The effect of DC and AC electric fields on heat transfer in R11

This paper presents the effects of 6KV DC and AC electric fields on heat transfer by using vertical heating surface in Freon 11 (R11) used as a dielectric liquid. The vertical heating surface consists of 17mm diameter 80mm long electrically heated brass tube surrounded by eight brass electrodes 1.8 mm in diameter. The heater was placed such that heating surface and electrodes were immersed in R11 refrigerant. DC and AC electric fields were generated by connecting the electrodes to a high voltage power supply. The results show a high drop in surface temperature is recorded at the free convection regime by applying 6KV DC with 2.6 fold increase in heat transfer values. However, a marginal increase in surface temperature is detected at the nucleate boiling regime when both 6KV AC and DC fields are used indicating a marginal inhibition of heat transfer. When R11 accidentally contaminated with rubber in one of the experiments, up to 7.5fold increase in heat transfer enhancement is recorded in comparison with the pure R11.