How well do different metals (specifically copper and aluminium) conduct heat to air?

[Commander Kinsey]

I do not understand people paying £25K for a new car when you can get a used one for £1K.

[Bing AI]

The thermal conductivity of a material is a measure of its ability to conduct heat. It is defined as the amount of heat that flows through a unit area of a material in unit time when there is a temperature gradient perpendicular to that area1.

If metal A has exactly twice the conductivity as metal B, then it can be deduced that metal A conducts heat to the air faster than metal B1. However, we cannot deduce that metal A conducts heat to the air exactly twice as fast as metal B1.

The factors that affect the rate of conduction include temperature difference, cross-sectional area, length (distance heat must travel), and time [1]. The thickness of the material through which the heat transfers also affects conduction [2].

[1]

[Max Demian]

But the stuff has to conduct heat through itself in order to conduct it to the air.

[The Natural Philosopher]

Utter crap. The rate of heat transfer to the air is utterly dominated by the conductivity of the air at the surface and the radiativity of the surface. And the area of the surface

Heat transfer does not have a 'speed'

[The Natural Philosopher]

Yes, but that's practically a short circuit with any metal heat sink

The picture in my mind is someone replacing the lead out wires to a 1K resistor with solid silver ones to reduce it's resistance.

Technically it will, but by so little its practically meaningless

[Ralph Mowery]

It could be the color of the metal or how rough the serface is.

[Commander Kinsey]

Forget air for the moment. Take metal A and metal B. Touch them together (very well, finely machined). What is the conductivity at that surface? The average of the two metals?

[Commander Kinsey]

Why don't they make the surface of heatsinks really rough? As in like orange peel, more surface area?

[Bing AI]

The rate of heat conduction between two metals in contact which have different conductivities is determined by the thermal contact conductance coefficient. This coefficient indicates the thermal conductivity or ability to conduct heat between two bodies in contact. The thermal contact conductance coefficient is dependent on the surface roughness, surface cleanliness, and the nature of the materials in contact¹.

Source: Conversation with Bing, 20/05/2023 (1) Thermal contact conductance - Wikipedia.

What is thermal conductivity? (article) | Khan Academy. Rate of conductive heat transfer at a boundary between two different ....

[Bing AI]

The side of the heatsink which is in contact with the air is usually designed to have fins or other structures that increase the surface area. The increased surface area allows for more efficient heat transfer from the heatsink to the air. However, making the surface too rough can create air pockets between the heatsink and the air, which can reduce the heat transfer rate.

[The Natural Philosopher]

Indeed. Most heat is lost by a heatsink though conduction to the air which then convects it away. The smoother it is, the better the airflow