Heatsink Thermal Resistance Calculation

[MikehZA]

Hi, I have some Aluminium flat bar that I would like to use as a heatsink. Is there a way to calculate the Thermal Resistance (deg C / W) based on surface area or volume? Regards, Mike.

 

[FvM]

It's basically the surface area, that matters. In addition, the surface orientation (horizontal, vertical) plays a role. Without forced cooling, the heatsink action is based on air convection. A vertical surface allowing a free convection has a slightly lower thermal resistance for this reason.

The heatsink material introduces additional thermal resistance., particularly when using thin sheets, or generally large length/cross section ratios. The material thermal resistance adds to the heat sink to ambient thermal resistance, but can be often ingnored in a rough estimation.

As a rough estimation, I would expect a thermal resistance of 5 - 10 K/W for 100 cm² surface area.

 

[MikehZA]

Thanks FvM much appreciate your input. - Mike

 

[eem2am]

the way to measure it is too use thermal paste to connect a power resistor to it and get it dissipating.....then you measure the temperature difference between ambient and the bit of the heatsink nearest the resistor..........then you get you kelvin-per-watt value

 

[FvM]

Yes, it's surely the best method to get the thermal resistance of a given heatsink geometry.