Guidelines for the Use of Aluminum Grooved Heat Pipes With Non-Negligible Gravity Effects

Thermal management of spacecraft is critical for a large range of applications in the space environment. From cold and stable temperature management, for example with scientific and observation purposes, to high power dissipation and high temperature requirements as for large telecom satellites, heat pipes are essential components along optimized, lightweight and effective thermal buses from the equipment to cool down to the radiative space environment. Extruded grooved aluminum heat pipes are long-term space qualified devices extensively used for decades. Aluminum grooved heat pipes filled with ammonia as working fluid are the most commonly used components. This technology is designed and optimized to operate in micro-gravity and the grooved design of the capillary wick is significantly affected by the gravity effects, on Earth and during lunar or planetary missions. With the aim of supporting the sub-system or satellite acceptance testing on Earth as well as providing useful guidelines to design grooved heat pipe based thermal buses for planetary missions, the proposed paper intends to analyze and explain the thermofluidic behavior of grooved heat pipes submitted to significative effects of external forces, like gravity. This analysis leads to several discussions and operational guidelines proposed to take advantage of external forces to design efficient thermal buses based on aluminum grooved heat pipes. On the top of the high thermal performance, gravity applications can beneficiate of highly qualified, lightweight and industrialized products to transport large amount of heat within many environment requirements.