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| mattinker:
A copper tube with water in it cannot heat to red heat. Have you ever tried to braze a copper plumbing installation with even the slightest amount of water in it? You just can't do it. It must be empty. Regards, Matthew. |
| vtsteam:
I'm not sure what you mean Matt by the "slightest bit of water in it". Flash boiler tubes routinely carry both water at the inlet and steam at the outlet, and may glow red along the superheated steam portion. This is commonly reported in operation. My question was, whether there was circulation in this copper coil or something closer to vapor lock, and therefore poor circulation. I believe, but will have to check again, that only part of the coil was glowing. Which would suggest circulation and flashing into steam along its length. If all coils in the flame were red, I'd suspect a lock. Yes I have soldered pipes before and pipes do need to be dry near the joint. I built and plumbed my house, and complete hydronic heating system including a wood furnace with copper heat exchangers and copper piping throughout. |
| mattinker:
Hi Steve, Well I was kinda thinking out loud this morning going out the door on my way to a job. I was pretty sure that you'd experienced the amount of energy to needed to keep a copper pipe dry whilst you braze it, it's enormous, red heat being of the order of 750°C is a huge amount of energy. In a small circuit, mostly filled with water, the pressure rise would be very fast, I would have thought that if it was circulating, the pressure would have gone up rapidly above 20 psi, I may well be wrong, (probably!) but I would have though you had a vaper lock! Regards, Matthew |
| vtsteam:
I lean toward that too, Matt, though thinking about it, it seems like even then it would have to "refresh" itself since it's below the main body and steam would be leaving it up through the body. It couldn't drop in pressure too low before at least a little water re-entered it to build it back up. But maybe not a steady flow. I'd like to work with it and see how good a flow can be achieved. And try different shapes. That's easy to do because the coil attaches with two flare nuts, so I can just change it out for another. This is kind of a nice design for experimenting with -- everything is screwed together and replaceable. This has a classic helical horizontal coil of 4 turns (I believe), per the magazine article plans. I'm wondering if a straight pipe might not work better because of increased circulation, even though it has less area. I wouldn't be surprised if that were true. I've seen them angle down gradually from the attach point at one end, and then sweep back up rapidly at the other. Probably what I'll try next. |
| mcflin:
This is the project I have been working on for many years ,a mono-tube boiler running on LPG and reaches 120 psi in 30 odd seconds,it still has bugs to iron out,but learning so much. ( hope the picture comes through ) |
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