EVAPORATION 



323 



Calandria 3. 



Calandria 4 



Vapour 

 space 4. 



Vacuum, ins. . . 



Temp, corresponding to vacuum, F° 



Observed temp., F° . . 



Superheat 



6-9 

 198-5 

 199-7 



I -2 



16 -4 



173-9 

 176 -2 



2-3 



26-2 

 119-6 

 135-3 



15-7 



Evaporation in each Cell. — The computation given above showed that 

 there should be a progressive increase in evaporation from cell to cell, but 

 on actual experiment the very irregular results given below were found. 

 The evaporation in each cell will be controlled by part of the heat appearing 

 as superheat, and by the quantit}^ of steam carried forward with the incon- 

 densible gases. The experiments were made with three sets of apparatus, 

 and, if anything, point to a nearly equal evaporation in the first three cells, 

 with a small increase in the last cell, much less than the computed increase. 

 In all these experiments the condensed water was discharged from each cell 

 direct. 



Percentage Evaporation in each Cell. 



The Actual Amounts of Water Evaporated. — This quantity was determined 

 by the writer in five quadruple effect evaporators ; the results given below 

 are calculated to the equivalent evaporation per lb. of dry steam with juice 

 entering at the temperature prevailing in the first cell. B}^ efficiency is meant 

 the percentage of heat accounted for in evaporation compared with the 

 maximum possible imder the conditions of operation, i.e., with reference 

 to the methods used for elimination of water and incondensible gases. 



1. Horizontal film ; S906 sq. ft. h.s. evaporating at rate of 5-6 lbs. per 

 sq. ft.-hr. ; 2,170 sq. ft. area protected with i in. asbestos ; 330 sq. ft. bare ; 

 water from Cell i, discharged direct, from Cells 2, 3, 4, through Cell 4 ; gases 

 vented from ceU to cell. Cj 225° F. ; VS^ 130° F, ; water evaporated ^steam 

 condensed 3 - 88 ; efficiency 90 - o per cent. 



2. Horizontal film ; 9,775 sq. ft. h.s. evaporating at rate of 9-10 lbs. 

 per sq. ft.-hr.; 2,800 sq. ft. area, zM bare ; water discharge and gases as in i. 

 Ci 214° F. ; FS4 132° F. ; w^ater evaporated /steam condensed 3-61; 

 efficienc}^ 88-6 per cent. 



3. Horizontal submerged tube; 11,284 sq. ft. h.s. evaporating at rate 

 of 6-7 lbs. per sq. ft.-hr ' 1,670 sq. ft. area protected with i in. asbestos, 



