BeginnerTopic 26 of 105Thermodynamics & Fluids
T-s diagrams
Visualise cycles and heat transfer as area on a temperature-entropy plot.
In depth
T on the vertical axis and s horizontal: area under a reversible path is heat. Isentropic processes are vertical lines; the saturation dome frames phase change. Used to visualise Rankine and refrigeration cycles and to compare efficiencies.
Key points
- Heat = ∫T ds
- Superheat and reheat visible
- Carnot is a rectangle
ExampleA Rankine cycle on a T-s diagram shows how superheating moves heat addition to higher T.
What is T-s diagrams?
Visualise cycles and heat transfer as area on a temperature-entropy plot.
Why is it important to understand T-s diagrams?
T-s diagrams show heat as an area and make efficiency easy to read for cycles, so they are the standard visual tool for power plants.
How is heat shown on a T-s diagram?
As the area under the process path, the heat transferred during a reversible process.
Why is a T-s diagram better than a P-V diagram for steam?
Steam's dome is clear on T-s, and heat and efficiency of power cycles appear directly as areas.
How is T-s diagrams used in practice?
Typical applications include comparing the heat input of a Rankine cycle with an ideal Carnot cycle, finding the heat added and rejected by a refrigeration cycle and visualising the effect of superheating on steam cycle performance.
What should I learn before T-s diagrams?
Study "Entropy" first (topic 25 of 105 in Thermodynamics & Fluids). It covers the groundwork this topic builds on.
What are the key points of T-s diagrams?
Heat = ∫T ds. Superheat and reheat visible. Carnot is a rectangle.
Can you give an example of T-s diagrams?
A Rankine cycle on a T-s diagram shows how superheating moves heat addition to higher T.
What comes after T-s diagrams?
The next topic is "Isentropic efficiency", which builds directly on this one.
How difficult is T-s diagrams?
It is classed as Beginner in Thermodynamics & Fluids (topic 26 of 105). It is an entry-level topic. It relies only on basic school mathematics and the ideas introduced earlier in this discipline.