The jet-engine demonstrates thermal energy conversion

 

1. In the combustion chamber, pressurized air and fuel burn and generate very hot exhaust
gas (about 1800 Kelvin), which flows at low speed (about 40 meters/second) toward the chamber exit. The hot gas accelerates toward the combustion chamber exit while becomes colder ( 1200 Kelvin; about and bout 775 meters/sec).  This gas acceleration is according to Bernoulli's energy conservation law.