[NiHaoMike]

I have not built that type of heat exchanger. I did build an open coil heat exchanger for my air compressor (so I can inflate tires with cool air) which is just about 5' of 1/4' tubing coiled to about 3" diameter, using a glass jar as a form to coil it around.

For your use, it would be similar except you'll probably want to use a longer length of 3/8" copper tubing and a tighter coil so it fits inside a piece of 4" PVC or CPVC pipe. Drill two holes near the ends of the pipe to allow the tubing to connect outside, then drill and tap two more holes for water. (If you're using it as a condenser, you'll want the water inlet near the bottom and the outlet near the top.) Then affix something to the inlet to force the water to cyclone inside, such as an inch or two of copper tubing bent to force the water to exit at an angle. Close off the bottom with an end cap and the top with a screw thread fitting and plug so it can be taken apart for cleaning and modification. (Or use screw thread fittings on both ends for maximum flexibility.)