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Experimental investigation of conjugate heat transfer through post-frame building walls

Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan

Citation:  2018 ASABE Annual International Meeting  1800030.(doi:10.13031/aim.201800030)
Authors:   Andrew J Holstein, David R Bohnhoff, Shengzhi He
Keywords:   Guarded Hot Box, Heat Loss, Heat Transfer, Post-Frame Building, Thermal Envelopes, Thermal Resistance.

Abstract. A rotatable guarded hot box was used to measure heat transfer through five different post-frame building thermal envelopes. The five configurations consisted of an insulated and an uninsulated specimen featuring offset outer and inner inset girts, an insulated and an uninsulated specimen with bookshelf girts, and a bookshelf girt specimen utilizing a radiant barrier. Envelopes were subjected to a range of mean sample temperatures, and were tested both with heat transfer occurring horizontally and with heat transfer occurring downwards. Effective thermal resistance was found to be up to 13% higher for specimens with offset girts, up to 59% higher for specimens transferring heat downwards, and up to 29% higher at 20°C than at 35°C. Comparison of experimental results to predictions that assume one-directional heat transfer normal to the wall surface reveal that one-dimensional equations over-predict the thermal resistance of high emissivity envelopes by an average of 17% and as much as 48%. These equations, however, under-predict the thermal resistance of low emissivity envelopes for which heat transfer acts horizontally by 21%. To increase the accuracy of thermal envelope prediction, experimental determination of thermal resistances should be used for complex geometries where conjugate heat transfer is expected.

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