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SELECTION OF WATER PUMPS

Dept: MECHANICAL ENGINEERING File: Word(doc) Chapters: 1-5 Views: 1

Abstract

The aim of this project is to capture the utilization of pumps for various uses and to maximize the principle of selection of water pumps through the application and pump selection for specific uses our society will transformed wholestically to an industrious nation in the clean water supply for supply for domestic, industrial and down stream sector. Pump parameters and selection are analyzed categorically to enable a good conception in practical. Centrifugal pumps can also be found as fuel as cooling water pumps for example diesel engine etc. Also positive displacement pumps are found a device in fuel and oil pump in most automobile and hydraulic systems.

INTRODUCTION

A pump is a device that moves fluids (liquid or gases) or sometimes slurries, by mechanical action.  Pumps can be classified into three major groups according to the method they use to move the fluid; direct lift, displacement and gravity pumps.

There are two types of pump which are generally used in industrial processes; positive displacement pump and centrifugal pump. It is important to choose a suitable type of pump base on process requirement and fluid process properties.  The types and application of pumps are explained in detail in the proceeding chapters.

Pumps operate by some mechanism (typically reciprocating or rotary), and consume energy to perform mechanical work by moving the fluid. It operate in many energy sources, including manual operation, electricity, engines, or wind power, come in many size, from microscopic for use in medical applications to large industrial pumps.

Mechanical pumps serve in a wide rang of applications such as pumping water from well aquarium filtering, pond filtering and aeration in can industry for water cooling and fuel injection, in the energy industry for pumping oil and natural gas or for operating cooling towers.

BACKGROUND OF STUDY

Engineering use pumps to deliver a liquid or gas to a specific place at a required rate/.  Liquids and gases are known as fluid.  A pump is used to change the elevation, velocity, or pressure of a fluid.  In nature, a fluid will flow naturally from a high place of a low place (like waterfall) or from a high pressure to a low pressure/ from inside a balloon to outside its velocity is often a function of geometry (its shape) and the condition around it.  When a fluid is needed uphill from source like a lake or pond at higher pressure than a source, or at a high rate, an engineer will consider a pump to accomplish the task.

 

 

 

 

 

This lesson will be broken into five basic section: Basic terms, fluid static, flow rate, the Bernoulli equation and a form of the energy for pumps.

 

Basic Terms

Gravity is often mistakenly labeled in force when it is actually an acceleration.  We use Newton’s 2

nd

 Law, F= m x n, to compute the weight where F is the weight, m is the mass and a is the acceleration which is equal to the gravitational pull, g. In metric units, g is equal to 9.81m/s

2

 and English units, g is equal to 32.2ft/s

2

.

            

The density of a fluid is an important factor in our calculations.  The density is a measure of the amount of mass in a given space or volume.  Denser fluid behave in a different manner than less dense fluid (water is denser than air to for example when we talk about pumps, density is important because pumps are used to deliver liquid).Liquid fluid with constant density.  The units for density is metric units are kg/m

3

 and English the units are pound (mass) per feet cubed (1bm/ft

3

).  We have to be very careful about mass units (1bm)  and force unit (1b>f).water has 62.41bm/H

3

 but we use the converted density 1.941bf5

2

.  engineers use the Greek letter ?. (rho) as he symbols for density.

Pressure is the force of a fluid on a surface and measured in unit of force per area.  When we use pressure in out equations we often have to convert it to 1b/ft

2

 to match with our other unit in the equation. To get the atmospheric pressure take 14.7.1bf/m, multiply by 144 in

2

/ft

2

 (12 inches per foot squared / the result is Patm = 2116.81bf/ft

2

.

Fluid Statics

When fluid is not in motion we can make certaining specification of our equations. This is called the study for fluid statics or hydrostatics. We can computer the pressure at any depth in a container as a function for the density, the gravitational constant, atmospheric pressure and the depth.  The absolute pressure is given as Pa= pgh + Patm.

Absolute pressure is the pressure with the atmospheric pressure included.

 

We measure the depth of the fluid. In this figure above, that is 6inches from the bottom. Let assume the fluid is  water so the density is 1.8\941bfS

2

/ft

4

.  The absolute pressure at the bottom of the container isPs = (1.941bfS

2

/ft

4

) x (32.2ft/S

2

0 x (6 in X1/12ft/in) + 2116.81bf/ft

2

Pas = 2148 1bf/ft

2

 or 14.91bf/in

2

(2148/144 to convert ft

2

 to in

2

)

Flow Rate

This is when the fluid is moving or flowing we cannot measure pressure as just a function of the fluid.  We need to define a measurement for the motion at the fluid. We use the velocity of the fluid at the starting point.  The velocity is the measure of the distance travelled in a given time.  The unit is meter per second M/S one of the function of a pump is to deliver a required amount of fluid in a given time.  The amount if usually measured in volume.

The volume flow rate is a measure of how much fluid is delivered in a specific time. The engineering symbols for volume flow rate is s and by formular

Q = v/t  (m

3

/s) where V is the volume and t is time.

Flow rate can be measured in two different ways, also collect a known amount of fluid in a container and time how long it took to fill it as per the equation above or you can use the velocity of the flow and the cross sectional area of the opening the fluid is coming out.

Q=v x A

Where

V     =    Velocity and

A     =     Cross sectional Area

The flow rate in a pipe system will stay the same but the velocity in a individual section can change as a function of the area of the pipe.