Smart role of Al2O3-water suspension on laminar heat transfer in entrance region of a channel with transverse in-line baffles

This study aims to two dimensionally evaluate laminar flow and heat transfer characteristics of Al2O3-water nanofluid in the entrance region of a baffled parallel plate channel. The mixture model, based on a single fluid two phase approach, with temperature-dependent properties is adopted to simulate nanofluid. A constant heat flux is imposed on the walls. The effect of Reynolds number, nanoparticle volume fraction and heat flux on wall temperature, velocity and pressure fields, and thermal-hydraulic performance are numerically investigated. It is found that the intensity and length of recirculation regions of flow in the baffled channel increases and decreases, respectively, as nanofluid is applied. The results reveal more uniform wall temperature profiles are obtained using nanofluid, especially for lower Reynolds number and higher volume fraction. Using nanofluid has more remarkable effect on reducing temperature in front of baffles in which hot spots occur. Because of this superior feature, the nanofluid under study plays an intelligent role in cooling applications of baffled channel. Both heat transfer and pressure drop increase when nanoparticles are dispersed in basefluid. The baffled channel shows better cooling performance at the presence of nanoparticle while imposed heat flux is increased. This potential of nanofluids proves that it can be called "smart fluid". It means that nanfluid plays automatically more effective role as heat transfer medium when temperature increases and then higher heat dissipation is required. It is also found that the effect of nanofluid on both heat transfer and pressure drop is approximately independent from baffle shape and the baffled channel presents a better thermal hydraulic performance under the condition of constant inlet velocity. (C) 2016 Elsevier Ltd. All rights reserved.