How do I seal copper pipe under pressure?

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I'm building a heat exchanger. It's 12" sections of 1/4" soft copper pipe half full of R134a. Only problem is filling/sealing them. I need a bunch, so a fill adapter for each one is outa the question. Schrader valves from old inner tubes work, but they're a lot of hassle. I've tried crimping/folding/soldering. Can never get it quite sealed so the solder will stick.
What's the trick to mashing the pipe so it seals well enough to get the solder on?
Thanks, mike
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    After you pour the R134a in, quickly apply one of these to the end of the tube
http://tinyurl.com/36nt2c7
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I think what you want is a "pinch off tool".
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Stormin Mormon wrote:

Typical ads say, "locking clamp...free both hands for other tasks." Suggests that I need to leave it clamped till the solder is done. Duh!! I'll try that.
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They changed designs, since I last saw one of these. This is what I found.
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item50372763114&rvr_id=&crlp=1_263602_263622&UA=WXF%3F&GUID 6ff5631290a03662f386a3ff9d6e10&itemid50372763114&ff4&3602_263622
http://tinyurl.com/2dnz6lv
New ones by Vise Grip seem to be the rage now days.
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If this is for a DIY heat pipe and will be used above freezing, just use distilled water as the working fluid. You can easily control the temperature at just above the boiling point to purge the air out but not have so much pressure that it keeps the solder from wicking in.
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Heat pipe, look it up. A sealed tube lined with a wicking material that is saturated with the refrigerant of interest. If heat is applied anywhere along its length the refrigerant evaporates at that spot and recondenses everywhere else where it is cooler. They are used extensively in computers these days to help transport the heat away from the high wattage chipsets, CPUs, and GPUs.
If the OP omitted the wick then his will only work upright by gravity return with the heat applied at the bottom.
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Daniel who wants to know wrote:

Turns out that the tire shop will give you all the used tire valve stems you want. Solves the sealing problem. Stick an air chuck on a R-134a can and I can fill 'em with ease.
Heat pipes work great. Kinda cool to use a stethoscope to listen to them boiling away as the heat moves.
Big problem getting heat from air into them with LOW temperature difference. Looking for any design info on optimum fin shape for heat transfer from air to pipe.
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On 7/29/2010 5:14 AM, mike wrote:

The problem with tire valves is that they're made for air. The valve cores do not use the same sealing materials as those for refrigerant. If you use an automotive valve stem, get valve cores made for refrigerant use. If you're going to make a bunch of heat pipes, get a process tube adapter to use along with a pinch off tool. To get a consistent amount of refrigerant into your tubes, you'll need a way to measure the amount of charge by using a scale or charging cylinder. I don't know how much money you want to spend making your on heat pipes but you may consider purchasing them from a manufacturer who has already spent tons of money on research and development.
http://www.ntxtools.com/network-tool-warehouse/ROB-12458-p-ROB.html
http://www.licensedelectrician.com/Store/SP/Dial-A-Charge.htm
http://www.enertron-inc.com/store.asp
TDD
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The Daring Dufas wrote:

Yep, but they work just fine for prototyping.
If you're going to make a bunch of

This is a hobby. Expensive tools are out of the question. Spending $7 on a pipe swaging tool made me cry. The heat pipe thing is a fun diversion trying to save some weight. I expect by the time I'm done, I'll be going back to a parallel-plate cross-flow heat exchanger.
To get a consistent amount of refrigerant into your

Stick ice cubes on the bottom half of the pipe and fill from top. Liquid condenses up to the level of the ice.
Verify with stethoscope listening to the pipe. Small heat source moved up/down the pipe. You can hear it boil when you reach the liquid level.
I don't know how much money you

ZERO!
but you may consider

No fun in that. Might as well go buy an HRV and pay to have it installed. It's more about the building and learning than the end result...and saving most of the thousand bucks.

Thanks, mike

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I stuck myself in the eye with a fork once - made me cry, too !

Really ? R134a condenses at 32 F and 0 PSIG ? Wow. I never knew that.
Can I come over and watch ? Because I'd really like to see you do that. I'd really like to see you 'pour' your 134a ( I think you mentioned it ? ), out of the jug, which will have ~ 80 PSI of pressure in it at room temperature, as a liquid, into a open container at 32 F, and have it sit there as a liquid. I'd really like to see that. Seeing as that's only ~ 42 degrees above it's boiling point at atmospheric pressure.
Yessirre, Bob, that would be a good one to watch . You see, I would expect it to BLAST out ( under 80 PSI of pressure at room temp in the can ), and ( assuming you're pulling liquid ), instantly boil off to a gas as it hit room pressure of 0 PSIG ( 14.7 PSIA ). Silly me. That's what I would expect.
    But that's just me, it may work different for you.

    Or you could stick your tongue on the pipe and see if it sticks. That would make about as much sense as the rest of your crap.

    He asked how much you want to spend, not how much you know !

Hope you have great insurance !
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.p.jm.@see_my_sig_for_address.com wrote:

You're confusing your failure to read/understand with my creativity. More thinking and less typing is in order.

Right on both counts. I ask questions when I don't know something. So far, there's been ONE response that actually helped somewhat. The rest have been restating the obvious... I need constructive, creative help, not criticism.

your superiority. What I actually said was: "Stick an air chuck on a R-134a can and I can fill 'em with ease. " No mention of atmospheric pressure at all. Note the title says, "UNDER PRESSURE".
http://nm7u.tripod.com/homepage/rube2.jpg
I really enjoy reading this group because of all the self-serving crap that is displayed. The lack of creativity displayed is mind-boggling. The propensity to denigrate instead of help is far more extensive than in the average newsgroup.
It is hard to not be pissed off by all the mudslinging when it's at me. But I'll get over it and move on.
Snicker all you want...I've got heat pipes that work even without your "help".
http://nm7u.tripod.com/homepage/fins1.jpg
Thanks again to the one person who did actually provide helpful input. Makes it worth wading through all the crap to find that nugget of info.
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On 7/29/2010 9:18 PM, mike wrote:

On your homepage, is that you in the black bikini? 8-)
TDD
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I lost track; who was nice to you, the Mormon? He just wants to convert you.
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Of course! I hope it's obvious.
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Real Pisser wrote:

See, you can't even get that right. Misinterpretation of the situation is the norm here.
I don't recall saying anything about "nice". I said "helpful".
Nice is just common courtesy....UNcommon on the web... almost nonexistent in this neck of the web.
People are welcome to be as obnoxious as necessary to make themselves feel good...as long as they're helpful.
I'm easily annoyed by unhelpful people who chime in just to be obnoxious. May make them feel superior, but it does NOT make them look superior or knowledgeable or smart.
And yes, I do understand that nothing that I can say here will change that.
Party on!
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On 7/30/2010 8:12 PM, mike wrote:

I still want to know if that's you in the bikini on your home page. *snicker*
TDD
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On 7/29/2010 2:36 PM, mike wrote:

Well, Mike, I find a lot of those expensive tools at pawn shops. I bought a swaging tool kit for copper tubing some years ago at the supply house for $100 and later picked up an identical kit at a pawn shop for $50. I got it for a friend I work with because he'd been admiring my kit. I go around to all of the shops I can find because of the great stuff I can pick up.
TDD
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