APPLICATION OP REFRIGERATION TO HANDLING OF MILK. 75 



ization takes place or in separate holding tanks arranged for the pur- 

 pose, after which it flows to the coolers. 



In the "flash," or continuous, process the milk flows from the 

 receiving tank to the pasteurizer, where it is heated to a temperature 

 of from 160° to 165° F. in from 30 seconds to a minute, and from 

 thence to the coolers, where it is cooled. 



It is obvious, therefore, that there is more refrigeration required 

 for a given amount of milk or cream in the latter, or "flash," than in 

 the former, or "holder," process. It is advisable, however, in both 

 the "flash" and "holder" processes of pasteurization to install be- 

 tween the heater and the cooler a regenerator or heat exchanger, in 

 which the heat is transferred from the hot milk leaving the heater to 

 the cold incoming milk; consequently the milk entering the heater 

 is thus heated while that entering the cooler is partly cooled, the cooler 

 proper reducing the temperature to the point desired. 



The milk coming from the regenerator enters the cooler at an 

 average temperature of about 88° F. and is reduced by the wa.ter 

 section of the cooler to about 75° F. It then enters the brine section 

 of the cooler, where the temperature of the milk is lowered to an 

 average of 45° F. by low- temperature brine circulated through the 

 coils of the cooler, or in some cases by direct expansion of the refriger- 

 ant in the coils. The cooled milk then flows from the cooler to the 

 bottler, where it is bottled and capped, after which it is stored in a 

 refrigerated room and allowed to remain overnight. As the tempera- 

 ture of the storage room is around 32° F. the milk is further reduced 

 to approximately 35° F., at which it goes on the wagons the following 

 morning and is delivered to the consumer. 



The work required of the refrigerating machine in a plant of this 

 kind is that necessary to reduce the temperature of the milk from 

 about 75° F., the temperature at which it leaves the water section 

 of the cooler, to, say, 45° F., the temperature at which it leaves the 

 brine section of the cooler, and that necessary for further cooling the 

 milk after it is placed in the cold storage room ; also that required 

 to take care of the heat that comes through the insulated walls of the 

 storage room and in lowering the temperature of the glassware and 

 bottle cases. The heat that will come through the walls of the room, 

 of course, depends upon the size of the room, the quantity and quality 

 of the insulation used, and upon the temperature of the outside air. 



Assuming a plant handling 1,000 gallons of milk daily, the size 

 of the storage room necessary will be approximately 12 by 13 by 

 12 feet, with an anteroom, say 6 by 12 feet, giving a total square 

 foot surface of 1,316. If the walls, floor, and ceiling are insulated 

 for a heat transmission of 2 B. T. U. per square foot per 24 hours, 

 for each degree difference between the inside and outside tempera- 

 tures, and if the average outside temperature is 80° F., then the 



