Step 3: Defining Input and Output Parameters in ANSYS FLUENT and Running the Simulation

You have now started setting up the CFD analysis using ANSYS FLUENT. In this step, you will define input parameters for the velocity inlet, set output parameters for the evaporator and heat exchanger volumes, define heat source boundary conditions for the evaporator and heat exchanger, then calculate a solution.

1. Define an input parameter called in_velocity for the velocity at the inlet boundary.

This displays the Velocity Inlet dialog box.

a. In the Velocity Inlet dialog box, select New Input Parameter... from the drop-down list for the Velocity Magnitude.

This displays the Input Parameter Properties dialog box.

e. Retain the value of 10 for Turbulent Intensity.

f. Enter 0.061 for Hydraulic Diameter (m).

2. Define an input parameter called in_temp for the temperature at the inlet boundary.

a. In the Thermal tab of the Velocity Inlet dialog box, select New Input Parameter... from the drop-down list for the Temperature.

b. In the Input Parameter Properties dialog box, enter in_temp for the Name, and enter 310 for the Current Value.

3. Set the turbulence parameters for backflow at the front outlets and foot outlets.

Boundary Conditions → outlet-front-mid-1 → Edit...

a. In the Pressure Outlet dialog box, select Intensity and Hydraulic Diameter from the Specification Method drop-down list in the Turbulence group box.

b. Retain the value of 10 for Backflow Turbulent Intensity (%).

c. Enter 0.044 for Backflow Hydraulic Diameter (m).

These values will only be used if reversed flow occurs at the outlets. It is a good idea to set reas-onable values to prevent adverse convergence behavior if backflow occurs during the calculation.

d. Click OK to close the Pressure Outlet dialog box.

e. Copy the boundary conditions from outlet-front-mid-1 to the other front outlets.

Boundary Conditions → Copy...

i. Select outlet-front-mid-1 in the From Boundary Zone selection list.

Scroll down to find outlet-front-mid-1.

ii. Select outlet-front-mid-2, outlet-front-side-left, and outlet-front-side-right in the To Boundary Zones selection list.

iii. Click Copy to copy the boundary conditions.

FLUENT will display a dialog box asking you to confirm that you want to copy the boundary conditions.

iv. Click OK to confirm.

f. Repeat the preceding steps to set the following backflow turbulence conditions for outlet-foot-left and outlet-foot-right.

Value Parameter

Intensity and Hydraulic Diameter Specification Method

Backflow Turbulent Intensity (%) 10

0.052 Backflow Hydraulic Diameter (m)

4. Set the Solution Methods Solution Methods

a. Select Coupled in the Scheme drop-down list.

The pressure-based coupled solver is the recommended choice for general fluid flow simula-tions.

b. Select First Order Upwind for Momentum and Energy in the Spatial Discretization group box.

This tutorial is primarily intended to demonstrate the use of parameterization and design points when running FLUENT from Workbench. Therefore, you will run a simplified analysis using first order discretization which will yield faster convergence.

5. Initialize the flow field.

Solution Initialization

a. Retain the default selection of Hybrid Initialization.

b. Click the Initialize button.

6. Define an output parameter called vol_evap for the volume integral at the evaporator cell zone.

Reports → Volume Integrals → Set Up...

This displays the Volume Integrals dialog box.

The value for the Total Volume of the evaporator will be used later in this tutorial.

a. In the Volume Integrals dialog box, select fluid-evaporator from the Cell Zones list.

b. Select the Volume option under Report Type.

c. Click the Compute button.

d. Click the Save Output Parameter button.

This displays the Save Output Parameter dialog box.

e. In the Save Output Parameter dialog box, keep the Create New Output Parameter option selected, enter vol_evap for the Name, and click OK to close the dialog box.

7. Define an output parameter called vol_heat_ex for the volume integral at the heat exchanger cell zone.

a. In the Volume Integrals dialog box, deselect fluid-evaporator and select fluid-heat-ex-changer from the Cell Zones list.

b. Select the Volume option under Report Type.

c. Click the Compute button.

d. Click the Save Output Parameter button.

e. In the Save Output Parameter dialog box, keep the Create New Output Parameter option selected, enter vol_heat_ex for the Name, and click OK to close the dialog box.

8. Define a heat source boundary condition for the heat exchanger volume.

Cell Zone Conditions → fluid-heat-exchanger → Edit...

a. In the Fluid dialog box, select Source Terms.

b. In the Source Terms tab, scroll down to Energy, and click the Edit... button.

This displays the Energy sources dialog box.

c. In the Energy sources dialog box, change the Number of Energy sources to 1.

d. For the new energy source, select constant from the drop-down list, and enter 0.

e. Click OK to close the dialog box.

9. Define a heat source boundary condition for the evaporator volume.

Cell Zone Conditions → fluid-evaporator → Edit...

b. In the Source Terms tab, scroll down to Energy, and click the Edit... button.

c. In the Energy sources dialog box, change the Number of Energy sources to 1.

d. For the new energy source, select constant from the drop-down list, and enter -787401.6 — based on the evaporator load (200 W) divided by the evaporator volume (0.000254

) that was computed earlier.

e. Click OK to close the dialog box.

In the Cell Zones Conditions task page, click the Parameters... button to open the Parameters dialog box where you can see all of the input and output parameters that you have defined in ANSYS FLUENT.

These parameters are also available in ANSYS Workbench.