Question: Consider an axisymmetric stagnation point on a missile traveling through the atmosphere at 5500mls where the static air temperature is near zero degrees absolute. It is desired to maintain the surface at 1200°C by transpiration of hydrogen through the wall. The hydrogen is available from a reservoir at 38°e. If the "heat of combustion" of hydrogen is approximately 116,000kJ/kg at 1200°C and the mean specific heats of hydrogen and air are, respectively, 15 kJ/(kg· K) and 1.1 kJ/(kg. K), evaluate the driving force B from the energy equation under the unit-Lewis-number assumption for the conditions of
(1) reaction of Hz with O2, and
(2) no reaction. Suggestion: Use the surface temperature as the temperature datum for enthalpy. Note that the free-stream enthalpy must include the very large contribution of the stagnation enthalpy.