The transfer of energy from one atom to another through physical contact is generally termed as conduction. Conduction based power supplies remove the need to depend upon fans for cooling. These devices utilise external metal structures, which act as a large heat sink surface for dissipation of internal energy. In some power supplies, liquid cooled plates are made up of serpentine channels through which liquid circulates for removing the unwanted heat. The conduction process is generally classified into three categories: Ionic Conduction, Electric Conduction and Heat Conduction.
As represented in the name, this type of conduction is due to the movement of ions from one place to another. This phenomenon happens due to the deficiencies in the lattice structure of solids. These defects permit the ions to progress in an electric field because of the vacancy. Specific solid materials have very high ionic conductivity which proved to be very effective in solid-state electronics like computers, mobile phones and power supplies. They are very useful in fuel cells as well as in both normal and rechargeable batteries. Ionic salts can also be dissolved in solution which then permits the electric current to flow.
In metals, electrical conduction occurs due to the movement of electrically charged particles. All the metals contain valence electrons in the outermost shell of each atom. These elements are free to move throughout the structure and responsible for the conduction of electrical current. The electric potential applied across the metal causes the net drift of electrons around the circuit, this flow of electrons is directly proportional to the applied electric potential. There is only one of the 12-coordinated metal in which each atom in the structure touches 12 other atoms. Secondly, 8-coordinate metal is often found in group 1 of the periodic table. In these metals, atoms are bound less tightly as each atom only connects to 8 other atoms. Lastly, some semiconductors serve as a conductor as well as an insulator like silicon and carbon. As compared to metal they are poor conductors of electricity but their conductivity is enhanced with the 'doping' process. in this process some impurities are added to the semiconductor. The doped semiconductor is then called an extrinsic semiconductor which conducts electricity more effectively compared to the usual semiconductors.
Thermal or heat conduction is defined as the rapid collision of neighboring particles, the collision of particles caused the transferring of kinetic energy. This process occurs with the temperature difference between the two bodies. The rate of heat conduction depends upon four things.
- The amount of temperature difference between two consecutive bodies
- The cross-sectional area of the region
- Length of the region
- The material in which the process is taking place
Metallic solids are known as the best heat conductors while gases are the worst. Because in solids, the particles are very close to each other and rapid collision causes very effective transferring of thermal and electrical energy. That's why a higher density of solid permits better conduction of thermal energy.
In a nutshell, conduction is all about the transfer of energy from a warmer substance to a colder substance through physical or direct contact. One important thing that needs to remembered is that energy is transfers from one particle to another but there is no overall movement of particles in the entire process. Conduction cooling is the most efficient way of increasing realibilty and durability of power supplies. Heat sensitive components can be cooled at source and thermally managed individually as required. These heat sensitive components can even be submerged somewhat into the metalwork. By using metalwork as part of the mechanics, typically a heatsink or cold wall is used to “conduct” the heat away. Conduction cooled PSU’s are often more robust due to the nature with which they are mechanically connected. They also negate the need for cooling fans which may be the noisiest and weakest mechanical point of the device.
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