12 CIRCULAR 44 3. U. S. DEPARTMENT OF AGRICULTURE 



1. Ill drying alfalfa I whole) on the apron-conveyor drier the aver- 

 age percentage loss in weight was about the same for the first and third 

 seasons. Not much forage was dried during the second season. The 

 power consumed per unit weight of material dried and per unit weight 

 of water evaporated was reduced in the third season from that shown 

 during the first season. The same held true for the heat requirements 

 of hue drier per unit weight of material dried and per unit weight of 

 wamr evaporated, although the hourly output and evaporation weight 

 did not show an increase. This more efficient utilization of power and 

 heat in the apron-conveyoi Irier was due to blowing the air counter- 

 on ent to the apron travel for the first half of the apron length. The 



intake and exhaust system on the apron-conveyor drier was arranged 

 so that the drying gases after first being forced through a section of the 

 api n might be drawn into a fan and then forced through another 

 section of the apron toward either the feed end or discharge end of the 

 o: ier. If the air moved toward the feed end, the counter-current sys- 

 tem was obtained; if toward the discharge end (fig. 5), the air moved 

 concurrently with the hay. The air velocity through the mat of forage 

 ranged from 80 to 150 feet per minute in all of these observations. 



2. When the apron-conveyor drier was used to dry chopped soybean 

 hay, the drying proved to be very uneven and poor, the average dis- 



ge moisture content being approximately 2 percent. At this 

 moisture content it is doubtful whether artificially dried forage will 

 keep in good condition, free from mold and spoilage. 



3. Gowpea hay in the apron-conveyor drier presented much the 

 some problem as to nonuniformity of drying as did soybean hay. 



■i. The data for the fourth season for the rotary drier were taken 

 when the material was further reduced by passing it through a hammer 

 mill after it had been cut in a silage cutter. The power requirements 

 oer 1,000 pounds of water evaporated were greater for drying soybean 

 h -- in the fourth season than in the third. The heat required per unit 

 rial dried was about the same, but the hourly evaporation was 

 increased trout 77 _i to S66 pounds, an increase of 13 percent. In drying 

 alfalfa there also appears to be or. increase in thermal efficiency as 

 well as caj acity of the drier due to the shredding of the undrie ', forage 

 with a hammer mill. 



o.l hen on the effect of maturity on power and fuel require- 



ments showed that the 120-day growth Otoe tan soybean hay required 

 slightly less power and fuel for dehydration than 80-day growth hay 

 of the same variety. This difference was not due to initial moisture 

 content of the green material. 



6. The thermal o icity for evaporating moisture was affected ma- 

 terially when the re rage was reduced to fine particles. The inner arts 

 of the forage plant :.oae in more direct contact with the drying gases 

 when chopped and shredded than when left whole, os they were hi the 

 - mveyor drier. 



Dal k men on several commei are operating on 



neighboring plantations. The performances of these driers are sum- 

 ized in table 3 under the headings of "Single-drum" and "Triple- 

 drum. 53 So far as the data show, the large commercial driers were 

 somewhat more efficient in the utilization of heat than the small 

 experimental units. 



