ROTAMETER

Presented By:Momina Noor (M12-PG01)

Mahnoor Butt (M12-CE16)

Sabahat Tahir (M12-CE12)

Farah Naeem (M12-CE55)

Objective:

The purpose of this presentation is to develop a better understanding of rotameter, its working and its use on domestic and industrial scale.

Contents: HistoryRotameter Working Principle Construction Working Derivation & GraphAdvantages & DisadvantagesUses

History: The history of variable-area meters dates

to 1908 when they were invented by German engineer Karl Kueppers in Aachen, Germany.

Felix Meyer recognized the commercial potential of Kueppers’ invention, and in 1909 founded “Deutsche Rotawerke” in Aachen.

Kueppers invented the special shape for the inside of the glass tube that realized a symmetrical flow scale.

Rotameter-Variable area meter What is rotameter ? A device used to measure fluid flow, in which a float rises in a tapered vertical tube to a height dependent on the rate of flow through the tube.

Working Principle: It is a variable area

meter which works on the principle of upthurst force exerted by fluid and force of gravity.

Construction: Graduated tapered

metering glass tube.

Float

Tapered tube:Safety-shielded glass tube

are in general use for measuring both liquids and gases.

Metal tubes are used where opaque liquids are used or temperature or pressure requirement is quite high.

Plastic tubes are also used in some rotameter designs due to their lower cost and high impact strength.

Float:Floats may be constructed of metals of

various densities from lead to aluminum or from glass or plastic.

Stainless-steel floats are common ones.Float shapes and proportions are also

varied for different applications.For small flows floats are spherical in

shape.

Different floats:

Working: Fluid enters the tapered tube,

some of the fluid strikes directly the float. Some of the fluid passes from sides.

Two forces are acting in this case:

Upthurst Force (Buoyancy) Weight of the float Annular space increases due to

increase in area of the tube.When equilibrium is established

the float comes to rest.

Measurement of flowrate: The flowrate is

measured directly from calibrated scale.

The reading is noted generally from ending point of cap of the float.

Formula:The pressure difference over the float −∆P, is

given by:

If area of the annulus between the float and

tube is A2 and the cross-sectional area of the tube is A1, then equation for orifice will become:

f

gρρf

A

VP f

2

1

2

2

1

2

AA

PACG D

Formula:Substituting the value of −∆P :

2

1

2

2

1

2

AA

A

gVACG

f

ffD

Graph:

Range, Repeatability & Accuracy Wide rangeability 5:1 – 12:1 High repeatability 0.5 – 1 %

Low accuracy 2 – 3 %

Advantages: No external power or fuel.

Manufactured of cheap materials.

Since the area of the flow passage increases as the float moves up the tube, the scale is approximately linear.

Disadvantages: Impact of gravity.

Accuracy of rotameter.

Uncertainty of the measurement.

Conclusion: Rotameter is used:

To measure the flow of gases and air at low flowrates.

When cost is the main consideration.

When high accuracy is not required.

"You mustn't be too rigid when doing Fluid mechanics."

THANK YOU ...

Question Answer Session