Analysis of Fluid Flow and Heat Transfer in a mixing elbow using ANSYS Fluent

Published on 01 Apr 2021. Written by Dineshkumar E

In this CFD project, you will use ANSYS to analyse the fluid flow and heat transfer in a mixing elbow. Mixing elbow is used in piping systems of power plants and process industries to find the flow field and temperature field in the region of the mixing section which helps to fix the position of inlet pipes. 

Before starting the project here is an overview of the problem which we are going to solve - Now a cold fluid (20C) is going to enter through the large inlet and it is going to get mixed with the warmer fluid (40C) which enters through a smaller inlet at the elbow. For the flow at the large inlet, the Reynolds number is 50,800,  hence the turbulent flow model will be needed.

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SLNOTE
Project Implementation:

Step 1: Launch ANSYS Fluent and make sure the required settings are enabled such as Embed Graphics windows, Display mesh after reading, workbench color scheme, etc. and load the mesh file.

Step 2: Change the mesh display by selecting graphics and animations in the navigation pane, then keep the view as front.

Step 3: Now we will do the mesh related settings - go to navigation pane select general and check the mesh. After checking the mesh look the minimum volume values if it is negative ANSYS will not begin the calculation.

Set the units properly using the scale option and check the mesh.

Step 4: Goto models enable energy equation and viscous model to perform heat transfer operations.

Step 5: Create a material by giving the following properties Density-1000kg/m3, Cp - 4216 J/kg-K, Thermal Conductivity-0.677 W/m-K, Viscosity - 8e-04 kg/m-s.

SLLATEST
Step 6: Set the cell zone conditions for the created fluid.

Step 7: Now give the boundary conditions for the cold inlet. Similarly set the boundary conditions for the hot inlet.

For the outlet set the boundary conditions using Boundary conditions option and pressure outlet-7. Also, set the boundary condition for the pipe wall.

Step 8: Start the calculation with residual plotting. If you didn’t get the result from the first-order discretization perform second-order discretization for all listed equations.

Step 9: Recreate the computational mesh after changing the geometry in ANSYS DesignModeler with the help of the duplicated system.

Adjust the mesh based on the temperature to enhance the forecast of the temperature field.

Step 10: After performing the calculations twice compare the results using CFD post.

Conclusion:

Two solutions are compared one using the first-order discretization which is ANSYS default scheme and the original mesh and the other using the second-order discretization and the adapted mesh which clearly shows the second is less diffusive. It is suggested that to use the first-order solution to start a calculation which uses high-order discretization scheme.

In this problem, you will get more accurate results if you solve the flow-field solution first because all properties are constant since the flow field is separated from temperature. During this procedure to turn on/off the solution of the equation you can use Equations dialogue box.

SLDYK
Kit required to develop Analysis of Fluid Flow and Heat Transfer in a mixing elbow using ANSYS Fluent:

• ANSYS

Technologies you will learn by working on Analysis of Fluid Flow and Heat Transfer in a mixing elbow using ANSYS Fluent:

• ANSYS
• CFD
• Mechanical

Any Questions?