Forged steel water-tube marine boilers manufactured by the Babcock & Wilcox co.

This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1905 Excerpt: ...G--Support for agitator and thermometer. K--Spring and screw for revolving agitator. L--Lever of agitator. M--Pressure gauge. O--Oxygen cylinder. P--Electric battery. S--Agitator. T--Thermometer. STEAM--PROPERTIES AND LAWS OF GENERATION HEN water is converted into steam it has first to be heated to a certain definite temperature which is called the boiling point. This temperature equals 212 degrees Fahrenheit for the ordinary pressure of the atmosphere (14.7 pounds above vacuum); but as the pressure is increased the boiling point increases, although at a decreasing ratio, until at 500 pounds above vacuum it equals 466.57 degrees Fahrenheit. As the water rises in temperature, it absorbs heat at the rate of one B. T. U. for each degree Fahrenheit. This is known as the heat of the liquid, or sensible heat, as it may be shown by means of a thermometer. After reaching the boiling point, the further addition of heat transforms the water into steam without increasing its temperature. The heat thus absorbed is called the heat of vaporization, or "latent heat," and cannot be shown by any instrument for measuring temperatures. The latent heat decreases as the pressure increases, it being about 966 British thermal units per pound at atmospheric pressure, and about 780 at 500 pounds pressure above vacuum. It will be seen, therefore, that the temperature of steam normal to its pressure, is the same as the water at the boiling point, and also that the total heat in steam consists of two parts; first, the heat contained in the liquid at the boiling point, and second, the heat of vaporization. Or, in other words, the total heat is the sum of the sensible heat and the latent heat. The total heat increases slightly as the pressure increases, being 1146.6 British th...