The Simultaneous Measurement of Wall Temperature and Flow Movement Inside a Pulsating Heat Pipe using Temperature-sensitive Paint and Fluorescent Dye

Abstract

A Pulsating Heat Pipe (PHP) is getting attention as one of the efficient heat transfer devices. However, a thermal fluid property inside PHP is so complicated and still unclear. In this study, temperature distribution and flow inside the PHP were visualized simultaneously by using Temperature-sensitive Paint (TSP) and dissolved fluorescence dye, respectively. The TSP was painted on a glass plate in stripe shape to cover a half of a channel. The TSP was excited by UV LED light and the intensity of luminescence was captured by high-speed camera in insulated area of the PHP. The intensity of luminescence was converted into temperature by means of getting a calibration function. The temperature of inner wall of the PHP changed corresponding to passages of liquid phase and vapor phase. The temperature decreased when liquid phase passed through and increased when vapor phase passed through. Moreover, the temperature changed when a liquid droplet or a vapor bubble passed through. It is suggested that these temperature changes were caused by both a difference of heat transfer coefficient between liquid phase and vapor phase and a phase change. These experimental results have possibility that determine boundary temperature corresponding to flow condition.