Beer Tools Pro - Cooler Calibration Problem

[erykmynn]

Well I did post this over at the BTP forums, but they look like they're pretty sparse traffic and there seems to be a good number of people over here using it.

I'm trying to get my Mash Tun calibrated, after missing various targets on mashes several times. Obviously sometimes I could just "preheat" and go for it, but that doesn't really help if there is more to do.

So I have a 10 gal rubbermaid:

width 12.5
length 12.5
height 18.8
capacity 10.0 gal
dead space 0.3 gal
heat capacity: 4646.0 j/kg k
heat xfer coefficient 2.98 w/m2 k

environment 65 F
infusion volume 5 gal
infusion temp 180.4 F
5 minutes 174.0 F
65 minutes 165.5


Now I know from experience that once equalized, this thing will only drop 1-2 degrees in an hour. People say they "tweak" their numbers, but how can I be comfortable mashing first at a temperature prescribed by something that has the thermodynamics so out of whack as to predict 7-8 degree drops in temperature?! And even if I can be comfortable as to hitting my strike temp, how do I begin to adjust it, so as to get in in the ballpark finally?

 

[Blindguardian]

I know what you mean, I am on the same lines as you when it comes the calibration temps of my equipment.
Another thing that might get you to thinking is this, the grain holds in heat so how can you get an accurate calibration of your cooler just using water?

That is what get me and puts doubt in my mind. So I am thinking would it not be better to calibrate the cooler while doing an actual mash if you do only sertian size batches with about the same amount of grains?

 

[erykmynn]

unless you were just "fudging" the numbers somehow with a recipe/schedule open, calibrating with a mash wouldn't be super accurate either I'd think because the amount of grains varies...

Also, looking at some of the other packages and calculators, they look for "thermal mass" which I have guesstimated is in the 2 1/2 - 4 lb range for the rubbermaid. The "specific heat" in beer tools pro should be "per-unit" value, but I don't understand how that can work if you don't enter the mass also...

 

[dr_finklestein]

I use a 10 Home Depot (Rubbermaide) water cooler and my mash temps are pretty consistant. I pre-heat it with .75 gal of 190* water, dump, and then add my mash water. Once I add the grains, cover the lid and most of the cooler with a down blanket, I get pretty consistant mash temps (only dropping .5*)

 

[Bobby_M]

Was the cooler sitting in that 65F environment for a few hours before you tested or was it in a colder garage overnight right before?

I've found that the MLT will definitely lose more heat without the grain, even with total volume considered. The way to tweak it is to fake the numbers on the 65 minute mark with a slightly higher temp. The last batch I did was with a 65m number 2F warmer than it calibrated at and it was accurate.

 

[erykmynn]

Was the cooler sitting in that 65F environment for a few hours before you tested or was it in a colder garage overnight right before?

I've found that the MLT will definitely lose more heat without the grain, even with total volume considered. The way to tweak it is to fake the numbers on the 65 minute mark with a slightly higher temp. The last batch I did was with a 65m number 2F warmer than it calibrated at and it was accurate.

65 environment the whole time. Sometimes the kitchen is warmer but the storage room is solid 65.

Thanks Bobby, that is essentially what I did, and I brewed an Oatmeal Porter this weekend that hit the temp marks from my "adjusted calibration" pretty well. Unfortunately my fittings were a little loose when I was decanting water in my cooler (but not during the mash) so there was some extra thermal mass in there to keep things interesting, but after another mash I should be really dialed in.

It also took a while to realize that a lot of my frustration earlier was that I was changing the parameters on the "Database" version of my Tun and that didn't automatically update the "recipe" version. It took several rounds of trial and error to figure that out, but what a relief!

Now I wonder if anyone has had success doing multiple infusions in a cooler once it's been calibrated.....

 

[Bobby_M]

Make sure you save all your settings as a template which can save vessels, heat source, and all other kinds of data. The workaround to that is to always use the last recipe file and modify for the next. The upside to using templates is if you screw up and start a new recipe from scratch or get one from someone else, you can retroactively load the template data on top of the recipe.