Re: [EnergyPlus_Support] Ground Temperature [Slab.exe]

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

On 12 Dec 2003, at 16:15, waspoorboy wrote:

> The new Ground Temperature package has "included monthly inside 
> temperatures (TIN), and a daily range."[ref. new E+SlabGHT.idd]
> 
> #1:The Ground Temp section of AuxiliaryPrograms.pdf has not reflected
> the change.

What is missing?  In the AuxiliaryPrograms.pdf for version 1.1.1, I see 
descriptions of these inputs on p. 49 (pdf p. 57).   

> 
> #2:It is said that Weather File ground temp may not be suitable of 
> being used directly [I/O ref], because the heat transfer between 
> building slab and the ground may already changed the soil temp around 
> the slab.
> 
> Q:If now the building is left un-airconditioned, i.e., no HVAC,
> would Weather File ground temp be suitable then ?

The weather file values are for undisturbed ground temperatures.   
Anything that is put over the ground disturbs the temperature profile.   
It is a very long transient that may take several years, but it  
changes.  Ground temperatures under buildings change greatly from  
undisturbed values.

Such a building will still have an effect.  It shades the ground and  
its inside temperature is usually not the ambient air temperature.The  
Weather File ground temp is not suitable.

The ground temperature program does not simulate a floating inside  
temperature, so a determination of the ground temperature requires  
multiple steps.  First simulate the unheated building in EnergyPlus  
with an insulated floor.  Then use the monthly average indoor  
temperatures as monthly indoor setpoints for the ground temperature  
calculation.  Use the resulting monthly ground temperatures with the  
EnergyPlus building simulation to determine the effect of the ground  
temperature.  This procedure could be repeated if the indoor  
temperatures resulting from the second EnergyPlus run are significantly  
different from those calculated with the insulated floor.  Usually they  
are not.


> 
> #3:"lower boundary at a fixed temperature"
> Should this field be always TRUE ? 
> If not, when should it be FALSE ?
> How does it affect the calculation and the results ?
> 
> BoundConds,
> TRUE, !- EVTR: Is surface evapotranspiration modeled
> TRUE, !- FIXBC: is the lower boundary at a fixed temperature
> FALSE;!- OLDTG: is there an old ground temperature file

With the lower boundary at a 10 m depth, there is a very small  
difference between the fixed temperature boundary condition and the  
zero flux boundary condition.  Just use the fixed temperature boundary  
condition.

> 
> Thanks,
> Ming
> 
> 
> 
> To unsubscribe from this group, send an email to:
> EnergyPlus_Support-unsubscribe@xxxxxxxxxxxxxxx
> 
> 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 are of the Support Web Site.
> 
> 
> 
> 
> 
> 
> Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/ 
> 


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

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 are of the Support Web Site.




 

Yahoo! Groups Links

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

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/