Cooling minimum air flow fraction ?

asked 6 years ago

Siv
653 ●1 ●11

updated 6 years ago

__AmirRoth__

4446 ●5 ●17 http://bleedinggreenna...

Will the Sizing:Zone:Cooling Minimum Air Flow Fraction input still be used to set minimum air flow for VAV systems even if my Cooling Design Air Flow Method = DesignDay ?

if yes, what is the ideal value used in the industry ? How to set the minimum air flow fraction value ?

answered 6 years ago

rraustad

13924 ●81 ●13 http://www.fsec.ucf.edu/

The Sizing:Zone, Cooling Minimum Air Flow Fraction input is used in two places as far as I can tell. I doesn't matter which cooling air flow sizing method is used, if this field is entered then it is used here:

DesCoolVolFlowMin = max(DesCoolMinAirFlow,
                                       DesCoolMinAirFlow2,
                                       DesCoolVolFlow * thisTUFZSizing.DesCoolMinAirFlowFrac);

and here:

// set the zone minimum cooling supply air flow rate. This will be used for autosizing VAV terminal unit
// minimum flow rates (comment seems incorrect, really used as a minimum lower limit for the maximum air flow)
FinalZoneSizing(CtrlZoneNum).DesCoolVolFlowMin =
    max(FinalZoneSizing(CtrlZoneNum).DesCoolMinAirFlow,
           FinalZoneSizing(CtrlZoneNum).DesCoolMinAirFlow2,
           FinalZoneSizing(CtrlZoneNum).DesCoolVolFlow * `FinalZoneSizing(CtrlZoneNum).DesCoolMinAirFlowFrac`);

Don't worry too much about what this code does, more importantly that input is used to limit the cooling minimum flow rate during the sizing procedure.