Experimental study on the heat transfer performance of a gravity-assisted separated heat pipe for high-power chip cooling

With increasing thermal management demands in data centers, this study proposes a miniaturized gravity-assisted separated heat pipe system for chip cooling that enhances energy efficiency, reduces structural complexity, and ensures operational durability. Experiments examined the effects of working fluid, filling ratio, evaporator structure, and installation method on thermal performance. Results demonstrate that the horizontal condenser layout promotes stable unidirectional fluid circulation. The dual-fan configuration improves the maximum heat dissipation capacity and lowers temperature. For this system, precise control of the filling ratio is crucial to prevent failure and degradation of thermal performance. High surface tension and boiling point can cause temperature oscillations, which can be alleviated by reducing microchannel height and utilizing the saved space as vapor and liquid collection chambers. Incorporating partition to guide the working fluid through the channels further mitigates temperature oscillations and improves heat transfer performance. Several design methods maintain the heat pipe operating temperature below 75 °C, under the conditions of a heating power of 350 W and a cooling power of 5 W. The optimal option horizontal dual-fan, 4 mm partition width, SF 33 as the working fluid, and 70 % filling ratio achieves a maximum temperature of 70.3 °C and an equivalent thermal resistance of 0.11 °C/W.