Heat transfer enhancement of finned-tube heat exchanger using nozzle- and diffuser-shaped fins instead of straight fins

In this paper, a new method has been used to improve the heat transfer rate in the finned-tube heat exchanger with nozzle- and diffuser-shaped arrangement. For this study, the effect of several parameters was studied numerically. For the computational fluid dynamics simulation, the continuity, momentum, and energy equations were solved by the finite volume method using the standard k-epsilon model. The rate of heat transfer increases with the decreasing of fin bend radius (15 < R-fb < 20) for both nozzle-shaped fin and diffuser-shaped fin. By increasing of side temperature (600 < T-side < 900) and side Reynolds number (2000 < Re-side < 5000) the heat transfer rate increased for both nozzle- and diffuser-shaped fins. Results showed that a nozzle-shaped fin with a fin bend radius of 15 mm under the condition of Re-in = 20,000, T-side = 900 K, and Re-side = 3400 has a higher effect on heat transfer in comparison with the other types of fins. The maximum heat transfer rate was almost 39% and 35% for the nozzle-shaped fin with a bend radius of 15 mm and diffuser-shaped fin with a bend radius of 15 mm compared with the simple tube, respectively. Finally, correlational equations have been suggested to forecast the average Nu number as functions of various parameters of the tube equipped with different types of outer fins involving nozzle- and diffuser-shaped.