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 rate of heat transfer are also useful where they can act as a heat shield in applications that generate large amounts of heat, such as airplane engines.
Here’s a ranking of heat conducting metals and metal alloys from lowest to highest average thermal conductivity, in Watts/meter-K at room temperature:
- 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, say, copper. This means that a pot made of stainless would take much longer to heat up 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 high temperatures longer, keeping buildings cooler in sunlight.
While 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. Heat generated by the electronics transfers from the chip to the aluminum and then to the air, either passively or with the help of forced airflow convection or a thermoelectric cooler.
Copper has a very high thermal conductivity and is much cheaper and more available than silver, which is the best metal of all for conducting heat. Copper is corrosion resistant and resists biofouling, which makes it a good material for solar water heaters, gas water heaters, and industrial heat exchangers, refrigerators, air conditioners, and heat pumps.
Other factors affecting heat conduction
When considering the best metals for heat conduction, you must also take into account other factors in addition to thermal conductivity, which affect the rate of heat flow. For example, the initial temperature of the metal can make a huge 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 of the metal, and the surface area of the metal.
For the largest selection of metals in the Southwest, contact Industrial Metal Supply.
Data taken from Engineering Toolbox.