Natural Convection Cooling of a Heat Source Placed at the Bottom of a Square Cavity Filled with Water-Based Nanofluid

Abstract

The present work deals with the cooling process of a heat source, placed in the center of the bottom wall of a square cavity. A numerical resolution using finite volume method was carried out. The cavity is filled with a water-based Nanofluid, where four different types have been assumed. The vertical and top walls are under low temperature TC. Two thermal conditions were assumed at the source (q-imposed or T-imposed), while the remaining parts of the same wall are isolated. The effects of Rayleigh number (Ranf), source length (SL), volume concentration of nanoparticles (Φ) and their types were analyzed. The case of pure water (Φ = 0%), studied first, served as a reference case. The results obtained for this case, showed the increase of disturbances in the dynamic and thermal fields, in addition to the average rate of heat transfer (Nu) when Ra increases and SL decreases. SL = 1.0 case showed exception. These effects are more important for the T-imposed case than the other. Subsequently, the Al2O3-Water Nanofluid is considered with 0 <Φ≤ 10%. An increase in circulation intensity with improvement of local (Nu) and average (Nu) heat exchange rates have been recorded when Φ increases, although mentioning that its effect is significantly stronger for the q-imposed case. In the last part of the work, three other types of Nanofluids were assumed, where the obtained results showed the main improving effect of higher thermal conductivity on the heat transfer intensity. An important result which can be summed up in the great rapprochement of the heat exchange intensities for strong Ranf and Φ for SL close to 1.0, for the two heating types. In other words, the condition on the source loses its importance for such considerations.