Electrohydrodynamic (EHD) enhancement of boiling heat transfer with a lo-fin tube

The effect of D. C electric field on nucleate boiling heat transfer for refrigerants of R-11, HCFC-123 and FC-72 was investigated experimentally by using a single lo-fin tube shell-and-tube heat exchanger. The lo-fin tube which brought two times increase in the heat transfer area provided about 150% of boiling hear transfer enhancement compared to that of smooth surface. This experimental study has revealed that the electrical charge relaxation time was an important parameter for the boiling heat transfer enhancement under electric field. Boiling heat transfer enhancement was obtained up to 40% for R-11 which had moderate relaxation time of 1.3 s. However remarkable boiling heat transfer enhancement has been obtained up to three fold increase(300%) for HCFC-123 which has the electrical charge relaxation time of 0.89 x 10(-3) s. For FC-72 having longer relaxation time than the bubble detachment one, no appreciable effect on the nucleate boiling heat transfer was observed.