
35Fundamentals
the exhaust gas temperature. As the exhaust temperature
increases, more energy is carried out of the combus-
tion system and less remains in the system. The avail-
able heat decreases to zero at the adiabatic equilibrium
ame temperature where no heat is lost from the gases.
Figure 2.17 shows that even at gas temperatures as high
as 3500°F (2200 K), the available heat of an O
2
/CH
4
sys-
tem is still as high as 60%. Figure 2.17 also shows that it
is usually not very economical to use air/CH
4
systems
for high- temperature heating and melting processes. At
an exhaust temperature of 2500°F (1600 K), the available
heat for the air/CH
4