Heat and mass transfer simulation and experimental evaluation of solar powered vacuum membrane distillation system
Water and energy scarcity in dry and remote areas is a well understood issue and becoming even more pronounced in the future due to the impact of climate change. Research on solar powered desalination techniques in these places is growing worldwide to produce fresh water using renewable sources of energy. Membrane distillation processes are technically simple and capable of producing high-quality potable water over a long period with minimal maintenance. With regard to the attractive advantages of the vacuum membrane distillation (VMD) process, it is a promising technology that can be implemented by the use of solar energy. The aim of this paper is not only to develop a mathematical model describing heat and mass transfer processes across a VMD process using thermal renewable energy, but also to implement innovative design to improve the overall performance of a solar powered vacuum membrane distillation (SVMD) system. In the present work, a small pilot-scale SVMD unit was designed, assembled and tested. The dependency of the predictive model to natural climatic conditions is assessed and validated against experimental data. Theoretical flux data of the proposed SVMD pilot plant is then graphed via a numerical solution in order to compare with experimental results. The influence of salinity concentration on the permeate flux is explained. Finally, sensitivity analysis of the simulated model showed that the permeate flux is highly sensitive to pressure, solar irradiance and flow rate values.