Numerical modeling of the vacuum membrane distillation process

• A model of a hollow fiber vacuum membrane distillation module is proposed.
• The energy, momentum balance and heat and mass transfer equations are simultaneously solved.
• The mathematical VMD model is validated in comparison with the previous results.
• The effect of the module dimension and operation condition on the VMD performance is demonstrated.

In this study, one-dimensional vacuum membrane distillation (VMD) model is suggested for predicting the performance of seawater desalination to evaluate the performance of hollow fiber type VMD module. The energy and momentum balance equations, as well as the heat and mass transfer equations, are simultaneously solved to determine the concentration of NaCl, temperature and velocity distribution of feed side along the module length, productivity of distilled water and specific energy consumption. The productivity increases with an increase in the inlet feed temperature and velocity, the number of fibers and the total module length. However, it decreases with an increase in the mass fraction of the feed. Specific heat energy consumption decreases with an increase in the inlet feed temperature and velocity and total module length, but it increases with an increase in mass fraction of the feed and number of fibers. The specific electrical energy consumption increases with an increase in mass fraction, velocity and total module length and a decrease in inlet feed temperature and number of fibers, but the specific electrical energy consumption is too small and negligible in comparison with the specific heat energy consumption (less than 2%) on various operating conditions and module dimensions.