Experimental Investigations on the Thermal Performance of a Vertical Closed Loop Pulsating Heat Pipe Using Binary Mixture of Fluids

This paper presents the experimental investigations conducted on a vertical closed loop pulsating heat pipe (VCLPHP) to evaluate the thermal performance. The values of thermal resistance and heat transfer coefficient obtained in the experimentation is used as evaluation parameters. The VCLPHP used has capillary tubes having an inner diameter of 2mm and outside diameter 3mm and bent into 5 turns. The lengths of the evaporator, adiabatic and condenser sections are 50, 90 and 70mm, respectively. The binary mixture of fluids used are acetone – ethanol and ethanol - methanol mixtures. The thermal performance of these binary mixtures were then compared with conventional working fluids such as acetone, ethanol and methanol. The fill ratios was changed from 50 to 80% in steps of 10% and the heat inputs were varied between 60 to 90W in steps of 10W. However, the mixing proportions for all mixtures was maintained as 1:1. All the experiments were conducted in the vertical position (90°). The experimental results showed that, the overall performance of acetone was the best with the lowest thermal resistance and highest heat transfer coefficient as compared to all pure fluids and among fluid mixtures the acetone-ethanol mixture showed the best thermal performance.