UNDERSTANDING FLUID FLOW MEASUREMENTS
Fluids can be measured in gravimetric terms (by weight or mass), or in volumetric terms (by volume), or by
velocity. We measure quantity in terms of mass or volume units, such as kilograms or liters. We can also
measure the quantity that has passed through a defined area in each direction over a given period in terms
of mass or volume (kilograms, cubic meters), or in terms of mass flow rate or volume flow rate, such as
kilograms per minute, or cubic meter per hour. To measure the fluid’s mass flow rate or volume flow rate,
we need to use some flow measurement devices, namely mechanical flow meters, variable area meters,
and differential pressure head meters.
WORKING PRINCIPLES IN FLUID FLOW MEASUREMENTS:
1. Bernoulli’s Energy Equation
an increase in the speed of a fluid occurs simultaneously with a decrease in pressure or a decrease in
the fluid's potential energy.
Practical application: pipe flow, venturi meters, orifice plates
2. Continuity Equation
The rate at which mass exits a system is equal to the rate at which mass enters a system in any steady
state process.
3. Projectile Motion
Projectile motion can have an impact on hydraulics through influencing the flow dynamics and fluid
properties inside hydraulic systems. When a bullet enters a fluid flow, it disrupts the flow patterns,
generating changes in velocity, pressure, and turbulence. This disturbance can impair the performance
and efficiency of hydraulic components like pumps, valves, and pipelines. Furthermore, the interaction
of the projectile and the fluid can cause energy loss, erosion, and wear on hydraulic equipment.
4. Principle of Manometer
Hydraulic manometers measure fluid pressure by measuring the heights of fluid columns, giving critical
information for system diagnostics and performance monitoring. They operate on hydrostatic principles
and provide accuracy and versatility across a wide range of hydraulic applications, assuring safe and
efficient system performance.
PIEZOMETER
(etong piezometer, ilagay after ng slides ng manometer)
5. Device Coefficients
- Eto ung sayo Fathima, dito mo iinsert yon lahat ng coefficients
FLUID FLOW MEASUREMENT
Flow Meter is a type of flow instrument that is used to indicate the amount of liquid, gas, or vapor moving
through a pipe or conduit by measuring linear, non-linear, mass, or volumetric flow rates.
As stated, there are three different flow quantities to be measured in a flow meter:
1. The actual velocity of the fluid at a given point (m/s).
2. The volume rate of flow (m/min^3).
3. The mass flow rate (kg/sec).
C. TYPES OF FLOW METERS
DIFFERENTIAL PRESSURE FLOW METER
- Measures the volume flow in gases, liquids and steam using the Bernoulli’s Principle.
- They are particularly used in situations where high pressure, high temperature or a large diameter play
a role.
- They are mainly found in the chemical, oil, gas, and power industries.
EXAMPLE/S OF DP FLOW METERS:
- Orifice Plates
- Venturi Tubes
- Pitot Tubes
- Flow Nozzles
(VIDEO LINK: https://youtu.be/oUd4WxjoHKY?si=bNCccrqbd5EKKyt4 )
ADVANTAGE/S OF DP FLOW DISADVANTAGE/S OF DP FLOW
METERS: METERS:
Versatility Square root relationship between
High accuracy flow rate and differential pressure,
Compatibility with existing therefore smaller span
infrastructure Affected by pressure and density
Reliability changes
VELOCITY FLOW METER
The flow is calculated by measuring the velocity of the fluid in one or more points in the flow and integrating the
flow speed over the flow area. The linear relationship between flow and velocity enables velocity flow meters to
measure flow over a wide range of areas.
TYPES OF VELOCITY FLOW METERS:
1. Vortex - The number of vortices formed indicates the fluid's velocity.
2. Electromagnetic - An electromagnetic flowmeter measures the voltage to calculate the flow rate.
3. Turbine - The frequency of rotations calculates the flow of velocity.
4. Paddle Wheel - sensor picks up on magnets in the paddle as it turns. These produce electrical pulses
that indicate the flow rate.
5. Ultrasonic - Ultrasonic flowmeters use transducers to send sound waves through a fluid.
POSITIVE DISPLACEMENT FLOW METER
Only type of flowmeter that determines the flow rate of a fluid by measuring the volume of fluid that comes
through the meter. The popular use of positive displacement flow meters is due to their accuracy and ability to
measure viscous, dirty, and corrosive media. The one issue with the measurements of positive displacement
flow meters is the pressure drop.
TYPES OF PD FLOW METERS:
1. Rotating or Sliding Vane Meter - The number of revolutions of the rotor is thus a measure of the amount
of fluid that has been passed through the meter.
(VIDEO LINK: https://youtu.be/AFHogF-9eGA?si=n0Z-8Gp4zyl7jfKT )
2. Rotating Impeller Meter - The fluid causes them to rotate, each time they do it causes a volume to be
trapped and move it from inlet to outlet.
(VIDEO LINK: https://youtube.com/shorts/6zE7KN1FiCE?si=CQsv05OyK4Ygs-mV )
TYPES OF PD FLOW METERS:
3. Rotating Piston Meter - The number of rotations of the piston drive shaft is a measure of the volume
that has passed through the meter.
(VIDEO LINK: https://youtu.be/ihTXmNRFJcU?si=m0xmG5zrNIg9sDl8 )
4. Nutating Disk Meter - In this type of meter, an inlet chamber is formed by the housing, a disk, and a
partition between the inlet and outlet ports.
(VIDEO LINK: https://youtu.be/ioId2PV0wZM?si=Xqxi2xdJkpn6A-Kx )
MASS FLOW METER
A mass flow meter measures the mass of a fluid by its inertia as it passes through a vibrating tube equipped
with sensors at the inlet and outlet. The vibration of the tube causes oscillation that is proportional to the mass
of the fluid. The principle of mass flow meters is based on the Coriolis effect that states that anybody moving
on the earth’s surface tends to drift sideways from its course due to the earth’s rotation.
TYPES OF MASS FLOW METERS:
1. Thermal Mass Flow Meters - Uses the principle of thermal dispersion. They have two temperature
sensors with one sensor being the heating element and the other the sensing element.
(VIDEO LINK: https://youtu.be/efhf7BLJ2fc?si=IOvzg0fBXaj751vc )
2. Coriolis Flow Meters - Coriolis flow meters work on the principle of the Coriolis principle. The generated
inertial force is at right angles to the direction of the flow, which is used by a Coriolis flow meter to
measure mass and determine the flow rate.
(VIDEO LINK: https://youtu.be/PvXgaDoZr1E?si=EWmDhUavMvePDZPB )
OPEN CHANNEL FLOW METER
This type of flowmeter includes a dam-like structure known as a primary device. Typically, the primary device is
either a weir or a fume.
