Where i work is two doors down from a car body shop, and i would like to tell you a story about a guy called James who used to work there.

James did welding on chassis frames, heavy panels and would make you a damn fine workbench for £80 in just 2 hours. he used a propane cutting torch (not as effective as acetelyne, but far cheaper), and a propane welding torch for many years, and was very proffecient and most of all *safe* with them.

He was a bit of a prankster, and used to love filling latex gloves with propane, and setting fire to them, small fireball, everyone laughs. one day James wasnt there and one of his coworkers wanted to show a new employee the trick with the latex glove and propane. what he did however was use the gas torch how it had been set up, with a oxy-propane mix... and when he ignited the glove, the oxygen accelerated the explosion so much the fireball was nearly 20ft wide and ended up giving four people 1st degree burns.

When James was told about the accident he made a lockable cupboard to keep the propane and oxygen bottles in and he was the only person with a key, but when he went on holiday for 2 weeks last year he was told to leave them the key in case anyone had to do any welding, he did and he regretted it. about half way through his holiday he recieved a phone call that there had been an explosion in the body shop and that even tho no-one was killed, 2 people who were working late next door were injured from flying glass and one would be deaf for life.

It turned out that the same guy that did the bad glove trick had used the torch and bottles just a day after James left, and did not turn off the valves on the bottles, and gradually the cupboard filled with gas. a few days later the gas concentration in the cupboard was so high, that when the ringer for the office phone went off, a spark arced between it and the cupboard (about 4cm) and it blew up.

the moral of this story is, that propane is *very* dangerouse in some places, and not so in others. think about having a computer case, essentually a metal box filled with an explosive gas, and then a spark from the computer or the compressor or fan kicking in on cyclic systems.... bang.

Err oxygen is an oxidizer. Even aluminum will explode if powdered and mixed with oxygen. However no one has a problem with aluminum heatsinks inside a case.

Fact is we're not talking about oxygen, we're talking about propane.

The compressor in my chilled water setup sprung a leak in one of the lines. It was R12. I took it into the refrigeration repair shop (they are the ones that found the leak,) and since R12 is not readily availabe anymore (and expensive), they put in R414B. The tech said that it works better than R12 anyway. Here is a quick link to R414B, it is a blend of R-22, R-124, R142b, and R-600a.

http://www.refrigerants.com/hcfc-r414b.htm

redleader... uhh, you breath oxygen right? (at least i hope you do) just where do you get it from? bottled from the local 7-11? personally i get mine from the air, its free in most places, and often comes with a handy blue-lip-be-gone stick in case you are caught without oxygen for a few hours and need to look good for the ladies. :D

on a more seriouse note, i forgot to make it clear that only the propane bottle leaked, not the oxygen. the oxygen in the air acted as the catalyst, sorry :rolleyes:

how deadly is that r22 vapor ?? u guys scared me :p

Already covered. NM. :p

It's off topic but how hard is it to build an R290 (Propane) based cooling system? I am 14 but I want to build a Phase Change cooler for the computer I will be building soon. I will be getting an old freezer and using the parts from it and may have to fabricate my own parts. Will it be too hard or not. Cost is also an issue.

Using R290 is probably not your best bet, unless you have some HVAC supervision. It is fairly dangerous in the wrong hands. Your best best is to try and build the unit your self, and have an HVAC qualified tech check and fill it for you.

Thanks. How expensive do you think it would be to build the system from an old freezer and if I use an old freezer can I just leave the refrigerant in there?

I'd use some R404A or R507.

How expensive is R404A and where can I get it?

i must be a nitpicker here and say that it wasnt a catalyst since it was used in the reaction ;)

back on topic, I havent even attempted a phase change system but I have a quick question: when I do, can I just swap out refrigerants and not really worry about the systems design? Or do certain R's only work in certain systems?

I don't know if I'm going to laugh or what. :eek:
Is this really true?

You have to learn your R's. The compressor has to be able to produce enough pressure for the gas in question, the capillary tube needs to be have a length/ diameter appropriate for your gas's viscosity and pressure drop. The system has to be charged with an amount specific to your system.

Without that specific knowledge, :confused: :shrug: The only workable substitution I know of is R134 for R22, which involves a slight performance hit.

What caracteristics should the refrigerants have to be good?
Thermal capacity?
Weight per gallon?

Others?

Whats the best refrigerant? wich ones use the cascade systems?



And finally, Why are cascade systems dangerous?

well thats why im asking long before I get it ;)

someones offering me and my friend a compact AC unit meant for cooling a 50'x100' room that has a "silent" mode on it, apparantly the cooling element ices over even at that setting :D I was thinking of putting the cold element inside the case, keeping the main part external, as kind of an intro to phase change. no modding of the unit mind you. also i dont think itd have any condensation since the entire inside of the case will be cold, and condensation is a cold object in a warm atmosphere...so maybe on the outside of the case :D

My chiller's R12

Mine too. The two direct die units I have are R134a and R502.

Bad Humor
 

Hey! I've got a great idea...take propane as your coolant, and increase the density by mixing in some oxygen...propane's density problem solved! It would be cool too, the oxygen would sublime into super-chilled little bubbles in the propane, so get some transparent tubing and show it off to yer friends!

er... no. Any oxygen within a phasechange rig at all no matter how slight the amount can result in catastrophic results.

Oh boy! Introducing oxygen into a flammable gas and running it through an electric motor that performs high compression on it. Sounds like a description of a diesel motor, eh? Well, except that diesel is not a gas. Initially.

sarcasm meter: OVERLOAD

*WHOOSH* right over their heads. :p

Yeah, most people catch it, but I was worried about the few, the proud, the boneheads. Next step after adding oxygen bubbles to the refrigerant: test it! Nothing better than testing such a system with a oxy-acetylene torch on the soldered evaporator block, right?