A pressure and flow simulation method for water cooling system based on component flow resistance characteristics

Abstract

The present invention discloses a method for simulating the pressure and flow of a water-cooling system based on the flow resistance characteristics of a component. The method relates to the field of simulation of the pressure and flow of a water-cooling system, and uses a curved pipe and multiple porous pressure jump surfaces to replace the modeling of the water-cooling base plate and the radiator pipeline; the equivalent pipeline is connected to the main pipeline system as the overall pressure and flow simulation of the pipeline system; the formula and method for setting the simulation parameters of the porous pressure jump surface are calculated based on the flow resistance curve of the water-cooling base plate and the radiator provided by the supplier. Compared with the traditional water-cooling base plate modeling, the present invention greatly reduces the number of grids, significantly shortens the simulation cycle, and greatly improves the simulation efficiency; uses three-dimensional finite element simulation for the entire pipeline system outside the water-cooling base plate, significantly improving the calculation accuracy of the pressure loss of the main pipeline system, and also improving the calculation accuracy of the flow distribution of each module; after the simulation is completed, the pressure and flow at any point in the pipeline system are observed through a cloud map, providing a detailed and accurate reference basis for the design and selection of the water-cooling pipeline system.

Description

Technical Field

[0001] The present invention relates to the field of simulation of pressure and flow of a water cooling system, and in particular to a method for simulating pressure and flow of a water cooling system based on flow resistance characteristics of components. Background Art

[0002] The switching devices of a traction converter generate power losses during operation. Due to the high heat generation and heat density of the switching devices, water cooling solutions are usually used to ensure heat dissipation of the switching devices. The switching devices are usually integrated into the power module. The heat loss of the power module is transferred to the coolant in the system through the water-cooled baseplate. The coolant is driven by a water pump to flow through the cooling system pipes, transferring the heat to the radiator. At the same time, in the cooling air duct, the cooling fan drives the external cooling air and the radiator for heat exchange. After the water-cooling piping scheme is designed, it is usually necessary to simulate the piping system to determine the pressure distribution at each point in the piping system and the coolant flow rate flowing through the water-cooled baseplate of each power module to verify the feasibility and rationality of the piping system.

[0003] With the development of computer technology, the use of finite element method for calculation of more complex flow field problems is an economical and reliable method. Fluent software has a more suitable numerical solution for the flow characteristics of each physical problem. It has the advantages of fast calculation speed, high stability, high calculation accuracy and fast convergence speed. It has a relatively rich physical model library and can more accurately simulate various complex flow processes such as laminar flow and turbulent flow. The accompanying Fluent meshing is a meshing tool for fluid mechanics and heat transfer. The meshing method is flexible and can divide unstructured grids of various shapes. Fluent software is a general CFD solver for unstructured grids. The flexible unstructured grid division can adapt to flows with large parameter changes and large gradient changes in the fluid field.

[0004] In the prior art, there are CFD simulation technologies based on computational fluid dynamics, such as ANSYS Fluent software. The specific solution is: using one-dimensional simulation, the various parts of the pipeline system are segmented, and the relationship between the pressure and flow of each section of the pipeline is estimated based on the empirical formula. Then, based on the pipeline topology, the "road" method is used to solve the pressure loss in each section of the pipeline and the flow distribution of each water-cooled base plate when the pipeline system is running in a steady state; using three-dimensional finite element simulation, the internal fluid areas of the main pipeline system and water-cooled base plates, radiators and other components are CFD simulated to obtain the pressure value at any point in the pipeline and the flow distribution of each water-cooled base plate when the pipeline system is running in a steady state. However, this technical solution has the following defects:

[0005] 1) The calculation of pressure loss in one-dimensional simulation pipelines is based on empirical formulas. However, water-cooling pipelines are often complex, and it is difficult to ensure the accuracy of simulation calculations by relying on simple empirical formulas to handle complex pipelines.

[0006] 2) 3D finite element simulation requires modeling the fluid region within the entire piping system, including the internal piping of each water-cooled baseplate and radiator. Because the internal flow paths of the water-cooled baseplate and radiator are complex and their scale differs significantly from the main piping, using this method to simulate the entire complex piping system will result in a huge total mesh count, increasing the simulation difficulty and workload. It also places high demands on the computer configuration to run the simulation, resulting in long simulation times and low efficiency.

[0007] 3) Due to commercial confidentiality and other reasons, water-cooled baseplate and radiator manufacturers are often unable to provide 3D models of the internal flow channels of the water-cooled baseplate and radiator. In this case, 3D finite element simulation of the piping system cannot be performed due to the lack of an accurate model.

[0008] Based on the above defects, it is necessary to improve the simulation method in the existing water cooling pipeline design to solve the above problems. Summary of the Invention

[0009] In order to solve the problem of using three-dimensional finite element method to simulate and analyze the pressure at any point in the main line and the flow distribution of each water-cooling base plate when the main line in the existing water-cooling system is relatively complex and there is no water-cooling base plate and radiator internal piping model, the present invention provides a water-cooling system pressure and flow simulation method based on the flow resistance characteristics of the components.

[0010] The present invention is achieved through the following technical solution: a water cooling system pressure and flow simulation method based on the flow resistance characteristics of components, using Fluent software for field-circuit coupling simulation, including the following steps:

[0011] 1) Modeling of the main pipeline system and the equivalent pipeline of the water-cooled baseplate:

[0012] Model the fluid area in the pipeline based on the actual 3D model. The equivalent pipeline of the water-cooled baseplate is made into a bend with the same diameter as the interface. Both ends of the bend must be tightly connected to the main pipeline system. One or more sections are set in the bend for backup.

[0013] 2) Water-cooled baseplate equivalent pipeline replacement:

[0014] In Fluent software, one or more sections in (1) are set as "Porous-jump" surfaces, i.e., porous pressure jump surfaces. The initial default values ​​of the parameter setting interface are: Zone Name is automatically named by the software, Phase is mixture, Face Permeability (m2) is 10000000000; Porous Medium Thickness (m) is 0; Pressure-Jump Coefficient (C2) (1 / m) is 0, Thermal Contact Resistance (m2-k / w) is 0; Figure 1 As shown;

[0015] 3) Calculation and setting of equivalent pipeline parameters:

[0016] The flow resistance curves provided by the water-cooling base plate and radiator base plate manufacturers are fitted with a quadratic polynomial. The pressure loss unit of the fitting curve is Pa and the flow unit is m 3 / s, the quadratic coefficient of the pipeline flow resistance curve obtained by fitting is a, and the linear coefficient is b;

[0017] If the equivalent pipe cross-sectional area is S, the number of cross sections in the elbow is set to N, the fluid viscosity is μ, the fluid density is ρ, the porous medium thickness is set to h, and all parameter units are converted to the international system of units, then the surface permeability α and the resistance coefficient C2 should be calculated and set according to the following formula:

[0018] (1)

[0019] (2)

[0020] The equivalent pipe bend itself also has a certain flow resistance, but this resistance is usually very small compared to the water-cooled baseplate. If the simulation accuracy is high or the resistance coefficient of the water-cooled baseplate itself is relatively small, the porous medium thickness setting value h can be modified as follows:

[0021] First, simulate and calculate the pressure loss P of the equivalent pipeline at the rated flow rate. The resistance P0 of the water-cooled base plate at the rated flow rate is found on the flow resistance curve. The thickness of the porous medium can be changed to h1. The calculation formula is as follows:

[0022] (3)

[0023] 4) Simulation solution of the entire piping system:

[0024] According to the actual working conditions, the remaining simulation boundary conditions and material physical property parameters of the pipeline are set in Fluent, and the simulation is run. When the pressure and flow in the pipeline fluctuate very little with the number of iterations and reach a threshold (this threshold is selected by technical personnel in this field based on actual application), the simulation is completed, and the pressure distribution and flow distribution of the entire pipeline system can be obtained.

[0025] Compared with the prior art, the present invention has the following beneficial effects: the present invention provides a pressure and flow simulation method for a water cooling system based on the flow resistance characteristics of components:

[0026] 1) Using 3D finite element analysis for all main pipes in the piping system can more accurately calculate the pressure loss along the coolant flow in pipes with relatively complex shapes and structures. After the 3D finite element simulation is completed, the pressure and flow at any point in the main pipe can be obtained, providing sufficient data and basis for the design and improvement of the piping system.

[0027] 2) When the supplier does not provide a water-cooling baseplate model, only the water-cooling baseplate flow resistance curve can still be provided to complete the pressure and flow three-dimensional finite element simulation analysis of the entire piping system;

[0028] 3) Since the external characteristics of the water-cooled baseplate equivalent pipeline simulation model are directly derived from measured data, the accuracy of the flow and pressure simulation within the main pipeline system is higher than that of finite element analysis after direct modeling of the water-cooled baseplate;

[0029] 4) Compared with traditional water-cooled baseplate modeling, the number of grids is greatly reduced, which significantly shortens the simulation cycle and greatly improves simulation efficiency;

[0030] 5) Using three-dimensional finite element simulation for the entire piping system outside the water-cooled baseplate can significantly improve the calculation accuracy of the main piping system pressure loss, while also improving the calculation accuracy of the flow distribution of each module;

[0031] 6) After the simulation is completed, the pressure and flow at any point in the piping system can be observed through the cloud map, providing a detailed and accurate reference for the design and selection of the water cooling piping system. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 An interface is provided for the porous pressure jump surface of the present invention.

[0033] Figure 2 It is a flow chart of the simulation process of the present invention.

[0034] Figure 3 This is the water cooling pipeline system model of the present invention.

[0035] Figure 4 This is an equivalent diagram of the water-cooling pipeline system model of the present invention.

[0036] Figure 5 It is a schematic diagram of pipeline pressure cloud map and flow rate (L / min) distribution. DETAILED DESCRIPTION

[0037] The present invention will be further described below with reference to specific embodiments.

[0038] The simulation tasks and working conditions described in this embodiment are as follows:

[0039] (a) Given a water cooling pipe system model of a converter cabinet, Figure 3 As shown (there is no detailed model inside the water-cooling baseplate and radiator model);

[0040] (b) Measured curves of coolant flow resistance characteristics of known water-cooled radiators and water-cooled baseplates;

[0041] (c) The physical parameters of the pump, such as the flow-head curve, viscosity coefficient and density of the coolant, are known;

[0042] (d) Through simulation, the pressure distribution in the water-cooling main line and the flow distribution of each water-cooling radiator and water-cooling base plate are obtained.

[0043] The model processing and parameter setting methods of this embodiment are as follows:

[0044] The simplified model components and component guide diagram of the water cooling pipeline are as follows Figure 4 As shown in the figure, this model is based on the engineering model and has been simplified and modified to meet the requirements of CFD analysis. The water-cooled baseplate, radiator, and environmental control device are replaced with elbows with very low flow resistance (the parts pointed by the arrows in the figure).

[0045] Add a zero-thickness surface in the middle of the elbow (the black line in the middle of the part pointed by the arrow), and set the zero-thickness surface as the porous-pressure jump boundary condition; all porous-pressure jump parameters are set according to the following steps and methods to set the α, h, and C2 values ​​so that this section of the pipeline has the same flow resistance curve as the original part. The step flow chart is shown in the figure below. Figure 2 The specific steps are as follows:

[0046] 1) Modeling of the main pipeline system and the equivalent pipeline of the water-cooled baseplate:

[0047] Model the fluid area within the pipeline based on the actual 3D model. The equivalent pipeline of the water-cooled baseplate is made into a bend with the same diameter as the interface. Both ends of the bend must be tightly connected to the main pipeline system, and a section is set in the bend for backup.

[0048] 2) Water-cooled baseplate equivalent pipeline replacement:

[0049] In Fluent software, the section set in (1) is set as the "Porous-jump" surface, that is, the porous pressure jump surface. The initial default values ​​of its parameter setting interface are: Zone Name is automatically named by the software, Phase is mixture, Face Permeability (m2) is 10000000000; Porous Medium Thickness (m) is 0; Pressure-Jump Coefficient (C2) (1 / m) is 0, Thermal Contact Resistance (m2-k / w) is 0; Figure 1 As shown;

[0050] 3) Calculation and setting of equivalent pipeline parameters:

[0051] The flow resistance curves provided by the water-cooling base plate and radiator base plate manufacturers are fitted with a quadratic polynomial. The pressure loss unit of the fitting curve is Pa and the flow unit is m 3 / s, the quadratic coefficient of the pipeline flow resistance curve obtained by fitting is a, and the linear coefficient is b;

[0052] If the equivalent pipe cross-sectional area is S, the number of cross sections in the elbow is set to N, the fluid viscosity is μ, the fluid density is ρ, the porous medium thickness is set to h, and all parameter units are converted to the international system of units, then the surface permeability α and the resistance coefficient C2 should be calculated and set according to the following formula:

[0053] (1)

[0054] (2)

[0055] Considering that the equivalent pipe bend itself also has a certain flow resistance, the porous medium thickness setting value h is corrected to improve the simulation accuracy:

[0056] First, simulate and calculate the pressure loss P of the equivalent pipeline at the rated flow rate according to the above method. The resistance P0 of the water-cooled base plate at the rated flow rate is found on the flow resistance curve. The thickness of the porous medium is changed to h1. The calculation formula is as follows:

[0057] (3)

[0058] 4) Simulation solution of the entire piping system:

[0059] According to the actual working conditions, the remaining simulation boundary conditions and material physical property parameters of the pipeline are set in Fluent, and the simulation is run. When the pressure and flow in the pipeline fluctuate very little with the number of iterations and reach a threshold, the simulation is completed, and the pressure distribution and flow distribution of the entire pipeline system can be obtained.

[0060] The simulation boundary conditions of this embodiment are set as follows:

[0061] The water pump inlet is set as the pressure outlet, and the gauge pressure is 0; the water pump outlet is set as the velocity inlet, and the flow rate is determined by comparing the simulation results with the water pump curve (approximating the curve through multiple simulation iterations). The pipeline pressure cloud and flow distribution diagram obtained after the simulation are shown in the figure below. Figure 5 shown.

[0062] The scope of protection claimed by the present invention is not limited to the above specific embodiments. For those skilled in the art, the present invention may have various variations and modifications. Any modifications, improvements and equivalent substitutions made within the concept and principle of the present invention should be included in the scope of protection of the present invention.

Claims

1. A pressure and flow simulation method for a water cooling system based on the flow resistance characteristics of components, characterized by: Fluent software is used to perform field-circuit coupling simulation, which includes the following steps: 1) Modeling of the main pipeline system and the equivalent pipeline of the water-cooled baseplate: Model the fluid area in the pipeline based on the actual 3D model. The equivalent pipeline of the water-cooled baseplate is made into a bend with the same diameter as the interface. Both ends of the bend must be tightly connected to the main pipeline system. One or more sections are set in the bend for backup. 2) Water-cooled baseplate equivalent pipeline replacement: In Fluent software, set one or more sections in 1) as "Porous-jump" surfaces, i.e., porous pressure jump surfaces. The initial default values ​​of the parameter setting interface are: Zone Name is automatically named by the software, Phase is mixture, Face Permeability (m2) is 10000000000; Porous Medium Thickness (m) is 0; Pressure-Jump Coefficient (C2) (1 / m) is 0, and Thermal Contact Resistance (m2-k / w) is 0; 3) Calculation and setting of equivalent pipeline parameters: The flow resistance curves provided by the water-cooling base plate and radiator base plate manufacturers are fitted with a quadratic polynomial. The pressure loss unit of the fitting curve is Pa and the flow unit is m 3 / s, the quadratic coefficient of the pipeline flow resistance curve obtained by fitting is a, and the linear coefficient is b; If the equivalent pipe cross-sectional area is S, the number of cross sections in the elbow is set to N, the fluid viscosity is μ, the fluid density is ρ, the porous medium thickness is set to h, and all parameter units are converted to the international system of units, then the surface permeability α and the resistance coefficient C2 should be calculated and set according to the following formula: (1) (2) If the simulation accuracy is high or the resistance coefficient of the water-cooled substrate itself is relatively small, the porous medium thickness setting value h can be corrected as follows: First, simulate and calculate the pressure loss P of the equivalent pipeline at the rated flow rate. The resistance P0 of the water-cooled base plate at the rated flow rate is found on the flow resistance curve. The thickness of the porous medium can be changed to h1. The calculation formula is as follows: (3) 4) Simulation solution of the entire piping system: According to the actual working conditions, set the remaining simulation boundary conditions and material physical property parameters of the pipeline in Fluent and run the simulation. When the pressure and flow in the pipeline fluctuate very little with the number of iterations and reach a threshold, the simulation is completed, and the pressure distribution and flow distribution of the entire pipeline system can be obtained.

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