Heat transfer performance of polytetrafluoroethylene oscillating heat pipe with water, ethanol, and acetone as working fluids

Abstract

The startup mechanism, temperature oscillation, liquid slug oscillation, and heat transfer performance of polytetrafluoroethylene (PTFE)-based oscillating heat pipes (OHPs) are investigated experimentally. The effects of working fluid, heat input, filling ratio on the startup performance, surface temperature oscillation, and thermal resistance of OHPs are investigated and analyzed. A closed loop OHP with six turns and an inner diameter of 2.41 mm was tested in a vertical heating orientation with working fluids of deionized water, ethanol, and acetone, respectively. The results show that the acetone-filled OHP provides the best thermal performance among three OHPs. Average peak-to-peak amplitudes of temperature oscillations in the acetone- and ethanol-filled OHPs are greater than the ones in the water-filled OHP. Temperature oscillation frequencies are highest in the acetone-filled OHP and lowest in the water-filled OHP among three OHPs. Liquid slug oscillation characteristics behave the similar trend. The amplitude and velocity of liquid slug oscillation are highest in the acetone-filled OHP and lowest in the water-filled OHPs. For the PTFE-based OHP, the thermal performances of ethanol- and acetone-filled OHPs are higher than the thermal performance of the water-filled OHP at a heat input between 60 and 300 W, which are different from a copper OHP. This conclusion is different from results of literature research showed that water-filled OHPs gave a better heat performance than acetone- and ethanol-filled OHPs.