Being Here

Commercially, temperature readings are extremely important. In sugar refineries the temperature of the heated liquids is observed most carefully, since a difference in temperature, however slight, affects not only the general appearance of sugars and sirups, but the quality as well. The many varieties of steel likewise show the influence which heat may have on the nature of a substance. By observation and tedious experimentation it has been found that if hardened steel is heated to about 450 deg. F. and quickly cooled, it gives the fine cutting edge of razors; if it is heated to about 500 deg. F. and then cooled, the metal is much coarser and is suitable for shears and farm implements; while if it is heated but 50 deg. F. higher, that is, to 550 deg. F., it gives the fine elastic steel of watch springs.

When fuel is placed in an open fireplace (Fig. 12) and lighted, the air immediately surrounding the fire becomes warmer and, because of expansion, becomes lighter than the cold air above. The cold air, being heavier, falls and forces the warmer air upward, and along with the warm air goes the disagreeable smoke. The fall of the colder and heavier air, and the rise of the warmer and hence lighter air, is similar to the exchange which takes place when water is poured on oil; the water, being heavier than oil, sinks to the bottom and forces the oil to the surface. The warmer air which escapes up the chimney carries with it the disagreeable smoke, and when all the smoke is got rid of in this way, the chimney is said to draw well.

The metal pipes which convey the heated air from the furnace to the ducts are sometimes covered with felt, asbestos, or other non-conducting material in order that heat may not be lost during transmission. The ducts which receive the heated air from the pipes are built in the non-conducting walls of the house, and hence lose practically no heat. The air which reaches halls and rooms is therefore warm, in spite of its long journey from the cellar.

The principle of hot-water heating is shown by the following simple experiment. Two flasks and two tubes are arranged as in Figure 15, the upper flask containing a colored liquid and the lower flask clear water. If heat is applied to _B_, one can see at the end of a few seconds the downward circulation of the colored liquid and the upward circulation of the clear water. If we represent a boiler by _B_, a radiator by the coiled tube, and a safety tank by _C_, we shall have a very fair illustration of the principle of a hot-water heating system. The hot water in the radiators cools and, in cooling, gives up its heat to the rooms and thus warms them.

• First of 1
• Second of 1
• Third of 1
• Fourth of 1
• Fifth of 1
• Sixth of 1

Copyright © 2006-2007 Bredimus.s5.com. All rights reserved.

Some information may no longer be up-to-date. Not responsible for content provided on other sites. Links are provided for reference only and do not necessarily constitute endorsements or specific recommendations. Bredimus.s5.com is not liable for content provided by other Web sites.