HVAC in FDS 5.5.3

[Sam J]

Hi,

I was wondering if the HVAC features were functional in FDS 5.5.3 code. I see the HVAC features described in the FDS 5.5.3 manual but when I run a case with HVAC VENT connected to AMBIENT NODE with a DUCT, I did not measure any flows through the vent. The same case has flows through the vent when ran in FDS 6.5.3. The only error I got when trying to run the FDS6 HVAC setup in FDS 5.5.3 was to do with DUCT PERIMETER. After I took out the DUCT PERIMETER, the input file ran, but there were no flows through the VENT as discussed.

I understand that the general (and correct) belief on here is to be progressive and always use the latest code i.e. FDS 6.5.3. Just wondering out of curiosity if anyone who still remembers FDS 5.5.3 has a simple explanation why this would not work in the old release? 

Thanks

Sam

[Sam J]

While we are on this topic of HVAC VENTS, I have another question. Lets assume I keep using the latest release as of today (6.5.3).

The whole point of having the set up described in original( HVAC VENT NODE ----- HVAC DUCT ----- AMBIENT NODE), was to simulate pressure loss through an architectural louver. I am interested to learn if I have been using a reasonable approach, or are there recommendations to better simulate louver pressure drop in FDS.

Below is an example of pressure loss chart provided by one of the louver manufacturers:

For intake through this louver, one the K loss factor can be calculated as approx 5.3. What would be the best way to represent these losses in FDS 6.5.3. What I have tried so far is sizing the HVAC VENTto be the same area as louver free area. I have entered the entire loss of 5.3 in the DUCT connecting the HVAC VENT and AMBIENT NODE . I have entered 0 roughness for the DUCT , and 0 LOSS for the AMBIENT NODE and actual VENT.

Are there any concerns or recommendations regarding this approach? 

[Dave McGill]

Hi Sam,

As I recall, 5.3.3 introduced zones and leakage paths. It did not have the complete HVAC solver (vents, nodes, ducts, fans etc) that appeared in (probably) 6.0.

Dave

[dr_jfloyd]

5.5.3 was an early release of the HVAC model. Numerous bugs and issues with the model have been resolved between 5.5.3 and 6.5.3. If your case runs correctly with 6.5.3 and not 5.5.3, then likely this was due to the resolution of one of those issues. 

[dr_jfloyd]

I would make the VENT the actual size of the louver and set the DUCT area to the free area. Your loss specification looks appropriate.