Experimental studies on heat transfer and friction factor characteristics of laminar flow through a circular tube fitted with helical screw-tape inserts

Experimental investigation of heat transfer and friction factor characteristics of circular tube fitted with full-length helical screw element of different twist ratio, and increasing and decreasing order of twist ratio set have been studied with uniform heat flux. The experimental data obtained are compared with those obtained from plain tube published data. The heat transfer coefficient increases with twist ratio. There is no much change in the magnitude of heat transfer coefficient enhancement with increasing twist ratio and with decreasing twist ratio set, as the magnitude of swirl generated at the inlet or at the outlet in the order of increasing twist ratio or decreasing twist ratio, is same in both the cases. The empirical correlations developed in terms of twist ratio and Reynolds number, are fitting the experimental data within plus or minus 15% and 13% for Nusselt number and friction factor, respectively.