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Thermal conductivity is the term that describes how quickly a material absorbs heat from areas of high temperature and moves it toward areas of lower temperature. The best heat-conducting metals have high thermal conductivity and are useful for many applications, such as cookware, heat exchangers, and heat sinks. On the other hand, metals with a lower heat transfer rate are also useful where they can act as a heat shield in applications that generate large amounts of heat, such as airplane engines.
Thermally Conductive Metal Options
Ranked from lowest to highest average thermal conductivity in Watts/meter-K at room temperature, the following metals are generally used as either a heat source block or for heat transfer, depending on their ranking. The least conductive metals are ranked first, all the way to the most conductive materials.
- Stainless Steel (16)
- Lead (35)
- Carbon steel (51)
- Wrought iron (59)
- Iron (73)
- Aluminum Bronze (76)
- Copper brass (111)
- Aluminum (237)
- Copper (401)
- Silver (429)
With one of the lowest thermal conductivities for a metal alloy, stainless takes much longer to conduct heat away from a source than copper. This means a pot made of stainless would take much longer to heat food than a copper-bottom pot (though stainless has other benefits). Steam and gas turbines in power plants use stainless steel because of its heat resistance, among other properties. In architecture, stainless steel cladding can resist higher temperatures, keeping buildings cooler in sunlight.
AluminumWhile aluminum has a slightly lower thermal conductivity than copper, it is lighter in weight, cheaper, and easier to work with, making it a better choice for many applications. For example, microelectronics such as LEDs and laser diodes use tiny heat sinks with aluminum fins that project into the air. Within aluminum, heat-generated electronics transfer from the chip through the aluminum to the air, either passively or with the help of forced airflow convection or a thermoelectric cooler.
CopperCopper has a very high thermal conductivity and is much cheaper and more available than silver, which is the best metal for conducting heat. Copper is corrosion resistant and resists biofouling, making it a good material for solar water heaters, gas water heaters, industrial heat exchangers, refrigerators, air conditioners, and heat pumps.
Other Factors Affecting Heat ConductionWhen considering the best metals for heat conduction, you must also consider other factors in addition to thermal conductivity, which affects the rate of heat flow. For example, the initial temperature of the metal can make a massive difference to its heat transfer rate. At room temperature, iron has a thermal conductivity of 73, but at 1832°F, its conductivity drops to 35. Other influences include the temperature difference across the metal, the thickness, and the metal's surface area.
Applications for Conductive MetalsThermally conductive metals are an essential resource for designing the structure of an application. Electronics and custom-designed mechanical components rely on conductive metals to produce a fully operative design that either draws or deflects thermal activity. Conductive metal applications include:
- Medical devices
- Laboratory equipment
- Construction gear
- Electrical wiring
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