(a)
2
1
2
2
Gases
Gases
2
2
Gas
1
or coal
1
2
2
2
Gases
2
2
Gases
Gases
1
1
or coal
or coal
(b)
1
E bg
1
A 1 ε 1–g
A 2 ε 2–g
E b1
J 1
J 2
E b2
1 – ε 1
A 1 ε 1
1
A 1 F 12 (1 – α 1–2,g )
1 – ε 2
A 2 ε 2
–q 2
285
Radiation Transfer through Gases
If we consider energy balance between gases and enclosure surfaces i, the
heat transfer rate (energy releases) from gases to the enclosure is
N
N E bg J i
q g =
A i ε i,g (E bg
−
− J i ) =
(14.29)
1/A i ε i,g
i=1
i=1
However, we still need Equations 14.24 and 14.27 or Equation 14.28 to solve
J i using the matrix method. The aforementioned gas radiation problems can
also be solved by method 1—the electric network analogy method.
14.2.2 Electric Network Analogy
Special case 1: Figure 14.7a shows several combustion furnaces that can be
modeled as radiation between two surface enclosures containing hot radiation gases, if T g > T 1 > T 2 : By using Equations 14.24, 14.27, and 14.29, Figure
FIGURE 14.7
(a) Radiation between hot gases and two-surface enclosures; (b) Electric network for radiation
from hot gas to two-surface enclosure.