Three-dimensional Thermal Network Analysis of Multi-stage Heat Sink with Water-mist Injection Applied to Thermal Management of Electric Aircraft

Electrification of aircraft has been realizing improvement in efficiency, reliability, and safety of the aircraft by substituting hydraulic and mechanical system with electric system. On the other hand, in future electric aircraft partially replacing the fan driving engines with motors, the thermal management of heat generation from the electric system will become crucial problem to be solved. In this study, for the future electric aircraft, thermal management in oil-cooling motors and air-cooling motor controllers was considered. Three-dimensional steady thermal network analysis (TNA) was performed for analyzing temperature field in an oil cooler for motor cooling and a heat sink for motor controller air-cooling. The present numerical procedure was verified by comparing the results of TNA with those of three-dimensional fluid-solid conjugate heat transfer analysis (3D-CFD). After the verification, TNA was performed for several aircraft flight scenarios, and the optimum geometry of the oil cooler and the heat sink was investigated under the constraints of allowable pressure loss of air flow and outlet oil temperature for oil cooler or maximum local wall temperature for heat sink using the weight (mass) as the object function to be minimized. Furthermore, the water-mist injection to the air flow was considered for lowering the air temperature and the weight of the heat sink.