Modern Engineering Thermodynamics

15.9 Maximum Explosion Pressure 619
FIGURE 15.8
Accessing the details.
15.9 MAXIMUM EXPLOSION PRESSURE
The maximum possible internal pressure produced by combustion in a closed, rigid system is the pressure that
occurs at the adiabatic flame temperature. It is the pressure that occurs when the system is insulated or when
the combustion reaction occurs too fast for significant heat transfer to occur (as in explosions). This maximum
pressure can be estimated from the ideal gas equation of state as
Maximum explosion pressure:
p max
= n pRT A
(15.19)
explosion V p
where n p is the total number of moles of product present in the volume, V p , and T A is the adiabatic flame temperature
of the reaction. Even though the adiabatic flame temperature is never reached in practice, this value of
p max is useful as an upper bound in explosion safety calculations.
CRITICAL THINKING
At the SRS, nitroglycerin (C 3 H 5 O 9 N 3 ) is a highly unstable liquid that explodes 25 times faster and with 3 times the energy
of gunpowder. In 1867, Alfred Bernhard Nobel (1833–1896) found that clay soaked with nitroglycerin was much more
stable and less sensitive to shock than pure nitroglycerin. He called this safer form of nitroglycerin dynamite and manufactured
it and other explosives for many years. His company was very successful, and with some of the profits, he founded
the Nobel Prizes in physics, chemistry, literature, physiology or medicine, and peace. Would the maximum explosion pressure
of nitroglycerin be 25 times higher than the explosion pressure of an equal mass of gunpowder?