Transcript THERMODYNAMICS LAB: Introduction to EES

Fluid Mechanics LAB:
Dynamic Pumps and Cavitation
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Dynamic Pumps
Kinetic or dynamic pumps add energy to the
fluid by accelerating it through the action of
a rotating impeller.
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Classification of dynamic pumps
Kinetic or dynamic
Pumps
Radial Flow
(Centrifugal)
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Axial flow
(propeller)
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Mixed flow
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Performance of Centrifugal Pumps
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System and Pump Operating Point
The operating point of the system is changed by
flow control valve
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Cavitation
Cavitation is the formation of vapor cavities
due to the decrease of the suction pressure
If below
to a value below the vapor pressure.
vapor
pressure,
cavitation
occurs
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Net Positive Suction Head
NPSH Available  hsp  hs  h f  hvp
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Pump efficiency
• The overall pump efficiency is a product of
the volumetric efficiency and the
mechanical efficiency
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Pump efficiency
Actual _Volume_ FLow_ Rate
Volumetric_ Efficiency =
´100%
Theoretical _Volume_ FLow_ Rate
QA

 100%
QT
Theoretical _ Power _Out
Mechanical _ Efficiency =
´100%
Actual _ Power _ In
=
P´ QT
´100%
N ´T
(P is in Pa; QA and QT are in m3/s; T is in N-m; N
is in Rev Per Second (RPS))
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Pump efficiency
Overall Efficiency = Vol.Efficiency x Mech.Efficiency
Actual _ Pump_Output _ Power
=
Actual _ Pump_ Input _ Power
Actual Power Out = P x QA
Actual Power In
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= Electrical Power Input (Watts)
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Suction Discharge Pressure Input
Trail Flow Rate
Pressure Pressure Difference Current
No.
(GPM)
(psig)
(psig)
(psig)
(Amps)
Input
Voltage
(V)
1
2
3
4
5
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Trail No.
Frequency Flow Rate
(Hz)
(GPM)
1
15
2
20
3
25
4
30
5
35
6
40
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Suction
Pressure
(psig)
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Discharge
Pressure
(psig)
Pressure
Difference
(psig)
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References
• Applied Fluid Mechanics, Robert L. Mott
• www.gewater.com
• www.pumpworld.com
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