Modelling mass transport within the membrane of direct contact membrane distillation modules used for desalination and wastewater treatment : scrutinising assumptions

A two-dimensional numerical model for a direct contact membrane distillation (DCMD) module, mostly used for desalination and wastewater treatment, has been created. This model has been used to explore the sensitivity of the simulated transmembrane flux of water vapour of the modelled distillation module to some of the commonly-used assumptions and simplifications related to the mass transport in the membrane, namely: equimolar diffusion; Knudsen diffusion-free mass transport; and binary gas mixture. The model has been also used to assess the impact of a slight total pressure difference across the membrane. The sensitivity of the transmembrane flux to the above assumptions has been then evaluated with relatively low and high inlet feed temperatures. The outcomes of the model have been presented, discussed and finally summarised.