[TRNSYS-users] Type 56 Zone Air Capacitance

[David BRADLEY]

Devin,
  The default value of the zone capacitance is 1.007*1.2*ZoneVolume. It 
accounts only for the capacitance of the air in the zone and does not 
account for any furnishings or zone contents. I typically modify the 
capacitance to be about 5 times the default value (up to 10 times for 
zones that have a LOT of stuff in them like a library, a warehouse, or 
(unfortunately) my basement). Whether you leave the default value or 
whether you increase it, there is still thermal lag from the concrete 
but that lag is heavily influenced by the heat transfer coefficient 
between the zone air and the concrete wall.
Best,
  David


On 6/26/2011 10:32, Devin Rohan wrote:
> I have a single zone office with a concrete slab and non-massive 
> walls.  I only seem to get good agreement between TRNSYS and a 1D 
> finite difference model I built when I increase the Zone Air 
> capacitance into the thousands (4000-6000 kJ/K).  Other wise, TRNSYS's 
> air temperature varies wildly and unrealistically with the ambient 
> temperature and there's no thermal lag from the concrete.  Is this 
> high of value for the zone air capacitance ok?
>
> -- 
> Devin M. Rohan, LEED Green Associate
> Purdue University
> Civil/Architectural Engineering
> drohan at purdue.edu <mailto:drohan at purdue.edu>
>
>
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> TRNSYS-users mailing list
> TRNSYS-users at cae.wisc.edu
> https://mailman.cae.wisc.edu/listinfo/trnsys-users

-- 
***************************
David BRADLEY
Principal
Thermal Energy Systems Specialists, LLC
22 North Carroll Street - suite 370
Madison, WI  53703 USA

P:+1.608.274.2577
F:+1.608.278.1475
d.bradley at tess-inc.com

http://www.tess-inc.com
http://www.trnsys.com

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