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Re: [EnergyPlus_Support] Energy Balance
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" <mjwitte@xxxxxxxx> 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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