The Effect of Frequency and Duty Cycle on Heat Transfer and Pressure Drop for Convective Condensation under Pulsed Electric Field

The effect of pulsed electric fields on heat transfer and pressure drop in horizontal in-tube convective condensation has been investigated. In particular, the effect of the frequency and duty cycle of an applied pulse wave between 0 and 8 kV was studied for frequencies in the range 0.5 Hz to 1.5 kHz and for 25 %, 50 % and 75 % duty cycles. The electric field was applied through a central electrode along the centerline of the tube. The experiments were performed for a constant mass flux of 58 kg/m2s and average vapor quality of 45 % which corresponds to stratified flow with the liquid level below the electrode (without EHD). The heat transfer enhancement ratio decreases with an increase of frequency for frequency range less than 60 Hz. Beyond 60 Hz, the heat transfer enhancement remains nearly constant and independent of frequency. The corresponding pressure drop ratio increases with an increase of frequency for frequency range less than 80 Hz. For frequencies more than 80 Hz, the pressure drop decreases with an increase of frequency. The heat transfer enhancement ratio and pressure drop ratio increase with an increase of the duty cycle for a given frequency of the applied signal.