Flame temperature, actual maximum

The emissive power of a fireball, however, will depend on the actual distribution of flame temperatures, partial pressure of combustion products, geometry of the combustion zone, and absorption of radiation in the fireball itself. The emissive power ( ) is therefore lower than the maximum emissive power (E ) of the black body radiation ... 

Adiabatic Reaction Temperature (T ). The concept of adiabatic or theoretical reaction temperature (T j) plays an important role in the design of chemical reactors, gas furnaces, and other process equipment to handle highly exothermic reactions such as combustion. T is defined as the final temperature attained by the reaction mixture at the completion of a chemical reaction carried out under adiabatic conditions in a closed system at constant pressure. Theoretically, this is the maximum temperature achieved by the products when stoichiometric quantities of reactants are completely converted into products in an adiabatic reactor. In general, T is a function of the initial temperature (T) of the reactants and their relative amounts as well as the presence of any nonreactive (inert) materials. T is also dependent on the extent of completion of the reaction. In actual experiments, it is very unlikely that the theoretical maximum values of T can be realized, but the calculated results do provide an idealized basis for comparison of the thermal effects resulting from exothermic reactions. Lower feed temperatures (T), presence of inerts and excess reactants, and incomplete conversion tend to reduce the value of T. The term theoretical or adiabatic flame temperature (T,, ) is preferred over T in dealing exclusively with the combustion of fuels. 

Deflagration Pressure The increase in pressure in a vessel from a deflagration results from an increase in temperature the actual maximum flame temperature for propane, for example, is 1925°C (3497°F). No significant increase in moles of gas to cause pressure buildiip results from combustion of propane in air. 

Table I lists the flame variables employed and the measured maximum flame temperatures without correcting for radiation losses. The latter depend on the actual flame temperatures, the reactant flowrates and the flame configurations. For the flame using air as oxidant (air flame), the radiation losses are 45 160 C under the present...

Maximum flame temperature (Tm) is the maximum temperature reached in the actual configuration, i.e., under conditions that are not adiabatic. 

Equation (3.49) will provide an exact answer if the final temperature and molecular weight are known and the gas obeys the ideal gas law. If the final temperature is not known, then the adiabatic flame temperature can be used to provide a theoretical upper limit to the maximum pressure. Equation (3.49) predicts a maximum pressure usually much higher than the actual pressure—experimental determination is always recommended. 

This may not be the case if T, the ignition temperature, coincides with the inflection point in the temperature curve where dTIdx has a maximum. Not much violence is due in this case by moving the boundary toward a more symmetrical position, the distances all being relatively small. Actually, it seems likely that the gradient of temperature is nearly constant across the flame zone. 

---