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FDS Examples

Simple Air Conditioning in a Room

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.

2. Mesh

The compute volume is divided into several meshes.
The meshes increase in definition as their proximity to the input extraction VENTs increases.

&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.

&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./