Carnot Efficiency
Carnot Efficiency
No heat engine can beat the Carnot efficiency set purely by its hot and cold reservoir temperatures — the upper bound every real cycle is measured against.
The Carnot efficiency is η = 1 − T_c/T_h. where T_c and T_h are the cold and hot absolute temperatures.
Inputs
T_c := 300 K=300 K
T_h := 800 K=800 K
Efficiency depends only on the temperature ratio.
eta := 1 - T_c/T_h=0.62
Results
Real engines reach only a fraction of this ideal because of friction and irreversibility. A higher hot temperature or lower cold temperature raises the ceiling.
Assumptions & limitations
- Reversible (ideal) cycle.
- Absolute temperatures.
- Two fixed-temperature reservoirs.