Operating characteristics of a new ultra-thin loop heat pipe

This paper presents a new cooling solution for thermal management using an ultra-thin loop heat pipe (LHP) with an evaporator of 0.6-mm thickness designed to be embedded in thin electronic devices. A prototype model of thin LHP was fabricated using chemical etching of thin copper plates and a diffusion-bonding process. The experimental investigation was conducted by measuring the temperature of each part of the thin LHP against the heat input to evaluate the heat transport performance of the thin LHP. Thermal resistance between the evaporator and the condenser of 0.11 K/W for a horizontal orientation, 0.03 K/W for a bottom heat orientation, 0.28 K/W for a top heat orientation was obtained at 20 W. It was confirmed that there is little dependence of the operating orientation on the thin LHP, which is capable of transferring a heat load of 20 W even in different orientations. A three-dimensional heat conduction analysis for the evaporator was carried out. From these calculations, the heat distribution in the evaporator and the quantity of heat leakage from the evaporator to the liquid line during steady operation was ascertained. The result of this investigation shows that the proposed LHP is a promising option for the thermal management of mobile electronics.