l8 PROPERTIES OF STEAM AND OTHER VAPORS. 



When the condition of the mixture of a liquid and its vapor is gi 

 by the pressure and value of .v, then a table giving the properties at each 

 pound may be conveniently used for this work. 



Adiabatic Equation for a Liquid and its Vapor. During an adiabatic 

 change the entropy is constant, so that the preceding equation g 



When the initial state, determined l>y .v, and /, or />,, is known and the 

 final temperature /,, or the final pressure />,, the final value #, may be 

 found by this equation. The initial and final volumes mav be calcu- 

 1 by the equations 



Tables of the properties of saturated vapor commonly give the specific 

 volume 5 but 



s = u + <r. 



The value of <r for water is 0.016, and for other liquids will be found in 

 Table XI I. 



For example, one pound of dry steam at 100 pounds absolute lias the 

 following properties found in Table 1 1 : 



/, =327.6 K. - = 1.1228 O l = 0.4743 5, = 4.409 x l = i 

 1 i 



If the final pressure is 15 pounds absolute, we have 



/ 2 = 2i3.o F. -? = 1.4358 2 = 0.3141 s 2 = 26.21 



2 



whence 



1.5971 = 1.4358 x -f 0.3141 



^ = ^935 

 The initial and final volumes are 



v l = 5, = 4.409 



v t - Xjit + <r - 23.40 



Such a problem cannot be solved inversely, that is we cannot assume 

 a final volume and determine directly the temperature and pressure cor- 

 responding. The Temperature-Entropy Table to be explained later 



