Limestone in the database

[Ned Lyon]

The properties for limestone in the current database are probably wrong. Using the existing limestone generats excessive convergence errors. Looking at the moisture sorption function, the first two values 0% and 70% both have 0 moisture content. There is then a rapid rise above 70%. While I didn't test any material, this property doesn't make sense to me. Changing the 70% moisture content to 1 significantly reduces, but does not eliminate convergence errors. Can you check the source data?

[Thomas]

Dear Mr. Lyon,

the data for the limestone in the "Generic North America Database" have been taken from ASHRAE Report 1018-RP where the measurements at 49.9% and 70.5% RH do indeed show a water content of 0 kg/kg. Apparently this has been faithfully transferred to the WUFI database although it does not really make sense and may cause difficulties for the numerics. It is certainly more realistic to set the 70% value to something greater than zero or to delete the 70% entry altogether, so that WUFI linearly interpolates between 0 kg/m³ at 0% and 2.5 kg/m³ at 88.6% RH.

While reviewing the moisture storage function, I noticed another problem with the limestone: the moisture content for 99.93% should be 32.5 kg/m³, not 3.25 kg/m³, and the extrapolated value for free saturation should accordingly be 34 kg/m³ instead of 3.4 kg/m³.

If you still have convergence problems with the corrected values, you might try the following provisional moisture storage function which I derived by fitting a model function to the measured data and which is smoother than the original curve in the database:

Code: Select all

RH    w [kg/m³]
0.0         0.0
0.5         0.29
0.8         0.96
0.9         2.05
0.93        2.96
0.95        4.12
0.99       15.1
0.999      31.8
0.9999     35.1
1          35.5

Regards,
Thomas