MECHANICAL REFRIGERATION 375 



Some open vats have a jacket and special open space at one 

 end for holding crushed ice. These vats will control and hold 

 temperature better than those that simply have a jacket around 

 them. The cooling of cream on a large scale by circulating ice- 

 water through the jacket is, at best, a slow process, usually too 

 slow to be effective and practical. 



This cooling process is carried out by mixing the ice and 

 water together in a separate vat to which a rotary pump is 

 attached, forcing the water through the jacket and again return- 

 ing it to the ice and water- tank to be cooled. The slowness of 

 this cooling process can in a measure be overcome by mixing salt 

 with the ice and water. This will cause the ice to melt faster, 

 and consequently cool the brine to a lower degree of temperature 

 than it is possible to obtain with water and ice. 



In case it is desirable, a set of coils can be made which will 

 fit into the open vat. The inlet and outlet of these coils can be 

 connected by means of rubber hose with the pipes conveying the 

 brine to and from the ripener. The coils can be made to move 

 up and down, by means of a rope attached to and leading from 

 the coils through a pulley near the loft and fastened to a small 

 crank at the end of a shaft. When the shaft turns the crank 

 will also turn and cause the coils in the vat to move up and down. 

 In the absence of a special up-to-date ripener, this manner of 

 cooling works very satisfactorily. 



A butter refrigerator containing a tank, as already described, 

 could be cooled by pumping brine through it in a similar 

 manner, as described for cream cooling, except that no coils are 

 needed. 



MECHANICAL REFRIGERATION 



Application in Creameries. Mechanical refrigeration on a 

 small scale has been considered expensive and impracticable 

 until within recent years. The science of producing cold arti- 

 ficially has been simplified and reduced to such a practical 

 basis that it is now used in many large plants as well as in smaller 

 plants where formerly natural ice was used altogether. Where 

 at least 10,000 pounds of milk, or its equivalent in cream. 



