[Bldg-sim] LBNL THERM - Boundary Conditions

[Pearson, Nastassja]

I am looking for some guidance in selecting my boundary conditions when modeling a glazing systems in THERM.

A long time ago I attended a THERM training session where they stated that for general projects it was not necessary to model a system to NFRC 100 boundary conditions. They stated we should use a "Simplified" boundary condition model rather than a "comprehensive: one and that a typical, acceptable interior air film coefficient is 8.3 W/mK.

Recently a discussion came up that we should use the "Comprehensive" boundary condition model for every simulation, and that the interior film coefficient should be closer to 3. I did a couple of different runs varying the boundary conditions and the results change significantly. See image below:

[cid:image001.jpg at 01CCD06B.F2C6BA90]

Run 01 is using the default NFRC Conditions. Run 04 is how I was previously taught to do the simulation. Runs 02 and 03 are other variations.

What happens to the model when you set the radiation model to to "Automatic Enclosure Model" compared to "Simplified"?

What boundary conditions (with respect to film coefficients and radiation models) should be used to generate conservative, but realistic results.?


Thanks

Nastassja Pearson
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