments of the present invention, a computer device is provided, including a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, it implements a calculation method for the heating performance of a vehicle high-pressure heater provided in the foregoing embodiments.

[0081] In some embodiments of the present invention, a computer-readable storage medium is provided. The computer-readable storage medium stores a computer program, and when the computer program is executed by a processor, it implements a calculation method for the heating performance of a vehicle high-pressure heater provided in the foregoing embodiments.

[0082] Traditional theoretical calculations need to be based on empirical formulas, which are obtained under certain assumptions and can only provide a rough estimate. Their accuracy is limited by the assumptions. The present invention obtains the heating performance of a vehicle high-voltage heater based on a simulation method. The simulation method can consider various variables, such as geometric shape, fluid flow characteristics, temperature distribution, etc., at a higher accuracy, and can model and analyze the heater in more detail, so that more accurate calculation results of the heat transfer efficiency can be obtained. Traditional theoretical calculations require setting up a test device for physical experiments. It is necessary to set up an actual vehicle high-voltage heater on the test bench and perform settings and debugging. It may take 1 hour to obtain data for testing one working condition. However, the simulation method of the present invention can directly simulate through a computer model, avoiding the time-consuming and cumbersome steps of these physical processes, consuming less time and obtaining the heating performance faster. In physical experiments, if it is necessary to verify the heating performance under different working conditions, it is necessary to replace the experimental equipment, adjust the experimental parameters or conduct experiments under different conditions. However, through the simulation method, only input parameters such as mass flow rate, pressure, temperature, etc. need to be adjusted, and the results under different working conditions can be quickly viewed without actually conducting multiple experiments, and the heating performance of the vehicle high-voltage heater under different working conditions can be directly calculated.

[0083] In some embodiments of the present invention, the outlet temperature and the pressure difference between the inlet and the outlet are evaluation indicators for measuring the accuracy of different methods. Taking the physical experiment as the reference standard, the theoretical calculation error is 12.8%, and the error of the simulation method of the present invention is 1.4%, which verifies the reliability and superiority of the method of the present invention.

[0084] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be obvious to those skilled in the art. The general principles defined in the present invention can be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to these embodiments shown in the present invention, but will conform to the widest scope consistent with the principles and novel features disclosed in the present invention.

Claims

1. A method for calculating the heating performance of a high-voltage heater for a vehicle, characterized in that: The following steps are involved: Extract the flow channel of the automotive high-voltage heater model, divide the various regions of the automotive high-voltage heater model, and name each boundary; Mesh the automotive high-voltage heater model, add boundary layer meshes, and encrypt the fluid domain meshes; The grid model of the heater is simulated and calculated, and output values ​​are obtained through simulation, and the output values ​​include the liquid inlet temperature T in and the outlet temperature T out ,Among them, the thermal-fluid-solid coupling method is used to simulate the heat transfer during ,the simulation, and the resistance area is set as the heat source, which ,represents the heat input. The heat is transferred to the heating plate in the ,heating plate assembly, and then the heating plate transfers it to the fluid; Based on the output values ​​obtained from the simulation, the heat transfer efficiency of the heater is determined.

2. The method for calculating the heating performance of a vehicle high-voltage heater according to claim 1, characterized in that: Use pre-processing software to extract flow channels from the automotive high-voltage heater model.

3. The method for calculating the heating performance of a vehicle high-voltage heater according to claim 1, characterized in that: Before extracting the flow channel, the length of the inlet and outlet sections is increased so that the fluid can reach a stable state before entering the main flow area. The length of the inlet and outlet sections is calculated by the following formula: Where, L in L is the length of the liquid inlet section; out is the length of the liquid outlet section; D in is the diameter of the liquid inlet; D out is the diameter of the liquid outlet.

4. The method for calculating the heating performance of a vehicle high-voltage heater according to claim 1, characterized in that: Boundary layer meshes are used to capture the details of the flow close to the solid surface. The boundary layer thickness can be calculated as: Where L is the characteristic length; Re is the Reynolds number; C is an empirical constant.

5. The method for calculating the heating performance of a vehicle high-voltage heater according to claim 1, characterized in that: When meshing, the shared topology enables the interface meshes between different regions of the automotive high-voltage heater model to share nodes.

6. The method for calculating the heating performance of a vehicle high-voltage heater according to claim 1, characterized in that: The heat transfer mode of the automotive high-voltage heater model is heat conduction, and its formula is: Where ρ is the density of the fluid; c p is the specific heat capacity of the fluid; T is the temperature; k is the thermal conductivity; Q is the internal heat source term.

7. The method for calculating the heating performance of a vehicle high-voltage heater according to claim 1, characterized in that: When performing simulation, the turbulence model selects the k-ε model, and the turbulence model formula is as follows: Where: G k is the turbulent kinetic energy caused by the mean velocity gradient; G b Used for the generation of turbulent kinetic energy caused by buoyancy; Y M is the factor affecting the total dissipation rate due to the compressible velocity turbulent pulsation expansion; μ t is the turbulent viscosity coefficient; C μ is the number that adjusts the relationship between the turbulent viscosity coefficient and the turbulent kinetic energy; x i is the spatial coordinate direction, used to describe the fluid position; μ is the dynamic viscosity of the fluid; σ k It is a dimensionless number that measures the relative size between the diffusion rate of turbulent kinetic energy and the dissipation rate of turbulent energy; ε is the dissipation rate of turbulent kinetic energy; C 1g , C 3g , C 2g is the number used in the turbulence model to adjust the effect of buoyancy on turbulence; The inlet condition is selected as mass flow inlet, and the outlet condition is selected as pressure outlet. The formula is: P out =P atm Where: P out is the outlet pressure; P atm is standard atmospheric pressure.

8. A method for calculating the heating performance of a vehicle high-voltage heater according to any one of claims 1 to 7, characterized in that: The formula for determining the heat transfer efficiency of the automotive high-voltage heater is: Where η is the heat transfer efficiency of the automotive high-voltage heater, ρ is the fluid density, C p is the specific heat capacity of the fluid, is the fluid volume flow rate, P is the heating power, T in is the liquid inlet temperature, T out is the liquid outlet temperature.

9. A computer device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that: When the processor executes the computer program, the method for calculating the heating performance of a vehicle high-voltage heater according to any one of claims 1 to 8 is implemented.

10. A computer-readable storage medium storing a computer program, characterized in that: When the computer program is executed by a processor, the method for calculating the heating performance of a vehicle high-voltage heater according to any one of claims 1 to 8 is implemented.

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