Experimental study on the pool boiling performance of a highly self-dispersion TiO2 nanofluid on copper surface

Abstract

Enhancing heat transfer performance of pool boiling is attractive in practical applications, while the utilization of nanofluid is regarded as an effective approach. However, existing knowledge of boiling enhancement with nanofluid is still limited in terms of the influences of its type, concentration, deposition and boiling time. In this paper, the pool boiling performance of a highly self-dispersion TiO2 nanofluid with mass concentration from 0.0001% to 0.1% was experimentally investigated and compared with Al2O3 and ZnO nanofluid. The effect of boiling-induced deposition layer was studied by means of repeatability test, wettability test and macro/micro morphology test. Results indicated that a super-hydrophilic micro-porous deposition layer formed on nanofluid boiling surface and led to nearly twice higher CHF than distilled water, and nanofluid itself had negligible influence on CHF enhancement. Increasing concentration of nanofluid led to occasional falling off of the deposition on surface and resulted in complicated and unpredictable boiling performance. Nanofluid type and concentration had limited influence on CHF, whose value kept around 1800 kW/m2. 0.0001% TiO2 and Al2O3 nanofluids had similar boiling curves, but ZnO nanofluid exhibited lower heat transfer coefficient. Finally, a novel criterion to predict the occurrence of film boiling in advance was proposed based on wall superheat change rate threshold. The present study will contribute to design guidance and security control of nanofluid-based pool boiling device.