A Flexible Pulsating Heat Pipe with Multiple Heat Transfer Branches

Flexible heat pipes are highly desired in many applications, such as human body thermal management, cooling of flexible electronic devices, and waste heat or renewable energy harvesting. In general, the thermal performance of flexible heat pipes is inversely proportional to flexibility. In this paper, a flexible heat pipe with multiple heat transfer branches was fabricated by Teflon tubes in the middle section and copper tubes in the heating and cooling sections based on the working principle of a pulsating heat pipe, which had both good thermal performance and flexibility. The experimental results showed that the thermal performance of the heat pipe decreased with increasing the bending angle or decreasing the inclination angle of the heat pipe. Furthermore, the apparent thermal conductivity of the proposed flexible heat pipe increased with the increasing heat power, which was up to 4333 W/(m·K) at the heat power of 24.6 W. In addition, as all the heat transfer branches had a large portion of the soft section (Teflon tube), they could deform independently with excellent flexibility. Therefore, the proposed flexible heat pipe can contribute to advanced thermal management and energy applications, which is beneficial to improve human thermal comfort as well as reduce fossil energy consumption and greenhouse gas emissions.