THE REFRIGERATOR 



157 



This difference in weight of a cubic foot of air at the different 

 temperatures from 30 to 100F. is more clearly shown by the 

 curve, Fig. 120. If the temperature of the air in a refrigerator 

 varies from 40 on the ice side to 55F. on the food side, the 

 weight of 1 cu. ft. of air will vary from 556 grains to about 

 538 grains. This means that the warmer air is only about 

 2 %o as heavy as the cooler air. This difference in weight is 

 sufficient to secure a convection current of considerable 

 strength. 



FIG. 120. Curve showing density of air at different temperatures. 



Exercise 43. A Study of the Temperature in a Refrigerator 



(a) Open the doors of a refrigerator and study carefully its con- 

 struction. Is it top-icing or side-icing? If it is a top-icing refrigera- 

 tor, determine whether the cold air drops out of the ice bcx at the 

 center of the refrigerator or at one side. Also determine whether 

 the warm air enters the ice compartment at one side only or at both 

 sides. 



(6) Having determined the course of the convection currents in 

 the refrigerator, place the thermometer in this current close up to the 

 opening through which the air passes as it leaves the ice compartment 

 and enters the food compartment. Close all of the doors for about 

 five minutes; then open one door and quickly read the thermometer 



