Performance and energy evaluation of compact multistage air gap membrane distillation system: An experimental investigation

A new design of compact multistage air gap membrane distillation system is experimentally tested for possible scaling up and commercialization. The performance of the new system is then investigated by studying the impacts of the operating variables on the permeate flux. Parallel and series flow arrangements are tested, and the energy efficiency is evaluated by the gained output ratio and the specific thermal energy consumption at different operating variables. In addition, the evaluation of system production cost of freshwater is carried out. Results reveal that both the permeate flux and the gained output ratio increase with increasing the feed temperature, feed and coolant flow rates and decreases with increasing the coolant temperature. The specific thermal energy consumption and the production cost decrease with increasing the feed temperature, feed and coolant flow rates and decreases with decreasing the coolant temperature. The compact system produces up to 13 kg/m²h (24 L/day). The parallel flow arrangement is slightly better than the series arrangement in terms of productivity. In contrast, the series flow arrangement is better in terms of energy efficiency.