Jump to Heat & Mass transfer - Mass Transfer in a system is governed by Fick's First Law: 'Diffusion flux from higher concentration to lower Overview · Commonalities among · Momentum transfer · Energy transfer. The paper deals with the main problems of heat and mass transfer in field and some phenomena of the combined thermal and Soret-driven convection. Parvin Zakeri-Milani and Hadi Valizadeh (February 11th ). Mass Transfer Phenomena and Biological Membranes, Mass Transfer in Multiphase Systems.

Author: | Mrs. Ally Nolan |

Country: | Mexico |

Language: | English |

Genre: | Education |

Published: | 10 January 2015 |

Pages: | 131 |

PDF File Size: | 24.72 Mb |

ePub File Size: | 35.36 Mb |

ISBN: | 738-6-91903-277-1 |

Downloads: | 21275 |

Price: | Free |

Uploader: | Mrs. Ally Nolan |

### Multiphysics Cyclopedia

This rate can be quantified through the calculation and application of mass transfer coefficients for an overall process. Transport phenomena There are notable similarities in the commonly mass transfer phenomena approximate mass transfer phenomena equations for momentum, heat, and mass transfer.

At higher Reynolds number, the analogy between mass and heat transfer and momentum transfer becomes less useful due to the nonlinearity of the Navier-Stokes equation or more fundamentally, the general momentum conservation equationbut the analogy between heat and mass transfer remains good.

The solution of the Navier-Stokes equations gives the velocity field a vector field that also determines the mass transfer phenomena of the convective flux of all species in the mixture.

The tight coupling between mass transport for each species and the conservation of mass for the whole mixture is exemplified in the example below.

## What Is Mass Transfer?

Oxygen in air is consumed at the surface of a catalyst and produces liquid water that is removed from the gas phase in a gas diffusion electrode.

The consumption of oxygen causes a net velocity in the gas mixture air. Additionally, a nitrogen concentration gradient is formed in order to perfectly mass transfer phenomena the advective or convective flux of nitrogen with an opposite flux by diffusion. Surface plot of the nitrogen concentration in mass transfer phenomena gas diffusion electrode.

mass transfer phenomena The flux along the right vertical edge, plotted in the x-y plot, shows that the diffusive flux from the catalytic surface exactly compensates the convective flux to this surface, generated by oxygen consumption at the catalyst's surface.

Due to the difficulties of numerically resolving steep gradients mass transfer phenomena potential, mass transfer across phase boundaries is often expressed using difference equations, instead of differential equations. This approximation implies that the gradients, included in the driving forces, are linearized inside a fictitious boundary layer see the figure below.

### Mass Transfer Phenomena and Biological Membranes

The thickness of the layer is then defined as the distance from a phase boundary where the linearized concentration gradient, starting from the concentration at the phase boundary, reaches the bulk concentration.

The definition of the boundary layer also means that its thickness may be mass transfer phenomena for different species. Fictive boundary layers inside and around a gas bubble in a liquid.

However, if the mass transport around mass transfer phenomena gas bubble in a liquid is studied, then L may denote the radius of the bubble.

## Transport phenomena - Wikipedia

Since the thickness of the boundary layer depends on the convection just outside an interface, the Sherwood number also gives a measurement of the convective and diffusive fluxes to such an interface.

The Sherwood number can also be defined as a function of the Reynolds and Schmidt numbers. The Reynolds number gives an estimate of the ratio of momentum transport by inertia to viscosity in mass transfer phenomena fluid: For example, in solid state physicsthe motion and interaction of electrons, holes and phonons are studied under "transport phenomena".

Another example is in biomedical engineeringwhere some transport phenomena of interest are thermoregulationperfusionand microfluidics. In chemical engineeringtransport phenomena are studied in reactor designanalysis of molecular or mass transfer phenomena transport mechanisms, and metallurgy.

The transport of mass, energy, and momentum can be affected mass transfer phenomena the presence of external sources: An odor dissipates more slowly and may intensify when the source of the odor remains present.

## Transport Phenomena

A good analogy is the flow of traffic on a busy freeway. The far right lane on the freeway typically move slower than the far left lane, with the lanes in the middle going faster the further left you move.

This can be compared to flow over a flat plate, where the slower flow the right lane on the freeway is right next to the plate, and the faster flow the left mass transfer phenomena on the freeway on the surface of the fluid.

The transfer of momentum is like the cars changing lanes, as slower cars pull mass transfer phenomena faster lanes the lanes slow down to allow the car to accelerate and not cause a pile-up on the freewayand the faster mass transfer phenomena pulling into slower lanes and speeding up the lane a little bit.

In Heat Transfer, energy moves from a place where there is a lot to a place where there is less. For example, if you heat up a brick, then drop it into cold water, the brick gets colder and the water gets mass transfer phenomena.

Once the brick and the water are at the same temperature, no more energy can be transferred.

Back to the red dye example: Mass transfer phenomena, as the dye spreads out, the concentration of the dye slowly increases, until, it is all at the same low concentration everywhere.