Re: [EnergyPlus_Support] Re: Thermal mass effect

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

The radiant ceiling panels certainly complicates matters, because it causes the 
surfaces temperatures in the entire zone to be cooler than they would be using 
an air-only HVAC system.  You mentioned comparing total cooling load.  Have you 
looked at peak cooling loads?  If there is no night venting, then I would 
expect thermal mass to have a small impact on total cooling load, but it should 
have a significant impact on peak cooling load, essentially flattening out the 
swings in cooling load.

Mike


On 6 Apr 2005, at 21:57, sm278424 wrote:

> 
> 
> Hi Mike,
> 
> We've discussed this building before. It has a CV supply air system + 
> plenum and radiant ceiling panels. 
> 
> Answers
> 1. I tried defining all of my constructions as Regular-R to eliminate 
> the mass. This increased the total cooling load by just under 5%.
> 
> 2. I'm using a combination: furniture and internal partitions are 
> internal mass, floors and ceilings are surface objects. Taking out 
> the internal mass increased the total cooling load by just about 1%.
> 
> 3. ORNL and Berkley Solar Group have done some interesting work here 
> on external walls.  The location of the concrete (mass) and the 
> magnitude of the daily temperature swings are the important factors. 
> 
> On internal surfaces, I found is that the interaction between the 
> radiant ceiling panel and the concrete floor is something to pay 
> attention to. Conceivably you could night-cool the building with this 
> type of system.
> 
> 4. Mostly by tracking the surface tempertures.
> 
> Shaun
> 
> 
> --- In EnergyPlus_Support@xxxxxxxxxxxxxxx, "Michael J. Witte" 
> <mjwitte@g...> wrote:
> > I don't have a good reference to offer, but I have some questions 
> to ask:
> > 
> > 1.  The obvious question - are you using Material:Regular so that 
> there is 
> > actually mass present in the building?
> > 
> > 2.  Have interior surfaces been described using internal mass or 
> surface 
> > objects?
> > 
> > 3.  In a "fully conditioned" building, mass effects tend to be 
> small, because 
> > most of the mass is not changing temperature very much except 
> during 
> > transitions to/from thermostat setback.  This is especially true if 
> the 
> > building has a fairly large footprint and a large core to perimeter 
> ratio.
> > 
> > 4.  How are you quantifying the "thermal mass effect"?
> > 
> > Mike
> > 
> > 
> > On 1 Apr 2005, at 17:47, sm278424 wrote:
> > 
> > > 
> > > 
> > > In models I've been working with recently (of a fully air 
> conditioned 
> > > office building), the thermal mass effect seems quite small.  
> > > 
> > > Can anyone suggest a good reference on this topic? 
> > > 
> > > Thanks
> > > Shaun
> > > 
> > > 
> > > 
> > > 
> > > 
> > > 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.
> > > 
> > > Yahoo! Groups Links
> > > 
> > > 
> > > 
> > > 
> > > 
> > > 
> > > 
> > > 
> > > 
> > 
> > 
> > 
> > ========================================================
> > Michael J. Witte, GARD Analytics, Inc.
> > EnergyPlus Testing and Support      
> > EnergyPlus-Support@g...
> 
> 
> 
> 
> 
> 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.
> 
> Yahoo! Groups Links
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> 
> 
> 
> 
> 
> 
> 
> 



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




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