THEORETICAL AND EXPERIMENTAL-STUDY IN MEMBRANE DISTILLATION

The performance characteristics of an air gap membrane distillation (A GMD) process for water desalination were investigated by conducting tw o long-run experiments. In the first test an 8-week continuous experim ent was carried out using a PVDF membrane of 0.45 mum pore diameter. T he second test consisted of a 6-week run using a PTFE membrane of 0.5 mum pore diameter. Furthermore, the effect of hot side temperature, co ld side flow rate and feed concentration were investigated. The experi mental results obtained showed that the mass flux was steady over time and that it was affected only slightly by an increase in salt concent ration. Permeate quality was dramatically affected when membrane wetti ng occurred, the cold side flow rate had a negligible effect on the pe rmeate flux and the flux exponentially increased with an increase in h ot side temperature. The effect of temperature gradient on mass transf er was clarified by applying the theory of non-equilibrium thermodynam ics. The Soret coefficient indicates that the thermal diffusion coeffi cient is negligible in comparison with the actual mass transfer coeffi cient of the process.