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OBA question - cooling the air

Discussion in 'The Garage' started by Shaggy, Sep 11, 2003.

  1. Shaggy

    Shaggy 3/4 ton status

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    <font color="green"> I have my York OBA system all set up and it works great. The only issue that I have is that the air gets really hot really fast since the compressor itself makes so much heat. I've been trying to come up with a simple way to cool the air off before sending it to the tank.

    Here's what I'm thinking, I just want to see if you guys think that I will cool the air much with this method. I'm considering buying 1/4" (actually has a .311" ID) copper tube and making a big coil that I will mount in front of the radiator ( a spiral coil, not just coiled up like you would coil a hose). I'll use as much of the tube as I can to make a coil that's about as long as the radiator is wide. I fiugre I could use maybe 20-30 feet or so. I would sweat pipe fittings to each end of the coil, so the air would come out of the compressor, through a stainless braided line to the copper coil, through the coil, back out to another stainless braided line, then back to either the manifold or the tank. I know that copper transfers heat well and will cool liquid very efficiently due to the heat trrnsfer, but will the heat transfer be very good with just air passing through the lines? If it only cools the air a few degrees then it won't be worth it. Any engineers out there that can run some numbers on it maybe? /forums/images/graemlins/thumb.gif</font>
     
  2. dyeager535

    dyeager535 1 ton status Premium Member

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    My dads using copper AFAIK to run the line back to his tanks (under the bed) but I kind of doubt he did it for the cooling effect.

    Copper isn't supposed to be good for vehicle applications (fatigues) but in this case, I'd not worry too much about it.
     
  3. HarryH3

    HarryH3 1 ton status Author

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    How about using an a/c condensor (or even the evaporator, if you can figure out where to mount it) to cool the air. Those are already designed to deal with high pressures and have excellent abilities to shed heat. /forums/images/graemlins/cool.gif
     
  4. Shaggy

    Shaggy 3/4 ton status

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    <font color="green"> I thought about that but haven't really looked into it, primarily because I've found that AC systems use all sorts of goofy fittings. I don't know how easy one will be to adapt to the system without having to jury rig it, slicing lines and using hose clamps to reattach them and whatnot. Any idea what kind of connectors are on a condensor?</font>
     
  5. HarryH3

    HarryH3 1 ton status Author

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    I'd just get the lines for the condensor from a junkyard and cut 'em to fit. If you don't want to use any barbed fittings, then a place that makes hydraulic hoses could press on some serious hydraulic fittings for you. /forums/images/graemlins/cool.gif I just had the flexible part of the engine oil cooling lines replaced on my wifes Suburban. The hydraulic shop just cut the crimp sleeves off the old fittings, then crimped on new Aeroquip hose. Total cost was a whopping $28 for about 4 feet of hose, 4 new crimp sleeves, and labor. /forums/images/graemlins/thumb.gif
     
  6. dyeager535

    dyeager535 1 ton status Premium Member

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    Here's another question, why do you want to cool the air down anyways?
     
  7. Shaggy

    Shaggy 3/4 ton status

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    <font color="green"> I'm afraid of melting my oil coelescing filter, it only has a 150 degree maximum temp on it, and I read on PBB that some guy actually had the exact same filter burst into flames because his OBA got too hot. </font>
     
  8. dyeager535

    dyeager535 1 ton status Premium Member

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    *That* makes sense. I asked my dad about his, and he was also concerned with the rubber lines...problem is, unless you can use "hard" line right from the pump, you still have to run hose to get from the pump to the frame. (if thats the route you are taking)
     
  9. Shaggy

    Shaggy 3/4 ton status

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    <font color="green"> All of my flexible lines are teflon lined braided stainless rated to over 400 degrees, so that's not really an issue. The copper that I want to use would be solely to cool the air down a bit before it gets into the meat of the system. I would run flexible stainless lines from the compressor to the copper line and also back from the copper line to the tank. The copper line would just be bent into a coil. Picture if I took a bunch of copper tubing and wrapped it around a good sized fire extinguisher from top to bottom, it would be a spiral maybe 8" in diameter and 2 or 3 feet long, then mounted the resulting coil of tube somewhere in front of the radiator or another vacant spot.</font>
     
  10. willyswanter

    willyswanter 1/2 ton status GMOTM Winner

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    Make a piece of tubing about 12" long and wrap it in 50watt peltiers. Put a good heat sink on the other side of each pelt and there you go, 0* C cooling at the pipe /forums/images/graemlins/thumb.gif

    http://www.mpja.com/productview.asp?product=9080+PM
     
  11. Shaggy

    Shaggy 3/4 ton status

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    <font color="green"> That's an interesting idea... Would need to come up with a heat sink for it, but the biggest problem I see is that the peltier is flat and tube is round, so heat transfer would kind of suck. It would get pricey too. /forums/images/graemlins/thinking.gif</font>
     
  12. willyswanter

    willyswanter 1/2 ton status GMOTM Winner

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    Some of the surplus equipment places, such as mpja.com and meci.com sell small condensor type things, small radiator about 12" x 8" with regular NPT ports ranging from 1/8" to 1/2" with a fan attached right to it that runs on 12vdc. It's what I planned on using.
     
  13. Shaggy

    Shaggy 3/4 ton status

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    <font color="green"> I just went and searched those sites but didn't come up with anything. They must be calling them something wierd... </font>
     
  14. willyswanter

    willyswanter 1/2 ton status GMOTM Winner

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    Yeah I can't find them either but in the paper catalogs there all over in there... Can't seem to find one of my catalogs though...
     
  15. Twiz

    Twiz 1/2 ton status

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    Allmost - kinda - sorta related.

    Here is what I did for my air compressor at home.

    You can see that the 1/2" copper tube is very discolored from the heat as it exits the compressor. As it runs down the line and cools - the copper color comes back. So, you know it's doing something - at least. The line getts very-hot, very quick, and cools down just about as quick when it cycles off.

    Factory "O", it had a single line from the left bank, run into a tee on the right bank, then about a foot of tubeing into the tank. That line was discolored all the way to the tank and the tank was much warmer to the touch, than it is now.

    I run another 60-gallon tank, spliced off the out-put of the main tank, for 120 gallons total. I never - ever, ever get a drop of water of the hose (A good thing, if you paint).

    That said, for a "on-board air system", I think I'd run dual tanks. A smaller one as a primary, to cool the charge and hopefully catch any water, making it easy to drain. Then from there into a seccondary tank.
    (One of the main purposes of the tank is to cool the air)

    BTW - 1/2" copper tube is a b!tch to bend by hand !
     
  16. Triaged

    Triaged 1/2 ton status

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    My thoughts on this...
    I haven't installed my OBA yet (still haven't made a bracket yet...but I do have a welder now) but I have put quight a bit of thought into it.

    I have desided to run a coil of copper hose from the York to the frame rail and all the way to under the truck where the tank will be. I have poly engine mounts and am not really worried about the tube cracking. The coil should provide for plenty of flex. The frame will also act as a heat sink on its way back to the tank. I haven't planned on running a oil seperator because I'll just drain it out from the tank along with all the moisture (the tank should be the lowest point and with care I could keep a good slope on the line to the tank). I then plan on running a line back from the tank to the front as well as the back (all copper) for the quick disconnects. That way they should have little moisture or oil because the tank will sepperate it all out.

    I am doing it this way for a few reasons.
    1) 1/2" copper is cheep and flows well
    2) Copper can handle the heat (and is cheep too)
    3) Copper is cheep (starting to see a pattern?)

    My thought is that even if I have to replace the coil from York to frame a few times I am still alot cheeper than braided stainless and rejecting alot more heat as well.
     
  17. 4X4HIGH

    4X4HIGH 1 ton status Premium Member GMOTM Winner

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    All this talk about running copper lines. IIRC heat anneals copper which makes it soft, I would think that would make it crack easily or not accept the 125 PSI pressure. I have OBA and I run a oil/water filter and I just used 300 PSI air line all the way around. I have no leaks anywhere and it doesn't get too hot either.
     
  18. 4x4Freak

    4x4Freak 1/2 ton status

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    Air conditioners (residential) use all copper lines. The discharge line directly off the compressor gets really hot and almost always has atleast 100 psi and around 200-300 psi when running. I have even seen one that was pushing 400 psi with no problems from the copper line. I dont think the heat would affect it enough to cause any problems.
     
  19. Shaggy

    Shaggy 3/4 ton status

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    <font color="green"> Cool twiz, that definately demonstrates that the copper will transfer heat pretty well. I run both the oil filter and a water seperator so I'm not too concerned about water in the lines, I'm not going to be painting off the OBA :P but I don't want any water in the ARB. Putting a second tank in would not be easy, it was hard enough finding an out of the way place to put the first one.

    Here's a pic of the system as it sits right now, I'm going to move the filters over near the manifold, so the air won't hit them until it's gone through the copper coil and the tank. In retrospect it was a mistake to run them right off o the compressor, but that's the way almost everyone does it so I didn't think it would be a problem when I first built the system.

    [​IMG]

    Thanks for the input everyone, I appreciate it. /forums/images/graemlins/thumb.gif</font>
     
  20. FWP

    FWP CRS

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    Why not just put the filters right before the points of use?
     

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