[EnergyPlus_Support] Re: Purchased Air vs. PTAC

["anarui.oliveira" <anarui.oliveira@xxxxxxxxx>]

Indeed.
In the zone node the difference is not very noticeable, but it is in 
the supply air nodes, as you suggested.
Thanks.

--- In EnergyPlus_Support@xxxxxxxxxxxxxxx, Richard Raustad 
<RRaustad@...> wrote:
>
> If the zone temperature is held at the same temperature in both 
cases, 
> compare the zone humidity levels. You will probably find that the 
DX 
> Coil maintains a lower zone humidity level which would probably 
account 
> for the difference in cooling energy..You could also compare the 
> humidity ratio of the supply air for each system. Does the DX Coil 
> provide a lower humidity ratio? You could also report the supply 
air 
> mass flow rate and enthalpy and calculate the delivered cooling 
energy 
> as a check.
> 
> anarui.oliveira wrote:
> >
> > Hello all.
> >
> > If (for cooling only), maintaining all other parameters in a 
model:
> >
> > - a PTAC is fully set to autosize, and a simulation is run,
> > - and then it is substituted by a simple Purchased Air 
configuration,
> > for the exact same zone and thermostat,
> >
> > why is the "DX Coil Total Cooling Energy" between 1.5 to 4 times 
higher
> > than the "Purchased Air Total Cooling Energy"?
> >
> > I know "Purchased Air" is a simplification, but since we're 
looking
> > directly at the thermal loads, and not any efficiency-dependent
> > consumption variable, where does this difference come from?
> >
> > Regards,
> > Ana Rui.
> >
> >  
> 
> -- 
> 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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