4 Transport Phenomena Flashcards
What happen during the diffusion of momentum/viscous motion
The transport occurs in the direction normal to the plates in which there is no motion.
What’s the Stefan flow?
a transport phenomenon concerning the movement of a chemical species by a flowing fluid (typically in the gas phase) that is induced to flow by the production or removal of the species at an interface
Which molecule collision scenarios exist?
- head-on collison
- off-center collision
- limiting off-center collision
What’s the mean free path
The distance a molecule traveled before th next collision occurs
l = travel distance / collision number
Which transport phenomena coefficients are pressure dependent?
- Diffusion coefficient D
- kinematic viscosity v
- thermal diffusivities Alpha
Which transport phenomena coefficients are temperature dependent?
- viscosity coefficient (mü)
- thermal conductivity coefficient lambda
- product of density and diffusion coefficient
What’s thermal diffusivity?
It measures the rate of transfer of heat of a material from the hot end to the cold end.
What’s the thermal conductivity of a material?
A measure of its ability to conduct heat
What does the Schmidt number indicate?
Influence of viscosity to mass diffusion
What does the Prandtl number indicate
Influence of viscosity o thermal diffusion
What does the Lewis number indicate?
Influence of thermal diffusion to mass diffusion
Which second order diffusion effect exist?
- Dufour effect
- Soret effect
What’s the Dufour effect?
When heat diffution occurs in the presence of a concentration gradient
What’s the Soret effect?
When mass diffusion occurs in the presence of a temperature gradient
Which importance do second order diffusion have?
Usually small and negligible
Soret effect is not negligible for H2 and soot
