Enthalpy(H) - Entropy(S) Diagram OR Mollier Diagram

MOLLIER DIAGRAM 

The Mollier Diagram is named after a german Mechanical Engineer Richard Mollier. It is a graphical representation of steam tables, in which Specific Entropy is plotted along the ordinate(X-axis) and Specific Enthalpy along the abscissa(Y-axis). The diagram is divided into two portions by a somewhat horizontal line termed as Saturation Curve.The lower portion(i.e., wet stream region) contains the values of wet stream, whereas the upper portion (i.e.,superheated steam region ) contains the values of superheated stream. 

A Mollier diagram has the following lines:-

     1.    Dryness Fraction lines

     2.    Constant Specific Volume lines

     3.    Constant Pressure lines

     4.    Constant Temperature lines

Dryness Fraction lines :-

These lines are drawn in the wet stream region.i.e., only below the saturation curve (which represents dryness fraction equal to unity). These lines represent the condition of wet steam between various values of enthalpy and entropy. The dryness fraction lines are slightly curved in horizontal direction.

Constant Specific Volume Lines :-

These lines are drawn in both wet steam region and superheated steam region. These lines represent the specific volume of steam between the various values of enthalpy and entropy. The lines are straight in the wet steam region, i.e., below the saturation curve, but are curved upwards in the superheated region i.e., above the saturation curve.

Constant Pressure Lines :-

These lines are also drawn in both wet steam region and superheated steam region. These lines represent the pressure of steam between the various values of enthalpy and entropy. The pressure lines are also straight in the wet steam region, i.e., below the saturation curve, but are curved slightly upwards in the superheated region i.e., above the saturation curve.

Constant Temperature Lines :-

These lines are drawn only in the superheated steam region i.e., above the saturation curve. These lines represent the temperature of steam between the various values of enthalpy and entropy . The temperature lines are slightly curved in the horizontal direction.