In this FDS example a simple HVAC system in a room is simulated.
1. Description
In a room with dimensions of 5.4 x 3.6 x 2.82 m, the HVAC system is simulated by introducing and extracting air.
- Initial ambient temperature: 27 ° C
- Air inlet temperature: 17 ° C.
As you will see in the .fds file, the initial temperature is specified via the command & MISC TMPA = 27. /
while the input temperature is specified directly on the SURF line of the input VENT through the TMP_FRONT variable.
The system is activated 10 seconds after the start of the simulation.
![](https://fdstutorial.com/wp-content/uploads/2021/03/image.png)
2. Mesh
The compute volume is divided into several meshes.
The meshes increase in definition as their proximity to the input extraction VENTs increases.
![](https://fdstutorial.com/wp-content/uploads/2021/03/image-2-1024x593.png)
&MESH ID='Mesh 01', IJK=28,120,10, XB=0,0.84, 0,3.6, 2.52,2.82/
&MESH ID='Mesh 02', IJK=76,60,5, XB=0.84,5.4, 0,3.6, 2.52,2.82/
&MESH ID='Mesh 03', IJK=14,60,10, XB=0,0.84, 0,3.6, 1.92,2.52/
&MESH ID='Mesh 04', IJK=38,30,5, XB=0.84,5.4, 0,3.6, 1.92,2.52/
&MESH ID='Mesh 05', IJK=7,30,16, XB=0,0.84, 0,3.6, 1.92,0/
&MESH ID='Mesh 06', IJK=19,15,8, XB=0.84,5.4, 0,3.6, 1.92,0/
3. HVAC supply and exhaust vents
The supply and input VENTs are entered as follows (see this FDS tutorial for a complete description of the parameters that regulate the input and extraction vents).
3.1 Supply
&VENT XB=0,0,0.4,1.4,2.7,2.76, SURF_ID='supply', DEVC_ID='timer'/
&SURF ID='supply', VOLUME_FLOW = -0.133, TMP_FRONT= 17. ,COLOR='CYAN' /
3.2 Exhaust
&VENT XB=0,0,2.2,3.2,2.7,2.76, SURF_ID='exhaust', DEVC_ID='timer'/
&SURF ID='exhaust', VOLUME_FLOW = 0.133, COLOR='BLUE' /
3.3 Timer device for supply and exhaust
&DEVC ID='timer', QUANTITY='TIME', XYZ = 1,1,1, SETPOINT=10, INITIAL_STATE=.FALSE. /
4. Outputs
As outputs there are slice files that measure the speed and temperature of the air in the environment.
![](https://fdstutorial.com/wp-content/uploads/2021/03/image-1.png)
&SLCF PBY = 0.72, QUANTITY='VELOCITY', VECTOR=.TRUE./
&SLCF PBY = 2.16, QUANTITY='VELOCITY', VECTOR=.TRUE./
&SLCF PBY = 3.60, QUANTITY='VELOCITY', VECTOR=.TRUE./
&SLCF PBY = 0.72, QUANTITY='TEMPERATURE', VECTOR=.TRUE./
&SLCF PBY = 2.16, QUANTITY='TEMPERATURE', VECTOR=.TRUE./
&SLCF PBY = 3.60, QUANTITY='TEMPERATURE', VECTOR=.TRUE./