- P (ft-lb/s) = C (efficiency) 62.4 (lb/ft3) Q (ft3/s) ht (ft)
Assume C = 0.8
P (ft-lb/s) = 0.8 × 62.4 × 70 × 45
P = 157,248 ft-lb/s
1 HP = 550 ft-lb/s
P = 157,248 / 550 = 285.9 HP
1 HP = 0.746 KW
P = 285.9 × 0.746 = 213 KW
- D = 0.6 m
Q = 150 L/s = 0.15 m3/s
V = Q / [(π/4) D2] = 0.150 / (0.7854 × 0.6 2 ) = 0.53 m/s
For T = 20o, ν = 1.0 × 10-6 m2/s
Reynolds number: R = VD / ν = 0.53 × 0.6 / (1.0 × 10-6) = 318,000
From Fig. 5-5: ks / D = 0.00058
From Fig. 5-4: f = 0.018
hf = f (1000/D) V2/(2g) = 0.018 × (1000/0.6) [(0.53) 2/(2 × 9.81)]
hf = 0.429 m.
- ν = 1.0 × 10-6 m2/s
Assume f = 0.018
Q = 0.15 m3/s
hf = f (L/D) (Q/A)2 / (2g)
hf = f (L/D) [Q/(πD2/4)]2 / (2g)
D5 = f Q2 / [(π/4)2 (2g) (hf / L)]
D5 = 0.018 × 0.152 / [(π/4)2 (2 × 9.81) (0.00043)]
D = 0.6 m.
Now compute a more accurate f.
From Fig. 5-5: ks / D = 0.00058
V = Q/A = 0.15 / [(3.1416/4) 0.62] = 0.53 m/s
Re = VD/ν = 0.53 × 0.6 / 0.000001 = 318,000
From Fig. 5-4: f = 0.018
Assumption was correct.
- From Fig. 5-6, for head loss 2.5 ft per 1000 ft, and D = 24 in, Q = 14 cfs.
The result using the online calculator is: Q = 13.678 cfs.