Tuesday, July 3, 2012

On the topic of diesel.

     So imaginary readers, did you read about Mariotte's Bottle?  Or maybe his law?  You know the one.  The one called Boyle's Law.
    That coffee maker I talked about is an example of the bottle, which in turn is an application of Boyle-Mariotte's law.   It always brings me a little bit of happiness to see some sort of physics principle play out in the real world.  Just one of those "AH-HA!" moments when you see it.  Or you could take chemistry.  Problem with that is, I can't drink the stuff in chemistry.
     The coffee maker got my curiosity working and I hit the pile of physics essays I've been accumulating.  In Rudolf Claussius work he mentioned Mariotte's law.  So, I've come to give you a small rundown.
     The Volume of gas is inversely proportional to the Pressure of the gas.
     Claussius explains it with a container that change it's size.  If this container was filled with a gas, and  then the container shrunk with the gas inside, then the pressure would increase.  Later, it was explained that molecules are the reason for this.  The gas would still have the same number of molecules, but would be in a smaller area.  Being a gas, the molecules are active and would hit the sides of the container more, exerting pressure on the container.
     This law applies to imaginary gases.  The law calls for the application of a constant temperature.  Here's the thing though, as the pressure increases, so does the heat.  As stated before, as the volume decreases, the activity of the molecules also increases.  Pressure is an energy, and energy changes to become other energy.  In this case it becomes heat.  What I'm saying is, if you change the volume, you change the temperature.
     The most perfect example of this I can think of is diesel engines.  They are an application of this principle.  Gas is released on the downward stroke of the piston.    As the piston comes back up, it compresses the gas, and increasing the pressure.  The gas heats up until it explodes, driving the piston back down.  And as the piston rises again, the exhaust is released from the cylinder.
     All the thermodynamic math is based on statistics.  Energy is observed when it's at a steady state, but we need to know what goes on between states.  Of course, statistics is one of the many classes I took in school that caused me to become disillusioned with math.  And I'm finding that it is applicable to something.
     I've really jumped right into the middle of this thermodynamics thing.  To make myself feel a little better, I'm going to rehash the three laws of thermodynamics, according to C.P. Snow; can't win, can't break even, and can't leave the game.  It makes it easier to remember them that way.  You can not conjure up energy from nothing, it converts to other energy.  You can not return to a previous energy state due to entropy.  And absolute zero is unattainable.
     I might talk about that later. For now, I want to discuss the Carnot Cycle.
     I wish I discovered this cycle earlier.  Last winter I was designing a project in my spare time and this would have helped.  One of Carnot's contributions to physics was the equation "Efficiency = (The difference of temperatures)/the first temperature.
     After spending time working with steam engines, Carnot decided that they could not use 100% of the heat.  This was due to some the heat being lost during the process.  Clausius later called this entropy.  I really, really want to talk about entropy, but I gonna save it for another time.
     As Carnot spent more time working on the problem, he hypothesized that if you increase the difference between the temperatures, then you can increase the efficiency of the engine.  Equations are fun to punch numbers into.  In this case, you can see that to get an efficiency of 100, you have decrease the tempurture to zero.    And entropy  makes this really hard to do in practice.
     Holy sweet Jesus, this stuff really takes a toll on my brain. And the worst part is, I always come out feeling like I didn't say what I wanted to.  Whatever, I'll just keep plugging away at this, and then I'll start feeling like I've gotten somewhere.  On an unrelated note, have you heard about there's going to be some information about the Higgs Boson experiement?  I'm excited to see what's released.

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