Radiation effects on transient hot-wire measurements in absorbing and emitting porous media

• Published in: International journal of heat and mass transfer Vol. 47; no. 14; pp. 3279 - 3290
• Main Authors: Gross, Ulrich, Tran, Le-Thanh-Son
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 01.07.2004; Elsevier
• Subjects: Applied sciences; Discrete ordinates method; Energy; Energy. Thermal use of fuels; Exact sciences and technology; Instruments, apparatus, components and techniques common to several branches of physics and astronomy; Materials and auxiliary equipments used in energy engineering; Numerical analysis; Physics; Porous media; Radiation; Thermal instruments, apparatus and techniques; Thermometry; Thermophysical properties; Transient hot-wire method; Porous media; Discrete ordinates method; Numerical analysis; Thermophysical properties; Transient hot-wire method; Radiation; Temperature measurement; Radiation effects; Thermal insulating material; Porous materials; Digital simulation; Measuring methods; Thermal conductivity; Hot wire; Discrete ordinate method
• ISSN: 0017-9310; 1879-2189
• DOI: 10.1016/j.ijheatmasstransfer.2004.02.014

The integro-differential equation governing the combined conduction and radiation heat transfer in a gray medium bounded by two infinite coaxial cylindrical surfaces is solved numerically to analyse the effect of radiation in transient hot-wire measurements in porous thermal insulations. The influences of the extinction coefficient, the emissivity of the wire and the heating power are studied. It is found that the hot-wire method works accurately only in cases where the extinction coefficient exceeds a minimum value which increases with the temperature. The calculated results confirm the linear relationship between measured thermal conductivities and the heating power. The problem of reference temperature for the measured thermal conductivity is also discussed in this work.