CANE SUGAR. 



5. The total quantity evaporated in the last vessel is 

 In the double effect 0-534. 

 In the triple effect 0-3734. 

 In the quadruple effect 0-284 

 of the total evaporation of the apparatus. 



In the mean the evaporative capacity of each vessel, not including self- 

 evaporation in the vessel, but including the evaporation due to heating from 

 self-evaporation in a previous vessel, is in 

 Double effect 1 : 1-0045 

 Triple effect 1 : 1-0075 : 1-138. 

 Quadruple effect 1 : 1-0055 : 1-109 : 1-196. 



Hausbrand uses the figures given immediately above to calculate the 

 relative areas of heating surface in the different vessels, provided the coefficient 

 of transmission of heat is known in each vessel ; if, for the moment, this be 

 taken as the same for each vessel, then if equal differences of temperature are 

 desired from vessel to vessel, this would be obtained by making the heating 

 surfaces in the ratio given above ; similarly, if the heating surfaces were made 

 the same in all the vessels the falls in temperature would be in the same ratio. 

 The transmission of heat is, however, not the same for all the vessels ; it 

 decreases from vessel to vessel, due to the greater viscosity and to the incrus- 

 tations being more pronounced in the later vessels. 



Claassen, from actual observations in beet sugar factories, gives the 

 following ratios for the transmission coefficient : 



Vessel. I. II. III. IV. 



Double effect ........ 1 : 0'66 



Triple .......... 1 : 0'70 : 0'33 



Quadruple effect ....... 1 : 0'91 : 0'75 : 0'55 



If these figures be taken as data, then to obtain the same temperature 

 difference, the heating surfaces would be in the ratio : 

 Double effect 



Triple effect 



Quadruple effect 



.- , 



..... 



Now since it is only by larger differences in temperature that viscid juices 

 are brought into violent ebullition, and since it is of great importance to main- 

 tain a rapid movement and good circulation, it is better, says Hausbrand, to 

 have a large fall in temperature between the two last bodies, and not to aim at 

 equalizing the fall in lemperature by increasing the heating surface in the later 

 bodies. 



310 



