Abstract

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/tube heat exchanger. The lo-fin tube which brings two times increase in the heat transfer area provided about 150% of boiling heat transfer enhancement compared to that of smooth surface. Experimental study has revealed that the electrical charge relaxation time is 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 has moderate relaxation time of 1.3 s. However remarked 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 × 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.

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