Temperature–entropy diagram
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![]() The classical Carnot heat engine | ||||||||||||
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Note: Conjugate variables in italics
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In thermodynamics, a temperature–entropy (T–s) diagram is a thermodynamic diagram used to visualize changes to temperature (T ) and specific entropy (s) during a thermodynamic process or cycle as the graph of a curve. It is a useful and common tool, particularly because it helps to visualize the heat transfer during a process. For reversible (ideal) processes, the area under the T–s curve of a process is the heat transferred to the system during that process.[1]
Working fluids are often categorized on the basis of the shape of their T–s diagram.
An isentropic process is depicted as a vertical line on a T–s diagram, whereas an isothermal process is a horizontal line.[2]
![](http://upload.wikimedia.org/wikipedia/commons/thumb/f/f4/Ejemplo_Diagrama_T-S.png/220px-Ejemplo_Diagrama_T-S.png)
For reversible processes, such as those found in the Carnot cycle:
If the cycle moves in a clockwise sense, then it is a heat engine that outputs work; if the cycle moves in a counterclockwise sense, it is a heat pump that takes in work and moves heat QH from the cold reservoir to the hot reservoir.
![](http://upload.wikimedia.org/wikipedia/commons/thumb/7/79/Temperature-entropy_chart_for_steam%2C_imperial_units.svg/220px-Temperature-entropy_chart_for_steam%2C_imperial_units.svg.png)
See also
- Carnot cycle
- Pressure–volume diagram
- Rankine cycle
- Saturation vapor curve
- Working fluid
- Working fluid selection
References
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