. The railroad and engineering journal . 0 5,660 400 114-54 ■19-54 1,976,875 2,456,000 2,456,000 18,889 5,660 .rVoo X 100 = per cent. We may remark that this loss is greater as the quantityof air used is greater; and as the figure of 20 kgs. can beconsidered almost a minimum, it follows that this loss willbe almost always greater than the figure given above. The ratio between the direct and indirect heating sur-faces varies according to the type of boiler and accordingto the strength of draft. The more the latter is increasedthe more the indirect heating
. The railroad and engineering journal . 0 5,660 400 114-54 ■19-54 1,976,875 2,456,000 2,456,000 18,889 5,660 .rVoo X 100 = per cent. We may remark that this loss is greater as the quantityof air used is greater; and as the figure of 20 kgs. can beconsidered almost a minimum, it follows that this loss willbe almost always greater than the figure given above. The ratio between the direct and indirect heating sur-faces varies according to the type of boiler and accordingto the strength of draft. The more the latter is increasedthe more the indirect heating surface may be increased. The accompanying table, given by M. Ser, shovvs theproportions generally adopted in the three types of boilersmost commonly used. The results of this table are ap-plicable to fire-boxes burning coal, the radiating powervarying with different kinds of fuel. The importance ofthe direct heating surface decreases when the fuel has lessradiating power. The small table below permits us totake account of its effect:. In steam generators placed over heating furnaces inmetallurgic establishments, the direct radiation of the fur-nace does not exist and the avetage production of steamto the square meter of heating surface is considerablydiminished. In practice it is usual to give to such gen-erators a heating surface almost equal to that which theywould have if the whole quantity of fuel employed in thefurnace was burned in them directly. If we admit a duty of 65 per cent, for the boiler withordinary fire-box, this same boiler placed on a heatingfurnace would not give more than three-fifths of the resultobtained in the first case, so that the coefficient would notbe more than X J = —that is, about 40 per cent, of the theoretical efficiency. PRODUCTION OF STEAM PER SQUARE METER PER HOUR. In boilers fired externally the average production ofsteam per square meter of heating surface per hour shouldbe from 10 to 15 kg. If below 10 kg. there is too great
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Keywords: ., bookcentury1800, bookdecade1880, booksubjectrailroa, bookyear1887
