Heat sink thermal resistance

Is there any way to figure out the thermal resistance of a heat sink without using a datasheet or using it in an actual circuit? I mean, simply by knowing its dimensions and material.

• It's not that easy. The number of fins, the total surface area, the mass and the material properties all determine the actual thermal resistance. One thing you can do is to estimate by comparing to a known heatsink which has similar dimensions. Commented Dec 7, 2021 at 13:43
• Simulations.... Commented Dec 7, 2021 at 14:25
• Look at an online electronics catalogue, and match your heatsink to pictures and dimensions of the ones they sell, then compare specifications. Commented Dec 7, 2021 at 15:23
• Does this answer your question? How can complex shape's heat sink thermal resistance be determined Commented Dec 8, 2021 at 9:10
• Does this answer your question? Heatsink size calculation Commented Dec 8, 2021 at 9:38

Is there any way to figure out the thermal resistance of a heat sink without using a datasheet or using it in an actual circuit? I mean, simply by knowing its dimensions and material.

Not really because if you don't use the data sheet you cannot know what size electrical device is meant to be accommodated. The surface area contact of the device to be fitted totally reshapes $$\R_{TH}\$$ - more surface area contact means lower $$\R_{TH}\$$ and less surface area contact means greater $$\R_{TH}\$$. So, you need to know things about the heatsink that cannot be necessarily determined by vision alone.

Is there any way to figure out the thermal resistance of a heat sink

$$\R_{TH}\$$ applies only to the specific component attached to it i.e. there are no $$\R_{TH}\$$ values for heatsinks without defining the physical interface between component and heatsink. Also, if the heatsink is asymmetrical then you won't get the same value of $$\R_{TH}\$$ when the device/component is mounted in a different position or face.

So, it's all about attaching your electrical device to the heatsink and getting the device to operate at a certain constant power. This is done by controlling the voltage and current to the component.

Stage 1

Put a constant power into that component with it unconnected to the heatsink. The temperature will stabilize at some point. Make sure it is less than the operating temperature for the device/component. Record that temperature.

You can then calculate what $$\R_{TH}\$$ is from the power value and the two stabilizing temperatures. Heatsink and component orientation will matter.