Research on the boundary conditions of electronic equipment. In a closed system, the heat generated by the operation of electronic equipment is eventually lost through convection heat exchange between the shell and the external environment. The calculation domain should include both internal and external parts. However, the establishment of both internal and external domain numerical models not only increases the modeling workload, but also has low computational efficiency. The outer wall surface of the shell is regarded as a hot plate placed in the environment. According to the heat transfer theory, the convection heat transfer coefficient of the outer wall surface is calculated and set to simulate the heat exchange process between the equipment and the environment, so that only the equipment needs to be built. The numerical model of the flow field and solid domain of the cavity, the number of grids and the calculation workload are significantly reduced.
Regardless of the protruding part of the surface, the calculation formula of the heat flux between the outer wall of the shell and the environment is: Q = Ah (T-TW). Among them, Q is the heat flux, T is the external ambient temperature, TW is the surface temperature of the plate, and A is the area of ​​the plate. Establish a coupled analysis model containing the flow field and solid domain. The shell material is made of aluminum with good thermal conductivity, with a thickness of 4mm. Other components with small geometric dimensions and little influence on heat transfer and flow are not considered in the modeling. Since the buoyancy-driven flow has an important influence on the calculation results, the grid spacing is smaller in the direction of gravity, while the grid spacing in the horizontal direction is relatively larger.
In order to increase the simulation accuracy, the local heating grid is encrypted in the three-dimensional area around the main heating element CPU and its adjacent PCB board. The total number of grids in the calculation model is about 300,000. Boundary condition calculation example There are six outer wall surfaces of the equipment case. Among them, four wall surfaces can be regarded as vertical plates, the upper wall surface is a flat plate with a heating surface facing upward, and the lower wall surface is a flat plate with a heating surface facing downward. According to the theory of heat transfer, the convective heat transfer coefficient of each face is related to the placement.
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