Design and thermal analysis of a high-performance flexible heat pipe with all-directional bending

Abstract

Based on two-phase heat transfer, flexible heat pipes have great engineering applications and broad prospects in the fields of flexible electronics, wearable electronic devices, and smart textiles. However, high flexibility remains a great challenge in practical applications. Herein, a high-performance flexible heat pipe with all-directional bending has been designed and fabricated, which can be easily bent from 0° to 360°. Polypropylene bellows, which are easy to bend and scalable, are used as the adiabatic section for connecting two rigid copper tubes. Flexible superhydrophilic copper meshes with nanostructured surfaces are employed as their inner wicking structure to circulate the liquid in the pipe. It is found that an optimal filling ratio of 30 % exists in this pipe. Under this condition, the minimum thermal resistance reaches 0.32 K/W when transferring a heat load of 12.0 W. As this flexible heat pipe is bent through a full 360° turn, its minimum thermal resistance can reach 0.89 K/W. Following extensive long-term testing, this flexible heat pipe continues to retain outstanding flexibility and remarkable heat transfer properties. These findings proposed in this work can offer efficient thermal management solutions for flexible electronics, electric vehicle battery modules, robotic articulation systems, and optimize the design of electronic systems in confined spaces.