[MFetch]

To Anyone:

I am working on my 7th grade science fair project. I chose solar energy and my dad and I are putting together 2 solar energy systems. The first a batch system. the second a thermosiphon system.

Now my question: I understand that ethylene glycol is used as a heat transfer fluid due to its corrosion resistance and good heat transfer properties. The thermosiphon is bascially a solar heat collector (copper pipes) 1/2 inch  arrainged in a veri=tical grid conntected at the top and the bottom. Then a verticle pipe 3/4 rises about 4 feet out of the middle of the collector to a heat coil. This coil is connected to a "water heater" metal cup of water.

The theory is the sunlamp will heat the ethylene glycol it should turn to a heated vapor rise up to the coil transfer its heat to the water via the coil. Once the heat is released it should return back down the pipe to the resivoir as a liquid. It should start the process all over again.

What I do not know is what percentage the antifreeze solution shiuld be? 100% antifreeze, or mixed with water to lower the percentage.

What amount of fluid should I use? half full in the collector so it turns to a gas? If it will turn to gas. or COMPLETElY full so the fluid transfers its heat by molecules rising thru the coolerr fluid and cooler fluid decending? any suggestions or ideas.

Michael

[MFetch]

Yes I did research on the project. But no one give the percentages and I don't understnd.

This ois a closed solar water heater system not under pressure and works with no pumps or moving parts.

Michael

[Mitch]

Alright this will be my rant on science fair projects. Most science fair projects seem to have very little to do with science; they are usually nifty engineering setups, or interesting diagrams of natural phenomena. It leaves science fair judges, like I have been, wondering where did the science go?

This relates to your question like this. In science nothing works the first time, its just one of those things. Science really is fixing the problem by a series of experiments to eliminate the problem. This is what a science fair project should explore.

You should try pure antifreeze first and see how well it works and measure its efficiency. You should then make successive mixtures of water and antifreeze until it works and measure their efficiency, you can make other mixtures if you want to measure the efficiency of your system. That would be a real science experiment. Don't mistake the construction of the device with the science you can do with it.

[MFetch]

Propylene glycol is safer but there are less toxic possibilities of antifreeze as well.

[MFetch]

I under stand but that is not my experiment and i am nearing the science fair. That would be an experiment for another time right now it would be an experiment within an experiment. I don't have time as a luxury.

My experiment is actually which system will work more efficiently not an some clever engineering project. Although it is clever. I just want some suggestions for which may work better. 100% or 50% like a auto antifreex mixture. And should the system be full or 1/4 full just ideas. It's not like I am building a volcano and demonstrating how to mix baking soda and vineager.

Michael

[sugarhillave]

in a book problem, 40% ethylene glycol was used. try it

[MFetch]

Ok,

40% does that mean it will boil faster or slower? Does that mean it will transfer heat better??

Should the system be full so heat rises thru the fluid or should the system be just in the collector so that only the heated gases rise thru the piping then transfer?

Any ideas on the process? I know what it is supposed to do just how to get there is the issue.

Michael