30 



CIRCULAR 74 0, U. S. DEPARTMENT OF AGRICULTURE 



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parts of a room, but there are times during the season, as fruit is 

 shifted or loaded out, when this is possible. In many cases, if tem- 

 perature conditions are known, steps can be taken to make them more 

 uniform. When fruit-temperature readings are not taken, it is often 

 assumed that the thermometer in an aisle shows temperatures that 



prevail throughout 

 the room. This is not 

 true, and wide tem- 

 perature variations 

 may occur, especially 

 for the first feAv weeks 

 of storage. 



THERMOCOUPLE 



In large plants 

 there are often inac- 

 cessible parts of the 

 cold-storage rooms 

 where it is not possi- 

 ble to take tempera- 

 tures with ordinary 

 thermometers. Here 

 thermocouple equip- 

 ment is useful. The 

 wires of this instru- 

 ment may be strung 

 from the center of 

 piles where actual 

 fruit temperatures are 

 desired and readings 

 made in aisles or in the 

 compressor room. 

 Figuee 8. — Thermocouple equipment for reading fruit Thermocouple equip- 

 temperatures at remote parts of cold-storage ment suitable for cold- 

 rooms. The wires may be installed for reading Qfnrnap ' ; Q en™ 

 temperatures at a central point, or the reading &lUia i? e 1 " &e ±& lilus 

 instrument may be carried from room to room. trated ill figure 8. 



Required Capacity of a Refrigeration System 



The storage season may be divided into two distinct periods. The 

 first is during the harvest, when warm fruit is being put into the plant ; 

 the principal problem is cooling the fruit, or removing the field heat. 

 The second is the holding period, when the main problem is maintain- 

 ing low temperatures as uniformly as possible. The heat load during 

 this period is relatively low, consisting of the respiration heat gener- 

 ated by the fruit, the heat entering through the walls, and heat from 

 workmen, power equipment, lights, air entering from outside, and 

 other incidental sources. 



NATURE OF HEAT 



A discussion of the heat from various sources that has to be removed 

 by a refrigeration system is necessarily more or less technical and 

 includes terms that may not be familiar to all readers. It is not diffi- 



