Document ZBVY5357dMQ2K1k7oOVq1r8kJ

F riction and Cap, !i II !! i?i'l8l 1 i-ti 648 CHAPTER 31 1950 Guide 4 SSSS 88SS 8SS3 3333 S3S3 SS3S 88RR RRS3 S33S SSS 3 3 8 R ia 3 s 8 3 3 s 3 33 3 3 S 3 3 is 555 SSSJSSS 2= S3 SSS 1115 1155 551 15 lids ssis sss 5555 5555 5515 sss ic asss rkrr ssss ass ssss ssaa rrrr rrrs sss S3 ISSSS 68SR RKRR ERRS SRS SESS 3883 SSSS 8S8E ERRR RRR 1 1111 S52S 5115 3333 3333 553 33 SSSS 83SS 3833 3888 88RK ERR *0 4(1SSS 33SS ESSS SS88 3338 8888 SSS ^ ^ M CT W Ot OO ^ W 9 Oi fwW W . 3333 8233 SSE3 88SS 8333 8888 SSS 5 5555 isss ssis ssss ssss ssss sss , 33 3353 3838 E33S SE33 SSSS 3883 SSS 3I5 338'1 33S3 3833 SSSS 8888 8388 SSS SS33 3333 3333 8338 S33S SEES 8888 338- 8 SS33 3333 3333 3333 3333 3888 SSSS SSS 15 Ills 3333 3333 3333 8838 8223 33SS BBS Sss aa aa sss; ssss sss; ssss.ssss sss ,5111 5111 5151 llll.llls 5111 5115 1115 151 1 5515 1551 5111 1111 5111 1511 5111 1155 52 ? a 555 5115 5151 1111 1111 1151.1111 1111 1111 111 1111 5551 sail ssss ssss ssss ssss, 3333 3333 333 4 SSSS -SSSS SSSS SSSS SSSS SSSS SSSS KSS3 ssss sss Air Duct Design 649 where hr = the total shook pressure loss, feet of fluid flowing. . a = velocity of air, feet per second. v* -- -- the velocity pressure corresponding to the mean velocity of flow, feet of fluid flowing. c' = an empirical factor based on experiments and termed shock factor or loss coefficient. It can be seen from Equation 4 that the shock factor is independent of both density and the unit used, and that it represents the number of velocity heads lost at the conduit transition or bend. Values of the shock factor for various duct elements are sometimes tabulated.8'7 It should be kept in mind, however, that absolutely reliable shock factors have not yet been fully established for all duct elements, and that difficulties have been en countered in correlating experimental data of different investigators. A comprehensive-study of the loss factors of duct elements is being conducted by the A;S.H.V.E. Research Laboratory for the purpose of obtaining exact data. For standard air Equation 4 changes to: . where Hr = total shock pressure loss, inches of water. Vm = velocity of air stream, feet per minute. C = an experimentally determined constant (shock loss coefficient)- Fig. 4, which' shows diagrammatically the^relation of velocity pressure to velocity for standard air (Fm = 4005 Vh,), can be conveniently used to find the total shock pressure loss for any duct element with known shock loss coefficient C. ' : * ............. ' '' Shock losses are independent of the roughness of the duct walls and1 therefore cannot be computed correctly as friction losses. It is, neverthe-