1 52 MANAGEMENT OF DAIRY PLANTS 



The amount of heat which will be conducted per second 

 through one square centimeter of copper one centimeter in 

 thickness when the difference in temperature on the two sides 

 of the copper wall is one degree Fahrenheit is equal to 



0.72 X -r- = 0.40 calorie. 

 180 



The amount of heat in B. T. U. which in one second is 

 conducted through one square centimeter one centimeter thick 



is equal to -^ B. T. U. with a difference in temperature of one 



252 



degree Fahrenheit. 

 The value of K is equal to ' 



£dHx^^:54)! = 0.004 B.T.U. 

 252 2.54 



Example: 



Determine the amount of milk which should be pasteurized 

 per hour when using a pasteurizer of 1,400 square inches heat- 

 ing surface; thickness of copper, 0.05 inch. The temperature 

 in the steam chamber is 212° F., the average temperature of 

 milk in pasteurizer, 152° F. and the milk is heated from 60° F. 

 to 180° F. 



Answer: 



0.004X1,400X60 -D T- TT 



Q = : X 3,000 = 24,192,000 B. T. U. 



0.05 



Amount of milk to be pasteurized = 



24,192,000 



\ = 214,468 pounds. 



120 X .94 



n. Factors Reducing the Efficiency of a Pasteurizer. — 



From the above problem it is evident that the theoretical 

 eflBciency is not obtained in practical work. About one per 

 cent of the theoretical efficiency is as much as may be expected 

 when using a pasteurizer of a continuous type. By this it is 

 not understood that ninety-nine per cent of the heat is lost, for 



' One inch is figured as being equal to 2.54 c. m. 



