The quantity of warm air for drying and its temperatures are the main factors. The practical ranges in temperature suitable for drying different products are given in Table I. The air supply required depends upon the rate at which the moisture is given up by the material. The air change frequency varies with every condition, the range being from 2 to 5 changes per minute in the drying chamber.

A rule-of-thumb for determining the volume of air required for a drying process allows 21⁄2 changes of air per minute in the drying chamber. The temperature of this warm air supply to be considered as the highest value given in Table I, corresponding to the material that is to be dried.

A closer approximation of drying requirements may be arrived at with the aid of Table II. The figures give the quantity of air necessary at saturation to evaporate one pound of water at the corresponding temperatures of the air entering the drying chamber. These values are based on the theory that the air will leave the dryer completely saturated. In practice it is found that the air does not remove more than 50 to 70% of the moisture, and allowance should be made for same.

cu. ft. While wet, the rope weighs 350 lbs., and after being dried, the weight is 250 lbs., requiring that 100 lbs. of water be removed. With the air entering the heater saturated, 827 cu. ft. of air will be required per pound of water as in Table II, for 160° temperature. Then 100 lb. X 827 cu. ft. equals 82,700 cu. ft., which is the volume of air necessary for drying the rope. If it were required to complete the drying process in 120 minutes, then the warm air supply would have to be delivered at the rate of 689 cu. ft. per min. This gives a theoretical air frequency of 689 divided by 600 or 1.15 changes per minute.

In making allowance for a practical installation, it should be remembered that the air in absorbing the moisture from the rope will be only a little more than half saturated. On a 50% basis, therefore, the volume of air will have to be doubled if the time remain 120 min. or the time extended to 4 hours if the air volume remain as above.

NEW DEVICES

New Smokeless Type of Capitol Boiler.

A widespread curiosity on the part of the heating trade has been gratified in the publication of data regarding the new smokeless type of Capitol boiler, which has recently been placed on the market by the United States Radiator Corporation, Detroit, Mich. Unlike most smokeless boilers, this construction discards the downdraft principle. It is largely built according to the general recommendations for the construction of smokeless furnaces as made by D. T. Randall, of the Bureau of Mines.

1. The coal should be supplied to the furnace in small quantities at frequent intervals. The more nearly the feed approaches a continuous and uniform supply the better the results.

2. The air supply should be slightly in excess of the theoretical amount required and be admitted principally through the fuel bed, with an auxiliary supply admitted at the front or rear of the furnace to burn gases from the coal.

3. The temperature in the furnace should be sufficiently high to ignite the gases given off from the fuel bed.

4. There should be a fire-brick combustion chamber of sufficient dimensions and

CONSTRUCTION OF CAPITOL SMOKELESS BOILER.

the furnace into the mixing chamber through two horizontal openings at the top and in the back or bridge wall of the furnace. The mixing chamber back of the furnace is formed by the bridge wall at the front and an ignition wall of fire brick at the rear of the mixing chamber.

The passage of the gases from the mixing chamber to the combustion chamber at the rear of the boiler is through a long, vertical opening in the ignition wall, permitting a congestion and intermixture of burning gases, and their complete combustion in the combustion chamber. It is stated that the principle of complete combustion before the gases are cooled, as opposed to the downdraft principle, in which the cooling of the volatile gases begins at the upper or water grate, results in exceedingly high efficiencies.

Another advantage mentioned for this type of boiler is that no skilled attendance is necessary to obtain smokeless results. As the design provides for the complete combustion of the volatile matter in the boiler, there is no smoke to escape to the open air except during, the time when the fire doors are open and coal is being fed to the boiler. It is stated that any of the bituminous coals may be used, including the lignites from the far West, at the same

Load in % of Load at 25° C

20 30 40

50

Temp. of the Ingoing Air in C

14 32 50 68 86 104 122

Temp.of the Ingoing Air in F

PERMISSIBLE LOAD ON A TURBO-ALTERNATOR AS A FUNCTION OF THE TEMPERATURE OF THE INGOING AIR.

generators are designed for a certain allowable maximum temperature in the armature and field windings makes some means for cooling them a matter of importance. With a given load, the temperature of a generator will be a fixed amount above the temperature of the ingoing ventilating air; therefore, the cooler the air delivered to the generator, the greater will be its capacity. The cleanliness of the air is also an important feature. The gain in capacity with cool air is worked out in the form of a chart giving the K.V.A. load

on turbo-alternators as a function of the entering air, and since the standard air temperature for electrical machinery is 25° C. (77° F.), 100% load is taken at this temperature. As an example, the temperature is assumed to be 90° F. (32.2° C.) with a relative humidity of 45%. The curve shows that with air at this temperature the safe capacity of the generator is only 87% of full load rating. If the air is passed through a Type B Spraco air washer and cooler, it may be reduced to a temperature of 74° F. (23.3° C.) or less, enabling the generator to carry 1022% load, resulting in a gain of approximately 15%, as the power required to operate the washer is but a fraction of 1% of the generator rating. The catalogue shows the different types of Spraco air washers, including typical installations. At the end is a list of 98 installations. Pp. Size 8 x 1034 in. Pp. 16.

PROGRESS IN HOT WATER HEATING is the titie of a revised and enlarged edition of a handbook devoted to the D. and T. tank-inbasement equipment, manufactured and sold by the D. & T. Mfg. Co., St. Louis, Mo. This system, primarily, is one for regulating the drafts on hot water heating boilers by means of the natural law of water expansion under increasing temperatures. The handbook goes on to describe the various devices used in this system including the D. and T. regulator, D. and T. air-sealed pressure controller and the D. and T. pressure gauge. Size 334in. x 6 in. Pp. 124.

VALVE WORLD for December, 1916, the monthly periodical of Crane Co., Chicago, readable contains, among other things, a article on "Des Moines, the City of Uncertainties." This issue closes the eleventh year in the life of the l'alve World.

Organization of Braemer Air Conditioning Corporation.

Warren Webster & Co., Camden, N. J., announce that they have disposed of the business of their air conditioning department and on and after January 1, 1917, the Webster air conditioning apparatus will be manufactured and exploited by the Braemer Air Conditioning Corporation, Lafayette Building, Philadelphia, Pa. The new corporation has been formed by William R. Braemer, for many years manager of the air conditioning department of Warren Webster & Co. Besides conducting a general business in the manufacture and sale of air purifying apparatus, the new company will act as experts in air conditioning work in all its phases.

The best wishes of a wide circle of friends will accompany Mr. Braemer in his enlarged field of activity.