352 The Commercial Apple Industry 



There are many better types of evaporators and its use is 

 not strongly recommended. 



Cabinet evaporator is heated by steam coils but other- 

 wise is very similar to the stack evaporator in construction 

 and operation. It has been used recently in New York 

 and Canada for vegetable and apple drying. 



Ceramic oven. The ordinary bake-oven principle has 

 been successfully applied in California. This type of 

 drier should permit of fuel economy as it is constructed 

 throughout of brick and fire brick. There is practically 

 no fire risk and radiation losses should be small. 



Electrically heated driers. Small evaporators for home 

 use have been designed in which an electric current passing 

 through resistance wires furnishes the necessary heat. 

 The drier is of the stack type. Except where electricity 

 is extremely cheap, it is doubtful whether such machines 

 would prove profitable, although a machine of recent de- 

 sign appears to have great possibilities. 



Forced draft evaporators. 



Most of the new driers on the market belong to this class. 

 The number of different forms is very great and is con- 

 stantly being added to. Their one common characteristic 

 is the forced air circulation. Outside of this one feature, 

 they are of almost every conceivable design. 



Horizontal tunnel. In general, this type consists of a 

 long chamber or tunnel resting on the ground with an air 

 heating system and fan so arranged that the heated air 

 may be blown or drawn over the trays. Usually the trays 

 are carried on trucks which enter the cooler end of the 

 tunnel and which leave the tunnel from the hotter end. 

 Great variation exists in the methods of heating the air. 



