Numerical study of the electrohydrodynamic effects on the two-phase flow within an axially grooved flat miniature heat pipe

A model for the fluid flow and heat transfer in an electrohydrodynamic (EHD) miniature heat pipe is presented. Coulomb and dielectrophoretic forces have been considered in the model. The coupled non-linear governing equations are developed and solved numerically. The variations of the liquid and vapor velocities and pressures as well as the liquid and vapor distributions along the Flat Miniature Heat Pipe (FMHP) are obtained. The electric field affects the liquid and the vapor velocities. It is also demonstrated that the vapor pressure drop increases with the electric field intensity, however, the liquid pressure drop decreases as the electric field strength increases. Moreover, the higher is the electric field intensity; the lower is the capillary pumping required for the liquid flow. This results into a lower liquid-vapor radius of curvature at the condenser. Similarly, the electric field affects the liquid-vapor shear forces as well as the liquid-wall and vapor-wall viscous forces. The analysis of the electric forces shows that the dielectrophoretic forces which act on the liquid-vapor interface are predominant and their order of magnitude is much higher than the Coulomb forces. It is also demonstrated that the capillary limit increases with the electric field, and the electric field reduces the dry-out when the applied heat input is higher than the capillary limit.