Effect of alumina nanofluids on bubble dynamics and heat transfer under quiescent conditions

Abstract

Thermal management of high heat loads is a relevant problem in various industrial applications. Nanofluids used in pool boiling based cooling systems are pointed as an attractive solution, but controversial results reported in the literature preclude a wider use of such cooling solutions. On the other hand, high costs are often reported to the fabrication of small quantities of nanoparticles, so cost-effective solutions are needed. Despite of the extensive research performed on pool boiling heat transfer of nanofluids, detailed studies on bubble dynamics and on their relation with pool boiling heat transfer is still scarcely reported in the literature. Hence, the present work addresses the effect of a cost-effective nanoparticle (alumina, Al2O3) in pool boiling heat transfer of water based nanofluids. The analysis performed here combines high-speed visualization with time and space resolved thermography to relate bubble dynamics and heat transfer. Results show that although alumina particles do not significantly affect single bubble dynamics, they result in a significant heat transfer enhancement. Hence, concentrations of 3wt% of Al2O3 lead to 38% in surface temperature reduction compared to that observed with water and an increase of 61% in the heat transfer coefficient. However, additional studies must be performed to infer if the use of such high nanoparticle concentrations is effectively beneficial, given the resulting issues (e.g. stability problems).

Keywords

• Nanofluids
• Pool boiling
• Heat transfer enhancement
• Nanoparticles concentration
• Bubble dynamics