Week 1- Mixing Tee

Aim:

For this challenge, we have created two versions of the mixing tee. One of them is longer than the other.

Your job is to set up steady-state simulations to compare the mixing effectiveness when hot inlet temperature is 36⁰C & the Cold inlet is at 19⁰C.

Use the k-epsilon and k-omega SST model for the first case and based on your judgment use the more suitable model for further cases. Giving the reason for choosing a suitable model is compulsory.

1. Case 1
• Short mixing tee with a hot inlet velocity of 3m/s.
• Momentum ratio of 2, 4.
2. Case 2
• Long mixing tee with a hot inlet velocity of 3m/s.
• Momentum ratio of 2, 4.

Momentum ratio = velocity at cold inlet / velocity at hot inlet

In a table, compare the following values from the 2 cases.

1. Cell count
2. Average outlet temperature
3. Number of iterations for convergence

Procedure:

Creating Geometry:

• Importing the geometry to Ansa geometry work bench.
• Now click on Prepare then choose the volume extractor.
• After click on volume extractor click on select edges.
• Now select some of the round edges of the mixing Tee.
• As you have extracted the volume solid.
• Close the geometry module.

Creating Mesh:

• Open the Mesh module.
• Model will automatically load then go to geometry.
• Select the faces option or click ctl + f to select the faces.
• Select the round faces and click N to name the face.
• Name all the mixing tee faces as inlet, outlet, walls.
• Then go to Mesh option select the Default and go to element size and type mesh = 0.002m.
• Now right click on Mesh option and click Generate the mesh.
• The Mesh will be generated.
• Now As we have generated the mesh close the mesh module.

Creating Setup:

• Opening the Setup module.
• Model will automatic load.
• Check for the quality optional.
• Now select the Physics option check on the energy option.
• Click on viscosity and check the K epsilon method and check Realized and hit OK.
• Now go to Cell zone check for the fluid as Air.
• Then go to Boundary condition and set inlet-x and inlet-y ratios and momentum condition.
• Go to solver select the pressure-based, Absolute and steady.
• Now go to definition and set the area weighted average as pressure and velocity report and standard deviation report click ok.
• Now by setting and the option go to initialize and initialize the data.
• It will give u 10 iteration value.
• Now set the no of iterations as 150 and Hit the RUN option.
• Now it will take some time depends on the no of mesh cell are there.
• Our graph and report will generated.

Creating Result:

• Opening the Result module.
• Checking the walls and inserting a plane1.
• Making the walls transparent to see the flow.
• Selecting the XY plane and creating Z axis as 0.
• Now enabling the Temperature in colors and apply.
• Now we can see the flow distribution on the plane.
• By checking the fixed option and setting the value to 2 decimal points.
• By checking the velocity option and setting the value to 2 decimal points.
• We have generated the flow in Mixing Tee.

MIXING TEE SHORT:

Meshing:

Fluent Setup:

Residuals:

Velocity:

Temperature:

Flow Result:

Temperature

Velocity:

Momentum = 4

Temperature:

Velocity:

Flow Result:

Temperature:

Velocity:

As shown in the above similarly we have to do for Mixing Tee long.

MIXING TEE LONG:

Geometry:

Meshing:

Fluent Setup:

Momentum = 2

Velocity:

Temperature:

Flow result:

Tmeperature:

Velocity:

Momentum = 4:

Velocity:

Temperature:

Flow Result:

Temperature

Flow velocity:

Conclusion:

Hence for this challenge, we have created two versions of the mixing tee. One of them is longer than the other.

so we prefer K-epsilon method is better for free flow in mixing tee because it doesn't effected by walls.