5
votes
Easily compute a good approximation of heat conductivity of cooled semi-vacuum (water vapor + air)
In the molecular flow region of pressure, the thermal conductivity of an ideal, monatomic gas is obtained by this equation.
$$
k = \frac{1}{\pi^{3/2} d^2}\sqrt{k_B^3T/m}
$$
where $d$ is the ...
- 2,991
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votes
Could a vacuum tank ever be light enough to be boyant in air?
Start out by doing some basic calculations. Air is mostly N2, with a atomic mass of 28, and O2, with a atomic mass of 32. There is more nitrogen than oxygen, so let's say air has a average atomic ...
- 11.5k
5
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How to design a vacuum climbing robot
You do not need full vacuum to accomplish your goal. A small amount of vacuum pressure adds up really quick over a large surface area. Try to make the entire footprint of your robot under vacuum; your ...
- 8,285
4
votes
Unsticking two glass elements fused by vacuum
Perhaps, depending on the materials, you could try gently heating one piece while cooling (or at least heat-sinking) the other piece, and hoping that the expansion mismatch will separate them.
You ...
- 4,259
4
votes
Accepted
deep vacuum in the 19th century
Geissler invented the so-called "liquid piston" pump using mercury for the piston. The basic idea of the design is to entrap some of the air between two volumes of mercury in a pipe, and then force ...
- 12.6k
4
votes
What is the equivalent of a capacitor in pneumatics?
The equivalent of a capacitor in terms of pneumatics would be a chamber such as a metal sphere the size of a tennis ball. It would be necessary to have an external vacuum pump to evacuate the air ...
- 7,307
3
votes
How to design a vacuum climbing robot
An important point in the fluid dynamics design is about control points. A simple experiment - hold your hand over a hose on the vacuum cleaner, you'll notice a light vacuum pulling on it, but hold ...
- 5,333
3
votes
Inlet/outlet of a fridge compressor
The small tube I believe is for the freezer coil, or it could be a capillary tube (thank you Swift). Regardless, simply solder it shut and use the two larger lines for pumping.
I would like to note, ...
- 726
3
votes
How to backfill vacuum chamber with low pressure gas
The simplest way to do this would be to design your own.
A commercially available spring, with an OD of 9mm, a length of 19mm, and a wire dia. of 1mm has a rate of 3.15 N/mm, with 11.5 mm compression ...
- 5,333
3
votes
Accepted
What is the equivalent of a capacitor in pneumatics?
The device is called a "receiver" in pneumatics - this is basically the tank you see on any garage compressor, or much larger and more elaborate setups in industrial settings. Its function can be ...
- 146
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votes
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Are vacuum actuated artificial muscles as hard to control as the pneumatic ones?
With a vacuum you are limited to the pressure differential between zero and atmospheric (~100kPa or ~15PSI). With pneumatic you are limited to the pressure differential between atmospheric and ...
- 5,629
2
votes
What type of positive displacement pump is used for vacuum liquid extraction?
Condensors in steam plant are a common application - about 90% vacuum and you have to extract the condensate at the rate the engine is using steam - something like 9 lbs per hp/hour if you'll excuse ...
- 1,630
2
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How to protect a pressure gauge from condensation in a vacuum steam boiler?
Have you tried a gauge guard? It's a simple diaphragm that allows pressure to transmit, without the liquid crossing the barrier.
- 5,333
2
votes
Vacuum vessel at 10mbar with a diaphragm pump: do I need a venting valve?
I am not a vacuum expert, but if you look at the technical data for your pump, you'll find this "Leak rate 6x10-3 Pa m³/s". I take this to mean that your 10 liter = 0.01 m$^3$ vessel will leak at a ...
- 2,676
2
votes
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What's the difference between a vacuum regulator and pressure regulator?
The difference is the side on which pressure is regulated, and the reaction curve.
Typical pressure regulator takes arbitrary input pressure (from compressor) and provides specified (lower) pressure ...
- 6,115
2
votes
How fast could a Mini Cooper go in a vacuum?
In an atmosphere, the top speed is probably limited by air resistance more than anything, but in a vacuum it would be limited by other factors. Rolling resistance is a major effect that would ...
2
votes
Does a pump like this exist?
I've owned a hand-held pistol-type vacuum pump, useful for testing distributor advance (yeah, long time ago). A quick search shows the inexpensive versions are capable of 0.6-0.7 atm, not quite what ...
- 7,307
2
votes
Can I use a NPT fastened device to vacuum or 10^-2 Torr?
Are you going to continue pumping or have intermittent pumping ? As a engineering professor of sealing once told me "everything leaks, it is a matter of how much". Without continued pumping you will ...
- 6,182
2
votes
Accepted
Need help identifying this vacuum chamber flange
I have some experience with high vacuum so thought I put in my two cents along with what I was able to find on this particular flange. My first inclination was this is a custom unit and I have since ...
- 726
2
votes
Diffusion Pump Copper Cooling Coil Repair
Do this: set up the water flow plumbing with the pump OFF, turn on the water flow, and measure the flow rate by running the discharge into a bucket of known volume for a known period of time, and ...
- 15.3k
2
votes
Accepted
Is it possible/practical to mold a single hollow piece of carbon fiber with a sealed vacuum in the middle?
If I understand correctly, it sounds like you want to make a short carbon fiber tube. This can be done by wrapping the carbon fiber cloth around a mandrel that has the diameter that you want the ...
2
votes
Is it possible/practical to mold a single hollow piece of carbon fiber with a sealed vacuum in the middle?
As far as I know, you can't mold a sphere or cylinder unless the material is on the outside of the mold and you keep the mold in place. Think paper machee over balloons.
There is no way to get the ...
- 7,148
2
votes
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Vacuum Pump Specs
Evacuating 10 psi of pressure from a 500 cu ft chamber in under a second is pretty insane. This is a good calculator, as you will probably need to change your parameters (most likely time) in order to ...
- 2,357
2
votes
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What kind of solenoid valve should I use for vacuum?
A pilot operated valve (often unfortunately generalized as a "solenoid valve") uses a small control solenoid valve and the pressure differential across the valve to open a diaphragm that ...
- 8,285
2
votes
Reverse Suspension Spring
The problems with the vacuum would be that
the resulting force would always be less than 1bar times the cross-section.
In a typical dampener the pressure of the N2 (or compressed air) is a few bars, ...
- 24.3k
2
votes
How do vacuum sealers work on a glass jar?
Not checked out the video, but if you put a jar with a liftable lid in a vacuum sealer then as the pressure outside the jar is reduced air in the jar will push past the seal to equalize the pressure.
...
- 16k
2
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How do vacuum sealers work on a glass jar?
What they are doing in the video is heating up the liquid inside the vessel, (with an open lid).
Then they take it out and immediately (i.e. before it cools down), they pack the lid.
What happens is ...
- 24.3k
2
votes
What is the maximum vacuum level achievable from heating up a metal in a vacuum chamber full of oxygen?
(The device concept you're describing is called a getter.)
The thermodynamic aspect is addressed in Ellingham diagrams:
You place a straightedge on point "O" (for oxygen) and on the ...
- 1,620
2
votes
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Is It Possible To Calculate The Internal Pressure Which A Sealed Glass Vessel Can Support, By Creating A Relative Vacuum Outside The Vessel?
The lowest pressure you can get is zero absolute. Air pressure is about 15psi absolute. The greatest difference you can get across the glass with a vacuum is then only 15psi.
If you want to test your ...
- 530
2
votes
Accepted
Will soft copper pipe deform under vacuum
From the perspective of the pipe, it's pressurized with the difference between external and internal pressure. So if your pipe is pressurized to 1 ATM relative to the room then it'll be pressurized ...
- 2,767
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