TEC usage

Hi there, I am currently working on a product which aims to aid in sports recovery. The product is a wrap which goes around a part of the leg and the user can select a hot or cold recovery session.

To achieve the hot and cold effect I am using a peltier module aka a TEC(thermoelectric cooler) and reversing the polarity determined by what setting the user chooses (hot or cold). When the heat setting is selected the peltier will rise to 50 degrees (celsius) and when the cold setting is selected the peltier should be at around 5 degrees.

I have been testing the TEC with an adjustable power supply and I cannot get the peltier device to drop to anything below 20 degrees. Any advice on how to to reduce this to the desired 5 degrees?

Thanks for any replies

Have you made a thermal model of the system? Doing so will go a long ways in helping understand and address your issues. Monitor your hot-side temperatures also; the temperature you see at the cold side is directly related to what’s present on the hot side.

It’s pretty common for folks to underestimate the amount of hot-side heat sinking required to achieve any significant refrigeration effect with a TEC. They’re really much more effective as heaters, because every electrical watt one puts in comes out the hot side as heat. Not so from a cooling perspective; one might have to put two or three electrical watts in, in order to suck just one thermal watt off the cold side.

The best cooling value for one’s electrical money when using TECs usually comes at around 30-40% or rated maximum electrical input. Beyond that, there’s a pretty sharp schedule of diminishing returns; the difference between operating at 80% and 100% of rated electrical input might be only a 3-4% increase in potential cooling performance.

Long story short, the standard suggestions for achieving lower cold-side temperatures with a thermoelectric cooler are backing off from maximum rated electrical inputs, using a more capable hot side heat sink, and a bigger fan to cool it.