Is there a name for the point where a Peltier cooler loses power and the cold side becomes warmer than the temperature around it and vice versa after power has been lost?

  • \$\begingroup\$ I'm not sure about your wording. Are you talking about power being removed from the cooler, or are you talking about the point where you're running so much current through it that it's heating the "cold" side instead of cooling it? \$\endgroup\$ – TimWescott Apr 9 '19 at 0:17
  • \$\begingroup\$ after power is being removed from the cooler it causes the cold side to become slightly hotter than ambient before returning to ambient. \$\endgroup\$ – Caleb Taber Apr 9 '19 at 0:21
  • \$\begingroup\$ Could you clarify your question? Even in spite of the fact that I'm not sure there's a name for the effect, other than "oh @#$%, the power went out!". \$\endgroup\$ – TimWescott Apr 9 '19 at 0:24
  • \$\begingroup\$ I've built a device that intermittently powers a Peltier device but when power is cut I get the previously mentioned heat spikes. I was looking to see if this is a normal issue with Peltier devices. \$\endgroup\$ – Caleb Taber Apr 9 '19 at 0:26
  • 5
    \$\begingroup\$ Yes, it's normal. They are poor insulators (it's part of the reason they're not very efficient). And like any refrigerator, they work by pumping heat into the "hot" end. So as soon as you turn off power, that heat flows from the hot end to the cool end. Running a Peltier device intermittently is to be avoided, if possible. \$\endgroup\$ – TimWescott Apr 9 '19 at 0:33

It's called poor thermal design. The Peltier devices reach a maximum Q or heat energy transfer when the cold side goes into an infinite heatsink.

Without a good heatsink, the cold and hot side reach an equilibrium hotter than the ambient.

Therefore consider your thermal conductance on both hot and cold side to be of utmost importance. This requires a good thermal heat spreader with grease and forced air 1 to 3 m/s velocity over the heat spreader fins. e.g. a CPU cooler for the hot side and larger mass with low Rth on the cool side.

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