APPLICATION OF REFEIGEEATION TO HANDLING OF MILK. 87 



is not available and the cost of manufactured ice is too great for 

 economical use, mechanical refrigeration is desirable in order to reduce 

 the temperature of the cream to a point where it can safely be carried 

 to the main creamery. 



Due to the development of the hand separator, by the use of which 

 the farmer is enabled to separate his milk on the farm, the auxiliary 

 creamery is fast being done away with. This arrangement, however, 

 places the responsibility of properly cooling the cream upon the 

 farmers before it is hauled or shipped to the creamery. What has 

 been said on the subject of cooling milk on the farm is, of course, 

 applicable to the cooling of cream, and as the weight of cream is only 

 about 13 per cent of that of the whole milk, the cooling is a com- 

 paratively easy matter. 



Where the separating is. done at the auxiliary creamery the milk 

 is first heated to about 90° before being run through the separator. 

 The temperature of the cream is first reduced by the well-water section 

 of the cooler to approximately 60°. 



Assuming that the auxiliary creamery handles 1,500 pounds of 

 cream daily through the summer months, and the temperature of the 

 cream when received is 60°, and that it is cooled to an average tem- 

 perature of 40°, the refrigeration necessary to cool the cream is 

 1,500 X .90(60-40) =27,000 B. T. U. But there is the loss in cooling 

 brine, radiation, etc., that must be taken into consideration. 



Owing to the variation due to poor workmanship, the arrangement 

 of the apparatus, etc., it is impracticable to calculate very closely on 

 the amount of refrigeration that will be lost. Therefore it is cus- 

 tomary to allow a certain amount to cover this loss, which usually 

 varies from 25 to 50 per cent. In the case under consideration 25 pei 

 cent would be ample. During the summer months the machine 

 would be run about 6 hours per day; therefore the size of machine 



,,, 27,000X1.25X4 _ r + 



necessary would be — ----- - =0.5 ton. 



2oo,UUU 



A cubic foot of calcium-chlorid brine will absorb about 52 B. T. U. 



in rising 1° F., and allowing a 10-degree rise in brine, 30 to 40 degrees, 



each cubic foot will absorb 52 (40 - 30) = 520 B. T. IT. Therefore the 



27 000 

 volume of brine required for cooling the cream is — '— =52 cubic 



feet, providing the machine is not running during the cooling process. 

 But with the machine in operation the volume of brine will be con- 

 siderably less. A half- ton machine is capable of extracting 6,000 

 B. T. U. per hour. Consequently as the machine is run during the 

 two hours of cooling it will extract 12,000 B. T. U. and the volume 



-,'. .Vt, (27,000X1.25) -12,000 ^ ,. , x 

 or brine necessary will be - — = 41.8 cubic feet. 



As the amount of heat that will come through the walls of the brine 

 tank is directly proportional to the exposed outside surface, and as 



