APPLICATION OP REFRIGERATION TO HANDLING OF MILK. 



27 



of the liquid is absorbed from the brine, which in turn is absorbed 

 from the air by the brine. In this case there is a double transfer 

 of heat, viz, from the air to the brine and from the brine to the 

 evaporating liquid in the test tube. The cooling effect is assisted 

 by the circulation within the brine itself, due to the difference in 

 weight of the colder liquid in contact with the surface of the test 

 tube, and that at a distance from it. The colder brine sinks to the 

 bottom of the vessel and its place is taken by the warmer brine, 

 thus producing a circulation as indicated by the arrows, whereas 

 in the preceding case the heat from the surrounding air was absorbed 

 directly by the re- 

 frigerant . In view of ^ ^ ' 

 the fact that it is im- 

 practicable to lower 

 the temperature of 

 the brine to that of 

 the refrigerant, the 

 absorption of heat 

 from the surround- 

 ing air by the brine 

 is not so rapid as 

 when the air is in 

 direct contact with 

 the walls of the ves- 

 sel as in the preced- 

 ing case. Figure 11 

 embodies the prin- 

 ciples of the commer- 

 cial brine-storage 

 system of refrigera- 

 tion, which will be 

 discussed later. 



Going one step f ur- 

 ther toward the 



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fc 



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f~h ~at*-r * -*f* ~r X 

 — VttV^/V -/- 



f 



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Fig. 11. 



practical application of artificial refrigeration, imagine an arrange- 

 ment as shown in figure 12, where the test tube in the foregoing 

 illustration is replaced by a steel cask or drum, such as is commonly 

 used for shipping ammonia, carbon dioxid, and other liquid gases, the 

 tank corresponding to the beaker containing the brine. The liquid in 

 the drum is under pressure, and if allowed to escape in a small stream 

 through the throttling or expansion valve against atmospheric pres- 

 sure it will evaporate in the coils located in the brine tank and the 

 heat required for vaporization will be taken from the brine. If a 

 pump were attached to the free end of the pipe the suction of the 

 pump would tend to produce a vacuum, which action would accelerate 



