To bend or not to bend: Impact on heat pipe performance

Thermal management of electronics continues to be a dominant factor that needs attention already early in the design phase. Within complex systems, typically a battle for space is imminent due to the multidisciplinary nature. In this respect, the use of low-form-factor phase-Transitional devices is standard industry practice nowadays. In particular, heat pipes have demonstrated high heat transfer rates, due to the utilization of a working fluid's latent heat in combination with reliable, small and lightweight designs. Heat pipes are employed in electronics cooling in which they are often bent and operated under different perating conditions. This study aims to investigate how heat pipes function when bent at various angles and inclinations. The impact of various bending angles (no bend, 30° bend, 2x30° bend, 45° bend, 2x45° bend and 90° bend) and inclination angles (horizontal, ±45° and ±90°) is examined. Bending losses and an associated theoretical model are validated for sintered-wick heat pipes. Heat pipe bending has minimal effect on the thermal performance as long as the bending angle does not exceed 45°. It is however important to consider gravity when operating bent heat pipes outside the horizontal plane.