平板热管多孔毛细芯等效导热系数预测

In this paper, a porous capillary wick in a vapor chamber is used as a research specimen and the influencing factors of effective thermal conductivity of the wick are theoretically analyzed. Based on the microstructure of the wick, which is randomly distributed with solid phase connection, three-dimensional diffusion limited aggregation models are reconstructed in this paper. The thermal conductivity of the gas in the confined space is calculated and the heat transfer characteristics under steady-state heat conduction are studied using numerical simulation. The results show that the thermal conductivity of the gas in the confined space is much lower than that in the free space, which is only 0.00986 W/(m K) under the atmospheric pressure. Besides, the thermal conductivity of the solid phase is 0.9 times that of the bulk material. The influence of different parameters on the effective thermal conductivity of the porous media is analyzed. The results show that the effective thermal conductivity of the capillary wick decreases with the increase in porosity, and the smaller the particle diameter is, the more significant is the trend. When the particle diameter is 40 μm and porosity is 0.4, the effective thermal conductivity is 12.14 W/(m K), which is about three times the corresponding thermal conductivity (3.89 W/(m K)) when the porosity is 0.7. The particle diameter also has a significant effect on the thermal conductivity of the porous capillary wick. In the case of small porosity, the effective thermal conductivity decreases with the increase in particle diameter, while in the case of larger porosity, the trend is opposite. The effective thermal conductivity of the capillary wick with porosity of 0.5 has deviation of 12.1% from the experimental value, which shows good adaptability of the proposed model.