AC voltage induced electrohydrodynamic two-phase convective boiling heat transfer in horizontal annular channels

An experimental study of alternating current (AC) induced electrohydrodynamic (EHD) flow and heat transfer augmentation for boiling inside an annular channel containing working fluid refrigerant HFC-134a has been conducted in a single-pass, counter-flow heat exchanger with a rod electrode placed concentric to a grounded tube. Experiments were conducted for an inlet quality of 0%, a heat flux of 10.2kW/m2, mass fluxes from 100kg/m2s to 500kg/m2s and applied voltages from 0kV to 8kV DC and 0kV to 24kV peak to peak AC. The AC tests were conducted for both low frequency (60Hz) and high frequency (6.6kHz) near sinusoidal waveforms. The results show that there is no apparent difference between the DC and the 6.6kHz AC test cases, whereas the 60Hz AC tests show significantly different behavior. The flow boiling heat transfer results indicate that the averaged heat transfer coefficients can be increased by as much as 3-fold for a 24kV p.p. 60Hz AC applied voltage. This also incurs a pressure drop penalty of 2.6-fold across the heat exchanger.