2023-09-04 02:34:23
Introduction
A transfer phenomenon (or transport phenomenon) is an irreversible phenomenon during which a physical quantity is transported through molecules. It is a transversal phenomenon present in all fields of science (Science (Latin scientia, “knowledge”) is, according to the dictionary…) and in engineering (Engineering refers to all functions ranging from design and studies to…). All the phenomena of transport (Transport is the fact of carrying something, or someone, from one place to another, the most…) have their origin in the inhomogeneity of an intensive magnitude. It is the spontaneous tendency of physical and chemical systems to make these quantities uniform which causes transport. Thus this type of phenomenon describes certain properties such as:
viscosity: transfer of momentum (In physics, momentum is the physical quantity associated with speed and mass…) due to an inhomogeneity of speed (We distinguish:), diffusion (In everyday language , the term diffusion refers to a notion of molecular…): transfer of the number (The notion of number in linguistics is dealt with in the article “Number…) of particle or mass transfer (In automotive jargon, mass transfer (often confused with charge transfer) is…) due to a density inhomogeneity (The density or relative density of a body is the ratio of its density to the…) particle, the thermal diffusion: thermal transfer (A thermal transfer, more commonly called heat, is a transfer of energy…) (or heat) if the temperature (The temperature is a physical quantity measured using a thermometer and. ..) is not uniform, electrical conductivity: transfer of electrical charge (Electric charge is a fundamental property of matter which respects the principle of…) in the event of a potential difference.
A transfer is characterized by a flux density (The word flux (from the Latin fluxus, flow) generally designates a set of elements…) of the quantity transferred, determined by the following relationship:
where the gradient is the gradient of the quantity transferred. The flux is obtained by multiplying the flux density by the surface (A surface generally designates the superficial layer of an object. The term a…) through which the transfer takes place. The constant is used to include the characteristics of the system in which the transfer takes place (diffusion, radiation) as well as those related to the forces acting on the system (convection).
Diffusion
Diffusion of the quantity (The quantity is a generic term of metrology (count, amount); a scalar,…) of movement
The behavior of Newtonian fluids obeys the following law, known as Newton’s law:
We can show the diffusivity of the momentum ν, or kinematic viscosity (In physics, kinematics is the discipline of mechanics which studies the…), by a modification of Newton’s law:
with
Mass Diffusion
Fick’s Law:
The diffusion coefficient Dab is specific for the species (In the life sciences, the species (from the Latin species, “type”…) a in the medium b.
Thermal diffusion (Thermal is the science that deals with the production of energy, the use of…)
Fourier’s Law:
More commonly called thermal conduction, this equation (In mathematics, an equation is an equality that links different quantities, generally…) can be modified to reveal its thermal diffusivity (Thermal diffusivity is the speed of penetration and attenuation of a thermal wave in…) α:
with
Payload broadcast (The payload represents what is actually…)
Ohm’s Law:
More commonly called electrical conduction, this equation can be modified to reveal its electrical diffusivity, D±, by a modification of Ohm’s law:
with
Other
Similar equations can be defined for the gravitational field:
Gravitational Flux Density:
In the case of a gravitational field, we can speak of graviton transfer and thus associate this phenomenon with a transfer phenomenon (A transfer phenomenon (or transport phenomenon) is a…).
Radiation
Radiation is done using electromagnetic waves (A wave is the propagation of a disturbance producing a variation in its path…) and is therefore reserved for heat transfer. In the latter case, the radiation is mainly dependent on the temperature of the hot body and is no longer influenced by any gradient.
Convection
Convection differs from diffusion by the origin of the transfer. For diffusion, this origin (which is also the driving force) is the gradient. For convection, this origin is an external force. Thus, for example, thermal convection implies a displacement (In geometry, a displacement is a similarity that preserves distances and angles…) of matter (Matter is the substance that makes up any body having a tangible reality. Its.. .) which allows thermal energy (Thermal energy is the kinetic energy of an object, which is due to agitation…) to be transferred. For matter, the convective transfer of a compound is due to a displacement of the medium which contains it.
Natural convection
Natural convection, also called gravitational convection, is due to gravity (Gravitation is one of the four fundamental interactions of physics.) and involves differences in density (the latter can be caused by a difference in temperature or a difference in concentration ) in a homogeneous medium.
Forced convection
The transfer is due to an external force of mechanical origin (In everyday language, mechanics is the field of machines, engines, vehicles, organs…) most often (pump, difference in level,…) and is faster than natural convection.
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