The HX does not turn off, the average flow rate is used in the calculations, you just don't know if the calculations are correct when the air flow rate ratio is that far off.
On 11/1/2011 4:21 PM, Jean marais wrote:
So what happens currently when the bounds are exceeded? Does the wheel turn off? I could live with that.
--- In EnergyPlus_Support@xxxxxxxxxxxxxxx, Richard Raustad <RRaustad@...> wrote:
>
> This issue has come up many times in the past. The manufacturer cannot
> guaranteethe ratings of the HX when the flow rate ratio is <50% or >130%
> of design. It's as simple as that. And there was no guidance of what to
> do inside the model when the air flow ratio was out of bounds since even
> the manufacturer could not tell us. If you want to use this HX model,
> keep the air flow ratio within the boundaries of where the model is
> valid. Otherwise, change to a flat plate HX (no latent heat transfer).
>
> On 11/1/2011 4:04 PM, Jean marais wrote:
> >
> > Had exactly the same issue doing exactly the same thing for the summer
> > case. I don't know any way to suppress warnings. Obviously, the amount
> > of heat exchange at the enthalpy wheel reduces to very small amounts
> > when the flow from exhaust is <50% the supply side. It seemed as if
> > the wheel stopped working, when I watched the outputs, but I actually
> > have no idea how the object is programmed to react in these
> > conditions. PS in the project I was simulating, an evapourative cooler
> > was cooling the exhaust air (but making very moist) before the
> > heatwheel to increase (take advantage) the sensible heat transfer
> > (which is at about 70%, while the latent eff is only 30% therefore not
> > missing much by "humidifying" the air).
> >
> > --- In EnergyPlus_Support@xxxxxxxxxxxxxxx
> > <mailto:EnergyPlus_Support%40yahoogroups.com>, Jason Kirkpatrick
> > <jason.alan.kirkpatrick@> wrote:
> > >
> > > All,
> > >
> > > I have a model including demand controlled ventilation and an enthalpy
> > > wheel treating the ventilation before the AHU. This all works ok,
> > but since
> > > the ventilation is varying with the occupancy, the enthalpy wheel
> > gives an
> > > error that the ventilation flowrate is too far from the design flowrate:
> > >
> > > ************* ** Warning ** HeatExchanger:AirToAir:SensibleAndLatent
> > > "F1:AHU HEAT RECOVERY": Average air volume flow rate is <50% or >130%
> > > warning continues. Air flow rate ratio statistics follow.
> > >
> > > I am wondering if there is a way that anyone knows of circumventing this
> > > warning or at least suppressing it.
> > >
> > > Thanks,
> > >
> > > Jason
> > >
> >
> >
>
> --
> Richard A. Raustad
> Senior Research Engineer
> Florida Solar Energy Center
> University of Central Florida
> 1679 Clearlake Road
> Cocoa, FL 32922-5703
> Phone: (321) 638-1454
> Fax: (321) 638-1439 or 1010
> Visit our web site at: http://www.fsec.ucf.edu
>
> UCF - From Promise to Prominence: Celebrating 40 Years
>
-- Richard A. Raustad Senior Research Engineer Florida Solar Energy Center University of Central Florida 1679 Clearlake Road Cocoa, FL 32922-5703 Phone: (321) 638-1454 Fax: (321) 638-1439 or 1010 Visit our web site at: http://www.fsec.ucf.edu UCF - From Promise to Prominence: Celebrating 40 Years
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