Author Topic: Al vs. SS. Which Heats Faster?  (Read 1315 times)

Offline hopfenundmalz

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Re: Al vs. SS. Which Heats Faster?
« Reply #15 on: November 23, 2010, 11:05:19 AM »
Martin - converted kegs have a skirt, that is what I use for my main pot.

a10t2 - You are probably right, again.  Time to try to see if my results are repeatable when I brew in a day or 2.
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Offline Kaiser

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Re: Al vs. SS. Which Heats Faster?
« Reply #16 on: November 23, 2010, 11:39:08 AM »
I’m with Sean on this one. Getting the heat transferred into and out of the metal is more critical for fast heating.
An interesting idea would be the adoption of the JetBoil design for a brew kettle: http://www.jetboil.com/products/technology where a series of meal fins provide a larger surface for the fire to metal heat exchange. This makes for more efficient use of the heat from the burning gas.

Another aspect of fast heating is even convection in the kettle. This is not necessarily given when we bring wort to a boil. Because all bottom of the kettle is heated evenly the hot wort wants to rise upwards from all these places. Unfortunately the cold wort that is falling down from the top gets in the way and there are many turbulences and the all so familiar sudden rise of large bubbles.

An improved kettle design would heat the kettle only in the middle or offset to one side. By doing so you promote a more even convection of the wort and better heat transfer between kettle wall and wort.  But the more you move the burner off-center, the less heated bottom area you are providing.

Yet another thing that gets in the way of good kettle wall to wort heat transfer is the formation of steam pockets/bubbles on the kettle wall. Those end up creating small spots of insulation between the wort and the kettle wall. That’s what you hear crackling when you are heating the wort. As soon as you stir the wort this crackling goes away since the hot wort close to the heated metal is replaced with colder wort. This is yet another reason why good convection helps with heating wort faster.

All this being said, I brew with a 5 gal SS pot that has none of the enhancements I talked about. Maybe someday when I have a new burner stand I can try off-center heating  to see if it improves convection.

Stirring the wort while heating is an elegant option as well. Especially you have a motorized stirrer which you could also use during the chilling process with an immersion chiller. Or you may want to keep the pump running while you are heating the wort. But make sure that the heat loss in the hoses is less than the gain you should be getting from better circulation in the kettle.

Kai



Offline denny

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Re: Al vs. SS. Which Heats Faster?
« Reply #17 on: November 23, 2010, 11:44:12 AM »
An improved kettle design would heat the kettle only in the middle or offset to one side. By doing so you promote a more even convection of the wort and better heat transfer between kettle wall and wort.  But the more you move the burner off-center, the less heated bottom area you are providing.

I seem to recall hearing a seminar at NHC (maybe Randy or Ray) talking about putting a metal plate under one side of your kettle for just this reason.
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Offline hopfenundmalz

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Re: Al vs. SS. Which Heats Faster?
« Reply #18 on: November 23, 2010, 11:49:10 AM »
Denny - the hear tamer that Randy and Ray talked about was to eliminate hot spots.  Could of had other reasons. I only went to the second one they did in Oakland, and they said they had talked about it in the first.

Kai - I do run my pump when bringing the wort to a boil.  Don't know if it really helps or not.
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Offline Kaiser

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Re: Al vs. SS. Which Heats Faster?
« Reply #19 on: November 23, 2010, 12:36:03 PM »
Martin - converted kegs have a skirt, that is what I use for my main pot.
 

I think what Marting is talking about is more like a 2nd wall for the kettle which provides a small gap. This gap provides some insulation. The skirts on keggles are different and I wonder to what extent they actually make heating less efficient. This is because they trap hot exhaust and prevent this hot gas from flowing across the surface evenly.

So far I got the most energy savings from having a wind shield and keeping the lid on the pot while heating the wort.

Kai

Offline gordonstrong

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Re: Al vs. SS. Which Heats Faster?
« Reply #20 on: November 23, 2010, 12:46:39 PM »
Sounds like to get the best effect, you need an All-Clad brewpot.  Gee, that should be cheap.  A 4-qt saucepan is something like $150.  And worth every penny, if you're a serious cook.  Imagine what a brewpot made like that would cost (or weigh?)

I made a "mash cozy" or insulating wrap for my mash tun out of the aluminized duct wrapping (with the tiny bubbles) sandwiching a fiberglass water heater blanket, held together with duct tape.  It cut my heat loss from around 10F/hr to about 1F/hr.  Looks a little goofy, but it slides over the mash tun with no problem, and I can remove it or slide it up a bit if direct heating.

Kinda makes picnic coolers look attractive.  Just wish you could direct fire them.  Well, more than once.  ;)
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Offline bluesman

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Re: Al vs. SS. Which Heats Faster?
« Reply #21 on: November 23, 2010, 12:57:28 PM »
Martin - converted kegs have a skirt, that is what I use for my main pot.
 

I think what Marting is talking about is more like a 2nd wall for the kettle which provides a small gap. This gap provides some insulation. The skirts on keggles are different and I wonder to what extent they actually make heating less efficient. This is because they trap hot exhaust and prevent this hot gas from flowing across the surface evenly.

So far I got the most energy savings from having a wind shield and keeping the lid on the pot while heating the wort.

Kai


I was thinking the same thing Kai.  I also think Martin was referring to an air gap between the walls. Kind of like double pane windows which are more energy efficient or a thermos for holding coffee. Sounds like we need to ask Blichmann to start working on this one.  ;)

The extra insulation would be needed to allow for more efficient heating but the opposite for cooling. When cooling we would want as much heat transfer as possible.  So it would be a dual purpose design.
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Offline tubercle

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Re: Al vs. SS. Which Heats Faster?
« Reply #22 on: November 23, 2010, 03:58:20 PM »
I have a converted keg brew pot and a 7.5 gallon turkey fryer AL pot.

 Never paid that much attention to heating up but I've noticed cooling is a lot quicker in the AL pot. No scientific numbers to throw out but I guess its the heat loss through the sides thing.
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Offline richardt

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Re: Al vs. SS. Which Heats Faster?
« Reply #23 on: November 23, 2010, 04:16:13 PM »
From an energy efficiency standpoint, I can't disagree with the logic of using coolers for holding the strike water and for mashing.
It also means less propane use and less time listening to the roar of the burners.  Wouldn't you rather listen to your brewing tunes or just enjoy the peace and silence?

Tri-clad SS boil kettles are the way to go to heat strike water/liquor and to boil the wort.
Round or rectangular insulated coolers ar the way to go for maintaining the strike water at desired temps during mashing and sparging and for mashing, as well.
I heat the entire volume of water at the outset.  Once I get to mash-in temps, I add the water amount needed.  I keep heating the rest to the sparging/mash out temps + 10 degrees and then put it in the non-pre-heated 10 gallon Igloo cooler and close the lid.  Propane burner remains turned off for the rest of the mash and until the first runnings get collected.  We're talking a good 45 min to an hour of quiet time.

I think the 2 igloo coolers (10 gallon each) and two SS kettles (one 20 gallons, the other 5.5 gallons--acts as an oversized grant) is a good way to go.  Single tier (on my patio table).  Gravity does all the work.  While I can still lift 10 gallons if I have to, it is easier to use the 5.5 gallon SS kettle (and/or the 1/2 gallon plastic scoop) as the grant.