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Fossil-fueled civilization

Zhigang Suo's picture

I'll be teaching an undergraduate course on engineering thermodynamics.  We will use the textbook by Cengel and Boles.  I will supplement the textbook using my own notes on thermodynamics.  Teaching this course will give me an opportunity to revise these notes and add new pieces. Here are notes for the opening lecture.

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Zhigang Suo's picture

Here is the thread of discussion  

Zhigang Suo's picture

Thermodynamics is a visual subject.  Slides, videos, and animations are often more effective than words.  A picture is worth a thousand words.  A movie is worth a thousand pictures.  

Here is an animation of a coal-fired plant.  The function of a coal-fired plant is to turn coal into electricity.  Pay attention to the sequence of events that realize this function.

Dear Zhigang,

1. The animation is nice, but the feed pump is not mentioned saliently into it.

Even if the amount of work done by the feed pump is negligibly small as compared to the work extracted from the turbine, when you include the feed pump explicitly, there arises a nice symmetry of having two heat-exchange devices (boiler and condensor) and two work-exchange devices (feed-pump and boiler).

That helps in establishing the correspondence of a real system with, first, the Rankine cycle, and then also with the Carnot cycle, esp. on the T-s diagram. The T-s diagram can then serve as an intermediary between the visual depiction and the abstract equations. Indeed, on a T-s diagram, students can visually see the effects of boiler pressure, turbine back-pressure, superheating, friction, and in fact, even the reason that the real steam cycle must have a thermal efficiency less than that of the Carnot cycle---and yet, why the idea of Carnot cycle is at all useful.

2. On another point, I am recommending your notes to my students (second year undergraduates of mechanical, for an intro. course on thermo.)

--Ajit

[E&OE]

 

Oops. Please read ``two work exchange devices (feed-pump and turbine)'' in place of ``two work-exchange devices (feed-pump and boiler)''. Sorry about that.

--Ajit

[E&OE]

 

Zhigang Suo's picture

The word energy serves no purpose in this narrative.  What we want is motion and electricity, not energy.  Energy is just one attribute of many.  We also need space, mass and electric charge.  Energy is conserved, so are space, mass and charge.  There is absolute no reason to single energy out.  Most talks about energy are lazy talks.  It is better to describe processes as what they are.  Fire tunrs water into steam, steam rotates a turbine, the turbine rotates a generator, and the generator produces electricity.  Energy simply has no reason to stand out.

In this new write up, I have removed this pesky word energy.  The file is shorter and clearer.  

Dear Zhigang,

Yes, they say that energy is quantized, but what is really quantized is the field, isn't it?

--Ajit

[E&OE]

 

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