Experimental Investigation and Performance Evaluation of a Closed Loop Pulsating Heat Pipe

Pulsating heat pipe (PHP) cooling is the new and emerging technique in the field of thermal management of electronics. In the present work, transient and steady state experiments are conducted on a single turn closed loop PHP. Evaporator and condenser wall temperatures are measured. Copper is used as the capillary tube material in the evaporator and condenser sections with inner diameter of 1.95 mm and outer diameter of 3 mm. The total length of the closed loop pulsating heat pipe is 540 mm. The evaporator and condenser sections are 185 mm and 195 mm respectively. The experiments are conducted both in the horizontal as well as in vertical orientations for different heat loads varying from 9 W to 15 W in steps of 2 W. The PHP is tested with different working fluids viz., Acetone, Methanol and Ethanol for different fill ratios from 60% to 80% in steps of 10%. The performance parameters such as temperature difference between evaporator and condenser, thermal resistance and the overall heat transfer coefficient are evaluated. The experimental results demonstrate that Acetone is the better working fluid among the working fluids considered in terms of lower thermal resistance and higher heat transfer coefficient. The heat transfer characteristics of PHP are found to be better at a fill ratio of 60%. The single loop PHP is found to perform better with horizontal orientation for all heat loads, working fluids and fill ratios considered.