Direct and indirect methods for calculating thermal emission from layered structures with nonuniform temperatures

L. P. Wang, S. Basu, Z. M. Zhang

Research output: Chapter in Book/Report/Conference proceedingConference contribution

Abstract

The determination of emissivity of layered structures is critical in many applications, such as radiation thermometry, microelectronics, radiative cooling, and energy harvesting. Two different approaches, i.e., the "indirect" and "direct" methods, are commonly used for computing the emissivity of an object. For an opaque surface at a uniform temperature, the indirect method involves calculating the spectral directional-hemispherical reflectance to deduce the spectral directional emissivity based on Kirchhoff's law. On the other hand, a few studies have used a combination of Maxwell's equations with the fluctuation-dissipation theorem to directly calculate the emissivity. The present study aims at unifying the direct and indirect methods for calculating thermal emission from layered structures with a nonuniform temperature distribution. Formulations for both methods are given to illustrate the equivalence between the indirect and the direct methods. Thermal emission from an asymmetric Fabry-Perot resonance cavity with a nonuniform temperature distribution is taken as an example to show how to predict the intensity, emissivity, and the brightness temperature. The local density of states, however, can only be calculated using the direct method.

Original languageEnglish (US)
Title of host publication2010 14th International Heat Transfer Conference, IHTC 14
Pages857-865
Number of pages9
DOIs
StatePublished - Dec 1 2010
Externally publishedYes
Event2010 14th International Heat Transfer Conference, IHTC 14 - Washington, DC, United States
Duration: Aug 8 2010Aug 13 2010

Publication series

Name2010 14th International Heat Transfer Conference, IHTC 14
Volume5

Other

Other2010 14th International Heat Transfer Conference, IHTC 14
CountryUnited States
CityWashington, DC
Period8/8/108/13/10

Keywords

  • Fluctuational electrodynamics
  • Generalized Kirchhoff's law
  • Multilayers
  • Thermal emission

ASJC Scopus subject areas

  • Fluid Flow and Transfer Processes

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  • Cite this

    Wang, L. P., Basu, S., & Zhang, Z. M. (2010). Direct and indirect methods for calculating thermal emission from layered structures with nonuniform temperatures. In 2010 14th International Heat Transfer Conference, IHTC 14 (pp. 857-865). (2010 14th International Heat Transfer Conference, IHTC 14; Vol. 5). https://doi.org/10.1115/IHTC14-22499