Additive-manufactured flat-plate copper pulsating heat pipe for three-dimensional heat spreader

Abstract A typical thermal management solution for miniaturized electronic devices with high heat flux is to integrate the heat spreader. Taking advantage of the thin and wickless, simple structure of Pulsating Heat Pipes (PHPs), several studies proposed flat-plate PHPs for this application. In most studies, the evaporator and the condenser are located at both ends of the PHP. However, in practical use, the PHP should spread a centrally located heat source in a three-dimensional direction, achieving high-temperature uniformity in a limited space. In this study, a PHP is proposed for spreading the heat of devices with high heat flux up to 50 W/cm2, and its thermal performance was experimentally investigated. The present PHP is novel also in terms of its design and fabrication: a spiral-shaped channel instead of a typical horizontal channel to facilitate not only in-plane but also out-of-plane heat spreading; additive manufacturing of pure copper with laser powder bed fusion process to make spiral-shaped channels. To the authors' knowledge, this is the first additively manufactured copper PHP. Methanol was used as the working fluid. By varying the filling ratio, the optimal range was determined to be between 39% and 59%. The thermal performance was evaluated within four orientations. The thermal resistance in every orientation was less than one-half of that of the empty PHP. The results shown in this work contribute to improving the thermal management of electronics that generate high heat flux by proposing an innovative heat spreader.