1 - Alaska Energy Data Inventory

Concrete Lined Port i on of Tunne 1. The concrete 1 i ned portionof the tunnel is 9.0 ft in diameter. With our maximum discharge of 500ft 3 /s that was assumed early on in the design process, we obtain aReynold's Number of 3.9 x 10 6 • The intersection of the Reynold'sNumber with the RPL on HOC chart 224-1 results in a friction factor of0.016. The VKP formula is independent of the Reynolds Number but aneffect ive roughness has to be assumed. . The fo 11 owi ng chart ill ustratesthe friction factors obtained from the VKP with the assumption of variouspipe roughnesses.Effective Roughnessks(ft ).0020.0025.0030.0040Relative RoughnessOiameter/Ks4500360030002250Oarcy-Weisbachfriction factorIIfll0.01400.01500.01550.0162The friction factor does not reach the maximum value (0.0160)obtained by using the RPL until Ks is equal to 0.0040. HOC 224-1recommends a Ks of .002 for circular concrete conduits as being aconservative value which would result in a friction factor of 0.0140 whichis well below the 0.0160 obtained from the RPL.HOC 224-1 does indicate that a Ks of 0.00397 was recordea at PineFlat but this was for concrete lining formed with wood (longitudinalplanking). Concrete lining in tunnels is placed with steel forms,resulting in much lower values of Ks (0.00001 to 0.00061).c Steel Penstock. The Reynolds Number for the recommended 6 ftdiameter penstock with 500 ft3/s discharge is 5.9 x 10 6 , resulting in amaximum friction factor of .0146 based on the RPL. Using the VKP formularesults in friction factors of 0.00087 and 0.0100 with corresponding Ksvalues of 0.0001 and 0.0002 respectively. HOC 224-1/1 recommends aconservative value of .0001 for vinyl or enamel coated steel pipe which isBl-20