Boiling heat transfer enhancement of R-134a in a tube bundle utilizing the EHD technique

Compound enhancement of boiling heat transfer with R-134a in a tube bundle was studied experimentally utilizing the electrohydrodynamics (EHD) technique. A laboratory-scale tube bundle utilizing commercially available forty fins per inch (40 fpi) tubes with R-134a as working fluid was used in the experiments. Two electrode configurations were tested (straight wire and wire mesh type). The results of the experiments suggest the applicability of the EHD technique for heat transfer enhancement in tube bundle while quantifying the role of various operating parameters. More than a four fold increase in the overall bundle heat transfer coefficient was obtained with wire mesh electrode. The corresponding enhancement with the straight wire electrode was two fold. The maximum EHD power consumption for the two electrode configurations were 5% and 1.2% of the bundle heat transfer rate, respectively. The experiments also addressed the effect of electric field polarity, which was found to have no pronounced effect on the enhancement mechanism for the bundle configuration at hand.