Phase-change as a school project - Questions

[DBurton]

I have been scrounging phase-change forums looking to learn everything I can for a while now, and now I am looking to build a direct-die system as a science fair project for school. The problem is that I have only about 1 month to get this done, and I also don't have an endless budget. My questions are 1.) can I get a working system in time (doesn't have to be perfectly tuned or anything, it just needs to work) and 2.) approximately how much am I looking at spending? I will have quite a bit of time to work on this over Christmas break (3 weeks of no school), so I am hoping that with enough work and some breaks on cheap parts, I could pull this off. However, if all is hopeless, then someone please tell me before I start spending money. :)

I'll be spending quite a bit of time around here if this works out.

[Maxprime]

I did a similar research project in high school - make sure you know your stuff very well as if you get an EE for a judge they can ROAST you. When I was in high school nobody was looking for supercooling for higher #'s - they were more worried about PC100 haha.

[herefishy]

Hi DBurton,

Do you have any acquaintances in the refrigeration or air-conditioning industry?

[afireinside]

Originally posted by herefishy
Hi DBurton,

Do you have any acquaintances in the refrigeration or air-conditioning industry?

Yea that will make or break the project. Getting your hands on a compressor and stuff at an affordable price wont be easy. Your also going to need tubing, make an evap or buy one from baker, a torch, MAPP gas, brasing rods and gauges along with the compressor condencer filter/drier and refrigerent.

[Chris_F]

Do you know everything you need to know to build it? If not, get reading FAST. If you do, then I think an affordable DD system can be made in a months time. What refrigerant will you be using?

[afireinside]

What refrigerant will you be using?
I'd assume he will have to use R134a or R290 as theres no way he will be able to get lisensed and buy some R22/r404a/other refrigerent in a month along with build a system. Now if he would tell us what he knows about this and if he knows anyone...

[DBurton]

Alright, I've got some connections with a machine shop for the torch and possibly the machining of an evap (if I don't buy the baker block, which I probably will). I am also looking at a Danfoss SC12MLX compressor, so if anyone can give me some opinions on that, then the help would be greatly appreciated. I am really thinking that I can pull this off, I just need to start calling around to some local a/c shops to find someone who will help me out.

Thanks guys.

[\/icious]

if your lookin to go cheap and easy then all you need to do is buy an window ac unit and change out the evap. You might need to change the cap tube but since your only going for a working system then i wouldnt think the current cap tube will be a problem. The only thing you would have to do is braze the evap and get her filled. That shouldnt take much time at all and wont burn a hole in your pocket

[DBurton]

Originally posted by \/icious
if your lookin to go cheap and easy then all you need to do is buy an window ac unit and change out the evap. You might need to change the cap tube but since your only going for a working system then i wouldnt think the current cap tube will be a problem. The only thing you would have to do is braze the evap and get her filled. That shouldnt take much time at all and wont burn a hole in your pocket

This is one thing that I have been seriously considering, and I'm going to the local thrift store tomorrow to see what kind of units they have. I know I've seen them there before, but I've never really taken a close look at anything. Thanks for the suggestion.

DBurton

[Chris_F]

If you use an AC you will have to refill it. I take it you don't have r22 so you would be out of luck. You could use r134a or R290. I wouldn't suggest R290 since this is your first time. r134a isn't great, but it will work. The only thing is you'll have to change the oil in the compressor. I would just buy a r134 compressor. It would probably be better.

[afireinside]

Whats so dangerous about R290 if your careful and read up on it beforehand?

[Redwolf]

Seeing its for a science fair.. Ask if Propane (R-290) is going to be a problem first.

[DBurton]

Propane shouldn't be a problem for the science fair, but seeing that the unit will be in my room after all is said and done, and that my room isn't the most ventilated in the world, I'd rather use something that won't cause problems should I ever have a leak. If I end up having to charge the system myself, then 134a seems to be my best bet, especially since super performance isn't my main goal. However, if I can find a place to do this for me, then I might take a look at some better options.

DBurton

[afireinside]

Na just say R290 if they ask ;)

[Chris_F]

I wouldn't use R290 unless you feal confident about building this. One spark and a little oxygen mixed in with the R290 = :explode:

Just keep safe when working with propane.

[afireinside]

Just be careful and your ok. I plan on using propane my first time. Its not THAT much propane considering the size of the system so I doubt it would kill you... But dont be suprised if you are brazing a joint and arnt being careful and wake up an hour later at the other side of the room with burn marks all over :p: