Studies on the effect of coaxially placed entry region disc as turbulence promoter on momentum transfer rates in forced convection flow of electrolyte were conducted. The study covers various diameters of the disc (D_d). Within the range of variables covered, the augmentation achieved in friction factor was found to be 5-fold over the tube flow in absence of promoter. Momentum transfer rates were analyzed with momentum transfer roughness function and roughness Reynolds number. The following correlation was reported from the study R(h⁺) = 0.0009 (Re⁺)^1.125 (f₅)^-0.869.

In earlier studies, the effect of roughness on friction factor and velocity distribution was done by Nikuradse (1933) for sand grain roughness. Cope (1941) studied the heat and momentum transfer for roughness elements, and later Nunner (1956) did so. Friction factor and heat transfer measurements for repeated rib roughness in tube flow were done by Sams (1956), Koch (1958), and Burgoyne et al. (1964). Webb et al. (1971) conducted experiments using tube with internal pins and correlated their data in terms of roughness Reynolds number (Re⁺) and roughness momentum transfer function R(h⁺). Dipprey and Sabersky (1963) analyzed their data in terms of roughness function for their experimental study. Sethumadhavan and Raja Rao (1983) conducted experiments for heat and momentum transfer for the tubes with tightly fitted helical wire coils. Most of the works mentioned above utilized wall similarity concept and correlated their data in terms of roughness function and roughness Reynolds number by assuming two regions, namely (i) Viscous region close to the wall of the tube; and (ii) Turbulent region which exists in the turbulent core away from the surface of tube. The same two-region flow assumed in the present study, also due to the presence of disc across the flow in the tube, generates turbulent core flow and viscous flow at the wall. An attempt was made to correlate the data in terms of R(h⁺) and (Re⁺) using the following type of analysis.

Chemical Engineering Journal, Momentum Transfer, Friction Factor, Turbulence Promoter, Turbulent Core Flow, Exit Calming Section, Helical Swirl Generators, Disc Diameter, Velocity Distribution, Molecular Viscosity, Frictional Resistance, Regression Analysis.