Questions tagged [carnot-cycle]

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Why a reversible engine's efficiency must be equal to that of a Carnot engine

Apparently, in order to prove that an engine must be as efficient as a Carnot engine if reversible is because apparently for its efficiency in either direction: $\eta_E \le (1-T_2/T_1)$ $\eta_R \ge (...
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Example of a Carnot machine made of a different physical system than a ideal gas?

Anybody knows an example of a Carnot machine made with any different thing than a gas? For example wire or a magnet. I was wondering that since I read the Kardar's book on Statistical Mechanics. He ...
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About the 2nd Carnot Corollary

I have a question about the 2nd Carnot Corollary. According to Moran, Fundamentals of Engineering Thermodynamics, the 2nd Carnot Corollary stated that "all reversible power cycles operating between ...
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Irreversible heat engines strictly less efficient than reversible ones

I understand how Carnot's theorem implies that irreversible heat engines must be no more efficient than reversible one's, but it is less clear why they need to be less efficient, as I have seen stated ...
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Plotting isothermals and adiabats

first time poster in this site. I am trying to create a small program to make a graph of the Carnot cycle. For isothermals I am simply trying to look for points where P*V would give the same ...
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Validity of Carnot's theorem when operating between finite reservoirs

Carnot’s theorem tells us that "the most efficient heat engines operating between 2 reservoirs have the same efficiency as a Carnot engine". This theorem assumes that the engines are operating ...
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What does the ratio of reservoir temperatures have to do with the efficiency of a heat engine?

I am having a conceptual difficulty with heat engine efficiency. I do not understand why having a larger difference in temperature between the hot and cold reservoirs have an effect on the thermal ...
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Limitations of converting pressure into kinetic energy

Bernoulli's principle states that an increase in the kinetic energy of a fluid occurs simultaneously with a decrease in pressure for isentropic processes. What then limits us from converting all of ...
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How Much Heat Is Absorbed/Rejected By The Heat Engine?

If a heat engine undergoes a reversible cycle consisting of two isobaric processes and two adiabatic processes, what methodology is used to determine how much heat is absorbed or rejected by the heat ...
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Carnot cycle with varying reservoirs

I was thinking what will happen to the standard Carnot cycle, if instead of - say - the usual cold reservoir, we adopt a smaller refrigerator, whose temperature in fact changes after the heat release ...
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Confusion about forces in the work done on the piston by the gas in Carnot cycle

I was drawing a free body diagram of the 3rd step of the Carnot cycle as shown below. The forces with - sign are reaction forces to the forces without the sign, according to Newton's 3rd law of ...
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Is Carnot's theorem equivalent to the Second Law of Thermodynamics?

In thermodynamics we have Carnot's Theorem which states that the efficency of any heat engine wich works with only two temperature's source is less or equal to Carnot's engine which works between the ...
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A system with temp T is in contact with a reservoir of temp T. Would the system ever take in energy and expand (do work) in this situation?

The context is explain a Carnot cycle and how to get work from a system. Its starts by saying the system is in equilibrium with its surroundings, but then it take in some energy Qin. How does ...
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Is there any difference between heat and entropy here?

This screenshot is from the Carnot Cycle page on Wikipedia. In the "Stages" section, it says that: The gas expansion is propelled by absorption of heat energy, $Q_1$, and of entropy, $\Delta S=Q_1/...
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Efficiency of a Carnot machine, in which, some of its extreme points are in the region of liquid transition to steam

I need to calculate the efficiency of a Carnot machine, in which, some of its extreme points are in the region of liquid transition to steam with the works, differences of energy and heats of each ...
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Are there actual technical realizations of the Carnot cycle?

The Carnot cycle is composed of four steps: isothermal expansion, adiabatic expansion, isothermal compression and adiabatic compression. In the case of combustion engines, we have the idealized Otto ...
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Is there only one Carnot cycle for every thermodynamic system?

So, Carnot engine is THE reversible engine operating on two reservoirs. No other engine can beat its efficiency on two reservoirs (eg. Otto cycle is not Carnot as it requires infinite number of ...
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Confusion about Clausius inequality

I am trying to learn the derivation of Clausius inequality in the following manner. Consider the following diagram "Reversible cyclic device" is working in Carnot's cycle. The combined system gets ...
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Carnot cycle in steam processes

Our professor told us that in steam processes, such as Clausis-Rankine process, Carnot's cycle is impossible to achieve. Can someone explain why?
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Carnot cycle's paradox

Carnot cycle is a reversible cycle. By definition a reversible cycle must have an infinitesimal temperature difference. That means ($T_{high}-T_{low}$) is very very small. Any finite temperature ...
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Entropy change in a reversible carnot cycle with 2 beakers

Consider 2 beakers each containing 1kg of water. One beaker has initial temperature of 25 degrees celsius and the other at 100 degrees celsius. The beaker are now mixed. Assuming no heat exchanged is ...
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Cascade Carnot cycle

In a Carnot cycle about 50% of the energy is converted in work whereas the other is dissipated in heat to the heat sources. Is it possible to reuse the heat in another cycle to reconvert 50% of it ...
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Efficiency of a thermodynamic cycle

We are given a thermodynamic cycle of an ideal gas (but of rigid spheres) composed of a single substance which undergoes a Carnot cycle illustrated below. All processes are assumed to be reversible. ...
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Müser engine and solar conversion efficiency

I found in many reference a derivation of the maximal conversion efficiency from solar power to work with the so-called that I found dubious (see for instance here). It usually goes like this. Let us ...