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[EnergyPlus_Support] Re: high surface temperature
I am trying to answer my own question here: why the surface
temperature or MRT seems too high when I simulated natural
ventilation using design day data.
Actually what I want to see is not design day, but a hottest day in
Seattle. I selected Sep. 2nd to test. I uploaded a Excel file
to "FILES", the name is :
XLS_WestZone_SmallOpening_0902_SimulationCompare.xls
The chart shows four simulations for this day.
A. No wind, maximum outside temp 36 C, 10 C daily temperature
range (from ASHRAE Seattle design day data),
B. No wind, maximum outside temp 36 C, 20.7 C daily temperature
range,
C. 5 m/s south wind, maximum outside temp 36 C, 20.7 C daily
temperature range,
D. Real weather data, simulated from 7/1~9/10, so there would no
initialization issue. On Sep. 2nd, maximum outside temp 36.7 C,
minimum 16 C, 3~5m/s wind (S/N)
E. Similar to (D), but simulation starts from 9/2.
The results show big difference between real weather data and design
day (same maximum temp, but small daily temperature range and no
wind). So the question changed to what data to use for system sizing,
especially for natural ventilation.
In addition, the initialization's influence seems not negletable.
Could any inside people give some explanation from the warm-up
algorithms?
Hannah
--- In EnergyPlus_Support@xxxxxxxxxxxxxxx, Hannah Yan
<hannahyan@y...> wrote:
> Rick,
>
> Thank you for the offer. See the attached file.
>
> Let me explain the situation a little bit. For the
> west and east exterior walls, I used 4 inch brick
> outside and 3 inch insulation inside. South, north
> walls and floors are interior walls. Ceiling is
> exposed to outside weather. 4 cooling design days are
> simulated. For the hottest day (1st day), at the cool
> night(25C outside), MRT in the room arrives 35C. At
> the hottest time, the south wall and west wall are
> about 2 C higher than the inside air temperature.
>
> It is true that there is not much ventilation. But I
> still suspected about the initialization, and I want
> to know how to eliminate the initialization effect for
> design days.
>
>
>
> --- Rick Strand <rkstrand@u...> wrote:
> > Hannah:
> >
> > It is difficult to give you any advice about the
> > validity of the surface
> > temperatures you are seeing because the text of your
> > message is relatively
> > vague. How much higher are the temperatures than
> > you are
> > expecting? EnergyPlus does have an initialization
> > process that it goes
> > through, but it should iterate enough days during
> > the warmup process to
> > eliminate the initial conditions. If you like, you
> > can send me your input
> > file and I will see if the temperatures seem
> > unreasonable. That would
> > allow me to look at your other concern as well.
> >
> > Rick Strand
> >
> > At 09:25 AM 7/17/2003 -0700, you wrote:
> > >Hi,
> > >
> > >I am simulating a natural ventilation environment
> > for
> > >several cooling design days without wind. There are
> > >some thermal mass on the floor but not too much for
> > >walls. I think the air temperature looks good, but
> > >surface temperature and MRT seem a little bit high
> > >than I expected. I suspect this is because E+ has
> > some
> > >special initialization that may influence. What do
> > you
> > >think?
> > >
> > >Beside, I found air change rate in .csv output
> > column
> > >BM seems too high and not corresponds to the
> > >infiltration volume in column BL. Is this a bug or
> > >something else?
> > >
> > >Thanks,
> > >
> > >
> > >
> > >
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