Conjugate Heat Transfer analysis on a Exhaust port using Ansys fluent

We have a wide experience in Engine CHT Analysis for various types of engines like bikes, passenger cars, racing cars, commercial vehicles, marine, agricultural equipment and earth-moving equipment, etc.

• The Exhaust port file is imported into the space claim by changing the unit system to m from mm. The heat transfer occurs in two modes in exhaust port by conduction at the pipe outer & by convection at pipe inside.

• Prepare --> extract volume is used to create a volume inside & also check whether any duplicate edges in the geometry if any delete using repair --> extra edges.

• Choose share under workbench so the walls between the fluid & solid share the edges & proper flow simulation occur. The pink color edge denotes the shared edge between the regions. 
• Create a baseline mesh & also create three named selection i) Inlet ii) Outlet.               iii) Outer wall convection. The mesh is used for the initial check for the setup.

Cell count  

• The Solver type  - Pressure-based, Velocity - Absolute, Time - Steady. The materials used are for solid - Aluminium & for the fluid - Air.
• The solver is initialized using a hybrid method. The contour plot for the temperature is created & also animation plot for the temperature contour is created.

Residual plot

Temperature plot

The inlet temperature is set to 700 k & as the flow progress, the temperature value decreases by the heat transfer process & steady state for the flow is obtained.

• Streamline plot is used to display a vector quantity, which is especially useful for visualizing fluid flow.

An XY plane is created to create plots along the flow outlet. By the law of conservation of mass, the flow of fluid inlet is equal to the flow of the fluid outlet, since the inlet diameter is very large when compared to the outlet dia, the velocity is increased at the outlet flow.

Velocity Plot

Heat Transfer Coefficient

CASE 2:

The mesh of the geometry is more refined to capture the physics properly. The inflation layer around the fluid wall is created to have accurate results over the convection & conduction heat transfer modes by creating the inflation named selection. The size of the mesh size is reduced to 10 mm. 

Cell count

Residual Plots

Temperature plot

Streamline plot

Velocity Plot

Heat Transfer Coefficient

Inference                                          

• The temperature plot for both the cases is almost equal & in the second case, the results are more accurate at inlet temperature.
• The max velocity in the first case is 38.1  m/s & in the second case, the max velocity is 40.9 m/s & variation of the velocity is around 7.5% whereas the mesh cell count increases by around 300 % but case 2 takes more time to attain convergence.
• From the table is clearly depicted that the value of the heat transfer coefficient is dependent on the cell count. HTC is a boundary layer concept & in case 2 we create inflation layers around the fluid layer to capture physics more accurately. The accuracy factor depends upon the element size, the total number of cells, mesh quality & inflation layer at the interface. So we can conclude that finer mesh produces accurate results.