Boundary thickness reduction

The author had realized that in the two papers referenced by the reviewer no film collapse was observed as the speed continuously decreased. Instead, the film thickness reduction is in many cases slower than that predicted by the conventional EHL formulae, and the curve is often pretty much leveled when the film becomes very thin, in the range of several nano-meters or a few tens of nanometers. This is actually the phenomenon caused by the boundary film, instead of the EHL film. The two papers were well written focusing on the topic of boundary film formation.The boundary film is more complicated, related to complex lubricant and interfacial chemistry and physics. However, what... 

In practice, it is sometimes possible to incorporate moving blades in the filter equipment so that the thickness of the cake is limited to the clearance between the filter medium and the blades. Filtrate then flows through the cake at an approximately constant rate and the solids are retained in suspension. Thus the solids concentration in the feed vessel increases until the particles are in permanent physical contact with one another. At this stage the boundary between the slurry and the cake becomes ill-defined, and a significant resistance to the flow of liquid develops within the slurry itself with a consequent reduction in the flowrate of filtrate. 

Data is shown in Figs. 7a and 7b for oxygen reduction on carbon steel in room temperature 0.6M NaCl. iL increases with co0 5 as predicted. Hence if the corrosion rate is determined by the mass transport of oxygen to the disk surface to support oxygen reduction, then the corrosion rate will increase as a function of the rotation rate, co, raised to the 0.5 power and linearly with dissolved oxygen concentration. The diffusion boundary layer thickness, 8d, may be calculated from Fick s first law after iL is determined. Recall that 8 = nFDCJiL for one dimensional diffusion at the steady state. This leads to the following expression for the diffusional boundary layer thickness ... 

The permeate flux increases with increasing feed velocity due to the reduction of the boundary layer thickness. Therefore, the temperamre and concentration at the liquid-vapor interface are approaching values close to those in the bulk solution. Garcia et al. [71] have observed that the feed pressure measured at the inlet of the feed cell frame increased with an increase in the feed flow rate consequently increasing the risk of membrane wetting. 

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