Heat transfer enhancement and optimization of a tube fitted with twisted tape in a fin-and-tube heat exchanger

This research examines the effects of a tube fitted with twisted tape on the optimal design of a fin-and-tube heat exchanger (FTHE). The twisted tape on the tube side results in a trade-off between the heat transfer and pressure drop, so both the effectiveness (which is related to the rate of heat transfer) and the total annual cost (which is related to the heat transfer area and pressure drop) were optimized simultaneously. All the physical parameters of the FTHE were considered as design parameters, and the optimization was performed using a genetic algorithm for different mass flow rates of the tube side. All the optimum results in the case with the twisted tape tube (TTT) were compared with the case of a plain tube (PT). The optimum results show that the Pareto front for the case of the TTT was completely dominant over the PT for lower mass flow rate (0.25 kg s⁻¹). Both the effectiveness and annual cost were enhanced in the TTT compared with the PT at the lower mass flow rate. On the other hand, for higher mass flow rates, there was a marginal point for effectiveness at which the Pareto front of TTT is dominant over that of the PT. For example, the TTT was optimal for effectiveness higher than 0.73, while the PT was optimal for effectiveness lower than 0.73 at a mass flow rate of 0.5 kg s⁻¹. For the low mass flow rate, the TTT is recommended for a wide range of effectiveness, while in the case of high mass flow rate, the TTT is recommended for just high effectiveness.