Name: 液態氦氣和派對氣球 - 視頻週期表 (Liquid Helium and Party Balloons - Periodic Table of Videos)
Uploaded: 2021-01-14T10:33:22.000Z
Duration: 11 min 44 s
Description: 【看影片學英語】數萬部 YouTube 影片，搭配英漢字典即點即查，輕鬆掌握單字發音與用法，長久累積看電影不必再看字幕。

scientists Comm parted Justus well as everybody else.

People can party in other ways without holding up scientific research.

Last Sunday in the newspapers, there was a story about helium running sort.

Helium is really important for all sorts of scientific experiments like the Large Hadron Collider on.

The reason it's running short is because everybody is filling their party balloons and there isn't enough being left for doing science.

It's really strange that one could run short of helium because it's the second most abundant element in the universe there unimaginable masses of helium.

But the problem is that there's not very much helium on Earth because helium atoms are very light, far lighter than the molecules of air.

And once they're in the atmosphere, they defuse up to the edge of the atmosphere and out into space, and gravity is not strong enough to keep them here.

This'd balloon helium helium is very small gas.

We use in this case to find leaks in high pressure and Hiram Vacuum Apparatus, because it's very, very small, finds the smallest, smallest holes.

The helium that we have on Earth has come from the decay of radioactive elements deep in the earth, and it's found in some deposits of natural gas.

And until recently, helium has been separated from that natural gas and stockpiled about 20 years ago.

In the early 19 nineties, America, which had been stockpiling helium since the 19 twenties, started to sell off the stockpiles.

So the price went right down and it became very cheap to fill balloons.

And at the same time people started making balloons out of this Met Alec metalized plastic this off silver balloons that you see everywhere, which hold the helium for a long time so you can sell them in shops in a rubber balloon.

The helium comes out so quickly that nobody wants to buy them, and the result is that we're just wasting this.

Helium helium is important scientifically as liquid helium, which boils at four degrees absolute.

That's minus 269 center grained and is one of the best coolants and is particularly important for cooling so called superconducting magnets.

Those that he used for magnetic resonance imaging machines that's used in the labs Han Drum colliders.

And it's also very important for cooling scientific samples.

If you want to do low temperature measurements, as part of my doctorate.

I used liquid helium occasionally, and I had special machine that could make the helium in my experiment, and today I went down to the stores to fetch it.

So what happens here is that this part is a thermos flask, which you can fill with liquid nitrogen to low temperature.

And then there's a fine tube going down here, which takes high pressure helium and allows it to come out through a nozzle so it comes out of the nozzle and expands.

When it expands through this nozzle, it undergoes what is called drill trumps and cooling, and it cools and liquefies.

When I use this appointment, it consumed huge amounts of helium, which was really expensive on.

Once the guests have gone through here, it was just blown out into the atmosphere and wasted.

But I did perhaps altogether half a dozen experiments, which were really important to my work, but normally I used hydrogen, which had a higher temperature, but with much cheaper.

Nowadays, at this university, people don't blow off helium when they're using to cool it, but instead we have pipes going from the labs to a central liquid fire so we can circulate the helium round and round, so it's not wasted.

So now I'm going to take you toe, have a look at the liquid fire and see how it's done.

I've never been there before, so it's really quite exciting.

The entrance looks quite unexciting, but just wait, So this is probably the largest thermos flask you've ever seen.

Certainly the largest one I've seen on this is where the liquid helium is stored.

That's nearly $20,000 worth of helium if you wanted to buy it.

So all the labs that use liquid helium around the campus are connected to this building by plastic pipes, and you can see them coming in here on Dhe.

Each pipe has the gas meter on it so that you can measure the amount of gas coming back.

Now that's very important, because the people doing the experiment get money for returning the gas.

And if they didn't get that money, they would just waste it on.

It goes into that big balloon on this balloon is really big.

You can see hundreds of cubic feet on DDE that amount of GUS will make.

Really, it's tiny amount of liquid enough to fill the volume.

About 16 bottles of this size, about 12 litres off liquids.

That balloon doesn't hold nearly enough gas in order to run the liquid fire.

So we're now in the compressor room where they're to compresses here, which compressed the gas from the balloon so that it can be stored more efficiently.

And so now, once the gas is compressed, it descent into some storage tanks and those storage tanks, A really quite impressive that I have to be quite thin to get there, and these are the tanks, and you can see they're huge.

These tanks contain the impure helium that's come from people's experiments because they always get a bit of air and that sort of stuff into the helium, not very much, but that would be enough completely to ruin the liquid fire.

Because of the very low temperature, the air would freeze and block everything up.

Then, at the second stage, this impure gas goes to the liquid fire which part of which can purify the gas and then pump it into this tank here, which holds highly purified helium when this tank is full toe.

Not a terribly high pressure, perhaps 11 atmospheres, then its sensors.

It's pressure gauges sense a message to the liquid fire that we're ready to liquefy the gas so the guests, when it leaves the white tank, goes into another compressor, which is a clean compressor, which is back in the same room here.

The clean helium compressor is inside this box, so you can't see it, and it's meant to make a terrible noise.

But fortunately, it's not on at the moment.

On this box uses more electricity than any other piece of equipment on the whole of our university campus.

So uses an eighth of a mega watt of electricity when it is running.

So it is a very powerful machine, and the reason it needs to is because helium is quite hard to compress.

So once the gas has bean compressed highly pure, it comes back here to the liquid fire.

On this liquid fire uses Jule Thompson expansion, just like the instrument that I showed you on the desk in my office on dhe.

This comm produce 40 liters of liquid helium each hour, so that's quite a serious amount, so it can produce if you like.

Three Balloon Worths for Patsy Nearly four balloon worths of gas could be liquefied in an hour on all the liquid is then stored in this tank.

And when the scientists are ready to use the liquid helium, it is transshipped into one of these smaller doers, which is then taken back to the department's chemistry.

That magnetic resonance imaging center or the physics department and the whole cycle begins again.

The helium goes into the equipment, and it then boiled back through the pipes and into the balloon.

So when the system is working really well, 95% of the gas is recycled.

I'm going to be shown liquid helium coming out of the tank.

So here's the liquid coming out, and it's immediately vapor rising.

If I breathe it in, my voice may go a little higher, but way mustn't waste too much because he will go into the atmosphere and be lost.

Interrupt a space by far the largest assembly of superconducting magnets in the world is at the Large Hadron Collider, where these magnets are all around.

The 27 kilometer long tunnel and Brady went there a few weeks ago, and he showed me photos of huge tanks of liquid helium that they have the Large Hadron Collider.

Also, there may be hiccups in supply in this article.

It describes some really quite expensive equipment, which, because of shortage of helium, isn't running on a number of days on because they have all the staff and everything else.

This is really quite a waste of money on dhe.

One wouldn't mind if the helium was being used for really sensible reason.

But if it's just big news for parting, people can party in other ways without holding up scientific research and particularly without endangering the measurements of M.

I scans, which he used in hospitals for all sorts of medical treatments.

But surely scientists don't wanna be seen as party poopers.

Scientists comm parted Justus well as everybody else.

Very like to make fun But you can fill balloons with hydrogen, then they explode.

 So if you smoke so I would suggest that you can still have a really good time without helium balloons at the party. 