Flash boiler effort

Some of us have been discussing a stand alone flash boiler. kind of a homemade hot water on demand unit.

I used a design I got from kladue that used four seperate coils joined through a manifold. Johnbeer has been talking about this as well. My problem has been getting the thing to stop leaking. I have not given up, but I decided to tak anothe course and see what happened.

I took a 50' coil of 3/8" copper I had for a chiller and roller it into a coned coil I installed this inside an old cornie with the bottom cut out. I ran an inlet and outlet through the cornie wall and bracketed the whole beast over a high BTU burner.

I pumped water from one of my kettles through the heater. The water began at 58 degrees. Running at about 2 GPM with the burner moderately high it raised up to 178 degrees in one pass.

This worked great and really used a whole lot less propane then heating the whole kettle at one time. It also means I can reduce my brewing schedule significantly, utilize my second kettle as a heated mash/lauter tun.

I want to play with some other configurations and need to address venting the burner as it exits the heater.

I will be keeping track of this project in the new Gadget Junkie group. Come check it out and add your own projects.

Here's a question... are you running the cold inlet at the top of the coil and the hot out end closest to the flame? I think that would be more efficient in the same way that a counterflow works.

That sounds really nice - keep us posted, for sure!

I am running top down. I have not compared it to bottom up. I should compare the two so we have some data.

And I get to ask "where are the pictures?"

The top down flow is the most efficient but, at low flow rates the warming water gives up the dissolved air which makes bubbles that can cause steam pockets and popping sounds. The bottom up flow works for both high flow for strike water heating and low flow for sparge heating as the bubbles move with the flow and do not cause localized steam pockets. The nicest feature with the flash boiler is the water is hot in 60 - 90 seconds so you dont have to wait 30+ minutes to get started when heating the HLT to temp, and temperature change is regulated by water flow or burner firing.

Anybody got any updates? I'm THIS close to cutting the bottom off a perfectly good corny and mangling a 50' 1/2" B3 superchiller for this. Also, what's the best way to get the rubber skirt off the top?

ScubaSteve said:

Anybody got any updates? I'm THIS close to cutting the bottom off a perfectly good corny and mangling a 50' 1/2" B3 superchiller for this. Also, what's the best way to get the rubber skirt off the top?

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don't mangle a perfectly good chiller just go buy a 50 foot roll of copper. I think once i go to bigger batched in the 20-30 gallon range im going to have to do this. right now though im trying to build an all electric 10 gallon. this is a fantastic idea though

OK, let me see what I can add here. I haven't got any good pictures, but I will see what I can do. The real trick is getting the tubing exposed to the heat. So coiling is key. Lots of loops that cover the entire space of whatever vessel (in my case a cornie) is housing them. Also your burner is important. I have a burner out of an old Hotsey pressure cleaner. It puts out a nice broad flame and handles high pressure propane (lots of BTUs.

My cornie was already shot. It leaked and the lid was half off. I just cut off the bottom, which was also dented (a real dog of a cornie), and heated the top from below with my burner. It just came off. I had to clean off the residual adhesive, I think it was butyl or something like it. I used a wire wheel on my drill.

kladue said:

The bottom up flow works for both high flow for strike water heating and low flow for sparge heating as the bubbles move with the flow and do not cause localized steam pockets.

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Ok, kladue didn't see this info until just now for some reason. I have been asking about other things in other threads, but are you saying a spiral that goes from larger diameter to smaller diameter, then back on itself to a larger diameter would be a good coil design? I figured I would overlap the coil-less space on the previously spiraling level of coil as I continued the rest of the way up the boiler chamber. I also planned on the coil continuing around the spiral in a mostly level or gently sloping up position, followed by a more upward angle when transferring between levels of spirals. Would this be efficient?

Also would you recommend 3/8" soft copper for this, or would 1/4" be something to consider?

kladue said:

The nicest feature with the flash boiler is the water is hot in 60 - 90 seconds so you dont have to wait 30+ minutes to get started when heating the HLT to temp, and temperature change is regulated by water flow or burner firing.

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So, assume for a second that we are talking about my system (A mash tun with a false bottom and another filter screen prior to the bottom drain, pumped through a return manifold that exits atop the mash tun. This manifold will have steam "directly" mixed in via .5 micron SS air-stone, placed ? distance before where the thermometer is attached to the manifold for reading your exiting wort temperature.) If I had the boiler set to produce steam at a specific burner setting and a specific supply water rate, I could recirculate my wort and adjust temperature via my wort flow control? Then, when the wort starts to show a temperature increase just turn down either my burner or my water flow on the boiler?

The old system uses a 1/4" Od X1-1/4" ss screen wire diffuser that has the wort flowing over the screen, steam and/or hot water on inside of screen. Operation goes like this, fire wort pump, fire water pump from tank and adjust water flow to 2 GPH, fire boiler burner and adjust fire to get desired mixer temp. As mixer inlet and outlet temps go up the boiler gas flow is turned down to control mixer temp, boiler water and wort flow remain constant. At low water flow into bottom of boiler coils the steam is superheated in the upper part of the coils before it leaves top of the boiler, maximum measured temp has been 300 degrees during a maximum output test, typical is 219 deg F. during step mash. Heated wort raises mash temp as it circulates without need to stir mash and efficiency has been 75%, a function of mill setting to get recirculation rates up. So far this method has worked for me for last 5 years with the old system.

For the boiler design question it depends on what you want to do, heat water or make steam. For water heating the top down method is most efficient, multiple tubes slow flow rate through each tube and give water more time to heat. For steam generation at low flow rates bottom up is best method because of dissolved air causing bubbles that block flow in multiple tube designs in a down flow setup. Tube size is a function of coil sizing and bend radius limits for material used, 1/4" is easier to bend than 3/8" but takes more footage to get same surface area. Main goal in coil construction is to get as much of chimney tube covered so hot gasses flow between coils instead of up a central opening.

Have you guys run preheated water from a cooler HLT through this boiler to get sparge temp water? I imagine the time is minimal?

Pete08 said:

Have you guys run preheated water from a cooler HLT through this boiler to get sparge temp water? I imagine the time is minimal?

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I'm running tap water thru mine and right into the HLT at what ever temp I need. My last brew had 3 sparges of 9 gallons each I was able to get the sparge water in the HLT and at 180* in about 10 minutes (each 9 gallon sparge)

Ahhh, I'm looking to be a little more fuel efficient, so I was thinking of building a boiler for preheat water, then recycling it to run my temps up for sparge water; you answered my question. Your temp control is by water flow adjustment and burner adjustment? Thanks for responding!

Pete08 said:

Ahhh, I'm looking to be a little more fuel efficient, so I was thinking of building a boiler for preheat water, then recycling it to run my temps up for sparge water; you answered my question. Your temp control is by water flow adjustment and burner adjustment? Thanks for responding!

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Yes, I run the burner full and control the flow to get the temp I need. To heat 10 gallons to 180* in 10-12 minutes is a lot better then I would be if I tried to heat it all in the HLT.

If you have a pump the flash boiler could be used for all kinds of things. Heating strike/sparge water, doing step maches, mashout, and even getting the wort to a boil faster.

This is pretty intriguing. If you weren't interested in making salt additions to your hot liquor, I could see this replacing your HLT and saving quite a bit of money in a larger system.

FSR402 said:

Yes, I run the burner full and control the flow to get the temp I need. To heat 10 gallons to 180* in 10-12 minutes is a lot better then I would be if I tried to heat it all in the HLT.

If you have a pump the flash boiler could be used for all kinds of things. Heating strike/sparge water, doing step maches, mashout, and even getting the wort to a boil faster.

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next time your brewing i wanna come watch!

eriktlupus said:

next time your brewing i wanna come watch!

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Ok I'll let you know. After that 25 gallon batch I'm kind of "stocked up" right now.

Thanks for the help.