Study on Heat Transfer and Flow Mechanism in Loop-Type Micro Heat Pipe

Abstract

A simple design micro-heat pipe was proposed. It was composed of 20.0 × 20.0 mm square flow circuit which had two adjacent narrow-sides (1.0×1.0 mm or 0.5×1.0 mm) and two adjacent wide-sides (5.0×1.0 mm, 5.0×0.5 mm, 3.0×1.0 mm or 2.5 × 1.0 mm). 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. It was confirmed experimentally that the circulation flow was formed in the micro flow circuit without any pump and the gravity effect. It was also analytically proved by solving a simple flow equation that the net circulation flow could be formed when the flow circuit; the flow resistance, was asymmetric. The boiling phenomena of the narrow space of the present scale (~ 1 mm) could be expressed with the existing correlation. Further examination is necessary for the narrow space condensation phenomena. It was proved that the micro heat pipe proposed is advantageous in the high heat road condition and in the light weight condition.