202 



R. Clausius on the Application of the 



warming and evaporation, has much lower temperatures than 

 the fire, and that thus the heat which is communicated to it 

 must pass from a higher to a lower temperature, there is in N 

 an uncompensated transformation which is not reckoned in the 

 calculation, which with the reference to making the heat useful 

 occasions a great loss. The work which can be obtained in the 

 steam engine from the quantity of heat, m, r x +Mc(T^ — 2\)— 

 is, as we see from equation (27), somewhat smaller than 



is T *~ T o 

 A ' T x ' 



If therefore the same quantity of heat could be communicated 

 to a variable body at the temperature of the fire, which may be 

 called T', while the temperature corresponding to the subtrac- 

 tion of heat, remains as formerly T 0 , the work possibly to be 

 obtained in this case according to equation (4) would be repre- 

 sented by 



A ' T ' 



In order to be able to compare the values of these expressions 

 in some examples, let the temperature t 0 of the condenser be 

 fixed at 50° C., and let the temperatures 110°, 150°, and 180° C. 

 be assumed for the boiler, of which the first two correspond 

 about to the low pressure engine and to the common high pres- 

 sure engine, and the last is to be regarded as about the limit of 

 the temperatures used in steam engines in practice. For these 

 cases, the fraction depending on the temperatures has the follow- 

 ing value. 



h 



110° 



150° 



180° 





0-157 



0-236 



0-287 





Whereas the corresponding value for the temperature of V of 

 the fire, if we assume this only at 1000° C. is 0746. 



25. It is hereby easy to perceive what S. Carnot and after 

 him many other authors have asserted, that in order to arrange 

 machines moved by heat more advantageously, we must princi- 

 pally endeavor to make the interval of temperature 1\ — T 0 

 greater. It is thus for example in the case of the caloric air 

 machines only then to be expected that they will obtain an im- 

 portant advantage over steam engines, when we succeed in mak- 

 ing them work at considerable higher temperatures than steam 

 engines, in which the danger of explosion forbids the applica- 

 tion of too high temperatures. The same advantage may how- 

 ever also be obtained with overheated steam, since as soon as 

 the vapor is separated from the liquid, we may heat it still fur- 



