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MEC 322: CONTROL SYSTEM AND INSTRUMENTATION CHAPTER 6 - Coggle Diagram
MEC 322: CONTROL SYSTEM AND INSTRUMENTATION
CHAPTER 6
FLOW MEASUREMENT
SECONDARY
RATE METER
measure another physical quantity
which related to flow
CATEGORIZED INTO
flow rate meter
velocity meters
USED DEVICE
PITOT TUBE
variable head velocity measuring device
Bernoulli's equation
:
P stat/p + V²/2 = P stag/p
V= √2 (P stag/p - P stat/p)
p
V
is the flow velocity
P
is the density of the fluid
P stag
is the stagnation or total pressure of the free stream given by the stagnation tube
P stat
is the free stream static pressure given
by static tube
Advantages
Simple n low cost
No pressure loss in the flow system
Easily inserted to a small hole
Useful in checking the mean velocities
Usually used to detect flow pressure aeroplane
PRIMARY
QUANTITIY METER
Measure the amount of fluid in terms of mass or volume that flows past a given point in a definite period of time
2 METHOD
Volumetric method
Fluid flowing in the flowmeter which is being calibrated is diverted into a tank
Gravimetric method
Fluid flowing in the flowmeter which is being calibrated is diverted into a VESSEL
COMMONLY USED DEVICE
Nutating Disc Meter
it has a movable disk mounted on an concentric sphere located in a spherical side walled chamber
The pressure of the liquid passing through the measuring chamber causes the disk to rock in a circulating path without rotating about it own axis
it is the only moving part in the measuring chamber
a pin extending perpendicularly from the disk is connected to a mechanical counter that monitors the disk's rocking motions
Each cycle is proportional to a specific quantitiy of flow
1 more item...
APPLICATION
Domestic water system
Sliding-Vane-Type Meter
Spring loaded vanes slide in and out of a channel in a rotor so that they make constant contact with the eccentric cylinder wall
When the rotor turns, a known volume of fluid is trapped between the two vanes and the outer wall
The flow rate is based on volume per revolution
The piston type is suitable for accurately measuring small volumes and is not affected by viscocity
Limitations with this device are due to leakage and pressure loss
ADVANTAGES
reaso-
APPLICATION
Dispensing petrol/ diesel in the fuel filling station
Lobed-impeller Meter
APPLICATIONS
metering of gas and
refined petroleum products
Used to lobed impellers, which are geared and meshed to rotate at opposite direction within the enclosure
A known volume of fluid is transferred for each revolution
INTRODUCTION
A technique used in any process requiring the transport of a material from one point to another
TYPES OF FLOW
LAMINAR FLOW
If Re < 2000
TURBULENT FLOW
If Re > 4000
BERNOULLI EQUATION
