Investigation of heat transfer characteristics of Al2O3-water nanofluid in a coiled agitated vessel across varied operating conditions

This study aimed to investigate the heat transfer behavior of an Al 2 O 3 -water nanofluid within a coil-agitated tank. The experiment utilized Al 2 O 3 -water nanofluids with varying volume concentrations, namely 0.2 vol%, 0.3 vol%, and 0.4 vol%. Two different cooling water flow rates, specifically 1.8 and 2.2 liters/min, were employed during the investigation. The propeller speed ranged from 2 to 12 (rps), and the temperature spanned from 30 to 80 °C. The findings revealed that the heat transfer coefficient of the nanofluids exceeded that of the base water. Moreover, it increased with higher volume concentrations, reaching its peak at 0.4 vol% with an average rise of approximately ±77.2%. Additionally, the heat transfer coefficient demonstrated an increase of about ±19.8% when the temperature was elevated to 80 °C and approximately ±11.9% when the propeller speed was raised to 12 rps. Comparing the two distinct flow rates, it was observed that the heat transfer coefficient rose with decreasing flow rate to 1.8 liters per minute, exhibiting an average enhancement of approximately ±13.6%.