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Enthalpy Entropy Diagram Steam

Reference data and engineering information about enthalpy entropy diagram steam for thermodynamics applications.

enthalpyentropydiagramsteamData Table

Overview

Engineering reference data for Enthalpy Entropy Diagram Steam in thermodynamics.

Key Formulas

First Law

ΔU=Q−W\Delta U = Q - W

Energy is conserved — heat added minus work done.

Ideal Gas Law

PV=nRTPV = nRT

Relates pressure, volume, and temperature of an ideal gas.

Heat Transfer

Q=mcΔTQ = mc\Delta T

Sensible heat transfer.

Carnot Efficiency

η=1−TC/TH\eta = 1 - T_C/T_H

Maximum efficiency between two temperatures.

Variables

Symbol Description Unit
UU Internal energy J
QQ Heat J
WW Work J
PP Pressure Pa
VV Volume m³
TT Temperature K

Understanding the Diagram

The Enthalpy-Entropy (h-s) diagram, also known as the Mollier diagram, is a fundamental tool in steam engineering. It graphically represents the thermodynamic properties of water and steam, primarily plotting specific enthalpy (h) on the y-axis against specific entropy (s) on the x-axis.

How to Read the Diagram

  • Constant Pressure Lines: Curve upward and to the right.
  • Constant Temperature Lines: In the wet region (under the dome), they are horizontal. In the superheated region, they curve upward.
  • Constant Quality Lines: Radiate from the critical point, dividing the wet region.
  • The Saturation Dome: The enclosed curve where liquid and vapor coexist.

Reference Diagram

A printable version of the phase diagram for water can be found here: Water Phase Diagram (PDF)

Note: For precise calculations, always refer to official steam tables as the h-s diagram is a graphical approximation.

References