An experimental investigation of micro pulsating heat pipes

Abstract

Two Si-based micro pulsating heat pipes (μPHPs) charged using HFE-7100 were either horizontally or vertically oriented and were tested using several heating powers. The width of each channel was 0.8 mm in one μPHP containing uniform channels, and the channel width was 1.0 mm or 0.6 mm in the other μPHP, which did not contain uniform channels. The depth of each channel was 0.25 mm. The overall size of each μPHP was 60 × 10 × 1.25 mm. Visual observation and temperature measurement of the μPHPs under various conditions were performed and the results were analyzed. The results indicated that when the μPHPs were operated horizontally at a heating power ranging from 1 to 7 W, the pulsating two-phase flow in the channels of the μPHPs could not begin, except when the μPHP containing nonuniform channels was tested at a heating power of 7 W. With a heating power less than 5 W, the frequency of the sine-like oscillating displacement of the vapor slug increased and the displacement of the vapor slug reduced in either vertically oriented μPHP, as the heating power increased With a heating power higher than 5 W, periodic "start-stop" behaviors were observed in the vertical μPHP containing nonuniform channels. © 2014 by the authors.