Magnetic Field Effect on Nanofluid Heat Transfer (MHD)

Magnetic Field Effect on Nanofluid Heat Transfer (MHD), ANSYS Fluent CFD Simulation Training (3-D)

In this project, nanofluid flows in a solid aluminum channel in the presence of an applied magnetic field are simulated by ANSYS Fluent software. Fluid flow is steady and is simulated as one single-phase flow, however, the thermophysical properties of nanofluid are calculated using the below formulas. The surface average of the nanofluid’s temperature is equal to 293.2 and 304.175K at the inlet and outlet, respectively.

where are density, viscosity, specific heat, and thermal conductivity coefficient of nano-fluid and volume fraction of nano-particles in fluid.

Geometry and mesh

The geometry of the fluid domain is designed in Design Modeler and the computational grid is generated using Ansys Meshing. The mesh type is unstructured and the element number is 26000.

CFD Simulation

Critical assumptions:

• The solver type is assumed Pressure Based.
• Time formulation is assumed Steady.
• Gravity effects are neglected.

The following table is a summary of the defining steps of the problem and its solution.

Solver configuration Models
Energy	On
Viscous	K-epsilon (standard)	Standard wall function
MHD model	MHD method	Magnetic induction
	Solution control	Solve MHD equation (on)
		Include Lorentz force (on)
		Include Joule heating (on)
		Under relaxation (0.9)
	Boundary condition	Solid outer wall (insulating wall)
		Fluid-solid interface (coupled wall)
	External field B0	B0 input option (patch)
	B0 component	Bx amplitude (1T)
		By amplitude (0T)
		By amplitude (1T)
Solver configuration Materials
Fluid	Definition method	Fluent Database
	Material name	NanoFluid (based on water, with modification)
	Density	1312 kg/m3
	Specific heat (Cp)	3248 J/kg.K
	Thermal conductivity	1.09387 w/m.K
	Viscosity	0.0011 kg/m.s
	UDS diffusivity	constant
	Electrical conductivity	1000000 siemens/m
	Magnetic permeability	1.257e-6
Solid	Definition method	Fluent Database
	Material name	Al (based on Aluminum with modification)
	Density	2719 kg/m3
	Specific heat (Cp)	871 J/kg.K
	Thermal conductivity	202.4 w/m.K
	UDS diffusivity	constant
	Electrical conductivity	3.541e7 siemens/m
	Magnetic permeability	1.257e-6
Solver configuration Cell zone conditions
Fluid	Material name	NanoFluid
	Source terms	Mass (0)
		X momentum (1)
		Y momentum (1)
		Z momentum (1)
		Turbulent kinetic energy (0)
		Turbulent dissipation rate (0)
		Energy (1)
		B_x (1)
		B_y (1)
		B_z (1)
Solid	Material name	Aluminum
	Source terms	Energy (2) 1.       UDF MHD energy source 2.       1000000 w/m3
		B_x (1)
		B_y (1)
		B_z (1)
Solver configuration Boundary conditions
Inlet	Type	Velocity inlet
	Velocity magnitude	1 m/s
	Turbulence intensity	5%
	Turbulent viscosity ratio	10
	Temperature	293.2 K
Outer Wall solid	Temperature	320 K
Solver configurations
Pressure-velocity coupling	Scheme	SIMPLE
Spatial discretization	Gradient	Least square cell-based
	Pressure	Second order
	Momentum	Second order Upwind
	Turbulent kinetic energy	First order upwind
	Turbulent dissipation rate	First order upwind
	Energy	Second order Upwind
	B_x	First order upwind
	B_y	First order upwind
	B_z	First order upwind
Initialization	X velocity	1 m/s
	Temperature	293.2 K

Magnetic Field Effect on Nanofluid Heat Transfer Results and discussion

The nanofluid flow average temperature at the inlet and out location is 293.2 and 304.175K respectively. In case of no magnetic field affecting the nano-fluid, the temperature at the outlet decreases to 303.74K. Heat flux to nanofluid is equal to 112102.2 w/m2.

Comparison between outlet temperature of nano-fluid in the presence and absence of magnetic field, reveals the effectiveness of magnetic field application in the present work. Magnetic field application increases outlet temperature by 1K and heat transfer to nano-fluid by 200w/m2.