November 2Tt, 1921 



HARDWOOD RECORD 



25 



the kilus within the limits desired and is simply influenced by the tem- 

 perature of the air. The wet bulb, however, is influenced by the amount 

 of evaporation that takes place on its surface which is kept moist by 

 water from a reservoir fed to said bulb by a wick. 



The drier the air is, the more rapid does the evaporation proceed, 

 and a greater amount of heat is, therefore, abstracted from the wet 

 bulb; consequently the temperature of the wet bulb is correspondingly 

 lower in comparison with the dry bulb. 



The less dry the air is the more slowly does tlie evaporation proceed 

 and a lesser amount of heat is, therefore, abstracted from the wet 

 bulb; consequently the temperature of the wet bulb is correspondingly 

 higher in comparison with the dry bulb. 



Maintaining certain wet bulb temperature controls humidity, there- 

 fore it is only necessary to so increase or decrease the moisture supply 

 that the wet bulb temperatures will correspond to the humidity desired 

 at certain air temperatures. For instance, if a particular temperature 

 and a particular humidity are wanted at a certain time within a kiln 

 during certain days as follows: 



Day Air Relative Wet Bulb 



Humidity Temp. 



Monday liOT. 65% 125y2°F. 



Wednesday 150°F. 53% 128°F. 



Friday 160°F. 46% 132°F. 



Sunday 170°F. 40% 136°F. 



then this controller maintains the required air temperature by regu- 

 lating the heating coils and maintains the desired humidity by regelat- 

 ing the source of humidity, whether steam sprays, water sprays, or 

 condensing coils, by a valve on the supply lines. 

 Changes Are Arrested 

 The tendency toward a change of temperature or humidity is over- 

 come. In other words, if a kUn shows a tendency to go higher or lower 

 than the dry bulb temperature for which the controller is set and is 

 shown for instance liy the ' ' air temperature ' ' column above by the 

 controller automatically either reducing or increasing the heat supply 

 similarly, if the humidity shows a tendency to go higher or lower than 

 the corresponding wet bulb temperature for which the controller is also 



set and in this instance as shown l>y the wet bulb column above, by the 

 controller automatically either reducing or increasing the source of 

 humidity. 



The setting point of the controller is automatically shifted also, to 

 take care of any desired air temperature or any desired humidity dur- 

 ing any desired time period by means of a cam revolved by clock work. 



The clock is so arranged to allow the cam to revolve once in any 

 period time from twelve hours to twenty-seven days. By this arrange- 

 ment, these temperature curves adaptable to a particular typo of kiln 

 can be supplied by cutting the cams to fit the temperature desired, 

 as for example: 



Minimum temperature 130°F. 



Maximum temperature 190 °F. 



Minimum Wet Bulb Temp. 130 °F. 



Maximum Wet Bulb Temp. 160 "F. 



With these curves made a part of the controller, the only thing left 

 to be desired is the length of time required to dry the material in the 

 kiln. For example — If by any certain drying schedule a certain num- 

 ber of days is require^d to dry 4/4 quarter sawed oak having twenty-five 

 percent moisture content, and according to this schedule the kOn 

 should run on the temperature curves shown above in fourteen days. 

 All that is necessary is to set the speed shift arrangement on fourteen 

 days and let the controller do the rest. 



Now, let's go back to the start of this narrative and suppose that 

 this firm with the steam heated concrete houses who piles its lumljcr 

 promiscuously in its dry kilns should utilize this money it wastes 

 each month and try out the better types of dry kilns, it then goes 

 further into the art of drying its material by an automatic con- 

 troller, as just described. This will pay high dividends to the man 

 who is broad enough to know that the human element and a dry 

 kiln are not as dependable as one automatically controlled every 

 second in each twenty-four hours. 



A controller of this kind will not in itself supply the temperature 

 nor humidity. It requires a heating plant for that. Neither will it 

 cause perfect circulation in the kiln, but if these fundamental prin- 

 ciples are not lacking, it will certainly give some wonderful regulation 

 and control of time, temperature and humidity. 



Suggestions Toward Improvement of Yard Drying Through Better Piling 



By Carl J. Maiiral 



(Co-ntinucd from yoicmbcr 10 Issue) 



Placing the pile so that its high face shall be exposed to the 

 south and its low face to the north, the sun warmed air will enter 

 at the high end of the ducts formed by the stickers between the 

 board courses, and progressing it will become denser and heavier 

 through cooling, in giving up some of its heat to the lumber, and 

 still heavier by taking up some of the lumber moisture, and fol- 

 lowing the law of gravity it will readily pass on through the down- 

 ward sloping ducts, and out at the north face of the pile, without 

 interference to the air circulatioii in force, volume or quality of 

 any adjoining duct on the side, above or below. 



Investigation developed that under average weather conditions a 

 space of one inch between the lumber courses will provide ample 

 duct capacity for the volume of air necessary to absorb, under 

 average temperature and humidity conditions of outdoor drying, 

 all of the moisture attracted to the surface of the lumber, if the 

 air traveled a distance of ton feet between adjoining courses of 

 lumber, impelled by its gravity alone, when the courses were 

 inclined 1% inches per foot, and if there were no interference by 

 adverse wind pressure. Ten feet, therefore, was the depth of the 

 pile adopted as standard, with one inch (full) as the logical thick- 

 ness of the stickers. 



Here it should be stated that the one inch thickness of stickers, 

 or the one inch height of air ducts will be quite sufficient for any 

 thickness of lumber or planks. To increase thickness of stickers 

 with increasing thickness of lumber is erroneous and unnecessary 



because the air contact is with the surface of the lumber only, 

 which surface remains the same per course, or top or bottom of the 

 air ducts, regardless of the thickness of the lumber. Many piles 

 of hardwood lumber, strictly green from the saw, 12/4 inch thick 

 and boards laid edge to edge, in the manner described, have been 

 carefully observed by the writer, and the edges were found in per- 

 fect condition after 18 months, free from stain, mold or slowness 

 of drying. When shrinkage begins, and it starts long before the 

 free moisture is out of the wood, an air space is formed between 

 the board edges, gradually enlarging itself, and this proves more 

 than sufficient for all requirements. 



A good foundation is essential. This may consist of nine con- 

 crete blocks with proper footings to suit soil conditions to each pile. 

 These foundation blocks should be spaced approximately as shown 

 in the sketch, and each entire foundation should be prepared for 

 16-foot lumber. Shorter lengths can then be readily taken care of. 

 Three 6"x8" pine timbers, placed east and west, over three of the 

 foundation blocks form the lengthwise sills, and these in turn sup- 

 port a number of movable cross sills, placed north and south over 

 same and kept from sliding by cleats attached to their south end 

 under side, to rest against the lengthwise sill. These cross sills 

 should be at least 4"x4" dimension, 10' 4" long and spaced to suit 

 the thickness of lumber to be piled. Better too many than not 

 enough. Lumber warped in drying remains so. It can be straight- 

 ened in some eases but the expense is prohibitive. Over these cross 

 (Continued on page 29) 



