Electrohydrodynamic effects on a nanofluid-filled flat heat pipe

Abstract

This study deals with a theoretical investigation on an axially grooved Flat Miniature Heat Pipe (FMHP) under an electric field. Copper oxide (CuO) and aluminum oxide (Al2O3) nanoparticles in N-pentane based nanofluid are considered. Under zero-electric field conditions, augmenting the nanoparticle volume fraction increases the liquid velocity at the evaporator and a part of the adiabatic zone, and reduces the vapor velocity in the adiabatic and the condenser zones. Results also reveal that the addition of the nanoparticles reduces the vapor pressure drop; in contrast, it increases the liquid pressure drop. The electric field increases the vapor pressure drop; however, it reduces the liquid pressure drop. Moreover, the EHD effects on the liquid and vapor velocities depend on the FMHP zone. The results also indicate that the capillary limit increases with the volume fraction of the nanoparticles and the electric field strength. It is also demonstrated that the capillary limit obtained with CuO nanoparticles is higher than that provided by Al2O3 nanoparticles. The study evidences the existence of an optimum fill charge for which maximum transferred heat powers are obtained. The optimum fill charge for the Al2O3 nanoparticles is lower than that obtained for CuO nanoparticles.