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Handbook of OSML Libraries: Emittance

CRMHT – CNRS Centre de Recherche sur les Matériaux à Haute Température, Orléans, France
Mesure indirecte de l’émittance (Includes sample data for Silicon Dioxide)

Mesure de la réflectivité et de la transmissivité normales spectrales (10 à 40 000 cm-1 soit 1 000 à 0,25 µm).

L’émissivité normale spectrale se déduit indirectement par calcul de ces deux grandeurs par application des lois de Kirchhoff ,

i.e. at each wavelength, Emissivity =1 – Reflectivity – Transmissity

Emittance-WN Handbook of OSML Libraries
E – dielectric function
N – complex refractive index
RT – reflectivity, layer transmissivity
WN – wave number
OSML Source : [Emitttance-WN]
Function Group : [Optical Functions]
Emittance-E
Emittance-E (AE) represents the fraction of the incident radiation that is absorbed (Kirchhoff law) by a sample with a plate shape. Its expression take into account for multiple reflections (no interference effects) and depends on the dielectric functions of the incident medium Ei, those of the material Eo and the thickness d of the sample.
Function signature : Emittance-E(x,Ei,Eo,Thickness)Units


The spectral dependence must be expressed in wave numbers (cm-1) and the thickness in (cm).
Emittance-N
Emittance-N (AN) represents the fraction of the incident radiation that is absorbed (Kirchhoff law) by a sample with a plate shape. Its expression take into account for multiple reflections (no interference effects) and depends on the complex refractive indexes of the incident medium Ni, those of the material No and the thickness d of the sample.
Function signature : Emittance-N(x,Ni,No,Thickness)Units


The spectral dependence must be expressed in wave numbers (cm-1) and the thickness in (cm).
Emittance-RT
Emittance-RT (ART) represents the fraction of the incident radiation that is absorbed (Kirchhoff law) by a sample with a plate shape. Its expression take into account for multiple reflections (no interference effects and depends on the reflectivity R and the layer transmissivity T of the sample.
Function signature : Emittance-RT(R,T)
Planck-WN
Planck-WN (PWN) is the wave number version of the Planck function. Its expression depends on the temperature T.
Function signature : Planck-WN(x,T)
Constants : C1=1.1910 10-6 (W.m2) C2=1.4388 (cm.K)

See Also : [Optical Functions] [Reflectance-WN] [Transmittance-WN]

Handbook of OSML Libraries

Emissivity Calculator Online

The Pyrometer Instrument Company, manufacturers of the Pyrolaser® and Pyrofiber® products, among others, have a unique, online emissivity calculator that enables one to calculate the temperature measurement effect of: wavelength, emissivity setting and temperature for Infrared measurement wavelength bands ranging from 0.655 micrometer to 10.6 micrometers.

You can access the calculator by CLICKING HERE

(Pyrometer Instrument Company, 92 North Main Street • Bldg 18-D • Windsor, NJ 08561 • USA
Telephone: (609) 443-5522 • Fax: (609) 443-5590 • Email: sales [at] pyrometer.com)

EMISSIVITY EVALUATION OF FIXED POINT BLACKBODIES

A paper by Sergey Mekhontsev, Vladimir Khromchenko, Alexander Prokhorov, Leonard Hanssen
National Institute for Standards and Technology, Gaithersburg, MD, USA

Presented at the 9th International Symposium on Temperature and Thermal Measurements in Industry and Science (TEMPMEKO 2004), June 22-25, 2004, Dubrovnik, Croatia, Proceedings, Vol. 1, ed. by D. Zvizdic (2004), pp. 581-586.

ABSTRACT

A new facility for the characterization of infrared spectral emittance of materials has recently been developed at NIST. The facility operation is based on measurements of a sample’s spectral radiance and surface temperature with help of a set of variable temperature blackbodies and a spectral comparator. For highest accuracy, variable temperature blackbodies are calibrated in spectral radiance against a pair of fixed-point blackbodies with interchangeable crucibles of In, Sn, and Zn, and Al, Ag, and Cu, respectively. The spectral emissivity of the fixed-point blackbodies also needs to be accurately characterized. We employ a multi-prong approach: (1) Monte Carlo ray-trace modeling and calculations, (2) hemispherical reflectance measurements of the crucible cavity material flat sample, as well as the cavity itself, (3) direct spectral emittance measurements of the same samples using the facility, and (4) comparison of the fixed point blackbodies with each other as well as with variable temperature heat pipe blackbodies, using filter radiometers and the facility’s Fourier transform spectrometer. The Monte Carlo code is used to predict the cavity emissivity with input of the cavity shape and the emissivity and specularity of the cavity material. The reflectance measurements provide emissivity data of both the material and the cavity at room temperature. The results are used to compare with and validate the code results. The direct emittance measurements of the material provide the temperature dependence of the material emittance as code input. The code predicted results for the cavities at their operating temperature (freeze points) are then compared with the relative spectral radiance measurements. Use of this complete set of evaluation tools enables us to obtain the spectral emissivity of the blackbodies with reliably determined uncertainties.

It presently can be downloaded in PDF format from the NIST website by CLICKING HERE

IR spectral characterization of customer blackbody sources:

“First calibration results”

A paper by S. Mekhontsev, M. Noorma, A. Prokhorov, and L. Hanssen from NIST in the USA, Presented at Thermosense XXVIII, ed. by Jonathan J. Miles, G. Raymond Peacock, and Kathryn M. Knettel, Proc. of SPIE 6205, 620503 (2006).

ABSTRACT:

We summarize recent progress in our infrared (IR) spectral radiance metrology effort. In support of customer blackbody characterization, a realization of the spectral radiance scale has been undertaken in the temperature range of 232 °C to 962 °C and spectral range of 2.5 µm to 20 µm. We discuss the scale realization process that includes the use of Sn, Zn, Al and Ag fixed-point blackbodies (BB), as well as the transfer of the spectral radiance scale to transfer standard BBs based on water, Cs and Na heat pipes. Further we discuss the procedures for customer source calibration with several examples of the spectral radiance and emissivity measurements of secondary standard BB sources. For one of the BBs, a substantial deviation of emissivity values from the manufacturer specifications was found. Further plans include expansion of the adopted methodology for temperatures down to 15°C and building a dedicated facility for spectral characterization of IR radiation sources.

It presently can be downloaded from the NIST website in PDF format by CLICKING HERE

Prediction of the thermal radiative properties of an X-Ray µ-tomographied porous silica glass

Prediction of the thermal radiative properties of an X-Ray µ-tomographied porous silica glass
B.Rousseau, D.De Sousa Meneses, P.Echegut, M.Di Michiel, J.-F.Thovert
Prediction of the thermal radiative properties of an X-Ray µ-tomographied porous silica glass
Applied Optics 46 4266-4276, (2007)

ABSTRACT
“A Monte Carlo ray tracing procedure is proposed to simulate thermal optical processes in heterogeneous materials. It operates within a detailed 3D image of the material, and it can therefore be used to investigate the relationship between the microstructure, the constituent optical properties, and the macroscopic radiative behavior. The program is applied to porous silica glass. A sample was first characterized by 3D x-ray tomography; then, its normal spectral emittance was calculated and compared with the experimental spectrum measured independently by high-temperature infrared emittance spectroscopy. We conclude with a discussion of the light-scattering mechanisms occurring in the sample.”

Work performed at and reported by: Centre National de la Recherche Scientifique (CNRS), France.