
416 Heat Transfer: Thermal Management of Electronics
the calculated temperature depends on the accuracy with which the emissivity of the
surface is known. Equation 15.19 shows that the error in calculated temperature is
correlated to the error in surface emissivity by
(15.20)
This equation shows that the absolute error in the calculated temperature, ΔT, for a
given absolute error in the assumed surface emissivity, Δε, is smaller for surfaces
with higher emissivity values.
Radiation coming from a surface is not all emitted from that surface. It also
includes the reected part of the irradiation that is incident ...