Theoretical analysis of a vertical multiple-effect diffusion solar still coupled with a tilted wick still

• Heat and mass transfer in the still was analyzed theoretically.
• Vapor from tilted wick still is transported to multiple-effect still.
• Solar energy is utilized adequately in multiple-effect still year-round.
• Distillate productivity would be about 18 kg/m2 day in average.

In this study, a combination of vertical multiple-effect diffusion solar still and tilted wick still is proposed and theoretically analyzed. The vertical multiple-effect diffusion still consists of a double glass cover and a number of vertical and parallel partitions in contact with saline-soaked wicks with narrow air gaps between the partitions. The moisture-rich layers of air in the tilted wick still and the multiple-effect still are connected so that the vapor evaporated from the wick of the tilted wick still can be transported to the humid air layer between the inner glass cover and the first partition of the multiple-effect still by natural convection. The latent heat of condensation of the vapor on the front surface of the first partition can be utilized as an added heat source for the multiple-effect still. It was found that solar energy utilized in the multiple-effect still would be adequate year-round. The total daily distillate production was predicted to be about 19.2, 16.0 and 15.9 kg/m2 day on the spring equinox and summer and winter solstices, respectively, when the diffusion gaps between partitions is 5 mm and the number of partitions is 10.