Design, fabrication and heat transfer performance study of a novel flexible flat heat pipe

Abstract

In this work, a novel flexible flat heat pipe (FFHP) is developed to dissipate high heat flux in flexible electronic devices. Its evaporation section and condensation section are made of metal cavity structure to guarantee good heat conduction, and flexible copper foil is used as the shell material of the adiabatic section to improve the overall flexibility. Spiral woven mesh adhered to a coarse copper mesh is selected as the liquid-wicking structure due to its excellent flexibility and strong capillary force, and the coarse copper mesh serves as a supportive structure. Deionized water is chosen as the working fluid. A feasible manufacturing process is also proposed. The effects of different liquid filling ratios (30%, 40%, 50%), bending curvature diameters (20 mm, 25 mm, 30 mm), and bending angles (0° ∼ 180°) on the heat transfer performance of the FFHP are investigated. Experimental results demonstrate that the FFHP with the optimum liquid filling ratio of 40% can transport heat up to 25 W in the horizontal operation state with a minimum thermal resistance of 0.99 K/W. Moreover, the FFHP can be bent from 0° to 180°. When bent to 180° with a curvature diameter of 30 mm, it still can transport a maximum heat of 15 W.