Crystal layer growth with embedded carbon-based particles from effervescent tablet-based nanofluids

Crystallization occurs as dissolved substances gradually solidify into crystal layers within a liquid, which can increase the capability of fluids to transfer heat. In this study, the growth of crystal layer in nanofluids produced from carbon-based effervescent tablets was examined. The tablets were fabricated by combining multi-walled carbon nanotubes (MWCNTs), sodium dodecyl sulfate (SDS), sodium phosphate monobasic (NaH₂PO₄), and sodium carbonate (Na₂CO₃). The effervescent tablets were formulated with MWCNTs, NaH₂PO₄, and Na₂CO₃ at a weight ratio of 1:5.1:2.26, respectively. These tablets were then immersed in distilled water (DW) and seawater (SW) to produce 0.05 vol.% to 0.15 vol.% MWCNT suspensions. Then, the dispersion stability, thermal conductivity, and crystal layer growth of the nanofluids were characterized. The results showed that the DW-based nanofluids were more stable than their SW-based counterparts. Additionally, the 0.05 vol.% DW-based suspension exhibited greater long-term stability than those of the 0.15 vol.% suspensions, whereas the SW-based nanofluid exhibited the opposite behaviour. The greatest increases in thermal conductivity were 3.29% and 3.13% for 0.15 vol.% MWCNTs in DW and SW, respectively. The crystallization process occurred in nanofluids that contained more than 0.05 vol.% MWCNTs and exhibited a greater growth rate in SW-based suspensions with high effervescent agent concentrations.