EVAPORATION 321 



while the degree Brix of the juicei leaving each cell will be 

 (I — 0-786 X 0-213) =15-6. 

 j I — o - 786 (0-213 + o - 224) I =19-7. 

 {i -0-786 (0-213 +0-224 +0-248)) =33-^- 

 1 1 — o - 786 (0-213 + o - 224 + o - 248 + o - 315) I = 60 • 8. 



The conditions as determined experimentally in a multiple effect are not 

 as computed, and hence it is not advisable to use these results as a basis of 

 design or for other purpose generally, except as a means of demonstration 

 of underlying principles. 



The Actual Conditions obtaining in Multiple Effect Apparatus. — In the 



following pages an account "s given of observations made by the writer, 

 chiefly on a vertical submerged tube quadruple from which steam was not 

 separated. The nomenclature adopted is shown in Fig. 185, where C, J, VS, 

 and CW, distinguished by appropriate suffixes, denote the temperatures 

 of the steam in the calandria, of the juice, of the vapour space and of the 



\/s. 



VS, 



ws. 



ys. 



CWfl 



condensed water. C was observed in the vapour pipe immediately before 

 it entered the calandria ; VS was observed about three feet above the upper 

 tube plates ; / and CW were observed in the pipes cis the juice or water left 

 an effect. 



The temperature difference in any cell is C„ — /„, and the total tempera- 

 ture difference is C^ — /„ where n is the number of vessels : the values of 

 /„, VS„, C„+i, Cir,.,^i were found to be very close together and to be in 

 descending order of magnitude. In what follows C„ — C„+i is usually taken 

 as the temperature difference in any cell, since these temperatures are 

 the ones most easil}^ observed, and Cj — VS^^ is sometimes taken as the 

 gross temperature difference. 



Distribution of the Temperature Difference. — Under the conventional 

 methods of operation the total available fall in temperature is of the order 

 100° F. This fall is unevenly divided between the cells, and it is the last 

 cell that absorbs an undue proportion of the available fall. The balance of 

 the temperature difference is unevenly divided between the other bodies. 

 In an apparatus \vith each cell equally clean there are reasons for believing 



z 



