Heat Transfer During Forced Convection Boiling of R-12 Under Swirl Flow

This work is an experimental investigation of heat transfer augmentation in a horizontal R-12 evaporator, continuing an earlier study [1] by the authors on swirl flow pressure drops. Twisted tapes were used to create swirl motion during the flow boiling inside an evaporator tube of 10 mm i.d. Average heat transfer coefficients have been determined for 60 runs corresponding to three heat fluxes, five mass velocities, and four twist ratios. Swirl flow heat transfer coefficients have been found, in general, to be greater than the corresponding plain flow values, but the degree of enhancement varies depending on the test conditions and the twist ratio of the inserted tape. An empirical correlation which predicts the average swirl flow heat transfer coefficients within ± 30 percent of the experimentally observed values has been successfully developed.