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.
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.
Last edited by willynilly; 03-22-2010 at 09:21 AM.
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.
Last edited by willynilly; 03-22-2010 at 03:22 AM.
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.
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.
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.
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.
Last edited by willynilly; 03-22-2010 at 08:56 AM.
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.
Last edited by willynilly; 03-22-2010 at 09:28 AM.
Take a look at GreenMontis flash boiler and MK-I threads to see the hardware and testing done.http://www.homebrewtalk.com/f51/flash-boiler-153116/,http://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
Linear Mode
