Effect of electrohydrodynamic (EHD) forces on charging of a vertical latent heat thermal storage module filled with octadecane

Abstract

Abstract The effect of Electrohydrodynamic (EHD) forces on the charging speed of a vertical latent heat thermal storage module filled with Octadecane as the Phase Change Material (PCM) was investigated experimentally. The melting process was initially governed by natural convection before introducing EHD forces. The melting process was studied under different applied voltages and the interaction between the EHD forces and gravitational forces (natural convection) was visualized using a novel shadowgraph measurement technique. It was found that the EHD forces significantly reduced the charging speed by up to 1.7 times when applying +6\xa0kV DC for a Rayleigh number of ( R a = 9 × 10 7 ) and a Stefan number of ( S t e = 0.045 ). The level of enhancement was increased by applying higher voltages, with cell bifurcation being identified as the main mechanism of enhancement. Local heat transfer coefficient measurements from the shadowgraph system identified the different heat transfer regimes: electrically dominated regime and mixed electrical and gravitational heat transfer regimes. Finally, the findings revealed that EHD forces expedited convection heat transfer by reducing the size of the convection cell.