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Peltier devices for "personal cooling" ? (or heating)

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coppercone2:

--- Quote from: TheMG on August 01, 2020, 01:42:26 am ---While it may provide a feeling of cool on the back of your neck, it really isn't going to do a whole lot to actually keep your body cool.

The device reportedly weights 3 ounces (85g) and can run for up to 90 minutes on a charge. If all of that weight was just the battery, using some of the best battery technology currently in mass production, you'd have around 23Wh of battery capacity, best case scenario.
Over a 90 minutes discharge, that's 15W power consumption.

The coefficient of performance in most practical TEC (peltier) implementations is between 0.4 to 0.7. So for a TEC operating at 15.3W of power input (again, ignoring the power used by the fan), will be able to "move" between 6 to 11W worth of heat.

The average human body dissipates approximately 100-120W of heat, at rest. This goes up considerably with exercise.

So very best case scenario... the device will help dissipate about 10% of your body heat, while you're sitting doing nothing. In reality, probably no more than 5%.

It may provide a pleasant feeling of coolness on the back of your neck but that's about it. You'll probably sweat just as much as if you weren't wearing the device.

--- End quote ---

There are three levels of cooling or warming, plus an additional boost mode that’s limited to two minutes and a control for the speed of the “fan.”

Kevin.D:
The Physics is against it, don't think it will nearly as effective as a simple fan blowing air on your skin .
The most relevant number here regarding peltiers is their heat pumping efficiency ,
ratio of how much power is put in to how much power(as heat) it will pump from cold side to the hot side,
The cheap peltiers I have here are ~ 0.5 efficient (100 W input to pump 50 W Heat from cold to hot side) .
Keeping in mind the peltiers heat sink/fan has to dissipate the power to do the work plus the heat(power) we are pumping
It's heat-sink/fan will need to be dissipating to air ~ 3 times more heat than simply blowing the air directly on the skin ,
and I don't see that happening, the peltier sink would have to be fan + evaporative to compete with a fan blowing on Sweating skin and then also take into consideration  blowing air directly on to skin is collecting heat from a relatively large contact area compared to contact area between peltier cold side and skin which will  just result in a very cold small area of skin with limited conduction from surrounding area ( blood vessels in that area will also probably contract reducing heat conductivity from surrounding area even more).

Reminds me of an Eload Idea I had a few year ago . I got some cheap peltiers to mount power MOSFETS on and then derived the input power necessary to  drive the peltiers  directly from (or  via a voltage reg if necessary) the waste input power that was to be dissipated by the Eload. By pumping out heat from the mounted MOSFET I effectively increased the case to sink thermal capacity of the MOSFET  by whatever the peltier could pump (so about 50 Watts with my cheap peltiers at their abs Max input power ~ 100W).
This doesn't work out very cost effective though because MOSFET's (there are a few exceptions) are much cheaper than peltier elements and so to increase the overall sink to case thermal conductivity we can just use another MOSFET and put it in parallel and that's much less expensive than with my peltier idea .

Regards

OwO:
A thin mat with loops of embedded piping + water circulation and a separate radiator (evaporative cooling, peltier, or compressor) could work.

RoGeorge:
It has been done as cooling gloves.  I've seen some research to enhance running endurance (for military purposes).  They noticed the main problem was overheating, and also the most heat exchange happens through the head and the hands are.

Keeping the hand palms cool was enough to run longer distances.  Something like this:



(the video I was talking was different, probably older then the one above, with a temperature probe inserted near the heart, through the lungs, in order to measure the most efficient hands cooling technique - a too cool glove was not good because capillary blood vessel constrict at low temp, therefore making the heat exchange less effective).

cdev:
Thats what I have been thinking. I am going to try to see if I can adapt some computer hardware. First just for a small area. I would be happy to cool my neck.

I ofter wear a damp bandana I've pun under cool water and squeezed out. Some years we've been able to go almost without using AC, but this year its been on a lot. :(  Despite having very good insulation.


--- Quote from: OwO on August 01, 2020, 10:38:52 am ---A thin mat with loops of embedded piping + water circulation and a separate radiator (evaporative cooling, peltier, or compressor) could work.

--- End quote ---

Don't want to use anything toxic (CFCs) and have an interest in electronics, so peltiers sound like the way to go. Plus it will let me use up some of the tons of small HSF/fans that I have here from years of computer builds.

Also, I want to build a cold plate for making small amounts of ice cream on the fly. That way of making instant icecream is really good. Its very popular at the Jersey Shore. People who sell ice cream that way while people watch their ice cream being made (its done with showmanship) make a small fortune on hot days.

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