1. Heat input QH = 3000 Joule and heat output QL = 1000 Joule. What is the efficiency of the heat engine?
Known :
Heat input (QH) = 3000 Joule
Heat output (QL) = 1000 Joule
Work done by the engine (W) = 3000 – 1000 = 2000 Joule
Wanted: Efficiency of the heat engine (e)
Solution :
[irp]
2. A heat engine produces 2000 Joule of mechanical work and the engine discharges heat to the environment at a rate of 500 Joule. What is the efficiency of the heat engine?
Known :
The work is done by the engine (W) = 2000 Joule
Heat output (QL) = 5000 Joule
Heat input (QH) = 2000 + 5000 = 7000 Joule
Wanted: Efficiency (e)
Solution :
[irp]
3. A heat engine has an efficiency of 30%. If the engine produces 10,000 Joule of mechanical work, how much heat is discharged as waste heat from this engine?
Known :
Efficiency (e) = 30 % = 30/100 = 0.3
The work is done by engine (W) = 3,000 Joule
Wanted : Heat output (QL)
Solution :
Heat output (QL) = heat input (QH) – work is done by engine (W)
QL = 10,000 Joule – 3,000 Joule
QL = 7,000 Joule