Effect of a channel layout on the thermal performance of a flat plate micro pulsating heat pipe under the local heating condition

Abstract

The effect of a channel layout on the thermal performance of a flat plate micro pulsating heat pipe (MPHP) under the local heating condition was investigated through a series of experiments. The thermal characterization was investigated, and flow visualization was conducted. The MPHPs with randomly-arranged channel layouts were fabricated to have the various effective dissimilarities. HFE-7000 was used as the working fluid, and a filling ratio was fixed at 50% in the present study. The effective dissimilarity was first introduced in this study as an attempt to quantify the effect of a channel layout on the thermal performance of a PHP under the local heating condition, and it was evaluated using the non-uniformity of a channel layout in the heating section. In the case of the MPHP with a uniformly-arranged channel layout, it had non-oscillating liquid slugs, which aggravates the thermal performance and operating range of the MPHP. However, liquid slugs in the MPHPs with randomly-arranged channel layouts oscillated with large-amplitudes in all the channels. Consequently, they had up to 32% higher thermal performance and two times wider operating range than those of the MPHP with a uniformly-arranged channel layout. Finally, this study experimentally found that the thermal performance of the MPHP increases as the effective dissimilarity increases. Therefore, the channels of the MPHP under the local heating condition should be arranged to have the large effective dissimilarity as much as possible to enhance the thermal performance and to extend the operating range simultaneously.