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“Cold Tube” cooling system uses half the energy of an air conditioner

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Re: “Cold Tube” cooling system uses half the energy of an air conditioner

#121

Post by aidenn0 »

eggsnbacon1 wrote: post #13
sparker72678 wrote: post #7

> The notoriously bad energy efficiency of air conditioners Air conditioners are actually pretty fantastically efficient for what they do. The problem with air conditioners is that there's no way to move a ton of heat without using a lot of energy. So, they do use a lot, but they make the most of it. What's truly bad are our buildings that have the minimal insulation and sealing possible, leaking all that cold air ri…

New buildings are rather efficient in US. The problem is old buildings that use 5X the energy for HVAC. I echo that AC is quite efficient. Far more efficient than traditional heating. There's a misconception that hot areas are less environmentally friendly due to AC. The opposite is true. Hot areas are only 25 freedom units hotter than humans prefer. Cold areas have months of 50+ temperature difference. The misconcep…

Is NG really over 5X cheaper than electricity? It seems like a NG genset that is better than 20% efficient wouldn't be that hard to build, yet I don't see people running their houses off of electricity that way.

Re: “Cold Tube” cooling system uses half the energy of an air conditioner

#122

Post by aidenn0 »

aeternum wrote: post #90
thescriptkiddie wrote: post #62

Earlier quoted context omitted.

I was recently shopping for an AC unit and had to get a portable one because I have bars over my windows. Having seen the Technology Connections video I naturally tried to get a dual-hose model, but after seeing the specs (and the prices) I ended up getting a single-hose model anyway. If we go by the DOE SACC ratings, this single-hose toshiba [0] has a 14% higher SACC rating than this dual hose whynter [1], for the s…

The problem with an efficiency rating that includes air ingress is that the outdoor air temperature is an unconstrained variable. The dual hose unit will likely outperform significantly if the temperature delta is high, but if the temp delta is low then the single-hose unit is probably better as it likely has a more efficient compressor. It looks like DOE SACC tests assume the outdoor air temp is 83 degrees for 80% o…

That's funny because I set my AC to 84, and only use it it outdoor temperature is over 86 (I live in a somewhat dry area: typical dewpoints are low-to-mid 60s on hot days).

Re: “Cold Tube” cooling system uses half the energy of an air conditioner

#123

Post by labawi »

taneq wrote: post #115
labawi wrote: post #81

Earlier quoted context omitted.

Thermal radiative coupling is bidirectional. Sucking away is appropriate and important as you do actually have to displace the energy somewhere. It works the same way when sucking air. A simpler non-radiating equivalent would be a reflective foil, or a polished metal - you could enclose yourself within it, get no radiating heat from environment, yet it wouldn't help cool you, because your radiation has no place to go…

> It works the same way when sucking air. This is a good analogy because (being pedantic) you can't suck air either. You can only make a region of lower pressure, into which the higher-pressure air pushes itself.

May I then ask what can you suck, by your definition?

Re: “Cold Tube” cooling system uses half the energy of an air conditioner

#124

Post by hajimemash »

mkl wrote: post #113
heisenzombie wrote: post #45

An idea I was told about relatively recently that kind of blew my mind: - Space is cold (~3K) - The atmosphere is really quite transparent in the wavelegth 8-13 μm - If one can construct an optical filter (e.g. grating) which is highly reflective except for a bandpass at 8-13μm, it is possible to reflect most solar energy but still "see" the cold of deep space - It's possible to build a box with sufficiently low ther…

> [^1] in fact, if you put it in the shade then it would warm up because it could no longer radiate to space. If I understand correctly, this isn't quite right. If it's in the shade, then whatever is shading it is radiating more heat onto it (because the shading object is hotter than space) and possibly reflecting its own radiated heat back. If it's under a clear sky then it's receiving less heat, so what it loses by…

I agree with your description, OP possibly concised his words a little too much as to imply the wrong thing.

Re: “Cold Tube” cooling system uses half the energy of an air conditioner

#125

Post by ac42 »

andor wrote: post #16

Not sure why they are researching the mechanism, these systems are commonly installed in Germany and known as "Kühldecke" (cooling ceiling). https://de.wikipedia.org/wiki/K%C3%BChldecke

The WP article points out the issue of condensation, which the OP claims as being addressed in a novel way.

Re: “Cold Tube” cooling system uses half the energy of an air conditioner

#126

Post by pdonis »

heisenzombie wrote: post #100
pdonis wrote: post #70

Earlier quoted context omitted.

> if we put a blackbody in deep space, would it eventually be cooled/heated to the temperature of the cosmic background radiation? No. As you note, in space in our vicinity there is a hot object, the Sun, in the sky, so the "temperature" of space in our vicinity is not really the 3K of the CMB, because an object placed in space in our vicinity will not come to thermal equilibrium at that temperature, but at some high…

Nice. Seems related to: https://en.wikipedia.org/wiki/Planetary_equilibrium_temperat... The temperature of a perfect black body in earth’s orbit would be ~255K (-18C) (This is not the case for the technology under discussion because it’s very much not a black body) I will point out that even at modest (astronomically speaking) distances, the solid angle of a star gets preeeeetty small. For example, a black body at ju…

> even at modest (astronomically speaking) distances, the solid angle of a star gets preeeeetty small

Yes, but you're not just being irradiated by a single star. There's a whole galaxy of them. They aren't all visible to the naked eye, but they're still there, and their radiation all adds up.

However, I have not done detailed calculations, so I might be overestimating, for example, what the effective radiation temperature would be of galaxies in intergalactic space.

Re: “Cold Tube” cooling system uses half the energy of an air conditioner

#127

Post by pdonis »

Aperocky wrote: post #119
pdonis wrote: post #70

Earlier quoted context omitted.

> if we put a blackbody in deep space, would it eventually be cooled/heated to the temperature of the cosmic background radiation? No. As you note, in space in our vicinity there is a hot object, the Sun, in the sky, so the "temperature" of space in our vicinity is not really the 3K of the CMB, because an object placed in space in our vicinity will not come to thermal equilibrium at that temperature, but at some high…

> In short, an object would come to thermal equilibrium in space at the 3K CMB temperature only if the CMB were the only radiation source in the object's sky. But in actual fact it never will be. I still don't see if this answer my question, assuming CMB is the only source, but the photon density has diminished significantly, would there be enough CMB photons to keep the object from going lower than 3K from emitting…

> assuming CMB is the only source, but the photon density has diminished significantly, would there be enough CMB photons to keep the object from going lower than 3K from emitting blackbody radiation?

Obviously not, since if the photon density has diminished significantly, the temperature of the CMB will diminish significantly too. The temperature of the CMB gets lower as the universe expands. When the CMB was originally emitted, some 300,000 years or so after the Big Bang, its temperature was around 3000K, not 3K. It has cooled to 3K because the universe has expanded by a factor of about 1000. It will continue to cool as the universe expands further.

> Will there ever be a time where there are not enough CMB to heat the blackbody?

Meaning, to heat the black body to the same temperature as the CMB at whatever time you are considering? No. The CMB is unlike all other radiation sources in that it is everywhere, and its effective temperature is the same everywhere. You can't be "at a distance" from the CMB the way you can from a star or a galaxy.

Re: “Cold Tube” cooling system uses half the energy of an air conditioner

#128

Post by kingnothing »

aidenn0 wrote: post #121
eggsnbacon1 wrote: post #13

Earlier quoted context omitted.

New buildings are rather efficient in US. The problem is old buildings that use 5X the energy for HVAC. I echo that AC is quite efficient. Far more efficient than traditional heating. There's a misconception that hot areas are less environmentally friendly due to AC. The opposite is true. Hot areas are only 25 freedom units hotter than humans prefer. Cold areas have months of 50+ temperature difference. The misconcep…

Is NG really over 5X cheaper than electricity? It seems like a NG genset that is better than 20% efficient wouldn't be that hard to build, yet I don't see people running their houses off of electricity that way.

In the US, natural gas averages $11.85 per 1,000 cubic feet. Electric averages $0.13 / kwh.

1,000 cubic feet of natural gas is a bit over 1 million BTU. That converts to 297 kwh of electricity.

that 1,015,000 btu costs:

$38.61 in electric

$11.85 in natural gas

Re: “Cold Tube” cooling system uses half the energy of an air conditioner

#129

Post by pdonis »

heisenzombie wrote: post #100
pdonis wrote: post #70

Earlier quoted context omitted.

> if we put a blackbody in deep space, would it eventually be cooled/heated to the temperature of the cosmic background radiation? No. As you note, in space in our vicinity there is a hot object, the Sun, in the sky, so the "temperature" of space in our vicinity is not really the 3K of the CMB, because an object placed in space in our vicinity will not come to thermal equilibrium at that temperature, but at some high…

Nice. Seems related to: https://en.wikipedia.org/wiki/Planetary_equilibrium_temperat... The temperature of a perfect black body in earth’s orbit would be ~255K (-18C) (This is not the case for the technology under discussion because it’s very much not a black body) I will point out that even at modest (astronomically speaking) distances, the solid angle of a star gets preeeeetty small. For example, a black body at ju…

> The temperature of a perfect black body in earth’s orbit would be ~255K (-18C)

More precisely, of a perfect black body in Earth's orbit with the same surface area and shape as Earth.

Re: “Cold Tube” cooling system uses half the energy of an air conditioner

#130

Post by taneq »

labawi wrote: post #123
taneq wrote: post #115

Earlier quoted context omitted.

> It works the same way when sucking air. This is a good analogy because (being pedantic) you can't suck air either. You can only make a region of lower pressure, into which the higher-pressure air pushes itself.

May I then ask what can you suck, by your definition?

Good question! 'Sucking' here is a bit like 'centrifugal force' - it's a real thing, but only in the right frame of reference.

In the case of centrifugal force, it's a real thing in a rotating reference frame, but doesn't exist in an inertial reference frame (because in that frame the acceleration is towards the center, ie. centripetal).

In the case of suction, it's a real thing when your zero-pressure reference point is above 'absolute zero' pressure, such as when you're measuring gauge pressure. In this case you can have an area of 'negative pressure' which is 'sucking' the surrounding fluid into it.

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