Study on improvement of pulsating heat pipe and prediction of heat transport characteristics

点击翻译按钮获取中文摘要

Heat transport characteristics of a pulsating heat pipe (PHP), which consists of a copper plate in the heating section and 24 copper tubes in the adiabatic and cooling sections, has been investigated using water, ethanol and R141b as the working fluid. It was found that PHP with R141b has higher performance in lower heat load range, and that with water has higher performance in larger heat load range. In order to enhance the performance of PHP with R141b, small diamond particles were added to the liquid. The PHP performance using R141b with particles was superior in the whole range of heat load due to the heat transfer enhancement by the flow agitation owing to the particles. In addition to the tubular PHP, a plate-type PHP with a meandering groove channel was investigated. A new type channel configuration was proposed, that is, the channel which connects both ends of channels was also meandered. It was revealed that the new type channel has higher heat transport performance than the conventional one when ethanol was used as the working fluid. Further, a fundamental experiment was performed on a simple PHP, that is, an oscillation of a single liquid slug in a straight channel. Both end regions of the channel were heated, and the center region was cooled. The oscillation of liquid slug was visualized by a high-speed video, and the change of pressure in the vapor region was also measured. It was clarified that the phase lag between the liquid oscillation and pressure oscillation causes a work to the liquid, which is the principal mechanism of PHPs. An exact numerical analysis was performed for the sensible heat transport due to the oscillating liquid, and the role of latent heat transport was estimated by the comparison between experimental and numerical results.