Electrohydrodynamic Enhancement of Flow Boiling in an Eccentric Horizontal Cylindrical Channel

An experimental investigation has been conducted to study the effect of electrode position on electrohydrodynamic (EHD) augmentation of flow boiling heat transfer in a horizontal channel. The experiments were conducted for boiling HFC-134a on the tube-side of a coaxial heat exchanger for dc voltage from 0 to 8 kV, liquid mass flux up to 500 kg/m²·s, inlet quality from 0 to 50%, and three vertical electrode positions within the tube (0 mm and ±2.73 mm from the centreline). Both local and global measurements of the heat transfer are presented along with an evaluation of the influence of the imposed electric field on the overall pressure drop. With the inner electrode raised upwards, a 1.6 fold increase in the heat transfer coefficient has been observed for a modest voltage level of 2 kV and pressure drop penalty of 20%. This level of enhancement in heat transfer is similar to the one obtained with coaxial electrodes at an applied voltage approximately three times lower.