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Stirling Cycle

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Posted by Morris Dovey on April 5, 2008, 2:50 pm
 
This is an attempt by the blind to lead the blind. Without any
good educational qualifications, I'm trying to post a
how-it-works web page to explain to other people (also lacking
currency in thermodynamics) exactly why/how the fluidyne engine
I've been working on is able to operate.

I'd be grateful if anyone who is up to snuff would take a few
minutes to look over what I put together and point out errors and
suggest improvements. I'd be especially grateful for that input
from anyone who teaches (or has tought) this stuff to newbies, as
well as suggestions that'd help remove the element of "magic"
from the picture.

The web page is at

   http://www.iedu.com/DeSoto/Stirling/StirlingCycle.html

...and my e-mail address is valid. Thanks!

--
Morris Dovey
DeSoto Solar
DeSoto, Iowa USA
http://www.iedu.com/DeSoto/

Posted by Morris Dovey on April 14, 2008, 3:45 am
 
Discussions in alt.energy.renewable led me to writing a software
model to simulate behavior of the solar-powered fluidyne we've
been developing (there's a photo at the bottom of
http://www.iedu.com/DeSoto/Stirling/Dyne.html  for anyone who
hasn't seen our "sewer pipe Stirling").

By simulating with different tube dimensions we can now get a
preview of how an "ideal" engine with those dimensions would
perform. I think I can rework the model to vary the dimensions
automatically so as to "hunt" for the dimensions to deliver the
best performance. There's a lot more to be done, but I thought
I'd share these results.

There's a pair of graphs at
http://www.iedu.com/DeSoto/Stirling/StirlingCycle.html  that may
help these pressure/temperature/volume values make sense.

This run assumes that the engine starts "cold" (at 70F) and that
the hot side is heated to 200F in a 70F environment at sea level:

     P(kPa)    T(C)     V(L)
    -------  -------  -------
0:  101.325    21.11     9.27

    106.299    35.56     9.27
    111.273    50.00     9.27
    116.246    64.44     9.27
    121.220    78.89     9.27

1:  126.194    93.33     9.27

    121.340    93.33     9.64
    116.846    93.33    10.01
    112.673    93.33    10.38
    108.788    93.33    10.75

2:  105.161    93.33    11.12

    101.017    78.89    11.12
     96.872    64.44    11.12
     92.727    50.00    11.12
     88.582    35.56    11.12

3:   84.438    21.11    11.12

     90.469    21.11    10.38
     97.428    21.11     9.64
    105.547    21.11     8.90
    115.142    21.11     8.15
    126.656    21.11     7.41

4:  126.656    21.11     7.41

    132.873    35.56     7.41
    139.091    50.00     7.41
    145.308    64.44     7.41
    151.525    78.89     7.41

1:  157.742    93.33     7.41

    143.402    93.33     8.15
    131.452    93.33     8.90
    121.340    93.33     9.64
    112.673    93.33    10.38
    105.161    93.33    11.12

2:  105.161    93.33    11.12

    101.017    78.89    11.12
     96.872    64.44    11.12
     92.727    50.00    11.12
     88.582    35.56    11.12

3:   84.438    21.11    11.12

     90.469    21.11    10.38
     97.428    21.11     9.64
    105.547    21.11     8.90
    115.142    21.11     8.15
    126.656    21.11     7.41

4:  126.656    21.11     7.41

    132.873    35.56     7.41
    139.091    50.00     7.41
    145.308    64.44     7.41
    151.525    78.89     7.41

1:  157.742    93.33     7.41

     P(kPa)    T(C)     V(L)
    -------  -------  -------
1:  157.742    93.33     7.41
2:  105.161    93.33    11.12
3:   84.438    21.11    11.12
4:  126.656    21.11     7.41

--
Morris Dovey
DeSoto Solar
DeSoto, Iowa USA
http://www.iedu.com/DeSoto/

Posted by Morris Dovey on April 15, 2008, 12:43 pm
 I've managed to convince gnuplot to plot the data I posted, and
managed to do (most of) a plot window capture using xvpick. The
result is at

   http://www.iedu.com/DeSoto/Stirling/fm_plot.gif

Note that the (vertical) pressure scale runs from 80 - 160 kPa
and the (horizontal) volume scale runs from ~ 7.5 - 11 L.

--
Morris Dovey
DeSoto Solar
DeSoto, Iowa USA
http://www.iedu.com/DeSoto/

Posted by daestrom on April 15, 2008, 10:07 pm
 

I like it, but I see the numbers on the left are cut off a bit.  Probably an
'xvpick' issue?

daestrom


Posted by Morris Dovey on April 15, 2008, 11:27 pm
 daestrom wrote:

It's not an "issue" - it's a _feature_ :-)

--
Morris Dovey
DeSoto Solar
DeSoto, Iowa USA
http://www.iedu.com/DeSoto/

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