324 



MARINE PRODUCTS OF COMMERCE 



32 °F (0°C) until delivery to the airport. The characteristics of the cartons are 

 such that the temperature inside rises approximately at the rate of3°F (1.7°C) 

 in 4 hours with an outside temperature of70°F (21.1°C). 



Fig. 15-4. Many ship- 

 ments of live lobsters are 

 made by airfreight. The lob- 

 sters are packed in specially 

 constructed, waterproof, cor- 

 rugated fiberboard cartons, 

 and covered with wet sea- 

 weed. In extremely warm 

 weather a tray of water ice 

 is added to keep the lobsters 

 cool. The cartons shown 

 above contain 50 lbs. of lob- 

 sters and have a gross 

 weight of 70 to 75 lbs. when 

 packed. Otlier sizes of car- 

 tons are available. 



( Courtesy A merican Airlines, Inc. ) 



Factors AfiFecting the Rate of Ice Melting 



In view of the wide appUcation of ordinary ice in the preservation of fishery 

 products before, during, and after the transportation episodes it might be profit- 

 able to review the factors that are held to affect the rate of ice melting and bring 

 to the reader a few observations covering these factors. For ease of discussion 

 and clarity the factors will be considered under separate sections as follows: 



Temperature of the Surrounding Air. Since the melting of ice is a purely physical 

 change involving an exchange of heat between surrounding media (fish, air, etc.) 

 and the ice, the rate of melting will vary directly with temperature difference 

 between the ice and the surrounding media, all other factors being equal. This 

 is known from elementary physics, and for most practical calculation the qualifica- 

 tion "all other factors being equal" can be ignored. More precise calculations, how- 

 ever, must take account of these other factors. 



Size of Ice Particles. Considering again the change in phase as caused by an 

 exchange of heat, we may observe that for a given temperatiire difference be- 

 tween surrounding media and ice the rate of melting will depend upon the ex- 

 posed area of the ice, or, in other words, upon the size of the ice particles, wdth 

 the qualification that all other factors be kept the same. This, also, is elementary, 

 and was a reason that used to be given by some fishermen when they demanded 



