Page 239 - Mechanical Engineers' Handbook (Volume 4)

228 Furnaces

Figure 9 Thermodynamic properties of air and flue gas. 1

8.1 Solid-State Radiation
‘‘Blackbody’’ surfaces are those that absorb all radiation received, with zero reflection, and
exist only as limits approached by actual sources or receivers of solid radiation. Radiation
between black bodies is expressed by the Stefan-Boltzmann equation:
4
4
Q/A N(T T ) Btu/hr ft 2
0
where N is the Stefan-Boltzmann constant, now set at about 0.1713 10 8 for T and T ,
0
source and receiver temperatures, in R. Because the fourth powers of numbers representing