Second-law analysis on plain fin-and-tube heat exchangers

Second-law analysis on the heat exchanger having plain fins on a staggered array of circular tubes was conducted on the basis of correlations of Nusselt number and friction factor proposed by Kim et al. (1998), from which the entropy generation rate was evaluated. Optimum Reynolds number and minimum entropy generation rate were found over different operating conditions. At a fixed heat duty, within the valid of range of Kim et al.'s correlation, the plain fin-and-tube heat exchanger should exhibit a small tube spacing in air flow direction, a large number of tube rows, and large fin thickness and the spacing between adjacent plain fins. There is an optimal ratio between tube spacing normal to air flow direction and the tube diameter.