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Questions and Answers
What characterizes laminar flow?
What characterizes laminar flow?
What is the primary driving principle behind the movement of fluids?
What is the primary driving principle behind the movement of fluids?
What commonly causes turbulent flow in a piping system?
What commonly causes turbulent flow in a piping system?
What is flow rate defined by?
What is flow rate defined by?
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What does the Reynolds number primarily help determine in fluid flow?
What does the Reynolds number primarily help determine in fluid flow?
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Which factor contributes to an increase in Reynolds number?
Which factor contributes to an increase in Reynolds number?
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Which statement is true about turbulent flow?
Which statement is true about turbulent flow?
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Which condition is least likely to cause laminar flow?
Which condition is least likely to cause laminar flow?
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What type of flow measurement devices are flappers and paddlewheels classified as?
What type of flow measurement devices are flappers and paddlewheels classified as?
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What do positive displacement flow meters measure?
What do positive displacement flow meters measure?
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How is flow often used in relation to flow rate?
How is flow often used in relation to flow rate?
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In flow measurement, what does 100 percent flow rate typically equate to?
In flow measurement, what does 100 percent flow rate typically equate to?
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Which of the following is a primary benefit of turbulent flow?
Which of the following is a primary benefit of turbulent flow?
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What is measured in volumetric flow units?
What is measured in volumetric flow units?
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What is a potential negative effect of turbulent flow?
What is a potential negative effect of turbulent flow?
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Which factor may influence the type of flow experienced in a piping system?
Which factor may influence the type of flow experienced in a piping system?
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What type of primary flow element is an orifice plate?
What type of primary flow element is an orifice plate?
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What happens to the Reynolds number when absolute viscosity increases?
What happens to the Reynolds number when absolute viscosity increases?
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Which type of flow measurement can be expressed in pounds per unit of time?
Which type of flow measurement can be expressed in pounds per unit of time?
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Which of the following is NOT a type of positive displacement meter?
Which of the following is NOT a type of positive displacement meter?
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What is the primary function of metering holes in a flowing process?
What is the primary function of metering holes in a flowing process?
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Which type of flow meter does not have a recovery cone and can be inserted directly into a pipe?
Which type of flow meter does not have a recovery cone and can be inserted directly into a pipe?
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What is the primary measurement principle of Magmeters?
What is the primary measurement principle of Magmeters?
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What disadvantage is associated with standard Pitot Tubes?
What disadvantage is associated with standard Pitot Tubes?
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What type of flow meter is most common for measuring mass flow and is not affected by changes in fluid properties?
What type of flow meter is most common for measuring mass flow and is not affected by changes in fluid properties?
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Which device responds to the pressure created by the primary flow measuring device and produces a corresponding output signal?
Which device responds to the pressure created by the primary flow measuring device and produces a corresponding output signal?
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Which flow measuring device is known for allowing solids to pass freely due to its design with sloped inlets?
Which flow measuring device is known for allowing solids to pass freely due to its design with sloped inlets?
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How do Venturi Tubes compare to orifice plates regarding permanent pressure loss?
How do Venturi Tubes compare to orifice plates regarding permanent pressure loss?
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What is the function of the small weep hole drilled next to a metering hole?
What is the function of the small weep hole drilled next to a metering hole?
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Which aspect does NOT affect the calibration of turbine meters?
Which aspect does NOT affect the calibration of turbine meters?
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What is the primary measurement method used by a vortex flow meter?
What is the primary measurement method used by a vortex flow meter?
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Which type of flow meter is designed to avoid mechanical movement?
Which type of flow meter is designed to avoid mechanical movement?
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What is the correct definition of total flow in the context of fluid measurement?
What is the correct definition of total flow in the context of fluid measurement?
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In which of the following scenarios would an orifice flow meter likely be unsuitable?
In which of the following scenarios would an orifice flow meter likely be unsuitable?
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What happens to the Reynolds number if the absolute viscosity of a fluid increases?
What happens to the Reynolds number if the absolute viscosity of a fluid increases?
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When measuring flow rate, which unit would be used for volumetric flow?
When measuring flow rate, which unit would be used for volumetric flow?
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What is the primary function of a Pitot tube in fluid measurement?
What is the primary function of a Pitot tube in fluid measurement?
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Which type of orifice plate is defined by a half-moon shape?
Which type of orifice plate is defined by a half-moon shape?
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For an orifice where the flow doubles, how does the differential pressure respond?
For an orifice where the flow doubles, how does the differential pressure respond?
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What is the primary method that a mass flow meter uses to measure fluid flow?
What is the primary method that a mass flow meter uses to measure fluid flow?
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Study Notes
Introduction to Flow
- Flow is a fluid in motion.
- Fluids move from high to low pressure.
- Flow rate is the amount of fluid moving through a pipe or channel in a given time.
- Laminar flow is smooth and consistent.
- Turbulent flow is caused by obstructions and promotes mixing.
- Reynolds number predicts whether flow is laminar or turbulent.
- Factors influencing Reynolds number: fluid velocity, density, viscosity, pipe inside diameter.
- Direct flow measurements measure flow directly.
- Indirect flow measurements infer flow from other variables.
- Flow can be measured in absolute quantities, percentages, or volumes.
Positive Displacement Flow Measurement
- Used for accurate volume measurements.
- Devices admit fluid into a chamber, measure volume, and transfer it to another point.
- Common types include piston, oval gear, nutating disk, and rotary vane.
Percentage Flow Rate
- Indicates a flowing process.
- 100 percent represents a specific quantity, such as GPM or liters per minute.
- Flow rates are expressed as percentages of this quantity.
Volumetric Flow Units
- Measure instantaneous flow rate by volume per time unit.
- Measured in GPM (gallons per minute) or CFM (cubic feet per minute).
Mass Flow Units
- Measure instantaneous mass flow per time unit.
- Expressed in pounds per time unit.
- Considers mass density, which is influenced by temperature.
Types of Flow Measurement Devices
- Most common flow elements measure differential pressure, which is related to flow rate.
- Primary flow sensing devices include:
Orifice Plates
- Thin metal plates with precise holes (metering holes).
- Create a pressure drop in the flow.
- Types: concentric, eccentric, segmental.
- Allow solids to pass.
- Mounted in orifice flanges.
- Changes in flow rate cause changes in differential pressure.
Venturi Tubes
- Create a pressure drop using a tapered design.
- Less permanent pressure loss than orifice plates.
- Pressure is reduced as the fluid speeds up in the narrower throat section.
Flow Nozzles
- Similar to venturi tubes, but with a smaller throat and no recovery cone.
- Inserted at flange connections or in spool pieces.
- Allow more flow per unit pressure drop than orifice plates.
- Suitable for slurries due to sloped inlets.
Pitot Tubes
- L-shaped tubes inserted into the pipe, measuring velocity at one point.
- One end faces the flow, the other measures static pressure.
- Provide accurate average velocity with high Reynolds numbers.
Multiport Pitot Tubes
- Multiple impact points across the pipe to measure velocity.
- One tube measures static pressure.
- Averages multiple readings for a single measurement.
Rotameters
- Variable area flow tubes.
- Fluids flow upward, lifting a free-floating indicator plummet.
- Float position indicates flow rate.
Magmeters
- Measure volumetric flow of electrically conductive liquids, slurries, and corrosive materials.
- No obstruction of flow path, non-invasive.
- Based on Faraday’s law – electrical potential is generated when a conductor moves through a magnetic field.
- Electrodes detect the potential.
Turbine Meters
- Contain a free-spinning turbine wheel.
- Revolutions per unit time are proportional to flow rate.
- A magnetic blade creates pulses as the turbine rotates.
- Requires calibration to establish a K factor (pulses per unit volume) considering viscosity and specific gravity.
Mass Flow Meters
- Most common: Coriolis meters
- Measurements are independent of temperature, pressure, density, and viscosity.
- A vibrating tube with velocity sensors measure the frequency change to determine mass flow.
Differential Pressure (D/P) Transmitters
- Convert pressure generated by primary elements into a standard output signal.
- Output signals can represent differential pressure or flow rate.
- Cell responds to pressure measurements.
- Flow rate changes are squared in the pressure drop.
Miscellaneous Flow Meters
- Vortex flow meters measure fluids but do not handle high viscosity or low flow applications.
- Target flow meters use a disc to measure force proportional to pressure head.
- Integral orifice flow meters measure small flows and are permanently installed in a meter run.
- Ultrasonic flow meters measure velocity by timing an ultrasound beam travel time.
- Can be inline (intrusive) or clamp-on (non-intrusive), measure temperature differences, and particulate content.
Flow Rate, Total Volume Flow, and Volumetric Flow
- Two types of flow measurement:
- Flow rate: instantaneous measurement.
- Total flow: summation of instantaneous flow rates over a time interval or accumulated counts from positive displacement devices.
- Measured in volume or mass units per time interval.
- Units
- Volumetric flow: GPM (gallons per minute), L/min (liters per minute).
- Mass flow: lbs/min (pounds per minute), kg/min (kilograms per minute).
- Total flow: gallons, pounds, cubic feet, liters, kilograms, cubic meters over specified time.
Check Your Knowledge
- To determine Reynolds number you need: pipe inside diameter, fluid viscosity, fluid density, and fluid velocity.
- Increase in absolute viscosity makes Reynolds number smaller.
- Differential flow rates require consideration of flowing fluid temperature.
- Segmental orifice plates are half-moon shaped.
- A rotameter uses a free-floating indicator plummet.
- A Pitot tube measures flow using an L-shaped tube with a static pressure tube.
- An orifice plate measures flow using a metal disc with a drilled hole.
- A flow nozzle measures flow with a tapered inlet device inserted into a flange connection.
- A venturi tube measures flow using a cone-shaped device.
- The % flow rate for a D/P of 28% is 52.9%.
- A turbine meter measures flow using a spinning fan.
- A magmeter measures flow by sensing electric potential.
- A mass flow meter uses a U-tube vibration frequency for flow measurement.
- A D/P transmitter responds to signals from primary devices.
- If flow through an orifice doubles, the differential pressure quadruples.
- Special flanges for mounting orifice plates are called orifice flanges.
- Units associated with mass flow are lbs/min.
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Image Matching
- Venturi: Cone shaped tube with inlet and outlet.
- Flow Nozzle: Tapered inlet device inserted into a flange.
- Multiport Pitot Tube: Tube with multiple sensors measuring velocity.
- Orifice Plate: Thin plate with a hole.
- Pitot Tube: L-shaped tube measuring velocity at one point.
- Mass flow meter: Uses vibration for flow measurement.
- Rotameter: Variable area flow tube with a floating plummet.
- Electromagnetic flow meter (magmeter): Uses magnetic field and electrodes to measure flow.
- Turbine meter: Contains a turbine wheel.
- D/P transmitter: Transmits signals based on pressure measurements.
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Description
This quiz covers the fundamental concepts of fluid flow, including definitions of laminar and turbulent flow, Reynolds number, and flow measurement techniques. It also explores positive displacement flow measurement and percentage flow rates for accurate assessments. Test your understanding of these essential fluid mechanics principles!
