/sci/ - Science & Math

WHOA...

I MUST BUILD YOUR IDEA

VERY COOL OP

WOULD READ AGAIN

I dont think the vaccum we can create is "100% vaccum" (is it?) and hence, a little bit of heat dissipation would still ensue, even if small.

Also, have you checked how do normal termic vials work?

>>2922073

>doesn't know that no absolutes in real life

it would just be a slightly better thermos, at 666 times the cost.

The thought has occurred to you many times probably because you own one of these already. They cost about $12, because they don't waste a lot of money on magnets and the air pocket trapped between the inner and outer pieces is a good enough insulator.

An ideal container so the initial temperature never changes?
No. It'd violate thermodynamic laws.
>>2922114
Perfect vacuum is a theoretical concept.
>>2922126
This is the closest you'll get to the ideal container.

Not if you have any intention of ever taking/pouring the contents out.

Also, while a vacuum does not convect or conduct heat, thermal radiation may still pass through it. Perhaps the better way of improving a Thermos' performance (or any Erlenmeyer flask) is by placing multiple thin reflective layers within the vacuum, to reflect any thermal radiation back to the side it came from.
>Coat interior of vacuum chamber with carbon-black (both content-side and environment-side)
>three or four layers of aluminized mylar to reflect thermal radiation back to the warm side rather than letting it pass to the cold side

If this works well, THEN maybe we can look again at better-insulating the conductive edges of our vacuum chamber.

To all you haters out there...

It might be inefficient and impractical. But it would be fun to build. And definitely fun to observe if it was successful.

>>2922122
>>2922135

I'm well-aware of the physical laws that would make such an object impossible. The original goal of this post was to identify the exact mechanism that would ensure that the second law of thermodynamics isn't violated.

In summary:
1. No perfect vacuum (though it'd be interesting to find out how much better "industrial vacuum" would be when compared to the usual air layer)

2. >>2922126
>Magnets are expensive
Irrelevant.

>>2922146
>Thermal radiation may still pass through it
Thanks.

I have a thermos that'll keep coffee warm/hot for 48 hours or so. It's fucking amazing.


Either way this would be a fun design-experiment.

>>2922180

Yeah really.

I think self sufficiency is cool. It seems like a very large thermos could essentially be a powerless refrigerator.

You could cool it once using a manually operated Hilsch vortex tube, and then preserve the temperature using a vacuum, magnet box thing.

>>2922214
>manually operated Hilsch vortex tube
>manually operated

>>2922236
What?

What did I do this time?

>>2922073
I like this idea, i think it would improve the heat/cold life substantialy.
>>2922240
dont worry there are a bunch of idiot fuck faces here that constantly argue about absolutes, and all that shit. ignore them.

BUT HOW WILL YOU OPEN IT, OP??

>>2922292

I guess you would have to ruin the vacuum. Which would make this better for long term containment.

I think what that guy was saying, was that because my idea of manually operated no one would do it.

I think, if you made a manually operated refridgerator, that worked like a thermos... Im going to guess it wouldnt take very much physical activity to cool down.

If I had to ride a bike to cool a refrigerator sufficiently for a few days. And it would cost no electricity. I would do it. Thats just me and I think it could get more efficient than that.

2nd law....
cannot perfect anything

eg vaccum

also radiation.

>>2922307
>Pedal-powered refrigerator
You want to actually do this?
Make it use an all-gas Stirling Cycle, post the results on /sci/ and I'll love you forever.

>>2922350

I might totally build something like this this summer.

The refrigerator I mean. I would love to build something like your stirling cycle, but, I dont have the confidence to build something like that.

But, its an awesome idea.

I dont know... Ill figure some shit out.

>>2922307
I don't think you understand thermo at all.

>>2922373

What?

Heat will still radiate out as various frequencies of IR from the container, even with a perfect vacuum.

>>2922398
he meant themos

>>2922398
protip: generously estimate the amount of power cycling generates. Now compare this to the power that a fridge consumes.

>>2922413
No. I abbreviated thermodynamics, sorry for the confusion.

>>2922711
Protip: Smaller refrigerators consume much less power than large ones, and the Stirling cycle is more efficient than the Rankine cycle for a given temperature gradient.

I don't think this is meant to be practical, anyways. It might end up being just a whacky way to cool off a six-pack of beer while simultaneously getting exercise.

And one more thing, to satisfy your requests:
>Power generated by an average cyclist (endurance, not sprint): 200 watts
>Power consumed by a typical new refrigerator: 500-1000 watts

>>2922866
so you're suggesting that a 200w (ignoring generator inefficiency) endurance cycling session could power a 500w refrigerator?

I'm telling you it's not only impractical but also near impossible to compress a gas solely with pedal power. Do what you want. Get a magnetic clutch compressor and connect it to your pneumatic circuit, pedal like you mean it, flick that solenoid switch and look what happens. I look forward to the results.

>>2922995
>so you're suggesting that a 200w (ignoring generator inefficiency) endurance cycling session could power a 500w refrigerator?
No, I'm suggesting a 200-watt mini-fridge could be built.
>I'm telling you it's not only impractical but also near impossible to compress a gas solely with pedal power.
Holy fuck. EVERYWHERE I TURN, /sci/ proves to me how stupid they really are. In the world they live in, things like mechanical advantage, insulation, etc. do not exist.

Fuck this board, everyone here is retarded.

>>2923018
even if you actually build the device, i bet you'll quickly lose the motivation to cycle the thing.

>>2923051
When that happens, I'll build a solar-thermal generator to run it instead (ALSO using a Stirling engine).

>>2923018
mechanical advantage? insulation? Do you even know how these fuckers work? Next time ask your parents or at least google the fucking concept before you write something retarded.

>>2923079
>10 in^2 piston requires 120 lbs to exert the required pressure
>I can only exert about 40 lbs on the pedal
>3-to-1 gear ratio, or 3-to-1 leverage via longer pedal crank and shorter piston stroke
Problem.
Fucking.
Solved.

The fact that you fuckers can't even comprehend simple mechanical solutions such as this baffles me.

>>2923109
>doesn't know that increasing torque will reduce angular velocity

HOW THE FUCK WILL THIS COMPRESS YOUR REFRIGERANT NIGGER?

>>2923162
>Implying that compression is somehow rate-dependant
I'm trying to REJECT HEAT during compression. Slow changes are more isothermal and less adiabatic, hence the reduced speed hurts nothing in terms of efficiency.

GTFO, you dim-witted untermensch.

Im back.

Yeah Im not talking about a full scale fridge. Definitely just a smaller one. I dont need much space.

Second of all, I wouldnt even considering man powering a refridgerator unless I had this concept of vacuum magnet efficiency.

Third of all, I dont play on electrically powering a fridge. There would be no electric parts. there would be an air pump that would blow air well below freezing into the box. via a hilsch votrex tube.