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Re: [EnergyPlus_Support] Energy Balance

To: EnergyPlus_Support@xxxxxxxxxxxxxxx
Subject: Re: [EnergyPlus_Support] Energy Balance
From: "Michael J. Witte" <mjwitte@xxxxxxxx>
Date: Tue, 6 Sep 2005 13:03:44 -0500
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See page 722 (pdf p. 755) for explanations of these variables.  In a nutshell, 
these report the load request from the thermostat.  Your example says that the 
zone requested heating (predicted load is positive), but the HVAC system 
delivered cooling.  Check the HVAC system controls and availability schedules 
to determine why the system did no provide heat when requested.

Mike


On 5 Sep 2005, at 11:59, Ali_Ajmi wrote:

> "These are all explained in the Input Output Reference "... I search it before
> sending you email and I tried again now, unfortunately, I could not find enough
> information on Page 1044, could advise any different documents. Mike, thanks for
> the elaboration of the first question. However, still I could not understand the
> the second and third variables:
>    2- Zone/Sys Sensible Load Predicted [W]
>    3- Zone/Sys Sensible Load to Cooling Setpoint Predicted[W]
> 
> Also, the Zone/Sys Sensible Load Predicted int the my output for the North Zone
> is 1.52 E+03 where the Zone/Sys Sensible Cooling Rate [W] is 4.09E+02. Why they
> are so different?  
> 
> Thanks in advance
> 
> Ali
>   ZONE NORTH:Zone/Sys Sensible Cooling Rate[W](Daily)ZONE NORTH:Zone/Sys
>   Sensible Load Predicted[W](Daily)4.09E+021.52E+034.73E+027.00E+02
> > 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.
> > 
> 
> 
> "Michael J. Witte" <mjwitte@xxxxxxxx> wrote:
> 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" 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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> > > > 
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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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> 



========================================================
Michael J. Witte, GARD Analytics, Inc.
EnergyPlus Testing and Support      
EnergyPlus-Support@xxxxxxxx




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