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If there is a change in the potential energy of a system; for example μ 1 >μ 2 (μ is Chemical potential) an energy flow will occur from S 1 to S 2, because nature always prefers low energy and maximum entropy. Molecular diffusion is typically described mathematically using Fick's laws of diffusion.
mass transfer (advection–diffusion problems; total momentum transfer to diffusive mass transfer) Prandtl number: Pr = = heat transfer (ratio of viscous diffusion rate over thermal diffusion rate) Pressure coefficient: C P
Under an idealized reaction condition for A + B → product in a diluted solution, Smoluchovski suggested that the molecular flux at the infinite time limit can be calculated from Fick's laws of diffusion yielding a fixed/stable concentration gradient from the target molecule, e.g. B is the target molecule holding fixed relatively, and A is the ...
The higher the diffusivity (of one substance with respect to another), the faster they diffuse into each other. Typically, a compound's diffusion coefficient is ~10,000× as great in air as in water. Carbon dioxide in air has a diffusion coefficient of 16 mm 2 /s, and in water its diffusion coefficient is 0.0016 mm 2 /s. [1] [2]
Graham's law states that the rate of diffusion or of effusion of a gas is inversely proportional to the square root of its molecular weight. Thus, if the molecular weight of one gas is four times that of another, it would diffuse through a porous plug or escape through a small pinhole in a vessel at half the rate of the other (heavier gases ...
Diffusivity is a rate of diffusion, a measure of the rate at which particles or heat or fluids can spread. It is measured differently for different mediums. Diffusivity may refer to: Thermal diffusivity, diffusivity of heat; Diffusivity of mass: Mass diffusivity, molecular diffusivity (often called "diffusion coefficient")
In gases, molecular diffusion is dependent on pressure and temperature. The higher the pressure, the slower the diffusion takes place, and the higher the temperature, the faster the diffusion takes place. In liquids, an increase in temperature increases the rate of diffusion. However, since liquids are incompressible, the rate of diffusion is ...
In engineering, the mass transfer coefficient is a diffusion rate constant that relates the mass transfer rate, mass transfer area, and concentration change as driving force: [1] = ˙ Where: is the mass transfer coefficient [mol/(s·m 2)/(mol/m 3)], or m/s