Membrane Surface with Dimples in Vacuum Membrane Distillation

Objectives: This work presents a study of the effect of membrane surface with dimples on the heat transfer in vacuum membrane distillation (VMD). Methods/Statistical Analysis: Polyvinylidene fluoride (PVDF) membrane and distilled water as feed solutions are tested in a laboratory-scale cross-flow flat-sheet membrane module with membrane area of 72.4 cm2. A perforated aluminum support embedded in the permeate compartment is used to support the membrane during the VMD process. Findings: The results show that the dimples stamped on the membrane surface by the perforated support having the diameter and depth approximately 5 and 1 mm, respectively. The permeability of the membrane with dimples increases by 3 - 20% at the corresponding feed temperature of 75 - 95°C. The deviations between the heat transfer coefficients predicted by a Nusselt correlation with dimpled effect and the experimental values are less than 10%. Application/Improvements: These findings are significant to reveal the influence of membrane deformation effect on the heat transfer correlation which is used to predict the VMD flux.