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Nano-engineered thermoelectrics enable scalable, compressor-free cooling

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Re: Nano-engineered thermoelectrics enable scalable, compressor-free cooling

#41

Post by usrusr »

s_tec wrote: post #21

Thermoelectric cooling is pretty inefficient, because the materials need to balance competing requirements: - Good thermal insulator - Good electrical conductor - Good semiconductor This is because the hot & cold sides are sandwiched closely together as a PN junction, so once you move heat from one side to the other, it just leaks right back. Mechanical cooling doesn't have this problem, because the hot & cold sides…

What if you use the technology in places where you actually want to maximize heat conductivity?

I'm thinking of the separation walls in counterflow heat exchangers (only useful at the end where the incoming stream is closer to its end temperature than the delta offered by thermoelectrics I guess). Can it do whatever it does across a temperature gradient?

Re: Nano-engineered thermoelectrics enable scalable, compressor-free cooling

#42

Post by scotty79 »

nandomrumber wrote: post #31
scotty79 wrote: post #26

Earlier quoted context omitted.

You could have heat pipe filled with liquid that evaporates at 5 degrees. This way it would draw heat from ambient level temperature and lead it to peltier device that would cool it below 5 deg and liquefy it back again. This way you could have peltier in the middle of your thick insulation layer with heat pipes drawing the heat into it from the cooled space and drawing the heat from the other side of it outside (usi…

I think you may have just reinvented absorption refrigeration, previously invented by Ferdinand Carré in 1858. https://en.wikipedia.org/wiki/Absorption_refrigerator

Not really. The role of heatpipes is not to cool, just to transfer heat to and away from peltier device so it's easier to insulate hot and cold side.

Re: Nano-engineered thermoelectrics enable scalable, compressor-free cooling

#43

Post by bigattichouse »

A lot of people throw around 5% efficiency for Peltiers, and it's just not true - it depends heavily on the temperature differential and current vs. IMax. You can (with care) drive them >2.0 COP.

This isn't anything like a compressor or heatpump system, but Peltiers get a bad rap... they move heat really well if you're not pushing them to the edge.

Here's a nice chart. At 10k difference and 0.1 current max, you're over 2.5 COP. https://www.meerstetter.ch/customer-center/compendium/71-pel...

Re: Nano-engineered thermoelectrics enable scalable, compressor-free cooling

#44

Post by K0balt »

It’s astonishing how here, in an ostensibly technical forum, the vast majority of comments are left by people who did not even skim the article. At least read through the informative comments left by those who did read it before giving your venerable opinion based on the information that was already in your head? I mean, isn’t the point of an article or paper to present new, novel information?

Re: Nano-engineered thermoelectrics enable scalable, compressor-free cooling

#45

Post by [deleted] »

bigattichouse wrote: post #43

A lot of people throw around 5% efficiency for Peltiers, and it's just not true - it depends heavily on the temperature differential and current vs. IMax. You can (with care) drive them >2.0 COP. This isn't anything like a compressor or heatpump system, but Peltiers get a bad rap... they move heat really well if you're not pushing them to the edge. Here's a nice chart. At 10k difference and 0.1 current max, you're ov…

[deleted]

Re: Nano-engineered thermoelectrics enable scalable, compressor-free cooling

#46

Post by perlgeek »

audunw wrote: post #34
vlovich123 wrote: post #20

Earlier quoted context omitted.

Nah. Heat pumps are ~10-100x more efficient than thermoelectric. Thermoelectric is just inefficient mechanism and is inherently difficult to scale up as the more electricity gets generated so does more heat which inhibits the temperature gradient you’re trying to utilize. There’s a reason water cooling is preferred instead of peltier to ferry heat away from electronic. Magnetocaloric is super interesting though as an…

It’s really, really weird to comment on the efficiency of these devices on an article like this, without actually checking the paper being referenced. Like, we know traditional thermoelectric are inefficient. But that’s the whole point of this research. To improve it. It seems like they achieve a CoP of 1.3-6.8 (depending on heat transfer load) versus e.g. - CoP of 2-4 which is common for a household refrigerator. So…

The abstract of the paper mentions temperature differential of 1.3°C and 2°C - not really inspiring for use in a refrigerator.

Neither the article nor the abstract go out of their way to compare the efficiency of the new system to traditional heat pumps. Makes it kinda hard for a lay person to really assess the situation.

Re: Nano-engineered thermoelectrics enable scalable, compressor-free cooling

#47

Post by Henchman21 »

K0balt wrote: post #44

It’s astonishing how here, in an ostensibly technical forum, the vast majority of comments are left by people who did not even skim the article. At least read through the informative comments left by those who did read it before giving your venerable opinion based on the information that was already in your head? I mean, isn’t the point of an article or paper to present new, novel information?

It’s the day before a holiday in the US. No one is thinking, we’re all just knee-jerk existing for another handful of hours and then… Then we engage in that once a year ritual of lighting up explosives and making a pilgrimage to the ER, where no one can afford proper treatment. /s

Happy 4th all!

(With apologies for the wildly off topic comment)

Re: Nano-engineered thermoelectrics enable scalable, compressor-free cooling

#49

Post by wrigby »

bigattichouse wrote: post #43

A lot of people throw around 5% efficiency for Peltiers, and it's just not true - it depends heavily on the temperature differential and current vs. IMax. You can (with care) drive them >2.0 COP. This isn't anything like a compressor or heatpump system, but Peltiers get a bad rap... they move heat really well if you're not pushing them to the edge. Here's a nice chart. At 10k difference and 0.1 current max, you're ov…

I didn’t know this, and it jumps out to me because 10k is pretty much the exact difference between room temperature and wine fridge tenperature - I wonder if this is actually not a horrible application for peltiers?

Re: Nano-engineered thermoelectrics enable scalable, compressor-free cooling

#50

Post by speed_spread »

adrian_b wrote: post #17
speed_spread wrote: post #10

Earlier quoted context omitted.

> can't move the heat very far. Heat pipes (as in CPU heatsinks) can passively move the heat up to a feet away. Far enough to allow effective insulation between cold and hot side. From there you can move the heat further away with a fan.

Heat pipes only reduce the thermal resistance between 2 points. They cannot cool something below ambient temperature. Thermoelectric coolers do not compete with heat pipes. They are useful only when you want to obtain a temperature lower than the ambient temperature. Otherwise, heat pipes or liquid flow cooling are the right solutions.

I was suggesting combining Peltier element _and_ heat pipes.
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