Experimental performance evaluation of multiple-effect diffusion stills under high heat flux

Active stills equipped with additional energy supply devices for enhancing productivity can select the amount of heat flux supply. However, most previous studies have been conducted at a heat flux below 1.0 kW/m(2), which can be obtained naturally, and only a few investigated heat flux optimization. In this study, the optimal heat flux and feed flow rate of an active multiple-effect diffusion still (MEDS) were evaluated experimentally at a high heat flux above 1.0 kW/m(2) to maximize its performance. An MEDS with 15 effects was fabricated, and its performance was investigated according to the feed flow rate under a heat flux range of 1.0-2.5 kW/m(2). The results showed that the freshwater production efficiency in terms of performance ratio (PR) increased with heat flux up to 2.18. The MEDS achieved 8.7 kg/(m(2)center dot h) at 2.5 kW/m(2). The optimal feed flow rate was identified based on the heat flux at which the MEDS exhibited the maximum output. The cost analysis showed that the MEDS using waste heat has a very attractive water cost of 1.0-3.0 $/m(3) at high heat fluxes, which is competitive with even other conven-tional desalination technologies. Therefore, the active MEDS at higher heat flux shows better performance and lower water cost.