Thermal protection characteristics of non-enclosed thermal cloak

Abstract

The aerodynamic heat of hypersonic vehicle nose cone can reach tens of MW/m<sup>2</sup> during flight, which could be transferred to the interior of hypersonic vehicle in the form of conduction and radiation. High efficient thermal insulation technology is of significance in keeping internal electronic components working safely. Thermal metamaterials can regulate the macroscopic heat flow path, and they are developing rapidly and have a wide application prospect in the field of thermal protection. In this work, a non-enclosed point transformation thermal cloak is designed to guide heat flow around hypersonic vehicle nose cone by using the transformation multithermotics, which can control thermal conduction and radiation simultaneously. A multi-layer structure is designed as cloak’s simplified approximation due to the anisotropic parameters. Based on the software COMSOL, the thermal protection characteristics and heat transfer mechanism of the point transformation cloak and multi-layer structure are studied numerically. The results show that heat can flow around the object in the form of conduction and radiation in both point transformation thermal cloak and multi-layer structure, so the heat transferred to the inner area decreases. Comparing with the thermal insulation material, the heating rate of the protected area slows down, and the temperature in the front of the hypersonic vehicle nose cone is significantly reduced. However, the improvement of the thermal protection performance of point transformation cloak and multi-layer structures requires that the solid thermal conductivity and radiative thermal conductivity of the material are lower than those of the original thermal insulation material. To solve this problem, a non-enclosed region transformation thermal cloak is further proposed. The solid thermal conductivity and radiative thermal conductivity of region transformation thermal cloak are non-singular, which could be higher than those of the original thermal insulation material. Numerical simulation results show that the region transformation thermal cloak can guide heat flow around object, so the thermal protection capability is improved significantly. Comparing with the thermal insulation materials, the temperature of the front of the hypersonic vehicle nose cone is reduced by 100 K, and the temperature of the inner central zone of the hypersonic vehicle nose cone is reduced by 10 K. The non-enclosed region transformation thermal cloak provides a new approach to realizing thermal protection and is suitable for complex target areas, showing great application potential in thermal protection.