Page 410 - Civil Engineering Formulas

HYDRAULICS AND WATERWORKS FORMULAS 337

3
3
where Q flow rate, ft /s (m /s)
c empirical discharge coefficient dependent on throat velocity and
diameter
d diameter of main section, ft (m)
1
d diameter of throat, ft (m)
2
h pressure in main section, ft (m) of water
1
h pressure in throat section, ft (m) of water
2
HYDROELECTRIC POWER GENERATION

Hydroelectric power is electrical power obtained from conversion of potential
and kinetic energy of water. The potential energy of a volume of water is the
product of its weight and the vertical distance it can fall:

PE WZ (12.141)

where PE potential energy
W total weight of the water
Z vertical distance water can fall
Power is the rate at which energy is produced or utilized:

1 horsepower (hp) 550 ft lb/s
1 kilowatt (kW) 738 ft lb/s
1 hp 0.746 kW
1 kW 1.341 hp

Power obtained from water flow may be computed from

%Qwh %Qh
hp (12.142)
550 8.8
%Qwh %Qh
kW (12.143)
738 11.8

where kW kilowatt
hp horsepower
3
3
Q flow rate, ft /s (m /s)
3
3
w unit weight of water 62.4 lb/ft (998.4 kg/m )
h effective head total elevation difference minus line losses due to
friction and turbulence, ft (m)
% efficiency of turbine and generator