Desalination of Brackish Water Utilizing Air Gap Membrane Distillation at Two Different Cooling Water Levels

Abstract

In this work, the effect of two different cooling temperatures (Tc) on the permeate flux (Fp) and thermal efficiency (η) of air gap membrane distillation (AGMD) module was studied experimentally. All data were described statistically in terms of means, standard error for means (SE), standard deviation (SD) and coefficient of variation (C.V.). Data were subjected to the analyses of the variance (ANOVA) and multivariate analysis to test the significant effect of different feed and designs at pf) and flow rates (Mf). Experimental results revealed that the percentage of AGMD permeate flux was reduced by 4.71%, 4.98%, 7.51%, 1.84%, 2.71%, 8.20%, 2.25% and 4.42% at increasing cooling temperature from 10 to 20 oC, respectively, in case of flow rate (Mf) of 2.0 and 4.0 L/m (temperature Tf of 50 oC), 6.0 and 8.0 L/m (temperature Tf of 50, 60 and 70 oC) due to lowering the temperature and vapor pressure differences between the hot and the cold feed at both sides of the membrane (ΔTcross=T1-T4). Regarding thermal efficiency (η), an opposite result was obtained whereas the thermal efficiency was improved significantly at increasing cooling temperature from 10 to 20 oC at all different operating conditions. The rate of increasing in thermal efficiency were around 1.26, 1.29, 1.15 and 1.27 times at flow rate Mf of 2 L/m and different temperature Tf of 50, 60, 70 and 80 oC, respectively.