Probably a little bit more since it's an imperfect seal. When you do the math doesn't it seem a lot more realistic? I mean look at even the most basic blower's that the industry uses are 50K to 100K cfm (cubic feet per minute).

You should check on those again. Most leaf blowers are less than 300 cfm.

That's the wonderful thing about PVC. Most of them don't melt until well over 300 F (150 C). It would need to be something tested though by an engineer to see if it's a problem. The amount of air moving through the system provides a natural cooling mechanism for the tubes.
[/quote]

You're just going to have hot air, and even hotter plastic. Or are you going to have air conditioning as these packages travel across Arizona in the summer?

[quote name='Sirisian' timestamp='1315610388' post='4859791']
Probably a little bit more since it's an imperfect seal. When you do the math doesn't it seem a lot more realistic? I mean look at even the most basic blower's that the industry uses are 50K to 100K cfm (cubic feet per minute).

You should check on those again. Most leaf blowers are less than 300 cfm.
[/quote]
I said industrial ones. Like this or others I'd imagine. Unless you thought I was talking about small leaf blowers.

It would definitely depend on the links and the size, but the technology is there for as much power as is required. Doing things efficiently would be key.

[quote name='Sirisian' timestamp='1315610388' post='4859791']
That's the wonderful thing about PVC. Most of them don't melt until well over 300 F (150 C). It would need to be something tested though by an engineer to see if it's a problem. The amount of air moving through the system provides a natural cooling mechanism for the tubes.

You're just going to have hot air, and even hotter plastic. Or are you going to have air conditioning as these packages travel across Arizona in the summer?
[/quote]
Cycling in outside/cold air into the system is an option. Are you worried about transporting cold items or just ones that can't get too warm? Would be interesting to build cold capsules for things that need to stay frozen. I could finally ship people blue moon ice cream without resorting to insane methods.

wait this thread is 60 posts long and noone mentioned the movie 'Brazil'! WTF

Cycling in outside/cold air into the system is an option. Are you worried about transporting cold items or just ones that can't get too warm? Would be interesting to build cold capsules for things that need to stay frozen. I could finally ship people blue moon ice cream without resorting to insane methods.

No, I'm talking about preventing the heat from friction from melting your system. You state that it will somehow be air cooled, but that's a lousy way to dissipate heat, especially if you're just using air pumped from outside. You keep dismissing major flaws as if they are trivial.


Please show me these basic 50k to 100k cfm blowers.

wait this thread is 60 posts long and noone mentioned the movie 'Brazil'! WTF

I was going to watch another movie actually today but when I saw this I was like "meh why not". That is a crazy movie on par with Russia's Solaris movie.

But yeah... exactly like that.

[quote name='Sirisian' timestamp='1315612415' post='4859807']
Cycling in outside/cold air into the system is an option. Are you worried about transporting cold items or just ones that can't get too warm? Would be interesting to build cold capsules for things that need to stay frozen. I could finally ship people blue moon ice cream without resorting to insane methods.

No, I'm talking about preventing the heat from friction from melting your system. You state that it will somehow be air cooled, but that's a lousy way to dissipate heat, especially if you're just using air pumped from outside. You keep dismissing major flaws as if they are trivial.[/quote]
oh sorry. I'm not dismissing it. I see what you mean now. You're talking about the heat on the capsule. We calculated before 44 N of force which would be converted into heat. To do that we need distance since work acts over distance W = F * d. Now 44 N * 2905 miles = 2.057×10^8 J of energy. We have to make an assumption that half the heat is put into the PVC tube walls and half goes into the canister. This might be a flawed assumption but that would be 1.029×10^8 J of energy added to the capsule along the whole trip. We're assuming a worse case where no heat is dissipated into the air. Okay we can imagine the surface that the energy is added to as a cube of plastic. Now when we evenly distribute the energy the temperature rises. Reading material. ABS has a specific heat of 1.54 J/g C. If we put all that energy into a 1 cm^3, aka 1.04 grams, of ABS plastic it will rise 1.029×10^8 J / (1.54 J/g C * 1.04 grams) = 64250000 C. Notice if we assume it expands through the whole shell and we calculate that with radius 15 cm and it's 0.5 cm thick with caps 0.5 thick and it's 60 cm long you get 3440 cm^3 and a raise in temperature of the whole canister by: 18677 C. Not bad even without losing any heat energy throughout the whole trip.

Now I know you might think that's a lot of heat energy to build up, but it just means that the system would need dissipate that. The continuous air rushing by might do that. However, if that doesn't help then another way would need to be designed. Again I'm not an engineer so I lack the proper material sciences class to make a clear prediction. (I do have a few physics classes under my belt if you want me to do other calculations).

Please show me these basic 50k to 100k cfm blowers.

Here's one. Can you be more specific though. There are hundreds of them on the Internet. Some go up to 440K cfm. I can't tell if you're skeptical that they exist or that they're basic enough? It's an electric motor connected to a fan so they use electricity. I imagine some run on 3-phase which isn't as basic.

The main goal would be to keep the system as simple as possible. These blowers can be made redundant so the system is fault tolerant. However I think an air-ducted fan system might be magnitudes more efficient. I'm not versed in blowers though. This would need serious engineering work.

You appear to have missed a rather key point: There is, by definition of the design, No Air Passing Over the Capsule. It must bleed all of its heat off into the pipe itself, which must be kept cool.


Also, those aren't 'basic' blowers. Those are expensive industrial blowers that aren't exactly a cheap thing you can easily buy in the tens of thousands.


Try calculating the amount of energy required to just blow air through a pipe that long. I haven't found a single tool that lets me calculate the energy loss due to friction on something that long without rewriting it. And JUST the air, before you add more friction from packets.

To everyone who says it cannot work due to physics - systems like this are already running. They have been for decades.

But!

It is impractical to have them running to each individual house.
Their efficiency is directly proportional to utilization. The case study from Japan shows that a busy system has only 3% fillrate (number of capsules vs. total volume of tube) which is insufficient.
They are not cost effective for light loads, they start at 1 ton.
Actual studies have looked into wear and tear and other aspects.

Some go up to 440K cfm.[/quote]Which doesn't say anything.

Fans come with "fan performance table/curve". Each fan has operational range which is, at basic level a ratio of pressure vs. speed. Type of fan chosen must be matched with load characteristics of actual pipeline so raw numbers don't say anything.

But as examples show, it is doable. Individual issues, such as heat or friction do need to be solved, but they are not impossible. All pipelines today deal with it. There's even a pipeline running in arctic which conducts heat into its supports to keep tundra from freezing and damaging concrete (or something similar).

Pipelines do transport air over long distances. 1000psi, which is managable, notice the pressure drop.

Regarding heat - yes, it is a problem, even with conventional pipelines. But that too can be solved. Turns out, it might not be the heat you will be worried about, but heat loss - the inability to heat the pipe enough to not have temperature deviations because it cools too much. Heat is radiated away from pipe (conducted as well). The ratio between circumference and volume however is r^2 vs. r^3, so insulation cannot keep up at some point. (discussed in various HVAC manuals). The question now becomes, if underground, how would surrounding area act (different terrain and all that).

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But all of that is moot. Issues are quite practical.

Existing infrastructure is poor fit for wide-spread adoption. Digging under cities is prohibitively expensive (see Big Dig). Houses, let alone large and old buildings simply aren't built to offer access to underground tubes for such purpose. And so on...

Nothing says it cannot work. We're saying it cannot be practical to have working compared to systems we already have in place.

I know tubes have been used for freight and such, but never on such a scale. Why? Because it is easier to put it on a truck or train and use transit infrastructure that is flexible in use.

The proposal of such a 'simple' general idea, like PVC tubes and blowers, doesn't work as simply as the poster is suggesting because of physics.