DOI: 10.1615/ICHMT.1986.IntSympHMTinRefCryo
ISBN Print: 978-3-54017-957-3
Analysis of Emittance Measurements with Heat Flow Meter and Guarded Hot Plate Apparatus
ABSTRAKT
The development of the theory of heat transfer through insulating materials in the last 15 years has emphasized the importance of radiation in light density insulating materials. The presence of radiation heat transfer explains the so-called thickness effect (i.e. the increase of the measured conductivity with the specimen thickness), that originated in the last decade a religious war in the world of thermal insulation between thermal resistance and thermal conductivity supporters. Most of the fights on the thickness effect were due to test errors and differences in testing conditions. Whenever radiation plays a significant role in the overall heat transfer process within an insulation, different results shall be expected if the emittances of the surfaces bounding the materials are different. Hence, in guarded hot plate and heat flow meter measurements on light density insulations, the definition of testing conditions shall include the apparatus emittances.