Measurement of heat transfer enhancement in melting of n-Octadecane under gravitational and electrohydrodynamics (EHD) forces

Organic Phase Change Materials (PCMs) have been studied extensively in literature for their use in latent heat thermal storage applications. This is mainly due to their chemical stability, high latent heat of fusion and low melting point which makes them a good candidate for space heating applications. However, one of the main drawbacks is their low thermal conductivity κ ≤ 0.6 W/mK, which poses a negative impact on the maximum allowable heat transfer rates that can be achieved which in turn puts a restriction on the geometry of the PCM modules. A novel heat transfer enhancement technique recently discovered employing the application of a high voltage within the PCM to introduce Electrohydrodynamic (EHD) forces which increases the melting process rate. The melting of paraffin wax under EHD forces was previously investigated and it was found that a reduction of the melting time by 40% can be achieved [5]. In this paper, a novel experimental methodology to quantify the heat transfer augmentation in melting of Octadecane under gravitational and EHD forces is presented. The developed experimental method allowed for the study of the EHD heat transfer enhancement under different parameters: electric potential, wave-form, temperature gradient and various aspect ratios. It is found that Coulomb forces are the main driving mechanism of enhancement in the melting of Octadecane and that a heat transfer augmentation up to 8.6 folds can be reached by using EHD.