I do not know the actual problem causing the long execution time.
In digital calculation, the thick construction material means that the reflected quantity would not reach the source end in time for correct summation. Short sampling time with some algorithm may not converge due to over swings. The longest sampling time available in EPlus is one hour.
If you know that the heat transfer quantity is small, this is the time to use adiabatic condition.
Dr. Li
To: EnergyPlus_Support@xxxxxxxxxxxxxxx
From: jeannieboef@xxxxxxxxx
Date: Wed, 7 Dec 2011 18:12:22 +0000
Subject: [EnergyPlus_Support] Re: Easy question - Very thick massive external floor
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Primary EnergyPlus support is found at:
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The primary EnergyPlus web site is found at:
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In digital calculation, the thick construction material means that the reflected quantity would not reach the source end in time for correct summation. Short sampling time with some algorithm may not converge due to over swings. The longest sampling time available in EPlus is one hour.
If you know that the heat transfer quantity is small, this is the time to use adiabatic condition.
Dr. Li
To: EnergyPlus_Support@xxxxxxxxxxxxxxx
From: jeannieboef@xxxxxxxxx
Date: Wed, 7 Dec 2011 18:12:22 +0000
Subject: [EnergyPlus_Support] Re: Easy question - Very thick massive external floor
Comming back to the composite wall concept. One could quite easily create a composite equivalent consisting of 3 layers, with an equivalent heat tranfer resistance and thermal capacitance, but I don't think it's the many layers that result in problems, I think it is the high thermal capacitance of a construction that thick.
If I'm right then the only way to battle the problem is to slice the construction at some point (say midway) and apply a constant (or varying) temperature at this point using the otherside coefficients. That would be difficalt to calculate. I could use the internal source object (since I have it anyway) to report the surface temperature at a given layer over the year. From this I could get a average temperature (or variable) and calculate what otherside coeff would be needed to achieve this. I would then cap off the contruction at this layer and apply the otherside coeff here.
What do you think?
If I'm right then the only way to battle the problem is to slice the construction at some point (say midway) and apply a constant (or varying) temperature at this point using the otherside coefficients. That would be difficalt to calculate. I could use the internal source object (since I have it anyway) to report the surface temperature at a given layer over the year. From this I could get a average temperature (or variable) and calculate what otherside coeff would be needed to achieve this. I would then cap off the contruction at this layer and apply the otherside coeff here.
What do you think?
__._,_.___
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.
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