Optical depth effects on aluminum oxide spectral emissivity

Joseph Kalman, David Allen, Nick G Glumac, Herman Krier

Research output: Contribution to journalArticle

Abstract

Measurements of high-temperature spectral emissivities of aluminum oxide were made within a heterogeneous shock tube over the spectral range of 650-900 nm. The spectral emissivity of optically thin micrometer-scale alumina particles scaled approximately as λ-1.4 from 2800 to 3500 K. Results from optically thin clouds of nanoscale alumina showed that a λ-1.2 dependence, closertothe λ-1 predictedby the Rayleigh limit, is appropriate over the same spectral and temperature ranges. For temperatures below the melting point of alumina, the emissivity of nanoalumina shows a significant temperature dependence. The effect multiple scattering has on the apparent emissivity is studied, and it is determined to contribute to the discrepancy between the current and previous works. A Monte Carlo simulation showed qualitative agreement with the experimental work. It was found that, at small to moderate optical depths, scattering is responsible for a small change in the spectral distribution of particle emissivity. At large optical depths, absorption has a much stronger effect on the apparent spectral emissivity. It was determined that choice of optical depth can strongly affect the results of pyrometry measurements.

Original languageEnglish (US)
Pages (from-to)74-82
Number of pages9
JournalJournal of thermophysics and heat transfer
Volume29
Issue number1
DOIs
StatePublished - Jan 1 2015

Fingerprint

emissivity
optical thickness
aluminum oxides
shock tubes
scattering
melting points
temperature measurement
micrometers
temperature dependence
temperature
simulation

ASJC Scopus subject areas

  • Condensed Matter Physics
  • Aerospace Engineering
  • Mechanical Engineering
  • Fluid Flow and Transfer Processes
  • Space and Planetary Science

Cite this

Optical depth effects on aluminum oxide spectral emissivity. / Kalman, Joseph; Allen, David; Glumac, Nick G; Krier, Herman.

In: Journal of thermophysics and heat transfer, Vol. 29, No. 1, 01.01.2015, p. 74-82.

Research output: Contribution to journalArticle

@article{acbd01dd7dfe4083b4cc1b2fab80d199,
title = "Optical depth effects on aluminum oxide spectral emissivity",
abstract = "Measurements of high-temperature spectral emissivities of aluminum oxide were made within a heterogeneous shock tube over the spectral range of 650-900 nm. The spectral emissivity of optically thin micrometer-scale alumina particles scaled approximately as λ-1.4 from 2800 to 3500 K. Results from optically thin clouds of nanoscale alumina showed that a λ-1.2 dependence, closertothe λ-1 predictedby the Rayleigh limit, is appropriate over the same spectral and temperature ranges. For temperatures below the melting point of alumina, the emissivity of nanoalumina shows a significant temperature dependence. The effect multiple scattering has on the apparent emissivity is studied, and it is determined to contribute to the discrepancy between the current and previous works. A Monte Carlo simulation showed qualitative agreement with the experimental work. It was found that, at small to moderate optical depths, scattering is responsible for a small change in the spectral distribution of particle emissivity. At large optical depths, absorption has a much stronger effect on the apparent spectral emissivity. It was determined that choice of optical depth can strongly affect the results of pyrometry measurements.",
author = "Joseph Kalman and David Allen and Glumac, {Nick G} and Herman Krier",
year = "2015",
month = "1",
day = "1",
doi = "10.2514/1.T4260",
language = "English (US)",
volume = "29",
pages = "74--82",
journal = "Journal of Thermophysics and Heat Transfer",
issn = "0887-8722",
publisher = "American Institute of Aeronautics and Astronautics Inc. (AIAA)",
number = "1",

}

TY - JOUR

T1 - Optical depth effects on aluminum oxide spectral emissivity

AU - Kalman, Joseph

AU - Allen, David

AU - Glumac, Nick G

AU - Krier, Herman

PY - 2015/1/1

Y1 - 2015/1/1

N2 - Measurements of high-temperature spectral emissivities of aluminum oxide were made within a heterogeneous shock tube over the spectral range of 650-900 nm. The spectral emissivity of optically thin micrometer-scale alumina particles scaled approximately as λ-1.4 from 2800 to 3500 K. Results from optically thin clouds of nanoscale alumina showed that a λ-1.2 dependence, closertothe λ-1 predictedby the Rayleigh limit, is appropriate over the same spectral and temperature ranges. For temperatures below the melting point of alumina, the emissivity of nanoalumina shows a significant temperature dependence. The effect multiple scattering has on the apparent emissivity is studied, and it is determined to contribute to the discrepancy between the current and previous works. A Monte Carlo simulation showed qualitative agreement with the experimental work. It was found that, at small to moderate optical depths, scattering is responsible for a small change in the spectral distribution of particle emissivity. At large optical depths, absorption has a much stronger effect on the apparent spectral emissivity. It was determined that choice of optical depth can strongly affect the results of pyrometry measurements.

AB - Measurements of high-temperature spectral emissivities of aluminum oxide were made within a heterogeneous shock tube over the spectral range of 650-900 nm. The spectral emissivity of optically thin micrometer-scale alumina particles scaled approximately as λ-1.4 from 2800 to 3500 K. Results from optically thin clouds of nanoscale alumina showed that a λ-1.2 dependence, closertothe λ-1 predictedby the Rayleigh limit, is appropriate over the same spectral and temperature ranges. For temperatures below the melting point of alumina, the emissivity of nanoalumina shows a significant temperature dependence. The effect multiple scattering has on the apparent emissivity is studied, and it is determined to contribute to the discrepancy between the current and previous works. A Monte Carlo simulation showed qualitative agreement with the experimental work. It was found that, at small to moderate optical depths, scattering is responsible for a small change in the spectral distribution of particle emissivity. At large optical depths, absorption has a much stronger effect on the apparent spectral emissivity. It was determined that choice of optical depth can strongly affect the results of pyrometry measurements.

UR - http://www.scopus.com/inward/record.url?scp=84922457783&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=84922457783&partnerID=8YFLogxK

U2 - 10.2514/1.T4260

DO - 10.2514/1.T4260

M3 - Article

AN - SCOPUS:84922457783

VL - 29

SP - 74

EP - 82

JO - Journal of Thermophysics and Heat Transfer

JF - Journal of Thermophysics and Heat Transfer

SN - 0887-8722

IS - 1

ER -