What is boiling?

[willynilly]

Assuming the contents are at 212, for each 970 BTU you will get one pound of water to convert to steam.

A 9000W element is equivelent to 30600 BTU/hr.

(30600 BTU/hr) / (970 BTU/lb.) = 31.5 pounds of water vaporized in 1 hour. That is 3.78 gallons.

BTW, "flashing the surrounding water to steam" would be boiling. Don't fool yourself that entire contents of a pot over a flame is boiling: it is only the bottom inside surface of the pot that is boiling.

Right PP....

9000W will boil off about 3.5 gallons per hour, which is why it gets reduced to 4000W, which is just above what I need for 1.3 gallon/hr boil off.

9000W is only 30K BTUs, but that is A LOT of heating power when you are getting 100% applied to the wort!

If you had a 30K BTU gas burner, youd be sitting there all day.

 

[passedpawn]

There is a misconception here that when water in a pot boils, it ALL boils. No. Only the water leaving as steam has boiled. The rest haven't received their 970 BTU's/lb. of energy, and are sitting calmly hoping to get to the bottom of the pot where the heat is entering.

 

[Yuri_Rage]

I don't understand why this thread is going downhill with all of these arguments about what constitutes a boil. Most of the arguing is adding no value whatsoever.

Back on topic, my 5500W electric kettle is capable of vigorously boiling 18 gallons of wort (after a bit of a wait, of course), but I usually dial it back to maintain a boil that looks very similar to the first video. I'm quite satisfied with the results, and I've yet to taste any DMS.

 

[Mista_Sparkle]

passedpawn and willynilly are correct.

In a brewing situation, it would generally be much cheaper to go electric. Traditional gas fired is terribly inefficient. maybe if you run a water heater type design, or maybe monti's boiler design gas can approach electrics costs. Gas furnaces are generally cheaper to operate because the price of gas is low and the temperature of the air being heated is also relatively low and its running at a comparatively high mass flow rate for good heat transfer. Theres really quite a bit more to add, but I don't feel its worth the time.

 

[willynilly]

1 BTU to get 1lb of water to rise in temp 1F

13 gallons water is
108 pounds of water

From 60F to 210F:
16,200 BTUs required to heat in an hour
If you have 32.4K BTUs it will take you 30 minutes to accomplish this.

970 BTUs per POUND to create water vapor.
Creating 1.5 gallons of vapor per hour (boil off)
12.5 POUNDS of vapor per hour
12.5 x 970 BTUs per POUND per hour
12,125 BTUs to create 1.5 gallons of boil off per hour

1kW equals 3412 BTUs
12,125 BTUs equals 3.5kW
3.5kW equals 3500W

3.5kWh at $.12 per kWh
$.42 to boil off 1.5 gallons in one hour (unless you are in Hawaii)

 

[kladue]

After review of the boiler and calandria test runs with flash boiler @3.1 Lb/Min steam output, and only condensed steam leaving kettle, a theoretical transfer of 3055 Btu's/minute was calculated. With continous heat input to 12 gallons for 15 minutes to raise the water temperature from 50 - 160 degrees, an effective heat transfer rate was calculated at 1088 Btu's/Minute. Continued heat application at the same heating rate brought container to a boil with an additional 30 minutes of heating, with the calculated addition of 32.66K Btu's. While the measurements were less than scientific the boil should have happened much sooner if only an additional 970 Btu,s were needed over water heating to 212. It appears that the heat applied is diffusing into surrounding water and a significant amount has to be dumped into the container to reach a boiling point around the heat source. The amount observed was about 1/3 the expected 970 btu's/lb but still more than just 970Btu's over 212 degree water. During testing live steam was not lost from condensate line so most of the latent heat of the steam should have been going into the water, what was not quantified was the container heat losses through the sides and evaporation.

 

[passedpawn]

Wow, I wish I was there.

 

[kladue]

I am hoping to have a new boiler built by May R&R run home, and install it in the new system so all the flows and temperatures can be recorded. With gas flows, liquid flows, and system temperatures controlled and logged, just need to write calculations to be able to do a realtime heatflow during heating and boiling with both direct fired BK burner and steam heating.

 

[willynilly]

So if I am reading that correctly, which I may not be... it took 45 minutes to go from 50F to a boil in 12 gallons, correct?

If I am reading that correctly, that is 21,496 BTUs, or the equivilent of 6300 watts. (weight, temp. delta, and time)

I am probably reading that wrong.

I dont understand steam, so I apologize if I am missing something. If you are effectively APPLYING 1088 BTUs per MINUTE, that is 48,960 BTUs APPLIED in 45 minutes.

Your heating time of 45 minutes from 50F to a boil doesnt add up if that is the case. 48,960 BTUs in 45 minutes is INCREDIBLE, whereas 50F to a boil in 45 minutes is really quite lengthy.

With 48,960 BTUs effectively APPLIED to water, you could effectively BOIL 27 gallons of water in 45 minutes. Not 12. You only have to apply 355 BTUs per minute to reach 16,013 BTUs which is what it takes to get from 50F to 210F.

Phase change aside, is the 355 BTUs per minute correct to get from 50F to 210F in 45 minutes?

 

[GreenMonti]

Also, the 9000W BK (30k BTUs) is reaching a boil in 13 gallons from 160F in 11 minutes... how fast is a much larger gas burner doing this? 30K BTUs isnt much, not much at all, but I can tell you that is a huge volume to heat in 11 minutes! If you had a 60K BTU gas burner, youd be waiting a very long time, I can tell you how long... about 40 minutes according to my watch.

Are you turning on the element while it is filling? Once its covered.

 

[kladue]

The conundrum is we are applying roughly 3055 Btu's a min but only seeing 1088 Btu's a min in temperature rise. The effective rate and applied rates are quite a bit apart, but if the applied rate is used the 970 Btu's/Lb value is within about 10% of applied heat. during the testing steam was generated with 3.1Lbs/minute of water flow into boiler, all that was leaving coils in kettle was water not steam. Lack of insulation and a cover over the kettle has skewed the results, but without enough instrumentation we are left to guess the end result.
The observed effective heat applied was equal to 19 Kw/Hr, Boiler output was equal to 53.7 Kw/Hr, we need further research to close applied and observed gap. The plan is to repeat this exercise on an instrumented platform where all the inputs and outputs can be measured and recorded.

 

[willynilly]

Are you turning on the element while it is filling? Once its covered.

After the kettle is full (13 gallons) I then turn on the element. 11 minutes later she is a rolling. This is not a matter of turning on the element while the kettle is filling, that is cheating.

 

[willynilly]

The conundrum is we are applying roughly 3055 Btu's a min but only seeing 1088 Btu's a min in temperature rise. The effective rate and applied rates are quite a bit apart, but if the applied rate is used the 970 Btu's/Lb value is within about 10% of applied heat. during the testing steam was generated with 3.1Lbs/minute of water flow into boiler, all that was leaving coils in kettle was water not steam. Lack of insulation and a cover over the kettle has skewed the results, but without enough instrumentation we are left to guess the end result.
The observed effective heat applied was equal to 19 Kw/Hr, Boiler output was equal to 53.7 Kw/Hr, we need further research to close applied and observed gap. The plan is to repeat this exercise on an instrumented platform where all the inputs and outputs can be measured and recorded.

Right, I am reading something wrong. 19kWh would get you to a boil, from 50F in 15 minutes flat.

You are dealing with 100 pounds of water right?
You said you raised it 110F in 15 minutes. It takes 11,000 BTUs to get that temp rise, so that being done in 15 minutes (11000/15) is 733 BTUs per minute, right? Where was the 1088 calculated from?

I am perplexed as to why it took 30 minutes to get from 160F to a boil when you were clearly applying 733 BTUs per minute to the boil between 50F and 160F... theoretically you should have reached a boil in 7 more minutes. (100 pounds, 50F temp delta and te 733 BTUs per minute you were applying) Meaning you SHOULD have seen 22 minutes from 50F to a boil...

Unless, heating time (transfer) (and cooling for that matter) will be affected by the DIFFERENTIAL of the two elements... whether it is water and a heating element, or water and water in the case of a chiller.

Could it be that as your 12 gallons approached the temp. of your steam that the effective heat transfer was lessened because the differential was not as great? Think about it, this happens in chillers all the time. Chilling with 70F tap water will get you to say 100F pretty fast from a boil, but as your wort nears the chilling water temp, your transfer takes a hit. I have documented this extensively with closed cooling systems. Once the two mediums get close in temp, the heat transfer is drastically reduced. I think this may be playing in a role in that 30 minutes to reach a boil from 160F. Just a thought.

If you went from 160 to 210F in 30 minutes, you were effectively transferring 166 BTUs per minute. I think this is a case of the heating medium (steam) and the water in your kettle losing the large delta that gave you the faster heating in the beginning. This is simple thermal dynamics, you are losing your delta, and thusly greatly reducing your rate of transfer.

This happens to heating elements too... as the water gets hotter, the heating slows, though to a lesser degree since the elements are so much hotter to begin with.

 

[kladue]

Not quite so it takes 45 minutes to hit a boil at constant input rate, that is the problem, 3.1 Lbs steam a minute in, all liquid condensate out, and 45 minutes later it boils. Not sure how much superheat there was but the assumption for calculations was that it was saturated steam. With 3.1Lbs/Minute dumping 970 Btu's/lb into the water, it is taking more heat than just warmup and 970 Btu's combined should be. Since the condensate exiting the kettle remained a liquid during entire run we believe that the heat is going into the kettle.

 

[willynilly]

How hot is your steam?

I think you are losing your delta between the steam and the 12 gallons of water.

Think about it, place a coil in a kettle of cold water, pump HOT water through that coil and you will see a temp. rise, but as your kettle of water heats up, it heats slower and slower until it ALMOST reaches the temp. of the hot water circulating in the coil.

This is the only thing that I can think of that explains the reduction in heat transfer.

All assumptions aside. If I look at your temp. rise, time and weight of water, you were averaging 733 BTUs per minute from 50-160F and averaging 166 BTUs per minute from 160F to a boil... just looking at temp. rise, weight of water, and time.

Are you measuring the steam temps?

 

[kladue]

The problem with the math is in order for the steam to return to water it has to give up 970 Btu's/lb, just as it takes 970 Btu's lb to create. We put the steam in and get water condensate out, the heat has to have gone somewhere as there is no steam coming out with condensate.

 

[willynilly]

Bottom line is, you are not creating the heat that you think you are, or there is some efficiency loss somewhere. The 12 gallons temp. and time wont lie though, and I have no idea where the loss is.

But, read below... this blows my mind sorta.

 

[willynilly]

I have to ask...

How are you creating 3-4 POUNDS of steam PER MINUTE? That is really incredible. That is 22-30 GALLONS of vapor per hour. That is like having a boil off rate of 22 gallons per hour...

970BTUs per pound of vapor
2,910 BTUs per minute
174,600 BTU/hr heat source

What in the heck do you have that is effectively transferring 175,000 BTUs to your boiler?

If you go to 4 pounds per minute
that is over 232,000 BTU/hr heat source

That is 232,000 BTUs effectively transferred, not rated, but actually transferred....

I have to work this out in my head... I am astonished...

175,000 BTU burner, if it could transfer 100% of its BTUs (which it cant) running full tilt for 45 minutes. A pound of propane would yield about 22k BTUs, so this would take 6 pounds of propane to run that burner full tilt for 45 minutes, and even then it would not create 3 pounds of vapor per minute. 6 pounds is 1/3 of a 20lb tank, so that is about $5 or more, just to reach a boil, theoretically.

Nothing is adding up here...

My 9000W kettle is only 30k BTUs...
So at 100% eff. and at FULL TILT it can only create .5 pounds not 3 or 4 pounds, but .5 pounds of vapor per MINUTE. But it will heat 12 gallons from 50F to a boil in 35 minutes... with 30K BTUs, which can only create .5 POUNDS of vapor per MINUTE.

It is also running 11 minutes from sparge temp. (160F) to reach a boil. Your test too 3x as long and you are presumably creating 6-8x more BTUs than I am.

 

[kladue]

Take a look at GreenMontis flash boiler and MK-I threads to see the hardware and testing done.https://www.homebrewtalk.com/f51/flash-boiler-153116/,https://www.homebrewtalk.com/f51/mk-i-161799/ With a flowmeter on the water into the boiler we calculated the steam yeild from the boiler, without any leakage between boiler and kettle the heat had only one place to end up. Accuracy of the flow meter at that range could account for some variation in calculated results but bottom line is this moves quite a bit of heat from shrouded burner to kettle. Burner firing may be beyond rating on burner but is not observable as it is inside tube

 

[willynilly]

Okay, after sifting through a few threads that he has running...

He is using a 170,000 BTU burner.
What size is your burner?

I also see that he increased his flow rate in another thread from a max of .25 gallons/min. to about .5 gallon per minute.

So, this begs the question, because I see a lot of numbers being thrown out, but every time I read another page, the numbers change...

How fast is GreenMonti reaching a boil with his 170,000 BTU fired boiler?

 

[willynilly]

EDIT:

There are too many conflicting numbers in the several threads I read on GMs boiler. So, can we post the time to boil and in how many gallons, etc... to get a starting point?

Then I can at least compare that to what you are seeing Kalude. He is using a 170,000 BTU burner, what is yours rated at.

I keep reading that GMs boiler is faster at reaching a boil than electric by a long shot, one referecen is 4x faster than a 4kWh heating element, but I cannot find the actual times, just theoretical BTU transfer.

 

[kladue]

Here is a test run of the coil calandria and 14 gallons of water from cold to boil https://www.homebrewtalk.com/f51/boiling-fb-166785/, maybe this will help. GreenMontis boiler is the current design in testing, my previous boilers have been built from SS tubing and perforance is poor compared to the copper coil version.

 

[willynilly]

I admit, this is some really cool stuff...

So 42 minutes in 14 gallons from 54F to a rolling boil.

So that is an effective transfer of 26,026 BTU/hr or 7.6kWh

The question then becomes, how much gas is the burner expending during that time. Obviously the burner is running at more than 27,000 BTUs

I cant heat much faster than that, I am just under 40 minutes to boil the same qty at the same temps. at a cost of $.57 to reach the boil. It then costs me $.40 to boil off 1.5 gallons over an hour. Total cost to boil then comes to $.97 from a cold start (which none of us really do)

Like I said it is really cool what you all have built, I am curious however how many pounds of LP it will take to perform a 60 minute boil, the resulting BTU usage and the overall cost (eff.) of the setup.

Yall have done a crap ton of work here, and great workmanship... I hope you don't mind me trying to wrap my head around the #s.

EDIT:
After piecing some numbers together from a coupe threads that talked about turns on the regulator, the resulting gas pressure and the associated BTU output of the burner...

It appears that the afore mentioned test was run with the burner at between 75K and 80K BTUs, 1.5 - 2 turns, the resulting heating times and temps indicate about 26K to 27K BTUs to the kettle for heating.

That is an eff. of about 36% which is pretty darned good for a gas fired anything in HBing.

Taking those numbers:

75K BTU/hr for 40 minutes to reach a boil (36% eff, effective BTUs approx. 27,000)
56,000 BTUs expended
2.55 pounds of LP to produce those BTUs
$.92 per pound of LP
$2.34 to reach a boil

Now boiling off the 1.5 gallons per hour will take
1.5 gallons x 8.34lbs per gallon
12.51 pounds of vapor
at 970 BTUs per pound
12,134 BTU/hr heat transfer to boil off 1.5 gallons

Assuming that the eff. of the burner is linear, and that Monti's previous posts are accurate with pressure and BTU useage, 36% assumed eff, the burner output would have to be about 33,000 BTUs over an hour. This is an additional 1.5 pounds of propane.

Total propane useage:
4.05 pounds based on the above information from several threads
$.92 per pound LP
$3.72 for a boil from 54F to 212F and then boiling for an hour with 1.5 gallons/hr boil off.

That is better performance than a straight up gas burner under a kettle from what I have typically seen.

Total BTU usage, using the information at hand, to reach a boil and boil off 1.5 gallons in one hour:
Gas fired steam boil used 89,000 BTUs
DIRECT fired gas boil with typical 25% burner eff utilizing the same burner would use 99,000 BTUs
Electric heating utilizing 9000W to reach a boil and 4000W to maintain a boil used 34,000 BTUs

 

[GreenMonti]

I admit, this is some really cool stuff...

So 42 minutes in 14 gallons from 54F to a rolling boil.

So that is an effective transfer of 26,026 BTU/hr or 7.6kWh

The question then becomes, how much gas is the burner expending during that time. Obviously the burner is running at more than 27,000 BTUs

I cant heat much faster than that, I am just under 40 minutes to boil the same qty at the same temps. at a cost of $.57 to reach the boil. It then costs me $.40 to boil off 1.5 gallons over an hour. Total cost to boil then comes to $.97 from a cold start (which none of us really do)

Like I said it is really cool what you all have built, I am curious however how many pounds of LP it will take to perform a 60 minute boil, the resulting BTU usage and the overall cost (eff.) of the setup.

Yall have done a crap ton of work here, and great workmanship... I hope you don't mind me trying to wrap my head around the #s.

EDIT:
After piecing some numbers together from a coupe threads that talked about turns on the regulator, the resulting gas pressure and the associated BTU output of the burner...

It appears that the afore mentioned test was run with the burner at between 75K and 80K BTUs, 1.5 - 2 turns, the resulting heating times and temps indicate about 26K to 27K BTUs to the kettle for heating.

That is an eff. of about 36% which is pretty darned good for a gas fired anything in HBing.

Taking those numbers:

75K BTU/hr for 40 minutes to reach a boil (36% eff, effective BTUs approx. 27,000)
56,000 BTUs expended
2.55 pounds of LP to produce those BTUs
$.92 per pound of LP
$2.34 to reach a boil

Now boiling off the 1.5 gallons per hour will take
1.5 gallons x 8.34lbs per gallon
12.51 pounds of vapor
at 970 BTUs per pound
12,134 BTU/hr heat transfer to boil off 1.5 gallons

Assuming that the eff. of the burner is linear, and that Monti's previous posts are accurate with pressure and BTU useage, 36% assumed eff, the burner output would have to be about 33,000 BTUs over an hour. This is an additional 1.5 pounds of propane.

Total propane useage:
4.05 pounds based on the above information from several threads
$.92 per pound LP
$3.72 for a boil from 54F to 212F and then boiling for an hour with 1.5 gallons/hr boil off.

That is better performance than a straight up gas burner under a kettle from what I have typically seen.

Total BTU usage, using the information at hand, to reach a boil and boil off 1.5 gallons in one hour:
Gas fired steam boil used 89,000 BTUs
DIRECT fired gas boil with typical 25% burner eff utilizing the same burner would use 99,000 BTUs
Electric heating utilizing 9000W to reach a boil and 4000W to maintain a boil used 34,000 BTUs

Like I have mentioned before (maybe not this thread) I am just learning about all this stuff. BTUs and steam. The info that I posted in my threads is most likely half right. I can't throw this stuff around yet and I am not aware of all the little quirks and what not.You are probably not too far off on those numbers. It certainlly goes along with what is in this thread.

I figure during the actual boil, right now I am using 1 lb for the hour. As you may very well know by reading that info, I ran it for 1 hour at the boiling firing rate and weighed the tank before during and after the run. I have to see what I use for the heating time. From what I understand propane flow rates change when there is back pressure on the system. I can't even fathom that math yet.

Not to worry, I am nipping at your heels. I am working on getting the efficiency up. I would like to get real close to the electric crowd. After all, what's 50 more percent??

 

[GreenMonti]

Here is a test run of the coil calandria and 14 gallons of water from cold to boil https://www.homebrewtalk.com/f51/boiling-fb-166785/, maybe this will help. GreenMontis boiler is the current design in testing, my previous boilers have been built from SS tubing and perforance is poor compared to the copper coil version.

Thank you for posting this. I couldn't find it last night for some reason. It was something to see 14 gallons heat at 6* min at the end.

 

[willynilly]

This thing is really cool Monti, I have actually learned A LOT by reading up on all of this and researching what you are doing over there. I have gained a lot of knowledge not only about your system, but mine as well.

I like to work numbers, numbers are real and solid and mathematics are hard to debunk. Much of this is me trying to get my head around what you have going on over there.

I have found that the eff. of a gas burner increases as you reduce the gas flow rate, so if you used 1 pound of LP for the hour boil, that is 22,000 BTUs and I calculated 34,000 because I do not think that the eff. is a constant, I think it is linear and related to the output of the burner at that time.

I was talking to a friend today who has a degree in physics... although I have no interest in LP boils, I may start working on a jacketed kettle that will trap more of the burners heat against the side of the kettle. Increasing the heating surface area and increasing the contact time of the heat and the kettle bottom and sides. I am interested in what the gains would be over the typical turkey fryer stand.

Anyhoo, I am learning a lot here.

 

[passedpawn]

When I used to use gas, I fantasized about taking a SS tube (keg spear) and welding it to the center of the keg to allow heat to flow up the inside of the wort, as well as around the sides. More surface area, and especially access to the center of the wort, would result in much faster boils I think.

Then I stumbled onto Pol's electric keggle thread...

 

[willynilly]

PP the physics major actually recommended the tube through the center too... accompanied by a a gas (heat) retaining jacket around the outside of the kettle. Increase contact surface area and time.

I may try to get my hands on some sheet metal and fabricate something on my old turkey fryer kettle to see some raw data. I know there will be in increase in performance, just not sure to the degree, and Id like to know!

 

[Cliff897]

What kind of boil? I'd say it all depends.

In your first post in the second video:
That's about the boil I shoot for.

It is not violent, not roiling, not exciting, but definitely rolling.
I want to see the fluid rolling.

The volume of steam generated is not terribly relevant. You will get some steam, but I should think that the wilder the boil the more dark your wort will get. and as a side effect the more evaporation for which you will have to compensate.
You might want the darker color.

 

[springer]

1 BTU to get 1lb of water to rise in temp 1F

13 gallons water is
108 pounds of water

From 60F to 210F:
16,200 BTUs required to heat in an hour
If you have 32.4K BTUs it will take you 30 minutes to accomplish this.

970 BTUs per POUND to create water vapor.
Creating 1.5 gallons of vapor per hour (boil off)
12.5 POUNDS of vapor per hour
12.5 x 970 BTUs per POUND per hour
12,125 BTUs to create 1.5 gallons of boil off per hour

1kW equals 3412 BTUs
12,125 BTUs equals 3.5kW
3.5kW equals 3500W

3.5kWh at $.12 per kWh
$.42 to boil off 1.5 gallons in one hour (unless you are in Hawaii)

Or NY mine is around $.23 . The electricity alone is $.11 and then for each KWH I get hit with a delivery charge of roughly the same amount .. And they are getting a 4% rate hike this year.Wish I had NG at the house