Document RaORM6QEYORX7Rp6yLgwB5or8

1126 CHAPTER 45. = 1958.Guide Table 4. Induced-Air-Flow Equivalent of the Eneboy in Falling, Unenclosed Streams of Particles (For a solid* flow rale R of t lb per sec and a specific gravity z = 1 referred to water.) Air Flow Equivalent, Cfm, (to be multiplied bt (ft/*)1/*) Falling Stream Distance, a Area, sq ft 1 t Particle Size, Millimeters: s to ` to SO too 3 ft 14 450 350 220 180 150 80 65 1 750 550 350 300 250 150 100 2 1200 850- 550 450 350 200 170 4 1900 1400 850 700 600 350 250 8 3000 2200 1400 1100 900 500 400 15 4600 3300 2000 1700 1400 800 650 25 6400 4600 3000 2500 2000 1000 900 50 10000 7500 4700 4000 3200 , 1800 1400 6 ft H 1 2 4 350 300 250 200 150 600 500 350 300 200 900 700 600 400 350 1500 1200 900 700 500- 8 2300 1800 1500 1000 900 15 3500 2800 2200 1500 1300 25 5000 4000 3200 2300 1800 50 8000 6000 5000 3700 3000 12 ft )4 1 2 4 560 900 1500 2300 450 700 1100 1800 350 600 900 1500 270 420 700 1000 220 350 550 850 20 ft 30 ft 8 15 25 50 X 1 2 4 8 15 25 M 1 2 4 8 15 25 3600 5300 7800 -- 800 1300 2000 3300 5000 8000 -- 1000 1700 2700 4400 6800 10000 -- 2900 4200 6000 10000 650 1000 1600 2600 4100 6400 9000 850 1400 2100 3500 5400 8200 -- 2300 3500 5000 8000 500 800 1300 2000 3200 5000 7000 650 1100 1700 2700 4200 6600 9000 1700 2600 3600 6000 370 600 960 1500 2400 3700 5000 500 800 1300 2000 3200 4800 6800 1300 2100 2900 4700 300 500 760 1200 1900 2900 4000 400 600 1000 1600 2500 4000 5400 From Plant and Process Ventilation by W. C. L. Hemeon, The Industrie! Press, New York (1955). tion must be employed, the air flow toward the hood has to overcome the tendency of the heated air to rise and also must sweep it into the hood. Consequently, the required exhaust air flow is very much larger than for hoods that simply capture the upward flow of heated air. A combination of an exhaust hood with a positive jet of air blown across the top of the M Industrial Exhaust Systems 1127 Table 5. Exhaust Requirements' fob Grinding, . Polishing, Buffing, Scratch Brushing Abrasive Cut-Off Wheels, Grinding and ... , Polishing Belts (Air Volume: 4600 fpm in'all branches.) (2 in. water suction at average hood) Grinding ob Cut-Oft Wheels - Buffing, 'Polishing, and Scratch Bbushing Wheel Diam, In. Max. Width*, In. Branch Diam, In. - CFM . ; Wheel. Diam, Max. Branch - in. Width*, In. Diam, In. CFM - 9 i{ 3 225 10-16 17-19 2 3 4 . 390 . 500 -9 10-16 2 3} 3 41 300 . 20-24 4 5 ' 610 17-19 .4 5 25-30 31-36 5 6 6 880 .20-24 7 1200 25-30 5 -6 ! 51 61 * ; ;i04o Horizontal Single Spindle Disc Grinders : Horizontal Double Spindle Disc. .Grinders - Vertical Single Spindle. Disc Grinders Wheel Diam, In. BranchDiam, In.' CFM Wheel Branch Diam, In. Diam, In. CFM Wheel Diam; In. Branch Diam, In.. : CFM. -12 13-19 20-30 31-36 3 4' 6 6 225 . 390 610 880 -19 20-25 26^30 31-53 54-72 1-5 1-6 1-7 2-6 . 4-8 610 880: 1200 1760 6240 -20 21^30 31-53 54-72 1-41 2-4 2-6 2-8 500 . 780 1760 . . 3120.'. Grinding ob Polishing Belts: otJ 3ninwide--3 " hmnch, add 1 in. to branch diameter for each 2 in. or fraction increase in belt width ^e Increase branch diameter 0.3 in., but not less than } in., for each 1 in. increase in width over dimension equipment and directed into the hood may be required above large pieces of equipment. Hemeon has suggested18 design Equations 2 to 6 which follow for:: var ious types of hoods. 1: Equation 2 is suggested for estimating the flow of heated air rising from the top of a hot body: . where ?o = 29 y/lp> It, ' i- ' , g) ?0 = air flow rate at upper limits of hot body, cubic feet per minute. f" = crss-sectional area of air stream at upper limits of hot body; square feet. Is -- height of hot body, feet. He = convectional heat transfer rate, Btu per minute FnT>f ar6a Ap may be aPProximated from the dimensions of the hot body, the r rtnZLtal rods' tbe width of the stream is practically the diameter of of 4 t k f1r vertlcal Planes, the air stream appears to thicken at an angle streorv, de? witb the Plane. For horizontal planes, the area of the air am may be taken as equal to the area of the plane itself. informal- Cas? horizontal plates, in the absence of better experimental 5 fundh-' e may be taken as equal to the horizontal diameter. Chapter rate ffBs mformation which may be used in estimating the heat transfer ,The flow rate, g , of heated air entering the hood after turbulent mixing