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Re: [EnergyPlus_Support] Energy Balance
These are all explained in the Input Output Reference (search the document for
the report variable names). If the system has no outside air, then number 1
(Zone/Sys Sensible Cooling Rate) will be equal to the DX coil sensible load (DX
Coil Sensible Cooling Rate[W]) minus any fan heat (Fan Electric Power[W] less
any motor heat fraction which is not in the airstream).
Mike
On 2 Sep 2005, at 18:13, Ali_Ajmi wrote:
> Mike I am still have confusing of interpretation some of the report variables.
> Could you kindly elaborate the meaning of the following variables:
> 1- Zone/Sys Sensible Cooling Rate [W]
> 2- Zone/Sys Sensible Load Predicted [W]
> 3- Zone/Sys Sensible Load to Cooling Setpoint Predicted[W]
>
> Mike, if I am using DX:Cooling Coil System (unitary), is it possible to know how
> much each zone has used out of the total DX system consumption or load? Is any
> of the above variable represent the zone load that sum with other zones load
> which at the end represented by the DX:Cooling System.
>
> Regards
> Ali
>
> "Michael J. Witte" <mjwitte@xxxxxxxx> wrote:
> No attachment received (not allowed on this group). In the yahoo group files
> area, in the Examples folder there are two zip files with example UAdeltaT
> calculations. Is your example steady-state? Are you adding the inside and
> outside film coefficients to the construction conductivities (these are report
> variables)? I am very confident it will balance. I suggest you create a very
> simple model (no windows, no internal gains, constant temperature, single
> material layer) and prove the balance first. Then add other components one-by-
> one. Also, for windows, the "heat gain" and "heat loss" report variables are
> net, including solar gains as well as conduction, so these should not be added
> again in the UADeltaT summation.
>
> Mike
>
>
>
> On 31 Aug 2005, at 17:06, Ali_Ajmi wrote:
>
> > Thanks Mike. I calculated the heat gain/loss through the opaque using
> > UADelataT, even thought the U was quite high 28.7 W/m2.K. Then added the
> > results to heat gain/loss from the windows and constant load (lighting,
> > peoples) that done by E+. This summation has been compared to the load
> > calculated from multiplying the mass flow rate by the enthalpy difference of
> > the in/out North Zone as an example. The result, shown in the attached excel
> > sheet, shows the zone load much higher than the system load. Could you please
> > advise of error(s) in this approach.
> >
> > Regards
> > Ali
> >
> > "Michael J. Witte" wrote:
> > Are you interpreting "energy transfer" as the envelope heat transfer to/from
> > the zone? This is not what it represents. The Energy Transfer meters are used
> > for various HVAC system energy flows. See the meter details (mtd) output file
> > for a list of specific report variables that are accumulated on a given meter.
> >
> >
> > There are no report variables available for the envelope contribution to the
> > zone load. The list of variables here are heat *gains*, presumably all
> > components except the heat transfer through opaque surfaces. The HVAC system
> > meets heating/cooling *loads*, and portions of the gains become loads
> > significantly later due to thermal mass. Comparing over a daily basis helps,
> > but not all gains become a load.
> >
> > If you want to confirm the physics and calculate the opaque surface heat
> > transfer, then the only accurate way is to set up a steady-state design day
> > and use UAdeltaT to calculate the surface heat transfer.
> >
> > Mike
> >
> >
> > On 25 Aug 2005, at 19:11, Ali_Ajmi wrote:
> >
> > > Hi All,
> > > I tried to balance the energy that losses in the North zone, in my five zone
> > > building, and energy needed by the system and gain by the solar to cover
> > > that losses. The report and meter variables that shown below shows that the
> > > energy transfer out of the zone in the first day of January too high
> > > comparable to the energy should be compensated the loss by the heating coil,
> > > people, lighting. A short list for the variables that I used to do this
> > > analysis is below. could any one figure out which variable I may missed or
> > > error of value conversion from W to J.
> > >
> > > ZONE NORTH:Zone Window Heat Gain[W](Daily)
> > >
> > > ZONE NORTH:Zone Window Heat Gain[J](Daily)
> > >
> > > ZONE NORTH:Zone Window Heat Loss[W](Daily)
> > >
> > > ZONE NORTH:Zone Window Heat Loss[J](Daily)
> > >
> > > ZONE NORTH:People-Total Heat Gain[J](Daily)
> > >
> > > ZONE NORTH:Electric Eq-Total Heat Gain[J](Daily)
> > >
> > > ZONE NORTH:Cat00 Electric Eq-Total Heat Gain[J](Daily)
> > >
> > > ZONE NORTH:Infiltration-Sensible Heat Loss[J](Daily)
> > >
> > > ZONE NORTH:Infiltration-Sensible Heat Gain[J](Daily)
> > >
> > > EnergyTransfer:Zone:ZONE NORTH [J](Daily)
> > >
> > > 6.67E-01
> > >
> > > 2.40E+06
> > >
> > > 1.57E+03
> > >
> > > 8.64E+12
> > >
> > > 1.09E+08
> > >
> > > 8.48E+07
> > >
> > > 8.48E+07
> > >
> > > 1.62E+08
> > >
> > > 0.00E+00
> > >
> > > 1.15E+08
> > >
> > > Thanks in advanced
> > >
> > > Ali
> > >
> > >
> > >
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> >
> > ========================================================
> > Michael J. Witte, GARD Analytics, Inc.
> > EnergyPlus Testing and Support
> > EnergyPlus-Support@xxxxxxxx
> >
> >
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> ========================================================
> Michael J. Witte, GARD Analytics, Inc.
> EnergyPlus Testing and Support
> EnergyPlus-Support@xxxxxxxx
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========================================================
Michael J. Witte, GARD Analytics, Inc.
EnergyPlus Testing and Support
EnergyPlus-Support@xxxxxxxx
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