Extended Bernoulli

BERNOULLI’S EQUATION Fluid Flow Most techniques for evaluating head loss due to friction are empirical (based almost exclusively on experimental evidence) and are based on a proportionality constant called the friction factor (f), which will be discussed in the next section. Example: Extended Bernoulli Water is pumped from a large reservoir to a point 65 feet higher than the reservoir. How many feet of head must be added by the pump if 8000 lbm/hr flows through a 6-inch pipe and the frictional head loss is 2 feet? The density of the fluid is 62.4 lbm/ft³, and the cross-sectional area of a 6-inch pipe is 0.2006 ft². Solution: To use the modified form of Bernoulli’s equation, reference points are chosen at the surface of the reservoir (point 1) and at the outlet of the pipe (point 2). The pressure at the surface of the reservoir is the same as the pressure at the exit of the pipe, i.e., atmospheric pressure. The velocity at point 1 will be essentially zero. Using the equation for the mass flow rate to determine the velocity at point 2: m₂ rA2v2 v₂ m₂ rA2 v₂ 8000^lbm hr æ ç è ö ÷ ø 62.4^lbm ft³ (0.2006 ft²) v₂ 639 ft hr æ ç è ö ÷ ø 1 hr 3600 sec v₂ 0.178 ft sec HT-03 Page 26 Rev. 0