Fluid Dynamics and Flow Principles

Study Notes

Flow

Flow is the quantity of fluid that moves through a pipeline.
Flow can be expressed in terms of velocity, volume, and mass.
Velocity is usually expressed in cubic feet per second.
Volume is usually expressed in gallons and barrels.
Mass is usually expressed in pounds, and is the most accurate method.
Daniel Bernoulli is credited with developing the principles of fluid flow.
Bernoulli's Principle states that as a fluid velocity increases, the pressure within it decreases.
The most common method used in plants to determine flow rates is the orifice plate in conjunction with a delta p transmitter.
The high side of the transmitter is connected upstream of the orifice plate, and the low side is downstream.
Flow always goes from high pressure to lower pressure.
The larger the differential pressure across the orifice plate, the greater the flow rate.
Gas flow rates are expressed in SCF (standard cubic feet).
Fluid flow rates are expressed in GPM, GPH, GPD, BPM, BPH & BPD.
Steam flows (or mass flows) are in Pounds.

Flow Types

Laminar flow is a smooth flow, with no mixing.
Turbulent flow is a chaotic flow, with lots of mixing and eddies.

Common Flow Sensing and Flow Measuring Devices

Orifice - Most common device for creating differential pressure. Installed between orifice flanges. Beveled side facing downstream. Flow is turbulent on the downstream side. Most common type is concentric (hole in the center).
Venturi - Creates pressure drop but minimizes pressure loss. More expensive than an orifice, but it is more accurate. Flow is smooth on the inlet and outlet.
Flow Nozzle - Similar to an orifice on the inlet and similar to the venturi on the outlet. Good for slurry applications.
Pitot tube - Another D/P device. "L" shape that faces the flow (highest pressure is at the center of the pipe. The lower pressure is near the outer wall.
Annubar - Has 4 impact points upstream and downstream and takes an average pressure reading.
Rotameter - Measures small flows. Works on gravity. Must be installed vertically. Flow enters through the bottom and out the top. Uses a tapered tube and a float.
Electromagnetic meter (magmeter) - Measures the electrical capacity of a conductive liquid.
Turbine meter - Measures the RPM of a spinning fan.
Coriolis - Mass flow meter. Has an electromagnetic coil that causes the tubes to vibrate like a tuning fork. Measures the frequency of vibrations, and can also measure the temperature of the flowing fluid. More accurate than volumetric flow meters.
D/P transmitter - The most common. Works according to Bernoulli's principle.
Weir - Underground sewer trunks, basins, lagoons, ponds, and environmental drains flow excess water over a wall (weir) to safe locations during heavy rains.
Flapper/Paddlewheel - Sight glasses that give visible evidence of flow (ex. Lube oil circulation, cooling water jacket, etc.).

Description

This quiz explores the concepts of fluid flow, including velocity, volume, and mass. It covers Bernoulli's Principle and methods for determining flow rates in pipelines. Test your understanding of how pressure differentials affect fluid movement.