The heat transfer and mass transfer fin efficiencies were analyzed numerically to show that popular models for heat transfer fm efficiency for circular fins are not always reasonable. The numerical results show that the effective heat transfer area of a circular fin increases several times faster than that of a straight fin for the same tube radius. Then, a simple but accurate heat transfer fin efficiency model was developed and verified by numerical results for a wide range of fin designs. This model predicts the heat transfer fin efficiency with absolute errors of less than 1%. The heat transfer and mass transfer fin efficiencies were found to be quite different for typical air flow with low relative humidity. Thus, these two fin efficiencies should not be assumed to be equal and a mass transfer fin efficiency model was developed, based on the heat transfer fin efficiency model. These heat transfer and mass transfer fin efficiencies are very useful for more accurate prediction for a wide range of practical applications.
