80 Transactions of the American Institute. 



Each pound of saturated steam transferred to the condensing 

 water the quantity of heat which had been required to raise it from 

 the temperature of the water of condensation to that due to the pres- 

 sure at which it left the boiler, plus the heat required to evaporate it 

 at that temperature. 



Each pound of water gives up only the quantity of heat required 

 to raise it from the temperature of the water of condensation to that 

 of the steam with which it is mingled. 



Tlie total amount of heat is made up of two quantities, therefore,, 

 and a very simple algebraic equation may be constructed, which shall 

 express the conditions of the problem : 



Let i7=heat units transferred per pound of steam. 

 h =heat units transferred per pound of water. 

 U = total quantity of heat transferred to condenser. 

 W= total weight of steam and water, or of feed water. 

 x = total weight of steam. 

 W— x— total weight of water primed. 



Then Hx+h (W-x) = U ; or, x= V— 



A 



Substituting the proper values in this equation, we determine the 

 absolute weights and per ceniages of steam and water delivered by 

 the several boilers to be as follows : 



Per centage of 

 Weight of Weight of water primed 



steam. water. to water evap- 



orated. 



Eoot 27,896. 0. 0. 



Allen 39,670. 0. 0. 



Phleger 19,782.94 645.06 3.26 



Lowe 31,663.35 2,336.65 6.9 



Blanchard 9,855.6 .296.9 3. 



And the amount of 'water ; in pounds ', actually evaporated per pound 

 of combustible : 



Eoot . . . . , 8.76 



Allen 8.76 



Phleger 8 .70 



Lowe 8.55 



Blanchard 9 .41 



Comparing the above results, the committee are enabled to state 

 the following order of capacity and of economy, in the boilers exhi- 

 bited, and their relative per centage of useful effect, as compared 

 with the economical value of a steam boiler that should utilize all of 

 the heat contained in the fuel : 



