Experimental investigation of hybrid fluid oscillatory motion and heat transfer in oscillating heat pipes

Abstract

Mathematical models predicting the oscillatory motions as well as the heat transfer effects of hybrid fluids (HF) in an oscillating heat pipe (OHP) are simulated. The models consider the vapor bubble as the gas spring for the oscillatory motions including effects of operating temperature, vapor bulk modulus, and temperature difference between the evaporator and the condenser. Using the theoretical hybrid fluid oscillatory motions from the developed models, heat transfer models showing the theoretical temperature differences in the evaporator and the condenser are developed including the effects of forced convection heat transfer due to the oscillating motion, the confined evaporating heat transfer in the evaporating section, and the thin film condensation heat transfer in the condensing section. Furthermore, an experimental investigation was conducted on a copper hybrid fluid oscillating heat pipe (HFOHP) with six turns. It is observed that the analytical models resemble and follow the same trends as the experimental data gathered. Results show that the changes in the working fluid's thermal properties due to the addition of gallium significantly helps to increase the heat transfer performance of a water OHP and helps provide a better understanding of HFOHP optimization for applications in high-powered systems.