Boilers and Furnaces Considered in Their Relations to Steam Engineering (Paperback)

This historic book may have numerous typos and missing text. Purchasers can usually download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1898 edition. Excerpt: ... in mixing the hot gas at the centre with the cold film next the surface of the tube. Also in every horizontal tube there is a tendency for the gases to be cooler in the upper part of the tube and hotter in the lower, for the upper part of the tube extracts heat far more readily from the gases than the lower half. The twist of the retarder has the effect of repeatedly turning over the gas in the tube as it flows along. In the second place, the retarder acts by direct radiation of heat to the tube surface. While this action may not be apparent at first sight, it is of such importance that it should be clearly understood. To this end the fact should first be realized that the temperature of the tube surface exposed to the fire in any steam boiler is practically the same as that of water in contact with it, no matter what the temperature of the gas on the other side, supposing, of course, the tube surface to be clean. The reason is that water absorbs heat many times as rapidly as gas. Now suppose we place in the tube any solid body, of any shape whatever. Manifestly, as it is surrounded and bathed on all sides by gases at a temperature of say io00 Fahr., it will, if it loses no heat, soon become of the same temperature as the hot gases. Suppose the surface of the tube is of a temperature of 3000 Fahr., the hot body at the centre of the tube will energetically radiate heat to the walls of the tube and will materially increase the amount of heat transmitted to the water. Whitham's Experiments.--A trial of retarders on a 100 horse-power horizontal tubular boiler was conducted by J. M. Whitham, to ascertain under what conditions, if any, they would add to the efficiency of the boiler. The boiler was 60 inches diameter by 20 feet long, fitted...