Handbook for heating and ventilating engineers . By the aid of mechanical apparatus, air may be movedpositively in either of two ways, by the exhaust method orby the plenum method, each having fans developed best suitedto its needs. In the exhaust method the fan is commonlyof the disk av propeller blade type, shown in Figs. 86 and 156 HEATING AND VENTILATION S7, ana moves the air by suction. It is usually Installed Inthe attic or near the top of the building, although with asystem of return ducts it may be installed in the plenum system uses a fan of the paddle wheel or mul-tiple
Handbook for heating and ventilating engineers . By the aid of mechanical apparatus, air may be movedpositively in either of two ways, by the exhaust method orby the plenum method, each having fans developed best suitedto its needs. In the exhaust method the fan is commonlyof the disk av propeller blade type, shown in Figs. 86 and 156 HEATING AND VENTILATION S7, ana moves the air by suction. It is usually Installed Inthe attic or near the top of the building, although with asystem of return ducts it may be installed in the plenum system uses a fan of the paddle wheel or mul-tiple blade type, shown in Figs. 88 and 89; the first is thestandard form of fan wheel in common use, and the secondis a more recent development of the same, called the tur-bine fan wheel, shown direct connected to a De Lavalsteam turbine. The wheels of the fans are also Fig. 87. Tests of the latter wheel seem to show a somewhat higherefficiency than has heretofore been possible witli the olderforms. Both of these forms of fans are used in plenumwork, and are placed on the forcing side of the circulatingsystem just between the air intake and the heater coils,or just following the heater coils, and hence produce a pres-sure within the building or suite heated, so that leakagesare outward and not so detrimental to the good workingof the plant as in the exhaust system. The motive power for fans may be of four kinds,electric direct drive, steam engine or steam turbine directdrive, and belt and pulley drive, as shown in Figs. 87, 88, 89and 90. Which of these drives will be the most appropriatewin depend entirely upon local conditions and the nature PLENUM WARM AIR HEATING 157 of the available power supply. The steam engine or steamturbine drive is perhaps the most common, since somesteam must be present for the supply of the heating coils,and since, too, t
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectventila, bookyear1913
