Influence of Module Length on Water Desalination Using Air Gap Membrane Distillation Process: An Experimental Comparative Study

The impact of the membrane module length on the air gap membrane distillation (AGMD) process performance was investigated experimentally under various operating parameters. In this work, two different lengths of the AGMD module (i.e., 0.59 m and 0.28 m) were tested separately to get the optimum in terms of lower energy consumption and higher water output. The mechanism of mass and heat transfer in the AGMD process is considered as well. The experimental results were subjected to the two-way analysis of variance (ANOVA) to examine the significant influence of operating parameters and modules at p < 0.05. Also, the results were subjected to simple linear regression analysis to measure the relationship between the operating parameters (independent variables) and the performance indicators (dependent variables). Statistical analysis carried on the experimental data manifested that the feed temperature parameter brought a highly significant difference (p < 0.001*) on the water output (P-w) and temperature difference ( increment T-cross). However, feed temperature had a non-significant effect (p > 0.05) on the gained output ratio (GOR), energy consumption (STEC), and heat input (Q(H.I)). Under optimal operating parameters of a flow rate of 18 L/h, feed temperature of 60 degrees C, coolant temperature of 20 degrees C, and feed salinity of 5000 mg/L, the P-w and GOR were increased by 64.50% and 50.00%; the STEC and Q(H.I) were reduced by 57.78% and 34.09%, respectively, from the long module to the short one. Thence, changing the length of the membrane module from 0.59 to 0.28 m promoted remarkably the performance of the AGMD process.