Flow patterns and heat transfer characteristics of flat plate pulsating heat pipes with various asymmetric and aspect ratios of the channels

Abstract

The thermal performance of flat plate pulsating heat pipes (PHPs) in compact electronic devices can be improved by adopting asymmetric channels with increased pressure differences and an unbalanced driving force. The objective of this study is to investigate the heat transfer characteristics of flat plate PHPs with various asymmetric ratios and aspect ratios in the channels. The thermal performance and flow pattern of the flat plate PHPs were measured by varying the asymmetric ratio from 1.0 to 4.0, aspect ratio from 2.5 to 5.0, and heat input from 2 to 28W. The effects of the asymmetric ratio and aspect ratio on the thermal resistance were analyzed with the measured evaporator temperature and flow patterns at various heat inputs. With heat inputs of 6W and 12W, the optimum asymmetric ratio and aspect ratio for the flat plate PHPs were determined to be 4.0 and 2.5, respectively. With the heat input of 18W, the optimum asymmetric ratio and aspect ratio were determined to be 1.5 and 2.5, respectively.