Document em5k6m6b2e6JQbwEj3qG36Ggy

.' W |WPf-,,h &*> f .1 * ft sfS'i I' -$$& .' rift# . Vi Kp^r 5-^' GRINDING 300 mWHEEL Ventilation GRINDING WHEEL 337 NO CAP ON STACK .-Mjrt'NjINfi Tsa^Bcr.TH, HD tajo :'m;i - J %1&2&X] r $-4 300 cfm GRINDING WHEEL GRINDING BOOTH DUST PAN COLLECTOR 5000 cfm 3000 cfm o' 5 tolol at 2" a .7 fit otic *,0,ic pressure pressure drop For simplicity, all horizontal and vertical bends ore represented In the same plans. Figure 24. Line diagram of an exhaust system. lATION BETWEEN AIR VELOCITY AND VELOCITY PRESSURE iJirJJhjiltinue or kinetic energy of moving air may be expressed in terms of WiWOmLH"-- or potential energy of a vertical column of water. Thus, the ru si.srafrs ;^u^,e exertecj by a column of water 1 inch high is enough to .balance i n ^ -ted by an air stream that impinges against a stationary surface ^^mc:t''frtf approximately 4000 l.f.m. We say, therefore, that 4000 l.f.m. head" or "velocity pressure" of 1 inch of water. Conversely, if swpib'u1j)ivsgure of 1 inch of water is allowed to escape to the atmosphere fi'iipess orifice, itwill emerge with a verbcity'of 4000 l.f.m. FSj^i0^t'.'a|piications in the field, the following approximate formula can be f!'jh,Lr`Jof|the two forms given: Air velocity, or V = 4000 y/VP f&p i Velocity pressure, or VP = (V/4000)2 xW D. AIR-DUCT FRICTION atuehart (Figure 22) applies to the flow of dry air at 70 F. and ometer through round straight galvanized sheet-metal ducts of 'uib^th.ahoutAO. Blip joints per hundred feet. i'V"' ln'pipes or ducts that differ considerably from the conveniij;:)c!.nrf?aficonstruction can be computed from the following formula in 17 and 18 : ^^^^^n%j!fe-f=water _ / 1200 \ /l.f.m.V ^J^^Sin.dred feet \ diameter in inches) \4000 ) kjtu'VLr ( se^ec^ an appropriate roughness measure -(). from Table rllL'4f?.la^i've roughness, </D, in which D is pipe diameter in feet; .($) 'Number from formula on page 339; (4) use Reynold^ Number T' ^*3^7j; w^CMr^EBi55S;rp|?`i6ffr[VfMf5=B'iiirr^S^SSi^