. Power, heating and ventilation ... a treatise for designing and constructing engineers, architects and students. t. 8 ft. 10 ft. 12 ft. 16 ft. 20 ft. 25 ft. 30 ft. 35 ft. 40 ft. ^H»w O 2 100 570 690 790 860 930 1060 1190 1310 1480 1535 1635 8 8 242 600 600 680 746 810 920 1020 1130 1220 1320 1400 9 4 430 440 610 680 646 695 790 876 970 1060 1130 1195 10 5 734 370 430 525 670 615 690 765 840 910 970 1080 11 , 6 1068 330 430 480 530 570 650 710 780 845 906 960 12 7 1439 320 370 420 460 490 650 605 670 720 775 820 14 8 1880 280 320 860 395 425 480 626 680 630
. Power, heating and ventilation ... a treatise for designing and constructing engineers, architects and students. t. 8 ft. 10 ft. 12 ft. 16 ft. 20 ft. 25 ft. 30 ft. 35 ft. 40 ft. ^H»w O 2 100 570 690 790 860 930 1060 1190 1310 1480 1535 1635 8 8 242 600 600 680 746 810 920 1020 1130 1220 1320 1400 9 4 430 440 610 680 646 695 790 876 970 1060 1130 1195 10 5 734 370 430 525 670 615 690 765 840 910 970 1080 11 , 6 1068 330 430 480 530 570 650 710 780 845 906 960 12 7 1439 320 370 420 460 490 650 605 670 720 775 820 14 8 1880 280 320 860 395 425 480 626 680 630 675 715 16 162 HEATING AND VENTILATING PLANTS from the pipe. These conditions are met by having a conicalend to the suction pipe and a spiral casing surrounding the form of the casing should be such that the water flowingaround it will move with the same velocity as that issuing fromthe blades of the wheel, then enlarging into the discharge pipethrough a conical mouthpiece. Fig. 113 shows the form of wheel or impeller commonly usedin pumps of small size, and Fig. 114 the hollow-arm type, em-. Fig. 115. Lawrence Centrifugal Pump. ployed in those of larger size. The latter has the advantage thatthe water is thrown outward without any churning motion, andalso that there are no dead spaces within the casing. Efficiency and Horse Power.—Under ordinary conditions theeiificiency of a centrifugal pump falls off considerably for headsabove 30 or 35 feet, but multiple-stage pumps are constructedwhich work with a good efficiency against 1,000 feet or more. Under favorable conditions an efficiency of 60 to 70 per cent isoften obtained, but for hot-water circulation it is more commonto assume an efficiency of about 50 per cent for the average case. HOT-WATER HEATING BY FORCED CIRCULATION 163 The horse power required for driving a pump is given by theformula: H. ,000X£ in which ff=friction head in feet. F=gallons of water delivered per minute. £=efl5ciency
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectventilation, bookyear
