From July to December 2015 I was a PostDoc at Massachusetts Institute of Technology, MIT, Boston in the research group of Professor John Lienhard. During my stay, I studied the convective transport processes in membrane channel flows. First results have been presented the 68th APS Meeting in Boston. A poster is available for download.
Laminar channel flows with periodic obstacles are present in many heat and mass transfer applications, e.g. membrane technologies such as electro-dialysis or spirally wound membrane modules. For process design, classical scaling laws are typically used, which scale the transfer (Sherwood) number, Sh, to the hydrodynamic Reynolds number, Re, the fluid specific Schmidt number, Sc, and to some dimensionless geometric parameters, Dh, in a classical form like Sh = C · Rea· Scb · Dhc. However, the validity of those scaling laws is limited to regions where the concentration boundary layer develops. It is well known that the transfer numbers approach a constant (Reynolds and Schmidt independent) value in the developed region of a laminar channel flow.
This present study examines numerically the validity of the scaling laws if the channel flow is interrupted periodically by cylindrical obstacles of different size and separation distance.
Rohlfs, W., Lienhard V, J.H.: Entrance length effects on Graetz number scaling in laminar duct flows with periodic obstructions: Transport number correlations for spacer-filled membrane channel flows, Int. J. of Heat and Mass Transfer, 97, 842-852, 2016.
I greatefully thank the German Academic Exchange Service (DAAD) for the financial support.