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Can Cooler Project – Part 1

This is part 1 of the Can Cooler Project (as of this post, still a work in progress).  The plan is to make a small standalone soda can cooler that can rapidly chill on demand, a single 12 oz can of soda.  Here is what I have so far!

can cooler prototype

I’m shooting for a 30 deg F temperature drop in under 15 minutes.  The basic design approach is to sandwich a Peltier element between a CPU heat sink and an aluminum cold sink that I will machine to the contour of a can using the Taig Micro Mill.  I’ve seen the mini fridge style coolers out there and from what I’ve read, they don’t perform well at all.  The USB powered versions are just silly as they’re limited to ~0.5 A at 5 V (~2.5 Watts).  Also, conductive heat transfer occurs where a flat plate contacts the base of a can.  As for the power supply, I’m using an old computer PSU and using the 12V rails to drive the Peltier element as well as the cooling fan.

Here is the Peltier element I’m using (model # TEC1-12710):

Peltier Element Part Number TEC1-12710

This is a CPU heatsink-fan combo from my junk box.  It didn’t work so well but I took more pictures of it than the other so…

Now we’re getting to the machining.  Here is a chunk of aluminum bar stock that will become the cold sink:

aluminum bar stock

Milling the surface flat for contact with the Peltier element:

I used the fly cutter to create the can diameter curvature.  Setup is easier than you might think.  First I used an edge finder to locate the surface.  Next, I moved the y axis half the can diameter away from the fly cutter.  In order to set the cutting tool for performing a boring type operation, I rotated the cutting tool as shown and slid it out until it just barely touched the material; tighten up the the cutting tool and it’s ready to go! 

using a fly cutter to bore

Making progress; I had to increase the spindle speed to 5500 RPM and take very light cuts (.002 to .004):

can contact surface emerging

The 2.6 inch diameter “boring” operation (with fly cutter) is complete:

Cold sink is almost complete – just need to cut off the end:

almost done

Cutting off the excess on the bandsaw:

Back to the mill and trimming of the excess with an end mill:

side milling complete

Ready for first power-on test!  Thermal compound is used between both contact surfaces.  The Peltier element and CPU fan are hooked up to the 12 V rail on a PC PSU.

heat sink in place

It works!  Well, it gets cold enough to create condensation anyhow: 

So this is where I realized that the heat sink was not going to cut it.  The heat sink was almost too hot to touch after just a few minutes of run time which means the cold side wasn’t getting as cold as it could.  Peltier elements run more efficiently when the hot side is not so hot.  I removed the fan and placed the heatsink in an icewater bath to see where things could go given a better heat sink.  This resulted in much cooler cold side temps and so I switched heat sinks for the one shown in the nextpicture (with heat pipes, a 120 mm fan, and lots of fins).  Now the hot side doesn’t feel hot at all and the cold side is much cooler.  In part 2 I plan to build an enclosure and post some actual performance data.  That’s all for now!

bigger heat sink!
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