A novel thermal desalting process using a binary string-of-beads flow array

The large mass transfer spacing in conventional solar stills causes a large mass transfer resistance and low space utilization. Convection mass transfer in vertical diffusion stills is always inhibited at small spacing due to the commonly used planar wicks. This paper presents a binary string-of-beads flow array for solar desalination using fibers instead of planar wicks, thus solving those problems and enabling coupled diffusion-convection mass transfer at small spacing. A prototype of our novel distiller with 16 mm mass transfer spacing and its experimental system are set up. Salt contamination, likely caused by splashing, is found to be tolerable at feedwater flows less than 50 L/h. At a saline water inlet temperature of 80 °C, the maximum thermal-water conversion efficiency reaches 0.81, and the maximum water productivity per unit volume reaches 56.3 kg/h/m³. Higher energy and space utilization than conventional stills and single effect vertical diffusion stills is demonstrated. A calculation model for heat and mass transfer between cold and hot water column pairs is developed for the first time, and the deviation between the calculated and experimental water productivity is less than ± 20%. This research may provide new ideas for efficient freshwater production in remote off-grid areas.