An apparatus has been designed and constnlcted for the study of liq.uic1 film flow on flat surfaces of varioue inclinations with and without a counter-flow of gas. Experimental results ho.ve b-:~en obtained for the system water-air at chamJ.el slopes of 7?t° to 900 on the Im an film thickness, the velocities and wavelengths of the interfacial waves, the s urf2.ce velocity and wall shear-stress in the film, all as functions of the channel slope ~d the liquid and gas flow rates. Velocity profiles, wall and interfacial shear-stresses, and static pressure drops of the gas stream have been measured at 43 0 slope as functions of gas and li~uid flow rates and position along the channel. Numerous visual and photo0raphic obse_vat~ollS m the flow behaviour have been made, together V the cine--photographs for investigating mixing in the wave fronts. Theoretical calcu1ntions have l)een made of' the surface- tension edbe effect; the results ~re in moderate agreement will the experiments. The experimental results have been compared with published theories and data. The usual theories of wavy film fJ. OVJ have been found to be Applicable only at very low flow rates. It has been shown that the complex phenomena occuring in film flow can be represented on a lle-J?r-We network, and a systematic nomenclatu::ce has been proposed for the flow regimes The importance of the gas entry effect in calculatinG two-phase flows of the plesent type has been demonstrated, and both the liquid entry zone and the surface tension ed~e effect may have an important influence on mass transfer in film-type equipment.

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A method for solving compressible fluid flow problems is described. The convergence of the solver is accelerated with the use of a multigrid scheme where the coarse meshes are created in an automatic way, using grid agglomeration. For viscous flows, a methodology for the application of unstructured hybrid meshes is proposed. A geometrically conservative, second order scheme for flows involving geometry movement for these meshes is presented. The performance of the method is illustrated in several examples of inviscid and viscous, steady-state and time-dependent flow. The complexity of the geometries considered spans from two-dimensional aerofoils to complex aircraft configurations.

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During separation and concentration of macromolecular solutions flux losses have traditionally been ascribed to the well-known phenomenon of concentration polarization with the formation of a gel layer that is subsequently compacted. In the present investigation ultrafiltration was modelled in three separate stages with distinctive time constants. It was shown that in the first stage listing less than five seconds a quasi-steady state concentration profile is reached. In the second stage of one to ten minutes solute adsorption on the membrane surface including the pores controls the permeation rate. The rate of flux decline is highest at this phase. The third stage is governed by a reaction mechanism which produces a surface gel causing flux decline at a much slower rate than in the previous adsorption step. This polymerization of the protein to a gel on the membrane was shown to be second order in the surface protein concentrations. The differences in the flux pattern between single protein solutions and natural protein mixtures were attributed to a change of order of the polymerization mechanism. Another model was developed to estimate the properties of anisotropic membranes as well as their very high water permeation rates which cannot be predicted with the earlier formulae used for homogeneous membranes. A reproducible and inexpensive method has been developed to attach food-grade proteases onto the UP membranes which then retard the rate of formation of gel on the membrane. This was achieved by ultrafiltering-the enzyme solution for the first ten minutes instead of the protein to be separated and hence producing a primary adsorbed layer of protease molecules. 25% to 78% improvement in cumulative permeate yield was obtained in a standard 22 hr run when processing 0.5% albumin or haemoglobin. It was also demonstrated that the flux enhancements were due to the biochemical action of the adsorbed protease and not to its physical effect as a prefilter coat. Economics of the system were shown to be favourable, improving the rate of return on capital investment up to 50% by reducing the total membrane area of the plant. The enhanced fluxes with self-cleaning membranes were modelled by modification of the original model, i.e. by incorporating an enzyme activity term to counteract the deposition of gel on the membrane surface.

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