MECHANICAL REFRIGERATION 



209 



of controlling the temperature during the warm summer 

 months. 



The brine is kept circulating by means of a brine pump. 



Strength of Brine. The brine is usually made from 

 common salt (sodium chloride). The stronger the brine 

 the lower the temperature at which it will freeze. Its 

 strength should be determined by the lowest temperature 

 to be carried in the brine tank. The following table from 

 Siebel shows the freezing temperature as well as the 

 specific heat of brine of different strengths: 



Percentag-e of salt by weig-ht. 



1, 



2, 

 3, 

 4, 

 6. 

 8. 



10, 



12. 



15. 



20. 



25. 



26. 



Specific 

 heat. 



.992 

 .984 

 .976 

 .968 

 .946 

 .919 

 .892 

 .874 

 .855 

 .829 

 .783 

 .771 



The fact that the specific heat grows less as the brine 

 becomes stronger shows it to be wise not to have the 

 solution stronger than necessary, because the less the 

 specific heat the less heat a given amount of brine is able 

 to take up. 



Refrigerating Capacity. When speaking of a machine 

 of one ton refrigerating capacity, we mean that it will 

 produce, in the course of twenty-four hours, the amount 

 of cold that would be given off by one ton of ice at 2>^° F. 



