Reviews of Thermal Insulator

Published: 14th November 2011
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A material that does not conduct heat well, i.e., has a relatively low thermal conductivity (see thermal conduction). Plastics, wood, cork, and some fabrics are good thermal insulators. The reason is that they contain weak molecular bonds in disorderly arrangements. Heat is transferred in a material by the vibration of the atoms and molecules. A disorderly arrangement of particles and bonds slows down the passage of heat through the material. Compare with thermal conductor.
Thermal insulation is the method of preventing heat from escaping a container or from entering the container. Thermal insulation can keep an enclosed area such as a building warm, or it can keep the inside of a container cold. Heat is transferred by from one material to another by conduction, convection and/or radiation. Insulators are used to minimize that transfer of heat energy. In home insulation, the R-value is an indication of how well a material insulates. If you have an object or area that is at a certain temperature, you may want to prevent that material from becoming the same temperature as neighboring materials.
Insulation is a barrier that minimizes the transfer of heat energy from one material to another by reducing the conduction, convection and/or radiation effects. Most insulation is used to prevent the conduction of heat. In some cases radiation is a factor. A good insulator is obviously a poor conductor. Less dense materials are better insulators. The denser the material, the closer its atoms are together. That means the transfer of energy of one atom to the next is more effective. Thus, gases insulate better than liquids, which in turn insulate better than solids.
An interesting fact is that poor conductors of electricity are also poor heat conductors. Wood is a much better insulator than copper. The reason is that metals that conduct electricity allow free electrons to roam through the material. This enhances the transfer of energy from one area to another in the metal. Without this ability, the material--like wood--does not conduct heat well.
Conduction occurs when materials—especially solids—are in direct contact with each other. High kinetic energy atoms and molecules bump into their neighbors, increasing the neighbor's energy. This increase in energy can flow through materials and from one material to another.
Solid to solid
To slow down the transfer of heat by conduction from one solid to another, materials that are poor conductors are placed in between the solids. Examples include:
* Fiberglass is not a good conductor nor is air. That is why bundles of loosely packed fiberglass strands are often used as insulation between the outer and inner walls of a house.
* Conductive heat cannot travel though a vacuum. That is why a thermos bottle has an evacuated lining. This type of heat cannot be transferred from one layer to the other through the thermos bottle vacuum.
Convection is transfer of heat when a fluid is in motion. Since air and water do not readily conduct heat, they often transfer heat (or cold) through their motion. A fan-driven furnace is an example of this. Insulation from heat transfer by convection is usually done by either preventing the motion of the fluid or protecting from the convection. Wearing protective clothing on a cold, windy day will inhibit the loss of heat due to convection.
Hot and even warm objects radiate infra-red electromagnetic waves, which can heat up objects at a distance, as well as lose energy themselves. Insulation against heat transfer by radiation is usually done by using reflective materials. A thermos bottle not only has an evacuated lining to prevent heat transfer by conduction, but it also is made of shiny material to prevent radiation heat transfer. Radiation from warm food inside the thermos bottle is reflected back to itself. Radiation from warm outside material is reflected to prevent heating cold liquids inside the bottle.

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