主动冷却点阵夹层防热结构温度响应计算模型北大核心CSCD

针对点阵夹层结构主动热防护问题,建立了夹层结构面板和芯体导热与冷却剂对流耦合的非稳态传热理论模型,利用有限体积法离散控制方程并在MATLAB中进行了迭代求解.模型首次考虑了面板与夹芯杆之间的收缩热阻,并利用分离变量法得到了收缩热阻的近似解析解.基于单胞模型和周期性边界条件,模拟得到了模型所需的表面对流传热系数h_(b)和h_(fin).最后,选取多单胞计算工况进行数值模拟和理论模型对比,并讨论了收缩热阻对模型预测精度的影响.结果表明:理论模型能够准确预测夹层结构及内部流体的温度变化,理论与仿真之间的最大误差不超过1%;随着外加热流密度不断增大,忽略收缩热阻使得计算结果造成的误差不断增大;与数值模拟相比,理论模型可显著地减少计算时间并节省计算资源,尤其适用于非均匀、非稳态复杂热载荷下点阵夹层结构的温度响应计算.

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

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 h_b and h_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.