Experimental Investigation of Closed Loop Pulsating Heat Pipe with Different Filling Ratio of Working Fluid

Abstract

With the advancement of science and engineering the need for space restricted cooling devices has increased. Closed loop pulsating heat pipe (CLPHP) is a new promising technology for heat transfer of microelectronics. In it by simple mechanism heat is transferred effectively and efficiently. The combination of processes like bubble nucleation, collapse, formation of vapor plugs and slugs, agglomeration, dynamic instabilities and temperature/pressure perturbation, etc. leads to exceptional heat transfer capability of the heat pipe. The aim of this research paper is to better understand the operation of PHP through experimental investigations and obtain comparative results for different parameters. A series of experiments are conducted on a closed loop PHP (CLPHP) with 8 loops made of copper capillary tube of 2 mm inner diameter. The heat pipe structure is using normal, CLPHP. DI Water, Ethanol, Methanol and Acetone is taken as the working fluid. The operating characteristics are studied for the variation of heat input, filling ratio (FR) and orientation. The single filling ratios are 0%, 30%, 50%, 70% and mixed filling ratio are (50%-50%) based on its total volume. The orientations are 0° (vertical). This paper attempts to demonstrate the effect of variation of different parameters on the same structure as well as the variation of thermal performance depending on the presence of wire insert and fins on different structures. The experiment demonstrates the effect of filling ratio and inclination angle and structural variation on the performance, operational stability and heat transfer capability of ethanol as working fluid of CLPHP. Important insight of the operational characteristics of CLPHP is obtained and optimum performance of CLPHP using ethanol and Methanol is thus identified. Acetone and Methanol (Mixed) works best at 50% FR at wide range of heat inputs for all structures of CLPHP. The best performance is obtained with normal structures. The optimum performance of the device can be obtained at vertical position