Non Newtonian Nano Fluid Heat Transfer, Paper Numerical Validation, ANSYS Fluent Training

Description

Project Description

The present project is going to simulate the heat transfer and the flow of a Non-Newtonian fluid containing nanoparticles inside a tube by ANSYS Fluent software. The base fluid contains water and substances called xanthan which, due to the solubility of xanthan in the water, has the properties of non-Newtonian fluids. This non-Newtonian fluid contains Nano aluminum oxide (Al2O3) to increase the rate of heat transfer. This simulation was carried out by two-dimensional for simplification, considering the heat flux in the wall. For the non-Newtonian fluid simulation, the Herschel-Bulkley model is used in the viscosity tab.

Assumption (Non-Newtonian)

There are several assumptions used for the present simulation:

The solver is Pressure-Based, and the simulation is Steady. Also, the simulation is performed as axisymmetric.

Geometry & Mesh

The present 2-D modeling is done using Design Modeler software. Due to the simulation of the flow in the tube and the symmetry in it, only one plane of symmetry is modeled. The meshing of the present model was done using ANSYS Meshing software with a structured type. Also, due to the physics of the problem and the existence of heat transfer and better flow simulation along the walls, a near-wall boundary layer mesh is used.

Non-Newtonian Fluid Flow CFD Simulation

We present summaries of the problem definition and problem-solving steps in the table:

Models
Laminar	Viscous model
Herschel-Bulkley	Viscosity
on			Energy
Boundary conditions (Non-Newtonian)
velocity inlet	Inlet type
1.269787769 m/s	Velocity magnitude (Re=900)
1.732714752 m/s	Velocity magnitude (Re=1600)
295 K	Temperature
Pressure outlet	Outlet type
0 Pa	gauge pressure
300 K	backflow total temperature
wall			Walls type
No slip	Shear condition
8846.4 W.m-2	heat flux
Solution Methods
simple			Pressure-velocity coupling
Second order	pressure		Spatial discretization
Second order upwind	momentum
Second order upwind	energy
Initialization
Standard	Initialization method
295 K	temperature

Boundary Condition (Non-Newtonian)

At the inlet, the velocity inlet boundary condition is set where the velocity value is entered at two different Reynolds in this section for the different simulations and at the inlet temperature is 295 Kelvin. The thermal heat flux condition is introduced. At the symmetry part of the pipe, the axis condition and at the outlet condition the pressure outlet is applied by atmospheric pressure and in the thermal part, it has a backflow temperature of 300 Kelvin.

Reference Value

Since the purpose of the problem is to investigate the heat transfer and fluid behavior only in the fluid zone, we select the fluid flow inside the tubular space as the reference zone.

Validation (Non-Newtonian)

In this project, we simulate a non-Newtonian fluid flow with the help of Computational Fluid Dynamics (CFD).
We compare the CFD results with the article results for the validation.

“Modeling of forced convective heat transfer of a non-Newtonian nanofluid in the horizontal tube under constant heat flux with computational fluid dynamics”.

We select Figure 3, part “a” as the target diagram for validation,  in two Reynolds 900 and 1600 simulations and we compare the results of the heat transfer coefficient with the paper.

The following table presents the results of this simulation:

Error (%)	Present Results	Paper Results
1.43	1676.070374	1700	Re=900
5.53	1846.789	1750	Re=1600

As you can see in the table above, the error is low, and the simulation results have a good accuracy.