[EnergyPlus_Support] Re: Zone Temperature Peaks too Early

["jeffreylauck" <JeffLauck@xxxxxxxxx>]

OK, here's a summary of what I've tried and the results:

Changed ZoneCapacitanceMultiplier from 1 to 2   ==> No change in peak time

Set convection coefficient for AllInteriorWalls to 7.7 W/m2-K  ==> No change in peak time

Set convection coefficient for AllInteriorSurfaces to 7.7 W/m2-K  ==> No change in peak time

Set convection coefficient for AllInteriorWalls to 1 W/m2-K  ==> No change in peak time

Set convection coefficient for AllInteriorSurfaces to 0.3 W/m2-K  ==> Peaks shifted to a later time for several of the days but it's not consistent

I'm beginning to think it's something other than convection.  Any thoughts?

Thanks,

Jeff

--- In EnergyPlus_Support@xxxxxxxxxxxxxxx, Joe Huang <YJHuang@...> wrote:
>
>  From the sounds of it, i.e., hourly profiles are similar but just shifted forward, my 
> guess is that the amount of thermal capacitance is okay, but that the coupling to the air, 
> i.e., convection coefficients, are the source of the problem.
> 
> Joe
> 
> Joe Huang
> White Box Technologies, Inc.
> 346 Rheem Blvd., Suite 108D
> Moraga CA 94556
> yjhuang@...
> www.whiteboxtechnologies.com
> (o) (925)388-0265
> (c) (510)928-2683
> "building energy simulations at your fingertips"
> 
> 
> On 5/7/2013 3:39 PM, Griffith, Brent wrote:
> >
> > An easy thing to try is to increase the sensible thermal capacitance of the zone's air 
> > using the ZoneCapacitanceMultiplier:ResearchSpecial object.
> >
> > *From:*EnergyPlus_Support@xxxxxxxxxxxxxxx [mailto:EnergyPlus_Support@xxxxxxxxxxxxxxx] 
> > *On Behalf Of *jeffreylauck
> > *Sent:* Tuesday, May 07, 2013 4:02 PM
> > *To:* EnergyPlus_Support@xxxxxxxxxxxxxxx
> > *Subject:* [EnergyPlus_Support] Re: Zone Temperature Peaks too Early
> >
> > Jean,
> >
> > Thanks for your response. I suppose it's possible that internal surfaces are slowing 
> > convection heat transfer in the actual house, but there's not a lot of furniture in the 
> > space. A small couch, a chair, and a table are about it.
> >
> > The only way I can think of to test this theory is to increase the roughness of the 
> > internal surfaces in the zone. Do you have any other suggestions?
> >
> > Thanks,
> >
> > Jeff
> >
> > --- In EnergyPlus_Support@xxxxxxxxxxxxxxx <mailto:EnergyPlus_Support%40yahoogroups.com>, 
> > "Jean marais" <jeannieboef@ <mailto:jeannieboef@>> wrote:
> > >
> > > Could it be that the actual convection from surfaces is different or more or less than 
> > those modelled thereby transfering heat from surfaces to air faster or slower. Are there 
> > more internal surfaces like furniture which could contribute the these effects?
> > >
> > > Jean
> > >
> > > --- In EnergyPlus_Support@xxxxxxxxxxxxxxx 
> > <mailto:EnergyPlus_Support%40yahoogroups.com>, "jeffreylauck" <JeffLau ck@> wrote:
> > > >
> > > > Hello All,
> > > >
> > > > First off, thanks for a great community. I've learned a lot from searching through 
> > the message archives over the past few months.
> > > >
> > > > I have a model of a Passive House that I am trying to validate using measured data 
> > from the actual house. I've created an hourly schedule file for the lights, electric 
> > equipment, window usage, blind usage, and hot water consumption based on sub-hourly data 
> > collected at the site. I'm using a custom weather file from the roof-top weather station 
> > that monitors dry bulb temp, relative humidity, wind speed and direction, and global 
> > horizontal solar radiation. The diffuse radiation component was estimated using the Erbs 
> > model prior to importing the data into the weather utility. Currently I'm only looking 
> > at the summer of 2012.
> > > >
> > > > The problem I'm having is that the peak temperatures in the model occur 2-4 hours 
> > before the measured data (2-3 hours in July and September, 3-4 hours in August). Here's 
> > what I've determined so far:
> > > >
> > > > 1. It's not due to a time shift in the data. I've verified that all data is GMT-8 
> > and that no Daylight Savings flags are included in the IDF.
> > > > 2. It's not due to a lack of thermal mass. I added a bunch of internal mass as a 
> > test and the peaks were reduced but occurred at the same time as previous models. Also, 
> > I'm using CondFD with 9 nodes and a 1-minute timestep.
> > > > 3. I don't think it's due to my custom weather file, as I get a similar results 
> > using TMY data.
> > > >
> > > > Does anyone have any suggestions on where to look next? Any ideas would be greatly 
> > appreciated.
> > > >
> > > > Thanks,
> > > >
> > > > Jeff
> > > >
> > >
> >
> >
>



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