Optimization of thermohydraulic performance of tube heat exchanger with L twisted tape

Abstract

A numerical investigation was conducted to explore the heat transfer optimization effect of circular tube heat exchanger with L-shaped twisted tape insert and to find the optimal parameter design in this paper. For better thermohydraulic performance, the effects of twist pitch (P), inner diameter (D), tape width (W) and number of tape (N) were studied with Reynolds number ranged from 1875 to 3750. Moreover, response surface method (RSM) was employed to indicate the relationship between the Nusselt number (Nu) and these parameters. With the analysis of flow structure inside the tube, it was conducted that the twisted tape insert was helpful to transform the axial velocity of fluid to radial velocity, forming vortex in the L region. The numerical results showed that the Nu and friction factor (f) of the tube fitted with L-shaped twisted tape insert gained an 199% to 208% increase and 674% to 696% when compared with that of smooth tube respectively. Besides, an optimal parameters set was obtained with P = 65.59 mm, W = 0.95 mm, D = 8.80 mm, in which the Nu and f were increased by 204% and 704% respectively as the results of response surface method.