Using Porosity to Measure Fibre Diameter

This paper is Part 12 in a series titled Fundamental Principles of Fibre Diameter Measurement.

Abstract

The theory underlying the physics of the flow of air through porous beds of fibres is founded on the work of a French Mathematician in 1840.  Poiseuille’s Law describes the relationships governing the flow of fluids though capillaries.

This theory, together with later enhancements by Darcy and then Kozeny are the basis of the operation of the Airflow Instrument.  From 1960 to 2000 the Airflow instrument was  the de facto standard for commercial trading of greasy wool, scoured wool and top, and despite the the advent of improved technologies that also provide distribution data, it is still used extensively in mill laboratories around the world.

This paper provides a detailed review of:

• the theory of operation;
• the development of the instrument; and
• its technical limitations.

Citation

"Fundamental Principles of Fibre Diameter Measurement. Part 12: Porosity", P.J. Sommerville, AWTA Ltd Newsletter, March 2004