
334 Heat Transfer: Thermal Management of Electronics
The solar irradiation absorbed by a surface with the solar absorptivity α
s
is
(13.51)
Table 13.2 gives the solar absorptivity and the surface emissivity of some common
surfaces [5]. It is seen that, for most surfaces, α
s
≠ ε and that is expected since the
sun’s apparent temperature is signicantly higher than the room temperature and
Kirchhoff’s law does not apply. A quick observation of Table 13.2 shows that white
paint has very low solar absorptivity and very high surface emissivity. Therefore,
white and other light colors are the best candidates for the external