What variables affect the efficiency of a heat engine?
The thermal efficiency of a heat engine is expressed as a product of the Carnot efficiency, the external irreversibility factor and the internal irreversibility factor, by which the three factors that affect the thermal efficiency can be clearly distinguished, and the influences of the external and internal …
What are the two statements known as the Carnot principles?
Carnot principles can be expressed as the following two statements: 1. The efficiencies of all reversible heat engines operating between a constant temperature source (TH) and a constant temperature sink (TL) are the same. They only depend on the high temperature TH=const and the low temperature TL=const.
How do you find the efficiency of a Carnot cycle?
Practice
- Convert the high and low temperatures from Celsius to Kelvin: Thot=540oC+273=813K. Tcold=20oC+273=293K.
- Determine the efficiency using the Carnot efficiency formula: η=[1−TcoldThot]×100%η=[1−293K813K]×100%=64%
Why is Carnot efficiency maximum?
Since the limit on efficiency is based on the temperature difference between the heat source and whatever is used to cool the system — usually outside air or a supply of water — it is clear that the hotter the heat source, the higher the possible efficiency.
Why are engines not 100 efficient?
It is impossible for heat engines to achieve 100% thermal efficiency () according to the Second law of thermodynamics. This is impossible because some waste heat is always produced produced in a heat engine, shown in Figure 1 by the term.
Do all reversible cycles have same efficiency?
Therefore, both (reversible) heat engines have the same efficiency, and we conclude that: All reversible engines that operate between the same two heat reservoirs have the same efficiency.
Is Carnot cycle reversible?
The Carnot heat-engine cycle described is a totally reversible cycle. That is all the processes that compose it can be reversed, in which case it becomes the Carnot refrigeration cycle.
Why efficiency of reversible engine is maximum?
Answer : The engine, in which the process can be retraced at any stage of its operation by reversing the boundary conditions, is called a reversible heat engine. Its efficiency is maximum, as no dissipation of energy takes place against friction, etc in such a heat engine.
Which statement is incorrect all reversible cycles have same efficiency?
Solution : All reversible engines work for different values of temperature of source and sink hence the efficients of all such engines are different. The incorrect statement is all reversible cycles have same efficiency.
Which statement is incorrect 1 all reversible cycles have same efficiency 2 reversible cycle has more efficiency than an irreversible one 3 Carnot cycle is a reversible one 4 Carnot cycle has the maximum efficiency in all cycles?
Explanation: Efficiency of all reversible cycles depends upon temperature of source and sink which will be different. Rest of the statements are correct.
What is Carnot reversible engine?
The Carnot cycle is essentially a reversible cycle that itself consists of four reversible processes. A reversible process is a process that is carried out infinitely slow, so that the entire process can be through of as consisting of a series of equilibrium states.
What is the formula of Carnot engine?
W=QH−QC=(1−TCTH)QH. efficiency =WQH=1−TCTH. These temperatures are of course in degrees Kelvin, so for example the efficiency of a Carnot engine having a hot reservoir of boiling water and a cold reservoir ice cold water will be 1−(273/373)=0.27, just over a quarter of the heat energy is transformed into useful work.
Which gas is used in Carnot engine?
A diatomic ideal gas is used in a Carnot engine as the working substance. If during the adiabatic expansion part of the cycle the volume of the gas increase from V to 32V, the efficenecy of the engine is. Now, efficiency=1-T2T1=1-T24T2=1-14=34=0.75.
What is the importance of Carnot cycle?
The Carnot engine — or the Carnot cycle — is important because it describes a heat engine that uses reversible processes that can be handled theoretically. Then we could use the real heat engine to power a Carnot cycle heat pump.
What is an ideal process?
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Who invented Carnot cycle?
Sadi Carnot
How does a Carnot engine work?
Carnot Engine – Working and Efficiency. Carnot engine is a theoretical thermodynamic cycle proposed by Nicolas Léonard Sadi Carnot in 1824. Carnot states that a hot body is required that generates heat and a cold body to which the caloric is conveyed, which produces mechanical work in the process.