Manchester Memoirs, Vol. xlv. (1901), No. 10. 



X. On the Construction of Entropy Diagrams from 

 Steam Engine Indicator Diagrams. 



By George Wilson, D.Sc, 



Demonstrator in the Whitivorth Engineering Laboratory, Owens College, 

 Manchester, 



AND 



H. Noble, B.Sc, 



IVhitzoorth Scholar, Owens College, Manchester. 

 Received and read February jlh, igoi . 



The examples of steam engine entropy diagrams which 

 have appeared from time to time in the Proceedings of 

 Engineering Institutions, and in the professional journals, 

 are constructed, in each case, to represent the heat changes 

 which take place, for the total amount of steam and water 

 in the cylinder. This quantity usually varies for each 

 cylinder in Compound, Triple or Quadruple Expansion 

 Engines. It is therefore necessary, under this system, to use 

 different scales of entropy for each diagram, if the same 

 water and steam lines are to be utilised throughout. From 

 this it follows that the relation of the combined area of 

 the indicator diagrams, when converted in this manner 

 into entropy diagrams, to the area which represents, in 

 the same diagram, the total heat received, does not repre- 

 sent the efficiency of the steam. In this respect also, 

 therefore, the entropy diagram, as at present constructed, 

 is at a disadvantage when compared with the reduced and 

 combined /.7/. diagrams for the same engines. 



That it would be an advantage to deal with the same 



Septe7nber loth, igoi. 



