The efficiency of an irreversible heat engine is always less than the efficiency of a reversible one operating between same two thermal reservoirs. ... The efficiencies of all reversible heat engines operating between the same two thermal reservoirs are the same.
Are reversible engines more efficient?
All reversible engines have the same efficiency , or one could drive the other to move more heat in the reverse direction. Also, no engine has an efficiency greater than a Carnot engine. Finally, a Carnot engine is reversible.
Why efficiency of reversible engine is maximum?
Every reversible heat engine operating between the same two temperature reservoirs have identical efficiency . This means no matter how a reversible heat engine is constructed or what the working fluid is, its efficiency is the same as all other heat engines working from the same two temperatures.
Why all reversible engines have the same efficiency?
This violates second law of thermodynamics. Hence the assumption we made that reversible engine EA having higher efficiency than the reversible engine EB is wrong. ... Hence it is concluded that reversible engines working between same temperature limits have the same efficiency .
Why is a reversible process more efficient?
Reversible processes do the most work, because they have to push against more external pressure . Since w = -PΔV, a greater value for the external pressure (P) results in a higher (more negative) work.
Is Carnot engine 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. This time, the cycle remains exactly the same except that the directions of any heat and work interactions are reversed.
Is irreversible engines have maximum efficiency?
All the reversible and irreversible engines have the same efficiency . Irreversible engines have maximum efficiency. All engines are designed as reversible in order to obtain maximum efficiency.
Is reversible heat engine possible?
This cycle is still known as Carnot’s cycle, but because it is defined to be a reversible cycle, no heat engine can ever be made to operate using it .
Why is Carnot cycle most efficient?
The Efficiency of Carnot’s Cycle
Practical engine cycles are irreversible and thus have inherently lower efficiency than the Carnot efficiency when operating at the same temperatures. ... The Carnot cycle achieves maximum efficiency because all the heat is added to the working fluid at the maximum temperature .
Does all reversible engines have same efficiency?
All reversible heat engines operating between the two given thermal reservoirs have the same efficiency . The efficiency of reversible heat engine does not depend on the working fluid, it depends only on the temperature of the reservoirs between which it operates.
Why is the reason that reversible processes is 100% efficient?
Reversible processes produce the maximum amount of work
If a process does work on the surroundings , you get more work out of the process if it is done slowly. This is because less heat is lost to the surroundings. So a reversible process (infinitely slow) does the maximum work.
What is the efficiency of a reversible process?
Reversible processes define the boundaries of how efficient heat engines can be in thermodynamics and engineering: a reversible process is one where no heat is lost from the system as “waste”, and the machine is thus as efficient as it can possibly be (see Carnot cycle).
What is the maximum efficiency of a heat engine?
Heat engines often operate at around 30% to 50% efficiency , due to practical limitations. It is impossible for heat engines to achieve 100% thermal efficiency () according to the Second law of thermodynamics.
Is isothermal process always reversible?
Isothermal expansion can surely be irreversible if you make it so. In fact, any process is usually at least a bit irreversible, and truly 100% reversible processes are impossible . ... Therefore, ΔU(T)=q+w=0 and thus ΔT=0 , an isothermal condition.
Is free expansion reversible?
Any expansion of a system in which the applied pressure is less than the system pressure can be called a free expansion. ... The free expansion of a gas is an irreversible process ; in principle, the temperature of a gas undergoing a free expansion is not a meaningful quantity.
Why reversible process is slow?
Because reversible processes are very slow , the system is always very nearly in equilibrium at all times. ... In that case all its state variables are well defined and uniform, and the state of the system can be represented on a plot of, for instance, pressure versus volume.
