Analytical methods for the efficiency of annular fins with rectangular and hyperbolic profiles under partially wet surface conditions.

In this study, we analytically investigate the performances of annular fins with rectangular and hyperbolic profiles under partially wet conditions. We propose four equations for the profiles of enthalpy difference, four equations for heat transfer rates, and four equations for fin efficiency which is a function of interface radius. We then present four equations for evaluating interface radius. Results indicate that the heat transfer rate and efficiency of an annular fin with a rectangular profile is higher than that with a hyperbolic profile. The efficiency under partially wet conditions is between those under fully dry and fully wet conditions. The efficiency of fully dry fins is independent of relative humidity; however, for fully wet and partially wet conditions, efficiencies increase with decreasing relative humidity. At the same relative humidity, heat transfer rate increases with an increasing ratio of outside radius to inside radius. In contrast, fin efficiency decreases. By analytical method, the partially wet annular fin performances are investigated. Partially wet fin efficiency of annular fin of rectangular profile is presented. Partially wet fin efficiency of annular fin of hyperbolic profile is presented. [ABSTRACT FROM AUTHOR]