Small-scale low pressure 'single effect distillation' and 'single stage flash' solar driven barometric desalination units: A comparative analysis

Worldwide water scarcity signifies an urgent need to develop sustainable, simple to operate, low-cost, small-scale desalination units especially suitable for remote communities. The single effect distillation (SED) and the single stage flash (SSF) type low-pressure barometric desalination units satisfying the above requirements have attracted great interest in academic circles, but a comparison of the two has never been attempted. Thus, analytical models have been developed to identify and evaluate common performance indication parameters. The main results of the analysis show that the SSF unit's heat input rate is ~30% greater than that of the SED unit, with a resulting decrease in its performance ratio of ~24%, in comparison. Consequently, the brine heater area of the SSF is ~3.25 times the evaporator area of the SED. Furthermore, the seawater feed rate in the SSF is also about 20 times greater, leading to a 20 times larger release of non-condensable gases into its condenser. This additionally results in the SSF unit's 'recovery factor' of only 3.3%, as compared to ~67% in the SED unit. These results reveal that the solar-driven barometric SED type units have a considerably better performance in all comparison aspects over the SSF type units.