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Cooling minimum air flow fraction ?

asked 2018-09-28 00:17:32 -0500

Siv gravatar image

updated 2018-10-15 19:10:02 -0500

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 ?

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answered 2018-10-04 21:31:29 -0500

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.

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Asked: 2018-09-28 00:17:32 -0500

Seen: 129 times

Last updated: Oct 04