Heat transfer evaluation
Glazing with reinforced thermal insulation

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 to the emissivity measured in the direction normal to the surface. For glass products, it...