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I'm trying to use a Peltier module (e.g. TEC1-12703) for heat diffusion physical experiment. An external power source provides around 8V with 1A current, so the generated heat from the surface of the module is quite good and very hot to touch.

However, when attaching a thin aluminum foil of 7cm x 7cm (with a thermal paste) to the hot side, only the part that is directly connected to the module becomes hot, but heat is not spread around at all (maybe only very very close to, ~5mm). It would be expected to receive a diffusion effect so that the foil will become hot until equilibrium is reached, since the Peltier module pumps heat all the time.

What am I missing? Is it because the foil is too thin so heat is dissipated so quickly?

[Edit on May 8th, 2023]

Following @john-doty answer below, few further questions come to my mind:

  1. Can I compute the rate by which heat is removed from the foil and what is the necessary heat power input (Watts) to overcome this effect? Where can I find typical constants for a thin aluminum foil? (assuming no airflow is forced upon)
  2. Is there a better electrical device in the form factor of a small Peltier module that could pump more energy into the foil?

Thanks, Moti.

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  • $\begingroup$ You need to bond the module thermally with a heat transfer paste or other kind of thermal interface material (like silicone sheets) to the metal. Thermal paste used to bond heat sinks to CPUs will probably do just fine. I would also thermally insulate the edges of the module and your sample, e.g. with a piece of Styrofoam (assuming that you don't need high temperatures). $\endgroup$
    – FlatterMann
    Commented May 7, 2023 at 16:23
  • $\begingroup$ @FlatterMann thanks, that's what I did, but maybe insulating the edges could help a little. $\endgroup$
    – Moti
    Commented May 8, 2023 at 9:52
  • $\begingroup$ This question and this one are partially relevant. Using the Al thermal conductivity you can calculate how fast heat can flow out through the foil. If you can do the experiment in vacuum to eliminate air cooling, the heat loss radiated from the foil could be calculated using Stephan-Boltzmann integrated over the area and temperature profile of the foil. If you just want to heat the wire, why not just use a bit of nichrome heater wire? $\endgroup$
    – David Bailey
    Commented May 8, 2023 at 13:44
  • $\begingroup$ This is another example of an experimental physics question being closed as "engineering" even though any answer will depend almost entirely on physics, and experimental physicists are far more likely to be interested and able to help. $\endgroup$
    – David Bailey
    Commented May 8, 2023 at 13:48
  • $\begingroup$ Thank you @DavidBailey, actually the examples you gave are perfect for further understanding of the phenomena. It gives a clue where to improve the experimental design. $\endgroup$
    – Moti
    Commented May 9, 2023 at 14:58

1 Answer 1

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If the foil is thin, air will efficiently remove heat from the foil, while heat will only diffuse into the foil slowly. The cross sectional area for cooling is the area of the foil, while the cross sectional area for heating is the thickness of the foil times the circumference of the heater.

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  • $\begingroup$ OK, that's an interesting point to follow, in case the setup would be isolated from flowing air in a casing, should that improve the diffusion? $\endgroup$
    – Moti
    Commented May 8, 2023 at 9:53
  • $\begingroup$ @Moti Perhaps. A thicker piece of metal would help more, I think. $\endgroup$
    – John Doty
    Commented May 8, 2023 at 12:35
  • $\begingroup$ Thanks, I'll give that a try :). $\endgroup$
    – Moti
    Commented May 8, 2023 at 13:15

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