HUMIDITY-REGULATED AND EECIRCULATING DRY KILN. 



11 



spray. This spra;f completely saturates the air in the flue B at what- 

 ever predetermined temperature is required. The baffle plates D D 

 are to separate all entrained particles of water from the air, so that 

 it is delivered to the heaters in a saturated condition at the required 

 temperature. This temperature is, therefore, the dew point of the 

 air when heated above, and the method of humidity control may 

 therefore be called the dew-point method. It is a very simple matter 

 by means of the humidity diagram,^ or by a hydrodeik, to determine 

 what dew-point temperature is needed for any desired humidity 

 above the heaters. 



Fig. 1. — Diagrammatic section of improved dry kiln with spray chambers 



Double-truck form. 



in center. 



Besides regulating the humidity the spray F also acts as an ejector 

 and forces a circulation of air through the flue B. The heating sys- 

 tem H is concentrated near the outer walls, so as to heat the rising 

 column of air. The temperature within the drying chamber is con- 

 trolled by means of any suitable thermostat, actuating a valve on the 

 main steam line. The lumber is piled in such a way that the 

 stickers slope downward toward the center. 



M is an auxiliary steam spray pointing downward for use at very 

 high temperatures. C is a gutter to catch the precipitation and 



1 Forest Service Bulletin 104, " Principles of Drying Lumber at Atmospheric Pressure 

 and Humidity Diagram," Superintendent of Documents, Government Printing Office, 

 Washington, D. C. Price, 5 cents. Lumber World Review, Feb. 10, 1915, 



