[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: [EnergyPlus_Support] Heat Recovery Problem





Hi Richard,
Thanks for your clarification. I can now interpret the meaning of this warning. I realized that this warnings is related with minimum outdoor air flow rate at Controller:OutdoorAir.
It should also be noted that there should be a compatibility between availability schedule of HX (which defines on/off based on 1/0 only and which is not modulating HX nominal supply flow rate) and minimum outdoor air schedule of Controller:OutdoorAir (which is a fractional schedule and values are multiplied by minimum outdoor air flow rates).
Therefore, any value below 1 for HX schedule means off (no operation) but any value for controller schedule means (say 0.75) is multiplied by min. outdoor air flow rate. At this point outdoor air flow rate can become 50% smaller than nominal supply flow rate of HX.
I already adjusted these two schedules to work together and all the warnings are cleared.
Only side effect of this manipulation is minimum outdoor flow rates will not be adjusted according to the number of people in a thermal zone.
Thanks.

Omer T. Karaguzel
Center for Building Performance & Diagnostics (CBPD)
Carnegie Mellon University 5000 Forbes Ave. Pittsburgh, 15213 PA



--- On Tue, 6/22/10, Richard Raustad <RRaustad@xxxxxxxxxxxx> wrote:

From: Richard Raustad <RRaustad@xxxxxxxxxxxx>
Subject: Re: [EnergyPlus_Support] Heat Recovery Problem
To: EnergyPlus_Support@xxxxxxxxxxxxxxx
Date: Tuesday, June 22, 2010, 3:51 PM

The message is telling you that the flow rate through the HX has fallen
to 49.4% of the nominal flow rate (see documentation for this HX). The
is below the threshold where the simulation can accurately predict HX
performance. Have you tried increasing the minimum OA flow rate
(Controller:OutdoorAir)?

O. Tugrul Karaguzel wrote:
>
> Hi all,
> I'm repeatedly having the following warning for my Energy Plus model
> in which i tried to simulate a heat recovery system (using
> HeatExchanger:AirToAir:SensibleAndLatent).
>
> ** Warning ** HeatExchanger:AirToAir:SensibleAndLatent "OA HEAT
> RECOVERY 3"
> ** ~~~ ** Average air volume flow rate is <50% or >130% of the nominal
> HX supply air volume flow rate.
> ** ~~~ ** Air volume flow rate ratio = 0.494. Occurrence info=
> HEADMASTER'S RESIDENCE, 01/01 08:00 - 08:15
>
> Does anyone have experience with such a warning? I tried to overcome
> it by changing input parameters in objects of Controller:OutdoorAir or
> Fan:VariableVolume or Sizing:System but unfortunately I cannot manage
> to solve it.
> Many Thanks.
>
> Omer T. Karaguzel
> Center for Building Performance & Diagnostics
> Carnegie Mellon University
> 5000 Forbes Ave. Pittsburgh, 15213 PA
>
>
>
>

--
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



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

Primary EnergyPlus support is found at:
http://energyplus.helpserve.com or send a message to energyplus-support@xxxxxxxx

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 currently allowed but be mindful that not everyone has a high speed connection.  Limit attachments to small files.

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:
    EnergyPlus_Support-digest@xxxxxxxxxxxxxxx
    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/




__._,_.___


Primary EnergyPlus support is found at:
http://energyplus.helpserve.com or send a message to energyplus-support@xxxxxxxx

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 currently allowed but be mindful that not everyone has a high speed connection.  Limit attachments to small files.

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




Your email settings: Individual Email|Traditional
Change settings via the Web (Yahoo! ID required)
Change settings via email: Switch delivery to Daily Digest | Switch to Fully Featured
Visit Your Group | Yahoo! Groups Terms of Use | Unsubscribe

__,_._,___