Why Is Carnot Efficiency Maximum?

Under what conditions an ideal Carnot engine has 100 efficiency?

and { T }_{ 1 } = temperature of sink source.

So n = 1 or 100%, { T }_{ 2 } = 0 K or heat is rejected into a sink at 0 K temperature..

Why can a Carnot engine not get 100% efficiency?

In order to achieve 100% efficiency (η=1), Q2 must be equal to 0 which means that all the heat form the source is converted to work. The temperature of sink means a negative temperature on the absolute scale at which the temperature is greater than unity.

Why the actual thermal efficiency is always less than the Carnot efficiency?

So if all the heat input was converted to useful work, the engine would have an efficiency of one (100% efficient). Thus, the efficiency is always less than one. Carnot showed that the maximum efficiency of a heat engine depends only on the temperatures between which the engine operates, not on the type of engine.

How do you increase Carnot efficiency?

From the Carnot Efficiency formula, it can be inferred that a maximum of 64% of the fuel energy can go to generation. To make the Carnot efficiency as high as possible, either Thot should be increased or Tcold (temperature of heat rejection) should be decreased.

Why is 100 Efficiency impossible?

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.

Why Carnot cycle is not possible?

Carnot cycles are not encountered in reality since achieving isothermal heat transfer is very difficult (needs very large heat exchangers and long time). Also process 3-4 requires a pump or compressor that can handle two phase mixture (liquid and vapor) which is impractical.

Which engine is most efficient?

The electric engine is most efficient. Electric motors are very efficient at converting electricity into work. Physicists throw around abstract numbers like 90%, whereas when discussing combustion engines, they use numbers less than 40%.

What is Carnot efficiency?

Carnot efficiency is the maximum efficiency that a heat engine may have operating between the two temperatures (Figure 2-7). Figure 2-7. Carnot process efficiency. The Carnot efficiency has little practical value. It is a maximum theoretical efficiency of a hypothetical engine.

Is Carnot engine 100 efficient?

A Carnot engine operating between two given temperatures has the greatest possible efficiency of any heat engine operating between these two temperatures. Furthermore, all engines employing only reversible processes have this same maximum efficiency when operating between the same given temperatures.

What happens when a Carnot cycle is run in reverse?

In the reverse Carnot cycle, work is done to extract heat from one system and expel it into another via four processes, two isothermal and two isentropic . In process 1→2, the gas is isentropically compressed, and there is no heat flow into or out of the refrigerator. … Heat transfer at this stage is zero.

Do all reversible engines have the same efficiency?

Reversible engines 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.

Why is the Carnot engine the most efficient?

The Carnot cycle can be thought of as the most efficient heat engine cycle allowed by physical laws. … This means that the Carnot cycle is an idealization, since no real engine processes are reversible and all real physical processes involve some increase in entropy.

Is Carnot engine possible?

A Carnot engine has to be perfectly reversible. This means zero friction, and perfect thermal conductivity between reservoirs*. In practice neither of these things are possible so you will only ever get “close”. As Floris points out the Carnot engine has to be perfectly reversible.

Can a perfectly 100% efficient system ever be created?

No. A system can never be 100% efficient. The reason behind this is because of heat and sound energy are lost in some amount in every system.

How is Carnot cycle calculated?

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 is the most efficient cycle?

Classical thermodynamics indicates that the most efficient thermodynamic cycle operating between two heat reservoirs is the Carnot engine [1] , and a basic theorem expresses that any reversible cycle working between two constant temperature levels should have the same efficiency as a Carnot cycle [2].

Which cycle has highest efficiency?

Explanation: Otto cycle is more efficient than Diesel cycle for a given compression ratio. 6. For constant maximum pressure and heat input, the air standard efficiency of gas power cycle is in the order.

Is Carnot a cycle?

The Carnot cycle is a theoretical ideal thermodynamic cycle proposed by French physicist Sadi Carnot in 1824 and expanded upon by others in the 1830s and 1840s. … It is not an actual thermodynamic cycle but is a theoretical construct. Every single thermodynamic system exists in a particular state.

Why are heat engines so terribly inefficient?

But yes, heat engines are generally quite inefficient. Ultimately, it’s because heat itself is a fairly inaccessible form of energy. … Doing that removes energy from the gas so it cools and loses pressure. By repeating the compression of a hot gas and extracting energy using a piston, we can get continuous work.

What is Carnot cycle in physics?

Carnot cycle, in heat engines, ideal cyclical sequence of changes of pressures and temperatures of a fluid, such as a gas used in an engine, conceived early in the 19th century by the French engineer Sadi Carnot. It is used as a standard of performance of all heat engines operating between a high and a low temperature.

Can you design an engine of 100% efficiency justify your answer?

Or, it is not possible to design a heat engine that has an efficiency of 1.00 or 100%. The efficiency of a heat engine can be 100% only if all the heat energy gets converted into work (or mechanical energy). … In other words, it will never be possible to design a heat engine having 100 per cent efficiency.