Numerical Study on an Electrohydrodynamically Driven Axially Grooved Flat Miniature Heat Pipe

Abstract

This study deals with the use of the electrohydrodynamic effects in flat miniature heat pipes (FMHP). A prototype is conceived and modeled. The equations of the model are developed on the basis of the mass, momentum, and energy balance equations as well as the Laplace–Young equation, which is modified in order to take into account the action of the electric field on the liquid–vapor interface. The electric field promotes the condensate flow back to the evaporator section. Hence, the capillary driving pressure, which is ensured by the capillary grooves, is diminished because the electrohydrodynamic pumping becomes responsible of the liquid flow from the condenser to the evaporator. The electric field decreases the liquid velocity and hardly affects the vapor velocity. Moreover, it increases the vapor pressure drop, and it decreases the liquid pressure drop. The effect of the fill charge on the capillary limit is particularly highlighted. For given groove dimensions, it is demonstrated that there exists an optimum fill charge that ensures a maximum capillary limit. The evolution of the flow parameters is given and discussed for different fill charges and maximum heat input powers.