The steaming temperature, called saturation temperature, heat transfer manufacturers increases when the pressure is increased. It can be summarized that heat power engineers using steam properties is seriously encouraged to use software and must evaluate that the program is based on IAWPS latest edition, provides maximum choice of input/output data and units' features, accuracy,

updating options and finally the price. Accuracy is key aspect, which should be verified by the buyer by using the figures given specifically for testing in IAPWS.

Review of some of them reveals that all are not equally good. Although steam tables and the diagram provides reasonably acceptable data still now, but it always remains difficult to get accurate output from the tables and the chart due to interpolation errors.

Another phenomenon is that during steaming from liquid water, it passes through a mixed phase, called saturation zone, when both water and steam simultaneously exists till it gets fully converted to dry steam and during that period the temperature does not increase when the pressure is kept constant.