Assertion (A): Rankine efficiency would approach Carnot cycle efficien...
-Regeneration improves the cycle efficiency by increasing the initial feed water temperature before the water, water enters the boiler and also helps in controlling the large the large flow rate of steam at the turbine exhaust.
- With regenerative feed heating, expansion through the turbine approaches an isentropic process.
Both the statements are individually true
View all questions of this test
Assertion (A): Rankine efficiency would approach Carnot cycle efficien...
Rankine Efficiency and Carnot Cycle Efficiency
Rankine efficiency is a measure of the efficiency of a Rankine cycle, which is a thermodynamic cycle used in steam power plants. The Rankine cycle consists of four processes: compression in a pump, heating in a boiler, expansion in a turbine, and cooling in a condenser. The Rankine efficiency is defined as the ratio of the net work output of the cycle to the heat input.
Carnot cycle efficiency, on the other hand, is the maximum possible efficiency for any heat engine operating between two temperature extremes. It is given by the formula:
Efficiency = 1 - (Tc/Th)
where Tc is the absolute temperature of the cold reservoir and Th is the absolute temperature of the hot reservoir.
Regenerative Feed Heating
Regenerative feed heating is a technique used in steam power plants to improve the efficiency of the Rankine cycle. In this technique, some of the steam leaving the turbine is extracted and used to heat the feedwater before it enters the boiler. This preheating of the feedwater reduces the amount of heat required in the boiler, thereby improving the overall efficiency of the cycle.
Assertion (A): Rankine efficiency would approach Carnot cycle efficiency by providing a series of regenerative feed heating.
This assertion is true. By using regenerative feed heating, the temperature of the feedwater entering the boiler is increased, which reduces the temperature difference between the hot reservoir (boiler) and the cold reservoir (condenser). As a result, the Carnot cycle efficiency increases, and the Rankine efficiency approaches the Carnot cycle efficiency.
Reason (R): With regenerative feed heating, expansion through the turbine approaches an isentropic process.
This reason is also true. In the Rankine cycle, expansion through the turbine is not an isentropic process due to the presence of irreversibilities such as friction and heat transfer. However, with regenerative feed heating, the temperature of the steam entering the turbine is increased, which reduces the temperature drop across the turbine. This reduction in temperature drop leads to a closer approximation of an isentropic process, improving the overall efficiency of the cycle.
Conclusion
Both the assertion and the reason are individually true, and the reason is the correct explanation of the assertion. Regenerative feed heating in the Rankine cycle improves the efficiency by reducing the temperature difference between the hot and cold reservoirs, and it also approaches an isentropic process in the turbine. Therefore, option B is the correct answer.
To make sure you are not studying endlessly, EduRev has designed Mechanical Engineering study material, with Structured Courses, Videos, & Test Series. Plus get personalized analysis, doubt solving and improvement plans to achieve a great score in Mechanical Engineering.