Numerical analysis of the mechanism of porosity effect on the thermal-hydraulic performance of Gyroid-type TPMS structures in combined aero engines

Gyroid-type Triply Periodic Minimal Surface (TPMS) heat exchanger, with its high heat transfer rates and lightweight design capacity, is well-suited for next-generation combined aero engines. However, current studies have focused on the analysis of different cell sizes, and little has been done on the analysis of porosities, which is important to analyze power-to-weight ratio in aerospace field. In the present research, thermal-hydraulic performances of Gyroid structures with different porosities from 60 % to 80 % are investigated under aero engines working conditions through numerical method. The Q and k in the structure with 60 % porosity individually increases 83 % and 72 % of that in the structure with 80 % porosity, while the pressure drop in cold and hot side will increase 5.94 and 1.80 times. Wall shear stress, turbulent kinetic energy and velocity inhomogeneity characteristics are analyzed to clarify the mechanism of porosity on heat transfer performance. Novel thermal-hydraulic correlations that including porosity parameter are derived from 240 data points using the leastsquares method, and the correlations have an average error of 5.73 % in Nuf and an average error of 9.48 % in ff,which are able to guide the design of aero engines. The results show that smaller porosity will not only bring large specific area, but also provide a large heat transfer coefficient, for it can significantly homogenize the velocity distribution and increase wall shear stress and turbulent kinetic energy.