Chapter 8 -INTRODUCTION TO THERMODYNAMICS 



PROPERTIESOF SATURATED STEAM 



147. 64X 



Figure 8-11.— Excerpts from Keenan and Keyes steam tables. 



have been discussed at some length in this 

 chapter and in the chapter dealing with prin- 

 ciples of measurement; at this point we are 

 concerned less with the properties themselves 

 than with the way in which they are tabulated 

 and the way in which they are represented 

 graphically. 



STEAM TABLES. — In the region near a 

 change of physical state, the behavior of a gase- 

 ous substance becomes too complex for the 

 relatively simple energy calculations that apply 

 to perfect gases and to many real gases over a 

 wide range of pressures and temperatures. 

 Because of the complicated equations needed 

 to describe the properties of vapors, engineers 

 customarily depend upon tables of vapor prop- 

 erties for information concerning the properties 

 of liquids and their vapors. The vapor tables 

 that are perhaps most commonly used are those 

 which give the thermodynamic properties of 

 steam. The most authoritative tables of thermo- 

 dynamic properties of steam are those prepared 

 by Keenan and Keyes under the title of Thermo- 

 dynamic Properties of Steam. ^'^ Figure 8-11 is 

 excerpted from Table III of the Keenan and Keyes 

 steam tables; it is included here chiefly to show 

 the general arrangement of information in these 

 tables, rather than to provide any significant 

 amount of data concerning the thermodynamic 

 properties of saturated steam. 



17 



Joseph H.' Keenan and FrederickG. Keyes. Thermo- 

 dynamic Properties of Steam . New York, John Wiley 

 & Sons, Inc., 1937. Excerpts from Table 111 are re- 

 printed through the courtesy of the publisher. 



The information given in each column of the 

 Keenan and Keyes table for the properties of 

 saturated steam is describedbriefly below. Note 

 that the subscript X is commonly used to denote 

 properties of the saturated liquid, g^ to denote 

 properties of the saturated vapor, and fg to de- 

 note property changes between the two states. 



Column 1 gives the saturation pressure of 

 the saturated water and the saturated steam at 

 the temperature given in column 2. Note that the 

 pressure is absolute pressure, not gage pres- 

 sure. 



Column 2 gives the saturation temperature 

 for the pressure shown in column 1. This tem- 

 perature is what is commonly referred to as 

 "the boiling point" of the liquid at the pressure 

 shown in column 1. In the steam tables, the 

 temperature is usually given in degrees Fahren- 

 heit rather than in degrees of an absolute 

 temperature scale. However, the absolute tem- 

 perature can always be obtained by simple com- 

 putation if it should be needed. 



Column 3 gives the specific volume of the 

 saturated liquid (water) at the pressure shown in 

 column 1 and the temperature shown in column 

 2. Specific volume is expressed in cubic feet per 

 pound. 



Column 4 gives the specific volume of the 

 saturated vapor (steam) at the pressure and 

 temperature shown. 



It should be noted that some portions of the 

 Keenan and Keyes steam tables have another 

 column for the increase in specific volume that 

 occurs during evaporation. This column is la- 

 belled Specific Volume, Evapo., symbolized by 



185 



