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Re: [EnergyPlus_Support] Energy stored in zone air





"Michael J. Witte" <mjwitte@xxxxxxxx> escreveu:          1. Yes, the thermal mass of the zone air is included in the zone heat balance.

2. You must compute the convective heat transfer from the zone surfaces by 
reporting Surface Inside Temperature, Surface Int Convection Coeff, and Zone 
Mean Air Temperature. The gain for each surface is Area*ConvCoeff*(Tsurf-
Tair).

Mike

On 16 Sep 2006 at 10:29, Clarice Bleil de Souza wrote:

> Hi everybody,
> 
> I am trying to understand how Eplus deals with the air heat balance
> equation. I had a look at the Engineering reference and got confused by the
> explanation in the following sections: 
> - Basis for the zone and system integration 
> - Summary of predictor corrector procedure
> 
> The air heat balance is described in detail there but what I am not sure is
> if the energy stored in the zone air is taken into account or not in the Eplus
> heat balance equation. Explaining it better... 
> 
> From equation 12 in page 8 of the manual it is said that:
> 
> Load in the system = (sum of the convective internal loads) + (convective
> heat transfer from the zone surfaces) + (heat transfer due to infiltration of
> the outside air) + (heat tranfer due to interzone air mixing)
> 
> This equation differs from the equation 2 page 5 because it does not include
> the energy stored in the zone air.
> 
> I want to plot the components of the air heat balance and assuming I have no
> heat tranfer due to interzone air mixing (I am not using any type of air flow
> model, just simple ventilation and infiltration objects) I can get as Eplus
> outputs all the other components except for the "convective heat transfer from
> the zone surfaces". If the air heat balance include the energy stored in the
> zone air I cannot calculate the convective heat tranfer from the zone surfaces
> from the above equation directly and in this case would like to know how could
> I get it. 
> 
> I tried to build up a simple model - only a box - so that I could sum the
> convective heat tranfer from each surface individually and check if the result
> would match the calculated value from the air heat balance equation. If they
> did then I'd know that the energy stored in the zone air was not be taken into
> account and could be ignored, but I could not do it because EPlus does not
> output the convective heat transfer for each surface only the convective heat
> tranfer coefficients. 
> 
> After that I got even more puzzled and clueless about how could I get this
> portion of the air heat balance and decided to ask you guys on the list.
> Can anybody give me a tip about how could I get this convective heat tranfer
> from surfaces or let me know if the energy stored in the zone air can be
> neglected or not in the process?
> 
> Thank you very much in advance for the help.
> 
> Best regards,
> 
> Clarice
> 
> 
> 
> ---------------------------------
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> 
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> 
> 
> 
> 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.idf and press the
> "search" button.
> 
> Yahoo! Groups Links
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 

========================================================
Michael J. Witte, GARD Analytics, Inc.
EnergyPlus Testing and Support 
EnergyPlus-Support@xxxxxxxx



         

 		
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