Analysis of a multi-stage air gap diffusion distillation system powered by low-grade sensible heat

A novel multistage air-gap diffusion distillation (MS-AGDD) system powered by low-grade sensible heat (LGSH) was proposed for fully recovering heat from LGSH to produce freshwater. The effect of operating parameter variations on the system performances was investigated theoretically based on the epsilon-NTU model for AGDD. The operating parameters include the hot water inlet temperature (T-hs(in)), the feed seawater flowrate (V-c,n(in)), salinity (S-c,n(in)) and temperature (T-c,n(in)), the temperature differences at the hot end of heat exchanger (Delta t(h)) and at the cold end of coolers (Delta t(c)). Results showed that under the given structure and size parameters of the system and the operating conditions, the variation of T-hs(in), V-c,n(in) or Delta t(h) affected the system performances significantly, but the variation of S-c,n(in) n or Delta t(c) affected those relatively less. The total freshwater yield and the recovered heat from the hot water enlarged with the increase of T-hs(in) or V-c,n(in), but they decreased with the increase of Delta t(h). The gained out ratio (GOR) of the system increased with the increase of T-hs(in), but it decreased with the increase of V-c,n(in) or Delta t(h). The irreversibility of the system increased with the increase of T-hs(in) or Delta t(h), but it decreased with the increase of T-c,n(in) or V-c,n(in).