RTD for diffusion free laminar flow in helical coils

Residence time distribution of a purely viscous non-Newtonian fluid in helically coiled or spatially chaotic flows

“…In these configurations, they obtained an essentially unique RTD curve which is narrower than that for straight ducts, confirming the theoretical results of Ruthven [5]. Trivedi and Vasudeva [10] complemented their previous experimental study by investigating the incidence of molecular diffusion for Schmidt numbers varying from 1500 to 8700, using the same coils as previously [9]. Depending on curvature ratio and Reynolds number, a 1.5-to 500-fold reduction in axial dispersion was observed compared with that in a straight tube; this reduction was enhanced by an increase in Schmidt number.…”

“…For this Reynolds numbers range, the flow in the chaotic twisted pipe arrangement can be considered as fully chaotic in the whole section of the apparatus [15,19]. In this case, the dispersed plug flow model has been found suitable for a correct prediction of the RTD of the liquid, both in the chaotic and in the helically coiled systems [15], confirming previous experimental works dedicated to the latter configuration [9,10,21].…”

“…Depending on curvature ratio and Reynolds number, a 1.5-to 500-fold reduction in axial dispersion was observed compared with that in a straight tube; this reduction was enhanced by an increase in Schmidt number. Looking closely at the experimental data of Trivedi and Vasudeva [9], Saxena and Nigam [11] showed that a unique RTD was not really obtained, but rather a gradual narrowing of RTD curves with an increase in Dean number. Saxena and Nigam [11] argued that, starting with coils having large curvature ratios and for low Reynolds numbers, the RTD should shift from that for straight ducts to that for helical coils.…”

“…Trivedi and Vasudeva [9] reported an experimental study on residence time distribution in the low-Reynolds number and lowDean number region (Dn ≤ 11) in helical coils having curvature ratios, R c /D, ranging from 10.5 to 278. In these configurations, they obtained an essentially unique RTD curve which is narrower than that for straight ducts, confirming the theoretical results of Ruthven [5].…”

Study of mixing behavior of cstr using CFD

“…Also, RTD represent a tool in successful process scale-up of chemical reactors. Many researchers have carried out experiments and simulations (Arratia et al, 2004;Buflham, 1983;Danckwets, 1953 and1958;Hocien et al, 2008;Levenspiel and Turner, 1970;Martin, 2000;Robinson and Tester, 1986;Trivedi and Vasudeva, 1974;Turner, 1982;Xiao-chang et al, 2009;Yablonskya et al, 2009;Zwietering, 1959) on RTD of CSTR. Lipowska (1974) found the RTD of the reactor without and with baffles and moving stirrer.…”