A Calculation Model for Temperature Responses of Active Cooling Lattice Sandwich Structures for Thermal Protection

Abstract

Aimed at the active thermal protection with lattice sandwich structures, an unsteady heat transfer theoretical model coupling facesheet and core heat conduction with coolant convection in the sandwich structure, was established. The model equations were discretized with the finite volume method and solved iteratively in MATLAB; the constriction thermal resistance between the facesheet and the lattice struts was considered for the first time in the model, and the approximate analytical solution of the constriction thermal resistance was obtained with the variable separation method; based on the unit-cell model and periodic boundary conditions, heat transfer coefficients <i>h</i>_b and <i>h</i>_fin required by the model were first obtained through numerical simulation. Finally, a case study with a multi-cell structure was carried out to compare the numerical and theoretical results, and the influence of the constriction thermal resistance on the prediction accuracy was discussed. The results show that, the theoretical model can accurately predict the temperature variations of the sandwich structure and the internal fluid, and the maximum deviation between theory and simulation is less than 1%. As the external heat flux increases, the error of theoretical prediction rises with the constriction thermal resistance ignored. Compared with the numerical simulation, the theoretical model can significantly reduce the calculation time and save calculation resources, thus it is especially suitable for active cooling lattice sandwich structures subjected to complex, non-uniform and unsteady thermal loads.