Characterization of heat transfer modes of tube side convective condensation under the influence of an applied DC voltage

An experimental study was performed to determine the modes of heat transfer in horizontal tube side convective condensation under an applied DC high voltage. Experiments were performed with R134a in a horizontal, single-pass, counter-current heat exchanger. A 8 kV DC voltage was applied through a central rod electrode with the tube wall grounded for mass flux in the range 45–156 kg/m2 s. The average quality across the test section was 45%, which corresponds to an initially stratified flow with the liquid level below the central electrode. The high-voltage electric field results in an interfacial electric body force which extracts the liquid from the bottom stratum towards the vapour core. This results in a phase redistribution with a resultant increase in heat transfer. The increase in heat transfer can be attributed to a change of the heat transfer mode in the lower section of the tube from convective condensation to film condensation.