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Re: [EnergyPlus_Support] Energy Balance
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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