Quantitative analysis of thermal performance and flow characteristics of oscillating heat pipes with different initial pressure

Abstract

Because of the importance of saturation condition to the operation of the oscillating heat pipe (OHP), the initial pressure of the OHP is a key parameter that affects its thermal performance. In the present work, thermal performance and flow characteristics of OHPs with different initial pressure (0.007 MPa, 0.018 MPa, 0.036 MPa and 0.065 MPa) under different heating power (0–140 W) and inclination angle (30°, 45°, 60° and 90°) were experimentally tested. Meanwhile, a regression model was proposed to quantitatively describe the variation of thermal resistance with heat input and initial pressure. The results showed that both the average temperature of evaporation section and the thermal resistance of OHP increased with the increase of initial pressure. The thermal performance could be 493% deteriorated with the increase of initial pressure from 0.007 MPa to 0.065 MPa. Compared with the OHP with lower initial pressure, the OHP with higher initial pressure had a smaller velocity of working fluid movement and a bigger temperature oscillation amplitude under the same amount of heat input. Based on the regression model, thermal resistance of OHP was more sensitive to heating power under small heat input, while more sensitive to initial pressure under big heat input. We hope the present work could provide some insights into the effects of initial pressure on the thermal performance and flow characteristics of the OHPs.