AL vs. SS myths, time for an experiment.
AL can be used for a boil kettle. No it is ok if seasoned. Busted.
AL causes Alzheimers. This has been Busted by scientific research.
AL will heat the wort faster due to the higher conductivity of the AL over SS. Well how much faster?
The overall heat transfer coefficient is what is important for a system. The system I use is a propane burner, the pot then the wort, so there are 3 heat conductors in series. People on the internet always say that AL will be faster due to the much higher conductivity. If you look on the web you will find the following for AL, and SS.
AL = 250 (W/m-degree C)
SS = 16 (W/m-degree C)
So the AL has greater than an order of magnitude of advantage in heat transfer per unit thickness
So to see how much time I was wasting on a brew day, I was able to do a quick test, since we recently were given a AL pot that as very close to a ss one we had. These are both about 10 quarts, and are very close in diameter and height, you have to get them side by side to see that the AL one is about ¼ inch taller. I thought there would be a small advantage to the AL, for what it is worth, but not enough to worry about.
Both pots were filled with 2 gallons of water. The Aluminum pot was put on first, and the temp was measured with a digital thermometer. Started the time at 110F, since my brother called and interrupted, and went to 200F, just because I was heating some of the sparge water. The AL was taken off and the SS was put on, and the propane valve was not adjusted (30 pounds in a 40 pound tank, so it was running steady). Both were uncovered. So what was the time?
AL = 15 min. 55 seconds
SS = 15 min. 20 seconds
Whoa! What the heck?
One clue is that the digital thermometer was jumping 3 to 4 degrees +/- with the AL pot vs. about 1 degree with the SS pot. The AL pot was even stirred several time while trying to take a steady reading, which should have helped its convection heat transfer. My guess it that the AL pot had higher convection currents out the sides These pots are as high as they are in diameter, so when you do the math, there is 4 times the surface are on the sides than on the bottom. The AL can transfer heat to the wort better in the bottom, but it can lose it faster through the sides.
This is far from a conclusive test, but when someone on a random website says my AL kettle will be faster, I will not lose any sleep. I have some bigger SS and AL pots to try.
AL is faster - Busted? More heating experiments are in order. If you have any data to share, please do. Or just flame me if you want.