Monroe L. Weber-Shirk S chool of Civil and Environmental Engineering Prelim 1 Review

Bernoulli vs. Energy ä What is the difference between the Bernoulli Equation and the Energy Equation? ä Give examples of when each equation could be used. ä What is the difference between the Bernoulli Equation and the Energy Equation? ä Give examples of when each equation could be used.

Darcy-Weisbach vs. Hazen- Williams ä Which equation is dimensionally correct? ä Which equation would you use if you were building a molasses pipeline? Why? ä What is the advantage of Hazen-Williams? ä Which equation is dimensionally correct? ä Which equation would you use if you were building a molasses pipeline? Why? ä What is the advantage of Hazen-Williams?

Contraction ä Why do some contractions have head loss? ä Where does this loss occur? ä Is the Bernoulli equation applicable upstream of a contraction? ä Over long distances ä Over short distances ä Downstream of a contraction? ä Why do some contractions have head loss? ä Where does this loss occur? ä Is the Bernoulli equation applicable upstream of a contraction? ä Over long distances ä Over short distances ä Downstream of a contraction?

PRV ä Why (and where) would you use a pressure regulating valve in a water distribution system? ä Why not simply use a head loss element (like a valve that is partly closed)? ä Why (and where) would you use a pressure regulating valve in a water distribution system? ä Why not simply use a head loss element (like a valve that is partly closed)?

Multiport Diffuser ä What is the first approximation for the discharge from the first port? ä What is the first approximation of the required piezometric head at the first port? ä Why is the approximation incorrect? ä Why does the discharge from the ports tend to increase for the last ports of the diffuser? ä What is the first approximation for the discharge from the first port? ä What is the first approximation of the required piezometric head at the first port? ä Why is the approximation incorrect? ä Why does the discharge from the ports tend to increase for the last ports of the diffuser?

Multiport Diffuser: Solution ä Starting with the first port and proceeding to the last port... ä Calculate the discharge from port i ä Calculate velocity change in diffuser past port i ä Calculate the piezometric head increase across port i ä Calculate the piezometric head decrease between ports i and i+1 ä Calculate the piezometric head at port i+1 ä Starting with the first port and proceeding to the last port... ä Calculate the discharge from port i ä Calculate velocity change in diffuser past port i ä Calculate the piezometric head increase across port i ä Calculate the piezometric head decrease between ports i and i+1 ä Calculate the piezometric head at port i+1

Multiport Diffuser: Solution ViVi ViVi HGL (_________ in pressure) (__________ in pressure) Known from previous step increase decrease

Pumps ä Why are pumps less efficient that turbines? ä The maximum head produced by an oil pump is 200 kPa. The diameter of the impeller is 0.5 m. What is the pump rpm? ä Why are pumps less efficient that turbines? ä The maximum head produced by an oil pump is 200 kPa. The diameter of the impeller is 0.5 m. What is the pump rpm?

+z NPSH problem from practice prelim Lake Water Surface Part E? Steel Pipe 100 m Plastic Pipe 3100 m Pump inlet length of intake pipeline is 3200 m 1 m Motor  f= 0.018D= 1.6 m

LSC Pump and Pipeline ä The lake source cooling intake pipe will have 3.1 km of plastic pipe (HDPE) lying on the bottom of the lake. The plastic pipe and steel pipe will be 1.6 m in diameter and will have a friction factor of approximately The entrance loss coefficient is 1. You may ignore other minor losses. The proposed plastic pipe can withstand a maximum negative pressure differential of 25 kPa (produced by the pumps taking water out of the wet pit) between the inside and outside of the pipe. The pump curve for a possible pump is given below. This pump operates at a constant 210 rpm.

Wet Pit Depth ä The pump is a vertical turbine pump, and pumps water out of a large wet pit, or open pool. If the pump intake is 1 m from the wet pit floor, how deep (relative to the lake surface) does the pit have to be for a flow of 2.2 m 3 /s. NPSHr includes intake losses for vertical turbine pumps. (reservoir depth is 5.32 m: head loss is 2.32 m and from NPSHr the pump must be submerged by 2 m.)

NPSH r

Major losses problem ä Cornell Utilities wants to know what the head loss will be in PVC pipe when water is flowing at 2.3 m 3 /s in a 1.5 m diameter pipe. The answer needs to be as accurate as possible. You are employed by Genoa, a manufacture of PVC pipe. ä No one has ever done a full scale test on PVC pipe that is this large. ä Come up with as many solution methods as possible. Rank the methods for accuracy and for feasibility. ä Cornell Utilities wants to know what the head loss will be in PVC pipe when water is flowing at 2.3 m 3 /s in a 1.5 m diameter pipe. The answer needs to be as accurate as possible. You are employed by Genoa, a manufacture of PVC pipe. ä No one has ever done a full scale test on PVC pipe that is this large. ä Come up with as many solution methods as possible. Rank the methods for accuracy and for feasibility.

Solutions ä Assume pipe is hydraulically smooth ä measure roughness with microscope ä measure roughness by measuring head loss in smaller piece of pipe ä full scale test ä Hazen-Williams ä Assume pipe is hydraulically smooth ä measure roughness with microscope ä measure roughness by measuring head loss in smaller piece of pipe ä full scale test ä Hazen-Williams ease accuracy