[dooberheim]

Anyone heard about this?

Click

This is an old article - I remember the name Wallace Minto from an old (1969) issue of Popular Science that described a 350 hp steam engine that he developed, that used Freon as the working fluid. I remember the VW bus he had it in would do zero-60 in less than 6 seconds.

Also, as a corollary to the above, has anyone heard of small steam engines that could run generators (or other machinery) for a home or small group of homes? Since they caould run on pretty much any fuel, I'd think more work would be being done with them.

DK

[gnm]

Interesting. I'm skeptical however about his claims of a few degrees difference. An ammonia cycle fridge works similarly to this but require more like 300 degrees? (not sure) of difference (usually provided by a small pilot light or electric heater). Also I believe that what would actually happen is that the propane or freon would evaporate until the vapor pressure overwhelmed the evaporation and it simply sat there in an equalized state. It would have to have a lot better condensor to lose enough heat to condese right away also. It simply would not spin fast enough because of the condensation time to make any real power. It an interesting notion but not likely to work as described.

-G

[strider3700]

technically yes it will spin. It's an overbalanced wheel, I'm not sure if the name changed before or after this was invented. They built one on mythbusters and got it to spin. However The one they built was only about 5 feet tall and I don't think it did 1 rpm. I don't believe the torque was all that impressive either.

Here's a link
http://www.phact.org/e/wheel.txt

The reason they work in such a tight temperature range is it's right around the boiling point of their gas/liquid of choice. It's an interesting idea but I have my doubts about the efficiency.

[gnm]

I looked into it a little more - apparently mother earth news even built one back in the 70's which was 22 feet around. It did turn but did not really prove to be something you could extract useable power from. More just a novelty really. Like the drinking bird toys...
There a yahoo group about it as well and it appears no one has ever been able to make an effective one.

-G

[dooberheim]

I also found this article:

http://www.amasci.com/freenrg/minto.html

But like the mother earth article it said just that it turned, not what it's efficiency was likely to be. Since Carnot's law states that efficiency of a heat engine is constrained by the ratio of temperature in to temperature out, I guess it could never be very efficient operating with just a few degrees difference.

Just wonderin'

DK

[pilferage]

It'd be kinda cool to set up a couple mirrors that could track the sun (using some kind of optical sensor) to heat this thing up. Given a few mirrors one might get a few horses out of this thing. Kinda like the solar two...

edit- 40' diameter... maybe it could make a few hp?

[oiless]

It's been a while since I did the math on minto's wheel, but there are size limitations, based on your working fluid and your material strength. I think 40' would be outside the limits of practicality.
The thing most people that look at it don't seem to get their head around is that not all the working fluid is vapourized. Just enough is vapourized to push the fluid in any given chamber to a higher opposed chamber.
When I looked at the problem years ago I thought that all the designs I was seeing (including the Mother one) were flawed. The working fluid chambers should be two parts, so that one small heat exchanger chamber can be heated to drive fluid in a larger second chamber to the opposing chamber set. Having to heat and cool only a small amount of fluid would raise efficiency and speed, I believe. Whether Minto himself realized this I don't know, I've never seen drawings that I could be sure were his, not someone elses interpretation.
Maybe some day I'll have time to try it.