Mass transfer - Citizendia

Mass transfer is the phrase commonly used in engineering for physical processes that involve molecular and convective transport of atoms and molecules within physical systems. In Chemistry, a molecule is defined as a sufficiently stable electrically neutral group of at least two Atoms in a definite arrangement held together by Convection in the most general terms refers to the movement of molecules within Fluids (i History See also Atomic theory, Atomism The concept that matter is composed of discrete units and cannot be divided into arbitrarily tiny In Chemistry, a molecule is defined as a sufficiently stable electrically neutral group of at least two Atoms in a definite arrangement held together by System (from Latin systēma, in turn from Greek systēma is a set of interacting or interdependent Entities, real or abstract Mass transfer includes both fluid flow and separation unit operations. Fluid dynamics is the sub-discipline of Fluid mechanics dealing with fluid flow: Fluids ( Liquids and Gases in motion In Chemical engineering and related fields a unit operation is a basic step in a Process.

Some common examples of mass transfer processes are the evaporation of water from a pond to the atmosphere; the diffusion of chemical impurities in lakes, rivers, and oceans from natural or artificial point sources; mass transfer is also responsible for the separation of components in an apparatus such as a distillation column. Evaporation is the process by which Molecules in a Liquid state (e Water is a common Chemical substance that is essential for the survival of all known forms of Life. Temperature and layers The temperature of the Earth's atmosphere varies with altitude the mathematical relationship between temperature and altitude varies among five Diffusion is the net movement of particles (typically molecules from an area of high concentration to an area of low concentration by uncoordinated random movement A chemical substance is a Material with a definite chemical composition. "Riverine" redirects here For the use of that term in Maritime geography, see there An ocean (from Greek, ''Okeanos'' (Oceanus) is a major body of saline water, and a principal component of the Hydrosphere. A point source is a single identifiable localized source of something Distillation is a method of separating Mixtures based on differences in their volatilities in a boiling liquid mixture In HVAC examples of a heat and mass exchangers are cooling towers and evaporative coolers where evaporation of water cools that portion which remains as a liquid, as well as cooling and humidifying the air passing through. HVAC (pronounced either "H-V-A-C" or occasionally " H-vak " is an Initialism or Acronym that stands for " Heating Cooling towers are heat removal devices used to transfer process waste heat to the Atmosphere. Evaporative coolers (also called swamp, desert, or air coolers) are devices that cool air through the simple Evaporation of water Temperature and layers The temperature of the Earth's atmosphere varies with altitude the mathematical relationship between temperature and altitude varies among five

The driving force for mass transfer is a difference in concentration; the random motion of molecules causes a net transfer of mass from an area of high concentration to an area of low concentration. The amount of mass transfer can be quantified through the calculation and application of mass transfer coefficients. In Engineering, the mass transfer coefficient is a Diffusion Rate constant that relates the Mass transfer rate mass transfer area and concentration Mass transfer finds extensive application in chemical engineering problems, where material balance on components is performed. Chemical engineering is the branch of Engineering that deals with the application of Physical science (e

In astronomy, mass transfer is the process by which matter gravitationally bound to a body, usually a star, fills its Roche lobe and becomes gravitationally bound to a second body, usually a compact object (white dwarf, neutron star or black hole), and is eventually accreted onto it. Astronomy (from the Greek words astron (ἄστρον "star" and nomos (νόμος "law" is the scientific study Matter is commonly defined as being anything that has mass and that takes up space. Gravitation is a natural Phenomenon by which objects with Mass attract one another A star is a massive luminous ball of plasma. The nearest star to Earth is the Sun, which is the source of most of the Energy on Earth The Roche lobe is the region of Space around a Star in a binary system within which orbiting material is gravitationally bound to that star A white dwarf, also called a degenerate dwarf, is a small Star composed mostly of Electron-degenerate matter. A neutron star is a type of remnant that can result from the Gravitational collapse of a massive Star during a Type II, Type Ib or Type A black hole is a theoretical region of space in which the Gravitational field is so powerful that nothing not even Electromagnetic radiation (e It is a common phenomenon in binary systems, and may play an important role in some types of supernovae, and pulsars. A binary star is a Star system consisting of two Stars orbiting around their Center of mass. A supernova (plural supernovae or supernovas) is a stellar Explosion. Pulsars are highly magnetized rotating Neutron stars that emit a beam of Electromagnetic radiation in the form of radio waves

For separation processes, thermodynamics determines the extent of separation, while mass transfer determines the rate at which the separation will occur. In Physics, thermodynamics (from the Greek θερμη therme meaning " Heat " and δυναμις dynamis meaning "

Analogies between heat, mass, and momentum transfer

It is important to note that in molecular transport, heat, or mass there are many similarities. The molecular diffusion equations of Newton for momentum, Fourier for heat, and Fick for mass are very similar. Jean Baptiste Joseph Fourier ( March 21, 1768 &ndash May 16, 1830) was a French Mathematician and Physicist Fick's laws of diffusion describe Diffusion and can be used to solve for the diffusion coefficient D. Therefore many analogies among these three molecular transport process. A great deal of effort has been devoted in the literature to developing analogies among these three transport processes for turbulent transfer so as to allow prediction of one from any of the others. In Fluid dynamics, turbulence or turbulent flow is a fluid regime characterized by chaotic Stochastic property changes Reynolds analogy assumes that the turbulent diffusivities are all equal and that the molecular diffusivities mu/ro and Dab are negligible compared to the turbulent diffusivities. Reynolds analogy relates turbulent momentum and heat transfer When liquids are present and/or drag is present the analogy is not valid. Other analogies, such as von Karman's and Prandtl's, usually results in poor relations. Ludwig Prandtl ( 4 February 1875 &ndash 15 August 1953) was a German Physicist. The most successful and most widely used analogy is the Chilton and Colburn J-factor analogy. Chilton and Colburn J-factor analogy is probably the most successful and widely used Analogy from heat Momentum, and mass transfer analogies This analogy is based on experimental data for gases and liquids in both the laminar and turbulent regions. Laminar flow, sometimes known as streamline flow occurs when a fluid flows in parallel layers with no disruption between the layers Although it is based on experimental data, it can be shown to satisfy the exact solution derived from laminar flow over a flat plate.