ARTIFICIAL DRYING OF FORAGE CROPS 



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15 



Water evaporated to produce a ton of dried 



material (hundreds of pounds) 



Figube 8.— Quantities of water evaporated, and loss in weight, in drying hay from and to different 



moisture contents. 



under some conditions, it may be misleading unless reference is also 

 made to the initial moisture content and kind of forage dried. 



Forage driers may be obtained with rated capacities ranging from 

 approximately 1,000 to 6,000 pounds of water per hour. However, a 

 machine capable of evaporating 3,000 pounds of water per hour 

 approaches the lower limit of capacity for practical purposes under 

 the conditions hay driers are usually operated in the United States. 



FURNACE AND FUELS 



A properly designed furnace of ample size is important for a forage 

 drier, as air much in excess of that required for complete combustion 

 is drawn through the furnace. The capacity of the furnace should be 

 large enough, and the size of the openings great enough so as not 

 unduly to increase resistance to the flow of the drying gases. With a 

 drum drier the air requirements at the discharge fan are taken roughly 

 as the equivalent of 1.2 cubic feet of dry air per minute per pound of 

 water evaporated per hour. Since the temperature of the drying gases 

 at the discharge end is in the neighborhood of 250° F. and that at the 

 drier inlet is about 1,500°, the inlet volume is about three times greater 

 than the volume at discharge. Therefore, a dryer with an evaporative 

 capacity of about 3,000 pounds of water per hour should allow the 

 passage of about 10,800 cubic feet of air per minute at the inlet. # The 

 entrance velocity should not greatly exceed 1,500 feet per minute. 



