Re: [EnergyPlus_Support] Re: Peak cooling loads

On Thu, Sep 22, 2011 at 10:14 AM, omarvelling <laxoayi@xxxxxxxxxxxxxxxx> wrote:

Dr. Li and Dru, thanks for your comments.
I can appreciate that the temperature profiles for outdoor dry-bulb and solar radiation pattern are not the same for the designDay and the weather file data and so the results will not match. However, I'm not using a designday for sizing, i'm actually using sizingperiod:weatherfiledays to perform sizing and so would expect the results to match for the same date/time. Any reasons why this is not the case? Thanks
Omar

--- In EnergyPlus_Support@xxxxxxxxxxxxxxx, Dru Crawley <dbcrawley@...> wrote:
>
> Dr Li is correct -- in the schedules you can have different conditions for
> the design days and the design day calculations can omit some of the loads.
> In addition, the climatic condtions are based on the weather parameters that
> you enter -- not the weather file (unless you use the weather file option
> for design conditions). And the solar radiation is calculated as clear sky
> (default).
>
> To see what is going on, include the design days in the simulation output --
> and select environment conditions such as temperature, wind speed, solar
> radiation for the design days -- and for the same date in the weather files.
> You'll see big differences.
>
> On Wed, Sep 21, 2011 at 4:35 PM, YuanLu Li <yli006@...> wrote:
>
> > **
> >
> >
> > I do not think the results would be the same, as they are averaged values
> > for different input data..
> >
> > The peak load conditions for the building may be different for the same
> > day, because the temperature profiles for outdoor dry-bulb and solar
> > radiation pattern are not the same for the designDay and the weather file
> > data.
> >
> > Compare the input data as well, to see whther they are the same. If you
> > made the designDay profile to track the extreme day weather file ODT, it may
> > give you a better match.
> >
> > Dr. Li
> >
> > ------------------------------
> > To: EnergyPlus_Support@xxxxxxxxxxxxxxx
> > From: laxoayi@...
> > Date: Wed, 21 Sep 2011 19:33:27 +0000
> > Subject: [EnergyPlus_Support] Re: Peak cooling loads
> >
> >
> >
> > Thanks Jean, I've reached the same conclusion as yours so I tried to
> > perform one more run with both the sizingperiod:weatherfiledays and the
> > runperiod limited to the same single day. I then changed the "Number of
> > Times Runperiod to be Repeated" to 20 (the results actually converged after
> > 15 repetitions). Despite this, the value of the sizing peak cooling load did
> > not match that of the simulation although peak loads occurred at the same
> > date and time. Anyways I now think I have a better understanding of what is
> > going on thanks to you.
> >
> > --- In EnergyPlus_Support@xxxxxxxxxxxxxxx, "Jean marais" <jeannieboef@>
> > wrote:
> > >
> > >
> > > Okay, sorry. As far as I know the .eio file shows the design loads used
> > for sizing your equipment, i.e. from your sizing run. I'm not sure what
> > sizing parameters sizingperiod:weatherfiledays uses (it may use the worst
> > case day from the weather file and simulate it over and over during
> > sizing...there are also summer weeks data where the week is possibly
> > repeated, however it surely doesn't repeat years untill the start of the
> > year converges with the end of the year which is what you'd have to do to
> > get the sizing max load values the same as the max loads in the year. as the
> > statistical weather year does not include the 1/100 year hot day, unless you
> > tell it to...there is a way I think, most systems are not sized this way.)
> > >
> > >
> > >
> > > --- In EnergyPlus_Support@xxxxxxxxxxxxxxx, "omarvelling" <laxoayi@>
> > wrote:
> > > >
> > > > Thanks Jean, I appreciate what you mentioned in your reply but I'm not
> > trying to size any system here, I'm only looking for peak cooling loads and
> > that is why I used sizingperiod:weatherfiledays instead of
> > sizingperiod:designday to determine the date/time that the peak load occurs
> > on and its magnitude. Bearing that in mind, should'nt I expect to find the
> > value of the peak load in the .eio file to match the value of the ideal
> > loads air system sensible cooling rate in the output variable file at the
> > same timestep?
> > > >
> > > > Thanks a lot, your help is very much appreciated,
> > > > Omar
> > > >
> > > > --- In EnergyPlus_Support@xxxxxxxxxxxxxxx, "Jean marais" <jeannieboef@>
> > wrote:
> > > > >
> > > > > The peak cooling load during your statistical weather year is "most
> > probable". The design day is used to size your systems for that once in a
> > hundred years hot day (the same day occuring over and over again untill
> > building temperatures at the beginning and end of the day equal/match those
> > of the day before and after) x sizing:parameter factors. the design day
> > cooling loads are therefore much more than the statistical year's worst day.
> >
> > > > >
> > > > > --- In EnergyPlus_Support@xxxxxxxxxxxxxxx, "omarvelling" <laxoayi@>
> > wrote:
> > > > > >
> > > > > > Hi all,
> > > > > >
> > > > > > I'm trying to determine the peak cooling loads for my model. I used
> > weather file days as my sizing period and also performed an annual
> > simulation using an ideal loads air system to control the zones. I checked
> > the time of the peak design sensible cooling load from the .eio output file
> > and then checked the output variable file but found the value of the ideal
> > loads air sensible cooling rate to be different from that of the .eio file
> > at the same timestep. Is this normal? Am I missing something here? Why do
> > the values of the sizing differ from the annual simulation although I'm
> > using weather file days to perform sizing?
> > > > > >
> > > > > > Thanks
> > > > > >
> > > > >
> > > >
> > >
> >
> >
> >
> >
>