Analysis of thermal performance and optimization of concentric circular fins under dehumidifying conditions

The analysis of wet fins was carried out by many investigators with the variation of a linear relationship between specific humidity and the corresponding saturation temperature of air adjacent to the fin surface. For determination of the fin surface temperature under this scheme, fin-tip temperature is essentially known a priori which can be employed to calculate the psychrometric parameters associated with the dehumidification process. On the other hand, the tip temperature is only known after the salving the governing equation and it is also a function of the psychrometric properties of air. Thus for the simplicity, dew point temperature is considered as the tip temperature for calculating only the psychrometric parameters of fully wet fins in a recent publication. Nevertheless, in the actual situation this dew point temperature never satisfies at the tip and therefore psychrometric parameters calculated with the assumption of the dew point temperature at the tip may be incorrect. In the present work, an iterative scheme is demonstrated for determination of the actual tip temperature and local fin surface temperature. With considering this aspect, thermal analysis of a new geometric fin, namely, annular step fin (ASF) is proposed for the more effective utilization of fin material in comparison with the annular disc fin. An optimization study has also been made by using the modified thermal analysis of fully wet fins and the analysis of partially wet fins, separately. A remarkable change in results has been noticed when they are compared with that of the published result. Finally, it is worthy to mention that the maximum heat transfer rate per unit volume for an ASF is always higher than that of the annular disc fin for the identical design condition.