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2. Heat transfer evaluation
2.1 Emissivity measurement
The measurement of emissivity is based on Kirchhoff's law, and can be used to determine the radiating power of any body. All you need to do is measure or theoretically determine the absorption coefficient A (λ ).
For thermal radiation wavelengths (infrared from 3 to 50 µm), the absorption coefficient of a body can be measured using an infrared spectrometer. As we saw earlier, glass is opaque for wavelengths above 4.5 µm (T (λ ) = 0). In this case, we have :
The emissivity value most commonly used in Europe is the normal emissivity ε n . It corresponds...
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Heat transfer evaluation
Which glazing for enhanced thermal insulation?
References
Standardization
French Standards Association (Afnor)
- Glass in construction – Determining the luminous and solar characteristics of glazing. - NF EN 410 - 11-1999
- Glass in construction – Determination of thermal transmittance, U – Calculation method. - NF EN 673 - 5-2003
- Glass in construction – Determination of luminous transmittance,...
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