industrial Instrumentation, Head type flowmeter concept

1. INDUSTRIAL INSTRUMENTATION
- II
UNIT – I
(VARIABLE HEAD TYPE FLOWMETERS)
Lesson - 02

2. VARIABLE HEAD TYPE FLOWMETER
 The Head type flow meters have a common feature
in that they produce a pressure difference when
fluid flow is maintained through them .
 There is a certain linear relationship between the
pressure difference and flow rate of the fluid
 Head type flow meters follows Bernoulli's theorem

3. PRINCIPLE OF HEAD TYPE FLOWMETER
In this ,a restriction is placed in fluid path.
• Restriction creates pressure difference
• The pressure difference indicates flow rate.
• The relationship based on Bernoulli's theorem

4. BERNOULLI’S THEOREM
Bernoulli’s theorem which is also known as Bernoulli’s
principle, states that an increase in the speed of moving
air or a flowing fluid is accompanied by a decrease in
the air or fluid’s pressure or sum of the kinetic (velocity
head), pressure(static head) and Potential energy energy
of the fluid at any point remains constant, provided that
the flow is steady, irrotational, and frictionless and the
fluid is incompressible.
Applicable: Incompressible – Non viscous – steady
Applications: Aerodynamics, Orifice/ Venturi tubes,
Race Car designs etc.,

5. VARIABLE HEAD TYPE – FIXED RESTRICTION

6. BERNOULLI‘S EQUATION
Where,
P=static pressure of fluid at cross section
ρ =density
g=acceleration
V=mean velocity
h=elevation head of the cross section

7.  It states that in a fluid stream, the sum of
Pressure head,
Velocity head
Elevation head
 At a point is equal to their sum at any other point
removed in the direction of flow from the first point plus
loses due to the friction between the two points
o The sum of the pressure head, the velocity head and the
potential head is known as the total head or the total
energy per unit weight of the fluid.
o Thus, the Bernoulli’s equation states that “In a steady,
irrotational flow of an incompressible fluid the total
energy at any point is constant”.

8. FLOW OF INCOMPRESSIBLE FLUIDS IN PIPES

9.  Venacontracta
 It Depends on the flow rate, whole tappings are
fixed, the position of maximum velocity changes
with changing flow rate.
 Basic equations are,
V=K1√h
Q=K1 A√h
W=K1 A√h
β Ratio:
β=d/D
where d=diameter of restriction
D=inside diameter of pipe

10.  Discharge Coefficient(Cd):
Cd=qactual/qideal
 Flow Coefficient(K):
Where,
K= flow coefficient
Cd=discharge coefficient
β=ratio of diameters
also we can write K=Cd Mva

11. ORIFICE AND DIFFERENTIAL PRESSURE
MANOMETER

12.  Here the pressure difference at orifice us usually
expressed in liquid-column height, then
P1 - P2=(ρm- ρf)h
Where h=liquid column height
ρm = weight density of manometer fluid
ρf = weight density of fluid over manometer
fluid
Finally, we can write the converted equations as,

13. THANK YOU