COLD STORAGE FOR APPLES AND PEARS 39 



Since the compressor room is a source of heat, placing it at one side 

 of the cold-storage building (see plan, fig. 10) eliminates the cause of 

 a warm spot, especially at the floor of the room above. It also makes 

 machinery more accessible when it has to be replaced and lessens the 

 risk of loss of machinery in case of fire, or of damage to the fruit when 

 ammonia leaks occur in the compressor room. When the room is given 

 space in the basement of the cold-storage building, as is frequently 

 done, there is a tendency to limit it to minimum dimensions, thereby 

 entailing difficulties when later it is desired to expand and to install 

 additional compressors. 



Where brine-spray chambers are used, there are several advantages 

 in placing them in an insulated penthouse^ on top of the building. 

 There is the decided advantage of being able to place the chamber 

 centrally with plenty of room for spacious ducts without infringing 

 upon the most desirable space for fruit storage. Having ample space 

 in the brine-spray room permits the effective elimination of spray 

 before the air enters the cold-storage rooms, allows the use of large 

 fans with slower turning impellers, gives space for reversing the direc- 

 tion of air flow without short turns, and provides good working condi- 

 tions for adjusting the brine concentration and servicing the equip- 

 ment. There is less corrosion of the fan when it delivers the air to 

 the brine-spray chamber than when it draws it from the spray. 



Fans and Ducts 



The efficiency of a refrigeration system depends to a great extent on 

 the effective movement of heat from the fruit to the evaporation coils 

 or the brine spray. The fan and air ducts should move the greatest 

 possible volume of air at the smallest possible cost of power. Two 

 reasons for keeping the fan-power requirements at a minimum are 

 that (1) the fan operates over a long period in the year, so that any 

 reduction in the cost of power to drive it is an important item; and 

 (2) the power used on the fan adds heat to the circulated air, thus 

 adding to the refrigeration load and reducing the useful capacity of 

 the refrigerating machinery. Each horsepower used on the fan puts 

 a load of 0.2 to 0.3 hp. on the compressor motor. 



It is false economy to have a fan of lower capacity than necessary 

 to circulate the required volume of air ; but it is true economy to have 

 fan and ducts so designed as to move the required volume of air with 

 the least possible power. Many plants are handicapped by having 

 a fan too small or ducts with too much air resistance. Increasing 

 the speed of a fan to get more air circulation is at the cost of more 

 power for every cubic foot of air circulated. For this reason it pays 

 to install an efficient fan having the required capacity at a moderate 

 speed. The fan motor should have more than one pulley, so that the 

 speed of the fan may be reduced after the fruit has been cooled down, 

 provided the split between the delivered and returned air can be kept 

 down to 1.5° F. at the slower speed. 



RESISTANCE IN AIR DUCTS 



The design of air ducts has an important bearing on the volume of 

 air that can be circulated by a blower, the volume circulated becoming 

 less as the resistance in the ducts increases. The resistance to air flow 



