Canadian wood products industries . of least resistance it is diffi-cult to see how an adequate even circulation of warmair through the lumber piles can be secured and main-tained when depending solely upon the uncontrollednatural movement of the air. If the warm air followsthe lines of least resistance in its upward movementmost of the air will tend to rise on either side ofthe piles of lumber, with a slight flow into the edgeof the piles. These two currents come together atthe top and then attempt to gradually drop downthrough the lumber, only to be met by the warm airthat is attempting to w
Canadian wood products industries . of least resistance it is diffi-cult to see how an adequate even circulation of warmair through the lumber piles can be secured and main-tained when depending solely upon the uncontrollednatural movement of the air. If the warm air followsthe lines of least resistance in its upward movementmost of the air will tend to rise on either side ofthe piles of lumber, with a slight flow into the edgeof the piles. These two currents come together atthe top and then attempt to gradually drop downthrough the lumber, only to be met by the warm airthat is attempting to work its way up from the bot-tom of the pile. The result is that as the ascendingand descending currents meet and stabilize in thecentre of the pile a dead air pocket is formed, whichgradually decreases as the drying progresses, butwhich also prolongs the drying period for it is usuallyseveral days behind the rest of the pile. From the foregoing it will be seen that some Assistant engineer, Forest Products Engineering Co., Since it is the air that removes the moisture from the surface of lum-her in a dry kiln, the movement of the air must he ample in all part^of the kiln, or uneven drying will result. The drift of smoke produced bysome hunting substance is often used as an indicator for searching outzones of too rapid or sluggish circulation in kilns. This method is greatly facilitated hy the use of the apparatus shownhere which was developed at the Forest Products LaboratoryMadison, Wisconsin. In this device, the Uf of which involves no firehazard, as in burning rope, punk, etc., in the kiln, the fumes of hydro-chloric acid are blown across ammonia; and an abundance of harmless,visible fumes are produced. These funics, being of approximately at-mospheric temperature, have little tendency to rise or fall indei>endenl otair currents. (Photograph furnished by the Forest Service ! a proper arrangement of inlet and outlet ducts it ispossible to secure a fairly
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Keywords: ., bookcentury1900, bookdecade1920, booksubjectfurnitu, bookyear1922
