90 



MISC. PUBLICATION 5 4 0, U. S. DEPT. OF AGRICULTURE 



Types of Cabinet Dehydrators 



To illustrate more clearly how these various parts are assembled 

 to form a cabinet and how they function, brief descriptions of several 

 types of cabinet dehydrators are included. Perhaps the most com- 

 mon type of cabinet drier is one similar to the design in figure 49. 



This cabinet is equipped with two or three centrifugal fans mounted 

 on a single shaft and propelled by one motor. Air is forced through 

 the fin-type steam coils and distributed through the trays by means 



47- 



Dry- and 

 Wet-Bulb 

 Thermometers 



;g Heater 

 \ 



Troys 



5C 



J 



Y V I 



Dry-Bulb 

 Thermometer 



Figure 49. — Cabinet dehydrator equipped with centrifugal fans and steam-heated 



fin-type coils. 



of adjustable louvers. Unless duct turns, baffles, or adjustable louvers 

 are provided in this type of cabinet, most of the heated air will be 

 forced through the bottom row of trays. Dampers are provided to 

 control the amount of recirculation of air and the degree of humidity 

 in the cabinet. 



Damper 



Baffle 



Figure 50. — Cabinet dehydrator designed to reheat the air in stages. 



The cabinet dehydrator illustrated in figure 50 is designed to re- 

 heat the circulating air in several stages, rather than all at once as in 

 the design shown in figure 49. Fresh air is drawn through the in- 

 take damper, picked up by the centrifugal fan, and forced through the 

 left-hand steam coil in the first stage of heating. Partitions are so 

 placed that the heated air passes through a few trays at the top of 

 the truck, then through the heater on the right-hand side, and back 

 through another section of trays as indicated by the arrows. The 

 moist air comes through the bottom row of trays and is carried through 

 a duct to the exhaust damper at the top of the cabinet. Recirculation 

 and humidity control are maintained with this damper. Two ad- 

 vantages are claimed for this design : (1) By repeated heatings fewer 

 pounds of air are necessary to remove a given weight of water, and (2) 

 more moderate dehydrating temperatures can be used. 



