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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

#61

Post by Aperocky »

heisenzombie wrote: post #59
Aperocky wrote: post #53

Earlier quoted context omitted.

Space is without temperature. Temperature is an attribute of things, space is a lack of things. What you're referring to is the temperature of cosmic background radiation, which is akin to how you emit infrared radiation at your body temperature. But you certainly don't classify the space where this radiation move through as having your body temperature. The two things are not the same imo.

"Temperature" is a slippery word that has many different definitions depending on what area of physics you're working in. In this case it is perfectly fine to refer to "the temperature of space" since you're explicitly using it as a cold sink. As evidence, see the paper (published in Nature no less!) that MengerSponge posted. The authors say "On the other hand, outer space, at a temperature of 3 K, provides a much co…

Here's something I don't understand though, if we put a blackbody in deep space, would it eventually be cooled/heated to the temperature of the cosmic background radiation?

The space around us is filled with photon coming from Sun at ~5500K, but it doesn't heat anything to anywhere near that. So given the current density of cosmic background radiation at 411 photon cm -3, would it be sufficient to place a blackbody to the equilibrium temperature?

I am not a physicist by training, and this is a genuine question.

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

#62

Post by thescriptkiddie »

userbinator wrote: post #52
dghughes wrote: post #36

Earlier quoted context omitted.

Portable air conditioners are bad. All the hot components are in the room with you and it takes air from the room and blows it outside. Technology Connections has a good video about this: https://youtu.be/_-mBeYC2KGc?t=355

That's true of the ones that have only one hose to the outside. Those with two hoses are much better, especially if you insulate the hoses: https://news.ycombinator.com/item?id=24023979

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 same BTU/hr rating. If we go by the wattage ratings (note: these are usually peak rather than average), the toshiba does use 13% more power than the whynter, so let's assume it cancels out and they both have the same energy efficiency. The toshiba is still $144 cheaper than the whynter. That's hard to justify for "dual hoses seem like they should be more efficient" without any actual evidence.

Please prove me wrong, before it's too late for me to return the single-hose one.

[0] https://www.toshiba-lifestyle.com/us/Room-Air-Conditioners/P...

[1] https://www.whynter.com/product/whynter-elite-12000-btu-dual...

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

#64

Post by londons_explore »

userbinator wrote: post #48
sparker72678 wrote: post #32

Earlier quoted context omitted.

The outdoor fresh air intakes are typically via ERVs (Energy recovery ventilation systems). These systems bring in fresh air, filter it, and typically run it through a heat exchanger to minimize energy losses as the fresh air comes and and the stale air goes out. The purpose is to prevent buildup of harmful gasses and VOCs (everything from CO2 to CO to regular out-gassing of furnitures, etc) that can become dangerous…

It's been my experience that the newer high efficiency buildings seem to be optimising for that rather aggressively to the detriment of breathable air, because the air in them certainly feels a lot stuffier than in the older ones I've been in. I can certainly see building owners setting the recirculation as high as they can get away with, for the lowest cost.

"Stuffy" air is your body detecting CO2. You should totally do something about it.

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

#65

Post by closeparen »

dghughes wrote: post #36
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…

Portable air conditioners are bad. All the hot components are in the room with you and it takes air from the room and blows it outside. Technology Connections has a good video about this: https://youtu.be/_-mBeYC2KGc?t=355

Portable air conditioners are a band-aid for people whose landlords or HOAs prohibit external HVAC components.

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

#66

Post by tripletao »

username505 wrote: post #60
URSpider94 wrote: post #54

Earlier quoted context omitted.

What is false?

The total efficiency of an air conditioner will never be more than 100% based on design; you will never be able to remove more heat than what the system produces in net cooling effect based off of the energy consumption created from compression - this is what would lead you to the eventual path of the theory of the heat death of the universe. You may be able to remove heat from one place to another but never more tha…

The ratio of thermal power moved to electrical power input is more properly called "coefficient of performance" rather than "efficiency", but it's far greater than 100% in modern equipment.

> From 1990 to 2013, U.S. shipment-weighted efficiency for residential split-system A/Cs increased from 9.5 SEER (~2.2 COP) to 14.9 SEER (~3.8 COP).

https://www.energy.gov/sites/prod/files/2016/07/f33/The%20Fu...

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

#67

Post by adrianN »

londons_explore wrote: post #47
sparker72678 wrote: post #32

Earlier quoted context omitted.

The outdoor fresh air intakes are typically via ERVs (Energy recovery ventilation systems). These systems bring in fresh air, filter it, and typically run it through a heat exchanger to minimize energy losses as the fresh air comes and and the stale air goes out. The purpose is to prevent buildup of harmful gasses and VOCs (everything from CO2 to CO to regular out-gassing of furnitures, etc) that can become dangerous…

2020: ”Poisonous stuff in our houses... Bad! Let's vent it to the environment!” 2120: The environment is all full of poisonous gasses from the people of 2020. Each house needs its own air purifier to make the outdoor air safe to breathe.

Luckily most organic compounds you find in indoor air aren't very stable.

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

#68

Post by KMag »

roywiggins wrote: post #26
marcinzm wrote: post #24

Earlier quoted context omitted.

[I was wrong]

Air conditioners are often more than 100% efficient- they move more heat energy than they consume. (Of course if you start with a fossil fuel, turn it into electricity, and then pipe that into an AC unit, the overall efficiency will be dropped by the efficiency of the power plant, but it's still somewhat made up for by the advantages of heat pumps)

As others have pointed out, the coefficient of performance is over 1.0. However, as I remember from my mechanical engineering classes, a single-stage piston compressor based refrigeration system found in most window-mount AC units, refrigerators, etc. typically operates at about half of the Carnot efficiency. Central AC units with scroll compressors do a bit better, and of course industrial chillers with multi-stage centrifugal compressors do quite a bit better.

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

#69

Post by DoofusOfDeath »

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…

> New buildings are rather efficient in US. The problem is old buildings that use 5X the energy for HVAC.

I was describing my home renovation project to someone who lives in Brazil. I don't how true this is for that entire country, but she said that it's very uncommon for Brazilian homes to have insulation.

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

#70

Post by pdonis »

Aperocky wrote: post #61
heisenzombie wrote: post #59

Earlier quoted context omitted.

"Temperature" is a slippery word that has many different definitions depending on what area of physics you're working in. In this case it is perfectly fine to refer to "the temperature of space" since you're explicitly using it as a cold sink. As evidence, see the paper (published in Nature no less!) that MengerSponge posted. The authors say "On the other hand, outer space, at a temperature of 3 K, provides a much co…

Here's something I don't understand though, if we put a blackbody in deep space, would it eventually be cooled/heated to the temperature of the cosmic background radiation? The space around us is filled with photon coming from Sun at ~5500K, but it doesn't heat anything to anywhere near that. So given the current density of cosmic background radiation at 411 photon cm -3, would it be sufficient to place a blackbody t…

> 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 higher temperature. Exactly what higher temperature, if we assume the object itself is a black body, will depend on the object's surface area and its distance from the Sun.

We could, of course, theoretically place an object outside our solar system, or even outside our galaxy, or even outside our local group of galaxies, or even outside the galaxy cluster of which our local group is a part. Doing those things would move the object farther and farther, on average, from high temperature radiation sources like the Sun. But there would still be radiation from those sources in the sky, meaning that the object would still reach thermal equilibrium at some temperature higher than the 3K CMB temperature.

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.

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