Homework Help: Calculating required pump pressure to maintain flowrate in a uniform horizontal pipe

1. May 25, 2010

Dave-RR

1. The problem statement, all variables and given/known data
I am having trouble with calculating the required pump pressure in a horizontal water pipe, 3Km long. i know that the flowrate is 600Kg/s, average velocity 5.6m/s, cross-sectional area of pipe is 0.107143m^2 and losses due to friction average 0.002 per meter

2. Relevant equations
pressure=force/area
bernoulli's equation

3. The attempt at a solution
pressure = (flowrate x G)/cross-sectional area
= (600 x 9.81) / 0.107143 = 54935.92 Pa

i think that this is the pressure at the end of the pipe however i am unsure how to caculate the pump pressure given the frictional loss coefficient. i have had very little teaching in fluid mechanics but have researched Bernoulli's equation however i cannot see how it, is applicable to this problem is there any other equations i could use given the known elements

Last edited: May 25, 2010
2. Jun 5, 2010

zeebek

Re: Calculating required pump pressure to maintain flowrate in a uniform horizontal p

$$\frac{U D}{\nu} = 1.7 \times 10^6$$
$$\Delta P = f \rho U^2 L / D /8 = 0.002 * 5.6^2 * 3000 / 0.3 / 8 \approx 80 \, Pa$$