Thermohydraulic performance of Al2O3-water nanofluid during single-phase flow and two-phase subcooled flow boiling

Abstract

This study presents the thermohydraulic performance of Al2O3-water nanofluid in single-phase and two-phase subcooled flow boiling in a horizontal copper tube. The results of a three-dimensional Eulerian-Eulerian CFD model are validated with the experimental data. Having the model validated, a comprehensive parametric analysis is conducted on the effect of Reynolds number, heat flux, and volume concentration of nanoparticles on the hydrothermal performance of the heat exchanging tube. The HTC in the flow boiling regime is increased by ∼73% compared to the single phase. The heat transfer and pressure drop increased through the addition of nanoparticles to the base fluid in single-phase and two-phase flows. However, its effect is more pronounced in case of single-phase flow. Increasing the heat flux on the tube wall is associated with a slight increase in the heat transfer coefficient (HTC) and a significant decrease in the pressure drop. The HTC and pressure drop increase by moving to higher Reynolds number. The vapor volume fraction of nanofluid was lower than pure water due to a higher heat transfer and lower wall temperature. The maximum PEC (performance evaluation criterion) of 1.25 and 1.19 is found in case of single- and two-phase flows.