Numerical Investigation of Non-Newtonian Nanofluid Flow in Spiral Pipe

Fluids can be classified from different perspectives. From the perspective of fluid behavior under the influence of shear stress, the fluids can be classified into Newtonian and non-Newtonian fluids. Newtonian fluid is a material in which shear stress without yield stress (at zero shear rate is zero shear stress) is only a linear function of shear rate and in this material shear stress to shear rate is called viscosity. In non-Newtonian fluids one of the two Newtonian fluid conditions (zero yield stress condition or shear stress linearity condition in terms of shear rate) or both conditions are not met simultaneously. In other words, it can be said that a non-Newtonian fluid is a fluid in which either the shear stress diagram is nonlinear in shear rate or if the diagram is linear it does not cross the origin of the coordinates.In this study, non-Newtonian fluid flow in spiral tubes with different cross-sections is investigated. Three circular, oval and square cross sections are provided for the spiral tube and the fluid flow is investigated in steady and three-dimensional state. For numerical simulation, the commercial software Ennis Fluent, which is a subset of Ennis software, is used specifically to simulate fluid flows. For different Reynolds numbers, different cross-sectional area of pipe and different torsion steps, mean Nusselt number, local Nusselt number, vorticity, friction coefficient and pressure drop have been measured and the influence of the mentioned parameters on each of the variables has been investigated. . It is shown that the spiral tube with a square cross-section generally exhibits the best thermal performance, followed by a spiral tube with an elliptical cross-section. In general, the spiral tube with a circular cross-section shows the weakest thermal performance among the three cross-sections examined. This equation can be found in the hydraulic diameter of the cross -section so that the hydraulic diameter of the square cross-section is obtained by 4, while the hydraulic diameter of the circular cross-section is 2. Thus the hydraulic diameter of the square cross -section is approximately twice that of the circular cross-section. For example, for a spiral tube with a circular cross-section and a volume fraction of 4: the average Nusselt number is approximately equal to the average Nusselt number for a spiral tube with a square cross-section and a volume fraction of 4: and an input rate of 5.5 m / s.

کلیدواژه ها:

Spiral pipe ، Non-Newtonian fluid ، Numerical simulation ، Fluent software.