Effect of multi-staging in vacuum membrane distillation on productivity and temperature polarization

MSVMD (multi-stage vacuum membrane distillation) has recently gained attention as means of enhancing the performance of single stage configuration. The present study is aimed to analyze the impact of multi-staging in VMD (vacuum membrane distillation) on productivity and the associated temperature polarization. Another goal is to determine the point of inversion, a point after which further multi-staging is no more beneficial both in terms of permeate productivity (flux) and associated temperature polarization. After validation with the experimental data, a parametric analysis of MSVMD performance is carried out numerically. Further, the permeate productivity and associated temperature polarization phenomenon were analyzed simultaneously under varying membrane specifications. The optimum number of stages, giving the maximum possible performance of MSVMD, is estimated for variation in most prominent process variables and membrane specifications. The point of inversion was found to be above 40 stages for varying process variables, however, it remained well below 20 stages for variation in some of the prominent membrane characteristics.