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[EnergyPlus_Support] Re: AHU with plate heat exchanger and no mixing box, possible?

Dear James,

Many thanks, my is VAV system... now I'll see what I can do.

Best regards,

Andrea


--- In EnergyPlus_Support@xxxxxxxxxxxxxxx, "James V Dirkes II, PE" <jim@...> wrote:
>
> Dear Andrea,
> 
> The HX object is convinced that flows should never fall outside the 50-130%
> range. (I'm hoping that E+ improves this limitation in a future release,
> since it has caused me problems, too!) This calculation is based on the Air
> Loop flow at the HX.  If you are using a constant volume system, this should
> be easy to fix; one or more of your flows do not agree / coincide.
> 
>  
> 
> If you have a VAV system or are using an economizer with variable outdoor
> air flow across the HX, you're not going to avoid these errors.  I don't
> think the errors cause serious inaccuracies in the model, however, but I
> have not checked it in detail.
> 
>  
> 
> You may be able to add a zone HX which accomplishes the equivalent
> thermodynamic process, depending on the actual system you are attempting to
> model.
> 
>  
> 
> The Building Performance Team
> James V. Dirkes II, P.E., LEED AP, BEMP
> 1631 Acacia Drive NW
> Grand Rapids, MI 49504
> 616 450 8653
> 
>  
> 
> From: EnergyPlus_Support@xxxxxxxxxxxxxxx
> [mailto:EnergyPlus_Support@xxxxxxxxxxxxxxx] On Behalf Of
> andreacostaenergyplus
> Sent: Friday, April 22, 2011 4:09 AM
> To: EnergyPlus_Support@xxxxxxxxxxxxxxx
> Subject: [EnergyPlus_Support] Re: AHU with plate heat exchanger and no
> mixing box, possible?
> 
>  
> 
>   
> 
> Dear James,
> 
> Thanks for you repaly.
> The problem is that I need the contrary: 100% fresh air system, for this
> reason I tried to impose the fresh air fraction =1 but then I get the
> following:
> 
> ** Warning ** HeatExchanger:AirToAir:SensibleAndLatent "OA HEAT RECOVERY
> > 1": Average air volume flow rate is <50% or >130% warning continues. Air
> > flow rate ratio statistics follow.
> > > 
> > > ** Warning ** HeatExchanger:AirToAir:SensibleAndLatent "OA HEAT RECOVERY
> > 1": Unbalanced air volume flow ratio exceeds 2:1 warning continues. HX
> flow
> > ratio statistics follow.
> 
> Thanks in advance for any further help,
> 
> Andrea
> 
> --- In EnergyPlus_Support@xxxxxxxxxxxxxxx
> <mailto:EnergyPlus_Support%40yahoogroups.com> , "James V Dirkes II, PE"
> <jim@> wrote:
> >
> > Dear Andrea,
> > 
> > 
> > 
> > How about adding an outdoor air controller and mixing box, but set outdoor
> > air for zero at all times. ("Maximum outdoor air flow rate" = 0)
> > 
> > 
> > 
> > The Building Performance Team
> > James V. Dirkes II, P.E., LEED AP, BEMP
> > 1631 Acacia Drive NW
> > Grand Rapids, MI 49504
> > 616 450 8653
> > 
> > 
> > 
> > From: EnergyPlus_Support@xxxxxxxxxxxxxxx
> <mailto:EnergyPlus_Support%40yahoogroups.com> 
> > [mailto:EnergyPlus_Support@xxxxxxxxxxxxxxx
> <mailto:EnergyPlus_Support%40yahoogroups.com> ] On Behalf Of
> > andreacostaenergyplus
> > Sent: Thursday, April 21, 2011 9:35 AM
> > To: EnergyPlus_Support@xxxxxxxxxxxxxxx
> <mailto:EnergyPlus_Support%40yahoogroups.com> 
> > Subject: [EnergyPlus_Support] Re: AHU with plate heat exchanger and no
> > mixing box, possible?
> > 
> > 
> > 
> > 
> > 
> > Hi all,
> > 
> > Would anybody be able to give be an help on the issue below?
> > 
> > Many thanks in advance,
> > 
> > Andrea
> > 
> > --- In EnergyPlus_Support@xxxxxxxxxxxxxxx
> <mailto:EnergyPlus_Support%40yahoogroups.com> 
> > <mailto:EnergyPlus_Support%40yahoogroups.com> , "andreacostaenergyplus"
> > <andreacostaenergyplus@> wrote:
> > >
> > > Dear All,
> > > 
> > > I am modelling an AHU with a plate heat exchanger an no mixing box.
> > > It seems that this is not possible in E+ and that I must have an
> > OutdoorAir:Mixer object in the AirLoopHVAC:OutdoorAirSystem:EquipmentList.
> > > Can anybody confirm this limitation?
> > > This is the error that I get:
> > > 
> > > ** Severe ** OutdoorAir:Mixer for AirLoopHVAC:OutdoorAirSystem
> > AHU1_OUTDOOR_AIR_SYSTEM not found.
> > > ** Fatal ** GetAirPathData: Errors found getting AirLoopHVAC
> > > 
> > > 
> > > 
> > > I tried a workaround, having the OutdoorAir:Mixer and imposing a Minimum
> > Fraction of Outdoor Air Schedule constanly equal to 1.
> > > But this lead to the follwoing warnings:
> > > 
> > > ** Warning ** HeatExchanger:AirToAir:SensibleAndLatent "OA HEAT RECOVERY
> > 1": Average air volume flow rate is <50% or >130% warning continues. Air
> > flow rate ratio statistics follow.
> > > 
> > > ** Warning ** HeatExchanger:AirToAir:SensibleAndLatent "OA HEAT RECOVERY
> > 1": Unbalanced air volume flow ratio exceeds 2:1 warning continues. HX
> flow
> > ratio statistics follow.
> > > 
> > > Is there any better solution to this issue?
> > > I would kindly appreciate anyone's help on this.
> > > Kind regards,
> > > Andrea
> > >
> >
>




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