Study of the heat transfer design of an integrated thermal management system for hypersonic vehicles using supercritical nitrogen as expendable coolant

Abstract

Nitrogen has been widely used as an expendable coolant in aviation and aerospace fields to cool the high-temperature components in a thermal management system. This paper presents a concept of a thermal management system for hypersonic vehicles that integrates various cooling technologies using supercritical nitrogen as heat sink. Since the thermophysical properties of supercritical nitrogen vary acutely with temperature, existing heat transfer empirical models fail to accurately evaluate the heat transfer coefficient of supercritical nitrogen during the parameter design of the thermal management system. Therefore, a new correlation specialized for supercritical nitrogen is proposed relying on a heat transfer experimental database including 784 data points compiled from seven published papers and the computer optimized dimensionless groups, which commendably solve the considerable deviation caused by the thermophysical property distortion and buoyancy effect. The new correlation has a mean absolute deviation (MAD) of 3.9% and improves the prediction accuracy of supercritical nitrogen heat transfer calculation remarkably by predicting 94.9% of the entire database within ±10% error band, based on which the heat transfer design method of the integrated thermal management system is discussed.