What are heat conductors?
The heat conductors They are those materials whose structure is such that heat can pass through them very easily. It must be remembered that matter is made up of atoms and molecules in constant vibratory motion, and that heat translates into a greater agitation of said particles.
Some materials conduct heat better than others, because its internal configuration facilitates this flow of energy. Wood, for example, is not a good conductor of heat because it takes a long time to heat up. On the other hand, iron, copper and other metals are, which means that their particles acquire kinetic energy very quickly.
That is why metals are the best for making kitchen utensils, such as pots and pans. They heat up quickly and reach temperatures high enough for food to cook properly.
However, handles and handles, which are in contact with the user’s hands, are made of other heat-insulating materials. In this way the pans are easily handled even when hot.
Driver types
Depending on their way of conducting heat, materials are classified as:
thermal conductors: diamond and metals such as copper, iron, zinc and aluminum, among others. Usually, good conductors of electricity are also good conductors of heat.
Thermal insulation: wood, rubber, fiberglass, plastic, paper, wool, anime, cork, polymers are good examples. Gases are also not good conductors.
Thermal conductivity of materials
The property that characterizes the way in which each of them conducts heat is called Thermal conductivity. The higher the thermal conductivity of a substance, the better it conducts heat.
The thermal conductivity of substances is determined experimentally. In the SI International System of Units, thermal conductivity is measured in Watt/(meter x kelvin) or W/(mK). It is interpreted as follows:
1 W/(mK) is equivalent to 1 watt of power, transmitted through a length equal to 1 meter, when the temperature difference between the two extremes is 1 kelvin.
Another unit for thermal conductivity used in Anglo-Saxon countries is BTUH/ (ft.ºF), where the initials BTUH correspond to British Thermal Unit per hour.
Thermal conductivity values
Next, the thermal conductivities of some elements and materials found in nature and that are frequently used in industry.
However, it must be noted that there are synthetic compounds, even in the experimental phase, whose thermal conductivity far exceeds that of diamond, which heads the table.
The temperature is decisive in the value of the thermal conductivity of metals. As the temperature increases, so does the thermal conductivity (although the electrical one decreases). For nonmetals, the thermal conductivity is approximately constant over a wide range of temperatures.
The values in the table are specified at 25 °C and 1 atmosphere of pressure.
When selecting a material for its thermal properties, one must take into account that it expands with heat. This ability is given by the Coefficient of thermal expansion.
Examples of heat conductors
Diamond
It is the best thermal conductor at room temperature, much better than copper and any other metal. In diamond, which is an electrical insulator, heat does not flow through conduction electrons, but through the propagation of vibrations in its highly organized crystalline structure. These vibrations are called phonons.
Silver
It is a highly valued metal for ornamentation due to its shine, color and malleability. It is resistant to oxidation and among all metals it is the one with the highest thermal conductivity, as well as excellent electrical conductivity.
For this reason, it has multiple applications in industry, both alone and in alloys with other elements such as nickel and palladium.
Copper
It is one of the most used metals when good thermal conductivity is required, because it does not corrode easily and its melting point is quite high, which means that it will not melt easily when exposed to heat.
Other advantages it has is its ductility, as well as not being magnetic. Copper is recyclable and is much less expensive than silver. However, its coefficient of thermal expansion is high, so its dimensions change appreciably when heated.
Gold
It is the precious metal par excellence and occupies a preponderant place in the history of humanity. Apart from this special meaning, gold is malleable, resistant and a magnificent conductor of heat and electricity.
Since gold does not corrode, it is used to carry small currents in solid-state electronic components. These currents are so small that they can be easily interrupted at the slightest hint of corrosion, which is why gold guarantees reliable electronic components.
Lithium
It is the lightest of all metals, although very reactive, so it corrodes easily. You also have to handle it with great caution, because it is highly flammable. Due to this, although it is abundant, it is not found in a free state but in compounds, for which reason it must generally be isolated by electrolytic methods.
Its thermal conductivity is similar to that of gold, but it is much cheaper than gold. Lithium carbonate is a compound used in the manufacture of heat-resistant glass and ceramics.
Aluminum
This lightweight, inexpensive, highly resistant and easy to work metal is one of the main materials used to manufacture heat exchangers in HVAC equipment such as air conditioners and heaters.
Bronze
Bronze is an alloy of copper and tin, mainly, with other metals to a lesser extent. It has been present since remote times in the history of humanity.
It is so important that a period of Prehistory has even been named the Bronze Age, the time when people discovered and began to use the properties of this alloy.
Zinc
It is a very malleable and ductile bluish-white metal, easy to work, although with a low melting point. It has been known since Antiquity, and is mainly used in alloys.
Currently, it is used to galvanize steel and protect it from corrosion. Also to manufacture batteries, pigments and manufacture special zinc sheets for the construction industry.
Iron
Iron is another metal with great historical significance. Like bronze, iron is linked to a period of Prehistory in which great technological advances were made: the Iron Age.
At present, cast iron continues to have many applications to make tools, utensils, in construction and as a material for the manufacture of automotive parts.
References
Thermal Conductors and Insulators. Retrieved from ck12.org.
Hill, D. Thermal Properties of Cast Iron. Recovered from ehow.com.