Optimization of the wire electrode height and pitch for 3-D electrohydrodynamic enhanced water evaporation

In this study, numerical and experimental analyses were carried out to study the electrohydrodynamic (EHD) effect on the evaporation rate of a channel forced convection flow. Three-dimensional steady turbulent flow equations combined with Maxwell equations were solved. The optimization of the electrode height (H) and longitudinal pitch (SL) was investigated numerically along with an optimal strategy (SCGM, simplified conjugate-gradient method). The mass transfer gain per power consumption was taken as the objective function to be maximized. The results showed that the EHD effect on the evaporating rate increased with increases in applied voltage and electrode pitch (SL) and decreases in electrode height (H). For example, as air flow inlet velocity uin = 1 m/s and applied voltage V0 = 15 kV, the mass transfer enhancement was doubled for SL = 40-100 mm at H = 20 mm, while the mass transfer enhancement was 3.5 times greater for H = 30-15 mm at SL = 100 mm. In addition, the optimization analysis indicated that the mass transfer gain enhanced per Watt power consumption by 316.9-179.7% when combined with the optimal (H, SL) design ranging from V0 = 13 to 17 kV and uin = 1.0 m/s. The comparisons of numerical results and experimental data obtained satisfactory consistency within a discrepancy of 19%.