Fan curves HVAC model FDS version 6.7.5

[fcurow]

To whom it may concern,

If I specify a fan curve with a ramp (pressure vs vol flow) under the HVAC model using fds version 6.7.5, how do I specify the reference density of the fan curve? Or what is the assumed reference density in the HVAC model?

Best Regards,
Sal

[drjfloyd]

Fans are assumed to maintain the volume flow specified without any correction for density effects.

[fcurow]

Thank you, but I'm modeling a fan curve not a constant volume flow. Typically, when the density of the air going through the fan is different than its reference density, for the same flow the fan pressure will differ. Will the fan pressure be adjusted for the given flow if the inlet temperature, and thus density, of the fan varies? Or will the curve I specified not be adjusted in any way:

&HVAC ID='Fan01', TYPE_ID='FAN', RAMP_ID='Fan01_RAMP_ID'/
&RAMP ID='Fan01_RAMP_ID', T=5.079862, F=1802.323392/
&RAMP ID='Fan01_RAMP_ID', T=5.705036, F=1756.608094/
&RAMP ID='Fan01_RAMP_ID', T=6.449808, F=1713.520341/
&RAMP ID='Fan01_RAMP_ID', T=7.254379, F=1675.1475/
&RAMP ID='Fan01_RAMP_ID', T=8.027541, F=1640.343261/
&RAMP ID='Fan01_RAMP_ID', T=8.824863, F=1604.242291/
&RAMP ID='Fan01_RAMP_ID', T=9.631851, F=1567.311414/
&RAMP ID='Fan01_RAMP_ID', T=10.419509, F=1530.588014/
&RAMP ID='Fan01_RAMP_ID', T=11.306229, F=1489.258628/
&RAMP ID='Fan01_RAMP_ID', T=12.086639, F=1453.40663/
&RAMP ID='Fan01_RAMP_ID', T=12.883962, F=1417.513137/
&RAMP ID='Fan01_RAMP_ID', T=13.719943, F=1384.130114/
&RAMP ID='Fan01_RAMP_ID', T=14.551091, F=1353.610271/
&RAMP ID='Fan01_RAMP_ID', T=15.348414, F=1327.675667/
&RAMP ID='Fan01_RAMP_ID', T=16.155401, F=1302.716203/
&RAMP ID='Fan01_RAMP_ID', T=16.9491, F=1279.048283/
&RAMP ID='Fan01_RAMP_ID', T=17.829779, F=1252.486061/
&RAMP ID='Fan01_RAMP_ID', T=18.634351, F=1226.997531/
&RAMP ID='Fan01_RAMP_ID', T=19.424425, F=1198.894794/
&RAMP ID='Fan01_RAMP_ID', T=20.228996, F=1167.010791/
&RAMP ID='Fan01_RAMP_ID', T=21.019071, F=1130.738652/
&RAMP ID='Fan01_RAMP_ID', T=21.807534, F=1090.114688/
&RAMP ID='Fan01_RAMP_ID', T=22.572642, F=1051.93895/
&RAMP ID='Fan01_RAMP_ID', T=23.321643, F=1008.991244/
&RAMP ID='Fan01_RAMP_ID', T=24.02534, F=969.077887/
&RAMP ID='Fan01_RAMP_ID', T=24.666621, F=932.224814/
&RAMP ID='Fan01_RAMP_ID', T=25.447837, F=891.691385/
&RAMP ID='Fan01_RAMP_ID', T=26.24516, F=855.873338/
&RAMP ID='Fan01_RAMP_ID', T=27.034429, F=825.374243/
&RAMP ID='Fan01_RAMP_ID', T=27.785442, F=801.721883/
&RAMP ID='Fan01_RAMP_ID', T=28.612967, F=783.048968/
&RAMP ID='Fan01_RAMP_ID', T=29.41633, F=772.312042/
&RAMP ID='Fan01_RAMP_ID', T=30.297009, F=769.791198/
&RAMP ID='Fan01_RAMP_ID', T=31.060161, F=772.111975/
&RAMP ID='Fan01_RAMP_ID', T=31.874742, F=779.521862/
&RAMP ID='Fan01_RAMP_ID', T=32.696226, F=789.117666/
&RAMP ID='Fan01_RAMP_ID', T=33.557979, F=798.817208/
&RAMP ID='Fan01_RAMP_ID', T=34.321937, F=804.922955/
&RAMP ID='Fan01_RAMP_ID', T=35.136517, F=807.323758/
&RAMP ID='Fan01_RAMP_ID', T=35.99827, F=805.24899/
&RAMP ID='Fan01_RAMP_ID', T=36.755324, F=799.854592/
&RAMP ID='Fan01_RAMP_ID', T=37.552647, F=790.178627/
&RAMP ID='Fan01_RAMP_ID', T=38.34997, F=777.27734/
&RAMP ID='Fan01_RAMP_ID', T=39.147293, F=761.320485/
&RAMP ID='Fan01_RAMP_ID', T=39.944616, F=743.156831/
&RAMP ID='Fan01_RAMP_ID', T=40.741939, F=721.598101/
&RAMP ID='Fan01_RAMP_ID', T=41.539262, F=695.795527/
&RAMP ID='Fan01_RAMP_ID', T=42.336584, F=666.428124/
&RAMP ID='Fan01_RAMP_ID', T=43.133907, F=634.853921/
&RAMP ID='Fan01_RAMP_ID', T=43.93123, F=603.279719/
&RAMP ID='Fan01_RAMP_ID', T=44.728553, F=571.026502/
&RAMP ID='Fan01_RAMP_ID', T=45.525876, F=538.773284/
&RAMP ID='Fan01_RAMP_ID', T=46.323199, F=505.841051/
&RAMP ID='Fan01_RAMP_ID', T=47.120521, F=471.550789/
&RAMP ID='Fan01_RAMP_ID', T=47.917844, F=436.751265/
&RAMP ID='Fan01_RAMP_ID', T=48.715167, F=400.254203/
&RAMP ID='Fan01_RAMP_ID', T=49.51249, F=362.059603/
&RAMP ID='Fan01_RAMP_ID', T=50.391738, F=321.100917/
&RAMP ID='Fan01_RAMP_ID', T=51.638177, F=256.880734/
&RAMP ID='Fan01_RAMP_ID', T=53.596866, F=165.137615/
&RAMP ID='Fan01_RAMP_ID', T=55.911681, F=55.045872/

[drjfloyd]

If you are using a fan curve the volume flow rate is adjusted based on the pressure the fan is working against as defined in the fan curve. But at a given pressure air at 20 C would have the same volume flow as air at 100 C.

…

On Thu, Jan 9, 2025, 13:01 fcurow ***@***.***> wrote: Thank you, but I'm modeling a fan curve not a constant volume flow. Typically, when the density of the air going through the fan is different than its reference density, for the same flow the fan pressure will differ. Will the fan pressure be adjusted for the given flow if the inlet temperature, and thus density, of the fan varies? Or will the curve I specified not be adjusted in any way: &HVAC ID='Fan01', TYPE_ID='FAN', RAMP_ID='Fan01_RAMP_ID'/ &RAMP ID='Fan01_RAMP_ID', T=5.079862, F=1802.323392/ &RAMP ID='Fan01_RAMP_ID', T=5.705036, F=1756.608094/ &RAMP ID='Fan01_RAMP_ID', T=6.449808, F=1713.520341/ &RAMP ID='Fan01_RAMP_ID', T=7.254379, F=1675.1475/ &RAMP ID='Fan01_RAMP_ID', T=8.027541, F=1640.343261/ &RAMP ID='Fan01_RAMP_ID', T=8.824863, F=1604.242291/ &RAMP ID='Fan01_RAMP_ID', T=9.631851, F=1567.311414/ &RAMP ID='Fan01_RAMP_ID', T=10.419509, F=1530.588014/ &RAMP ID='Fan01_RAMP_ID', T=11.306229, F=1489.258628/ &RAMP ID='Fan01_RAMP_ID', T=12.086639, F=1453.40663/ &RAMP ID='Fan01_RAMP_ID', T=12.883962, F=1417.513137/ &RAMP ID='Fan01_RAMP_ID', T=13.719943, F=1384.130114/ &RAMP ID='Fan01_RAMP_ID', T=14.551091, F=1353.610271/ &RAMP ID='Fan01_RAMP_ID', T=15.348414, F=1327.675667/ &RAMP ID='Fan01_RAMP_ID', T=16.155401, F=1302.716203/ &RAMP ID='Fan01_RAMP_ID', T=16.9491, F=1279.048283/ &RAMP ID='Fan01_RAMP_ID', T=17.829779, F=1252.486061/ &RAMP ID='Fan01_RAMP_ID', T=18.634351, F=1226.997531/ &RAMP ID='Fan01_RAMP_ID', T=19.424425, F=1198.894794/ &RAMP ID='Fan01_RAMP_ID', T=20.228996, F=1167.010791/ &RAMP ID='Fan01_RAMP_ID', T=21.019071, F=1130.738652/ &RAMP ID='Fan01_RAMP_ID', T=21.807534, F=1090.114688/ &RAMP ID='Fan01_RAMP_ID', T=22.572642, F=1051.93895/ &RAMP ID='Fan01_RAMP_ID', T=23.321643, F=1008.991244/ &RAMP ID='Fan01_RAMP_ID', T=24.02534, F=969.077887/ &RAMP ID='Fan01_RAMP_ID', T=24.666621, F=932.224814/ &RAMP ID='Fan01_RAMP_ID', T=25.447837, F=891.691385/ &RAMP ID='Fan01_RAMP_ID', T=26.24516, F=855.873338/ &RAMP ID='Fan01_RAMP_ID', T=27.034429, F=825.374243/ &RAMP ID='Fan01_RAMP_ID', T=27.785442, F=801.721883/ &RAMP ID='Fan01_RAMP_ID', T=28.612967, F=783.048968/ &RAMP ID='Fan01_RAMP_ID', T=29.41633, F=772.312042/ &RAMP ID='Fan01_RAMP_ID', T=30.297009, F=769.791198/ &RAMP ID='Fan01_RAMP_ID', T=31.060161, F=772.111975/ &RAMP ID='Fan01_RAMP_ID', T=31.874742, F=779.521862/ &RAMP ID='Fan01_RAMP_ID', T=32.696226, F=789.117666/ &RAMP ID='Fan01_RAMP_ID', T=33.557979, F=798.817208/ &RAMP ID='Fan01_RAMP_ID', T=34.321937, F=804.922955/ &RAMP ID='Fan01_RAMP_ID', T=35.136517, F=807.323758/ &RAMP ID='Fan01_RAMP_ID', T=35.99827, F=805.24899/ &RAMP ID='Fan01_RAMP_ID', T=36.755324, F=799.854592/ &RAMP ID='Fan01_RAMP_ID', T=37.552647, F=790.178627/ &RAMP ID='Fan01_RAMP_ID', T=38.34997, F=777.27734/ &RAMP ID='Fan01_RAMP_ID', T=39.147293, F=761.320485/ &RAMP ID='Fan01_RAMP_ID', T=39.944616, F=743.156831/ &RAMP ID='Fan01_RAMP_ID', T=40.741939, F=721.598101/ &RAMP ID='Fan01_RAMP_ID', T=41.539262, F=695.795527/ &RAMP ID='Fan01_RAMP_ID', T=42.336584, F=666.428124/ &RAMP ID='Fan01_RAMP_ID', T=43.133907, F=634.853921/ &RAMP ID='Fan01_RAMP_ID', T=43.93123, F=603.279719/ &RAMP ID='Fan01_RAMP_ID', T=44.728553, F=571.026502/ &RAMP ID='Fan01_RAMP_ID', T=45.525876, F=538.773284/ &RAMP ID='Fan01_RAMP_ID', T=46.323199, F=505.841051/ &RAMP ID='Fan01_RAMP_ID', T=47.120521, F=471.550789/ &RAMP ID='Fan01_RAMP_ID', T=47.917844, F=436.751265/ &RAMP ID='Fan01_RAMP_ID', T=48.715167, F=400.254203/ &RAMP ID='Fan01_RAMP_ID', T=49.51249, F=362.059603/ &RAMP ID='Fan01_RAMP_ID', T=50.391738, F=321.100917/ &RAMP ID='Fan01_RAMP_ID', T=51.638177, F=256.880734/ &RAMP ID='Fan01_RAMP_ID', T=53.596866, F=165.137615/ &RAMP ID='Fan01_RAMP_ID', T=55.911681, F=55.045872/ — Reply to this email directly, view it on GitHub <#14023 (reply in thread)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/ADBUZ4NGIZMXXZIDTDK5IXL2J22PLAVCNFSM6AAAAABU4LZK4CVHI2DSMVQWIX3LMV43URDJONRXK43TNFXW4Q3PNVWWK3TUHMYTCNZYHE3DKNY> . You are receiving this because you commented.Message ID: ***@***.***>