Heat transfer limit of a block into a heat sink

Question

I seem to recall a limit to how fast a block can dissipate heat into a heat sink. I have a block of copper generating heat attached to a heat sink held at a constant temp. If you know the formula I need that would be great otherwise just the name for the principle so I can look that up.

Thanks

Answer 1

Basically heat flow is like series resistors. the copper block is in series with the junction between the block and the heat sink, and that is in series with whatever is acting to heat sink it.

Each element has a thermal resistance, usually expressed in watts per degree C, ie, with a temperature difference of X degrees C there is Z watts of heat flowing.

Since they are in series, you add them up to get a total thermal resistance.

Once you have that, if you know the watts being dissipated, you can calculate the temperature difference, or vice versa.

If you have a block of metal, it's possible to calculate thermal resistance if you know the dimensions and the metal.

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