This article first appeared in Practical Engineering 1940 Vol1 No3. The information herein is accurate as of 1940. The piece brings to the attention of the reader developments within Engineering at the time.
For industrial as well as power station application the gilled tube economiser has the well-known inherent and important advantages of greatly increased heating surface per unit space occupied. Gills of some designs and types, however, have disadvantages as compared with a smooth tube, especially in connection with the deposition of soot and dust which increases the difficulty of effective cleaning. In addition, this operation cannot be carried out continuously with the convenient slow-moving, mechanically-operated scrapers, and intermittently operated steam-jet cleaning has to be used.
Some time ago, E. Green and Son, Ltd., of Wakefield, placed on the market their new "Premier Diamond" gilled tube economiser, which possesses not only the maximum heat absorption, using a special square type of gill, but which also has solved the problem of soot and dust deposition. This new economiser is available in two types— with cast-iron tubes having integral cast-iron gills, for up to 650 lbs. per bq. in. pressure, and steel tubes with cast-iron gills shrunk on, which also prevent external corrosion, for almost any pressure, up to 4,500 lbs. per sq. in. if necessary.
In both cases, however, the principle is the same, the tubes being arranged horizontally in staggered rows, one above the other, whilst the large rectangular gills form with the tube portion a diamond shape in vertical cross section, that is, with a sharp edge at the top and bottom. Consequently, soot and dust cannot deposit to any appreciable extent because of the sharp edges and the smooth, sloping, fiat surfaces of the diamond portions. These constitute a difficult resting place for solid particles, which slide down and fall to the bottom of the casing. A travelling steam jet soot-blower is provided, which however in most cases need not be used more than a few minutes per shift, and with some coals is not necessary.
The economiser tubes are fixed horizontally in a steel-plate casing formed of removable panels, the travel of the combustion gases outside the tubes being vertical and the water inside horizontal, both at high velocity, which itself increases the rate of heat transmission and reduces the tendency to soot and dust deposition.