Rotary single shaft type, German type of vertical and disc type drying ovens and the like have been used in Japan as drying ovens for sands. But because of the inferior of contact between combustion gas and sands, the efficiency of these types of ovens is very low. Based on the results announced in Repts. 1 and 2, the authors made a new type of drying oven as a trial and shall explain the mechanism and the efficiency of this oven hereafter. This oven is designed applying the air stream drying method and this time the reverse stream system is adopted on drying.
  The structual design of the oven is illustrated in Figs. 1 and 2. The sands slip down onto conical type blades and they are scattered off by rotation. By this rotating action, the sands fall down from all circumferences of the blades and they form the shower of sand grains. Combustion gas forced into the sand shower by means of an exhaust blast machine and this makes the contact between sand grains and hot air stream effectively.
  The sand dried by means of drying ovens heretofore used has a temperature around 100°C.
  If the treated sands have a higher temperature, it seems unfavorable in the point of heat or time lose. To prevent this defect, the cooling air is introduced into the machine from its bottom to cool the heated sands. This is also helpful to lessen the humidity stuffed in the oven. By the effectiveness of the cooling air, the temperature of the sand dried by this oven was about 25°C. The drying efficiency of already existing oven is said about 15∼40% and in the most preferably designed one, it is about 67%.
  But this newly designed oven gives very good result and its efficiency reaches about 69%.

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