Lattice Boltzmann Simulation of Flow Heat Transfer in Complex Pores with Hierarchical Structure

Based on the D3Q19 lattice Boltzmann method (LBM) and within the application context of transpiration cooling technology, this study investigates the influence of the pore structure and thermophysical parameters of a hierarchical porous medium on the temperature field. The layered pore structure is reconstructed using spherical particle packing and random generation methods. The temperature distribution and heat transfer characteristics under the effects of porosity, solid thermal conductivity, layer thickness ratio, and the number of layers are calculated and analyzed. The results show that a larger porosity along the flow direction leads to a faster temperature rise rate in the solid matrix of the porous medium. The solid temperature within pores of a structure with a sparse upper layer and a dense lower layer is lower than that of a structure with a dense upper layer and a sparse lower layer. Furthermore, a greater difference in the solid thermal conductivity between the two layers results in lower solid temperature and a slower rate of temperature change within the pores. Compared to a pore structure where the dense upper part constitutes a larger thickness proportion, a smaller proportion of the sparse upper part leads to a lower temperature within the pores. When the number of layers in the hierarchical structure does not exceed five, increasing the layer count can reduce the temperature of the heat exchange medium. However, when the number of layers exceeds five, the internal solid temperature of the porous medium increases instead.