Thermal Spreading with Flat-Plate Oscillating Heat Pipes

Abstract

The thermal performance of a flat-plate oscillating heat pipe operating as a heat spreader was experimentally investigated. The copper flat-plate oscillating heat pipe had overall dimensions of , possessed two layers of minichannels, and was charged with acetone to a filling ratio of approximately 80%. The flat-plate oscillating heat pipe was centrally heated with a square heat source and had a copper pin-fin heat sink attached to its opposite side for crossflowing air at speeds of either 1, 2, or . The results clearly indicated that the flat-plate oscillating heat pipe is capable of operating in the thermal spreading mode, providing for a 10–15% reduction in total thermal resistance (relative to pure copper) and managing heat inputs up to 230 W with the maximum surface temperature not exceeding 100°C. In addition, the temperature uniformity of the heat sink was greater when attached to the flat-plate oscillating heat pipe, especially for lower Reynolds numbers (airspeeds). A critical heat input was required to initiate the flat-plate oscillating heat pipe, and this heat input increased with Reynolds number. This study further confirms the heating mode directly affects the heat transfer performance of a flat-plate oscillating heat pipe.