Heat engine is a device, which converts heat energy into mechanical work. The miechanical energy of fuel is converted into heat energy by combustion of fuel to produce
work of expansion. Heat engine can be represented as in figure 1.1.
Qa = Heat absorbed from heat source.
Qr = Heat rejected to heat sink.
W = Work output of engine.
EFFICIENCY = work output/heat input
this is known as theoretical or ideal thermal efficiency as it doesnot take into account any practical losses which do occour while actual runing of the engine. this is known as heat engine.