Method of loading LumberFig. 51. Method of loading Lumber on its Flat, cross-wise of the Dry Kiln when same has Three Tracks.
Fig. 51. Method of loading Lumber on its Flat, cross-wise of the Dry Kiln when same has Three Tracks.
Method of loading LumberFig. 52. Method of loading Lumber on its Flat, end-wise of the Dry Kiln by the Use of the Single-sill or Dolly Truck.
Fig. 52. Method of loading Lumber on its Flat, end-wise of the Dry Kiln by the Use of the Single-sill or Dolly Truck.
Method of loading LumberFig. 53. Method of loading Lumber on its Flat, end-wise of the Dry Kiln by the Use of the Double-sill Truck.
Fig. 53. Method of loading Lumber on its Flat, end-wise of the Dry Kiln by the Use of the Double-sill Truck.
Method of loading Kiln CarFig. 54. Method of loading Kiln Car with Tight or Slack Barrel Staves cross-wise of Dry Kiln.
Fig. 54. Method of loading Kiln Car with Tight or Slack Barrel Staves cross-wise of Dry Kiln.
Method of loading Kiln CarFig. 55. Method of loading Kiln Car with Tight or Slack Barrel Staves cross-wise of Dry Kiln.
Fig. 55. Method of loading Kiln Car with Tight or Slack Barrel Staves cross-wise of Dry Kiln.
Method of loading Kiln CarFig. 56. Method of loading Kiln Car with Tub or Pail Staves cross-wise of Dry Kiln.
Fig. 56. Method of loading Kiln Car with Tub or Pail Staves cross-wise of Dry Kiln.
Method of loading Kiln CarFig. 57. Method of loading Kiln Car with Bundled Staves cross-wise of Dry Kiln.
Fig. 57. Method of loading Kiln Car with Bundled Staves cross-wise of Dry Kiln.
InFigure 58will be seen method of piling shingles "cross-wise" of dry kiln when same has three tracks.
InFigure 59will be seen another method of piling shingles "cross-wise" of the dry kiln when same has three tracks.
Method of loading Kiln CarFig. 58. Method of loading Kiln Car with Shingles cross-wise of Dry Kiln.
Fig. 58. Method of loading Kiln Car with Shingles cross-wise of Dry Kiln.
Method of loading Kiln CarFig. 59. Method of loading Kiln Car with Shingles cross-wise of Dry Kiln.
Fig. 59. Method of loading Kiln Car with Shingles cross-wise of Dry Kiln.
InFigure 60will be seen method of piling shingles "end-wise" of the dry kiln when same has two tracks.
InFigure 61will be seen a kiln car designed for handling short tub or pail staves through a dry kiln.
Car loaded with 100,000 ShinglesFig. 60. Car loaded with 100,000 Shingles. Equipped with four long end-wise piling trucks and to go into dry kiln end-wise.
Fig. 60. Car loaded with 100,000 Shingles. Equipped with four long end-wise piling trucks and to go into dry kiln end-wise.
Kiln Car designed for handling Short Tub or Pail StavesFig. 61. Kiln Car designed for handling Short Tub or Pail Staves through a Dry Kiln.
Fig. 61. Kiln Car designed for handling Short Tub or Pail Staves through a Dry Kiln.
InFigure 62will be seen a kiln car designed for short piece stock through a dry kiln.
InFigure 63will be seen a type of truck designed for the handling of stave bolts about a stave mill or through a steam box.
InFigure 64will be seen another type of truck designed for the handling of stave bolts about a stave mill or through a steam box.
InFigure 65will be seen another type of truck designed for the handling of stave bolts about a stave mill or through a steam box.
InFigure 66will be seen another type of truck designed for the handling of stave bolts about a stave mill or through a steam box.
InFigure 67will be seen another type of truck designed for the handling of stave bolts about a stave mill or through a steam box.
InFigure 68will be seen another type of truck designed for the handling of stave bolts about a stave mill or through a steam box.
InFigure 69will be seen the Regular 3-rail Transfer Car designed for the handling of 2-rail kiln cars which have been loaded "end-wise."
InFigure 70will be seen another type of Regular 3-rail Transfer Car designed for the handling of 2-rail kiln cars which have been loaded "end-wise."
InFigure 71will be seen a Specially-designed 4-rail Transfer Car for 2-rail kiln cars which have been built to accommodate extra long material to be dried.
InFigure 72will be seen the Regular 2-rail Transfer Car designed for the handling of 3-rail kiln cars which have been loaded "cross-wise."
InFigure 73will be seen another type of Regular 2-rail Transfer Car designed for the handling of 3-rail kiln cars which have been loaded "cross-wise."
InFigure 74will be seen the Regular 2-rail Underslung type of Transfer Car designed for the handling of 3-rail kiln cars which have been loaded "cross-wise." Two important features in the construction of this transfer car make it extremely easy in its operation. It has extra large wheels, diameter 131⁄2inches, and being underslung, the top of its rails are no higher than the other types of transfer cars. Note the relative size of the wheels in the illustration, yet the car is only about 10 inches in height.
Kiln Car Designed for handling Short Piece StockFig. 62. Kiln Car Designed for handling Short Piece Stock through a Dry Kiln.
Fig. 62. Kiln Car Designed for handling Short Piece Stock through a Dry Kiln.
A Stave Bolt TruckFig. 63. A Stave Bolt Truck.
Fig. 63. A Stave Bolt Truck.
A Stave Bolt TruckFig. 64. A Stave Bolt Truck.
Fig. 64. A Stave Bolt Truck.
A Stave Bolt TruckFig. 65. A Stave Bolt Truck.
Fig. 65. A Stave Bolt Truck.
A Stave Bolt TruckFig. 66. A Stave Bolt Truck.
Fig. 66. A Stave Bolt Truck.
A Stave Bolt TruckFig. 67. A Stave Bolt Truck.
Fig. 67. A Stave Bolt Truck.
A Stave Bolt TruckFig. 68. A Stave Bolt Truck.
Fig. 68. A Stave Bolt Truck.
A Regular 3-Rail Transfer TruckFig. 69. A Regular 3-Rail Transfer Truck.
Fig. 69. A Regular 3-Rail Transfer Truck.
A Regular 3-Rail Transfer TruckFig. 70. A Regular 3-Rail Transfer Truck.
Fig. 70. A Regular 3-Rail Transfer Truck.
A Special 4-Rail Transfer TruckFig. 71. A Special 4-Rail Transfer Truck.
Fig. 71. A Special 4-Rail Transfer Truck.
A Regular 2-Rail Transfer TruckFig. 72. A Regular 2-Rail Transfer Truck.
Fig. 72. A Regular 2-Rail Transfer Truck.
A Regular 2-Rail Transfer TruckFig. 73. A Regular 2-Rail Transfer Truck.
Fig. 73. A Regular 2-Rail Transfer Truck.
A Regular 2-Rail Underslung Transfer TruckFig. 74. A Regular 2-Rail Underslung Transfer Truck.
Fig. 74. A Regular 2-Rail Underslung Transfer Truck.
InFigure 75will be seen the Regular 3-rail Underslung type of Transfer Car designed for the handling of 2-rail kiln cars which have been loaded "end-wise." This car also has the important features of large diameter wheels and low rail construction, which make it very easy in its operation.
A Regular 3-Rail Underslung Transfer TruckFig. 75. A Regular 3-Rail Underslung Transfer Truck.
Fig. 75. A Regular 3-Rail Underslung Transfer Truck.
InFigure 76will be seen the Special 2-rail Flexible type of Transfer Car designed for the handling of 3-rail kiln cars which have been loaded "cross-wise." This car is equipped with double the usual number of wheels, and by making each set of trucks a separate unit (the front and rear trucks being bolted to a steel beam with malleable iron connection), a slight up-and-down movement is permitted, which enables this transfer car to adjust itself to any unevenness in the track, which is a very good feature.
A Special 2-Rail Flexible Transfer TruckFig. 76. A Special 2-Rail Flexible Transfer Truck.
Fig. 76. A Special 2-Rail Flexible Transfer Truck.
InFigure 77will be seen the Regular Transfer Car designed for the handling of stave bolt trucks.
InFigure 78will be seen another type of Regular Transfer Car designed for the handling of stave bolt trucks.
InFigure 79will be seen a Special Transfer Car designed for the handling of stave bolt trucks.
A Regular Transfer Car for handling Stave Bolt TrucksFig. 77. A Regular Transfer Car for handling Stave Bolt Trucks.
Fig. 77. A Regular Transfer Car for handling Stave Bolt Trucks.
A Regular Transfer Car for handling Stave Bolt TrucksFig. 78. A Regular Transfer Car for handling Stave Bolt Trucks.
Fig. 78. A Regular Transfer Car for handling Stave Bolt Trucks.
A Special Transfer Car for handling Stave Bolt TrucksFig. 79. A Special Transfer Car for handling Stave Bolt Trucks.
Fig. 79. A Special Transfer Car for handling Stave Bolt Trucks.
InFigure 80will be seen the Regular Channel-iron Kiln Truck designed for edge piling "cross-wise" of the dry kiln.
InFigure 81will be seen another type of Regular Channel-iron Kiln Truck designed for edge piling "cross-wise" of the dry kiln.
A Regular Channel-iron Kiln TruckFig. 80. A Regular Channel-iron Kiln Truck.
Fig. 80. A Regular Channel-iron Kiln Truck.
A Regular Channel-iron Kiln TruckFig. 81. A Regular Channel-iron Kiln Truck.
Fig. 81. A Regular Channel-iron Kiln Truck.
InFigure 82will be seen the Regular Channel-iron Kiln Truck designed for flat piling "end-wise" of the dry kiln.
A Regular Channel-iron Kiln TruckFig. 82. A Regular Channel-iron Kiln Truck.
Fig. 82. A Regular Channel-iron Kiln Truck.
InFigure 83will be seen the Regular Channel-iron Kiln Truck with I-Beam cross-pieces designed for flat piling "end-wise" of the dry kiln.
InFigure 84will be seen the Regular Small Dolly Kiln Truck designed for flat piling "end-wise" of the dry kiln.
A Regular Channel-iron Kiln TruckFig. 83. A Regular Channel-iron Kiln Truck.
Fig. 83. A Regular Channel-iron Kiln Truck.
A Regular Single-sill or Dolly Kiln TruckFig. 84. A Regular Single-sill or Dolly Kiln Truck.
Fig. 84. A Regular Single-sill or Dolly Kiln Truck.
InFigure 85will be seen the Asbestos-lined Door. The construction of this kiln door is such that it has no tendency to warp or twist. The framework is solid and the body is made of thin slats placed so that the slat on either side covers the open space of the other with asbestos roofing fabric in between. This makes a comparatively light and inexpensive door, and one that absolutely holds the heat. These doors may be built either swinging, hoisting, or sliding.
An Asbestos-lined Kiln Door of the Hinge TypeFig. 85. An Asbestos-lined Kiln Door of the Hinge Type.
Fig. 85. An Asbestos-lined Kiln Door of the Hinge Type.
InFigure 86will be seen the Twin Carrier type of door hangers with doors loaded and rolling clear of the opening.
Twin Carrier with Kiln Door loaded and rolling clear of OpeningFig. 86. Twin Carrier with Kiln Door loaded and rolling clear of Opening.
Fig. 86. Twin Carrier with Kiln Door loaded and rolling clear of Opening.
InFigure 87will be seen the Twin Carrier for doors 18 to 35 feet wide, idle on a section of the track.
InFigure 88will be seen another type of carrier for kiln doors.
InFigure 89will be seen the preceding type of kiln door carrier in operation.
InFigure 90will be seen another type of carrier for kiln doors.
InFigure 91will be seen kiln doors seated, wood construction, showing 31⁄2" × 53⁄4" inch-track timbers and trusses, supported on 4-inch by 6-inch jamb posts. "T" rail track, top and side, inclined shelves on which the kiln door rests. Track timber not trussed on openings under 12 feet wide.
Twin Carriers for Kiln Doors 18 to 35 Feet wideFig. 87. Twin Carriers for Kiln Doors 18 to 35 Feet wide.
Fig. 87. Twin Carriers for Kiln Doors 18 to 35 Feet wide.
Kiln Door Carrier engaged to Door Ready for liftingFig. 88. Kiln Door Carrier engaged to Door Ready for lifting.
Fig. 88. Kiln Door Carrier engaged to Door Ready for lifting.
InFigure 92will be seen kiln doors seated, fire-proof construction, showing 12-inch, channel, steel lintels, 2" × 2" steel angle mullions, track brackets bolted to the steel lintels and "T" rail track. No track timbers or trusses used.
Kiln Door Carrier shown on Doors of Wood ConstructionFig. 89. Kiln Door Carrier shown on Doors of Wood Construction.
Fig. 89. Kiln Door Carrier shown on Doors of Wood Construction.
Kiln Door Construction with Door Carrier out of SightFig. 90. Kiln Door Construction with Door Carrier out of Sight.
Fig. 90. Kiln Door Construction with Door Carrier out of Sight.
Kiln Door Construction. Doors Seated. Wood Construction.Fig. 91. Kiln Door Construction. Doors Seated. Wood Construction.
Fig. 91. Kiln Door Construction. Doors Seated. Wood Construction.
Kiln Door Construction. Doors Seated. Fire-proof Construction.Fig. 92. Kiln Door Construction. Doors Seated. Fire-proof Construction.
Fig. 92. Kiln Door Construction. Doors Seated. Fire-proof Construction.
Humidity Diagram
Fig. 93. The United States Forest Service Humidity Diagram for determination of Absolute Humidities. Dew Points and Vapor Pressures; also Relative Humidities by means of Wet and Dry-Bulb Thermometer, for any temperatures and change in temperature.
Somesimple means of determining humidities and changes in humidity brought about by changes in temperature in the dry kiln without the use of tables is almost a necessity. To meet this requirement the United States Forestry Service has devised the Humidity Diagram shown inFigure 93. It differs in several respects from the hydrodeiks now in use.
The purpose of the humidity diagram is to enable the dry-kiln operator to determine quickly the humidity conditions and vapor pressure, as well as the changes which take place with changes of temperature. The diagram above is adapted to the direct solution of problems of this character without recourse to tables or mathematical calculations.
The humidity diagram consists of two distinct sets of curves on the same sheet. One set, the convex curves, is for the determination of relative humidity of wet-and-dry-bulb hygrometer or psychrometer; the other, the concave curves, is derived from the vapor pressures and shows the amount of moisture per cubic foot at relative humidities and temperatures when read at the dew-point. The latter curves, therefore, are independent of all variables affecting the wet-bulb readings. They are proportional to vapor pressures, not to density, and, therefore, may be followed from one temperature to another with correctness. The short dashes show the correction (increase or decrease) which is necessary in the relative humidity, read from the convex curves, with an increase or decrease from the normal barometric pressure of 30 inches, for which the curveshave been plotted. This correction, except for very low temperatures, is so small that it may usually be disregarded.
The ordinates, or vertical distances, are relative humidity expressed in per cent of saturation, from 0 per cent at the bottom to 100 per cent at the top. The abscissae, or horizontal distances, are temperatures in degrees Fahrenheit from 30 degrees below zero, at the left, to 220 degrees above, at the right.
The application of the humidity diagram can best be understood by sample problems. These problems also show the wide range of conditions to which the diagram will apply.
Example 1.To find the relative humidity by use of wet-and-dry-bulb hygrometer or psychrometer:Place the instrument in a strong circulation of air, or wave it to and fro. Read the temperature of the dry bulb and the wet, and subtract. Find on the horizontal line the temperature shown by the dry-bulb thermometer. Follow the vertical line from this point till it intersects with the convex curve marked with the difference between the wet and dry readings. The horizontal line passing through this intersection will give the relative humidity.Example: Dry bulb 70°, wet bulb 62°, difference 8°. Find 70° on the horizontal line of temperature. Follow up the vertical line from 70° until it intersects with the convex curve marked 8°. The horizontal line passing through this intersection shows the relative humidity to be 64 per cent.Example 2.To find how much water per cubic foot is contained in the air:Find the relative humidity as in example 1. Then the nearest concave curve gives the weight of water in grains per cubic foot when the air is cooled to the dew-point. Using the same quantities as in example 1, this will be slightly more than 5 grains.Example 3.To find the amount of water required to saturate air at a given temperature:Find on the top line (100 per cent humidity) the given temperature; the concave curve intersecting at or nearthis point gives the number of grains per cubic foot. (Interpolate, if great accuracy is desired.)Example 4.To find the dew-point:Obtain the relative humidity as in example 1. Then follow up parallel to the nearest concave curve until the top horizontal (indicating 100 per cent relative humidity) is reached. The temperature on this horizontal line at the point reached will be the dew-point.Example: Dry bulb 70°, wet bulb 62°. On the vertical line for 70° find the intersection with the hygrometer (convex) curve for 8°. This will be found at nearly 64 per cent relative humidity. Then follow up parallel with the vapor pressure (concave) curve marked 5 grains to its intersection at the top of the chart with the 100 per cent humidity line. This gives the dew-point as 57°.Example 5.To find the change in the relative humidity produced by a change in temperature:Example: The air at 70° Fahr. is found to contain 64 per cent humidity; what will be its relative humidity if heated to 150° Fahr.? Starting from the intersection of the designated humidity and temperature coordinates, follow the vapor-pressure curve (concave) until it intersects the 150° temperature ordinate. The horizontal line then reads 6 per cent relative humidity. The same operation applies to reductions in temperature. In the above example what is the humidity at 60°? Following parallel to the same curve in the opposite direction until it intersects the 60° ordinate gives 90 per cent; at 57° it becomes 100 per cent, reaching the dew-point.Example 6.To find the amount of condensation produced by lowering the temperature:Example: At 150° the wet bulb reads 132°. How much water would be condensed if the temperature were lowered to 70°? The intersection of the hygrometer curve for 18° (150°-132°) with temperature line for 150° shows a relative humidity of 60 per cent. The vapor-pressure curve (concave) followed up to the 100 per cent relative humidity line shows 45 grains per cubic foot at the dew-point, which corresponds to a temperature of 130°. At 70° it is seen that the air can contain but 8 grains per cubic foot (saturation). Consequently, there will be condensed 45 minus 8, or 37 grains per cubic foot of space measured at the dew-point.Example7. To find the amount of water required to produce saturation by a given rise in temperature:Example: Take the values given in example 5. The air at the dew-point contains slightly over 5 grains per cubic foot. At 150° it is capable of containing 73 grains per cubic foot. Consequently, 73-5=68 grains of water which can be evaporated per cubic foot of space at the dew-point when the temperature is raised to 150°. But the latent heat necessary to produce evaporation must be supplied in addition to the heat required to raise the air to 150°.Example8. To find the amount of water evaporated during a given change of temperature and humidity:Example: At 70° suppose the humidity is found to be 64 per cent and at 150° it is found to be 60 per cent. How much water has been evaporated per cubic foot of space? At 70° temperature and 64 per cent humidity there are 5 grains of water present per cubic foot at the dew-point (example 2). At 150° and 60 per cent humidity there are 45 grains present. Therefore, 45-5=40 grains of water which have been evaporated per cubic foot of space, figuring all volumes at the dew-point.Example9. To correct readings of the hygrometer for changes in barometric pressure:A change of pressure affects the reading of the wet bulb. The chart applies at a barometric pressure of 30 inches, and, except for great accuracy, no correction is generally necessary.Find the relative humidity as usual. Then look for the nearest barometer line (indicated by dashes). At the end of each barometer line will be found a fraction which represents the proportion of the relative humidity already found, which must be added or subtracted for a change in barometric pressure. If the barometer reading is less than 30 inches, add; if greater than 30 inches, subtract. The figures given are for a change of 1 inch; for other changes use proportional amounts. Thus, for a change of 2 inches use twice the indicated ratio; for half an inch use half, and so on.Example: Dry bulb 67°, wet bulb 51°, barometer 28 inches. The relative humidity is found, by the method given in example 1, to equal 30 per cent. The barometricline—gives a value of 3/100H for each inch of change. Since the barometer is 2 inches below 30, multiply 3/100H by 2, giving 6/100H. The correction will, therefore, be 6/100 of 30, which equals 1.8. Since the barometer is below 30, this is to be added, giving a corrected relative humidity of 31.8 per cent.This has nothing to do with the vapor pressure (concave) curves, which are independent of barometric pressure, and consequently does not affect the solution of the previous problems.Example10. At what temperature must the condenser be maintained to produce a given humidity?Example: Suppose the temperature in the drying room is to be kept at 150° Fahr., and a humidity of 80 per cent is desired. If the humidity is in excess of 80 per cent the air must be cooled to the dew-point corresponding to this condition (see example 4), which in this case is 141.5°.Hence, if the condenser cools the air to this dew point the required condition is obtained when the air is again heated to the initial temperature.Example11. Determination of relative humidity by the dew-point:The quantity of moisture present and relative humidity for any given temperature may be determined directly and accurately by finding the dew-point and applying the concave (vapor-pressure) curves. This does away with the necessity for the empirical convex curves and wet-and-dry-bulb readings. To find the dew-point some form of apparatus, consisting essentially of a thin glass vessel containing a thermometer and a volatile liquid, such as ether, may be used. The vessel is gradually cooled through the evaporation of the liquid, accelerated by forcing air through a tube until a haze or dimness, due to condensation from the surrounding air, first appears upon the brighter outer surface of the glass. The temperature at which the haze first appears is the dew-point. Several trials should be made for this temperature determination, using the average temperature at which the haze appears and disappears.To determine the relative humidity of the surrounding air by means of the dew-point thus determined, find the concave curve intersecting the top horizontal (100 percent relative humidity) line nearest the dew-point temperature. Follow parallel with this curve till it intersects the vertical line representing the temperature of the surrounding air. The horizontal line passing through this intersection will give the relative humidity.Example: Temperature of surrounding air is 80; dew-point is 61; relative humidity is 53 per cent.The dew-point determination is, however, not as convenient to make as the wet-and-dry-bulb hygrometer readings. Therefore, the hygrometer (convex) curves are ordinarily more useful in determining relative humidities.
Example 1.To find the relative humidity by use of wet-and-dry-bulb hygrometer or psychrometer:
Place the instrument in a strong circulation of air, or wave it to and fro. Read the temperature of the dry bulb and the wet, and subtract. Find on the horizontal line the temperature shown by the dry-bulb thermometer. Follow the vertical line from this point till it intersects with the convex curve marked with the difference between the wet and dry readings. The horizontal line passing through this intersection will give the relative humidity.Example: Dry bulb 70°, wet bulb 62°, difference 8°. Find 70° on the horizontal line of temperature. Follow up the vertical line from 70° until it intersects with the convex curve marked 8°. The horizontal line passing through this intersection shows the relative humidity to be 64 per cent.
Place the instrument in a strong circulation of air, or wave it to and fro. Read the temperature of the dry bulb and the wet, and subtract. Find on the horizontal line the temperature shown by the dry-bulb thermometer. Follow the vertical line from this point till it intersects with the convex curve marked with the difference between the wet and dry readings. The horizontal line passing through this intersection will give the relative humidity.
Example: Dry bulb 70°, wet bulb 62°, difference 8°. Find 70° on the horizontal line of temperature. Follow up the vertical line from 70° until it intersects with the convex curve marked 8°. The horizontal line passing through this intersection shows the relative humidity to be 64 per cent.
Example 2.To find how much water per cubic foot is contained in the air:
Find the relative humidity as in example 1. Then the nearest concave curve gives the weight of water in grains per cubic foot when the air is cooled to the dew-point. Using the same quantities as in example 1, this will be slightly more than 5 grains.
Find the relative humidity as in example 1. Then the nearest concave curve gives the weight of water in grains per cubic foot when the air is cooled to the dew-point. Using the same quantities as in example 1, this will be slightly more than 5 grains.
Example 3.To find the amount of water required to saturate air at a given temperature:
Find on the top line (100 per cent humidity) the given temperature; the concave curve intersecting at or nearthis point gives the number of grains per cubic foot. (Interpolate, if great accuracy is desired.)
Find on the top line (100 per cent humidity) the given temperature; the concave curve intersecting at or nearthis point gives the number of grains per cubic foot. (Interpolate, if great accuracy is desired.)
Example 4.To find the dew-point:
Obtain the relative humidity as in example 1. Then follow up parallel to the nearest concave curve until the top horizontal (indicating 100 per cent relative humidity) is reached. The temperature on this horizontal line at the point reached will be the dew-point.Example: Dry bulb 70°, wet bulb 62°. On the vertical line for 70° find the intersection with the hygrometer (convex) curve for 8°. This will be found at nearly 64 per cent relative humidity. Then follow up parallel with the vapor pressure (concave) curve marked 5 grains to its intersection at the top of the chart with the 100 per cent humidity line. This gives the dew-point as 57°.
Obtain the relative humidity as in example 1. Then follow up parallel to the nearest concave curve until the top horizontal (indicating 100 per cent relative humidity) is reached. The temperature on this horizontal line at the point reached will be the dew-point.
Example: Dry bulb 70°, wet bulb 62°. On the vertical line for 70° find the intersection with the hygrometer (convex) curve for 8°. This will be found at nearly 64 per cent relative humidity. Then follow up parallel with the vapor pressure (concave) curve marked 5 grains to its intersection at the top of the chart with the 100 per cent humidity line. This gives the dew-point as 57°.
Example 5.To find the change in the relative humidity produced by a change in temperature:
Example: The air at 70° Fahr. is found to contain 64 per cent humidity; what will be its relative humidity if heated to 150° Fahr.? Starting from the intersection of the designated humidity and temperature coordinates, follow the vapor-pressure curve (concave) until it intersects the 150° temperature ordinate. The horizontal line then reads 6 per cent relative humidity. The same operation applies to reductions in temperature. In the above example what is the humidity at 60°? Following parallel to the same curve in the opposite direction until it intersects the 60° ordinate gives 90 per cent; at 57° it becomes 100 per cent, reaching the dew-point.
Example: The air at 70° Fahr. is found to contain 64 per cent humidity; what will be its relative humidity if heated to 150° Fahr.? Starting from the intersection of the designated humidity and temperature coordinates, follow the vapor-pressure curve (concave) until it intersects the 150° temperature ordinate. The horizontal line then reads 6 per cent relative humidity. The same operation applies to reductions in temperature. In the above example what is the humidity at 60°? Following parallel to the same curve in the opposite direction until it intersects the 60° ordinate gives 90 per cent; at 57° it becomes 100 per cent, reaching the dew-point.
Example 6.To find the amount of condensation produced by lowering the temperature:
Example: At 150° the wet bulb reads 132°. How much water would be condensed if the temperature were lowered to 70°? The intersection of the hygrometer curve for 18° (150°-132°) with temperature line for 150° shows a relative humidity of 60 per cent. The vapor-pressure curve (concave) followed up to the 100 per cent relative humidity line shows 45 grains per cubic foot at the dew-point, which corresponds to a temperature of 130°. At 70° it is seen that the air can contain but 8 grains per cubic foot (saturation). Consequently, there will be condensed 45 minus 8, or 37 grains per cubic foot of space measured at the dew-point.
Example: At 150° the wet bulb reads 132°. How much water would be condensed if the temperature were lowered to 70°? The intersection of the hygrometer curve for 18° (150°-132°) with temperature line for 150° shows a relative humidity of 60 per cent. The vapor-pressure curve (concave) followed up to the 100 per cent relative humidity line shows 45 grains per cubic foot at the dew-point, which corresponds to a temperature of 130°. At 70° it is seen that the air can contain but 8 grains per cubic foot (saturation). Consequently, there will be condensed 45 minus 8, or 37 grains per cubic foot of space measured at the dew-point.
Example7. To find the amount of water required to produce saturation by a given rise in temperature:
Example: Take the values given in example 5. The air at the dew-point contains slightly over 5 grains per cubic foot. At 150° it is capable of containing 73 grains per cubic foot. Consequently, 73-5=68 grains of water which can be evaporated per cubic foot of space at the dew-point when the temperature is raised to 150°. But the latent heat necessary to produce evaporation must be supplied in addition to the heat required to raise the air to 150°.
Example: Take the values given in example 5. The air at the dew-point contains slightly over 5 grains per cubic foot. At 150° it is capable of containing 73 grains per cubic foot. Consequently, 73-5=68 grains of water which can be evaporated per cubic foot of space at the dew-point when the temperature is raised to 150°. But the latent heat necessary to produce evaporation must be supplied in addition to the heat required to raise the air to 150°.
Example8. To find the amount of water evaporated during a given change of temperature and humidity:
Example: At 70° suppose the humidity is found to be 64 per cent and at 150° it is found to be 60 per cent. How much water has been evaporated per cubic foot of space? At 70° temperature and 64 per cent humidity there are 5 grains of water present per cubic foot at the dew-point (example 2). At 150° and 60 per cent humidity there are 45 grains present. Therefore, 45-5=40 grains of water which have been evaporated per cubic foot of space, figuring all volumes at the dew-point.
Example: At 70° suppose the humidity is found to be 64 per cent and at 150° it is found to be 60 per cent. How much water has been evaporated per cubic foot of space? At 70° temperature and 64 per cent humidity there are 5 grains of water present per cubic foot at the dew-point (example 2). At 150° and 60 per cent humidity there are 45 grains present. Therefore, 45-5=40 grains of water which have been evaporated per cubic foot of space, figuring all volumes at the dew-point.
Example9. To correct readings of the hygrometer for changes in barometric pressure:
A change of pressure affects the reading of the wet bulb. The chart applies at a barometric pressure of 30 inches, and, except for great accuracy, no correction is generally necessary.Find the relative humidity as usual. Then look for the nearest barometer line (indicated by dashes). At the end of each barometer line will be found a fraction which represents the proportion of the relative humidity already found, which must be added or subtracted for a change in barometric pressure. If the barometer reading is less than 30 inches, add; if greater than 30 inches, subtract. The figures given are for a change of 1 inch; for other changes use proportional amounts. Thus, for a change of 2 inches use twice the indicated ratio; for half an inch use half, and so on.Example: Dry bulb 67°, wet bulb 51°, barometer 28 inches. The relative humidity is found, by the method given in example 1, to equal 30 per cent. The barometricline—gives a value of 3/100H for each inch of change. Since the barometer is 2 inches below 30, multiply 3/100H by 2, giving 6/100H. The correction will, therefore, be 6/100 of 30, which equals 1.8. Since the barometer is below 30, this is to be added, giving a corrected relative humidity of 31.8 per cent.This has nothing to do with the vapor pressure (concave) curves, which are independent of barometric pressure, and consequently does not affect the solution of the previous problems.
A change of pressure affects the reading of the wet bulb. The chart applies at a barometric pressure of 30 inches, and, except for great accuracy, no correction is generally necessary.
Find the relative humidity as usual. Then look for the nearest barometer line (indicated by dashes). At the end of each barometer line will be found a fraction which represents the proportion of the relative humidity already found, which must be added or subtracted for a change in barometric pressure. If the barometer reading is less than 30 inches, add; if greater than 30 inches, subtract. The figures given are for a change of 1 inch; for other changes use proportional amounts. Thus, for a change of 2 inches use twice the indicated ratio; for half an inch use half, and so on.
Example: Dry bulb 67°, wet bulb 51°, barometer 28 inches. The relative humidity is found, by the method given in example 1, to equal 30 per cent. The barometricline—gives a value of 3/100H for each inch of change. Since the barometer is 2 inches below 30, multiply 3/100H by 2, giving 6/100H. The correction will, therefore, be 6/100 of 30, which equals 1.8. Since the barometer is below 30, this is to be added, giving a corrected relative humidity of 31.8 per cent.
This has nothing to do with the vapor pressure (concave) curves, which are independent of barometric pressure, and consequently does not affect the solution of the previous problems.
Example10. At what temperature must the condenser be maintained to produce a given humidity?
Example: Suppose the temperature in the drying room is to be kept at 150° Fahr., and a humidity of 80 per cent is desired. If the humidity is in excess of 80 per cent the air must be cooled to the dew-point corresponding to this condition (see example 4), which in this case is 141.5°.Hence, if the condenser cools the air to this dew point the required condition is obtained when the air is again heated to the initial temperature.
Example: Suppose the temperature in the drying room is to be kept at 150° Fahr., and a humidity of 80 per cent is desired. If the humidity is in excess of 80 per cent the air must be cooled to the dew-point corresponding to this condition (see example 4), which in this case is 141.5°.
Hence, if the condenser cools the air to this dew point the required condition is obtained when the air is again heated to the initial temperature.
Example11. Determination of relative humidity by the dew-point:
The quantity of moisture present and relative humidity for any given temperature may be determined directly and accurately by finding the dew-point and applying the concave (vapor-pressure) curves. This does away with the necessity for the empirical convex curves and wet-and-dry-bulb readings. To find the dew-point some form of apparatus, consisting essentially of a thin glass vessel containing a thermometer and a volatile liquid, such as ether, may be used. The vessel is gradually cooled through the evaporation of the liquid, accelerated by forcing air through a tube until a haze or dimness, due to condensation from the surrounding air, first appears upon the brighter outer surface of the glass. The temperature at which the haze first appears is the dew-point. Several trials should be made for this temperature determination, using the average temperature at which the haze appears and disappears.To determine the relative humidity of the surrounding air by means of the dew-point thus determined, find the concave curve intersecting the top horizontal (100 percent relative humidity) line nearest the dew-point temperature. Follow parallel with this curve till it intersects the vertical line representing the temperature of the surrounding air. The horizontal line passing through this intersection will give the relative humidity.Example: Temperature of surrounding air is 80; dew-point is 61; relative humidity is 53 per cent.The dew-point determination is, however, not as convenient to make as the wet-and-dry-bulb hygrometer readings. Therefore, the hygrometer (convex) curves are ordinarily more useful in determining relative humidities.
The quantity of moisture present and relative humidity for any given temperature may be determined directly and accurately by finding the dew-point and applying the concave (vapor-pressure) curves. This does away with the necessity for the empirical convex curves and wet-and-dry-bulb readings. To find the dew-point some form of apparatus, consisting essentially of a thin glass vessel containing a thermometer and a volatile liquid, such as ether, may be used. The vessel is gradually cooled through the evaporation of the liquid, accelerated by forcing air through a tube until a haze or dimness, due to condensation from the surrounding air, first appears upon the brighter outer surface of the glass. The temperature at which the haze first appears is the dew-point. Several trials should be made for this temperature determination, using the average temperature at which the haze appears and disappears.
To determine the relative humidity of the surrounding air by means of the dew-point thus determined, find the concave curve intersecting the top horizontal (100 percent relative humidity) line nearest the dew-point temperature. Follow parallel with this curve till it intersects the vertical line representing the temperature of the surrounding air. The horizontal line passing through this intersection will give the relative humidity.
Example: Temperature of surrounding air is 80; dew-point is 61; relative humidity is 53 per cent.
The dew-point determination is, however, not as convenient to make as the wet-and-dry-bulb hygrometer readings. Therefore, the hygrometer (convex) curves are ordinarily more useful in determining relative humidities.
InFigure 94will be seen the Hygrodeik. This instrument is used to determine the amount of moisture in the atmosphere. It is a very useful instrument, as the readings may be taken direct with accuracy.
To find the relative humidity in the atmosphere, swing the index hand to the left of the chart, and adjust the sliding pointer to that degree of the wet-bulb thermometer scale at which the mercury stands. Then swing the index hand to the right until the sliding pointer intersects the curved line, which extends downwards to the left from the degree of the dry-bulb thermometer scale, indicated by the top of the mercury column in the dry-bulb tube.
At that intersection, the index hand will point to the relative humidity on scale at bottom of chart (for example seeFig. 94). Should the temperature indicated by the wet-bulb thermometer be 60 degrees, and that of the dry-bulb 70 degrees, the index hand will indicate humidity 55 degrees, when the pointer rests on the intersecting line of 60 degrees and 80 degrees.
InFigure 95is shown the Recording Hygrometer complete with wet and dry bulbs, two connecting tubes and two recording pens and special moistening device for supplying water to the wet bulb.
This equipment is designed particularly for use in connection with dry rooms and dry kilns and is arranged sothat the recording instrument and the water supply bottle may be installed outside of the dry kiln or drying room, while the wet and dry bulbs are both installed inside the room or kiln at the point where it is desired to measure the humidity. This instrument records on a weekly chart the humidity for each hour of the day, during the entire week.
The HygrodeikFig. 94. The Hygrodeik.
Fig. 94. The Hygrodeik.
InFigure 96is shown the Registering Hygrometer, which consists of two especially constructed thermometers. The special feature of the thermometers permits placing the instrument in the dry kiln without entering the drying room, through a small opening, where it is left for about 20 minutes.
The Recording HygrometerFig. 95. The Recording Hygrometer, Complete with Wet and Dry Bulbs. This instrument records on a weekly chart the humidity for each hour of the day, during the entire week.
Fig. 95. The Recording Hygrometer, Complete with Wet and Dry Bulbs. This instrument records on a weekly chart the humidity for each hour of the day, during the entire week.
The temperature of both the dry and wet bulbs are automatically recorded, and the outside temperature will not affect the thermometers when removed from the kiln. From these recorded temperatures, as shown when the instrument is removed from the kiln, the humidity can be easily determined from a simple form of chart which is furnished free by the makers with each instrument.
The Registering HygrometerFig. 96. The Registering Hygrometer.
Fig. 96. The Registering Hygrometer.
The Recording ThermometerFig. 97. The Recording Thermometer.
Fig. 97. The Recording Thermometer.
InFigure 97is shown the Recording Thermometer for observing and recording the temperatures within a dry kiln, and thus obtaining a check upon its operation. Thisinstrument is constructed to record automatically, upon a circular chart, the temperatures prevailing within the drying room at all times of the day and night, and serves not only as a means of keeping an accurate record of the operation of the dry kiln, but as a valuable check upon the attendant in charge of the drying process.
The Registering Thermometer
Fig. 98. The Registering Thermometer.
The Recording Steam-Pressure GaugeFig. 99. The Recording Steam-Pressure Gauge.]
Fig. 99. The Recording Steam-Pressure Gauge.]
InFigure 98is shown the Registering Thermometer, which is a less expensive instrument than that shown inFigure 97, but by its use the maximum and minimum temperatures in the drying room during a given period can be determined.
InFigure 99is shown the Recording Steam Pressure Gauge, which is used for accurately recording the steam pressures kept in the boilers. This instrument may bemounted near the boilers, or may be located at any distance necessary, giving a true and accurate record of the fluctuations of the steam pressure that may take place within the boilers, and is a check upon both the day and night boiler firemen.
InFigure 100is shown the Troemroid Scalometer. This instrument is a special scale of extreme accuracy, fitted with agate bearings with screw adjustment for balancing. The beam is graduated from 0 to 2 ounces, divided into 100 parts, each division representing 1-50th of an ounce; and by using the pointer attached to the beam weight, the 1-100th part of an ounce can be weighed.