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# Pipe Bending

## Pipe Bending

(OP)
Good day

I have a limited space in which to put a condenser ( 25 x 14.5 x 2.5 cm and i required about 650 cm^2 area. At the moment I have proposed simply using bent piping (180 degree bends to form parallel tubes - looks like a snake shape) with water flowing through it. I can get the required area but the bends at the end of the tubing are very tight so we hit manufacturing difficulties...in the order of 1 pipe diameter. Welding is an option but it is a lot of welds and going to end up quite expensive for what seems quite simple.

The constraints are the volume and the feed points which are fixed at 140 mm apart

Another idea we have had is to simply increase the bend diameter but then weld on flat metal plates at right angles to the tube to make up the lost area. This seems possible but I haven't yet got down to solving the little differential equation that pops up to check the net energy transferred.

So any ideas for a cost effective easy to implement solution or an easier reasonably accurate way to calculate the amount of energy transfered when i weld the flat plates on.

I am looking also for a text which has the minimum bending radius for pipes.

Kind regards
Ryan

### RE: Pipe Bending

Take a look at SPIRAL PLATE HEAT EXHANGERS, large surface area in a small envelope.

Another possible , if copper would work as the material of contruction are refrigeration subcoolers, check with a local refrigeration part supplier, SPORLAN manufacturers these I believe.

Try filling the pipe with sand heating, with a rosebud, to 900-1000 C and bending as tight as you can.

What about machining a piece of metal to accept two pipes in a socket joint.

+----------------------------+
|                            |
+  -  -  -  -  -  -  -  -  - +
|                            | drill thru
|                            | plug ends
+  -  -  -  -  -  -  -  -  - +
|     |       | |       |    |
|     |insert | |insert |    |
|     | pipe  | | pipe  |    |
+----------------------------+
fillet weld
around pipe

Hope these ideas help, Rich

### RE: Pipe Bending

Since the pressure difference between the steam and cooling water is small, couldn't you use several parallel flat plates with gaskets ? E.g. between 6 plates you would have
5 spaces ( W/S/W/S/W ) and with rivets or screws you could
make a compact, large surface assembly.

For sketch, send FAX#

### RE: Pipe Bending

The condenser that you are designing is tiny...I'd assume that it is for a refrigeration cycle?  One thing that may help you is to design it more like a shell and tube heat exchanger with straight tubes and open manifolds on the turns.  These manifolds would direct the flow to the appropriate tubes in order to achieve the three passes that you deem necessary.  I believe that this may also be what nbucska was talking about.  Good luck.  Look forward to hearing what your final design is.

### RE: Pipe Bending

For a text on pipe bending try "Voluntary Standards for Cold Bending of Pipe".  You can purchase it at www.fmametalfab.org

Also try "Standards of Tubular Exchanger Manufacturers Associaion" (TEMA).  I think this one is closer to what you're doing.  You can probably find them on the web.

Kevin

### RE: Pipe Bending

Instead of filling with sand, we have had good luck with filling the tube with a cerro alloy then bending.  It keeps the flow area about as round as I have seen.  We were making precision bends in 1.5" s.s. tubing for an underwater hydraulic manipulator.  The cerro alloys are a low temperature melting point metal that will expand a little when it hardens.  After bending, you can put the tube in boiling water and melt the metal out.

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