Which Metals Conduct Heat Best?

In a world driven by technology and innovation, the role of metals in our daily lives is becoming increasingly important. Metals are everywhere, from your smartphone’s inner circuitry to the car you drive. One of the crucial properties that engineers, architects, and material scientists consider when selecting a metal for a particular application is its thermal conductivity. But what does that mean, and which metals excel in conducting heat?

What is Thermal Conductivity?

Thermal conductivity measures the ability of a metal to conduct heat. Thermal conductivity provides a quantitative way to specify how a temperature gradient within a material drives the flow of thermal energy. This property varies across different types of metal and is crucial to consider in applications with high operating temperatures.

When a material has high thermal conductivity, it means that heat will pass through it quickly. In contrast, metals with low thermal conductivity are considered thermal insulators. In pure metals, thermal conductivity stays roughly the same with temperature increases. However, in alloys, the thermal conductivity increases with temperature.

Which Metals Conduct Heat the Best?

When it comes to thermal conductivity, not all metals are created equal. Some are exceptional conductors of heat, while others are better used as insulators. Let’s take a closer look at how various metals rank for thermal conductivity.

Common Metals Ranked by Thermal Conductivity

Rank      Metal                    Thermal Conductivity [BTU/(hr·ft⋅°F)]

1             Copper                 223

2             Aluminum           118

3             Brass                     64

4             Steel                      17

5             Bronze                  15

As you can see, copper and aluminum have the highest thermal conductivity out of the more common metals, while steel and bronze have the lowest. Heat conductivity is fundamental when deciding which metal to use for a specific application. As copper is an excellent conductor of heat, it’s suitable for heat exchangers, heat sinks, and even saucepan bottoms. Because steel is a poor conductor of heat, it’s ideal for high-temperature environments like airplane engines.

Some applications requiring metals that are good thermal conductors include heat exchangers, heat sinks, and cookware.

Heat Exchangers

A heat exchanger is a common application where good thermal conductivity is essential. A heat exchanger is designed to transfer heat from one medium to another efficiently. A solid wall typically separates the two media to prevent mixing, although some specialized heat exchangers allow direct contact between the media.

The efficiency of a heat exchanger is often measured by its “effectiveness,” which is the ratio of the actual amount of heat transferred to the maximum possible amount of heat that could be transferred with infinite surface area and time.

Copper is a popular choice for heat exchangers in industrial facilities, air conditioning, refrigeration, hot water tanks and under-floor heating systems. Its high thermal conductivity allows heat to pass through it quickly. Copper has additional properties desirable in heat exchangers, including resistance to corrosion, biofouling, stress, and thermal expansion. Aluminum can also be used as a more cost-effective alternative in some heat exchanger applications.

There are different types of heat exchangers, each suited for specific applications:

Shell and Tube Heat Exchangers – Consists of a shell (a large vessel) with a bundle of tubes inside. One fluid flows through the tubes, and the other fluid flows outside the tubes but inside the shell.

Plate Heat Exchangers – Made up of corrugated plates stacked on top of each other. Fluids flow between the plates, and the corrugated pattern enhances heat transfer.

Finned Tube Heat Exchangers – Uses tubes with extended surfaces (fins) to increase the heat transfer area, making the process more efficient.

Plate-Fin Heat Exchangers – Combines plates and fins and is often used in applications where compact size and efficiency are critical, such as in aircraft engines.

Regenerative Heat Exchangers – Uses a single fluid that passes alternately through a hot and cold exchanger to save energy and improve efficiency.

Direct Contact Heat Exchangers – Allows the two fluids to come into direct contact, which can be more efficient but only suitable when mixing the fluids is acceptable.

Heat exchangers are commonly used in the following situations:

Industrial Facilities

Heat exchangers in industrial facilities include fossil and nuclear power plants, chemical plants, desalination plants and marine services.

In industrial facilities, copper-nickel alloy is used to construct the heat exchanger tubing. The alloy has good corrosion resistance, which protects against corrosion in saltwater environments. It also has good biofouling resistance to avoid the formation of algae and sea mosses. Aluminum-brass alloy has similar properties and can be used as an alternative.

Heat exchangers can contribute to sustainability initiatives by enabling heat recovery from industrial processes. The recovered heat can be redirected to other parts of the facility for heating or pre-heating needs, significantly reducing energy consumption and lowering greenhouse gas emissions.

Solar Thermal Water Systems

Solar water heaters are a cost-effective way to heat water in which a copper tube transfers the solar thermal energy to water for domestic or industrial use. In these systems, solar collectors absorb solar radiation, typically in the form of flat-plate or evacuated-tube designs, where it is transformed into heat. The challenge then lies in transferring this heat to water in a controlled and effective manner, which is where heat exchangers come into play.

In a typical solar thermal water system, a heat transfer fluid—often a mixture of water and antifreeze—is circulated through the solar collectors to absorb the solar energy. This heated fluid then passes through a heat exchanger, transferring its thermal energy to the domestic water supply without mixing the two fluids. This separation is vital, especially when the heat transfer fluid includes non-potable substances like antifreeze. Copper is used because of copper’s high thermal conductivity, air and water corrosion resistance, and mechanical strength.

Gas Water Heaters

Heat exchangers play an essential role in the functioning of gas water heaters, particularly in tankless or “on-demand” systems in residential and commercial boilers. Unlike traditional tank-style water heaters, which always keep a large volume of water hot, tankless gas heat heaters use heat exchangers to rapidly heat water on demand, offering both efficiency and instant availability.

In a tankless gas heater, cold water flows into the unit when a hot water tap is opened. This activates the gas burner, which heats a metal heat exchanger. As water flows over the heat exchanger, thermal energy is transferred from the hot metal surface to the water, raising its temperature to the desired level. The heat exchanger’s design allows for a large surface area in a compact space, maximizing the heat transfer rate and rapidly delivering hot water. For gas water heaters, copper is preferred because of its high thermal conductivity and ease of fabrication.

Forced Air Heating and Cooling

Heat pumps using air have long been used for residential and commercial heating. They work via air-to-air heat exchange through evaporator units. They can be used in wood furnaces, boilers, and stoves. Again, copper is typically used for its high thermal conductivity.

Heat Sinks

Heat sinks are a type of heat exchanger that transfers heat generated by an electronic or mechanical device into a moving coolant fluid. The fluid transfers the heat away from the device, allowing it to cool to the desired temperature. Metals with high thermal conductivity are used.

Heat sinks are designed to maximize the surface area in contact with the coolant fluid and can vary significantly in design depending on its application. It may consist of a flat metal plate or a complex array of fins, pins, or channels designed to increase the surface area available for heat dissipation.

Computers use heat sinks to cool central processing units or graphics processors. In electronic devices like CPUs and GPUs, the heat sink is often paired with a fan to actively circulate air through the fins, enhancing the cooling process. Heat sinks are also used in high-power devices like power transistors, lasers, and light-emitting diodes (LEDs).

Aluminum alloys are the most common heat sink material. This is because aluminum thermal conductivity is high, it is lightweight and easy to manufacture, and it costs less than copper. However, copper thermal conductivity is high and might be used where needed. Some heat sinks use a combination of aluminum fins with a copper base.

Cookware

A more household use of metal with good thermal conductivity is in cookware. You don’t want to wait all day for your food to heat up. Metals such as aluminum and copper are commonly used in constructing pots, pans, and other cookware because of their excellent thermal properties.

One of the most immediate benefits of using a high-conductivity metal is uniform heat distribution. Poor heat distribution can lead to hotspots, which cook food unevenly and increase the risk of burning. High-conductivity metals spread heat more uniformly across the cooking surface, ensuring that food is cooked evenly and thoroughly, thus improving its taste and texture.

Cookware made of high-conductivity metals responds more rapidly to changes in heat, allowing for better control during cooking. This is especially important for recipes that require precise temperature control, such as melting chocolate or simmering sauces. The faster heat-up and cool-down times also mean less energy is wasted, contributing to overall energy efficiency in the kitchen.

Copper is often used in the bottoms of high-quality cookware because the metal rapidly conducts the heat and spreads it evenly across its surface. However, if you’re on a budget, you can use aluminum cookware as an alternative. Heating your food may take a little longer, but your wallet will thank you!

At Metal Supermarkets, we are committed to providing you with a diverse range of high-quality metals that excel in thermal conductivity and other essential properties. Talk to one of our store associates to discuss what metal would be ideal for your project.