Novel mini loop heat pipe with twisted wires as wick structure

Abstract

In the present research, the twisted wires of a commercial flexible electrical cable were used as a novel wick structure of a mini loop heat pipe designed for cooling components in compact electronic gadgets. Besides being cheap and easy to manufacture, this porous medium presents good thermal performance, with permeability of around 1.76 x 10^-10 m² and porosity of 45.63 %. The studied wick was installed inside a mini loop heat pipe of 76 x 60 x 1.1 mm³. The thermal performance of the device was experimentally evaluated, showing excellent heat transfer capacity when compared to similar literature loop heat pipes with conventional wicks, being able to remove up to 9 W/cm² in all tested orientations (horizontal, gravity assisted, and against gravity). The lowest thermal resistance achieved was 0.26 ± 0.04 °C/W, in the horizontal position. Considering the safety operation condition of electronic gadgets, most of the experiments were finished when the evaporator achieved temperatures of up to 100 °C. However, the device was able to transfer up to 12 W/cm², if higher evaporator temperatures were allowed, when the capillary limit was reached, as predicted by a literature-based model. Compared to other more conventional wicked mini loop heat pipes from the literature, the present device was able to transfer similar or higher heat. Due to its great flexibility, the wick is easily adaptable and can be applied to other wicked two-phase technologies.