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Transcript of Pumps
Gandhinagar Institute Of Technology
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Active Learning Assignment
Electrical F1
PUMPS
Elements of Mechnical Engineering(2110001)
Prof. Naman Dave
Name ENROLLMENT NO. Himal Desai 140120109008Abhishek ChokshiHarsh Dedakia
PREPARED BY:-
140120109005140120109012
Introduction
Objective of pumping systemWhat are Pumping Systems
• Transfer liquid from source to destination
• Circulate liquid around a system
Introduction
• Main pump components• Pumps• Prime movers: electric motors, diesel engines,
air system• Piping to carry fluid• Valves to control flow in system• Other fittings, control, instrumentation
• End-use equipment• Heat exchangers, tanks, hydraulic machines
What are Pumping Systems
Introduction
• Head• Resistance of the system• Two types: static and friction
• Static head• Difference in height between
source and destination• Independent of flow
Pumping System Characteristics
destination
source
Static
head
Statichead
Flow
Introduction
• Static head consists of• Static suction head (hS): lifting liquid relative to
pump center line• Static discharge head (hD) vertical distance
between centerline and liquid surface in destination tank
• Static head at certain pressure
Pumping System Characteristics
Head (in feet) = Pressure (psi) X 2.31 Specific gravity
Introduction
• Friction head• Resistance to flow in pipe and fittings• Depends on size, pipes, pipe fittings, flow
rate, nature of liquid• Proportional to square of flow rate• Closed loop system
only has friction head(no static head)
Pumping System Characteristics
Frictionhead
Flow
Introduction
In most cases:Total head = Static head + friction head
Pumping System Characteristics
Systemhead
Flow
Static head
Frictionhead
Systemcurve
System head
Flow
Static head
Friction head
Systemcurve
Classification of pumps
Reciprocating positive displacement pumps • use back and forth movement of mechanical parts Water is for most practical purposes incompressible.
Consequently, if a close fitting piston is drawn through a pipe full of water, it will displace water along the pipe.
Similarly, raising a piston in a submersed pipe will draw water up behind it to fill the vacuum which would otherwise occurs.
Basic relationships between the output or discharge
rate (Q), piston diameter (d), stroke or length of piston travel (S), number of strokes per minute (n), and the volumetric efficiency, which is the percentage of the swept volume that is actually pumped per stroke ( η vol )
Swept area of the piston is A =
The swept volume per stroke will be V= AS The discharge per stroke will be q = V η vol The pumping rate (per minute) is Q = nq
42πd
• These are group of devices which utilizes the displacement principle for lifting or moving water, but which achieve this by using a rotating form of displacer (gears, vanes, lobes or screws).
• use gears and vanes to move discrete part of water.
• These generally produce a continuous, or sometimes a slightly pulsed, water output these pumps tend themselves readily to mechanization and to high speed operation than reciprocal displacement pumps.
Rotary positive displacement pumps
• use the centrifugal force of rotating devices (called impellers) to increase the kinetic and pressure energy of the water.
• Depends on propelling water using a spinning impeller of rotor.
• There are two main types of rotodynamic pumps (centrifugal pumps), i.e. ◦Volute centrifugal pumps◦Turbine centrifugal pumps
Rotodynamic (centrifugal) pumps
Centrifugal Pump
Electric Motor
Centrifugal Pump
ElectricMotor
Reciprocating and rotary pumps are called positive displacement pumps, while centrifugal pumps are called variable displacement pumps in which the delivery head varies with the quantity of water pumped.
Axial flow pump
Radial flow (Centrifugal pumps)
Typical mixed flow pump
In centrifugal pumps the energy is imparted to the water by a unit of rotating vanes called an impeller, which are located in a stationary body called the casing.
CASING Water is pushed into the center or eye of the impeller by
atmospheric or water pressure and set into a rotary motion by the impeller.
-The rotating movement causes a centrifugal force to act upon the water, which drives the water outward, between the vanes of the impeller, into the surrounding casing from where it moves to the pump outlet.
-Different types of casing: a)Single volute, (b) Double volute, and (c). Diffuser turbine casing.
PUMPING THEORY-CENTRIFUGAL PUMPS
Impellers can be classified according to the direction of flow through the impeller in relation to the axis of rotation as (a) radial, (b) axial or (c) mixed flow.
Where high flows at low heads are required (which is common with irrigation pumps), the most efficient impeller is an axial flow one.
Impellers can also be classified according to their design into (a) open (consist only vanes attached to the hub with out shroud/side-wall), (b) semi-open (have one shroud) and (c) enclosed (have shrouds (sidewalls) enclosing the waterways between vanes) impellers as shown in figure.
IMPELLERS
Impellers
Pumps can not pump vapors! The satisfactory operation of a pump requires that
vaporization of the liquid being pumped does not occur at any condition of operation.
NET POSITIVE SUCTION HEAD-NPSH
Net Positive Suction Head Available, NPSHA
Net Positive Suction Head Available is a function of the system in which thepump operates. It is the excess pressure of the liquid in feet absolute over its vaporpressure as it arrives at the pump suction, to be sure that the pump selected does not cavitate.
Head to Feed Pump Subcooling before PumpTo overcome suction head
HeadDesigned into Installation
HX
Cool a few DegreesTo overcome suction head
Piston Pumps
Gear Pumps
food applications, because they handle solids without damaging the pump.
Particle size pumped can be much larger in these pumps than in other PD types
Lobe Pumps
Screw Pump
THANK YOUFOR ATTENTION