Flash boiler

[GreenMonti]

On the topic of the flash boiler, I noticed a few runs ago that my coils were moving on me. It was mentioned to me by Kladue to tie the coils to the inner pipe with some copper wire. I wanted to see things move and to show everyone else thinking of making one of these that this should not be overlooked. I took it apart today so I could address this.

Here is a couple of shots of it.

Here it is now. You can see the copper wire I used to hold the coils in place. You'll also notice the coils are like they should be.

 

[kladue]

Looks like it is holding up well after what must have been some high temperatures in the coils during the steam runs.

 

[GreenMonti]

Looks like it is holding up well after what must have been some high temperatures in the coils during the steam runs.

I have put it through its paces on purpose.

 

[kladue]

After the tuning runs with the stainless coil boiler and having to run nearly 100% to hold temperature at the higher flow rate, I think I will be copying your copper coiled boiler. The plan is to make 6 - 16' coils with 3-3" coils that are centered on water feed tube and 3 - 2-1/2" diameter coils that fit between centered coils and hopefully will fit in the existing 6" tube. Water feed will still be at the bottom and the outlet at the top to fit existing boiler connections, with increased burner clearance on the bottom. The plan is to fabricate and pressure test in Arizona, and ship it to Oregon to install during May R&R runs.

 

[GreenMonti]

After the tuning runs with the stainless coil boiler and having to run nearly 100% to hold temperature at the higher flow rate, I think I will be copying your copper coiled boiler. The plan is to make 6 - 16' coils with 3-3" coils that are centered on water feed tube and 3 - 2-1/2" diameter coils that fit between centered coils and hopefully will fit in the existing 6" tube. Water feed will still be at the bottom and the outlet at the top to fit existing boiler connections, with increased burner clearance on the bottom. The plan is to fabricate and pressure test in Arizona, and ship it to Oregon to install during May R&R runs.

I was thinking about this just today at work. Mine was a bit picky on the high flow rates too until I installed the preheat coil. With a total of 6 coils though, I would just about bet you wont need the preheat coil. Should be good. I would love to hear how it works.

I want to make a new boiler myself just to make one, and make it with compression fittings on the top and bottom. This would allow servicing one of the coils or replacing one of the coils should something get clogged or who knows what. If SS swage lock fittings were used it would make building the distribution blocks much easier. Like yours.

 

[TBrosBrewing]

I have a design question about this, sorry if I missed the answer to this while reading the previous 28 pages. Is there a reason that the outflow of water doesn't move counter to the burner. It seems to me that the water would be more efficiently heated if the water input were at the top of the coils and ran down towards the burner, similar to a counter-flow chiller. Then out of the center pipe. When the water is converted to steam, would the back pressure be uneven or cause other problems?

This is a very well thought out system, and is a very appealing project. I'm just trying to understand it a little better.

 

[GreenMonti]

I have a design question about this, sorry if I missed the answer to this while reading the previous 28 pages. Is there a reason that the outflow of water doesn't move counter to the burner. It seems to me that the water would be more efficiently heated if the water input were at the top of the coils and ran down towards the burner, similar to a counter-flow chiller. Then out of the center pipe. When the water is converted to steam, would the back pressure be uneven or cause other problems?

This is a very well thought out system, and is a very appealing project. I'm just trying to understand it a little better.

The reason for the flow the way it is is due to steam bubbles forming and blocking flow. The steam naturally wants out on a uphill path. So we are giving it that, and in turn we get a more smooth running system.

 

[willynilly]

I tried to find it in this thread...

What is the BTU output of your burner?

Also, there was talk about superheated steam...

Doesn't super heated steam have a much lower heat transfer coefficient than saturated steam? How will that play a role in heating with the steam?

What is the final determination on if it can boil a kettle? What is the temp. rise time from say 60F to 160F? What have you calculated as the effective BTU transfer to the kettle? With the rated BTUs of the burner and the time to heat, is it effcient to heat a boil kettle in this manner? Considering time and cost of fuel?

I am trying to wrap my head around Kaludes boiler that produces 3-4 POUNDS of vapor per minute in the other thread... but the BTUs, time and such arent making any sense to me.

Thanks

 

[GreenMonti]

I tried to find it in this thread...

What is the BTU output of your burner?

Also, there was talk about superheated steam...

Doesn't super heated steam have a much lower heat transfer coefficient than saturated steam? How will that play a role in heating with the steam?

What is the final determination on if it can boil a kettle? What is the temp. rise time from say 60F to 160F? What have you calculated as the effective BTU transfer to the kettle? With the rated BTUs of the burner and the time to heat, is it effcient to heat a boil kettle in this manner? Considering time and cost of fuel?

I am trying to wrap my head around Kaludes boiler that produces 3-4 POUNDS of vapor per minute in the other thread... but the BTUs, time and such arent making any sense to me.

Thanks

I need to send you a pm man.

My burner is a brinkmann and they claim 170,000 BTU/hr.
All the threads have the same boiler, I tried to stay on topic but it would appear that I can't do that very well.

The superheated steam is going to be used for the mash temp increases. Very little water input into the mash this way. It will be a direct injection into the recirculating mash.


Edit: As it stand now, I can heat water at .5GPM from 50 to 212 output instantly. I need to increase the flow so I can see how fast I can run it to get instant strike water at 160-170. Probably pretty quick. Then it will be turned down to either maintain or to do a step mash (the superheated steam) if I would like too. It will then give me instant sparge water. I will then kick it in the rear and do my boil with it. It will be a single heat source brewery when I am done.

 

[willynilly]

I try to keep my inbox full, so I dont get PMs What is up man?

When you are heating that .5GPM from 50F to 210F you are getting 664 BTUs per minute, so that is 39,840 BTU/hr heat source (equivilent)

664BTUs per minute / 110F temp rise = 6 pounds of water/min

160F output at that BTU rating: .73 GPM at the afore mentioned BTU output (39.8K BTUs)

664BTUs per minute / 120F temp rise = 5.5 pounds of water/min

170F output at that BTU rating: .66 GPM at the afore mentioned BTU output

That is the mathematical result, your results may vary.

 

[GreenMonti]

I try to keep my inbox full, so I dont get PMs What is up man?

When you are heating that .5GPM from 50F to 210F you are getting 664 BTUs per minute, so that is 39,840 BTU/hr heat source (equivilent)

664BTUs per minute / 110F temp rise = 6 pounds of water/min

160F output at that BTU rating: .73 GPM at the afore mentioned BTU output (39.8K BTUs)

664BTUs per minute / 120F temp rise = 5.5 pounds of water/min

170F output at that BTU rating: .66 GPM at the afore mentioned BTU output

That is the mathematical result, your results may vary.

Just in reference to me trying to follow you around and answer all your questions. I could just tell you all the info in one shot.

At .5GPM my boiler shutters and puts out 212* water. It is boiling in the boiler at that rate of flow.

 

[Mista_Sparkle]

So I had a thought while studying for a thermodynamics exam a little bit ago

What would be an interesting experiment would be to turn your flash boiler/coil heat exchanger setup into essentially one giant Heat Pipe

You would need to run it at a vacuum essentially, at least at room temperature where the only fluid was water, The thing could be gravity powered and its flow would be self regulated.

like this

 

[kladue]

That design and theory are good, the problem is the system friction losses require a pump to assist flow.

 

[Mista_Sparkle]

if you run it on a vapor cycle, you really wouldnt need a pump provided you apply all your heat on a vertical section

 

[kladue]

The demon in the works is friction, yes if the piping were made large enough to work without auxillary pumping it would be difficult to work with, down sizing the tubing and using a pump reduces cost of materials and size of distribution piping. What you have drawn is an example of steam heating systems with gravity return, research 1 pipe steam heating systems for a simpler design.

 

[Mista_Sparkle]

Its a bit different than a 1 pipe system as a 1 pipe system has to operate above atmospheric pressure, if something like this was implemented, it would be able to operate far below atmospheric pressure for superior heat transfer at lower temperatures. If the steam generator was of vertical orientation, it would be able to generate ρgz psi where ρ is the density of water in lbm/ft^3, g is the gravitational constant, and z is the change in height across the steam generator assuming a constant water level higher than the steam generator, ideally the fluid level would sit about even with the top of the boiler.

Since it would be operating at the vapor pressure of water, it would always be at its boiling point and allow approximately isentropic heat transfer as the temperature differential would approach 0 which would be the best that can occur without operating a heat pump

 

[diatonic]

Tubing coils aren't very effective moisture separators and you'd end up with a lot of liquid blocking steam flow, and probably develop some dangerous pressures.

 

[Mista_Sparkle]

Tubing coils aren't very effective moisture separators and you'd end up with a lot of liquid blocking steam flow, and probably develop some dangerous pressures.

I was thinking about, that, what You could do is on the exit of the steam generator, run it through a wider section of tubing with a drain back into the feed side, then you are left with only steam exiting.

Plus, if pressures climbed, the temperature would go up and excess heat would be forced back out in the pot anyway. Since the coils in the pot would be colder than those in the burner, the steam would HAVE to flow that way as it would be at a lower pressure than in the boiler. EDIT: as long as there is no air in the system

 

[diatonic]

Plus, if pressures climbed, the temperature would go up and excess heat would be forced back out in the pot anyway. Since the coils in the pot would be colder than those in the burner, the steam would HAVE to flow that way as it would be at a lower pressure than in the boiler. EDIT: as long as there is no air in the system

Or your household plumbing grade copper experiences a catastrophic failure sending copper shrapnel and steam in to you & your brewing buddies

 

[GreenMonti]

I ran the boiler today with nothing more then just an outlet. I had 58* inlet water, at a rate of 48oz/min. AKA 3.131lbs/min. I saw a output of 165*. So it would appear that the boiler itself is very efficient in what it does. About 93% efficient. Interesting?


Edit: Its only fair that I say I used the firing rate at 2.5 PSI. Which I/we assume is a pound of propane per hour usage. So, 21,952 BTUs/hr was the rate of burn. Or 365.8667 BTUs/min.

 

[GreenMonti]

I ran the boiler today with nothing more then just an outlet. I had 58* inlet water, at a rate of 48oz/min. AKA 3.131lbs/min. I saw a output of 165*. So it would appear that the boiler itself is very efficient in what it does. About 93% efficient. Interesting?


Edit: Its only fair that I say I used the firing rate at 2.5 PSI. Which I/we assume is a pound of propane per hour usage. So, 21,952 BTUs/hr was the rate of burn. Or 365.8667 BTUs/min.

This is a bit off. i should have posted this in the drunk thread.

The 165 output number was a different number. I did have 58* input at a rate of 48oz/min. The output was 156*. That makes the boiler 83% efficient.

The 165* output number was when I was testing to see how much water I could run through it at max fire. I was able to a little over 3/4 of gallon a min. The efficiency went down into the basement on that one. So it would appear that propane is more efficient at a lower pressure like Willy was saying.

 

[willynilly]

This is a bit off. i should have posted this in the drunk thread.

The 165 output number was a different number. I did have 58* input at a rate of 48oz/min. The output was 156*. That makes the boiler 83% efficient.

The 165* output number was when I was testing to see how much water I could run through it at max fire. I was able to a little over 3/4 of gallon a min. The efficiency went down into the basement on that one. So it would appear that propane is more efficient at a lower pressure like Willy was saying.

Yeah, it is a somewhat linear progression...

I think the issue is one of velocity. As you increase the pressure, and BTUs, you are also blowing those BTUs through that chimney at a much higher velocity, so you are losing a larger % of the heat to ambient.

83% is still pretty darned good, which amounts to 18,400 BTU/hr

It only takes 15,400 BTUs to get 12 gallons boiling from 58F
So at your 18,400 BTU/hr flow rate you could boil that 12 gallons in 50 minutes (if the transfer to the kettle is 100% eff)

That is using 1lb of propane per hour, which is VERY efficient IMHO.

 

[Mista_Sparkle]

something to keep in mind though is that the efficiency will decrease as the water/steam temp gets higher.

That is quite impressive though

 

[GreenMonti]

Yeah, it is a somewhat linear progression...

I think the issue is one of velocity. As you increase the pressure, and BTUs, you are also blowing those BTUs through that chimney at a much higher velocity, so you are losing a larger % of the heat to ambient.

83% is still pretty darned good, which amounts to 18,400 BTU/hr

It only takes 15,400 BTUs to get 12 gallons boiling from 58F
So at your 18,400 BTU/hr flow rate you could boil that 12 gallons in 50 minutes (if the transfer to the kettle is 100% eff)

That is using 1lb of propane per hour, which is VERY efficient IMHO.

Yea I agree. It would appear though that I will loose the same on the condensing coil. So 17% twice. I believe that a fair estimate would be about 66% all said and done right now. The issue I have right now is I have to heat the water tank with the waste/condensate. So, in essence I am heating up much more liquid then what is in the kettle. I am going to run it again all from a cold start and see how long it takes me to get a boil at the 2.5 PSI firing rate. Once it boils I will take the temp reading of the water tank and note the time.

 

[GreenMonti]

something to keep in mind though is that the efficiency will decrease as the water/steam temp gets higher.

That is quite impressive though

Right. The more equal they get I slow down.

 

[beercheer4me]

What is it? and what's it for ?

 

[willynilly]

For clarification, 2.5 PSI is equaling about 22,000 BTU/hr correct?

 

[GreenMonti]

For clarification, 2.5 PSI is equaling about 22,000 BTU/hr correct?

Yes, my understanding is 1 lb of propane is equal to 21,591 BTU potential.


I did another run and like before I hit the same number of 66% total system efficiency. That was for the first 30 min of run time. I didn't run it any longer.

 

[diatonic]

I'd hate to see your propane bills

 

[GreenMonti]

I'd hate to see your propane bills

I have only bought 3 tanks worth since the boiler was built back in December. I have made two batches of beer, run the boiler tests, and used up the rest on the grill. I still have 30 lbs in my current tank. Not bad. We pay like 13 bucks a fill.