transportcoëfficiënt

A transport coefficient is a proportionality constant that relates a flux of some quantity to a gradient of a driving potential for that flux. In essence, it quantifies how efficiently a quantity is transported through a system under the influence of a gradient. These coefficients are fundamental in many areas of physics and chemistry, particularly in describing transport phenomena such as diffusion, viscosity, thermal conductivity, and electrical conductivity.

For example, Fick's first law of diffusion states that the flux of particles is proportional to the negative of the concentration gradient. The constant of proportionality is the diffusion coefficient, a classic example of a transport coefficient. Similarly, Fourier's law of heat conduction relates the heat flux to the temperature gradient, with thermal conductivity as the transport coefficient. In fluid dynamics, Newton's law of viscosity relates the shear stress to the velocity gradient, where the dynamic viscosity acts as the transport coefficient. Electrical conductivity describes the relationship between electric current density and the electric field gradient.

Transport coefficients are generally dependent on the material's properties, temperature, pressure, and other environmental conditions. They can be determined experimentally or calculated from theoretical models. Understanding transport coefficients is crucial for modeling and predicting the behavior of various physical systems, from the microscopic movement of atoms and molecules to macroscopic phenomena like heat and mass transfer in engineering applications.