Direct-contact membrane distillation configuration

Direct-Contact Membrane Distillation Configuration If the mean free path of the transported molecules is large in comparison with the membrane pore size (i.e., Kn > 1 or dp < X.,)> the molecule-pore wall collisions are dominant over the molecule-molecule collisions, and the Knudsen type of flow is responsible for mass transfer through the membrane pore. In this case the permeability through each pore in the Knudsen region was expressed as follows (Matsuura, 1994 Khayet et al., 2004a) ... 

The most common configurations of PMRs with suspended photocatalyst are those utilizing pressure driven membrane processes, such as microfiltration (MF), ultraflltration (UF) and NF. In other types of PMRs, photocatalysis is combined with dialysis, pervaporation (PV) or direct contact membrane distillation (DCMD, MD) (Mozia, 2010). 

Figure 6.12 Common configurations used for membrane distillation (a) DCMD.direct contact membrane distillation (b)AGMD, air-gap membrane distillation (c) SGMD,sweep gas membrane distillation and (d)VMD, vacuum membrane distillation (Caputo etal.,2007).

An aqueous solution colder than the feed solution is maintained in direct contact with the permeate side of the membrane, giving rise to the configuration known as direct-contact membrane distillation (DCMD). Both the feed and permeate aqueous solutions are circulated tangentially to the membrane surfaces by means of circulating pumps or are stirred inside the membrane cell by means of a magnetic stirrer. In this case the transmembrane temperature difference induces a vapor pressure... 

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