SpectralEmissivity & Emittance

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What the Heck is (Spectral) Emissivity?

Part One of Two from the mind of FLIR
It health partners pharmacies starts:

Fill two soda cans with hot water and wrap one with scotch tape. Which one will radiate more heat?

You might be surprised at the answer

(It has all to do with Spectral Emissivity, although this video continues the illusion that it’s really simple “Emissivity” at work! The concept of Emissivity is simple and easy to grasp as the video shows. The understanding is a bit more difficult and begins when one realizes that it is really Spectral Emissivity.)

But looking beyond that technical fine point, the video illustrates two other things:Read More

ASTM E307 – 72(2008) Standard Test Method for Normal Spectral Emittance

At Elevated Temperatures
Developed by ASTM Subcommittee: E21.04, on Space Simulation Test Methods, and in the Annual Book of ASTM Standards, Volume 15.0 Space Simulation; Aerospace and Aircraft; Composite Materials

Quoting from the standard’s Scope:

1. Scope

1.1 This test method describes a highly accurate technique for measuring the normal spectral emittance of electrically conducting materials or materials with electrically conducting substrates, in the temperature range from 600 to 1400 K, and at wavelengths from 1 to 35 ?m.

1.2 The test method requires expensive equipment and rather elaborate precautions, but produces data that are accurate to within a few percent. It is suitable for research laboratories where the highest precision and accuracy are desired, but is not recommended for routine production or acceptance testing. However, because of its high accuracy this test method can be used as a referee method to be applied to production and acceptance testing in cases of dispute…

Obtaining directly from ASTM International has two options:

1. Buy Standard (PDF): 6 pages $ 37.00 US (In PDF format, this active standard is the most current version published by ASTM. You will download the file after you check out of the ASTM Store.)

2. Buy Standard (Print): 6 pages $ 37.00 US (In printed format, this active standard is the most current version published by ASTM. After you place your order, ASTM will print this standard and deliver it to your ship-to address by common carrier.)

Ordering Options Outside of the United State. has many more: Click here: (http://www.astm.org/IMAGES03/InterNatDist.pdf)

Table of Emissivities in Three Popular Spectral Regions

The Table of Emissivity on the INFRAPOINT Messtechnik GmbH website, posted in 2009 (No longer available online) had summary data for a wide variety of materials broken down into three distinct spectral regions for the wavelength regions where the majority of infrared radiation thermometers and Infrared Thermal Imaging cameras operate.

First and second are tables that deal with the narrow spectral bands about 0.9 µm and 1.6 µm, the regions where many Silicon (Si) photovoltaic detectors (peak wavelength response: (0.9 µm) and both Germanium (Ge) and Indium Gallium Arsenide (InGaAs) (nominal wavelength region (0.7 – 1.6 µm) are used.

The third table cover the 8 – 14 µm waveband where most “low” (near ambient) temperature IR thermometers and thermal imaging sensors operate.

It has been reproduced here below in the spirit of Internet openness from our archives. We hope there is no problem in doing so and if any heir or assigns of INFRAPOINT Messtechnik GmbH wishes to keep this information secret, obviously against the original intent of INFRAPOINT, please contact us according to our webpage contact information.


   Table of emissivity        
  The emissivity ? (radiant emittance factor) is the relationship of the radiated intensity of a body to the intensity of a blackbody of the same temperature.
It is the most important factor, in order to determine of an item exactly.

If you want to measure the surface temperature with an infrared thermometer the emissivity must be known and correct adjusted
on the instrument.

               
   Material  Emissivity     Material  Emissivity  
  Metals Wavelength
0.9 µm 
Wavelength
1.6 µm 
  Non metals Wavelength
8 – 14 µm  
 
               
  Aluminium, bright 0.05 – 0.25  0.05 – 0.25    Asphalt  0.95   
  Aluminium, anodized 0.2 – 0.4  0.1 – 0.4    Concrete 0.95  
  Chrom, bright 0.28 – 0.32  0.25 – 0.3    Gypsum 0.85 – 0.95   
  Iron, oxidised 0.4 – 0.8 0.5 – 0.9    Graphite  0.75 – 0.92   
  Iron, not oxidised 0.35 0.1 – 0.3    Glass*, pane  0.80   
  Gold, bright 0.02 0.02    Rubber 0.85 – 0.95   
  Copper, bright 0.06 – 0.20 0.06 – 0.20    Wood, natural 0.8 – 0.95   
  Copper, oxidised  0.5 – 0.8  0.7 – 0.85    Chalk 0.98   
  Magnesium 0.03 – 0.8  0.05 – 0.3    Ceramics 0.85 – 0.95   
  Brass, bright  0.8 – 0.95  0.01 – 0.05    Plastics 0.85 – 0.95   
  Brass, oxidised  0.65 – 0.75  0.65 – 0.75    Masonry 0.85 – 0.95   
  Nickel, oxidised  0.8 – 0.9  0.4 – 0.7    Human skin 0.98   
  Platinum, black  –  0,95    Oil paints 0.85 – 0.95   
  Silver  0.02  0.02    Paper  0.85 – 0.95   
  Steel, melted 0.30  0.20 – 0.25    Porcelain 0.85 – 0.95   
  Steel, oxidised  0.8 – 0.9  0.8 – 0.9    Quartz  0.8   
  Steel, bright 0.40 – 0.45  0.30 – 0.4    Carbon black 0.95   
  Titanium, bright 0.5 – 0.75  0.3 – 0.5    Chamotte  0.85 – 0.95   
  Titanium, oxidised  –  0.6 – 0.8    Textile, Drapery 0.85 – 0.95   
  Zinc, bright 0.6  0.4 – 0.6    Tone 0.95   
  Zinc, oxidised  0.5  0.05    Water 0.95  
  Tin 0.25  0.1 – 0.3    Cement  0.9   
* The emissivity of glass (0.95 – 0.97 µm) is in the range of 4.5 – 7 µm particularly high.
Glass has there an absorption band (spectral range, where materials absorb radiation).
To measure glass surface temperatures, the best wavelength is at 5.14 µm, because
the measurement at this range is not affected by absorption bands such as carbon or hydrogen.

Thermophysical properties and normal spectral emittance of Iridium up to 3500 K

“Thermophysical properties and normal spectral emittance of Iridium up to 3500 K”,

International Journal of Thermophysics Vol. 28(2), p. 697-710, http://dx.doi.org/10.1007/s10765-007-0188-9, (2007) by C. Cagran, G. Pottlacher

C. Cagran1 and G. Pottlacher1 Contact Information
(1) Institute of Experimental Physics, Graz University of Technology, Petersgasse 16, 8010 Graz, Austria

Published online: 10 May 2007
“An ohmic pulse-heating experiment together with radiometry and ?s-photopolarimetry is deployed at the Institute of Experimental Physics, Graz University of Technology, to obtain temperature-dependent thermophysical properties of conducting samples in the solid and molten states…”

“This experimental setup has been used within the present work to gather data for solid and liquid iridium. Results for both thermophysical properties, as well as the normal spectral emittance obtained at a wavelength of 684.5 nm up to 3500 K are reported. The newly obtained values for iridium are presented in graphical and tabular form and compared to available literature data. The uncertainties for all reported properties are stated and it follows that, considering these expanded uncertainties, the recent data are in very good agreement with literature sources. Mutually motivated by these good results and by the scarce (if any) data available for the liquid state, the thermal conductivity and thermal diffusivity of liquid iridium are estimated by means of the Wiedemann–Franz law.”

Keywords: ellipsometry – iridium – normal spectral emittance – pulse-heating – thermal conductivity – thermal diffusivity – thermophysical properties

STANDARDIZATION OF THERMAL EMITTANCE MEASUREMENTS. PART III.

NORMAL SPECTRAL EMITTANCE, 800-1400 K, Authors: Harrison, W.N. ; Richmond, J.C. ; Skramstad, H.K.

From the Energy Citations Database, OSTI IdentifierOSTI ID: 4830164

Technical Report, WADC-TR-59-510(Pt.III), National Bureau of Standards, Washington, D.C.,1961 Sep 01

ABSTRACT:

The equipment for direct measurement of normal spectral emittance was extensively modified by incorporation of a new external optical system that increased the amount of radiant energy available for measurement by a factor of about 10, and other associated changes. The test procedure was modified by incorporation of a zero line” correction. The equipment was calibrated by means of sector-disk attenuators which passed known fractions of the radiant flux from a blackbody furnace. Working standards of normal spectral emittance were prepared, calibrated, and shipped. An equation relating the normal spectral emissivity of a metal to five other parameters of the metal, each of which makes a non-linear contribution to the emissivity, was solved for one set of data by long hand” methods. Some progress was made in setting up a program for solution of the equation by use of an electronic computer. Equipment for the automatic recording of spectral emittance data in a form suitable for direct entry into an electronic computer, and on-line computation from spectral emittance data of total emittance or solar absorptance, was designed. Specifications for the equipment were prepared and bids received preparatory to placing an order for its procurement. (auth)