Oscillating Heat Pipe Performance With Modified Evaporator Geometries

Abstract

An oscillating heat pipe (OHP) is a heat transfer device that is capable of transferring large amounts of thermal energy with low thermal resistances. These characteristics make it a potentially viable option for high-heat flux cooling requirements. OHPs have several key advantages over other cooling technologies: passive operation, simplicity, low cost, and low mass. OHPs consist of an evaporator, adiabatic, and condenser sections joined by multiple interconnected meandering channels. A two-phase working fluid, in this study acetone, fills the channels and acts as the heat transfer medium. The focus of this study is to investigate OHP performance with enhancements in the evaporator section. Four evaporator geometry variations were studied: wavy channel, straight channel, recessed cavity, and pin and cavity. It was found that the wavy-channel and recessed-cavity geometries have superior performance when compared to the traditional straight channel, with 40% and 27% lower thermal resistances, respectively. The pin-and-cavity OHP performed 22% worse in terms of thermal resistance, than the straight-channel OHP. The wavy-channel OHP uniquely showed excellent operating characteristics in the horizontal orientation (0° inclination angle). Both the wavy-channel and recessed-cavity OHPs also showed the ability to transfer larger amounts of thermal energy (up to 400 W) before drying out. The reduction in performance of the pin-and-cavity OHP relative to the straight-channel OHP indicates that a reduction in performance and results when the pressure drop between the evaporator and condenser sections is increased.