And on this side, we're going to write out an engine, and we're going to say this is a Carnot engine.
在这边,我们画出一个热机,是卡诺热机。
So, what I want to do is make a new engine which really just consists of two engines, side by side.
我们先构造一个,由两个热机组成的热机,并排排列。
So, the total work that we can get out must be zero, out of the whole sum of them.
因此,我们可以从这两个热机,得到的总功,一定是零。
So, the engine that I'm going to illustrate is called a Carnot engine.
这个热机,叫做卡诺热机。
Now I want to just assume that in some way they're different.
现在我们假设,这两个热机在某些方面是不同的。
That's the work that the system is doing to the environment. I'm doing work to the environment. The work is negative, which means that work is being done to the environment.
功的大小,就是矩形的面积,这样我们就实现了一台热机,冷却,加热,加热,冷却,系统回到了初态。
So what this says is the efficiency of any reversible engine T1 has to be one minus T2 over T1.
这就是说,任何可逆热机的效率都是,负T2除以。
One is our Carnot engine as we've seen it, and the other is just any other reversible engine.
一个是我们已经学过的卡诺热机,另一个是任何一个其它可逆热机。
After all, we're taking the output work that we get from the right, and using it all to drive the left.
毕竟,我们利用,右边产生的功,来驱动左边的热机。
So now let's look at the efficiency of our irreversible engine.
再来看看,不可逆热机的效率。
So in other words, this engine is running less efficiently than my Carnot engine.
也就是说,这个热机的效率,比卡诺热机低。
We could, write the work that we generate -w that comes out as negative w.
的热机相连,热机运行做功。
So this is some other engine that runs using reversible processes.
这是另一台,利用可逆过程工作的热机。
OK, so here is just an engine like what we've already seen, and I'm going to specify that this is a Carnot engine which is to say all the results that we just derived hold for this case.
这一个热机,跟我们以前见过的差不多,我们把它确定为,卡诺热机,所以我们之前得到的结果都对它适用。
Let's just take our reversible engine and modify it a little bit.
我们就拿可逆热机为研究对象,并对它进行一点修改。
We've formulated one particular kind of engine, and seen how we can analyze what it does, come up with relations that seem of value for efficiency and other quantities.
这是一个很典型的热机,我们来分析它是怎么工作的,然后得到效率和其它一些,有用物理量之间的关系。
It's not a result that's specific to the one cycle that we put up.
这不是某一个,特定热机的结果。
As we expected, it's less than one, and of course if we build an engine, we want it to be as high as possible, as close to one as possible.
就像预先期待的一样,效率小于一,当然如果我们建造一台热机,我们希望效率越高越好,尽可能接近一。
Remember this one's running backward, we're pumping heat up.
请记住这个热机是反过来运行的,我们把热量向上传输。
In a real engine, of course, you can approach the reversible limit.
在一个真实的热机里,当然,你可以达到可逆极限。
So generalize our Carnot engine results.
让我们推广卡诺热机的结果。
What you've built is an engine. You cool, you heat, you heat, you cool, you get back to the same place, but you've just done work to the environment.
这就是热机,我们用燃料或者热源加热,然后把它,与大气接触让它冷却。
We're building up to entropy and to engines, Carnot cycles, etcetera.
我们要研究,熵,热机,卡洛循环等概念。
And side by side, we're going to run another engine.
与它并列的,有另一台热机。
So it's going to be the case for any irreversible engine.
这对所有不可逆热机都成立。
So use work out of right-hand side to run left-hand backward.
利用右边输出的功,来驱动左边的热机反方向运行。
And you know, you could have a reversible engine with lots and lots of steps, but you could always break them down into some sequence of adiabatic and isothermal steps.
你们知道,我们可以设计一个由,很多很多个,循环步骤的热机,但是总可以把它分割成,一系列的绝热,和等温过程。
So you know, what the second law is doing, in other words, it's putting these restrictions on how well or how effectively we can convert heat into work in the case of the engine, or work into heat extracted in the case of a refrigerator.
你们知道,在热机中,热力学第二定律的作用,换句话说,就是给热量,转化为功的效率,施加限制,或在制冷剂中,对抽取热量,进行限制。
Now what I want to do is put up a specific example of the cycle that can be undertaken inside here in an engine, and we can just calculate from what you've already seen of thermodynamics.
现在我想做的是,举一个例子,来具体说明热机内部的循环过程,同时我们可以利用热力学定律进行计算,看看热力学参量发生了什么变化。
we can run the engine backward and build a refrigerator, if you've got your lecture notes from last period your 8-9, well, they're labeled 8-9 lecture notes, I made an attempt to define something which was a little bit misguided.
现在我们可以把热机倒过来,制作一台制冷机,如果你们拿出上节课的笔记,也就是8-9节,好的,他们在8-9节,当时我试着,定义了一些,有些误导你们的物理量。
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