Re: [EnergyPlus_Support] CTF vs. CondFD results

[Bereket Nigusse <nigusse_ba@xxxxxxxxx>]

 

Liam,

 

To diagnose the possible causes of the difference it is always helpful to see the material types and the corresponding thickness of the heavy mass construction. For light constructions both method should show good match provided all other inputs are correct and identical. I suggest you may want to compare the two procedures by changing the layers thckness (use light construction) to rule out other input errors.

Bereket

--- On Fri, 11/6/09, Liam <liambrn@xxxxxxxxx> wrote:

From: Liam <liambrn@xxxxxxxxx>
Subject: [EnergyPlus_Support] CTF vs. CondFD results
To: EnergyPlus_Support@xxxxxxxxxxxxxxx
Date: Friday, November 6, 2009, 2:22 PM

 

Hi All,

I'm modeling a building of fairly heavy mass so I want to use the CondFD algorithm to better characterize transient effects. A comparison between CTF and CondFD yields differences in predicted heating loads of 100% or more.

I repeated the comparison for several of the example files, e.g., 4ZoneWithShading_ Simple_1 and got similar differences.

Everything in the models is identical except for HeatBalanceAlgorith m. I used 20 time-steps/hour for both algorithms.

Any thoughts as to what might be happening?

Thanks in advance!

Liam O'Brien

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