We can compare with eq 683 for laminar flow which

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Unformatted text preview: length for 1.9 slugs/ft3 and 3 3 (a) 0.00002 ft /s and (b) 0.002 ft /s. Assume smooth walls. Solution Part (a) The viscosity 3.8 10 5 slug/(ft s). The spacing is 2h 4h 0.4 ft. The Reynolds number is VDh ReDh (6.0 ft/s)(0.4 ft) 0.00002 ft2/s 2.4 in 0.2 ft, and Dh 120,000 The flow is therefore turbulent. For reasonable accuracy, simply look on the Moody chart (Fig. 6.13) for smooth walls f 0.0173 hf f L V2 Dh 2g 100 (6.0)2 0.4 2(32.2) 0.0173 2.42 ft Ans. (a) Since there is no change in elevation, p ghf 1.9(32.2)(2.42) 148 lbf/ft2 Ans. (a) This is the head loss and pressure drop per 100 ft of channel. For more accuracy, take Deff 2 3 Dh from laminar theory; then 2 3 Reeff and from the Moody chart read f and p 80,000 0.0189 for smooth walls. Thus a better estimate is 0.0189 hf (120,000) 100 (6.0)2 0.4 2(32.2) 2.64 ft 161 lbf/ft2 1.9(32.2)(2.64) Better ans. (a) The more accurate formula predicts friction about 9 percent higher. Part (b) Compute 0.0038 slug/(ft s). The Reynolds number is 6.0(0.4)/0.002 fore...
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