Flow Measurement

Table of Contents

Flow measurement is the oldest of all measurement process variables in the field of instrumentation. It is designed to determine the proportion and quantity of material flowing in or out of a process. For the purpose of cost accounting, such measurements are often required for steam, water and gas services. Without flow measurement, plant material balancing, quality control and even the operation of any continuous process would be nearly impossible.

There are three types of flow

Laminar (Viscous) Flow
Turbulent Flow
Transitional Flow

Laminar (Viscous) Flow:

Let a liquid flow slowly and steadily over a fixed horizontal surface, such that a layer of liquid moves parallel to it, with their velocity increasing uniformly from one layer to the next. The velocity is maximum at the free surface of the liquid. This type of fluid flow in which its layers slide over each other without mixing is called laminar flow.

Turbulent flow:

If the liquid is pushed into the tube too fast, the flow may become turbulent. In matter, the velocities of different particles pass though the same point may vary and change erratically with time. The water speed in the high falls is a fast flowing river which is generally turbulent.

Transitional Flow:

Transitional flow is a blend of laminar and turbulent flow, with laminar flow towards the pipe’s borders and turbulent flow in the centre. Each of these flows exhibits distinct behaviours in terms of the frictional energy lost during flow, and several equations are used to forecast these behaviours.