Effects of buoyancy and centrifugal forces on the nanofluid mixed convection in a 3D curved horizontal microtube using a two-phase mixture approach.

The purpose of this study is numerical investigation, the laminar flow hydrodynamic and mixed convection of water-copper nanofluid in a microtube by applying the two-phase mixture method. This 3D simulation is run at Re = 10, Ri = 0.1 - 10 ) and volume fraction of nanoparticles φ = 0–6% through Finite Volume Method. The nanofluid flow is assumed Newtonian, assessed in a horizontal microtube of 90 ∘ curvature angle. The objective is to assess the impact of the buoyancy and centrifugal forces on the flow in a bent geometry. In this research, the interpretation and investigation of Nusselt Number (Nu), coefficient of friction and temperature distribution in three-dimensional macrotube with changes in volume fraction and Richardson number will be discussed. The results reveal that the nanofluids' hydrodynamic properties and behavior next to their heat transfer in bent geometries vary from those of other geometries and flat surfaces while being more trajectory dependent. The average Nusselt number and the average friction factor in the inner, outer, top, and bottom regions of the microtube strongly depend on the Ri number and φ. The increase in φ promotes the micron heat transfer mechanisms in the microtube, thus, an enhancement in the heat transfer rate. The variations in velocity components and the buoyancy and centrifugal forces are among the most influential factors on hydrodynamic and heat transfer parameters like the friction factor and Nu number. The value of the local Nu number has an ascending trend when the φ increases in the initial stage of the flow from the inlet section to the middle of the path. This is while the local Nu number decreases as the φ increases after the 45 ∘ curvature upward. The increase in the friction factor level from the entrance up to 45 ∘ angle is due to the more substantial effects of buoyancy and centrifugal forces. [ABSTRACT FROM AUTHOR]