Chemical Engineering Journal, Vol.92, No.1-3, 15-26, 2003
Influence of secondary flow on diffusion with heterogeneous reaction
The concentration distribution in a Newtonian fluid for the secondary flow in a curved tube with bulk/wall reaction is obtained for a range of parameter values using an axially marching spectral finite difference scheme. The results predominantly illustrate that for fixed extent of secondary flows there is an improvement in the performance of the reactor as the effect of bulk and wall reaction mechanisms intensify in the system. For the same magnitude (moderate effects) of bulk and wall reaction mechanisms, there appears to be an increased conversion/performance in the homogeneous case. For small values of the reaction parameters, the improvement in the performance (3%) is more due to the wall reaction than bulk reaction. But, for moderate values of the non-dimensional reaction parameters (around 10), the enhanced performance (28%) is more due to the bulk reaction than wall reaction. As the effects of secondary flow dominate, there is an improvement in the performance of the reactor irrespective of the reactivity of the solute and the results agree with those of Mashelkar and Venkatasubramanian [AIChEJ. 313 (1985) 440] for the case of non-absorbing walls. It is also observed that the approach of isoconcentration profile to the stream line pattern occurs at a lower value of the curvature parameter in the presence of wall reaction. The study is extended to examine the modifications in the tracer response measurements due to the power law theology of the flowing fluid. The salient observation, irrespective of the reactivity of the solute, is that the performance of the reactor is improved in the case of pseudoplastic fluids compared to dilatant fluids. This improvement is further enhanced due to the presence of mild wall reaction.