Question

What does a high permeability coefficient mean?

Answer 1

The coefficient of permeability of an incompressible fluid is defined as the rate of flow of fluid molecules through a unit cube of porous substance (Cell wall, soil) when a unit pressure difference is applied across it.
For material with a high permeability coefficient, fluids can easily pass through such material.
For permeability of the soil, Darcy’s law plays a crucial role in determining the result of the permeability test.
Permeability coefficient is very important in many fields of engineering and biology as well.

Complete step by step solution:
As given above, the coefficient of permeability is the rate at which fluid can flow through a porous membrane (lipid bilayer) under unit pressure and volume.
Thus, for a high coefficient permeability, the rate of flow of fluid will be high.
And the formula for permeability coefficient is given as
$k = \dfrac{{qL}}{{Ah}}$
From this, we can see that the S.I unit of coefficient of permeability is $cm/s$.
Here,
$k =$ coefficient of permeability.
$q =$ Rate of discharge fluid ($c{m^3}/{\text{ }}sec$).
$L =$ length of the membrane in cm.
$A =$ cross-section area of membrane ($c{m^2}$).
$h =$ constant heat causing flow in $\;cm$.

Additional information:
The coefficient of permeability is extremely useful for agriculture and civil engineering.
For example, it can be used to calculate how easily any fluid or water can move through soil concrete or any other porous material.
It is also known as the hydraulic conductivity of a material.

Note: Diffusion coefficient (D) is defined as the amount of a substance that is diffused across a unit area and it is inversely proportional to the permeability coefficient.
i.e., $D \propto \dfrac{1}{k}$
A lipid bilayer is a thin polar membrane consisting of a double layer of lipid molecules that form a barrier around the cell.
The coefficient of permeability is also affected by certain factors such as viscosity, the density of the fluid, void size, surface roughness, etc.