Re: THERMODYNAMICS [Re: Technology: Inverted energy source..]

From: Robert J. Bradbury (
Date: Fri Mar 17 2000 - 11:18:16 MST

On Thu, 16 Mar 2000 wrote:
> I eagerly read "Engines of Creation"...and the well as "mambo
> chicken" and anything else i could find on MNT....I haven't seen anything
> lately....why not?

There are a couple of books on my Reading List page, and I'm sure
you are aware of most of the authors discussed on the list - Bear,
Stephenson, etc. Robert Freitas is going to write a popularization
of Nanomedicine that I expect will be very cool, but he has to finish
the other two technical volumes first. There are an increasing number
of academic books, e.g. Nanotechnology by G. Timp, these are high-throw
weight books that will give Nanotech an increasingly legit image.
I've heard that Nordly is working on an interstellar nanoprobe

If you really like nanotech, you can always lurk out on sci.nanotech.

> But anyway...what you were saying about nitro bricks...
> Basicly it would work but it would just cost too much?
Yep, you gotta put more energy in to manufacturing the bricks
than you can get out by having a cooler sink. Your engine
is normally going to operate at 95 C (368K) [slightly less than
the boiling point of water], you are sinking that to 21C (294K),
so your efficiency is (368-294)/368 = ~20%. Going to LN2 bricks
as the sink @ 63K gives you (368-63)/368 = 82%. So your engine
efficiency goes way up. Maybe you get 3-4x the MPG?

Actually, there might be some problems with doing the calculation
this way since the operating temperature that should be used
might need to be closer to the fuel-air temperature in the cylinder.
[Guess I need to read the books a little more...]

I'd have to spend more time than I have today to calculate the costs
of making the N2 bricks, but I'm pretty sure the manufacturing costs
for the bricks would be much more than the fuel savings. Figure
it this way -- I've heard that Liq. N2 costs about as much as milk.
As a very gross estimate, I'd bet you need fill up with several
times as much Liq. N2 as gasoline. N2 bricks would be slightly more
expensive and you would have to shovel them into your "locomotive".

Now the interesting thing, if the calculation done the way I've
outlined is correct, is that you would win quite a bit by being
able to operate your engine at a higher temperature. (The boiling
point of water is way below the ~70% the melting point of steel,
which is where metals start getting soft). You could run at a higher
temperature by finding a fluid that boils at a higher temperature
and remains liquid wherever you are driving the truck. In
glancing around the net a little, it appears that poly-ethylene
glycol (the main ingredient in raditor additives I believe),
comes in various molecular weights (more or less "poly").
The higher MWs, presumably have higher boiling (and freezing
points). So if you want to put high MW PEG in your radiator
in Florida and low MW PEG in your radiator in Minnesota, you
should be able to pick up some efficiency. You might
also need a variable speed pump between the engine and the
radiator, so you can precisely control the temperature by
varying the rate at which the fluid circulates.

For a really good design, you would have to include a centrifuge
that would spin the fluid with taps in the inner/middle/outer sections
so it could pump the high/mid/low-MW PEG into or out of the circulating
mixture, then you wouldn't have to change the fluid as you move
around the country. [This is based on "biology" techniques known
as sucrose or cesium chloride gradient centrifugation, where you
centifuge the liquids to get different densities at different
levels in the test tube so you can separate materials of different
molecular weights.]

Given what trucks cost and how much fuel they use, I'm surprised
someone hasn't thought of this. The next time you are talking
with some engine people Mick, you might ask them about this.
Maybe the problem is that you don't have any biologists doing
design at the engine companies... :-)

The really advanced engines though are totally ceramic, so they
didn't need coolant at all and could operate at very high temperatures
and efficiency. Most of that work though has been sidelined by the
fuel cell research because of the requirements for reducing pollution
levels. Comparing the efficiency of fuel cells to combustion
engines would be an interesting effort (for another day).


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