156 



REFRIGERATION AND ITS USES 



while the warmer, lighter air passes upward at the other 

 side. In the side-icing refrigerator the air current is evidently 

 always downward on the ice side and upward on the food side 

 (Fig. 119). The top-icing refrigerator usually affords a much 

 larger ice capacity compared with the food capacity than does 

 the side-icing refrigerator. On this account, when both 

 ice boxes are filled, we should expect a somewhat lower tem- 

 perature in the top-icing than in the side-icing refrigerator. 

 On the other hand, since in the side-icing refrigerator the food 

 compartment extends the entire height of the refrigerator, the 

 columns of cold air and of warm air are considerably higher 

 than is possible in the top-icing refrigerator of the same 

 capacity. This insures very perfect circulation, which is an 

 essential feature of a good refrigerator. 



185. Temperature Obtained and the Cause of Circulation. 

 In a good refrigerator well filled with ice, the temperature of 

 the air as it leaves the ice compartment and enters the food 

 compartment is usually from 40 to 45F. As the air leaves 

 the food compartment and enters the ice compartment, its 

 temperature is often raised to 55 or even 60F. This differ- 

 ence in temperature is the cause of the circulation, the warmer, 

 moist air being considerably lighter per cubic foot than the 

 cooler, dry air (Arts. 130-137). 



TABLE VII. WEIGHT OF 1 Cu. FT. OF AIR SATURATED WITH 



WATER VAPOR; ALSO, WEIGHT OF THE WATER VAPOR IN EACH 



CUBIC FOOT OF AIR 



