LTD Stirling Engine on wet sponge - ?

[Tom Booth]

Question:

Could an LTD type Stirling engine be made to run on evaporative cooling ?

I was thinking that it would be possible to simply place a large sponge in a pan of water and set an LTD engine on the sponge to test the idea.

It might help to cut some groves or channels in the sponge to increase the sponge's surface to air area for more air circulation through the sponge and more cooling.

I've read of LTD engines that are supposed to be able to run on as little as 1 degree Temperature difference.

I'm fairly certain that the evaporative cooling from a wet sponge could create at least a 1 degree temperature difference, especially on a warm dry day with low humidity.

Anyway, I don't happen to have one of these LTD engines available and was wondering if someone who does would be willing to try it and maybe post a video.

[theropod2]

Oh you can do better than water, and I'd use something with a higher evaporation rate to start with, say a 50/50 mix of water and alcohol, with a fairly stiff sponge that wicks well. Maybe concentrate light on the hot side via a simple magnifying glass. You might be able to pull it off with just water, if you can get a really really good reduction in friction, and light moving parts. Go for it!

R

[Tom Booth]

Oh you can do better than water, and I'd use something with a higher evaporation rate to start with, say a 50/50 mix of water and alcohol, with a fairly stiff sponge that wicks well. Maybe concentrate light on the hot side via a simple magnifying glass. You might be able to pull it off with just water, if you can get a really really good reduction in friction, and light moving parts. Go for it!

R

Thanks for the input and suggestions.

I agree, alcohol would work better but would also cost money (for the alcohol).

I don't want to assist the process with added heat (from light or other source) just air temperature on top as heat source and the cooling by evaporation on bottom. Otherwise this would defeat the purpose: i.e. to see if evaporative cooling alone would work.

I think most standard or typical LTD engines already have little friction, light moving parts etc. if they can run on the heat from someones hand, so I'd like to see if this could work without any special modifications to the engine to begin with.

As I said, I don't have such an engine available at the moment. If someone who does could give this a try I'd appreciate it. If not, I'll probably be getting or building some kind of LTD Stirling in the future but I guess I'm impatient and thought someone here might have one and could easily run such an experiment.

Otherwise I guess I'll post the results whenever that happens.

I already searched YouTube and the internet to see if there was anything like "Stirling Engine runs on wet sponge" or the like but couldn't find anything so I thought that this must be something that hasn't been tried before.

[Ian S C]

I have run my one on ice packs, If you put the icepack underneath, and sit the motor in the sun it runs in reverse. My motor normally runs on hot water. Ian S C

[Tom Booth]

Well, I found this:

[youtube]http://www.youtube.com/watch?v=ARD3ctp80ac[/youtube]

A wet piece of paper. Close enough.

[Bumpkin]

"I don't want to assist the process with added heat (from light or other source) just air temperature on top as heat source and the cooling by evaporation on bottom. Otherwise this would defeat the purpose: i.e. to see if evaporative cooling alone would work."

Tom, it seems like it might evaporate better from the top, though I suppose it would be harder to get the ambient heat to the bottom. Bumpkin