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Re: [EnergyPlus_Support] mixing autosized and manual input for a BASEBOARD HEATER:Water:Convective object



1.  This will be undersized, because the temperature difference in the 
denominator needs to be a log mean temperature difference which includes the 
leaving air and water temperatures, which you do not know.  (A new way of 
inputting baseboard heat capacity is in the plan for the future.)

2.  I am not sure I can explain why the peak output is smaller thatn the 
heating design load.  Are the simulation outputs from "Do the design day 
simulations" or "Do the weather file simulation"?

3.  There is a bug in the user specification of UA for the baseboard.  This has 
been fixed for the 1.3.0 release which will be available soon.

Mike


On 25 Apr 2006 at 16:45, Elmer Morrissey wrote:

> Hello all, 
> 
> I have a question pertaining to autosizing BASEBOARD 
> HEATER:Water:Convective objects. 
> 
> In the simulation model, the BASEBOARD HEATER:Water:Convective 
> objects are the only energy tempering devices in the room.
> 
> Simulation Run 1: Set the UA from UA = q(loss) / (t(water)-t(air)) 
> and autosize water flow rate
> If I run the simulation and concentrate on one particular zone, the 
> heating design load is 718.55 W. Assuming the room temp is 20C and 
> the water temp is 80C, this would leave a UA of 11.98 W/dK. However, 
> if you use this values in the input configuration for UA: (1) the 
> zone temperature is not consistently maintained at 20C and (2) the 
> maximum load from the heater is never greater than 360.81 W. 
> 
> Simulation Run 2: Autosize the UA and water flow rate
> EnergyPlus calculates the values of UA to be 18.933. The zonal 
> conditions are spot on. The only odd behaviour is that the max 
> output from the heater is never greater than 600 W.
> 
> Simulation Run 3: Set the UA from the last run and water flow rate
> Now the zonal conditions are not maintained even though nothing was 
> changed except manually configuring the UA syntax to the autosized 
> value from the previous run.
> 
> Can anyone explain this?
> 
> Kind regards
> 
> -Elmer
> 
> 
> 
> 
> 
> 
> 
> 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.idf and press the
> "search" button.
>  
> Yahoo! Groups Links
> 
> 
> 
>  
> 
> 
> 
> 


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





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