T2
T1
x
Gases
Tg(x)
1
T
o
y
q λ
I λ
I n cos θ θ
θ
τ
T 2
+
L
y
dw
ds
dy = ds cos θ
T1 > T2
289
Radiation Transfer through Gases
Air fuel
Surface zones
Gas zones
Air fuel
Surface zones
Gas zones
FIGURE 14.12
Concept of zone method for real furnace heat transfer problem.
Zone for gases T g,i = Number of gas zones, a uniform temperature in
each zone
Zone for surfaces T i = Number of surface zones, a uniform temperature
in each zone
The problem will be even more complicated if convection effects are considered, which is up to 20% of heat transfer rate for a circulation well-mixed
furnace. In reality, soot formation and radiation can further make the problem
harder to model.
14.3 Radiation Transfer through Gases with Nonuniform
Temperature
14.3.1 Cryogenic Thermal Insulation
In some applications, such as cryogenic thermal insulation, radiation heat
is transferred from surface 1 to surface 2 through participating gases with
varying temperature as shown in Figure 14.13. For a simple 1-D problem,
FIGURE 14.13
Radiation heat transfer through gases with varying temperature.