378 COOLING FACILITIES FOR CREAMERIES 



can again be absorbed when it expands into gas at the lower 

 pressure. 



3. This liquefied gas, which is still under great pressure, is 

 then admitted through what is termed the expansion- valve. 

 This valve is especially constructed for that purpose, and has 

 only a very minute opening in it for the admission of the liquid 

 ammonia. On the expansion side the pressure is low (20 to 

 30 pounds). As the liquid ammonia emerges from the high- 

 pressure side through the expansion-valve into the expansion 

 side, it forms a gas. This expanded gas may then be circulated 

 through coils for cooling purposes. From there it passes back 

 into the suction side of the compressor ready to go through 

 another similar cycle. 



From the above description it will be seen that there are two 

 sides to the system, the expansion side and the compression 

 side. The compression side extends from the compressor to 

 the expansion- valve ; the expansion side from the expansion- 

 valve to the suction side of the compressor, inclusive. 



Transferring the Cold. The methods of transferring the cold 

 to the different places in the building vary. There are two sys- 

 tems, viz.: 



1. Direct Expansion. 



2. Brine System. 



1. By the direct-expansion system the condensing-pipes are 

 extended to the room or place at which the cooling is to be done. 

 An extended set of expansion coils then convey the gas which 

 absorbs the heat. A lower temperature can be produced by this 

 method than with the brine system. 



2. In the brine system a large brine- tank is placed some- 

 where in the creamery at a place most convenient with respect 

 to cooling. This tank contains a strong solution of brine. The 

 chief reason why brine is used in preference to water is that 

 brine has a very low freezing-point. This will vary with dif- 

 ferent degrees of saturation. 



Either one, sodium chloride (common salt), or calcium 

 chloride, may be used for brine. The latter is considered the 

 better chiefly because it is not so hard on the pipes and it keeps 



