Re: [EnergyPlus_Support] infiltration

["Michael J. Witte" <mjwitte@xxxxxxxx>]

My apologies for the delayed response to this question.  Please see below.

On 16 Jun 2004, at 22:58, teklay weldeabzgi wrote:

> 
>  i am simulating  a two story office building. there is a corridor on both
>  stories. and in my simulation the corridor is not conditioned b/c the doors are
>  assumed to be opened the whole day, hence it is difficult to control the
>  temperature of the corridors. but i think the temperature of the corridors is
>  less than the outside environment due to the infiltration from the conditiond
>  rooms. so how can i consider the outside environent of the walls which are
>  exsposed to the corridors.

You should model the corridor as a separate thermal zone, and the walls between 
the conditioned rooms and the corridor should be interzone heat transfer 
surfaces with OutsideFaceEnvironment=OtherZoneSurface, and 
OutsideFaceEnvironmentObject=corresponding wall in the corridor zone.

> 
> second question i have asked this question last time and mike has replaed to me
> but i couldn't get it. this is i couldn't understand how to estimate the
> constants A, B, C, and D in the infiltration equation. in the input output
> reference it says only they are user specified constants and they are dependent
> in the external environment. so is there any one who can help me how to estimate
> this constants for a given climate. or could send me a note or values of these
> constants for different climates.
> 

The question of typical values for these coefficients is subject to debate.  
Ideally, one should do a detailed analysis of the infiltration situation and 
then determine a custom set of coefficients using methods such as those laid 
out in Chapter 26 of the ASHRAE Handbook of Fundamentals.  The EnergyPlus 
defaults are 1,0,0,0 which gives a constant volume flow of infiltration under 
all  conditions.  The coeffeicients are not climate-dependent, rather they are 
dependent on the types of openings and cracks present in the building.

BLAST (one of the EnergyPlus predecessors) used the following values as 
defaults:  0.606, 0.03636, 0.1177, 0.  These coefficients produce a value of 
1.0 at 0C deltaT and 3.35 m/s (7.5 mph) windspeed, which corresponds to a 
typical summer condition.  At a winter condition of 40C deltaT and 6 m/s (13.4 
mph) windspeed, these coefficients would increase the infiltration rate by a 
factor of 2.75.  

In DOE-2 (the other EnergyPlus predecessor), the air change method defaults are 
(adjusted to SI units) 0, 0, 0.224 (windspeed), 0.  With these coefficients, 
the summer conditions above would give a factor of 0.75, and the winter 
conditions would give 1.34.  A windspeed of 4.47 m/s (10 mph) gives a factor of 
1.0.  

The source of the BLAST defaults is noted in the BLAST documentation as:  

"Empirical equation and the coefficient default were determined from ASHRAE 
journal articles and other data on the effects of outdoor weather conditions."  

The source of the DOE-2 defaults is based on examining the infiltration 
relationships decsribed in the ASHRAE Handbook of Fundamentals.   

The EnergyPlus example files use all of the above, the BLAST defaults in some 
(GeometryTest), the DOE-2 defaults in some (5ZoneAirCooled), and the EnergyPlus 
defaults in some (LgOffVAVDetCoil).  

I hope this helps.

Mike


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



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