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Questions tagged [carnot-cycle]

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Does Piston moves faster when we accelerate the car?

I am learning about car basics. I found that engine is nothing but a system where heat energy is converted into up/down motion of the piston in the cylinder. Finally, this up/down motion is converted ...
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1answer
108 views

Does a Carnot-efficient heat engine recover all work that was initially done?

There are two adiabatic containers filled with an ideal gas. In container A work is done which eventually turns completely into heat, leading to a temperature difference between container A and ...
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Reverse the combustion engine

All you know what a combustion engine is doing: Transform chemical energy into kinetic energy. What about the opposite? I know when I park a car at a slope and lose the breaks it will drive ...
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2answers
2k views

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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3answers
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Why is the cyclic volume integral of $P/T$ larger than the one of $P_ext/T$ in an irreversible process?

In order to derive the Clasius inequality we can call the first law of thermodynamics in it's differential form: $$dU={\itđ}q-P_{ext}dV.$$ If the process is reversible: $$dU={\itđ}q_{rev}-PdV.$$ ...
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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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1answer
321 views

Carnot cycle equation

How to prove the relation $\frac{Q_{given\space out}}{Q_{absorbed}}=\frac{T_{cold}}{T_{hot}}$ by only writing equations using first law?
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375 views

Understanding the Carnot cycle

My textbook explains the Carnot cycle as follows: Heat is added to the boiler, where the steam inside expands isothermally at high temperature (T(High))--(both valves closed). The intake valve is ...
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1answer
690 views

How to define the thermodynamic temperature

I've been reading derivations of the thermodynamic temperature scale. I'm assuming these are using Kelvin's method. I follow the math and the conclusion of the argument, but I don't understand how it ...
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0answers
31 views

Why an ideal gas expands in the 2nd step of carnot's cycle/engine?

In the 2nd step of carnot's cycle, when the gas cylinder is kept under an adiabatic condition, it expands and the temperature falls. My question is why does the gas spend it's internal energy to ...
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1answer
55 views

Efficiency of a reversible thermodinamic cycle

1 mole of ideal monoatomic gas completes a reversible ABC cycle, in which AB is a VOlume constant tranformation, BC an adiabatic expansion(Q=0) and CA an isotherm(Temperature during tranformation is ...
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1answer
56 views

Clausius's Carnot Cycle Equation Derivation

In his paper clausius describes a Carnot cycle and he continue arguing like below: In order to make an analytical application of the method...we will assume that all the changes which the gas ...
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2answers
106 views

Calculating efficiency of a Engine

Given are four points in a PV-diagram: $(V_1, 3/2P_1)$ is the leftmost point, $(V_2,3/2P_1)$ is the rightmost point, $(\frac{V_1+V_2}{2},P_1)$ is the lowest point and $(\frac{V_1+V_2}{2},2P_1)$ is the ...
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1answer
58 views

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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2answers
351 views

How do I prove that the Carnot cycle is the most efficient graphically? [closed]

I have to prove that the Carnot cycle is the most efficient by comparing it with a arbitrary cycle working within the temperature range of $T_L$ to $T_H$ in a ST-diagram. How do I do this?
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2answers
164 views

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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0answers
126 views

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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1answer
114 views

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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96 views

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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3answers
363 views

Where does the energy come from for adiabatic processes of a Carnot cycle?

I'm getting stuck on where this additional energy comes to move the piston further outward/inward during adiabatic processes when the only energy changed is during isothermal processes. Can someone ...
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1answer
84 views

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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0answers
71 views

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 ...
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1answer
26 views

Distributed Workload AS cooling?

To my understanding, many processes require cooling to achieve optimum use. Power stations, for example, require cooling for electricity production. Computer hardware systems, similarly require ...
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2answers
445 views

How is Carnot's theorem valid also for engines that are not heat engines?

I understood the statement and the proof of the Carnot theorem. Carnot's theorem states: All heat engines between two heat reservoirs are less efficient than a Carnot heat engine operating ...
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1answer
50 views

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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1answer
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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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1answer
223 views

Proving the following cycle is equivalent to Carnot cycle

I want to investigate whether the following cycle I'm about to describe is equivalent to Carnot cycle or not. By equivalent I mean, giving two reservoirs($A$,$B$) with temperature $T_1$ and $T_2$ with ...
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1answer
243 views

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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1answer
501 views

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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1answer
96 views

Carnot's Engine Proof flawed?

https://www.youtube.com/watch?v=LUoUb4hGMH8 I was looking at the reason as to why a Carnot Engine and watched this video on KhanAcademy. He used a very clever method of proving this by using the ...
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1answer
33 views

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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2answers
57 views

Efficiency of Carnot engine [duplicate]

Why is the efficiency of Carnot engine regarded as the maximum efficiency possible for a heat engine?