EVAPORATION 



327 



Rate of Evaporation in a Quadruple Effect as influenced by " Pressure " 

 OF Steam in First Calandria. 



C2 



C4 



1^54 . . 



" Vacuum," ins. 



Cx — C2 



Ci — F54 . . 

 Ci — C2 



C^F54^^°^ 

 C4 — F54 

 Q-F54 ^^°° 

 r (sees.) 



r(Ci — C2) . 

 r (Ci — vs^) 



Kx .. 

 K^ .. 



Km • ■ 



Lbs. water per 

 ft.-ho'jr 



sq. 



212 -6 

 207 -I 

 169 -o 

 120 -3 

 27-0 



5 '5 



48-7 



9-2 -3 

 5-95 



53 -I 



1012 



5566 



49284 



50S 



81 



3-95 



2l6 -2 

 208 -9 



171 -7 



121 -2 



26 -g 



7-3 



50-5 



95 -o 



7-68 



53-1 



776 

 5665 

 40298 



497 



99 



216 



5-13 



230 •» 

 218-6 

 184 -o 

 126 -o 



26-3 



T 2 '2 



58-0 

 104-8 



II -64 



55 -4 



445 

 5329 

 25810 



518 



154 



337 



8-95 



.\nalvsis of the results in the two preceding schedules leads to the follow- 

 ing conclusions : — 



1. The value of K^ increases as the temperature difference increases, 

 although certain obser\'ations present irregularities, probably due to errors 

 of experiment and to chfhculty in maintaining all desired conditions 

 unchanged. 



2. In the series ^nth C^ constant and VS^ varying, the value of Km 

 does not suffer much change, so that the water evaporated is nearh' directly 

 proportional to the total temperature difference, or to Cj — FS4. 



3. Comparisons of values of K are obscured by the effect of the variation 

 in the absolute value of the temperature difference, and by its position in 

 the absolute scale of temperature ; thus in the series with C^ constant, 

 K^ regularly increases as C^ — Cg increases, and K^ remains fairly constant 

 with a slight increase in the same sense. The less values of K^ occiir when 

 C4 — VS^ is smaller, but higher in the absolute scale of temperature. These 

 two influences may counterbalance each other, so that the combined effect 

 on K^ is small. On the other hand, in the series \nth C^ varying and VS^ 

 designed to be constant (actuallv, however, with a variation of 6° F.) there is 

 small change in the value of K^, with, if anything, a tendency to increase 

 as Ci — C, increases. K^, however, increases very largely, and here increase 

 in the value of Cj — FS4 is accompanied by an elevation of the position of 

 Ci — FS4 in the absolute scale of temperature ; at the same time a very 

 material increase occurs in the value oi Km- 



4. Increasing the temperature difference (Q — FS4) by increasing the 

 temperature at the hot end (increase of C^ or increase in the pressure of the 

 heating steam), increases the value of K,n or the capacity of the apparatus 

 much more than in direct proportion to the value of C^ — FS4. Increasing 



