Quote:
Originally Posted by MEMPHIS91
...But if I did make it this is what I was thinking. Pipe in pipe. Center pipe is for water with larger pipe around it filled with R290. Do several of these tied together.
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There have been several DIY HXs similar to your drawing, done here at ER.
Acquario did a very interesting unit, that used a plastic shell and had multiple copper coils running inside, for the refrigerant. His first try had insufficient copper tubes, so he rebuilt it with more tubes, and got the results he wanted.
http://ecorenovator.org/forum/40959-post9.html
Also, randen did an interesting one wherein he used large flex pipe for the shell and copper inside for the refrigerant. You'll need to search for that one. The part that made that one work was machined brass end plugs that he could braze the refrigerant lines to, and ot also had fittings for water. With your amazing hack brain, you'll likely come up with an off-the-shelf solution.
Your biggest problem will be maintaining a hermetic seal of the refrigerant carrying portion.
The pressure involved in the water portion will be in the very low psi range, whereas the pressure of the refrigerant will be very high, and will be subject to severe temperature cycling.
So, if you're gonna do tube(s) in shell, think through your tube structure, and how it must be constructed, then think how you will need to wrap a metal or non metal structure around it, that will allow your water flow and maintain a seal at 10 psi or so.
Also, there is some flexible pipe material that is intended for connecting natural gas to a stove or something. This stuff is interesting because it has a high surface area, and would encourage turbulent liquid flow, which will increase efficiency. I have seen it in stainless and also in copper. The copper variety should be easy to braze. The stainless could be brazed also, with care, high-silver brazing rod and proper flux.
Rave on!
-AC