Numerical Investigation of DE-AGMD Desalination Using RSM: Seeking Optimal Performance

A double‐effect membrane distillation (DE-AGMD) process was developed by equipping air gap membrane distillation (AGMD) with internal heat recovery. In this arrangement, the latent heat of the first effect will be recycled as a source of heat for the second effect. More produced water without adding energy. This configuration improves the efficiency of the process, and SEC (specific energy consumption) decreases. The potentialities of DE-AGMD to desalt seawater were investigated. Response surface methodology (RSM) is used to model and optimize the operating parameters for water desalination by DE-AGMD. Permeate flux ( Jp ) and salt rejection ( R %) were the main performance responses to optimize. The temperature difference (Δ T ), width of air gap (δ), feed flow rate ( Q f ) and cooling solution flow rate ( Q c ) were the operating parameters investigated to optimize the performance of DE-AGMD. The obtained quadratic regression model is validated by analysis of variance (ANOVA). The high values of R 2  = 99.86 and R 2 adj = 99.7 confirmed that the quadratic equation properly fitted the experimental data. The optimal operation parameters are found to be 52.28 °C for the temperature difference, 25.62 L h −1 for the feed flow rate, 23.87 L h −1 for the permeate flow rate and 3 mm for the air gap width. Under these conditions, the permeate flux could reach 4.69 L m −2  h −1 . The experimental and predicted results show a good agreement confirming the fit of the models by 97.78%. The modeling of salt rejection is found to be difficult due to the steadiness of response for all experimental runs (> 97%).