DAVIS. — A PQ PLANE FOR THERMODYNAMIC CYCLIC ANALYSIS, G41 



are peculiar in that for them the point e of Figure 2 coincides with the 

 point g. of that figure; in other words this line (^e = T^ is a locus of 

 first order cycles of the type of Figure 1, which thus appear as special 

 cases of the second order cycles of type B. It is evident that the ab- 

 scissa of any point of this locus represents the amount of heat that must 

 be supplied to a unit mass of isothermally compressed air, to raise its 

 temperature to that of adiabatically compressed air at the same pressure ; 



too 



300 350 400 450 500 

 in BTU 



150 200 250 



Figure 8. 



Type B. Final temperature. For cycles with isothermal compression. (Cf. 

 Figure 3.) 



and therefore, to bring such air to a given thermodynamic state requires 

 an amount of heat which is the sum of this preliminary.^' and the Q^ 

 of the corresponding adiabatic cycle. This explains the shearing of the 

 adiabatic plane. Points to the left of this locus represent figure-of-eight 

 cycles, so that, for the engineer, this line is a sort of natural boundary 

 for the isothermal plane. 



The FT" area for the same values of Fand 7'^ as were used before, 

 now takes the form indicated in Figure 10. Its boundaries have simply 

 been subjected to the horizontal shear already described, so that the P 



VOL. XL. 41 



