Overall Efficiency of a Radial Fin Assembly Under Dehumidifying Conditions

Abstract

The aim of this paper is the analysis of heat transfer in a radial fin assembly during the process of dehumidification. An individual finned tube geometry is a reasonable representation of heat exchangers used in air conditioning. The condensation process involves both heat and mass transfer and the cooling takes place by the removal of sensible as well as latent heat. The ratio of sensible to total heat is an important quantity that defines the heat transfer process during a dehumidifier operation. A one-dimensional model for heat transfer in the fin and the heat exchanger block is developed to study the effects of condensation on the fin surface. The combined heat and mass transfer process is modeled by incorporating the ratio of sensible to total heat in the formulation. The augmentation of heat transfer due to fin was established by comparing the heat transfer rate with and without fins under the same operating conditions. Calculations were carried out to study the effects of relative humidity and dry bulb temperature of the incoming air, and cold fluid temperature inside the coil on the performance of the heat exchanger. An analysis of the overall efficiency for the assembly was also done. Results were compared to those under dry conditions, wherever appropriate. Comparison between present results and those published for rectangular as well as radial fins under fully wet conditions were made. These comparisons established the validity of the present model. It was found that the heat transfer rate increased with increment in both dry bulb temperature and relative humidity of the air. The augmentation factor, however, decreased with increment in relative humidity and the dry bulb temperature. The fin efficiency decreased with relative humidity.