The Mollier Diagram (h-s)

The Mollier Diagram (h-s)

#

The Mollier diagram plots enthalpy (h) vs entropy (s) for steam. Essential for analyzing turbines and steam cycles.

Zones

#

• Left of saturation curve: subcooled liquid
• Under the curve: wet steam (liquid + vapor mixture)
• Right of the curve: superheated vapor

Key Lines

#

Isobars (constant pressure), isotherms, quality lines (steam fraction), isentropic lines (vertical).

Turbine Analysis

#

Ideal expansion: vertical line (constant entropy) from high to low pressure. Work = \(\Delta h = h_1 - h_2\). Real expansion: entropy increases (line tilts right). Efficiency: \(\eta = \frac{h_1 - h_{2,real}}{h_1 - h_{2,ideal}}\)

Conclusion

#

The Mollier diagram lets you quickly analyze steam transformations and calculate turbine work without solving complex equations.