On Boiling Limit In Closed Loop Pulsating Heat Pipe and Effect of Filling Pressure

This paper presents the results of an experimental study on investigation of operational limits in a closed loop Pulsating Heat Pipe (CLPHP) which turns into an interesting field of study for researchers as a high efficiency device rather than any metal to enhance and intensify heat transfer through passive two phase heat transfer mechanism. Although up to date, there is no complete theoretical understanding of operational characteristics of these devices, many applications ranging from electronics thermal management to compact heat exchangers achieved. It is needed to produce experimental data under various operating conditions for a better theoretical understanding.The experiments are carried out for different working fluids, filling ratio and evacuation levels at the different heat loads to specify the boiling limit point (dry-out) of CLPHP and choose the best condition to solve it. The results show that working fluids at filling ratio of 60% and more evacuation level have better performance and acetone is the best in comparison with methanol, ethanol and distilled water.