Direct contact membrane distillation: An experimental and analytical investigation of the effect of membrane thickness upon transmembrane flux

Polyvinylidene fluoride (PVDF) electrospun nanofibrous membranes (ENMs), consolidated with a heatpress process and of various thicknesses were fabricated and tested in a DCMD cell at five different operating conditions. Membranes as thin as 27 mu m were sufficiently robust for evaluation and gave a transmembrane flux as high as GO L/h m(2). An analytical model was created to estimate the optimal membrane thickness for DCMD operations. It is found that the value of optimal thickness increases with reduced heat transfer coefficients; decreased teed inlet temperature; increased membrane permeability; and increased salinity. Even for 10% NaCl the predicted optimum was estimated to be 13 mu m which was Loo thin for experimental confirmation. Based upon this analysis but with due allowance for the variation of heat transfer coefficients with temperature dependent physical properties a single Matlab model was created to fit the five sets of data With the introduction of a structural derivation factor, which reflected the experimentally determined variation of porosity and pore size with thickness, the model was found to fit the data very well. (C) 2014 Elsevier B.V. All rights reserved.