Development of candle soot dispersed phase change material for improving water generation potential of tubular solar distillation unit

Solar still is an economical device for purify brackish water, however its yield is low. Therefore, present work aims to increase the water output of tubular solar still (TSS) by introducing closed mild steel tubes filled with paraffin wax (as phase change material, PCM) and candle soot derived carbon nanoparticles (CSNP, 0.3 wt%) as dispersant for the first time. Experiments were conducted with three TSS – one with conventional TSS without any PCM, and the other two with only PCM and 0.3 wt % CSNP-PCM to augment the water production. There was an increase in thermal conductivity of 40.59% with 0.3 wt % CSNP over the base PCM. TGA analysis showed excellent thermal durability of 0.3 wt % CSNP-PCM and final degradation temperature was 314.26 °C. In addition, the dispersion of CSNP in PCM also altered the phase change temperatures with meager deviation from base case. The thermal performance analysis of TSS show that full day cumulative fresh water generation by conventional TSS was 3.04 kg/m², whereas utilizing the PCM and 0.3% CSNP-PCM in tube inside TSS augmented the water generation by 42.4% and 87.82% respectively, than the baseline case. In addition, the modified TSS with PCM and 0.3 wt % CSNP-PCM exhibited higher energy efficiency of 59.26% and 109.94% respectively, than the base line case. The generated fresh water cost was only 0.014 $/kg for TSS with 0.3% CSNP-PCM. It is concluded that conductive CSNP doped PCM with excellent thermal performance significantly enhanced the water output of the SS and could be widely applied in other design of still for better thermal performance.