36 CIRCULAR 74 0, U. S. DEPARTMENT OF AGRICULTURE 



Incidental Heat 

 Motor : B. t. u. per day 



Brine pump: 2% hp.X3,000 B. t. U.X24 hr 180,000 



Fan: 10 hp.X 3,000 B. t. U.X24 hr 720,000 



Conveyor: 1 hp.X 3,000 B. t. U.X24 hr 72,000 



Infiltration, workmen, etc. : 288,000 B. t. u. per 1,000' boxes received 



(estimated) X3 864, 000 



Total 1, 836, 000 



Recapitulation 



Field heat__ 4, 455, 000 



Heat of respiration 1,575,000 



Building-heat leakage 559, 640 



Incidental heat 1, 836, 000 



Total heat load 8, 425, 640 



Refrigeration required : 8,425,640-^-288,000, or 29.3 tons. 



The greatest demands for refrigeration, as will be seen from this 

 example, come from (1) field heat, (2) heat of respiration, and (3) 

 infiltration and workmen, which are directly related to the volume 

 of fruit being received and cooled each day during the peak of the 

 harvesting season. To cool this fruit promptly for late keeping it 

 is essential to have this reserve of refrigeration for a comparatively 

 short time. After the receiving season, when the fruit has been 

 cooled to 32° F., the heat of respiration from 50,000 boxes of apples 

 would require only 3.5 tons of refrigeration, and this added to build- 

 ing-heat leakage and heat of motors for fan and brine pump would 

 demand only 8.7 tons of refrigeration. As the weather becomes cooler 

 the building-heat loss is reduced, resulting in still smaller refrigera- 

 tion demands. In climates where day temperatures range from 55° 

 to 75° during the harvest season the refrigeration requirements may 

 be roughly estimated at 8 tons for each 1,000 bushels (packed boxes) 

 received into storage daily, in addition to refrigeration needed for 

 building-heat loss and heat from motors. If the quantity of fruit is 

 measured in field boxes, the requirement per 1,000 is about 6.5 tons, 

 instead of 8, since the field boxes contain less fruit. 



COLD-STORAGE DESIGN 



In laying out a cold-storage plant the first consideration should be 

 efficient refrigeration of the fruit, followed by efficiency and economy 

 in handling it. These requirements do not always permit the lowest 

 cost in construction and operation. An insulated building in the form 

 of a cube — dimensions equal for length, width, and height — repre- 

 sents the minimum requirements for materials in walls and the least 

 outside exposure for heat transfer. Buildings of different dimensions, 

 however, usually are necessary for the practical considerations of re- 

 ceiving, shipping, segregating, and piling the fruit and for the effi- 

 cient use of labor. Lay-out and design will be influenced also by other 

 factors, such as precooling requirements. Figure 10 illustrates an 

 arrangement of a packing and cold-storage plant for apples and 

 pears. 



