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Re: [EnergyPlus_Support] Re: about the minimum system air flow ratio
Not knowing which system and equipment you use,
have you looked at the breakout of heating versus
reheating? In one of my recent simulations the reheat
was almost as much as the heating energy in total and
exceeds from early Spring through Fall. (No heat in
the summer). More humid locations with relatively low
heating needs will have highest reheat energy.
Since the heating end-use includes both heating and
reheating (something we plan to change for V 1.2.2),
I had to look at individual zone results. I added this
variable report:
Report Variable,
*, !- Key_Value
Heating Coil Energy, !- Variable_Name
monthly; !- Reporting_Frequency
Which gives energy results for all the heating coils
including reheat.
beyangj
<beyangj@xxxxxxxxxx To: EnergyPlus_Support@xxxxxxxxxxxxxxx
m> cc:
Subject: [EnergyPlus_Support] Re: about the minimum system
11/14/2004 07:13 AM air flow ratio
Please respond to
EnergyPlus_Support
Dear,
Thank you very much for your reply! I used SET POINT MANAGER:WARMEST
to reset the supply air temperature as mentioned by Mike and did the
simulation again, but it didn't seem to work. The heating was also
needed all the year round, and the amount needed was similar to that
before.The smaller the minimum system air flow ratio and the zone
minimum air flow fraction were set, the smaller heating would be
used in the summer and winter. Compared the simulation results with
that simulated using DOE-2.1E, the cooling energy was similar, but
the heating energy was greatly different, and there was no heating
in the summer in the DOE-2.1E simulation results, and all the
parameters were the same in the EnergyPlus model and the Doe-2.1E
model. The heating energy simulated using DOE-2.1E was much larger
than that simulated using EnergyPlus in winter when the minimum
system air flow ratio and the zone minimum air flow fraction were
set as smaller values so as to have a smaller heating energy in the
EnergyPlus model. I want to know how can I get the reasonable
results? Could you give me some more advice? Thanks again!
Best,
Stewart
--- In EnergyPlus_Support@xxxxxxxxxxxxxxx, "Michael J. Witte"
<mjwitte@g...> wrote:
> If humidity control is not an issue, you can use SET POINT
MANAGER:WARMEST to
> reset the supply air temperature. This will reduce the amount of
summer reheat
> required but will also increase fan power. Or you can schedule
reheat coils
> off for the summer and let the spaces overcool.
>
> Mike
>
> On 11 Nov 2004, at 10:54, Edward Lyon wrote:
>
> >
> > You may not have a simulation mistake. A variable air volume
system
> > will use heat during summer cooling to avoid over cooling a
space. For
> > instance, if your system discharges 50F air, but the cooling
load only
> > requires 60F air at the minimum flow volume, heat will be needed
to
> > maintain set point temperature. Typically you will need a cold
supply
> > air temperature to lower the dew point of the ventilation air for
> > humidity control. Maintaining humidity control requires heating
to
> > avoid over cooling the space.
> >
> > Ned Lyon
> >
> > Senior Project Manager
> > Simpson Gumpertz & Heger Inc.
> >
> > 41 Seyon Street
> > Building #1, Suite 500
> > Waltham, MA 02453
> >
> > Phone: 781-907-9000
> > Fax: 781-907-9009
> >
> >
> > >>> beyangj@h... 11/11/2004 10:03:09 AM >>>
> >
> > Dear,
> > In my simulation, the minimum system air flow ratio and the zone
> > minimum air flow fraction were varied several times, and that
> > affected the result of cooling energy slightly, but that
affected
> > the result of heating energy obviously. I am wondering why
there is
> > some heating in the summer days, and the heating just occurs in
the
> > period the system is turned on. When the ratio and the fraction
> > mentioned before are set smaller, the heating in the summer
would
> > also become smaller. As a matter of fact, there is no heating in
the
> > summer days, but there is always some heating in the summer days
> > even the minimum system air flow ratio is set as 0.01. How can I
get
> > rid of this mistake? In addition, I want to know how much these
> > ratio values affect the results. Thanks in advance!
> >
> > Best,
> >
> > Stewart
> >
> >
> >
> >
> >
> >
> > The primary EnergyPlus web site is found at:
> > http://www.energyplus.gov
> >
> > The group web site is:
> > http://groups.yahoo.com/group/EnergyPlus_Support/
> >
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appropriate
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> >
> >
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> >
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>
> ========================================================
> Michael J. Witte, GARD Analytics, Inc.
> EnergyPlus Testing and Support
> EnergyPlus-Support@g...
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