Steam tables and charts


Steam is in a vapor state which is widely different from a gas. No gas laws are applicable to vapor analysis. There are complex equations of state for a vapor. Consequently tables and charts have been prepared for the steam vapors for making analysis simple and time saving.


Only saturated as well as specific properties of water and steam at various temperatures and pressures can be read from steam tables and charts. Specific volume, specific enthalpy and entropy for saturated liquid and saturated vapors are given in the table.


There is another shorter way for analysis of systems by the use of temperature entropy chart and enthalpy entropy chart (also called the Mollier Chart) using steam as the working substance as in steam engines, steam turbines and various space heating applications.


Refer to Fig. and concentrate on the following lines which are highly helpful in the analysis.


This chart is extremely helpful in the analysis. This contains the following lines.Black 1. Thick is saturated vapor curve. Below this is wet region. Above this is super heated region

2. Inclined straight lines are constant pressure lines

3. Thick black vertical line BC is constant entropy lines.

4. Horizontal lines are constant enthalpy lines.

5. Curved lines in the wet region are constant dryness fraction lines.

6. Curved lines in the super heated region are constant temperature lines.


Rankine Cycle uses steam as the working substance for its analysis. At various points of the cycle, various  properties of steam are required. These properties can be easily read from these charts since all the processes of Rankine Cycle can be easily represented on these charts. Use of steam tables for analysis will be more time consuming as compared to the use of charts because values in steam tables are given at some specific pressures and temperatures which are not going to coincide with actual conditions in the cycle.