Influence of heat transfer path In the initial design, there is no contact between the heat sink and the case, and the heat generated by the CPU is completely transferred to the case by convection in the closed cavity. In the improved design, thermal grease was added between the heat sink and the housing. The heat transfer methods and paths of the two structures are different. Without silicone grease, the heat generated by the CPU is dissipated in natural convection and transferred to the housing. Due to the low heat exchange efficiency, a large temperature gradient is generated between the component and the air. The CPU temperature is as high as 155 ° C, which exceeds the component's Withstand range. When there is thermal grease, part of the heat generated by the CPU is transferred to the PCB, causing the temperature of the board and chips in the surrounding area to increase, and most of the heat is directly transferred to the device case through the silicone grease, and the temperature of the component Significantly decreased to only 49 ℃, indicating that the heat transfer path and method have a significant effect on the heat distribution of electronic products.
The temperature of the area where the device casing contacts the thermal grease is the highest, and the farther away, the lower the temperature. However, due to the good thermal conductivity of the shell material, the temperature gradient across the shell surface is not large, and the maximum temperature difference is only about 1.2 ° C. The heat transfer path and method only slightly affect the temperature distribution, and the maximum temperature of the housing is basically the same. Analyze the influence of thermal conductivity of silicone grease and ambient temperature. It can be seen that the thermal conductivity has a significant effect on the temperature of the CPU. Increasing the thermal conductivity of the silicone grease can increase the heat transferred to the housing through direct thermal conduction, effectively reducing the CPU temperature. The temperature of the CPU and the housing increases linearly with the increase of the ambient temperature. When the ambient temperature is 40 ° C, the CPU temperature reaches about 70 ° C, which still meets the working temperature requirements.
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