HOME REFRIGERATION 5 



could be read. Thus the percentage of running time and power consumption 

 could be calculated for each refrigerator in order to ascertain that they were 

 functioning properly. 



Temperature 



Recording thermometers were used to record the changes in temperature both 

 in the room and in the refrigerator cabinets. Thermocouples were also used to 

 measure the temperature at different locations within the refrigerators and in 

 the room. 



For room temperature measurements, thermocouples were set eight feet, four 

 feet, and ten inches above the floor between the two refrigerators. For the de- 

 termination of temperatures in the refrigerator, a thermocouple was placed in the 

 center and about two inches above each shelf; two other thermocouples were 

 placed in the lower chamber of the freezing compartments, one centered on the 

 back wall, the othei* suspended one inch from the roof directly in the center of 

 the chamber; two additional thermocouples were placed in the freezing com- 

 partment to be inserted in the frozen food cartons placed therein. 



The evaporator (freezing coils) temperatures were measured by means of 

 special thermocouples, the junctures of which were soldered to small flat copper 

 plates so that the thermocouple could be placed directly in contact with the sur- 

 face of the coils. These were placed on the top and bottom coils of the freezing 

 compartment. 



All thermocouples were connected to a selector switch which in turn was con- 

 nected to a potentiometer. The potentiometer was checked against a standard 

 mercury thermometer before readings were taken. 



Humidity 



Different degrees of relative humidity within the refrigerators were obtained 

 by the use of closed containers and by varying the refrigerator loads and door 

 openings. The relative humidity measurements were made by means of wet bulb 

 thermocouples which consisted of thermocouples wound with a wick of un- 

 bleached linen and mounted, together with a well, on small stands. The wet 

 bulbs were standardized by means of a sling psychrometer at room temperature 

 to within 1°F. and the correction taken. At least three of these thermocouples 

 were used in each refrigerator and the lowest readings were employed. When a 

 wet bulb appeared to be "off" it was removed from the cabinet, checked with a 

 sling psychrometer and rewound, if necessary. 



Relative humidity readings were made at the beginning and end of at least 

 two consecutive periods when the refrigerator motor was in operation, and the 

 mean temperature and humidity calculated. The readings were made after the 

 refrigerator doors had not been opened for at least six hours so that the cabinet 

 had had time to reach a constant temperature. 



Dehydration 



Loss of moisture was determined by weighing the samples directly, in their 

 containers, to the nearest tenth of a gram. The amount of dehydration of the 

 foods themselves, in the tests on "left-overs", was ascertained by the change in 

 moisture content. Moisture determinations were made by drying the samples at 

 135°C. in an electric air oven, according to the A. O. A. C. (1940) method. 



