MEC3454 Thermodynamics and Heat Transfer

Tutorial 8 – Heat exchangers and radiation

Q4. The spectral emissive power of black body is governed by the Planck distribution:

Eb , , T =C1

−5

eC 2/ T−1First radiation constant C1=2hc0

2=3.742×108W m4

/m2

Second radiation constant C2=hc0/k=1.4387×104m K

For a given temperature we may calculate the wavelength of maximum emissive power by differentiating Eh,λ with respect to λ. Do this to establish Wien's law: maxT=C3

where λmax is the wavelength corresponding to the maximum in Planck curves and the third radiation constant C3 =2898 μm K.