Now for this experiment, this is a constant enthalpy experiment for the Joule-Thomson experiment, this is equal to zero.
对于这个实验,焦耳-汤姆逊实验,是一个焓不变的实验,焓变化等于0,所以我可以。
But it's a good story, Joule decided that there must be a direct relationship between work and heat.
所以说,这只是一个不错的故事而已,焦耳认为功和热之间,一定具有某种直接的联系。
A joule is a kilogram meter squared per second squared.
一个焦耳等于,一千克乘以米的平方除以秒的平方。
What is the energy unit in SI? The joule.
国际单位制中的能量单位是什么,焦耳。
The relationship between heat and work was initially proposed in the 1940's by Joule.
热量和功的关系首先是,由焦耳在1940年提出的。
Real refrigerators actually work with liquids that go into gases so use the latent heat of the liquid, so it doesn't really work like the Joule-Thomson expansion. So this is real.
液体变成气体来工作,以运用液体的潜热,所以这不是,真正像焦耳-汤姆逊膨胀一样工作,这是真实的气体,不像焦耳。
It turns out that this quantity here, which is called eta of J the Joule free expansion parameter, is not quite zero.
这个量后来被,称作焦耳膨胀系数,其实并不等于零。
It's constant pressure. OK, so now, last time you looked at the Joule expansion to teach you how to relate derivatives like du/dV.
这是恒压的,好,上节课你们,学习了焦耳定律,以及怎样进行导数间的变换。
What we've been talking about, the Joule-Thomson experiment, constant enthalpy process?
首先,刚才说的,那些有什么问题吗?,焦耳-汤姆逊实验,等焓过程?
And if that's equal to zero, that means that the Joule-Thomson coefficient for an ideal gas is also equal to zero. We're going to actually prove this later in the course.
说明理想气体的,焦耳-汤姆逊系数也等于0。,详细的证明过程,会在以后的课上给出。
Joule actually did this experiment, and he observed that for the gas expansions that he could do, that the temperature did not increase measurably.
事实上焦耳的确做了这个实验,他做到了,他能达到的最好实验要求,发现在可测量范围内没有观察到温度上升。
Well, it's going to be an experiment, very much like the Joule experiment.
同一些实物联系起来?,这就需要一个实验。
This one turns out to be the heat capacity, and this one turns out to be something that we measure in the Joule-free expansion.
其实,这就是热容,这是焦耳自由膨胀实验中,我们要测量的物理量。
OK, so we ended up last time, we talked about Joule-Thomson expansion, which is an irreversible expansion through a nozzle, through a porous plug, constant enthalpy expansion.
上节课,我们讨论了焦耳-汤姆逊,膨胀过程,也就是气体,通过毛细管。
The Joule-Thomson experiment is irreversible.
实验是一个不可逆过程。
What happened to the temperature in a Joule expansion in ideal gas?
对理想气体,焦耳-汤姆逊膨胀过程中温度如何变化?
The Joule-Thomson coefficient is equal to zero.
焦耳-汤姆逊系数等于。
I want to cool a gas with a Joule-Thomson experiment, what temperature do I have to be at?
给气体降温时,需要到达什么温度?
Now, there are two stories about Joule and how he came to this insight.
现在关于他如何得到这个想法的,有两种不同的说法。
And we saw that, you saw that the Joule coefficient for an ideal gas was zero.
我们会发现,你们也会发现,理想气体的焦耳系数是零。
it's kind of like the Joule expansion, an ideal gas.
焦耳-汤姆逊膨胀过程相似。
This is equal to zero. So this irreversible process this Joule-Thomson process, is a constant enthalpy process. Delta h for this process is equal to zero.
等于0。所以这个不可逆过程,也就是焦耳-汤姆逊过程,是一个等焓过程。
Ordinary heat capacities are in Joule's per Kelvin mole, not kilojoules, right.
一般热容的单位是焦耳每摩,而不是千焦。
So the Joule free expansion involves opening this valve and asking what happens when this gas moves into the other bulb or distributes between the two.
焦耳自由膨胀就是,打开阀门后的过程,气体从一个腔跑到另一个腔,并在它们之间平均分配。
OK, the Joule-Thomson experiment.
焦耳-汤姆逊实验。
That's our Joule - Thompson expansion.
这就是我们的焦耳-托马斯膨胀。
v du/dV under constant temperature. du/dT v under constant volume. You use the Joule expansion to find these quantities.
像偏u偏v,恒温下的偏u偏,恒容下的偏u偏,你们知道怎么运用焦耳定律。
We use a liquid helium. And so in order to make a liquid helium, you can't take helium at room temperature and do this, because if you did, you would just heat it up, because the room temperature is above the inversion temperature, so Joule-Thomson would heat up the helium.
为了得到液氦,不能再常温,做这个实验,否则就是加热氦气,因为室温高于它的转变温度,所以焦耳-汤姆孙,实验会加热氦气。
This is real, unlike the Joule coefficient which is very small so that most gases have tiny Joule coefficients. So if you do a Joule experiment, you hardly measure a temperature change. With real gases, here you do actually measure it. You can feel it with your finger on your bicycle tire.
系数那样小以至于,大多数气体的焦耳系数,都很小,所以如果你做焦耳实验,很难测量出温度的变化,对于真实气体,你可以测量它,你能通过手指按在,自行车轮胎上来感觉到它。
The Joule experiment was a constant energy experiment, right. Here we're going to have to find a constant enthalpy experiment, and that is going to be the Joule-Thomson experiment. That's going to extract out a physical meaning to this derivative here.
非常像焦耳实验,焦耳实验是一个能量恒定的实验,我们这里要做的是,找到一个焓不变的实验,也就是焦耳-汤姆逊实验,这个实验可以把这里的微分式形象化。
应用推荐