A heat engine operates between a hot reservoir at 600K and a cold reservoir at 300K. In each cycle the engine absorbs 1.0kJ of energy from the hot reservoir.
Engine R is an ideal engine that operates reversibly between the two reservoirs.
Engine S follows the same intake and exhaust temperatures but the rapid combustion that drives its piston generates an additional 20JK−1 of entropy inside the working fluid during each cycle.
Assume both engines reject energy only to the cold reservoir and that no other energy transfers occur.
(1) Part 1: For Engine R, determine the heat expelled to the cold reservoir and the thermal efficiency of the engine.
(2) Part 2: For Engine S, determine the minimum possible amount of energy that must be expelled to the cold reservoir each cycle. Hence calculate its maximum possible thermal efficiency.
(3) Part 3: Explain, using the second law of thermodynamics, why Engine S cannot achieve the same efficiency as Engine R even though both operate between the same temperature limits.