[Equest-users] Thermal mass effects --- of stuff (UNCLASSIFIED)

Thu Jun 18 14:44:24 PDT 2015

Julien,

I don't mind at all being quoted or cited, but since I don't read everything that's 
posted, just the ones that intrigue me, you might want to cc me via e-mail to get my 
attention.  It's true that I had said in an earlier post that I've found DOE-2 models to 
be "lighter" than measurements, it was not just by a bit, but by a lot.  I didn't do any 
serious investigation into the discrepancy, but I attributed it to the models assuming 
uniform air conditions within a space, surface air film coefficients based on smooth 
planar surfaces, and uniform distribution of the internal thermal mass within the space. 
As scientists or engineers, there's a preference for "getting the inputs right", i.e., 
having the furniture-fraction correspond to the actual amount of furniture in the space, 
but it may be that either the algorithm or the inputs need to be tweaked in order to get a 
indoor air temperatures closer to what's actually observed.

Joe

Joe Huang
White Box Technologies, Inc.
346 Rheem Blvd., Suite 205A
Moraga CA 94556
yjhuang at whiteboxtechnologies.com
http://weather.whiteboxtechnologies.com for simulation-ready weather data
(o) (925)388-0265
(c) (510)928-2683
"building energy simulations at your fingertips"

On 6/18/2015 1:04 AM, Julien Marrec wrote:
> Jeff,
>
> In E+ there's also an "InternalMass" objec. It is listed under the group "Thermal Zones 
> and Surfaces". It only asks for a construction, a zone name, and its surface (m² / ft²): 
> might be easier.
>
> From the I/O reference:
> /*Internal Mass*
> is used to specify the construction/material parameters and area of items within the 
> space that are important to heat transfer calculations but not necessarily important 
> geometrically. (For example, furniture within the space – particularly for large spaces)./
>
> John,
>
> Both e+ and equest can have internal mass objects, that you can add/or customize.
>
> E+ having no defaults on the subject, it won't take any internal mass into account 
> unless you tell it to.
>
> eQuest has by default some internal mass: Floor-weight and Furniture. For Furniture - 
> default is FURN-WEIGHT = 2 lb/ft² of floor area - compare that to what you think you 
> have in your garage and you'll see the difference :))
>
> I think an even bigger problem is to use external walls (especially in equest where it's 
> so easy...) defined only by R-value as opposed to layer-by-layer, thus with no thermal 
> mass...
>
> I'm pretty sure as a general rule we tend to underestimate the overall thermal mass.
> On the subject, I remembered Joe Huang (Joe, I hope you don't mind me quoting you) 
> making a comment about DOE2 making "lighter" models than real anyway so you have to 
> "boost up the internal mass considerably beyond what's there to get  the floating 
> temperature profiles to match measured temperatures" (see his post here 
> <http://lists.onebuilding.org/htdig.cgi/bldg-sim-onebuilding.org/2015-January/046078.html>)
>
> Best,
> Julien
>
>
> > Le 17 juin 2015 à 20:20, "Eurek, John S NWO" <John.S.Eurek at usace.army.mil 
> <mailto:John.S.Eurek at usace.army.mil>> a écrit :
> >
> > Classification: UNCLASSIFIED
> > Caveats: NONE
> >
> > General question:
> >
> > Do any energy models take into account the thermal mass of stuff?
> >
> > Then extreme case I know about is a garage.  When my garage was empty and I turned on 
> the heater it heated up fairly quickly.  When I brought in my truck, tools, shelves, 
> etc. (a few tons of steel) it took a lot lot longer to get warm.
> >
> > This is an extreme case, but the same thing would happen in every type of building on 
> some level.
> >
> > -----Original Message-----
> > From: Equest-users [mailto:equest-users-bounces at lists.onebuilding.org 
> <mailto:equest-users-bounces at lists.onebuilding.org>] On Behalf Of Jeff Haberl
> > Sent: Wednesday, June 17, 2015 10:39 AM
> > To: Peter Schonherr; equest-users at lists.onebuilding.org 
> <mailto:equest-users at lists.onebuilding.org>
> > Subject: [EXTERNAL] Re: [Equest-users] Thermal mass effects of interior walls
> >
> > Hello Peter,
> >
> >
> >
> > Create layered walls with the materials you intend to simulate and then set the floor 
> weight = 0 to trigger custom weighting factors. You may have to fiddle with the interior 
> convection/radiation coefficient to get a meaningful “connection” to the room air node.
> >
> >
> >
> > Jeff
> >
> >
> >
> > 8=!  8=)  :=)  8=)  ;=)  8=)  8=(  8=)  8=()  8=)  8=|  8=)  :=')  8=) 8=?
> > Jeff S. Haberl, Ph.D.,P.E.inactive,FASHRAE,FIBPSA,......jhaberl at tamu.edu 
> <mailto:jhaberl at tamu.edu> <mailto:........jhaberl at tamu.edu <mailto:jhaberl at tamu.edu>>
> > 
> Professor........................................................................Office 
> Ph: 979-845-6507
> > Department of Architecture............................................Lab Ph:979-845-6065
> > Energy Systems Laboratory...........................................FAX: 979-862-2457
> > Texas A&M University...................................................77843-3581
> > College Station, Texas, USA, 77843..............................URL:www.esl.tamu.edu 
> <http://www.esl.tamu.edu>
> > 8=/  8=)  :=)  8=)  ;=)  8=)  8=()  8=)  :=)  8=)  8=!  8=)  8=? 8=) 8=0
> >
> >
> >
> > From: Equest-users [mailto:equest-users-bounces at lists.onebuilding.org 
> <mailto:equest-users-bounces at lists.onebuilding.org>] On Behalf Of Peter Schonherr
> > Sent: Wednesday, June 17, 2015 10:26 AM
> > To: equest-users at lists.onebuilding.org <mailto:equest-users at lists.onebuilding.org>
> > Subject: [Equest-users] Thermal mass effects of interior walls
> >
> >
> >
> > Hello,
> >
> >
> >
> >      Is it possible to model the effects of thermal mass of interior walls? if so, how 
> is that done?
> >
> >
> >
> > Peter Schonherr
> >
> >
> >
> >
> > Classification: UNCLASSIFIED
> > Caveats: NONE
> >
> >
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