COLD-STORAGE METHODS 



Air compressing and expanding machines are represented, diagrammati- 

 cally, by fig. I, where A is the chamber to be cooled, B a compression 

 cylinder driven by power, c a cooler, and D an expansion cylinder whose 

 piston is operated by the air which has been previously compressed in B. 

 This pump, after drawing air from A, compresses it to three or four 

 atmospheres, the mechanical energy thus exerted being simultaneously 

 converted into heat. The compressed and heated air passes through the 

 cooler C, into the expansion cylinder d, where it assists the driving agent, 

 as already indicated. Upon the final discharge of the cooled and expanded 

 air into the chamber A, it abstracts heat from the atmosphere therein. 



Machines working on the principle of evaporation and condensation by 

 compression of a volatile liquid are represented, diagrammatically, in fig. II, 

 where A is again the chamber to be cooled, b a compressor driven by 

 power, c a condenser, and d the refrigerator, the two latter vessels con- 

 sisting of coils of pipe charged either with ammonia or carbonic acid, both 

 highly volatile substances, of which, however, the former is more generally 

 used. The ammonia enters the refrigerator as a liquid, and, rapidly eva- 

 porating within its coils, abstracts heat in so doing from the atmosphere 

 filling the chamber a. The vapour thus generated in D is drawn into the 

 pump B, and there compressed to such a tension that, upon entering the 

 condenser, it assumes the liquid form. The condensed ammonia then 

 returns to the refrigerator D, through a regulating valve E. 



Fig. in represents, diagrammatically, a cold store having three floors of 

 chill-rooms; and here, as in the case of fig. II, ammonia, leaving the 

 compressor B, situated in the engine-room g, enters the condenser c, and, 

 passing as a liquid through the regulating valve e, becomes vaporized in 

 the refrigerator D, whose coils are submerged in a brine-tank F. Above 

 this tank, and occupying its whole length, two or more spindles, carry- 

 ing a number of plate-iron discs L, L, slowly revolve. The discs are about 

 2 feet diameter, X mcn thick, and set about % inch apart; their total 

 superficial area being considerable. They dip, as they rotate, into the cold 

 brine below, and emerge with damp chilled surfaces, over which a stream 

 of air is constantly impelled by the action of the fan H. The latter sucks 

 its supply through the openings J, J, J, from all or any one of the rooms 

 A, a, a, at will, and having urged it through the numerous narrow spaces 

 separating the discs L, L, from each other, delivers it again into the cold 

 chambers through K, K, k, both inlet and outlet apertures being furnished 

 with sliding shutters. A constant circulation of air results, and whatever 

 moisture arises from the goods stored in the chill-rooms is carried thence 

 by the outgoing current from the fan, condensed upon the cold surfaces 

 of the revolving discs, and by them transferred to the brine, which, 

 weakened by these fluid additions to its bulk, requires to be occasionally 

 dosed with salt. 



