CONSULTING DEPARTMENT-(Continued)

pieces have been so accurately united, by intense heat or otherwise, that the junctures cannot even be discovered by a powerful magnifying glass.

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Refrigeration

Question. Describe process of absorption refrigeration.-R. S. P.

Answer. In the absorption system, it is necessary to maintain pressure upon the ammonia gas when freed from water in order that it may become liquefied, and during its period of liquefaction give up the latent heat.

The Carré original machine consisted. of two strong iron jars connected together with an iron pipe. In jar I, or ammonia still, was placed a quantity of highly charged aqua ammonia. A spirit lamp was placed under jar I. When the jar became heated, an air cock was opened until the air was exhausted. Jar 2 was placed in a tank and surrounded by cold water. The supply of this water was constantly changing so that at all times the water remained cold or at its original temperature, which we may assume at 60 degrees Fahr. The heat from the lamp caused the ammonia to vaporize and a pressure was obtained sufficient to liquefy the gas in jar 2. This pressure was about 120 pounds per square inch. The intense pressure made by the ammonia gas was sufficient to raise the boiling pressure of the water to 230 degrees Fahr., thereby preventing the vaporization of the water. This temperature was ample to drive out a large amount of gas.

After the process was complete, which was determined by the length of time. that the heat was exposed to jar I, the lamp was removed. The water was drawn off from around jar 2 and the tank filled with whatever substance it was desired to freeze. A water pipe allowed water to flow over jar I and cool its contents, the result being that the pressure was removed from both jars, and the liquid anhydrous gas began to vaporize in jar 2, the gas again returned to jar I, and was taken up

Sketching Device

Yo

YOU need this instrument right on your own desk. Every man does who has an idea to express. In one half the time spent in going to the drafting room and explaining what you want to the draftsman you can, with the aid of the Rapid Sketching Device, jot down your idea yourself with perfect clearness and accuracy. The Rapid Sketching Device is a money saver, because it is a time saver. It enables you to draw and scale your lines at the same time and at any desired angle. It consists of a graduated square, which, by means of a protractor, can be set at any angle, thus giving parallel lines anywhere about the board. This parallel motion is accomplished by means of an arm consisting of two pivoted parallelograms which join the protractor to the left hand corner of the board. Spring stops are provided for the zero, 30°, 45°, 60° and 90° angles, so that these may be obtained without stopping to read the protractor. The blades of the square are scales and are interchangeable; furnished in any length and any graduation. Also straight edge for inking. The Rapid Sketching Device can be used for drawings up to 18'x24', and is ordinarily used on a 20"x 27" board.

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Complete Information on Application Universal Drafting Machine Co. 220-226 SENECA STREET Cleveland, Ohio, U. S. A.

CONSULTING DEPARTMENT-(Continued)

in the water from which it had been expelled. By the passage of the anhydrous ammonia from a liquid to a gas, the heat which was taken up and caused the vaporization, being held latent by the gas, was taken from the surrounding liquid in the tank.

This produced a low temperature, the boiling point of liquid anhydrous ammonia being at atmospheric pressure 47 degrees below zero Fahr. The ratio of the temperature and pressure determines the temperature at which the gas boils in passing from a liquid to a gaseous condition.

Cooling Towers

Question. When is it advantageous to use a cooling tower?-F. W. M.

Answer. It sometimes happens that it is impossible to place a steam plant in close proximity to a natural water supply. In such cases the water necessary for the condenser (the circulating water) is expensive, and if the cost is very great it does not pay to add the condenser, because the cost of the circulating water might more than offset the gain from

could be provided whereby the circulating water as it issues from the condenser could be cooled and then used over again in the condenser, the noncondensing engine could then be run condensing; thus taking advantage of all the benefits due to the use of reduced back pressure and heating of the feed water. This has been attempted by conducting the heated discharge water to a pond, where it is allowed to cool to a lower temperature before being used again. Another plan is to place in the yard or on the roof of the building large shallow pans, in which the water is cooled by being exposed to the atmosphere. These methods are unsatisfactory on account of the considerable area necessary and the slow action. In addition, they are uncertain, because they are dependent upon atmospheric conditions.

A more efficient and at the same time more expensive process is to use a cooling tower or a water table. The discharge from the condenser is led to the top of

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CONSULTING DEPARTMENT-(Concluded)

the cooling tower, where it is cooled before being returned to the condenser. This cooling is effected by distributing the water, by a system of piping to the upper edge of a series of mats or slats, over the surface of which the water flows in a thin film to a reservoir which is situated in the bottom of the cooling tower. The mats partially interrupt the flow, and by breaking up the water in small streams cause new portions to be exposed to the cooling effect of the air currents. The water from the reservoir then flows downward through the suction pipe, and is pumped by the circulating pump through the condenser. After passing through the condenser and absorbing heat from the exhaust steam, it rises through the discharge pipe and commences the circuit over again.

The tower may have several arrangements and be made of various materials. A satisfactory form is constructed of steel plates; within the tower are a large number of mats of steel wire cloth galvanized after weaving.

To assist in the cooling of the water, the air is often made to circulate rapidly by means of a fan, which forces the air into the lower part of the tower and upwards among the mats. This fan is usually of the ordinary type, and may be driven by an electric motor, a line of shafting, or by a small independent engine.

In case the fan is not used, the mats are arranged so that they are exposed to the atmosphere. This, of course, necessitates the removal of the steel casing. Usually the fanless tower must be placed at the top of a high building, or in some position where the currents of air can readily circulate among the mats.

With an efficient type of cooling tower the water may be reduced from 30° to 50° Fahr., thus allowing a vacuum of from 22 inches to 26 inches. This will, of course, greatly increase the economy of the plant, and allow the heated feed water to be returned to the boilder.

The water table is usually made of wooden slats placed in the ground near the plant. After trickling over the slats and becoming cooled by the air, it collects in the bottom of the reservoir and is then pumped into the condenser.