All Questions
Tagged with reversibility carnot-cycle
40 questions
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Whats the lowest energy substance reaches during adiabatic expansion of carnot engine? [closed]
In carnot engine we know the steps like first isothermal, than adiabatic, then reverse isothermal and adiabatic.
And we know that efficiency increase if the temperature of hot box(heat supllier) is ...
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Confusion about reversibility of a carnot engine
I recently posted a question about entropy and the conversation changed topic to bring up an interesting question. @Chemomechanics explained that for a transformation to be reversible it is needed ...
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Why do we need an adiabatic expansion in the Carnot cycle? [duplicate]
As we know that 1st process is an reversible isothermal expansion during this the system is in quasi static equilibrium which helps in increasing the volume of the system but why does the second step ...
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Reversibility of the ideal Carnot cycle
How do adiabatic processes in the reversible Carnot cycle take place? Is the gas adiabatically isolated? If so, how would that happen in real life? (I know that Carnot cycle is not practically ...
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Please explain why the Carnot cycle is reversible while the Otto cycle is irreversible using the kelvin or clausius statement of the second law [closed]
why is the Carnot cycle reversible while the Otto cycle irreversible according to Kelvin-planck statement
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What is Entropy Balance Relative to (un)Compensated Heat of Clausius?
Consider the ideal Carnot cycle consisting of two ideal reversible isothermal stages at $T_0$ and $T_1$ and two ideal adiabatic reversible (isentropic) stages connecting them; assume that $T_0 > ...
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How can we say that work done by carnot engine in a cycle equals net heat released into it even when it is operated b/w 2 bodies and not 2 reservoir?
When a carnot engine is operated between 2 reservoir then after each cycle it return to its initial state so change in internal energy is zero and so work done by it equals net heat released into it. ...
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How does a reversible Carnot cycle transform heat to work?
To make clearer what I am asking let me introduce a new terminology to avoid any misunderstandings. Let the heat flow, which is rate, between a reservoir and an engine be denoted by $\mathfrak J$ and ...
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The Work Done by an Irreversible Carnot Cycle
This is a question from the book, Understanding Non-Equilibrium Thermodynamics by Lebon and Jou.
Show that the work performed by an engine during an irreversible cycle operating between two thermal ...
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Approximation of any reversible process by carnot cycle
While studying thermodynamics i came across the fact that any reversible cycle can be represented by series of miniature carnot cycles. I am unable to understand how can it be done for every cycle as ...
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Is $Q=TS$ valid for externally reversible process or internally reversible process?
For $q=tds$ is this equation valid for externally reversible process or internally reversible process? Like for example a heat transfer process in Rankine Cycle is internally reversible but not ...
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Is it always true that a non-adiabatic reversible process is an isothermal process?
In a Carnot Cycle, a reversible isothermal process is a non-adiabatic reversible process. Is it always true that a non-adiabatic reversible process is an isothermal process?
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Meaning of "Heat engine working between two Temperatures"
According to Carnot Theorem:
"Of all engines working between two given temperature, none is more efficient than a carnot engine."
I want to know what actually is meant by an engine working ...
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Carnot cycle total reversibility
I read the discussion of the same problem in another problem posted here Carnot Total Reversibility, but still I can't get the reason why Carnot cycle is stated as "Totally Reversible", it ...
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Proof for $\oint \frac{dQ}{T}=0 $ in a reversible process
I'm actually trying to prove that Entropy is a state function. I get struck at the point where I need to prove that $\oint \frac{dQ}{T}=0 $ for a reversible process.
Clausius in his book The ...
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The reversible Carnot cycle is the most efficient between $T_2$ and $T_1$. Is it a form the second law itself?
The second law of thermodynamics
proposed by Clausius, Kelvin, Carnot ..etc in its original form as T dS> dQ for irreversible process and Tds =dQ only for reversible thermodynamics process.
This ...
user248651
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Can the Efficiency of an Arbitrary Reversible Cycle be Equal to the Efficiency of the Enclosing Carnot Cycle?
I was reading the following article:
https://www.researchgate.net/publication/...
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Can anyone prove this overstated-but-almost-never-justified fact from thermodynamics?
Clausius inequality states that $\oint {\delta Q\over T}$ equals zero for a system undergoing a reversible cycle, whereas it can’t be greater than zero for an irreversible cycle.
But everywhere, I ...
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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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Deriving the second law of thermodynamics from an irreversible carnot process
I have studied the ideal carnot cycle extensively where we assume that
$$\Delta S_{\mathrm{total}}=\sum_i \frac{Q_i}{T_i} =0$$
Now I was wondering whether it is possible to derive basic properties ...
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Entropy generation in an engine
I'm trying to distinguish between maximum and minimum entropy generation by an engine, and ran into a conundrum.
The total entropy generation is found by applying an entropy balance to the red control ...
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Total Reversibility of Carnot Cycle
I was reading about Carnot cycle in "Thermodynamics by Cengel & Boles", now it is stated that Carnot cycle is a totally reversible cycle, i.e it is an internally as well as externally reversible ...
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Could a Carnot engine linked to a Carnot "refrigerator" create a perpetual heat flow between two reservoirs?
Here is a diagram of the system in question (adapted from the diagram on this page):
All of the work produced by the Carnot engine is used to drive the Carnot refrigerator, which is simply a Carnot ...
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Reversible and irreversible cycles: Changes in entropy of the system and the surrounding
Entropy is a state function.
Is it true that at the end of a cyclic process, the change in entropy of the of the system and that of its surrounding are both separately zero irrespective of whether ...
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Is there an implemented example of an almost reversible heat engine?
I'm reading Feynman's discussion of Reversible engines (Vol I 44.3) in The Feynman Lectures on Physics. His discussion is very abstract, and leaves a lot of practical questions unanswered. Rather ...
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How do we know that entropy is a state function given by $\delta Q_{\mathrm{rev}}/T$ for any arbitrary (not just reversible process)?
In this video, the professor goes through a "derivation" for entropy using the Carnot cycle, in which he establishes that entropy is a state function for that process.
However, he then continues the ...
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What makes a process reversible?
I just want someone to verify what I think.
I originally thought that for a reversible process to occur, no irreversibilities like friction can occur. Nevertheless, if we consider the Carnot ...
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Derive the Carnot Efficiency without using the Carnot Cycle? [closed]
How can you derive the Carnot efficiency using only properties of reversible cycles?
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Irreversible processes don't account in entropy calculations?
Pick a Carnot Cycle (being $T_1<T_2$), it is reversible, therefore $\Delta S_{univ, cycle}=0$.
The same result is obtained via the sum of all entropies associated with its transformation, which ...
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Is "entropy" not a state variable for irreversible process?
Any reversible process can be described as a sum of many infinitesimally small Carnot cycles, so $\oint {dS} = \oint {\frac{{dQ}}{T}} = 0
% MathType!MTEF!2!1!+-
% ...
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Difference between reversible and irreversible adiabatic process in PV diagram
let's say we've got a carnot-cycle in a pressure volume diagram with the following processes:
1 -> 2: reversible isothermal
2 -> 3: reversible adiabatic
3 -> 4: reversible isothermal
4 -> 1: ...
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Entropy and Clausius inequality
From the Clausius inequality we can derive that the efficiency of a Carnot (reversible) cycle is given by: $$e= 1 - \frac{T_c}{T_h}$$
Is this true for every reversible cycle? Is the efficiency of all ...
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Carnot engine basics?
A line in my textbook says.. ' if we employ any other process that is not adiabatic, say an isochoric process, to take the system from one temperature to another, we shall need a series of ...
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Why is entropy of system same for reversible and irreversible processes? [closed]
I read that entropy change of universe is zero in a reversible process but positive in a irreversible process,then doesn't it mean that entropy change of system of both the processes must be ...
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Reversibility and isothermal processes
I would like to know why any reversible process has to be isothermal, according to my sources.
Why can´t we consider adiabatic processes to be reversible?
EDITED
https://www.ohio.edu/mechanical/...
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Why is the net entropy change of an irreversible engine positive?
In a Carnot engine the net entropy changein a cycle is zero. But in an irreversible engine operating between two temperatures the net entropy change in a cycle is positive. As I have understood, this ...
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Entropy of loops in the PV plane
The change in entropy of the Carnot and reversible cycles is said to be 0. Several other loops are supposed to have a non-negative change in entropy.
This presents 2 problems which I cannot reconcile....
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Efficiency of reversible engines
I'm a little confused about something. 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 ...
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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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Efficiency of Stirling engine and Carnot's theorem
I want to calculate the efficiency of this Stirling cycle for an ideal gas $pV = nRT$
The mechanical work is
$$
\Delta W_{12} = - \int_{V_1}^{V_2} p(V) \mathrm{d}V = -nRT_2 \ln \frac{V_2}{V_1}\\
\...
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