Flow Boiling Inside Microfin Tubes: Recent Results and Design Methods

Microfin tubes have become the most important type of heat transfer augmentation for intube evaporation of refrigerants in direct-expansion evaporators, climate-control systems and heat pumps. These tubes are characterized by a large number of small fins inside small diameter tubes, providing heat transfer augmentations in the range from 1.5 to 4 times with only modest two-phase pressure drop penalties. The most recent experimental research on evaporation of pure fluids in microfin tubes is reviewed and the latest prediction methods are critically assessed.