196 



R. Clausius on the Application of the 



stant temperature of the condenser be called T 0 . During the con- 

 nection of the cylinder with the condenser, the piston goes "back 

 again through the whole space which it previously passed over, 

 and thereby all the steam which did not of itself pass directly 

 into the condenser is driven into this and is here condensed. It 

 only remains in order to complete the cyclus of operations, to 

 bring back into the boiler the liquid which has arisen from the 

 condensation of the steam. This purpose is served by the small 

 pump I), whose action is so regulated that during the ascent of 

 the piston, it draws up exactly as much liquid from the conden- 

 ser as has been brought into this last by the condensation of the 

 steam; and this quantity of liquid is then forced into the boiler 

 by the descent of the piston. When this has here become heated 

 again to the temperature T„ everything is again in the initial 

 condition, and the same series of processes can begin anew. We 

 have here then to deal with a complete circular process. 



In common steam engines, the steam passes into the cylinder 

 not only from one side, but alternately from both. This however 

 produces only the difference that during an ascent and descent 

 of the piston, two circular processes take place instead of one, 

 and it is sufficient in this case also to determine the work for one 

 of them in order to be able to deduce the whole work which is 

 done during any time. 



19. In this determination we will, as is customary, consider the 

 cylinder as a shell which is impenetrable to heat, neglecting the 

 exchange of heat which takes place during one stroke between 

 the walls of the cylinder and the steam. The mass in the cylin- 

 der can only consist of steam at a maximum density mixed with 

 some liquid. It is clear from the foregoing, that the steam can- 

 not pass into the overheated condition during the expansion 

 which takes place in the cylinder after cutting off its connection 

 with the boiler, provided that no heat be communicated from 

 without, but on the contrary that it must be partly precipitated, 

 and in other processes to be mentioned farther on, which it is 

 true might occasion a slight overheating, this is prevented by the 

 fact that the steam in rushing into the cylinder always carries 

 with it some liquid and remains in contact with it. 



The quantity of this liquid mixed with the steam is insignifi- 

 cant, and as it is for the most part distributed through the steam ? 

 in fine drops, and consequently can rapidly participate in the 

 changes of temperature which the steam undergoes during the 

 expansion, we shall make no sensible error if we consider in cal- 

 culation the temperature of the whole mass in the cylinder as 

 the same for every determined instant of time. 



Furthermore, not to make the formulas too complicated at the 

 outset, we will in the first place determine the whole work which 

 is done by the pressure of the steam without taking into account 



