Flux Prediction in Direct Contact Membrane Distillation

Membrane distillation (MD) is a potential mean of water desalination. MD is a thermally driven desalination technology that has been employed in four basic configurations. One of these configuration is Direct Contact Membrane Distillation (DCMD). In DCMD, both hot and cold solution is maintained in direct contact with micro porous hydrophobic membrane material. Heat and mass transfer analysis was performed on DCMD. Based on Kinetic theory of gas, the performance of different models of membrane permeability (coefficient) was investigated under different DCMD operating parameters (feed temperature, coolant temperature and feed flow rate). Knudsen number provides the guideline in identifying the type of model of mass transfer to be considered under any given experimental conditions. Results revealed that for a given pore size under the same simulation and experimental conditions, Transition (Knudsen- Molecular diffusion) type of flow model predictions is in good agreement with the experimental results. Hence the best model to be consider for flux prediction in DCMD. The effect of membrane pore size was also studied. Results showed that permeate flux increases with increase in pore size up to the critical pore condition where the flux prediction remain constant (unchanged).

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