Heat-engine efficiency and Carnot bound
A cyclic heat engine drawing heat Q_h from a reservoir T_h and rejecting Q_c to T_c delivers W=Q_h−Q_c.
Key knowledge
A cyclic heat engine drawing heat Q_h from a reservoir T_h and rejecting Q_c to T_c delivers W=Q_h−Q_c. Its efficiency η=W/Q_h≤1−T_c/T_h; equality requires a reversible cycle with these two reservoirs.
Values and equations
W=Q_h−Q_c; η=W/Q_h≤1−T_c/T_h
- W,Q_h,Q_c
- Work delivered and heat magnitudes J
- T_h,T_c
- Hot/cold reservoir temperatures K
- η
- Dimensionless efficiency
Conditions and scope
- T_h>T_c>0 are absolute temperatures; positive heat magnitudes, a cyclic working body and no additional work/energy reservoirs.
- A refrigerator reverses heat pumping; its coefficient of performance is a different ratio. Real irreversibility lowers efficiency.
Sources · 1
References
Sources retain their recorded scope. A source link alone does not establish verification of every statement.
Evidence and review
Thermodynamics and Statistical Mechanics (2016): Heat engines: Equations 6.196–6.201: cyclic first-law balance, reservoir entropy and efficiency bound; excludes historical and numerical engineering generalizations.
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Entry details
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