Carnot cycle efficiency reaches maximum limits for_____________________?
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Answer: E. reversible engine
Explanation
The Carnot efficiency represents the maximum theoretical limit for any heat engine operating between reservoirs. Only a fully reversible engine can achieve this ideal upper bound of performance. Irreversibilities like friction and heat loss always reduce real engine efficiency below this limit. Sadi Carnot formulated this principle using reversible isothermal and adiabatic processes. The second law of thermodynamics establishes that no engine can exceed Carnot efficiency. Reversibility requires zero friction and infinitesimal temperature gradients during heat transfer.
Engineers use Carnot efficiency as a benchmark to evaluate how well real engines perform. Power plant optimization focuses on minimizing internal irreversibilities to approach the limit. Theoretical thermodynamics relies on reversible cycles to define absolute temperature scales. Option A limits the cycle to gas engines, ignoring broader thermodynamic applicability. Option B focuses on lubrication, which reduces friction but cannot eliminate all irreversibilities. Option C specifies petrol engines, which operate on Otto cycles well below Carnot limits.
- Subject
- Engineering
- Category
- Mechanical Engineering
- Topic
- —
- Difficulty
- medium
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