16 



CIRCULAR 443, U. S. DEPARTMENT OF AGRICULTURE 



Table 4. — Operating data for drying alfalfa and for drying oats- 



FIRST SEASON 



Crop 



Dura- 

 tion of 

 test 



Temperature of 

 drying air 



Inlet 



Exit 



Weight of forage 



Enter- 

 ing 



Dis- 

 charge 



Moisture' con- 

 tent^ forage 



Enter- 

 ing 



Dis- 

 charge 



Water 

 evapo- 

 rated 



Loss in 

 weight 

 of for- 



Oats-brome-alfalfa mixture. 



First cutting alfalfa 



Second cutting alfalfa 



Third cutting alfalfa: 



Test No. 1 



Test No. 2 



Hours 

 6.16 

 5.80 

 8.38 



2.04 

 1.40 



650-880 

 400-600 



°F. 



270-290 

 255-270 

 270-290 



240-265 

 210-245 



Pounds 

 10, 816 

 11,119 

 14, 662 



3,591 

 2,515 



Pounds 

 3,850 

 2,779 

 4,141 



1,415 

 1,243 



Per- 

 cent 

 66.9 

 74.6 

 73.8 



63.6 



Per- 

 cent 

 13.0 

 12.4 

 9.1 



8.3 

 7^2 



Pounds 

 6,739 

 7,949 



10, 448 



2, 167 

 1,167 



Per- 

 cent 

 64.4 

 75.0 

 71.8 



SECOND SEASON 



Second cutting alfalfa __ 



Third cutting alfalfa 



15.36 

 5.45 



700-1300 

 850-1300 



240-295 

 250-295 



38, 179 

 14, 009 



13, 440 

 4,238 



64.5 

 66.9 



6.4 



5.7 



23, 766 

 9,134 



64.8 

 69.7 



reduced to about 55 percent. Under such conditions it will be neces- 

 sary for the machine to evaporate 2,089 pounds of water to produce a 

 ton of hay at 8 percent moisture. In the latter case the capacity of the 

 drier in tons of hay per hour may be twice as great as with 70 -percent 

 moisture-content forage. 



The capacity of a drier will depend also somewhat upon the kind of 

 forage, the degree of processing before it is fed to the machine, and the 

 condition of the air entering the drier. When drum driers are used, 

 the fineness and uniformity of chopping greatly influence the perform- 

 ance of the machine. Alfalfa, some varieties of clover, and meadow 

 grasses usually dry much more easily than soybean hay or other coarse- 

 stem plants. The capacity of a drier is frequently referred to in terms 

 of tons of dried material delivered per hour. Although this method 

 gives an indication as to what tonnage may be expected 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 12,000 pounds of water per hour. 



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 to not 

 unduly 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 about 250° F. and that at the drier inlet is about 



