Parametric Characterization on the Thermal Performance of a Closed Loop Pulsating Heat Pipe

Recently closed loop pulsating heat pipes have been receiving much attention because of their potential applications in high heat flux micro-electronic systems. They work by self thermal driven oscillation without any mechanical parts. Though they are simple in structure, understanding of the heat transfer mechanism is highly complex having a strong thermo- hydro dynamic coupling governing their performance. In this paper, an experimental study on a closed loop PHP with a single turn has been conducted there by providing vital information regarding parameter dependence on its performance. The PHP is made of brass tube having an internal diameter of ۲ mm and outer diameter of ۳ mm. The parametric characterization has been done for the variation in internal diameter, fill ratio, working fluid and orientation of the device. The working fluids Acetone, Methanol, Ethanol and Propanol are considered for experimentation with volumetric filling ratios of ۵۰%, ۶۰%, ۷۰% and ۸۰%. Input heat power of ۷ to ۱۲ W is varied at the evaporator section. The CLPHP is also verified for its thermal performance at ۰۰, ۳۰۰ and ۶۰۰ orientations. The transient and steady state experiments are conducted and operating temperatures are measured using K- type thermocouples. The results highlighted that the thermal performance of a PHPis strongly influenced by change in fill ratios, orientation and heat input. ۸۰% fill ratio yields an effective heat transfer rate for a horizontal mode of operation. Appreciable fluid movement and better heat transfer rate are observed for the ۳۰۰ orientation of PHP operation. Acetone exhibits better heat transport capability compared to other working fluids in all orientations.