Transport Phenomena - short answer questions from AMIE exams (Summer 2018)
What are the factors on which diffusivity depends?
- The rate of diffusion is affected by the concentration gradient, membrane permeability, temperature, and pressure.
- Diffusion takes place as long as there is a difference between the concentrations of a substance across a barrier. However, diffusion stops, when the concentrations of the substance on either side of the barrier become equal.
- The permeability of a membrane affects the rate of diffusion. Diffusion rate increases as membrane permeability increases.
- Changes in temperature and pressure values also affect the diffusion of substances. Pressure plays an important role in the diffusion of gases as gases diffuse from a region of higher partial pressure to a region of lower partial pressure.
Flow past immersed bodies
The physical significance of Prandtl and Schmidt numbers
Differentiate between turbulence and wall turbulence.
The analogy between momentum and heat transfer
Reynolds's analogy gives the interrelationship between fluid friction and newton’s law of viscosity.
The Reynolds analogy is given by,
Nu/RePr = St = Cf/2
Nu = Local Nusselt number, Re = Local Reynolds number, St = Local Stanton number, Pr = Prandtl number, Cf = Skin friction coefficient