Interface resistance in thermal insulation materials with rough surfaces

Clarke, R, Shabani, B and Rosengarten, G 2017, 'Interface resistance in thermal insulation materials with rough surfaces', Energy and Buildings, vol. 144, pp. 346-357.


Document type: Journal Article
Collection: Journal Articles

Title Interface resistance in thermal insulation materials with rough surfaces
Author(s) Clarke, R
Shabani, B
Rosengarten, G
Year 2017
Journal name Energy and Buildings
Volume number 144
Start page 346
End page 357
Total pages 12
Publisher Elsevier
Abstract We have previously shown how errors due to interface resistance arising in the measurement of highly-conducting insulation materials may be minimized by the use of flexible buffer sheets at the plate interface. We have found however that for materials with very rough surfaces, such as some building boards, thermal resistance and test thickness are both measured to be higher when harder buffers are used. This paper reports on an experimental study of nine materials and four buffer types to better quantify these effects. Thermal resistance was higher by up to 0.01 m2.K/W and thickness by up to 0.5 mm using the hardest buffer relative to the softest. An analytical model has been developed, allowing measured roughness to be expressed as flat high and low areas of varying height and area fraction so that thermal resistance and height variations may be predicted as a function of roughness. These predictions have agreed reasonably well with optical roughness measurements. The model further predicts that interface-resistance errors are proportional to surface roughness and are always present with harder buffers, typically reaching 010 m2.K for a mean roughness amplitude (Sa) of 200 μm. However with softer buffers these errors are absent below an onset level, typically at an Sa value of 60 μm.
Subject Heat and Mass Transfer Operations
Keyword(s) thermal resistance measurement
rough surfaces
interface resistance
thermal insulation
heat flow meter
DOI - identifier 10.1016/j.enbuild.2017.03.012
Copyright notice © 2017 Elsevier B.V
ISSN 0378-7788
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