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空调是什么原理?如何选择制冷剂? – 译学馆
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空调是什么原理?如何选择制冷剂?

How Air Conditioning Works

PBS Digital Studios
公共广播公司 数码影像工作室
If you’re feeling the summer heat,
如果你感到了夏暑之热
you might be tempted to switch on the machine that makes
你也许会忍不住想打开
all the problems go away: your air conditioner.
使所有问题烟消云散的设备:你的空调
And the source of that sweet relief?
为什么那样轻松惬意?
Well, of course it’s chemistry.
当然 是化学反应的功劳
Air conditioners pull off the seemingly magical feat of
空调实现了看似神奇的壮举
making the air inside a home, car, or shopping mall deliciously chilly.
住所 汽车 商场里的空气 因它变得凉爽宜人
Air conditioning — and refrigeration, which is the same thing
空调和冰箱是一样的
just in a slightly smaller box
只不过空调的外壳稍微小一点
— rely on the laws of physical chemistry.
这依托于物理化学的定律
And p-chem tells us that
物理化学告诉我们
as a liquid evaporates into a gas, it absorbs heat.
当液体蒸发成气体时要吸收热量
The molecules in a liquid are held together by weak intermolecular interactions.
水分子聚集依靠的是 分子间微弱的作用力
Not quite chemical bonds,
说是化学键呢 又不完全是
just enough passing attraction to keep them from flying apart.
产生的吸引力 只是足够不让分子游离散开而已
Some of the molecules absorb enough heat energy
一些分子吸收了足够多的热能
— in other words, they get moving fast enough
——换句话说 它们运动的足够快
— to overcome these intermolecular attractions, ESCAAAAPE and take gaseous form.
以至于能够克服分子间的吸引力而逃脱 并转化成气态
That’s the reason you feel chilly getting out of the shower
那便是为什么你洗澡后会感觉冷
and why we sweat to stay cool.
以及 为什么汗水能保持身体凉爽
The water has to absorb heat to evaporate.
因为水要吸热才蒸发
And it carries that heat away from you.
所以它从你的身体带走了热量
An air conditioner’s basic job, then,
一台空调的基本工作
is to use a fluid called a refrigerant
就是使用一种叫做制冷剂的液体
that constantly changes from a liquid to a gas and back to a liquid again
制冷剂不断从液体变成气体 而后又再变成液体
to move heat from one place (your sweaty bedroom)
以便 把热量从一个地方 (你热得冒汗的卧室)
to another (outside, where it’s already hot and miserable anyway, so who cares.)
转移到另一个地方(屋外)(反正屋外炎热难受 没人会在意到了哪儿)
Here’s a admittedly very schematic-ified version of how most a/c units work.
这张主要空调元件的工作原理示意图 确实非常简略
The liquid refrigerant flows through a series of coils exposed to the air in your home.
液态制冷剂流经一圈一圈的管道 而这些管道是暴露你家空气中的
The refrigerant has a low boiling point,
制冷剂的沸点很低
so the heat from the interior air is enough to make it turn into a gas.
所以外界空气的热量足够把它转变成气体
Which means there’s now more heat in the refrigerant
这意味着现在制冷剂里有更多的热量
and less in the air.
而空气中热量更少
A fan blows that colder air into your room.
风扇把冷空气吹进你的房间
Or straight into your face, we’re not judging.
或者直接吹到你的脸上也说不准
So now your A/C has to do two things
那么现在你的空调需要完成两件事
: dump the heat absorbed by the refrigerant outside,
一件是将制冷剂吸收的热量排到外面
and two, it has to condense the refrigerant back into a liquid
第二件 必须把制冷剂重新凝结成液体
so it can be used again.
以便再次使用
And to do those things it uses a compressor to ramp up the pressure on the gaseous refrigerant
空调为此使用压缩机增加气态制冷剂的压力
— so much that it can condense into a liquid again,
气态制冷剂 在如此大的气压下 就算外界温度更高
even though it’s at the warmer outside temperature
也能够再次被凝结成液体
As it condenses, the refrigerant loses heat to the air around it, which another fan blows
制冷剂凝结时热量散到周围的空气中 热空气则被另一个风扇吹到了户外
outside, where it’s already all sticky anyway.
反正户外已经完全闷热难受了
Which is a neat trick,
这是一个巧妙的技巧
boiling something at a low temperature and then condensing it at a high one.
将某物在低温下气化 然后在高温下冷凝
Nothing in thermodynamics is free,
在热力学定律中没有什么是可以不付出代价的
and the compressor needs energy to do the work of
压缩机需要能量
compressing the refrigerant.
来完成制冷剂的压缩工作
Which may explain your power bills in July.
这也就能解释你在7月份飞涨的电费账单
After the refrigerant condenses, the air conditioner backs off the pressure with an expansion valve,
制冷剂冷凝后 空调用膨胀阀降低压力
so that the refrigerant can boil at the lower temperature again.
因此制冷剂能够在较低的温度下再次气化
Which it does, in a loop, over and over
它将一直循环这个过程
until your home reaches the temperature you set
直到屋内温度达到设定温度
the thermostat to, or your housemates complain
或者 直到你的舍友向你抱怨温度太低
and switch it off.
关掉空调
While the refrigerant could be practically any substance,
虽然几乎任何东西都可以作为制冷剂
there are some chemicals that do the job better than others,
有一些化学物质更能够胜任这项工作
and these refrigerants have a checkered history.
这些制冷剂的历史一波三折
A refrigerant needs to have a pretty low boiling point, and one that can be adjusted to where
制冷剂需要极其低的沸点
you want it by changing the pressure on it.
要能通过改变其压强 调节到所需的温度
It should also be pretty good at conducting heat,
它还应该具有良好的导热性
be able to absorb a lot of heat as it boils.
能够在气化的时候吸收大量热量
And then it needs to be cheap, widely available, and as non-flammable
另外 它需要便宜 很容易获得
and non-toxic as possible.
尽量不易燃和无毒
That kinda narrows your choices of chemical.
那使能做制冷剂的化学物质受到了限制
Scientists thought they’d found
科学家相信他们已经找到了
the perfect refrigerant with Freon,
一种完美的制冷剂——氟利昂
which is the trade name a group of chemicals called chlorofluorocarbons.
一组称为氯氟烃的化学品的商品名
But CFCs are actual murder to the ozone layer.
但是氯氟烃实际是破坏臭氧层的罪魁祸首
They’ve been largely replaced with hydrofluorocarbons, or HFCs.
它们已大多被氢氟烃 即HFCs取代
HFCs don’t damage the ozone layer, which is good!
HFCs不会破坏臭氧层 这很棒
But they have a different problem…they’re greenhouse gases.
但是他们有其他的问题 他们是温室气体
So the search is on to phase out HFCs too.
因此 为了逐步淘汰HFCs 人们又在继续寻找
Some alternatives?
还有其他的替代品吗?
Simple hydrocarbons like these have been approved in the USA.
像这些简单的碳氢化合物在美国是受批准的
Hydrofluoroolefins like this one are less rough on the climate than HFCs,
氢氟西烃对气候的影响比HFCs小
but also more expensive.
但也更加昂贵
The most surprising potential replacement is CO2.
最令人吃惊的潜在替代品是二氧化碳
CO2 totally works as a refrigerant, and even though
二氧化碳完全可以用作制冷剂
it is the literal poster child for greenhouse gases,
尽管它实际上是典型的温室气体
it’s also way less potent than HFCs.
但其影响远不及氢氟碳化物
Whatever we use in the future, it doesn’t seem likely that
不论我们在将来使用什么
we’ll give up on AC altogether.
看起来我们都不会放弃对空调的依赖
Not in a scorching summer like this one.
尤其不会在这样一个炎热的夏天
Pass the popsicles, wouldja?
请把冰棒递过来 好吗
Thanks for watching,
感谢观看
and if you want to help us keep making great videos like this one,
如果你想帮助我们继续产出像这样的优秀视频
remember to subscribe, turn on notifications, share this video,
记得订阅 打开通知 分享这个视频
and brag at your next cocktail party that
你下次鸡尾酒会炫耀说 自己对
you know all about the machine that’s keeping everyone from sweating their eyes out.
避免出汗的机器了如指掌 会蛮吸引人眼球的
We’re…pretty sure y’all go to cocktail parties.
额 我们还挺确定你们都会参加鸡尾酒派对的
We’ll see you next week.
我们下周见

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空调是什么原理?如何选择制冷剂?本期视频将为您揭晓

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