Novel method for the design and assessment of direct contact membrane distillation modules

An equivalent effectiveness-number of transfer units (ε-NTUMD) method was developed for direct contact membrane distillation. Efficient performance rating and design sizing for individual DCMD modules can be rapidly made based upon limited experimental data. Using this method, the construction of a specific finite element model and their associated costs, involving both time and expenditure, are avoided. Instead the module performance or sizing requirements can be estimated efficiently using a set of expressions based on the conventional ε-NTU expressions used for the design of heat exchangers. The outlet temperatures are also predicted which is useful for the design of the overall DCMD process and module cascading networks. The ε-NTUMD method was validated against an experimentally validated discretized model of a flat sheet DCMD module, built using MATLAB. A correction function is included in the ε-NTUMD method proposed which results in 100% of the derived data being accurate within 6% of model results. Method validation was done for both co- and countercurrent flow, with a range of module dimensions, flowrates and membrane permeabilities.