Optimization design of falling film type plate-fin condenser/reboilers by minimizing specific entropy generation rate

This paper presents an optimization model for falling film type plate-fin condenser/reboilers based on the entropy generation minimization method, which considers the irreversibilities owing to both irreversible heat transfer and pressure drop. The specific entropy generation rate, i.e. the entropy generation rate per unit total heat transfer area, is proposed as an optimization objective function. Main geometrical parameters (i.e. fin height and fin pitch) of the evaporation channel of a falling film type plate-fin condenser/reboiler are optimized. The analytical results show that under certain fin pitch, there exist different optimal fin heights corresponding to the minimum entropy generation rate and the minimum specific entropy generation rate, respectively. In addition, the value of minimum specific entropy generation rate decreases with the increase of the fin pitch, and the optimal value of the fin height varies little with the fin pitch. Effects of the heat transfer temperature difference, inlet mass flow rate of liquid to be evaporated and inlet mass flow rate of vapor to be condensed on both the minimum specific entropy generation rate and optimum values of fin parameters are also analyzed in detail.