Welding a tank connector to aluminium

  1. James7519 New Member

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    Location:
    England
    i hAve a 15000L koi pond that the water flows through before going back to my heat sinks that removes any excess heat and takes the water back down to ambient levels of 25c even in summer colder in winter

    cooling water is much more efficient than cooling air due to the heat capacity and the thermal transfer ability of water.

    to be more efficient sometimes it is not about using a technology that is more efficient although I personally think this is more efficient than AC but about using things you already have to your advantage.

    so my koi pond has a 36000 lph water stream it’s long and narrow creating a fast flow river type pond with a waterfall that drops 1.3m straight down.

    A stainless steel pipe laid on the bottom of the pond will pass the heat from the radiators into the water. But due to my pond size, and the fast flow it already has the efficiency of that transfer will be significantly improved.
    Due to the large waterfall I already have the pond will not heat up from this as the amount of evaporative cooling going on.

    I also have fresh water going into the pond from a local water stream and it overflows around 300l a day. So a lot of the excess heat is evaporated or sent downstream.

    I spend 100s a month of paying for my heating to be turned on. But also hundreds in electricity for my servers which create heat - which is a bit dumb. So I aim to create the system to transfer this heat to my underfloor heating in my house and then any left over heat on the return line goes through the pond.

    So by doing this in the winter I manage to keep my pond from freezing which is nice a nice bonus for the fish, i heat my house and reduce heating bills, and reduce electric usage on AC usage
    In summer I can close the manifolds on my underfloor heating and send the water directly to my pond which even in the hottest day’s of summer never gets above 25c so the water in the return will always get back down to 25c which is more than cold enough to absorb heat and repeat the cycle.
    This links back to why I wanted 50mm x 50mm pipe so that I could have enough water in the system so that the water can heat from 25c -32c within around 30 minutes so the pump can be thermostatically controlled to turn on when water reaches 32 and turn off when it’s 25c. Otherwise in winter with the pump on 24/7 water temp willl get down to 5c and due to it being below the dew point water will flood my electrical components due to condensation
     
    Last edited: Feb 14, 2020
  2. James7519 New Member

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    29
    Location:
    England
  3. qwakers Member

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    426
    Location:
    cornwall, united kingdom
    cant see a ac switch, so looks like its dc only
     
  4. James7519 New Member

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    29
    Location:
    England
    I’m looking into other methods of sealing the end of the pipes first before I commit to welding based on the things you guys have said. Maybe I can find another way to seal the ends
     
  5. qwakers Member

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    426
    Location:
    cornwall, united kingdom
    brazing might work..
     
  6. James7519 New Member

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    29
    Location:
    England
    I thought brazing didn’t work with aluminium due to the oxide layer?
     
  7. qwakers Member

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    426
    Location:
    cornwall, united kingdom
    never thought about it, to be honest. will have to do some reserch
     
  8. Newlands Member

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    192
    Location:
    Sussex, UK
    There is a brazing process for aluminium - almost like soldering, and obviously a lower temperature than welding. Look it up on YouTube.
    An important concern would be that you are talking about mixing metals - aluminium to stainless can’t be joined by welding or brazing, and in your earlier post you mention aluminium to brass, which again can’t be welded and would also be a corrosion disaster waiting to happen, especially in the presence of warm water.
    To be perfectly honest I don’t think your idea of using aluminium box section is going to fly. It would be cheaper for you to go down to the plumbers merchant and buy some copper tube, a blowtorch, a roll of solder and some easy-flo flux and make a test rig up - soldering is a lot easier to master than ac tig, copper tube is easier to cut form and join, and it’s much better thermally than aluminium. Fifty quid plus a weekend in the shed will tell you whether it is worth continuing or whether to give it up.
    On the other hand, you could order in a load of expensive ally box section, buy a £1500 ac/dc tig plus more on the ppe gear and gas, and struggle to master welding for a couple of months to get to the same conclusion.
     
  9. James7519 New Member

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    29
    Location:
    England
    pipe won’t work otherwise I would do that. Components need a flat surface to be mounted onto with thermal adhesive for conduction to occur directly to the water
     
  10. James7519 New Member

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    29
    Location:
    England
    I’ve considered brazing aluminium to aluminium using sheet metal and a threaded aluminium bung but I can’t find any information on the strength of this kind of braze would it be strong enough?
     
  11. Newlands Member

    Messages:
    192
    Location:
    Sussex, UK
    I don’t know whether the aluminium brazing process is strong enough as I haven’t ever used it myself - did you look it up on YouTube?
    Copper pipe will work if you do some design thinking, but you’re trying to solve all the little design details before you’ve thought through the big issues first.
     
  12. James7519 New Member

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    29
    Location:
    England
    trust me I’ve considered copper pipe it won’t work - first issue being it won’t hold enough volume of water to have enough heat capacity
     
  13. Newlands Member

    Messages:
    192
    Location:
    Sussex, UK
    Ok. I’ll send my engineering degree back and ask for a refund.
     
    Brad93 likes this.
  14. James7519 New Member

    Messages:
    29
    Location:
    England
    If you use copper pipe which would only contain a small amount of water I’d have to encase the pipe in solid aluminium somehow so that the components can be directly mounted to it I can’t mount anything onto a copper pipe. If the aluminium isn’t touching the copper entirely convection happens instead of conduction which is less efficient.

    If I use less water capacity in winter the water will be freezing cold as soon as a water pump turns on. No room for water to mix and reduce temp gradually. So the water will end up below dew point and cause condensation on all the electrical components and fry them?

    a few posts up I posted a full detailed list of these things
     
  15. Pigeon_Droppings2 Member

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    2,697
    Location:
    london
    Aluminium brazing rods I think would work fine...they're used on radiator repairs too. Need a descent blow torch...tin the two pieces separately then heat as one I think would work.

    Mapp gas torch is what I use with them.
     
  16. Farside

    Farside Badly Welded Man

    Messages:
    3,634
    Location:
    Ireland
    Have you searched for box section copper pipe?
    Not saying such a beast exists, but it would solve your problem, at least insofar as a flat smooth face to stick the hot bits to, and much easier to join conventional copper pipe to via soldering. Easy to make a copper end plate with a tapped hole.
     
  17. carbon

    carbon Member

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    Retired likes this.
  18. northwest

    northwest Member

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    Manchester UK
    This.

    I have some 80mm copper pipe here and looking at it I would beg to differ. All you have seen is the 15mm stuff in B&Q, there are alternatives.

    Likely not. You would only get below dew point if no heat was coming from the servers, there is though. Besides, back in the nineties we used to just wipe the moisture off the monitors in the warehouses and fire them up. Dew causes corrosion. In the main.

    Alter your design (forget ally) and just solder flat copper plates to the (large diameter) round copper pipe where they come into contact with the hot bits. Fire up google and look at pictures of cooling plant, process plant or industrial installations. Get back to me if you find any of them using square tubing.
     
  19. fzr phil Member

    Messages:
    55
    Location:
    Grays Thurrock
    Perhaps an elaborate water block could be all made from copper, use refrigerant grade pipe back to your water fittings. Can all be brazed properly and pressure tested, could certainly be water-tight and Cu better than Al as conductor. Water flow will depend on your pump. Condensation is prevented with proper lagging.
    Good luck with your project.
    Phil
     
    Brad93 and Retired like this.
  20. fzr phil Member

    Messages:
    55
    Location:
    Grays Thurrock
    How many Kw of heat are you talking about realistically.
    I work on chillers/ heat pumps /you name it. In all environments process/industrial/commercial/residential from pretty small to as big as a house
    There could well be an off the shelf package. Suitable. I could give a lead to our sales team if you like. Where in UK?
     
    Brad93 and Retired like this.
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