Exhaust temperature is the temperature of the exhaust gases in the nozzle, from the throat to the exit. The combustion temperature for liquid fueled rockets is typically around six thousand degrees Kelvin. The combustion temperature will be higher if the reaction releases a higher amount of energy, so a fuel reacting with liquid oxygen will reach a higher temperature than a fuel reacting with hydrogen peroxide. The combustion temperature will generally be higher if the exhaust has a higher molecular weight, if it is high in carbon dioxide for instance. The reaction of ethanol and hydrogen peroxide will reach a temperature of about three thousand nine hundred degrees Kelvin. The reaction of quadricyclene and oxygen react will reach a temperature of about seven thousand eight hundred degrees Kelvin.

The exhaust gases in the throat are a bit cooler than when they were in the combustion chamber, as some of their thermal energy was used to go supersonic in the throat. As the pressure ratio increases, the exhaust temperature ratio falls, as more of the exhaust's thermal energy becomes kinetic energy. The exhaust temperature at the nozzle exit will be about half that of the throat. The parts of the nozzle with high temperatures require liquid cooling. Often these are made of copper because of its high thermal conductivity. Given exhaust molar, k, nozzle efficiency, pressure ratio, product enthalpy and reactant enthalpy,exhaust temperature can be calculated.

k = 1.21
temperature change = ( reactant enthalpy - product enthalpy ) * ( 1.0 - 1.0 / k ) / 8,314 J * K / kmol / exhaust molar
expanded change ratio = ( 1.0 - pow( 1.0 / pressure ratio, ( k - 1 ) / k ) ) * nozzle efficiency * temperature change
exhaust temperature = temperature change - expanded change ratio + 298 K
 
 

This is used in bipropellant rocket, tripropellant rocket, pumped rocket and rocket cost.
 
 

Feedback   Free Electronic Nation Home    Rocket   GNU Free Documentation License