11

CTC 450CTC 450

PumpsPumps

http://www.esi-group.com/SimulationSoftware/CFD_ACE/blood.html

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ObjectivesObjectives

Ability to simplify pipe systems by use Ability to simplify pipe systems by use of equivalent pipes (parallel and of equivalent pipes (parallel and series)series)

Know what types of pumps are Know what types of pumps are availableavailable

Ability to develop a pump Ability to develop a pump performance curve performance curve

Ability to develop a simple system Ability to develop a simple system curvecurve

Equivalent PipesEquivalent Pipes

An imaginary conduit that replaces a An imaginary conduit that replaces a section of a real system such that section of a real system such that the head losses are identical for the the head losses are identical for the quantity of flowquantity of flow

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Equivalent Pipe to ReplaceEquivalent Pipe to Replace Parallel Pipes-Ex 4-19; page Parallel Pipes-Ex 4-19; page

113113 Determine an equivalent pipe Determine an equivalent pipe 10001000’ in length to ’ in length to

replace two parallel pipes (8” pipe @ replace two parallel pipes (8” pipe @ 10001000’ and 6” ’ and 6” pipe @ pipe @ 800800’)’)

1.1. Assume a head loss (10’) and calculate HGL slopes Assume a head loss (10’) and calculate HGL slopes of both pipes (10’/of both pipes (10’/10001000’) and (10’/’) and (10’/800800’). Using ’). Using diameters and HGL slopes calculate Q in both pipes diameters and HGL slopes calculate Q in both pipes from Hazen-Williams nomograph (550 & 290 gpm)from Hazen-Williams nomograph (550 & 290 gpm)

2.2. Total Q’s (840 gpm)Total Q’s (840 gpm)

3.3. Use nomograph w/ HGL slope (10’/Use nomograph w/ HGL slope (10’/10001000’) and total ’) and total Q to get equivalent pipe size (answer=9.4”)Q to get equivalent pipe size (answer=9.4”)

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Equivalent Pipe to ReplaceEquivalent Pipe to Replace Serial Pipes Serial Pipes

Determine an equivalent pipe 2000’ in length to Determine an equivalent pipe 2000’ in length to replace three pipes in series (8” pipe @ 400’ , 9.4” replace three pipes in series (8” pipe @ 400’ , 9.4” pipe @ 1,000’ and 10” pipe @ 600’)pipe @ 1,000’ and 10” pipe @ 600’)

1.1. Assume a flow (500 gpm) and calculate head Assume a flow (500 gpm) and calculate head losses in all 3 pipes from Hazen-Williams equation losses in all 3 pipes from Hazen-Williams equation or nomograph (3.3+3.8+1.6=8.7’ per 2000’)or nomograph (3.3+3.8+1.6=8.7’ per 2000’)

2.2. Determine head losses per 1000’ (4.4’ per 1,000 ft)Determine head losses per 1000’ (4.4’ per 1,000 ft)

3.3. Use nomograph w/ calculated head loss and Use nomograph w/ calculated head loss and assumed Q to get equivalent pipe size assumed Q to get equivalent pipe size (answer=9.2”)(answer=9.2”)

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PumpsPumps

Machines that do work on fluidsMachines that do work on fluidsPumps increase the pressure in a Pumps increase the pressure in a

pipe, or lift water, or move water pipe, or lift water, or move water Axial-flowAxial-flow

Flow is parallel to axisFlow is parallel to axisBest suited for low heads and high flowsBest suited for low heads and high flows

Radial-flow (centrifugal)Radial-flow (centrifugal)Flow is perpendicular to axisFlow is perpendicular to axisBest suited for high headsBest suited for high heads

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Pump Performance CurvesPump Performance Curves

Obtained by experimental data and Obtained by experimental data and plotted on graphs (usually for a plotted on graphs (usually for a specific pump at a specific rotation specific pump at a specific rotation speed)speed)Head versus dischargeHead versus dischargeEfficiency versus dischargeEfficiency versus discharge

Shutoff head is the pressure head if Shutoff head is the pressure head if discharge is completely stopped (Q=0)discharge is completely stopped (Q=0)

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Pump EfficiencyPump Efficiency

Efficiency is defined as the motor Efficiency is defined as the motor power input divided by the power power input divided by the power outputoutput

Centrifugal pump efficiency is usually Centrifugal pump efficiency is usually in the range of 60-85%in the range of 60-85%

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Pump Curve (1750 rpm)

0

50

100

150

200

250

0 1000 2000 3000 4000 5000

Discharge (gpm)

He

ad

(ft

) o

r E

ffic

ien

cy

(%

)

Head-DischargeCurve

Efficiency

1010

Variable Speed PumpsVariable Speed Pumps

Pumps which can be operated at Pumps which can be operated at variable speedsvariable speeds

Have 2 pump curves (high speed and Have 2 pump curves (high speed and low speed) and pump can operate low speed) and pump can operate between the curvesbetween the curves

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System Head CurvesSystem Head Curves

Accounts for static head and friction losses Accounts for static head and friction losses in the systemin the system

Static head (lifting of water to a higher Static head (lifting of water to a higher elevation)elevation)

Friction losses (increases as the flow Friction losses (increases as the flow increases)increases)

In real systems, outputs are variable and the In real systems, outputs are variable and the system head “curve” is actually a “band”system head “curve” is actually a “band”

Pump should be operated at the intersection Pump should be operated at the intersection of the system-head curve and the head-of the system-head curve and the head-discharge curvedischarge curve

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System Head Curve ExampleSystem Head Curve Example

See page 108 (Figures 4-14 & 4-15)See page 108 (Figures 4-14 & 4-15) Curve 1 – If pump is used to “raise” water Curve 1 – If pump is used to “raise” water

from a lower source to a higher tank from a lower source to a higher tank (outlet 1)(outlet 1)

Curve 2 – If pump is used to raise water to Curve 2 – If pump is used to raise water to a load center (outlet 2)a load center (outlet 2)

Actual operation can vary between the Actual operation can vary between the curves depending on how much flow is curves depending on how much flow is discharging from outlet 1 and 2discharging from outlet 1 and 2

System Curve-Simple System Curve-Simple ExampleExample

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System CurvesSystem CurvesCurve 1: Pump to StorageCurve 1: Pump to Storage

Curve 2: Pump to LoadCurve 2: Pump to Load

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What do H1 and H2 represent?

How do you calculate the increase in head based on the pumping rate?

Pump & System Head Curves Pump & System Head Curves ExampleExample

1515

Pump operates at A when pumping only to storage

Pump operates at B when pumping only to the load

Pump operates at C when pumping partly to the storage tank and partly to the load

Example-Discussion of PumpsExample-Discussion of Pumps

Small systemSmall systemUse 2 constant speed pumps with same Use 2 constant speed pumps with same

capacitycapacityIntermittently pump to tankIntermittently pump to tankControl by fluctuation of water level in Control by fluctuation of water level in

tanktankElevated storage maintains pressure in Elevated storage maintains pressure in

the systemthe system

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Example-Discussion of PumpsExample-Discussion of Pumps

Large systemLarge systemUse 3 pumps in parallel (1 as standby)Use 3 pumps in parallel (1 as standby)Operate pumps individually or in Operate pumps individually or in

combination to meet demandcombination to meet demand

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1818

http://www.armstrongpumps.com/present_newsletter.asp?groupid=1&nlfile=00_00_054

1919

Pump Operation ScenariosPump Operation ScenariosSingle PumpSingle Pump

Constant speed (as flows change the Constant speed (as flows change the pump pressure changes)pump pressure changes)

Variable speed (maintains a constant Variable speed (maintains a constant pressure over a wide range of flows pressure over a wide range of flows by varying the rotational speed of by varying the rotational speed of the pump impellor)the pump impellor)

2020

Pump Operation Scenarios Pump Operation Scenarios Multiple PumpsMultiple Pumps

Multiple pumps – parallel – one as Multiple pumps – parallel – one as “standby”“standby”

Multiple pumps – series – to increase Multiple pumps – series – to increase discharge headdischarge head

PumpsPumps

http://www.simerics.com/http://www.simerics.com/simulation_gallery.htmlsimulation_gallery.html

2121

Next Lecture

Manning’s Equation (open channel flow)

Rational Method

MidtermMidterm

Open Book/Open NotesOpen Book/Open NotesThursday, October 10Thursday, October 10thth (10 am-Noon) (10 am-Noon)Will cover lectures 1-9Will cover lectures 1-9

ChemistryChemistry BiologyBiology Fluid StaticsFluid Statics BuoyancyBuoyancy Fluid Flow (continuity, storage)Fluid Flow (continuity, storage) Bernoulli’s/EnergyBernoulli’s/Energy Friction Friction

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