Fabrication and performance evaluation of flexible flat heat pipes for the thermal control of deployable structure

In this work, we report the fabrication and thermal performance evaluation of flexible flat heat pipes by using laser ablated casing material with aluminum compound packing film and using gradient wetting functional copper meshes covered with nanowires as the wick structure. Deionized water was chosen as working fluid and three different filling ratios (20%, 30%, 40%) of working fluid were loaded into the heat pipe to investigate its impact on thermal performance. The fabricated flexible flat heat pipes can be bended from 0 degrees to 180 degrees in the horizontal operation mode and demonstrated consistently low thermal resistance of 0.525 degrees C/W or effective thermal conductivity of 1499 W/m . K after repeated bending. Simultaneously, theoretical analysis reveals that bending disturbs the vapor flow from evaporator to condenser in the flexible flat heat pipe, which leads to increased liquid-vapor interfacial thermal resistance in the evaporation section. The purpose of this study is to apply the flexible flat heat pipe to thermal control of deployable structures. (C) 2019 Elsevier Ltd. All rights reserved.