Time Scale Analysis for Prediction of Nusselt Number of Nanofluids Flowing Through Straight Tubes: An Experimental Study

Because of anomalous heat transport behavior in nanofluids, several possible mechanisms suggested by various authors to explain the thermal conductivity and heat transfer coefficient enhancement lack unanimity. Hence, this research article aims to explore convective heat transfer enhancement mechanisms by correlating them with observed experimental data of nanofluids. The analysis is carried out by comparing the order of magnitude of different diffusion mechanisms for different types of nanofluid systems. Four different types of nanofluids, Al2O3/EG-W (0.6, 0.9, 1.2, and 1.5 vol.%.), Al2O3/PG-W (1, 1.5, 2, and 2.5 vol.%.), CuO/PG-W (0.25, 0.5, 0.75 and 1 vol.%) and MgO/PG-W (0.3 and 0.66 vol.%) have been studied in this research. A generalized mechanism-based correlation has been proposed to predict the Nusselt number for these nanofluids, for flow through a straight tube under laminar conditions. Results showed that the Brownian motion is very slow in comparison to nano convection-diffusion and heat diffusion. The proposed model predicted the combined data for all the nanofluids studied well within a range of ±5%. Statistical errors of the proposed model were also calculated. Data from other authors were also validated using the proposed correlation, and the parity plot showed that the relationship predicted the data well within a range of ±15%.