Effect of TiO2–SiO2 hybrid nanofluids on enhanced oil recovery process under different wettability conditions

This work presents a study of using the Wilson Plot method to determine the convective heat transfer coefficient (CHTC) of the following nanoparticles in water as the base fluid: SiO₂, TiO₂, and Al₂O₃. The experiments were carried out in a double layer concentric glass tube in which the hot fluid and nanofluids exchange heat in a counter current fashion without direct contact. Attention was also given to the volumetric concentration, flow rate, and the size of nanoparticles to investigate their effects on CHTC. From the experiments, it was found that by adding nanoparticles, the CHTC of water can generally be enhanced and a 45% increase has been achieved with a 0.5 vol% concentration of Al₂O₃ nanoparticles at an intermediate Reynolds number around 4100. Moreover, simply reducing nanoparticle size and increasing the nanofluid flow rate do not necessarily lead to the CHTC enhancement, rather, they have adverse effects. It is concluded that the enhancement depends on the stability of the dispersed nanoparticles that can be characterized by their overall mean size and zeta potential as useful measures.

This paper presents an experimental investigation of two-phase liquid-gas flow across a sudden expanded diameter in a horizontal pipe. A closed flow loop having a transparent pipe was designed and...

In this paper, separating and reattaching aqueous laminar flows produced by a sudden inward expansion within confined annular geometries are experimentally studied. The test geometries are based on a previous numerical study. The fluid flow structure at the expansion region is experimentally characterized using particle image velocimetry combined with refractive index matching. The detailed measurements of the velocity field, reattachment length, and relative eddy intensity are obtained for two different expansion ratios, 1.4 and 1.6. For both expansion ratios, the reattachment length is found to vary nonlinearly with the Reynolds number $(50<Re<600)$, in line with numerical predictions. The eddy intensity is found to depend strongly on both the Reynolds number and expansion ratio with the relationship between the Reynolds number and the reattachment length being nonlinear. Overall, the corresponding numerical predictions are in good agreement with the measurements undertaken herein.