Re: [EnergyPlus_Support] Purchased Air variables

[Richard Raustad <RRaustad@xxxxxxxxxxxx>]

1) - the maximum reported heating/cooling rate increases
  The load met by purchased air should not change IF the zone conditions 
have not changed. Mass flow rate should increase. Check the zone conditions.
  PAOutput = M*Cp*dT
2) - Why, for instance, when cooling, the cooling rate/energy increases 
greatly when lowering the supply humidity ratio in Purchased Air 
definitions?
  Since you specified a lower humidity ratio, the dH from zone supply 
inlet to zone is greater. Q=M*Cp*dH. Mass flow rate should be the same.
3) - what should be the approach to choosing the supply temperature and 
humidity ratio to be set in Purchased Air objects?
  Choose the SA temp/humrat inputs to closely resemble the supply air 
conditions of the "real" system you expect to use to replace PA.

anarui.oliveira wrote:
>
> Hello.
> I've been doing some experimenting with Purchased Air and I'd
> appreciate some help to better understand why:
>
> - the maximum reported heating/cooling rate increases as I set the
> supply air temperatures in Purchased Air to be closer to the zone
> setpoint temperatures?
>
> - Why, for instance, when cooling, the cooling rate/energy increases
> greatly when lowering the supply humidity ratio in Purchased Air
> definitions? Does PA actually accounts for the energy necessary to
> force the supply airflow below dew point and then back to the
> defined supply temperature again? I was under the ideia that PA was
> much simpler than that?... In the affirmative case, which are the
> departure conditions that PA considers to calculate those extra
> energy consumptions due to HR adjustments?
>
> Considering that I'm using PA for a first approach of thermal load
> estimates and equipment sizing, what should should be the approach
> to choosing the supply temperature and humidity ratio to be set in
> Purchased Air objects (especially HR greatly influences results)?
>
> Regards,
> Ana Rui Oliveira.
>
>  

-- 
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


------------------------------------

The primary EnergyPlus web site is found at:
http://www.energyplus.gov

The group web site is:
http://groups.yahoo.com/group/EnergyPlus_Support/

Attachments are not allowed -- please post any files to the appropriate folder in the Files area of the Support Web Site.

EnergyPlus Documentation is searchable.  Open EPlusMainMenu.pdf under the Documentation link and press the "search" button.
Yahoo! Groups Links

<*> To visit your group on the web, go to:
    http://groups.yahoo.com/group/EnergyPlus_Support/

<*> Your email settings:
    Individual Email | Traditional

<*> To change settings online go to:
    http://groups.yahoo.com/group/EnergyPlus_Support/join
    (Yahoo! ID required)

<*> To change settings via email:
    mailto:EnergyPlus_Support-digest@xxxxxxxxxxxxxxx 
    mailto:EnergyPlus_Support-fullfeatured@xxxxxxxxxxxxxxx

<*> To unsubscribe from this group, send an email to:
    EnergyPlus_Support-unsubscribe@xxxxxxxxxxxxxxx

<*> Your use of Yahoo! Groups is subject to:
    http://docs.yahoo.com/info/terms/