[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
[EnergyPlus_Support] Re: Internal mass
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...
------------------------ 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/