Questions tagged [carnot-cycle]
A theoretical ideal thermodynamic cycle which provides an upper limit on the efficiency that any classical thermodynamic engine can achieve during the conversion of heat into work, or conversely, the efficiency of a refrigeration system in creating a temperature difference by the application of work to the system.
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Is Carnot theorem applicable to black holes?
As I know, there is a simple method to take almost all $mc^2$ from mass by dropping it to the black hole. Doesn't this violate Carnot theorem? Or does it define the temperature of black hole as very ...
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"Universality" of Carnot cycles
In his answer to the discussion "Historical view of the second law of thermodynamics as a complete differential" (https://physics.stackexchange.com/q/823281)
@hyportnex wrote that:
Contrary ...
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At what stage in the Carnot cycle, does a Carnot engine produce work?
I am currently confused as to how exactly a Carnot engine (ideal engine) produces work. I will explain my current understanding of how a Carnot engine works:
A piston containing gas is placed into ...
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Contradiction in the Carnot Cycle?
The carnot cycle is reversible, because the temperature difference between heat reservoir and fluid is extremely low, so that heat can flow in both directions.
Also, the carnot cycle is described as ...
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What happens if you factor in the energy required to switch between the reservoirs and insulating stand of the Carnot engine?
I'm reading about the Carnot cycle (as a non-physicist!) and much of the focus is on the idealisation around the infinite time needed due to the requirement of only infinitesimal differences in ...
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Efficiency of thermal (rankine) power plants based on ambient temperature?
so I'm preparing for an interview and this is a common question that they always ask,
Say there are two power plants working on ideal rankine cycle
One in Alaska (low ambient temperature) and one in ...
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Relation between heat quotient and temperature quotient
Is $$\frac{Q_c}{Q_h} = \frac{T_c}{T_h}$$ valid for any reversible ideal cycle Or just for the Carnot cycle?
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Application of Stokes theorem in closed thermodynamic cycles
I was reading a book on thermodynamics when I came across the following:
"Any closed thermodynamic cycle can be approximated by infinitely many Carnot cycles".
I realize that because the ...
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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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Is there a specific commercial or experimental implementation of the Carnot cycle? [closed]
I have been unable to find an example of a Carnot engine implemented practically, beyond the drinking bird (which has not revolutionized technology as far as I know). I understand the Stirling and ...
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How does Heat flows in Carnot engine? [duplicate]
According to fundamental concept of thermal conduction, heat flows from higher temperature to lower temperature. As in Carnot cycle, there is isothermal expansion and compression as a process i.e. ...
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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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How to derive the Clausius Inequality?
In my thermodynamics class, we've seen the Clausius inequality derived for a Carnot cycle, and then extended to any cycle. For the Carnot Cycle, we have that it's the most efficient possible cycle ...
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Why does the temperature of the working fluid have to be close to the temperature of the cold reservoir during a Carnot cycle?
I understand why the temperature of the hot reservoir has to be minimally higher than the temperature of the hot working fluid during the isothermal expansion phase of the Carnot cycle (to limit new ...
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Work obtained during isentropic expansion in the Carnot cycle versus the work done to gradually lower the outside pressure
We have a Carnot cycle and lets say it is in thermal and mechanical equilibrium with the surroundings before the beginning of the process. I am using the convention that heat brought to the system is ...
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In a Carnot Engine, how does the heat flow from the heat reservoir to the engine if both are at the same temperature?
From what I read about the Carnot Cycle, there are 4 major steps involved, viz. Isothermal Expansion, Adiabatic expansion, Isothermal compression and Adiabatic compression. During the Isothermal ...
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Relationship between volume and temperature of an ideal gas
I am self-studying thermodynamics, and was reading up Carnot heat engine (Yunus Cengel - thermodynamics book). So, the experiment in the textbook is set up such that, we have an adiabatic piston-...
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Carnot cycle with finite heat capacity [closed]
Suppose we perform a Carnot Cycle between 2 temperature baths $T_1$ and $T_2$ with $T_2>T_1$ and both having finite heat capacity $C$. What is the final equilibrium temperature?
I have a vague ...
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Where is the heat loss occuring in the Carnot cycle, if compared to a ideal gas turbine
The most efficient heat engine cannot be more efficient than this (1 - tc/th) so let's assume a hypothetical gas turbine where there is no friction or conduction losses , say the ambient temp is 300k ,...
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Is there a thermodynamic cycle used where energy is extracted when the gas condenses to a liquid?
I was trying to calculate the energy efficiency of such a cycle, but I'm not sure how it depends on the input and output temperature difference, which doesn't seem right.
The cycle I was thinking of ...
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Thermodynamic temperature scale
I was wondering why is it that I can replace heat going into a carnot engine with the temperature of the "hot place" and vice versa, i.e , why can the temperatures of the places replace the ...
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Temperature Dependence of Thermal Efficiency in Carnot Cycle
Suppose a Carnot Cycle operates between a hot reservoir at temp $T_h$ and a cold reservoir at temp $T_c$. Suppose also that the system is initially at point $(V_1,p_1)$ in the pV-plane and that the ...
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Generalizing Carnot theorem
Motivated by question Can IC engines be modeled as Carnot engines?. I am wondering whether/how Carnot theorem could be generalized to other kinds of devices performing "useful work", such as,...
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Can IC engines be modeled as Carnot engines?
In the "talk" tab for Wikipedia Heat Engine article, someone is questioning whether an internal combustion engine can be modeled as a heat engine - and therefore is limited or is not limited ...
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An alternative approach to proving the Carnot's theorem using the equality of areas of $pV$ and $TS$ diagrams
According to Carnot's theorem, the efficiency of a reversible heat engine operating between two reservoirs at different temperatures is independent of the working substance and depends only on the ...
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Can heat flow from colder to hotter body breaking the second law of thermodynamics? [closed]
In an isothermal process, the whole heat is converted to work but not in a cycle so it doesn't break the 2nd law of thermodynamics.
$$dQ=dW$$
But let's imagine a scenario with it. If we connect an ...
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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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Calculation of efficiency of a heat engine [closed]
The efficiency of any heat engine doing work $W = |Q_{in}| - |Q_{out}|$ is given by:
$N = |W|/|Q_{in}|$
The reasoning for this given in my textbook is along the lines of:
The purpose of any heat ...
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Could Refrigerators Take In Cold Outside Air To Save Energy?
We heat up rooms, then we use that warm air and cool it down in refrigerators. Each is a lossy, energy requiring process. This seems thermodynamically inefficient. Couldn't refrigerators get cold air ...
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How the temperature used in second law of thermodynamics and ideal gas law equivalent? [closed]
I was reading Theory and Problems of Thermodynamics by Schaum's Outline series and there the author starts from some axioms (which are the thermodynamic laws, excluding the zeroth and third). Then he ...
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Why does heat engine efficiency use absolute zero rather than thermal differential?
Carnot's theorem calculates efficiency of a heat engine versus absolute zero. I read the question
Why can Carnot efficiency only be 100% at absolute zero?
But I don't feel it addresses it precisely.
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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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Carnot Cycle Question
I have two questions surrounding the Carnot cycle. The typical diagram for a Carnot cycle is shown here:
I have several textbooks that discuss this cycle, but what none of them do is explain how ...
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Confusion on Absolute Temperature Scales used in solving Carnot Cycle problems
I have a Carnot Cycle problem where the temperatures of the hot and cold reservoirs are given in Celsius and I'm asked to solve for the cycle efficiency. Of course, My first step is to convert Celsius ...
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Question regarding carnot engine
Why is it drawn as though the $heat$ is the entering & leaving the parallelogram in $PV Diagram$ of $Carnot$ $Cycle$.
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Is an isentropic process always adiabatic? [duplicate]
I am making an exercise about a pulsating jet engine. There is a part in the cycle of this engine that is an isentropic expansion and i'm wondering if I can use $PV^{g} = cte $ in this process
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Does isothermal expansion not beat the efficiency of Carnot Heat Engine?
Ques:
If I just take the 1st step of a Carnot Heat Engine (CHE) than it turns out to be more efficient than the CHE itself.
Explanation:
The 1st step of a CHE is the pure isothermal expansion of (...
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Vapor Compression Refrigeration Cycle
My question here is, why do we need point 2 to be on the saturated liquid line, i.e. why do we need a saturated liquid for the throttling process? Why can we not use it in the liquid region or ...
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Entropy of real substances - Is it possible to decompose arbitrary $p$-$V$ cycles of real substances in small Carnot cycles of an ideal gas?
In physics textbooks it is proved that $\oint\frac{δQ_{rev}}{T}=0$ by decomposing an arbitrary cycle in the $p$-$V$ diagram into infinitesimal Carnot cycles. Does the arbitrary cycle have to be a ...
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Why does adiabatic expansion occur in the carnot process?
(Spoiler: Why adiabatic expansion happens in Carnot cycle doesn't really answer the question for me.)
In the Carno cycle, the open system is first brought into contact with the warm reservoir, which ...
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Understanding Clausius theorem by slicing an arbitrary cycle into multiple Carnot cycles
As the title implies, I had some issues understanding how Clausius theorem
$$\int_{Closed}\frac{dQ}{T} = 0$$
can be derived for an arbitrary cycle starting by slicing it into multiple Carnot cycles. ...
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What stops entropy from forming if you extract 100% of heat flow and use it for work?
In a carnot engine you convert 100% of heat put inside the system during the isothermal phase into work. This is the basis of maximum efficiency and makes sure that it is reversible. If you don't ...
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Does the Carnot efficiency apply to photoelectric conversion?
If you consider a black body as energy source and photoelectric conversion at room temperature as the energy receiver.
Wouldn't it be possible to:
use an ideal prism/diffraction grating to separate ...
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How to justify that Carnot loop for ideal gas is closed on two sides by adiabatic curves?
I'm trying to figure out how to show that the orange curves connecting the two green curves are infact adiabatic:
The set up is that I have an ideal gas, and I am searching for the loop when it's ...
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How was adiabatic expansion conceived from the caloric theory perspective? [closed]
Nowadays we say that during the adiabatic expansion stage of the Carnot Cycle the internal energy due to the temperature of the gas gets transformed into work, but Carnot himself supported the caloric ...
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How is a Carnot engine in quasi-equilibrium?
If the reversible isothermal expansion and adiabatic expansion both yield positive work (as the pv diagram indicates), it means that the gas inside the cylinder was compressed before those stages ...
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Entropy change in each step of Carnot Cycle
How to go about calculating the entropy change in each step of a Carnot Cycle given only $T_{h}$, $T_{l}$, and the work performed per cycle?
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How to prove the efficiency of Carnot engine is bigger than Otto engine [closed]
I know the Carnot engine has maximum efficiency among all engines from Clausius statement, but how to prove the relationship of these two engines in equation? Thanks.
More specifically, the ...
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