What liquid expands the most with a temperature change?

[4570Man]

I can't go into the details of the project but basically I intend to fill the bottom side only of a "hydraulic" cylinder with a yet to be determined fluid. What is going to provide the most movement of the cylinder with a temperature change? Just looking at a couple of charts that I have no idea what they actually mean maybe Ammonia.

 

[Tractor Seabee]

There are more complications to this than appears on the surface. Ammonia is nasty to work with and needs to be under a high pressure to remain liquid. Any gas off the liquid will be compressible so will not move the push rod. The seals on a hydro cylinder will probably not be compatible with a lot of fluids, especially like ammonia. Think Teflon seals. A lot of research on temp/press relationships and hydro calcs are in your toolbox for this. You will be dealing with more than one liquid/gas physics laws. My arm chair engineering at work.

Ron

 

[4570Man]

I've already thought about at least the corrosive part. The possible solution was to use an expansion tank. Put the expanding liquid in the rubber bladder and put put oil in the other side. Then it expands and forces oil out of the cylinder into the tank.

 

[texasranger556]

I suppose a pertinent question is what are you trying to accomplish? Detect a temperature change? Move something heavy (or light) based on temperature? Something else?

Have you ruled out electronic sensors and actuators?

 

[4570Man]

I'm trying to move something light based upon a temperature change. Electric isn't an option.

 

[MossRoad]

Remember that many liquids don't expand at a regular rate. That is, they don't expand proportionally to temperature changes. Mercury in a thermometer expands very regularly through a broad temperature change. So keep that in mind for your project X.

Also, you can't compress a liquid, so if its under pressure, it won't move much. Release the pressure and woosh!

 

[MossRoad]

I'm trying to move something light based upon a temperature change. Electric isn't an option.

Have you thought about using metal like a thermostat?

 

[4570Man]

Have you thought about using metal like a thermostat?

I probably need 10 pounds of push and 3 inches of travel. I don't think the metal could accomplish it.

 

[MossRoad]

I hope you share the project once its done.... sounds interesting. :thumbsup:

 

[bcp]

Greenhouse vent cylinders.

From:
Automatic Greenhouse Vent Openers & Circulation Fans

How automatic vent openers work: Vent openers do not require electricity. The opener has a metal cylinder containing a mineral which expands when heated. This pushes a piston that opens the vent. As the temperature cools, the mineral shrinks and a spring closes the vent and resets the piston. The opening and closing of the vent is gradual allowing just the right amount of air flow for cooling.

and

From:
Greenhouse Accessories : Univent Automatic Vent Opener Replacement Cylinder

Use the Standard Vent Opener to lift up to 15 lbs, and the much stronger Gigavent, with powder-coated green, all metal construction, to lift up to 65 lbs.


Bruce