Fig. 5: A scalable cascaded TDD device.
a The structure of the Burgers cascade. a1 The Burgers cascade contains many small cells; each cell is a small parallel-plate channel. In a single cell, the working fluid is divided into two streams, top and bottom, denoted by red and blue arrows respectively. For the entire Burgers cascade, the top is hot and the bottom is cold. The hot stream (red arrow) flows towards the top-left cell outlet and has a lower concentration for thermophobic species, while the cold stream (blue arrow) flows to the bottom-right outlet and has a higher concentration. Water flows in the m direction, where m is a row and n is a column. a2 Photo of a transparent miniature with M = 5 and N = 10 showing the lateral spread of dye after injection close to the device inlet. Details of this experiment are provided in Supplementary Fig. 12. b Contour plot of the concentration in each cell. C0 = 30,000 ppm, ΔT = 60 K, ST is assumed to be 1.8 times of that of NaCl in water. M = 185 and N = 20 (b1) and M = 490 and N = 35 (b2). When the cut-off distance is 10% of the total distance, i.e. the recovery rate Rw is 10%, the yield concentration Clow = 5000 ppm (b1) and 1000 ppm (b2), respectively. c The concentration of the cold stream is plotted along the flow direction (when N = 20) for different recovery rates. Two different feedwater concentrations are considered, C0 = 30,000 and 60,000 ppm, with the same assumptions as in (b) were applied. Drinking water here is defined as water with salt concentration less than 1000 ppm. Lower recovery rate means larger ΔC. d The yield concentration when expanding the size of the Burgers cascade fixing Rw to 10%. By expanding the size of the Burgers cascade, seawater can be desalinated to drinking water standard. For different levels of target salinity, the corresponding size M is indicated by coloured labels.
