Thermal characteristics of latent heat sinks based on low melting point metal and topologically optimized fins under lateral hypergravity

Abstract

With the increasing thermal load of optoelectronic equipment on aircraft, the method of using low melting point metals (LMPMs) instead of organic phase change materials (PCMs) to construct latent heat sinks has immense potential to solve the thermal control problem. However, aircraft are usually under hypergravity during maneuvering flight, and the thermal characteristics of latent heat sinks are likely to be different from those under normal gravity. Hence, the dynamic thermal characteristics of a latent heat sink with bismuth-based LMPM and topologically optimized fins under lateral hypergravity (0–6 g) were investigated with heat fluxes of 10–50 kW/m2. Compared with n-docosane, LMPM decreases the heating wall temperature by over 10 °C, and the holding time below specified temperatures (50, 60, and 70 °C) is prolonged by more than 50 %. Compared with the pin fin, the topologically optimized fin reduces the heating wall temperature by more than 4 °C maximum. The effect of hypergravity on the thermal performances of the heat sink with LMPM and topologically optimized fins is connected with the melting stage. It is negligible in the solid conduction stage and the initial stage of latent melting. It makes the heating wall temperature first increase and then decrease but always higher than that under normal gravity in the rest stage of latent melting. It causes the heating wall temperature to monotonically decrease with hypergravity in the liquid convection stage. The largest difference in heating wall temperature under various gravity occurs between 2 g and 0 g. It is 5.2 °C and its percentage is 7.6 % for 50 kW/m2. In addition, the effect of heat flux on thermal performances is not related to hypergravity.