THE EVAPORATION OF THE JUICE TO SYRUP. 



Ruissellement. By this term is meant the evaporation of juices in 

 films as opposed to evaporation in bulk. It will be shown later that a high 

 level of the juice undergoing evaporation is not conducive to a high efficiency, 

 and further in bulk evaporation the body of juice under treatment at one time 

 is great and may represent up to two hours' output of the mills. To overcome 

 this disadvantage of the vertical tube apparatus many appendages to and 

 various forms of tubes have been invented with the object of maintaining a 

 film of liquid on the interior of the tubes. None of these devices have come 

 into permanent use, as from their nature they prevented the cleaning of the 



FIG. 175. 



tubes. Ruissellement^ or film evaporation, has, however, been successfully 

 .applied in the Yaryan, Lillie, and Kestner designs, and has been adapted to 

 the vertical tube apparatus in the Meyer and Arbuckle patent ; this process is 

 shown schematically in Fig. 175. The circulation of the juice is effected by 

 the centrifugal pumps; the juice on entering the pipe emerges as a 

 spray through perforations in the latter and at the same time causes the pipe 

 to revolve in a horizontal plane ; the action is exactly similar to the sprinklers 

 commonly used in watering lawns. 



Film evaporation may to a certain extent be obtained in vertical tube 

 apparatuses by keeping the level of the juice one-third to one-half the height 



305 



20 



