[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: [EnergyPlus_Support] Re: Internal mass
EnergyPlus has been compared to a variety of other simulation tools, including
DOE-2.1E (see http://www.energyplus.gov/testing.html). I have not seen a
comparison with TRACE. The handling of thermal mass is equal to or better than
these other tools. If you are not seeing the results you expect, make sure you
are using MATERIAL:REGULAR and verify the property inputs. Also, as Alexandre
points outs, there are certain configurations in which the thermal mass has
little impact due to placement which prevents it from being active.
Mike
On 27 Sep 2004, at 7:52, alexandrevarela2000 wrote:
> Hi Shaun,
>
> I haven´t had that much experience with DOE2 or Trace, but I´m
> working with people who have worked with DOE2.
>
> Their opinion is that E+ is having better results with internal mass
> than DOE2.
>
> One thing to have in mind when "building" constructions to study the
> effect of internal mass is not to place a "light" material (carpet,
> expanded polystyrene...) as the outermostlayer as this will eliminate
> the internal mass effect. I don´t know if this helps...
>
> My work with internal mass took a small stop, but I will have a look
> at those models again in the near future.
>
> This topic is very important as internal mass is sure to have a big
> impact in building performance.
>
> Looking forward for more "internal mass" news, good work,
> Alexandre
>
> --- In EnergyPlus_Support@xxxxxxxxxxxxxxx, "sm278424"
> <shaunmartin@s...> wrote:
> > I'd like to ask one further question related to this discussion.
> >
> > Has it been found that the heat balance calculations in E+ produce
> > significantly different results from DOE2 and Trace with respect to
> > thermal mass effects?
> >
> > In the model I'm currently working on the thermal 'lag' seems
> almost
> > non-existent.
> >
> > Thanks
> > Shaun Martin
> >
> >
> > --- In EnergyPlus_Support@xxxxxxxxxxxxxxx, "Michael J. Witte"
> > <mjwitte@g...> wrote:
> > > It is difficult to sort out all of the different heat transfer
> > mechanisms in a
> > > particular model. Several issues to explore:
> > >
> > > 1. Have you run a case with no partitions and no internal mass
> to
> > convince
> > > yourself that the mass is having an effect. Your various cases
> as
> > listed in
> > > the original posting are all somewhat similar to each other, they
> > just vary in
> > > the location and amount of internal mass.
> > >
> > > 2. In the file that was posted, if I understand correctly, the
> > partition walls
> > > use the contsruction "PartitionAlex" which uses
> > material "4_1_10001" as the
> > > outside and inside surface layers. This material has a solar
> > absorptance of
> > > 0.25, which is quite low. This will limit how much solar the
> > interior
> > > partitions absorb and limit their impact on the space conditions.
> > >
> > > 3. The ventilation air does not interact directly with the
> > partitions/internal
> > > mass. It only mixes with the zone air, and then the zone air
> > interacts with
> > > the zone surfaces. You may notice that internal mass has only a
> > small effect
> > > on mean air temperature, but a larger effect on mean radiant
> > temperature.
> > >
> > > 4. How high are the ventilation rates? If they are high, then
> > the zone air
> > > temperature will track very closely to the outside drybulb
> > temperature
> > > regardless of how much internal mass is present. You might also
> > try some cases
> > > with zero ventilation and zero HVAC to see that the internal mass
> > does indeed
> > > dampen the temperature swings.
> > >
> > > 5. There are limits to how much thermal mass can be effective in
> > a given
> > > space. The amount of heat transferred into the internal mass is
> > limited by
> > > UAdeltaT for convection and by absorptance*area for radiant and
> > solar. At some
> > > point, more mass makes no difference, because there is not enough
> > heat transfer
> > > at the surface to utilize it.
> > >
> > > 6. The ground temperatures are 16C. This is quite cool and
> > provides a
> > > significant heat sink. Decouple the floor from the ground and
> see
> > if the model
> > > behaves more as you would expect. To develop better ground
> > temperatures, use
> > > the Slab program described in the Auxiliary Programs document.
> > >
> > > 7. Regarding convex zones, the zone must be fully enclosed, and
> > it must not
> > > violate the rule about intercepting more than two surfaces. If
> > these rules are
> > > violated, the alrogithm does not work properly.
> > >
> > > Mike
> > >
> > >
> > >
> > > On 20 Aug 2004, at 8:42, alexandrevarela2000 wrote:
> > >
> > > > Hi Rahul,
> > > >
> > > > Thanks for your interest int his matter. You are mainly right.
> > The
> > > > internal doesn´t "really" afect loads. But internal mass
> > > > should "flatten" indoor air temperature curve. and this is not
> > > > changing that much with increased mass.
> > > >
> > > > Partitions interact with outside environment if you use
> > > > FullInteriorandExterior solar distribution model, since E+
> > calculates
> > > > the radiation incident in these interior walls. In this way
> > > > partitions are affected by outside conditions (sun).
> > > >
> > > > This model has natural ventilation. This is another outside
> > condition
> > > > affecting internal partitions.
> > > >
> > > > I also have a question about convex and non-convex zones. If I
> > inser
> > > > partitions in a convex zone, in a way that they don't divide
> the
> > > > zone, I can still say that the zone is convex. Is this right?
> > The
> > > > thing is that if using the E+ definition of convex ("A formal
> > > > definition of convex is that any straight line passing through
> > the
> > > > zone intercepts at most two surfaces"), the zone is no longer
> > convex.
> > > > I hope I could make myself clear...
> > > >
> > > > Maybe I will just post a generic model in the files folder so
> > > > everybody can check out the geometry and fenestration.
> > > >
> > > > Thanks alot for your help,
> > > > Alexandre
> > > >
> > > > --- In EnergyPlus_Support@xxxxxxxxxxxxxxx, Rahul Chillar
> > > > <chillarrahul@y...> wrote:
> > > > > Hello
> > > > >
> > > > > As you put it, its lot dependent of building physics.Mainly
> > because
> > > > the partitions are not exposed to outside enviornment and its
> > > > temperature fluctuates with the zones temperatures and the
> > > > temperature lag depends on its thermal mass.
> > > > >
> > > > > Also generally the zones being seperated by Internal
> > partitions
> > > > have same temperatures on both the sides of the partitions too.
> > > > >
> > > > > Hence the effect of partition is negligible on the loads,
> > mainly
> > > > the partition is preventing the convective transfer between the
> > zones
> > > > which would have take place had they not been present.
> > > > >
> > > > >
> > > > > Thanks
> > > > > Rahul Chillar
> > > > >
> > > > >
> > > > >
> > > > > alexandrevarela2000 <amv@e...> wrote:
> > > > > Dear all,
> > > > >
> > > > > I´ve simulated a building's internal mass like this:
> > > > >
> > > > > 1)Internal partitions as InternalMass (construction type
> > Plywood)
> > > > > 2)Internal partitions as InternalMass (construction type
> brick
> > wall)
> > > > > 3)Internal partitions modeled as walls (actual surfaces and
> > not
> > > > > internal mass) and using solar distribution FullExterior
> > > > > (construction type brick wall)
> > > > > 3)Internal partitions modeled as walls (actual surfaces and
> > not
> > > > > internal mass) and using solar distribution
> > FullInteriorAndExterior
> > > > > (construction type brick wall)
> > > > >
> > > > > The results regarding these situations didn´t change that
> > much,
> > > > which
> > > > > doesn´t seem right. On the other hand changing mass
> properties
> > for
> > > > > external walls, roofs or floors does have a large impact on
> > results
> > > > > (specially floor mass).
> > > > >
> > > > > Could this be E+ software related, or is this relating only
> to
> > the
> > > > > building's physics?
> > > > >
> > > > > If you think it helps I will upload the base model.
> > > > >
> > > > > Thank you very much,
> > > > > Alexandre
> > > > >
> > > > >
> > > > >
> > > > > 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 SponsorADVERTISEMENT
> > > > >
> > > > >
> > > > > ---------------------------------
> > > > > 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 the Yahoo! Terms
> of
> > > > Service.
> > > > >
> > > > >
> > > > >
> > > > > Thanks
> > > > > Rahul Chillar
> > > > > Grad Student
> > > > > Building Systems lab
> > > > > Univ Of Illinois Urbana Champaign
> > > > >
> > > > >
> > > > > ---------------------------------
> > > > > Do you Yahoo!?
> > > > > Yahoo! Mail - 50x more storage than other providers!
> > > > >
> > > > > [Non-text portions of this message have been removed]
> > > >
> > > >
> > > >
> > > >
> > > > 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
>
>
>
>
>
>
========================================================
Michael J. Witte, GARD Analytics, Inc.
EnergyPlus Testing and Support
EnergyPlus-Support@xxxxxxxx
------------------------ Yahoo! Groups Sponsor --------------------~-->
Make a clean sweep of pop-up ads. Yahoo! Companion Toolbar.
Now with Pop-Up Blocker. Get it for free!
http://us.click.yahoo.com/L5YrjA/eSIIAA/yQLSAA/dkFolB/TM
--------------------------------------------------------------------~->
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
<*> 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/