Page 46 - DJJ20063- Thermodynamics 1

DJJ20063- Thermodynamics 1

Superheated Steam Tables

A steam is called superheated when its temperature is greater than the saturation

temperature corresponding to the pressure. When the pressure and temperature are
given for the superheated steam then the state is defined and all the other properties can

be found.

Example 2.3
o
steam at 10 bar and 200 C is superheated since the saturation temperature at 10 bar is
o
o
o
179.9 C. The steam at this state has a degree of superheat of 200 C – 179.9 C = 20.1
o C. The equation of degree of superheat is:

Degree of superheat = tsuperheat – tsaturation (2.7)

The tables of properties of superheated steam range in pressure from 0.006112 bar to

the critical pressure of 221.2 bar. At each pressure, there is a range of temperature up to
high degrees of superheat, and the values of specific volume, internal energy, enthalpy

and entropy are tabulated.

For the pressure above 70 bar, the specific internal energy is not tabulated. The specific
internal energy is calculated using the equation:

u = h – pv (2.8)

For reference, the saturation temperature is inserted in brackets under each pressure in

the superheat tables and values of vg, ug, hg and sg are also given.

A specimen row of values is shown in Table 2.2.4-3. For example, from the superheated
3
o
table at 10 bar and 200 C, the specific volume is 0.2061 m /kg and the specific enthalpy
is 2829 kJ/kg.

37 | P a g e