[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: [EnergyPlus_Support] Simulation Speed
If the temperature in any zone changes by more than 0.3C, the simulation
will shorten the time step. In your case from 30 to 15 minutes. If
during the 15 minute simulation, the temperature in any zone changes by
more than 0.3C, the simulation will again shorten the time step and
continue this until the maximum zone temperature difference is less than
0.3C. This can mean that you are actually simulating at 1 minute time
steps in a worst case scenario. Check the zone temperatures to see if
they are stable at the thermostat set point temperature. You may also
want to upload this file to the files area in the problem submittals
folder so we can have a closer look.
Filipe madureira wrote:
>
> Hi all,
>
> I’m simulating a large/complex hospital facility.
>
> The geometric model is not very complex but it has a large number of
> thermal zones.
>
> To calculate the energy consumption of primary and secondary system I’ve
> defined a model with the following characteristics:
>
> Inside and Outside Detailed Convection algorithm.
>
> Solution Algorithm: CTF
>
> For the plant loops:
>
> · Cooling and heating equipment are simulated with
> Purchased:ChilledWater and Purchased:HotWater respectively
>
> For Air loops:
>
> · I’ve created constant volume air handling units (AHU) with cooling
> and heating coils. Some AHU provide treated air to a single zone( AHU
> type1) and other ( AHU type2), provide treated air to several zones.
>
> For zone equipment:
>
> · For AHU type 1 zone equipment is a reheat coil. Some zones have
> only temperature control and others have temperature and humidity
> control.
>
> · For AHU type 2 zone equipment is Direct Air to provide the
> necessary outside air. In controlled zones I ‘ve also defined fan coils to
> provide the remaining necessary heating or cooling energy.
>
> For Zone Sizing:
>
> · For zones controlled by AHU type 1 I’ve defined the Outside Air
> volume flow rate, the cooling and heating design air flow rates and
> the air
> flow method as “flow/zone”.
>
> · For the remaining zones outside air is supplied by Direct Air
> through system AHU type 2. For this reason, and because some zones
> have also
> fan coil systems, I set the zone outside air volume flow rate as zero and
> defined the the flow rate in the Direct Air object to avoid outside air
> being supplied by fan coil systems.
>
> For system sizing:
>
> · For AHU type2 I’ve defined the total Outside Air volume flow rate
> (as the sum of the corresponding Direct Air flow rates).
>
> · For AHU type1 I’ve defined the total Outside Air volume flow rate
> with the “autosize” option.
>
> For all components (coils, fans…) except for Direct Air, I let the
> autosize
> option in the autosizable fields to let the program calculate the
> necessary
> values.
>
> The convergence parameters defined were:
>
> Building:
>
> · Loads Convergence Tolerance value 0.04
>
> · Temperature Convergence Tolerance value 0.4
>
> Time step in Hour:
>
> · Time step in Hour 2
>
> System Convergence limits:
>
> · Minimum System time step 1
>
> · Maximum HVAC iterations 50
>
> · (I’ve raised up this value from 20 to 50 because I got a warning
>
> “** Warning ** SimHVAC: Maximum iterations (20) exceeded for all HVAC
> loops”
> )
>
> Fan Coil Unit: 4Pipe and Single Duct: Const Volume: Reheat
>
> · Convergence Tolerance 0.001
>
> With this model I performed two different simulations:
>
> 1) The described building with high internal gains (electric
> equipment, people and lights) which corresponds to the sizing HVAC
> equipment conditions, to estimate annual building HVAC energy consumption
>
> 2) The same model as 1 but with lower internal gains (~50% of total
> internal gains of simulation 1) to estimate total energy consumption to
> check portugueese building energy code
>
> The hourly simulation for an entire year took 9 hour for case 1. For
> case 2
> it took almost one week and a half!!
>
> Is it normal to have such a difference in total simulation time?
>
> Could this simulation time difference be due to the lower internal gains?
> With lower internal gains conduction effects could be more important and
> this could slow down simulations?
>
> The convergence parameters are reasonable?
>
> To define Direct air flow rates instead of autosizing is a correct
> procedure?
>
> Thanks in advance for your help,
>
> Best Regards
>
> Filipe Madureira
>
> Tel: +351 919 293 876 | E-mail: filipe.madureira@xxxxxxxxxxxxx
> <mailto:filipe.madureira%40fluidinova.pt>
>
> __________________________________________________________
>
> FluidInova, Engenharia de Fluidos, SA
>
> TECMAIA - Parque de Ciência e Tecnologia da Maia
>
> Rua Engº Frederico Ulrich, nº 2650 | 4470-605 Moreira da Maia | Portugal
>
> Tel: (351) 229 408 265 | Fax: (351) 229 408 266
>
> E-mail: <mailto:geral@xxxxxxxxxxxxx <mailto:geral%40fluidinova.pt>>
> geral@xxxxxxxxxxxxx <mailto:geral%40fluidinova.pt> | Web:
> <http://www.fluidinova.pt/ <http://www.fluidinova.pt/>>
> http://www.fluidinova.pt/ <http://www.fluidinova.pt/>
>
> [Non-text portions of this message have been removed]
>
>
--
Richard A. Raustad
Senior Research Engineer
Florida Solar Energy Center
University of Central Florida
1679 Clearlake Road
Cocoa, FL 32922-5703
Phone: (321) 638-1454
Fax: (321) 638-1439 or 1010
Visit our web site at: http://www.fsec.ucf.edu
UCF - From Promise to Prominence: Celebrating 40 Years
The primary EnergyPlus web site is found at:
http://www.energyplus.gov
The group web site is:
http://groups.yahoo.com/group/EnergyPlus_Support/
Attachments are not allowed -- please post any files to the appropriate folder in the Files area of the Support Web Site.
EnergyPlus Documentation is searchable. Open EPlusMainMenu.pdf under the Documentation link and press the "search" button.
Yahoo! Groups Links
<*> To visit your group on the web, go to:
http://groups.yahoo.com/group/EnergyPlus_Support/
<*> Your email settings:
Individual Email | Traditional
<*> To change settings online go to:
http://groups.yahoo.com/group/EnergyPlus_Support/join
(Yahoo! ID required)
<*> To change settings via email:
mailto:EnergyPlus_Support-digest@xxxxxxxxxxxxxxx
mailto:EnergyPlus_Support-fullfeatured@xxxxxxxxxxxxxxx
<*> To unsubscribe from this group, send an email to:
EnergyPlus_Support-unsubscribe@xxxxxxxxxxxxxxx
<*> Your use of Yahoo! Groups is subject to:
http://docs.yahoo.com/info/terms/