Abstract: In this work, the performance of a modified double slope still (MDSSS) was evaluated compared to conventional single slope one (CSS). The modifications depended on different additives, namely: copper chips, copper oxide (CuO) nanoparticles/fluid, and paraffin wax as phase change material (PCM). First, the proposed materials were characterized to determine the thermophysical properties and the best ratios. As resulted, the copper chips, and nano-enhanced materials (water and PCM) had higher thermal conductivity than bulk water, and pure materials, respectively. Beyond the characterization, three cases of MDSSS were investigated compared to CSS: copper chips immersed in CuO/water nanofluid (1.5 wt%) (case I), integrating pure PCM container below the basin containing the previous materials (case II), and using nano-based PCM (15 wt%) instead of the pure PCM (case III). Moreover, the thermo-economic performance was evaluated by determining the efficiencies of the first and second laws of thermodynamics and the freshwater cost. As found, all cases showed good performance improvements, and case III was the best from both production and thermo-economic considerations. For this case, the productivity, energy efficiency, and exergy efficiency were enhanced by 113, 112.5, and 190%, respectively, relative to CSS. In addition, the freshwater production cost was saved by 35.3%.
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