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it becomes a gray area but it should be pretty clear if you can treat something is reversible are irreversible.
这是个灰色区域,但什么可以当作可逆过程处理,而什么要当作不可逆过程,这是相当清楚的。
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Anybody have any questions on that, because when we voted, the majority of the class thought it was reversible Yes.
上节课我们投票时，多数人都认为它是一个可逆过程，而现在大家应该都知道了,它其实是不可逆过程，有问题吗？
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Instead of this reversible isothermal step, Let's make it an irreversible isothermal step.
不是可逆等温过程，而是不可逆等温过程。
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get back to the initial point is going to require some input from outside, like heat or extra work or extra heat or something because you've done an irreversible process.
如果要逆转它,回到初始点，就需要外界的投入，比如额外的功，额外的热量等等,因为你进行了一个不可逆过程。
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And all we know about this is that it's really for some irreversible reversible step.
我们知道,这个式子,对不可逆过程成立。
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Because if it's irreversible, it's very likely that I don't know what the pressure inside the system is doing while this is happening.
因为对不可逆过程，系统内部的压强,没有明确的定义,气体不处于平衡态。
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Now, if we go back to our Carnot cycle which is a set of reversible paths, it's useful to compare this to what happens in an irreversible case.
如果回到卡诺循环,它是由一系列可逆过程组成，我们将它,和不可逆过程的情况相比较。
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And I want to make sure everybody figured out that it really was an irreversible expansion.
或者多孔塞的,不可逆的等焓过程。
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that instead of all the steps being reversible, let's just put in one irreversible step.
不是所有的过程都是可逆的，其中有一个过程不可逆。
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So w, the work is less for the irreversible process than the reversible process.
不可逆过程中系统对外界,做的功要比可逆过程时小。
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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。
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we're going to have a difference here between the irreversible case and the reversible one.
可逆过程,和不可逆过程,会有不同。
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So for an irreversible process, I wouldn't really be allowed to put a path there.
不可逆过程，是无法画出路径曲线来的。
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If it was non-reversible, I would be allowed to put an initial point and a final point, but I wouldn't be allowed to put a path between them like this, connecting them together.
如果是不可逆过程，我可以画出过程的初态点,和末态点，但是我不能再像这样,画出连接这两个点的，路径曲线来。
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Wirr Minus w irreversible, this is the work which is done to the environment by the system, -Wrev minus w irreversible is always smaller than minus w reversible.
一点提示，不可逆过程中系统,对外界做的功，总是小于,之前我们。
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The temperature is not going to cool as much for the irreversible process.
对不可逆过程,降温不会有可逆过程多。
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So it's that the irreversible efficiency is lower than the reversible one.
所以不可逆过程的效率,小于可逆过程的效率。
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The Joule-Thomson experiment is irreversible.
实验是一个不可逆过程。
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du But if it's not reversible, it's not du.
但如果这不是可逆过程，它不等于。
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T2 STUDENT: From T2 reversible is greater than T2 irreversible, saying that T2 reversible is .
学生：可逆过程的,比不可逆过程的T2更高，也就是可逆过程的T2更热。
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We're going to also look at the irreversible case briefly.
以后我们会简单地讲下不可逆过程。
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But now, so this is where the refrigeration comes in. So if you take a gas, and you're below the inversion temperature and you make it go through this irreversible process, the gas comes out colder from that side than that side.
这就是冰箱的原理,如果在低于转变温度,的情况下我们将气体经过,这个不可逆过程,气体出来的温度将比这边低。
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It's about a tie, and everybody else doesn't now.
这是一个不可逆过程？
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So this is an irreversible process.
所以这是一个不可逆过程，焦耳-汤姆逊。
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It's an irreversible expansion.
这里的膨胀过程是不可逆的。
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This is an irreversible process.
可逆过程中才成立，而这是个不可逆过程。
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If I look at different points in my container during that path, I'm going to have to use a different value of pressure or different value of temperature That's not an equilibrium state, and that process turns out then to be an irreversible process.
如果我要研究在路径中容器里的,不同的点，我就得在容器里不同的点上使用,不同的压强值,或不同的温度值,实际上这不是个平衡态，这个过程是,不可逆过程。
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There's less work done to the outside.
于是对不可逆过程。
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And for the spontaneous change which happens irreversibly That means that'll be dq irreversible.
对于不可逆的自发过程,这说明dq是不可逆的,当过程是可逆时。
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And I compare T2 irreversible T2 They're both less than T1.
我们要比较不可逆过程的,与可逆过程的T2，to，T2，reversible。,显然它们都比T1要小。
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