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


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)


Frictionhead

Flow

Introduction

In most cases:Total head = Static head + friction head


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