The Carnot efficiency dictates that higher efficiencies can be attained by increasing the temperature of the steam.Carnot cycle is a theoretical cycle with the highest possible efficiency of all thermodynamic cycles.The area bounded by the complete cycle path represents the total work that can be done during one cycle.
So the second law is directly relevant for many important practical problems. In short, this principle states that the efficiency of a thermodynamic cycle depends solely on the difference between the hot and cold temperature reservoirs. A system undergoing a Carnot cycle is called a Carnot heat engine. It is not an actual thermodynamic cycle but is a theoretical construct and cannot be built in practice. They are not done infinitely slowly and infinitesimally small steps in temperature are also a theoretical fiction. Therefore, heat engines must have lower efficiencies than limits on their efficiency due to the inherent irreversibility of the heat engine cycle they use. The surroundings do work on the gas, increasing its internal energy and compressing it. The gas expands isothermally while receiving energy Q H from the hot reservoir by heat transfer. The temperature of the gas does not change during the process. The gas does work on the surroundings and loses an amount of internal energy equal to the work that leaves the system. The gas compresses isothermally to its initial state while it discharges energy Q C to the cold reservoir by heat transfer. It means the isentropic process is a special case of an adiabatic process in which there is no transfer of heat or matter. The assumption of no heat transfer is very important, since we can use the adiabatic approximation only in very rapid processes. Note that, this ratio c p c v is a factor in determining the speed of sound in a gas and other adiabatic processes. The heat transfer into or out of the system typically must happen at such a slow rate in order to continually adjust to the temperature of the reservoir through heat exchange. In each of these states the thermal equilibrium is maintained. The area under the Ts curve of a process is the heat transferred to the system during that process. For reversible (ideal) processes, the area under the T-s curve of a process is the heat transferred to the system during that process. For this type of power plant the maximum (ideal) efficiency will be. These processes cannot be achieved in real cycles of power plants.
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