Effect of aspect ratio and filling ratio on thermal performance of an inclined two-phase closed thermosyphon

In this paper the effect of the aspect ratio and filling ratio on the thermal performance of an inclined two-phase closed thermosyphon under normal operating conditions has been investigated experimentally. The experiments were carried out for filling a ratio range of 20%<= F.R <= 60% and aspect ratios of 15, 20, and 30 for an inclination angle range of 15 degrees <=Phi <= 90 degrees. The thermosyphon was manufactured using a copper tube with an inside and outside diameter of 14 and 16 min respectively, and a 1000 mm length. Distilled water was used as the working fluid. The heat transfer rate, temperature distribution, and condensation heat transfer coefficient of the inclined two-phase closed thermosyphon were measured. The results showed that the maximum thermal performance of the thermosyphon occurred at 60 degrees for all three aspect ratios and several filling ratios. The thermal performance of the inclined thermosyphon with an inclination angle of 60 degrees was better for a filling ratio of 45%. It was also found that a higher condensation beat transfer coefficient for all three aspect ratios took place between 30 and 45 degrees.