HVAC Definition - Forced Outlet


HVAC outlet conditions are defined in the same way as inlets. As the geometry file in this example already has HVAC surfaces defined the 'Select Triangles' option for 'planar' shapes will be used to define the outlets (Method 1 described in the previous section). If surfaces for HVAC inlets and outlets are not explicitly defined in the CAD model, then the 'From Points' option may be more applicable.


Ensure that the Building, 2D Lines, and Gas Turbine Enclosure 01.png layers are toggled off. Rotate the model (or use the view cube) to view the underside of the turbines. Press Ctrl + P to change the perspective to orthographic, this will remove the vanishing point and make the 3D window appear similar to a plot plan, as in Figure 18. It is not needed to change the perspective (Ctrl+P) but doing so can be helpful at times.


Tutorial 9 - Figure 18 - Orthographic view from bottom of geometry file



This section will add four outlets, one at each of the orange squares on the ceiling of the building (indicated by the red arrows in Figure 18):

  1. From the Add Items tab, select HVAC or Fans from the Select Item menu option

  2. Set the Type as Forced Outlet

  3. Leave the Name as its automatically defined one

  4. Set the Flow Rate to "5 m3/s"

  5. Choose the Shape as Planar, and the Method to From Triangles

  6. Use the Pick Tool to choose one of the orange squares indicated in Figure 18.

  7. Click the Preview checkbox to ensure that the direction of the flow is pointing towards the square and away from the turbines, as shown below.


    Tutorial 9 - Figure 19 - Showing a preview of the HVAC Outlet 01 (preview in red) pointing up into the orange square, note this is opposite direction from the inlet (purple)


  8. Click Add Item to add the HVAC outlet to the project.



Repeat steps 1 through 8 for the remaining 3 outlet locations, each should have a flow rate of 5 m3/s.


Tutorial 9 - Figure 20 - showing the four HVAC outlets (green) defined pointing into the ceiling of the building.



The flow rates for the HVAC definitions are important as the mass balance needs to be the same for the inlets and outlets, meaning the sum of the flow rates for all the inlets should equal the sum of all the outlets.


For this tutorial eight inlets at 2.5 m3/s results in a total of 20 m3/s. Thus, the four outlets needed to be set to 5 m3/s.


The next section will go over how to define the internal ventilation simulation with all 12 HVAC boundary conditions.