SWEETENED CONDENSED MILK CONDENSING 



71 



circulation of the milk over the heating surface is indispensable. 

 It is further obvious that the rapidity of evaporation is in direct 

 relation to the area of the heating- surface. 



Rapidity of circulation of the milk demands that there be 

 no hindering counter currents and that the milk be permitted 

 to circulate with maximum freedom in one direction. This can 

 best be accomplished by leaving a large open space in the center 

 for the milk to return to the bottom after it has boiled up and 

 over the coils from the periphery. 



In order to have the coils so ar- 

 ranged as to permit this maximum and 

 unhindered circulation of the milk, the- 

 pan must have a certain height or 

 depth, so as to admit the necessary 

 heating surface. 



With the growing recognition of 

 these principles, vacuum pan manufac- 

 turers are therefore more and more 

 tending toward the style of pan with a 

 tall body in proportion to its diameter. 

 The vacuum pan consists of four 

 main parts, namely, the jacket or bot- 

 tom, the body or vapor belt, the dome 

 and the condenser. 



The Jacket forms the bottom of 

 the pan. The inside wall is copper, the 

 outside cast iron. It generally is con- 

 cave, the curve varying in different 

 types of pans from a depth of a few 

 inches to two and one-half feet. The 

 steam space in the jacket between 

 inner and outer walls is about two 

 inches wiide. It is equipped with two 

 steam inlets and one or two steam 

 outlets. In some pans some or all of 

 the steam outlets of the coils also ex- 

 haust through the jacket. 

 In the center of the bottom there is an opening, from two 

 to three inches in diameter, for the discharge of the condensed 



Piff. 18 

 Vacuum pan and condenser 



Courtesy of C. E. Rogers 



