How to Model Thin Aluminum Construction [closed]

asked 2023-07-31 16:17:43 -0500

IanVG
261 ●4 ●7

I've got some old specifications that describe a wall panel as:

Infill panel shall be 5/8" exterior type particleboard with 0.011 mil aluminum bonded to both sides

That's pretty thin aluminum (this thin: 1.1e-5 inches or 0.0002794 millimeters). Based off this post, it seems that there are limits on some of the physical properties of materials in EnergyPlus. Does anybody have any advice on how to model/create this material/construction in EPlus?

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Closed for the following reason the question is answered, right answer was accepted by IanVG
close date 2023-08-01 13:24:22.049612

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answered 2023-08-01 12:19:00 -0500

mdahlhausen

9314 ●17 ●11 http://openstudio.net/

If you are measuring a material layer in nanometers, then you should just change the surface emissivity of the other material.

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Great, this makes sense. I accepted this as the right answer. I'll also follow-up when I can with the actual material that I ended up creating for this scenario and post the properties somehow here.

IanVG ( 2023-08-01 13:25:16 -0500 )edit

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answered 2023-08-01 07:58:15 -0500

J Monteiro

1186 ●3 ●10

If the aluminum plate has this thickness, it can be neglected, since neither the thermal resistance of the layer nor the thermal inertia caused by the layer is relevant to the model.

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Hmm, yes this generally what the EPlus Input-Output documentation suggests:

"...Extremely thin and/or highly conductive material layers should be neglected from the Construction rather than included because they will not contribute to the assembly’s overall thermal resistance or heat capacity. For some cases, thin and/or highly conductive materials are a serious problem for the heat transfer modeling and the values for thickness, conductivity, density and specific heat are checked for appropriateness.[...]"

IanVG ( 2023-08-01 13:14:18 -0500 )edit

In addition a few lines further on, the documentation also mentions:

"The absorptance values in this object impart surface properties to the construction and should be applied to the thermally significant inner and outer layers in the overall assembly. Attempting to trick the program by modeling thin “paint” layers to apply surface properties is not a good idea; the models were not intended to support such strategies."

IanVG ( 2023-08-01 13:15:03 -0500 )edit

I believe what this suggests, as @mdahlhausen states below, is that the construction should consist of a single material, where the surface emissivity of the material is that of the thin metal (e.g. here it would be aluminum).

IanVG ( 2023-08-01 13:17:18 -0500 )edit

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