Need a good boil off rate to start with.

[autonomist3k]

I'm using an 8 gallon 14" wide aluminum pot to brew today and don't have time (or propane) to calculate my boil off rate, I was wondering if anyone with similar equipment could give me a ball park idea of what my boil off rate will be? I live in a pretty warm climate, (sacramento) if that helps.

My keggle's boil off rate here is 1.5 gal/hour, I suspect that it would be different with my aluminum pot though.

I'm using the smaller pot because I'm doing a small batch and the dead space in my keggle would kill my brewhouse efficiency.

 

[william_shakes_beer]

Aluminum VS SS is irrelevant. It's the vogor of the boil and surface area of the kettle. If you want less boil off, reduce the heat to a simmer after it reaches 212. I have a 15 gallon blichman and at a gentle simmer it boil soff 1 gallon per hour. Mty 7.5 gallon turkey fryer boils off 3/4 gallon per hour on the stovetop.

 

[rodwha]

Isn't a vigorous boil necessary or ideal?

 

[autonomist3k]

AL conducts heat differently than SS, so I figured it would effect the boil off rate.
I've also read that the surface area of the pot affects it.
I have a marking that I use on my propane regulator so I'll be boiling the same as I always do.

 

[sportpak]

http://sigginet.info/brewing/tools/boil-off-calculator/

This should get you close, but you won't know for sure until you run a batch or two on your setup.

 

[autonomist3k]

Just ran the numbers on that calculator and I don't trust it, it was off by a half gallon for my keggle.
Maybe adding the specific btu's into the calculation would give a better idea. I'm pretty sure climate affects it also.

 

[Auger]

AL conducts heat differently than SS, so I figured it would effect the boil off rate.
I've also read that the surface area of the pot affects it.
I have a marking that I use on my propane regulator so I'll be boiling the same as I always do.

The material difference would affect how much heat/energy is required to maintain a given temp/boil rate, but assuming all else is equal, shouldn't affect the boil off rate. Surface area will have a much greater effect.

 

[autonomist3k]

I guess as long as your boil vigor us the same, the type of metal doesn't matter, makes sense.
But the diameter difference will have a different water surface area for evaporation to take place, so if the diameter is the same, the boil off rate should be the same.
Good talk guys, I think I got it.
Thanks.

 

[dkevinb]

Sounds like you already have an answer, but my 14" diameter 8-gallon aluminum pot boils off about a gallon an hour on a turkey fryer in coastal SoCal. That's pretty much what the calculator said, too.

 

[autonomist3k]

Awesome, that's pretty much my situation, thanks!

 

[autonomist3k]

In case anyone is wondering, I boiled off about 1.4 gallons.

 

[dkevinb]

In case anyone is wondering, I boiled off about 1.4 gallons.

What's your humidity up there right now? Kid #1 lives in Fresno, and I know it's hot and nosebleed dry there. We're hotter than normal, but more humid than normal here in the Newport Beach area. Humidity will have a big impact on boil off.

 

[autonomist3k]

Humidity was probably around 26%

 

[dkevinb]

Humidity was probably around 26%

Oof. Nosebleed. We're around 75% at the moment. My guitars are going crazy. We're not used to this humidity. It's normally around 50%.

 

[Btaz]

I have been trying to figure this out as well as I have some new kettles. I've looked at other tools and never could figure out what went into the calculation. The % tools always seemed funny/incorrect as the rate doesn't really change with how much water you have. Also, when people have reported their rate you never really know what temperatures or how they measured their volumes (water expands ~1.5% from room temp to near boiling) and how accurate they might be (I know I'm just eyeing things in the 0.25 gal range). Also, the loss is a heat in / heat out equation so the type of burner and inefficiencies really make a difference which can change some setup to setup. I have a little tool, untested, that seems to come out with reasonable answers compared to other tools. With this at least I know what goes into it.

If you are curios take a look and see if it gives you a reasonable results. It isn't too refined and pretty messy for now, but to give you some clues, fill in the kettle and burner info and the boil off rate is on around row 180. I'm interested to see how well my calculations go. Somethings to note, I don't take humidity into account as from what I've read it makes almost a negligible difference. Also, I don't take windspeed into account as this can affect the burner efficiency, for now I just allow for user input as to their estimation of efficiency. And there are a lot of other things in there that I'm thinking about and working on that don't pertain to this topic.

Brewing Size Calculations.xlsx