278 



TABLES 261-267.— THE JOULE-THOMSON EFFECT IN FLUIDS * 



The Joule-Thomson effect is defined as the ratio of the change in tempera- 

 ture to the drop in pressure of a fluid driven by the drop in pressure through 

 a porous partial blockage in the fluid flow tube. The space between the reading 

 thermometers on each side of the porous obstruction is to be isolated as to 

 exchange of heat energy but not as to work energy. Nor must the fluid gain a 

 significant amount of directed kinetic energy between the thermometers. Under 



these circumstances the Joule-Thomson effect, a = ( — — ) , where h = u — pv = 



\dpj h 



enthalpy, and since ft is a function of both t and p, the steps are preferably 



represented as infinitesimals. Since Ap is always negative, /x is positive when 



At is negative. For all the gases yet measured, /x is zero along a line in the 



tp plane called the inversion line. 



* The material on the Joule-Thomson effect was supplied by J. R. Roebuck, of the Uni- 

 versity of Wisconsin. 



TABLE 261.— THE JOULE-THOMSON EFFECT ON AIR (WATER AND CARBON 



DIOXIDE FREE) <* 



M as a function of t and p, t in °C, p in atm, m in c C/atm. 



83 Proc. Amer. Acad. Arts and Sci., vol. 60, p. 535, 1025; vol. 64, p. 287, 1930 (both corrected). 



TABLE 262.— THE JOULE-THOMSON EFFECT ON HELIUM 81 



M as a function to t (and independent of pressure up to 200 atm), / in °C, fi in °C/atm. 



8J Phys. Rev., vol. 43, p. 60, 1933 (corrected). 



SMITHSONIAN PHYSICAL TABLES 



