. Seasoning of wood; a treatise on the natural and artificial processes employed in the preparation of lumber for manufacture . irculation can be controlled at all times. Briefly, it consists of a drying chamber with a partitionon either side, making two narrow side chambers opentop and bottom. The steam pipes are in the usual position underneaththe material to be dried. At the top of the side chambers is a spray; at the bottomare gutters and an eliminator or set of baffle plates toseparate the fine mist from the air. The spray accomplishes two things: It induces an in-creased circulation and
. Seasoning of wood; a treatise on the natural and artificial processes employed in the preparation of lumber for manufacture . irculation can be controlled at all times. Briefly, it consists of a drying chamber with a partitionon either side, making two narrow side chambers opentop and bottom. The steam pipes are in the usual position underneaththe material to be dried. At the top of the side chambers is a spray; at the bottomare gutters and an eliminator or set of baffle plates toseparate the fine mist from the air. The spray accomplishes two things: It induces an in-creased circulation and it regulates the humidity. This isdone by regulating the temperature of the spray water. The air under the heating coil is saturated at whatever KILN-DRYING OF WOOD 161 temperature is required. This temperature is the dewpoint of the air after it passes up into the drying chamberabove the coils. Knowing the temperature in the dryingroom and the dew point, the relative humidity is thusdetermined. The relative humidity is simply the ratio of the vaporpressure at the dew point to the pressure of saturatedvapor (see Fig. 30).. wftiRl^^^^^^^afeM Fig. 30. Section through United States Forestry Service Humidity-controlled Dry Kiln. Theory and Description of the Forestry Service Kiln The humidities and temperatures in the piles of lumberare largely dependent upon the circulation of air withinthe kiln. The temperature and humidity within the kiln,taken alone, are no criterion of the conditions of dryingwithin the pile of lumber if the circulation in any portion 162 SEASONING OF WOOD is deficient. It is possible to have an extremely rapid cir-culation of air within the dry kiln itself and yet havestagnation within the individual piles, the air passingchiefly through open spaces and channels. Whereverstagnation exists or the movement of air is too sluggishthe temperature will drop and the humidity increase,perhaps to the point of saturation. When in large kilns the forced circulation is i
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