78 THE SCIENTIFIC PAPERS OF 



In the discussion of the Paper 



"ON GIFFARD INJECTOR FOR FEEDING STEAM- 

 BOILERS," by Mr. JOHN ROBINSON, 



ME. C. W. SIEMENS * said he had made some calculations as to 

 the rise of temperature in the feed-water by its passage through 

 the injector, on the assumption that the steam supply carried 

 the water along with it by impact, taking no account of the 

 friction of the water ; that is, that if 1 Ib. of steam in motion 

 were mixed with 2 Ibs. of water at rest, the result produced 

 would be 3 Ibs. put in motion at one-third the original velocity 

 of the steam. 



Now since the velocity of water or steam issuing into the atmo- 

 sphere from the same boiler was equal to that acquired by a 

 falling body in falling through the height of a column of the same 

 water or steam giving the same effective pressure, and since the 

 velocity acquired by a falling body was proportional to the square 

 root of the height through which it fell, it followed that the 

 velocity of the water and of the steam would be proportional to 

 the square roots of the relative volumes ; and as the volume of 

 steam with one atmosphere effective pressure was 860 times that 

 of water, it would issue with -v/860 or 29 times the velocity of 

 the water from the same boiler. Hence the steam issuing would 

 just balance 29 times its own weight of water trying to issue from 

 the boiler ; and, therefore, assuming the total heat of the steam to 

 be 1200, and the original temperature of the feed 100, the rise 



of temperature of the feed would be 12 j 1 10 _P = 37. And 



Zi) + 1 



calculating the rise of temperature in the same way for the 

 higher pressure of steam there would be 



with 1 atmosphere effective pressure 37 rise of temperature 



55 '" 1i 5> J> " ,, ,, 



5> " 55 55 55 *0 ,, ,, 



A KK 



55 55 55 5> ,, 



55 10 80 ,, 



* Excerpt Minutes of Proceedings of the Institution of Mechanical Engineers 

 1860, p. 78. 



