Enhancement of nanofluid stability and critical heat flux in pool boiling with nanocellulose.

A nanofluid, which is an aqueous fluid with nanoparticles, is an attractive medium for enhancing critical heat flux (CHF); however, its instability over a long period of time due to sedimentation and aggregation has impeded its successful application in industry. In this study, lightweight negatively charged TEMPO-oxidized cellulose nanofibers (CNFs) were utilized as a nano-sized substance in water and examined to enhance both the CHF performance and thermal stability of nanofluids. Owing to low density of the CNFs and long range repulsion between negatively charged CNFs, there were no aggregation and sedimentation of CNFs with multiple boiling/cooling cycles. In addition, with CNF concentrations of 0.01, 0.03, 0.05, and 0.10 wt%, CHF enhancement increases of 40.7%, 45.1%, 54.9%, and 69.4%, respectively, were achieved over that of pure water. The present results demonstrated the great potential of CNFs as eco-friendly and cost-effective nano-substances that can overcome the instability of nanofluids.