Mass transfer at the confining wall of helically coiled circular tubes in the absence and presence of packed solids

Limiting current measurements were made at the electrode surfaces fixed flush with the inner wall of a helically coiled circular tube. The measured limiting current facilitated the computation of wall–liquid mass transfer coefficients. The mass transfer data were obtained for the flow of electrolyte through the helical coil in the absence and presence of packed solids. The mass transfer coefficient was found to decrease with increasing p/D ratio and approached minimum for straight tube case. The mass transfer data were correlated in terms of Colburn factor j D, expressed as a function of Reynolds number Re and torsion number Tn obtained as j D = 0.34 Re − 0.58 T n 0.17 . Analysis of the experimental data obtained in case of packed coiled tubes of circular cros- section revealed that the effect of p/D ratio on pressure drop was observed to be insignificant. The effect of pitch on mass transfer coefficient in case of packed helical coils was found to be marginal.