[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: [EnergyPlus_Support] understanding coil autosizing
EnergyPlus uses a SummerDesignDay and WinterDesignDay or design period. It applies these outdoor environmental conditions to the building object. All schedules objects for other inputs such as internal loads, infiltration or equipment availability separately define themselves for the designday. The building behaves as it should and the energy required to keep each zone at its required temperature is calculated at each time step. The largest load found over all the time steps is then the peak load that must be satisfied.
Next the program looks at what supply air temperature and humidity was defined by the user. For that design air supply temperature and humidity, the required volume flowrate is calculated to match the peak load.
This flowrate and temperature humidity combination is used in the last step to size all the equipment and includes user over or undersizing factors.
So if you have multiple zones, you may control the central AHU via a master zone or Warmest Zone or, or, or...so many options. The program figures out the total peak volume flowrate required and the required supply temperature humidity.
If you are autosizing the dxcoil, EnergyPlus will figure out what to fill in the fields (such as rated capacity, rated CoP, rated SHR) so that a coil size results such as to meet the supply air conditions required at peak load whilst using a coil model that draws on normalized performance curves. So you end up with a more or less realistic coil that also behaves realistically over a whole range of conditions and not only at peak load times. Similar is true of water coils.
Problems with this procedure tend to occur when the user specifies conditions which cannot be met due to other constraints imposed. Example, a user specifies a design supply temperature that is colder than the design supply water temperature to a water coil.
On 1 Sep 2015 5:09 pm, "
a.aelhefni@xxxxxxxxx [EnergyPlus_Support]" <
EnergyPlus_Support@xxxxxxxxxxxxxxx> wrote:
Â
hi guys ,
I'm designing a case where I need to size my cooling coil the following way :
  Program compares OA peak conditions : 1- peak dry bulb and mean coincident wet bulb temperature
                                2- peak dew point and mean coincident dry bulb temp
                                3- peak wet bulb with mean coincident dry bulb temp
  and select the case having highest enthalpy .
  Therefore by knowing this enthalpy and the enthalpy required after coil , a coil size is selected .
Does energyplus work it that way ? anyone has a hint how the program sizes coils ?Â
__._,_.___
Posted by: Jean Marais <jeannieboef@xxxxxxxxx>
Primary EnergyPlus support is found at:
http://energyplus.helpserve.com or send a message to energyplus-support@xxxxxxxx
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 currently allowed but be mindful that not everyone has a high speed connection. Limit attachments to small files.
EnergyPlus Documentation is searchable. Open EPlusMainMenu.pdf under the Documentation link and press the "search" button.
![]()
__,_._,___