VEGETABLE AND FRUIT DEHYDRATION 



91 



More recently several cabinet dehydrators equipped with propeller- 

 type fans have been designed. One of these designs, which was 

 developed for use by State and Federal institutions, is illustrated in 

 figure 51. Double-walled sides and top are made up in such a manner 

 that the sections can be bolted to form a portable unit, and these 

 sections are insulated to prevent excessive heat losses. A four-blade, 

 laminated- wood propeller, 5% feet in diameter, is driven at 600 r. p. m. 



n.O On Heater 



-gooo 



Y"§-s-- 7l 



v. - ■ v . 



Damper 



Wet- and 

 Dry-Bulb 

 ■I Thermometers 



Figure 51. — Cross-blower cabinet debydrator employing airplane propeller. 



to deliver 800 to 1,000 feet of air per minute as a suction air flow. 

 Four sets of stationary duct turns are installed to insure a uniform 

 air flow through the trays. Steam-heated fin-type coils or iron-pipe 

 radiators make ideal heating units for this type of cabinet, although 



An intake-exhaust damper is 



direct gas heaters can be used also 



PROPELLER FAN 



Figure 52. — Stearn-beated single-truck cabinet debydrator. 



provided for air recirculation and humidity control. Slanting trays 

 may be used to direct the air down through the food material rather 

 than horizontally across it. 



If trucks fitted with guide rails are used, the rails can be so arranged 

 that the trays are slid into the truck in a slanting position. If the 

 trays are to be stacked one on top of the other, the screen bottoms 

 can be built into the wood frames in a slanting position^ 



With another type of cabinet dehydrator, which uses a propeller 

 fan, an entirely different method of air distribution is utilized, as 

 illustrated in figure 52. The propeller is mounted on one side of the 

 cabinet directly behind a steam-heated fin-type coil. The air flow is 

 heated by means of the steam coil and forced through a series of curved 



