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 flue-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 Hquor 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 
20 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 hquid 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 
