Home / Examples / Fluid Analysis [Bernoulli] / Example 20: Room Ventilation (Air of Humidity)

Example 20: Room Ventilation (Air of Humidity)

General

• The case where the air of 60% humidity flows into the room of air of 30% humidity through its window is analyzed.
  The case where the air of 30% humidity flows into the room of air of 30% humidity from the door is analyzed.
  

• A comparison has been made between two cases: one taking into account the weight of water vapor, and the other not.
  

• See [Diffusion Analysis] for setting 30% and 60% humidity.
   

• Unless specified in the list below, the default conditions are applied.
  

• Simulation Time: around 50 min

 

• Obtain this session's project file. (Right-click and choose 'Save link as')

• 
  

• Results will vary depending on Femtet version and the PC environment.

 

Analysis Space

Item	Settings
Analysis Space	3D
Model Unit	m

 

Analysis Conditions

Item	Tab	Settings
Solver	Solver Selection	Fluid Analysis [Bernoulli]
Analysis Type	Fluid Analysis	Transient Analysis
Timestep	Transient Analysis	Timestep: Specify   No. Number of Calculation Steps Output Interval Timestep [s] 1 180 5 1
Diffusion Analysis	Fluid Analysis	Select Diffusion Analysis
Diffusion Analysis Setting	Fluid Analysis	Analysis type: Transient Analysis Type and Unit of Diffusion Quantity: Molar Concentration   Ambient Value (Default Value): 0.3834 [mol/m3] See [Diffusion Analysis] for setting 30% humidity. Initial Value: Use ambient value   Take into account buoyancy: Analysis Model Settings Buoyant (Take into account buoyancy) Select Take into account weight of diffusing materials.. Select [300_Water Vapor H2O] in the material DB and click [Input]. No_Buoyant Do not take into account buoyancy. Deselect Take into account weight of diffusing materials..
Pressure Correction	Fluid Analysis Setup Details	Select Correct the pressure condition to balance with buoyancy.
Meshing Setup	Mesh	General Mesh Size: 0.3 [m]

 

Model

The air domain is shown as below. The model represents a room with a ventilator, a door, and a window. The door and the window are assumed to be opened.

Body Attributes and Materials

Body Number/Type	Body Attribute Name	Material Name
5/Solid	Room	000_Air *

* Available from the material DB

Boundary Condition

Boundary Condition Name/Topology	Tab	Boundary Condition Type	Settings
Door/Face	Fluid	Inlet/Outlet	Natural Inflow/Outflow Diffusion Analysis Setting Select Use Ambient Value.
Window/Face	Fluid	Inlet/Outlet	Natural Inflow/Outflow Select [Direct Entry]. 0.7668 [mol/m3] See [Diffusion Analysis] for setting 60% humidity.
Fan/Face	Fluid	Outlet	45 [m3/min]

 

Results

The streamlines of the flow coming from the window at 180 [s] is shown below.

If buoyancy is not taken into account, a direct flow toward the ventilator is observed, and if buoyancy taken into account, a flow circulating around the top of the room toward the ventilator is observed.

 

Take into account buoyancy	Do not take into account buoyancy

 

 

The contours of molar concentration after 180 [s] are shown below.

If buoyancy is taken into account, the area of high humidity spreads around the top of the room.

 

Take into account buoyancy	Do not take into account buoyancy