Boiling Enhancement by Using Nanofluid

The pool boiling behavior of water was experimently studied over a TiO2 nanoparticle-coated heater. The nanoparticle-coated wires were produced by boiling processes which submerge a pure nickel wire into nanofluid. Making nanoparticle-coated wires included two parameters: concentration of the nanofluids and heat flux.The concentrations of the nanofluids were 0.01%wt., 0.1%wt., and 1%wt., and the heat flux were 0 kW/m2, 500 kW/m2 and 1000 kW/m2. Furthermore, the contact angle measurement, SEM and EDS analysis were conducted to discuss the features of nanoparticle-coated wires.
The SEM and EDS results showed that nanoparticles were deposited on the heating surface during boiling processes. Besides, the thickness of the nanoparticle-coated surface was enhanced as concentrations and heat flux increased. The boiling curves indicated that heat transfer coefficient of nanoparticle-coated wires decreased as a result of thermal resistance which was generated by nanoparticle-coated surface. However, the CHF was enhanced due to its hydrophilic surface which measured by contact angle experiments, and the maximum CHF enhancement rate was about 87%. It is believed that CHF enhancement is mainly caused by the nanoparticle coating on the heating surface.
To test the reliability of nanoparticle-coated wire, boiling curve comparisons between nanoparticle-coated wire and used nanoparticle-coated wire were performed. The CHF and heat transfer coefficient decreased as using time increased. The modification of the heating surface was the main reason that heat transfer coefficient decreased. However, the relationship between contact angle and CHF disappear. Thus, the reason of CHF decrease is still unknown.