Week 1- Mixing Tee

AIM:

To perform and analyze the steady-state simulation of mixing Tee of two different lengths (Short Pipe & Long Pipe) with two different momentum ratios.

GIVEN DATA:

• Hot inlet Velocity - 3 m/s
• Hot inlet Temperature - 36^oC
• Cold inlet Temperature - 19^oC
• Momentum Ratio - 2 & 4 (Short & Long)

SOLVING AND MODELING:

1. Open the SpaceClaim in the Geometry and then import the case setup of the model.
2. Select the Edges using the Prepare ---> Volume Extract ----> Select the Edges for the fluid volume.

MESHING:

1. Using the Face (Ctrl + F) option select the faces and N to name the face i.e. input x, input y, outlet, and Wall.
2. Go to Mesh right-click and generate Mesh.
3. Element Size - 0.001 has been increased to get accurate results.

POST-PROCESSING:

1. In ANSYS Work bench ---> Results the post-processing window will open the volume to visible.
2. Insert ---> Location ----> Plane ----> XY Plane. --->Color---> Variable---> Temperature ---> Set the Minimum and Maximum temperature.
3. To get the color for the temperature difference go to the wall double click and render option to make it transparency.

Use the Standard k-ε model when:

• Dealing with industrial applications with moderate computational resources.
• The flow does not involve strong adverse pressure gradients or swirling flows.
• General accuracy is acceptable, and computational efficiency is a priority.

Use the SST k-ω model when:

• Accuracy near walls and in adverse pressure gradient regions is crucial.
• Simulating complex flows with strong streamline curvature, rotation, or swirling motions.
• Computational cost is a secondary concern compared to accuracy.

CASE:1

SHORT PIPE

MOMENTUM RATIO-2

MOMENTUM RATIO-4

TEMPERATURE:

Momentum Ratio - 2 Momentum Ratio - 4

VELOCITY:

Momentum Ratio - 2 Momentum Ratio - 4

CASE:2

LONG PIPE

MOMENTUM RATIO-2

MOMENTUM RATIO-4

TEMPERATURE:

Momentum Ratio - 2 Momentum Ratio - 4

VELOCITY:

Momentum Ratio - 2 Momentum Ratio - 4

SLNO	PIPE TYPE	MOMENTUM RATIO	CELL COUNT	AVERAGE OUTLET TEMPERATURE	ITERATIONS
1	Short	2	576658	30.43	126
2	Short	4	576658	27.58	160
3	Long	2	765172	30.48	124
4	Long	4	765172	27.47	196

RESULTS:

Turbulence Models:

• Results from Realizable K-Epsilon and K Omega SST turbulence models yield similar average temperatures.
• However, the K Omega SST model requires more time and iterations for convergence.

Momentum Ratio and Outlet Temperature:

• A higher momentum ratio (4 in this case) leads to a significant drop in outlet temperature due to the influence of high-velocity cold air.
• Indicates that higher momentum ratios result in more efficient mixing.

Effect of Pipe Length:

• Short tee and long tee pipes show almost similar results for a momentum ratio of 4.
• Suggests that the length of the pipe doesn't significantly affect the efficiency of the pipe.

Standard Deviation:

• Long tee pipes have a lower standard deviation compared to short tee pipes.
• Increasing the inlet cold air velocity for short pipes can improve mixing efficiency.

Velocity and Mixing:

• Increasing velocity improves turbulent mixing.
• The majority of mixing is attributed to higher velocity, with additional mixing occurring along the length of the pipe due to diffusion.

Analytical vs. Numerical Outlet Temperature:

• Not much difference was observed between analytical and numerical outlet temperatures.