DRYING BANANAS 139 



the air may be extracted by a fan. In order to secure that 

 the hot air penetrates in all directions, both inlet and outlet 

 should start at the bottom of the room. The inlet pipe 

 should come in as near the centre of the floor as possible. 

 The outlet pipes, of which there may be two or more, 

 should start near the floor at the greatest distance from 

 the inlet, and conduct the wet air to one junction outlet 

 pipe at the ceiling. This junction pipe should be provided 

 with a valve at its base, which may be opened to start the 

 draught, and then kept closed. If steam is employed for 

 heating, it is conducted by pipes near the floor on each 

 side of the room. The inlet openings are arranged along 

 the pipes, and the pipes are encased in partly grated casings 

 so that the incoming air may be brought into close contact 

 with the hot pipes. In this case the outlet pipes may have 

 their openings above the shelves on which the material to 

 be dried is placed. Spon * states that "the minimum size 

 of fresh-air duct and outlet shaft should be one square foot 

 area for every 500 c. ft. of space in the room (when 

 empty), this being a room, say, 8 ft. each way ; and the 

 outlet shaft should be at least twice as high as the room, 

 say 16 ft. or higher. With a higher shaft a smaller area 

 would suffice. These sizes are for drying rooms for a 

 laundry ; for substances of a drier nature, smaller ducts 

 and shafts, with a corresponding decrease in the air supply, 

 may be used." 



Blackmarfs Fans. The illustrations on p. 140 show a 

 building suitable for use with Blackman's fans and hot air. 

 The building is made of galvanized sheet steel ; one 

 measuring 40 ft. by 20 ft. by 12 J ft. will give a drying 

 surface of 5000 square feet. The shelves can be drawn out 

 on runners from one or both sides of the building, so that 

 the bananas can be sun-dried when the weather conditions 

 are favourable. 



In this type of drier the air is blown through the heaters 

 into the drying chamber by two fans, and then over and 

 under the trays on which the produce is spread. To 

 * " Workshop Receipts," i. 492 (1009). 



