This document discusses rotameters, which are variable area flow meters commonly used to measure flow rates of liquids and gases. It describes the construction, principle, and working of rotameters. The document is divided into four parts: (1) introduction to variable area meters and details on rotameters, (2) pressure drop and flow rate calculations, (3) modifications and advantages/disadvantages, and (4) applications of rotameters such as in control panels, laboratories, and various industries.

2.  Awais Ahmad RP14-CE21
 Rana Aown Haider RP14-CE63
 Hassan Haider Zaidi RP14-PG15
 Usman Ahmad Khan RP14-PG07

4. Part 2
 Pressure drop
 Flow rate
 Coefficient of discharge
Part 1
 Introduction to variable area meters
 Rotameter
 Construction
 Principle
 Working
Part 3
 Modifications
 Advantages
 Disadvantages
Part 4
 Applications

5. Part 1
Introduction to variable area meters
Rotameter
Construction
Principle
Working

6.  In the Variable area flowmeters
“the drop rate in the pressure is
constant and the flowrate is a function
of area of constriction”.
 Most commonly Known variable area
meter is known as “ROTAMETER”.

7. Tapered tube

8. “The buoyant force exerted on
an immersed object is equal to
the weight of liquid displaced
by that object.”

9.  Vertical Installation
 Liquid Flow Direction (bottom to top)
 Buoyancy force
 Impact of Gravity
 Annular space
 Equilibrium

11. Part 2
 Pressure drop
Flow rate
Coefficient of discharge

12.  The pressure drop arises from the conversion of pressure energy to kinetic
energy and from frictional losses which are accounted for in the coefficient of
discharge.
 The pressure difference over the float -∆𝑃, is given by:
−∆𝑃 =
𝑽 𝒇 𝝆 𝒇−𝝆 𝒈
𝑨 𝒇
This equation shows the pressure difference across the float is equal to its weight
in the fluid divided by its maximum cross sectional area.

13. Rotameter is considered as an orifice meter with the variable
aperture, thus the formula used for orifice with slight changes
can be used.

14. CD=0.98
CD=0.79
CD=0.64

15. Part 3
Modifications
Advantages
Disadvantages

16. Stainless steel tube
rotameter (For high
temperatures fluids) Magnetic float (for
turbid fluids)

17. Use of spring in
Horizontal rotameters
Polymeric rotameters
(for gases)

18. Calibration of Rotameters

19. Low cost
Low Pressure drop
Rangeability is better
It is suitable for small flowrates
It also measures the flowrate of corrosive fluids
it is easily equipped with alarms and switches or any transmitting device

20. It is difficult to handle the glass tube type.
It must be mounted vertically.
It requires in line mounting.
Accuracy = ± 0.5 to 10%
It is limited to low temperatures.
Generally it is limited to small pipe services.

21. Part 4
Applications

22.  Control panels
 Control in research laboratories
 Measurement & control on machinery
 Pilot plants
 Water purification (Osmosis)
 Control of gas burners
 Flow control for industrial refrigeration
 Chemical / pharmaceutical / cosmetic industry
Lab scale rotameter

23. Pilot plants

24.  Measurement & control on machinery
 Control in research laboratories

25. Medical oxygen regulator with
rotameter
Bypass rotameter

26. Alarm system