This project was inspired by Brewpastor and my craftsmanship by BM.
After reading BP's thread about the flash boiler idea I knew I had to do this. Most of my brew day is spent waiting for things to heat up. And I'm moving up to 30 gallon batches soon so this is only going to get worse.
So I quickly slapped together something that I thought may work. It was 20 feet of 3/8 copper tube rolled into a stainless charcoal starter tube and placed onto an extra burner a friend gave me. It worked for the most part but was not very efficient. With the tap water coming in at 67* I was able to hit a exiting temp of 192* at a flow rate of one gallon at 3 and a half minutes. And with a very small move of the valve it was down to 130*. This was with the burner kicking for all it had. and wide open water flow would get me to about 90*.
With a little more thought and looking around the house I found a Korny keg that I had that was shot. The gas in port threads were all screwed up. Perfect I thought, so I cut the bottom off, removed the rubber handles with a screwdriver and a map gas torch. Took the keg and burner to work where I welded 4 plates to the burner to hold the keg. Then I placed the keg on the burner and fired up the plasma cutter. Cut holes thru the plates and the keg at the same time then cut two slots up the sides to have a place for the tubing to go thru.
I then took 50 feet of 3/8 copper tubing and rolled it around a 4" PVC pipe. I rolled it up the length for the keg and then back down.
My thought was that if the water was going in and then up, then down and out it would give it two points it would be in contact with the flame and spend more time in the intense heat.
My test run tonight went well and I see room for improvement.
Tap water coming in was 63*
at full flow I was getting a flow rate of 3 gallons per minute.
With the burner at full bore and water at full flow I hit a max temp out of 113* (a 50* increase)
It took some playing with flame and water flow but I managed to hit my mash in temp that I need of 175* at a flow rate of .555 gallons per minute (one gallon took 1:52). Not as fast as I would like but I think I can get this better. I was not able to get a good flame (a lot of yellow fire) so I will add some air holes around the lower part of the keg near the burner.
The valve was still really touchy. There was a point where it was to fast or two slow so I think I'm going to add another valve either inline with the one I have or on the out port . My thought is that it would allow me more control and get me out of that touchy point in the valve.
But this may be perfect the way it is. I'm not looking to rid myself of my HLT just get the water into there either at temp or damn close to it. I brew using water from my hot water tap (water heater is 3 years old and always gives me clean water) so in this case my water would be going in at 120*, with a full flow rate of 3 gallons per minute with a temp increase of 50* that would put me within 5* of my mash in temp of most my beers.
This would mean that I could be mashing in (theatrically) in 1-2 minutes. As it is it takes about a minute to fill the HLT then about 30 minutes to heat it.
My next thought was that once I go to a pump system I'll be able to pump the wort from the MLT thru the boiler and into the kettle. Not getting it to boiling but I'm shooting for like 200 - 205* so then it would not take me long at all to get 40 gallons to a boil.
Here are my pics, now post your thoughts.