A water evaporator is a phase change heat exchanger, as a heat sink, especially for high-speed flight vehicles. It is composed of internal channels for convective cooling and external fins for boiling. In this paper, six water evaporators, Hex0–Hex5, are designed with five different internal channels and two different external fins. The VOF simulation models are built to investigate their boiling heat transfer performances in a sub-atmospheric environment. Experimental studies were carried out to verify the accuracy of the numerical model of water evaporator. The simulation results show that the structures of the internal channel and external fin both have an impact on the heat transfer performance. For the internal channels, their height change has much more obvious effect than their structural continuity. For the external fins, the increase of the fin bulge structure helps to improve the heat transfer performance. For the aircraft, the optimal design structure of water evaporator is Hex4 and its heat transfer performance can be improved by 13.31% compared with Hex0.

In this paper, the liquid cooling and vapor compression refrigeration system based on an Antifreeze-R134a Heat Exchanger (ARHEx) was applied to the thermal management system for high-power avionics in helicopters. The heat transfer performance of the ARHEx was studied. An experimental prototype of ARHEx was designed and established. A series of experiments was carried out with a ground experimental condition. A heat transfer formula for the antifreeze side in the ARHEx was obtained by means of the coefficient of Nusselt number with experimental analysis. The performance of heat transfer and pressure drop for the refrigerant side of the ARHEx was deduced for the given condition.