CONTINUOUS PROCESS EVAPORATORS 169 



leaves openings at both ends of the vapor body for the vapors to 

 escape, the ends or heads of the vapor body being dished out- 

 ward. The vapor body also carries the milk inlet, vapor outlet 

 and spy glasses. 



The steam chest which is attached to the lower part of the 

 vapor body, is divided by a solid partition into two compart- 

 ments. The upper and larger compartment is filled with tubes 

 which are expanded in the fine-sheets, closing both ends. The 

 tubes themselves are open at both ends. They are two inches 

 in diameter and from six to eight feet long. The lower and small 

 compartment, called the downtake. is entirely open at both ends. 

 The steam chest is equipped with a steam inlet, a liquor outlet 

 and a condensation outlet or drip. The steam is around the 

 tubes and the milk is inside the tubes. 



Operation. This machine is operated under vacuum of from 

 26 to 28 inches mercury column, the vapor outlet being connected 

 with a condenser and vacuum pump. 



The fluid milk enters the vapor body and flows down into 

 the bottom of the downtake of the steam chest, from where it 

 rises in the tubes and finds its level. The level of the milk in 

 the tubes is kept low, the coefficient of the heat transmission 

 being highest when the milk level in the tubes is about one- 

 third of the tube length above the lower flue-plate," and it is 

 regulated by automatic float controls in the larger machines. 

 The steam that is turned into the steam chest, causes the 

 milk in the tubes to boil. The vapor thus arising from the 

 milk, together with a portion of the milk, rises and passes 

 through the upper part of the tubes at a very high speed, 

 and is thrown with great force against the ribs of the baffle 

 plate which extends across the whole cylindrical length of the 

 vapor body. 



The liquid or condensed milk returns through the down- 

 take to the lower part of the steam chest where it escapes from 

 the machine. The vapor passes at both ends of the baffle plate 

 into the vapor space above and from there through the entrain- 

 ment separator for reclaiming escaping milk, and then to the 

 condenser attached to the outlet of the vapor body. 



The upper part of the tubes becomes covered with a climb- 

 ing film of milk. .-This together with the high speed of the 



