Effect of Nanofluid and Surfactant on Thermosyphon Heat Pipe Performance

An experimental analysis is done to investigate the thermal performance of a thermosyphon heat pipe (THP) using three working fluids, namely, distilled water, nanofluid, and a mixture of nanofluid and surfactant. The working nanofluid is titanium dioxide and THP is made of copper tube with the outer diameter of 15 mm and length of 1000 mm. The effects of the input power and inclination angle on the THP performance are investigated. The experimental results indicated that with increasing the concentration of nanofluid, thermal efficiency increases and thermal resistance of the thermosyphon decreases. According to the results, mixing the nanofluid with the surfactant will decrease the evaporator wall temperature and the thermal resistance, while it increases the thermal efficiency of THP. Comparison between two nanofluids and a conventional fluid in a THP shows that the best pipe inclination angles are 60 degrees for water and 90 degrees for nanofluids. Adding the proper amount of surfactant increases THP's thermal efficiency by 20%. The best thermal performance of THP achieved at the input power of 200W for all the working fluids. The average deviation of 1% was observed between the experimental results of this study and those available in the open literature.