[EnergyPlus_Support] Re: Thermal mass effect

["sm278424" <shaunmartin@xxxxxxx>]

Sorry, by total cooling load I was actually refering to the peak.

Actually, I'm not sure it does do much to the peak.  I'm getting 
more comfortable with my 5% figure.  

The basic problem is the solar gain spikes that occur at lower solar 
altitudes (where it's difficult to provide external shading). It's 
the spikes that send the thermal comfort index out of control.  By 
its nature thermal mass is slow release, so it flattens the day but 
does little for the spikes. 

It's an interesting issue. I wish I had more time to spend on it.



--- In EnergyPlus_Support@xxxxxxxxxxxxxxx, "Michael J. Witte" 
<mjwitte@g...> wrote:
> 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
> > 
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> > http://groups.yahoo.com/group/EnergyPlus_Support/
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> > Attachments are not allowed -- please post any files to the 
appropriate folder
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> > 
> > 
> > 
> > 
> > 
> > 
> > 
> > 
> 
> 
> 
> ========================================================
> Michael J. Witte, GARD Analytics, Inc.
> EnergyPlus Testing and Support      
> EnergyPlus-Support@g...





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