Which one of the following statements is correct?a)Efficiency of the C...
Carnot cycle has highestefficiency but very high back. So work ratio is low.
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Which one of the following statements is correct?a)Efficiency of the C...
Answer:
The Carnot cycle and the Rankine cycle are both idealized thermodynamic cycles used to analyze and compare the performance of thermal power plants. Each cycle has its own advantages and disadvantages in terms of efficiency and work ratio.
1. Carnot Cycle:
- The Carnot cycle is the most efficient cycle for a heat engine operating between two temperature limits.
- The cycle consists of four processes: isothermal heat addition, adiabatic expansion, isothermal heat rejection, and adiabatic compression.
- In the Carnot cycle, the working fluid operates in a closed loop, transferring heat to and from the surroundings through isothermal processes.
- The efficiency of the Carnot cycle is given by the formula: Efficiency = 1 - (Tc/Th), where Tc is the temperature at which heat is rejected and Th is the temperature at which heat is added.
- The Carnot cycle has a high theoretical efficiency, but it requires an idealized heat engine and is difficult to achieve in practice.
2. Rankine Cycle:
- The Rankine cycle is commonly used in thermal power plants as it closely resembles the actual steam power cycle.
- The cycle consists of four processes: heat addition, expansion, heat rejection, and compression.
- In the Rankine cycle, water is used as the working fluid and undergoes phase change from liquid to vapor and vice versa.
- The efficiency of the Rankine cycle is lower than the Carnot cycle due to irreversibilities such as friction and heat losses.
- The work ratio of the Rankine cycle is the ratio of net work output to the heat input. It represents the efficiency of converting heat into work.
- The Rankine cycle has a lower efficiency compared to the Carnot cycle, but it is more practical and achievable in real-world applications.
Comparison:
- Option B states that the efficiency of the Carnot cycle is high and the work ratio is low compared to the Rankine cycle. This statement is correct.
- The Carnot cycle has a higher efficiency than the Rankine cycle because it operates between two temperature limits, while the Rankine cycle operates over a range of temperatures.
- However, the work ratio of the Carnot cycle is lower than the Rankine cycle because the Carnot cycle requires an idealized heat engine, which is difficult to achieve in practice.
- Therefore, option B accurately describes the performance characteristics of the Carnot and Rankine cycles.
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