One of the interior wall types in DOE-2 is "AIR", for which there is a default library member "Default Air Wall Construction" with heat transfer of U = 2.7 Btu/h-ft2-?F. The help menu describes this as the recommended value but gives no reference for it. How might we come up with a range of values?
I frequently model air walls for everything from open doors to transfer grills to stairwells etc. It is also critical to my method of modeling DOAS systems where I assign the DOAS to plenum spaces and the zonal systems to the spaces below.
There are many situations where I suspect the default 2.7 value is too small, such as the DOAS system method I described, or any time you have forced air systems on either or both sides of the air wall. Other examples could be displacement ventilation systems, or high bay systems with fans to avoid stratification.
The relevance of changing the number is that higher values simulate higher rates of mixing of air, and can impact the unmet hours substantially if the zone temperatures separated by the air wall have a high delta-T between them.
What say you, simulationists?
Thanks,
~Bill
William Bishop, PE, BEMP, BEAP, CEM, LEED AP | Pathfinder Engineers & Architects LLP
Senior Energy Engineer
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