Molecular transport processes, i. e., diffusion, heat conduction, and viscosity, have in common that the corresponding physical properties are transported by the movement of the molecules in the gas. Diffusion is the mass transport caused by concentration gradients, viscosity is the transport of momentum caused by velocity gradients, and heat conduction is the transport of energy caused by temperature gradients. Additionally, there are other phenomena like mass transport caused by temperature gradients (thermal diffusion or Soret effect) or energy transport caused by concentration gradients (Dufour effect). The influence of the latter is usually very small and is often neglected in the simulation of combustion processes. A detailed discussion of the transport processes can be found in the books of Hirschfelder et al. 1964 or of Bird et al. 1960.
KeywordsThermal Diffusion Rigid Sphere Collision Integral Intermolecular Potential Pressure Diffusion
Unable to display preview. Download preview PDF.