Orientation-Free Micro Heat Pipe

Abstract

A simple design micro-heat pipe was proposed. It was composed of a 20.0 × 20.0 mm square flow circuit which had two adjacent narrow-sides (1.0 × 1.0 mm2 or 0.5 × 1.0 mm2) and two adjacent wide-sides (5.0 × 1.0 mm2 or 2.5 × 1.0 mm2). A heating spot was at the narrow side and a cooling spot was at the wide side. Working fluid was ethanol. The flow circuit was placed horizontally. Bubbles generated at the heating spot migrated toward the wide side, the bubbles coalesced there to form a large bubble, and then the large bubble moved to the cooling spot. Finally, the large bubble was condensed at the cooling spot. This cycle repeated continuously. As a result of it, heat transport from the heating spot to the cooling spot was produced in the micro heat pipe even if it was arranged horizontally. It was confirmed that this simple device works as the heat pipe. An analysis of a flow mechanism was performed by solving a simple flow equation based on the flow resistance. It was proved that one-way circulation flow could be formed in the flow circuit. Predicted flow velocities were close to measured velocities. The heat transport performance of the proposed micro heat pipe was much better than the heat conduction of a stainless steel plate.