Mesoscopic numerical study of the startup characteristics of grooved heat pipe under high heat flux

Abstract

The dry-out phenomenon that occurs in the evaporation section under high thermal load can lead to heat pipe startup failure, which considerably affects the safe and efficient operation of microelectromechanical systems. In this study, the startup characteristics of a grooved heat pipe are investigated with the mesoscopic lattice Boltzmann method. The focus is on the effects of wettability, inclination angle, and liquid filling volume on the evolution of the liquid supply velocity and dry-spot area. Results show that nucleate boiling can be formed by starting the heat pipe at high heat flux, and the vapor jetting generated by bubble bursting can reduce the liquid supply velocity by more than 70%. Capillary pressure can be increased, and the perturbation of bubbles to the meniscus region can be suppressed by enhancing the wettability of the capillary wick, thus promoting the return of the condensate to the evaporation section. The pressure on the liquid side in the evaporation section decreases as the inclination angle increases, which shortens the waiting time for vapor core formation and improves the stability of boiling behavior. A non-monotonic relationship exists between the liquid filling volume and heat transfer limit time of the heat pipe, which reaches the maximum only when the initial liquid layer fills the capillary wick exactly.