A semi-empirical model to predict the pressure drop of pure refrigerants and refrigerant mixtures in microfin tubes for both condensation and evaporation is presented. The new pressure-drop model is based on an existing smooth-tube correlation. The model was validated using experimental data compiled from published literature and this showed that the model is capable of predicting pressure drops for different refrigerants and refrigerant mixtures within 10–25 per cent mean absolute deviation. This model can be employed in micro-fin tubes with fin heights from 0.1 to 0.38 mm, helix angles from 0 to 30°, and mass flux ranges up to 600 kg/m2 s.
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