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Home Brew Forums > Home Brewing Beer > All Grain & Partial Mash Brewing > Mash Tun Thermal Mass
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Old 04-14-2009, 11:50 PM   #1
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Default Mash Tun Thermal Mass

I was looking at the members' gallery and saw a picture of one of the brew calculators. Don't know which it's from since I don't have either BrewSmith or ProMash. It was the Dough In Mash Strike Temp Page, and at the top of the column there was an entry space for "Mash Tun Thermal Mass". Does anyone know the mttm of their equipment or know how to calculate it? Knowing this variable would take pre-heating the mash tun out of the picture. Would this info be available from the cooler or kettle manufacturer? Seems rather esoteric, but since we deal in a lot of esoterics anyway.....I thought some of you tech-heads would know this.

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Old 04-15-2009, 02:08 AM   #2
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If you use ProMash, it will tell you what your thermal mass is. It will give you options on different types of MLTs and tell you what a good starting point is for your thermal mass.

Honestly, I dont trust that stuff, why? Here is why. If yo use a set value for say, a beverage cooler... here is what happens.

Your water will have to be hotter if you start with a cooler that is 55F than you will if the cooler is at 80F, right? Simple thermal dynamics. So how can you possibly use a coefficient that is a set value when dealing with a dynamic situation? This is odd, yes?

Therefore, I heat my strike water to strike + 15F. This is plenty to preheat the tun, the water cools to strike temp, then you mash in.

Grain temp, strike water temp, MLT temp... there are so many variables, a simple coefficient will not suffice. It is closer, but still a wild guess.

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Old 04-11-2010, 04:16 PM   #3
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I use a cube beverage cooler as my mash tun, and the way I run my mash is as follows:
I start heating my strike water, aiming about 15-20 degrees higher than the target temp. While that's going, I quickly bring a gallon of water to a boil and throw it in the cooler, close the lid, and let it get nice n' steamy. WHen my strike water is at temp, I dump the formerly boiling gallon, toss in the grain, and add my strike water quart by quart until I'm sure there's no dough balls, at which point I pour in the rest of the strike, give it a good stir, and adjust the temperature with a little bit of hot or cold.

I always wonder about the thermal mass too, but in reality, it's only a practical number for large commercial breweries. If they miss their strike temp, that's a batch that's inconsistent with the others, and probably ruined. For the homebrewer, what's a degree or two?

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Old 04-12-2010, 08:20 PM   #4
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Arriving at the proper mash temperature appears to be my bête noir since switching to AG last June. I dislike using brewing software, and I can't see why there isn't some easy way to plug in an approximate thermal mass of a cooler (which ought to be about the same for any insulated cooler of the same size), the mass of the grain, either assume an ambient or preheat temperature, and arrive at a temperature for the strike water that will give a mash temp +/- 1 degree. Or maybe I'm missing something.

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Old 04-12-2010, 08:36 PM   #5
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From http://promash.websitetoolbox.com/post?id=1790768

You can calculate this yourself using ProMash.

  1. Go into ProMash and open the Strike Temp calculator.
  2. For Mash Tun Thermal Mass, Enter 0.
  3. For Total Grain enter 0.00001 pounds. (It won't let you go any smaller - entering 0 will give you a division error.) This should make your water:grain ratio 120000:1.
  4. For Total Water, enter 16.00 quarts.
  5. For Desired Strike Temp, enter 170. (You can use any temperature but this will more accurately reflect actual mash temperatures.)
  6. For Grain Temp, enter the current room temperature.
  7. Heat 16 quarts (4 gallons) of water to 170 degrees and pour it quickly into the mash tun. Close the lid and seal it up, and let it sit for about 5 minutes.
  8. Measure the temperature of the water in the mash tun.
  9. Enter the temperature of the water in the mash tun in the "Desired Strike Temp" field in ProMash.
  10. Now look at the "Initial Strike Water Temp Should Be" window. You will note that, with Thermal Mass set to 0, this number will be the same as the "Desired Strike Temp" field.
  11. Now, in small (say 0.1 or smaller) increments, increase the Thermal Mass field until the "Initial Strike Water" field reads 170 (or whatever temperature you started with, if you didn't use 170 for some reason.).
  12. Ta-da! Whatever the Thermal Mass field says is your mash tun's thermal mass!

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Old 04-12-2010, 09:23 PM   #6
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I guess what I'm saying is that sure, you can calculate the thermal mass of you mash tun, but is it going to help you brew award-winning beer? No. Ingredients, creativity, and cleanliness have more impact than a number most of us don't even know anything about ever will.

Thermal mass is analogous to mass in the tradition sense - mass resists a change in acceleration, thermal mass resists a change in temperature, and is given in units of energy per delta temperature. This number, also called the thermal capacitance, will tell you how many Joules (units of energy) it takes to raise the temperature of 1g of a material by 1 degC. So, by extension, the thermal mass of your mash tun is how much energy you need to input into the system to raise the entire system to the desired temperature, and depends on ambient temperature, amount of grain, and obviously the thermal mass of the entire system.

So yes, calculate away! Just saying that it'll just be faster to add a quart or two of boiling or cold water to get your temperature right than it is to fiddle with complicated equations all day. That being said, I'm a science nerd and will probably run home and calculate it anyway, just to satisfy my curiosity... RDWHAHB!

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Old 04-13-2010, 04:41 AM   #7
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Quote:
Originally Posted by The Pol View Post
If you use ProMash, it will tell you what your thermal mass is. It will give you options on different types of MLTs and tell you what a good starting point is for your thermal mass.

Honestly, I dont trust that stuff, why? Here is why. If yo use a set value for say, a beverage cooler... here is what happens.

Your water will have to be hotter if you start with a cooler that is 55F than you will if the cooler is at 80F, right? Simple thermal dynamics. So how can you possibly use a coefficient that is a set value when dealing with a dynamic situation? This is odd, yes?

Therefore, I heat my strike water to strike + 15F. This is plenty to preheat the tun, the water cools to strike temp, then you mash in.

Grain temp, strike water temp, MLT temp... there are so many variables, a simple coefficient will not suffice. It is closer, but still a wild guess.
Fascinating.
I would guess that Promash and Beersmith assumes that the temperature of the MLT is the same as your grain temperature. If that is the case, then a simple constant should be enough to calculate the strike water temperature.
The problem with this is that nowhere in Promash that I have found does it ask for the mass of the MLT, and without that knowledge it cannot possibly calculate an accurate strike temperature.
In contrast, Beersmith does ask for the mass of the MLT, so in theory should be able to calculate the strike temperature more accurately.
I put the same recipe into both Beersmith and Promash. 9.75 lbs grain at 56F 9.75 qt water in a 10g gott cooler with a thermal mass of 0.3 to hit a mash temperature of 152F
Beersmith came up with a strike temperature of 174F, and Promash with 181F.
I have no idea which is more accurate because I always preheat my MLT and add grain to water, but one will result in a mash temperature about 5 to 6 degrees greater than the other.

Quote:
Originally Posted by swankyswede View Post
So yes, calculate away! Just saying that it'll just be faster to add a quart or two of boiling or cold water to get your temperature right than it is to fiddle with complicated equations all day.
Have you ever tried this? I have. After ending up with a low mash temperature, I added boiling water, overshot, added cold water, overshot, added boiling water, overshot etc. By the time it was all sorted out, I had the right mash temperature, but the water to grain ratio was totally screwed up, as was the character of the beer.

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Old 04-13-2010, 01:06 PM   #8
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Quote:
Originally Posted by ajf View Post
Have you ever tried this? I have. After ending up with a low mash temperature, I added boiling water, overshot, added cold water, overshot, added boiling water, overshot etc. By the time it was all sorted out, I had the right mash temperature, but the water to grain ratio was totally screwed up, as was the character of the beer.
It's the way I always brew - I preheat the tun cooler with boiling water for about 15 minutes, heat my strike water to +15 degF target, add water to grain, then adjust accordingly. I usually hit within 2 degF of the target with the strike, so it only takes a little bit of hot or cold to get it right on.
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Old 08-05-2011, 04:53 PM   #9
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Quote:
Originally Posted by swankyswede View Post
I guess what I'm saying is that sure, you can calculate the thermal mass of you mash tun, but is it going to help you brew award-winning beer? No.

It's helped my brew award winning beer by making sure I hit accurate mash temps more easily.
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Old 08-05-2011, 05:51 PM   #10
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Quote:
Originally Posted by Denny View Post
It's helped my brew award winning beer by making sure I hit accurate mash temps more easily.
That's fantastic! A more controlled process gives more predictable results. I live in the wildly swinging temperatures of the Northeast, where it can be 65 and dry one day and 95 and sticky the next, and because I brew outside, it's hard to adjust for such drastic temperature changes. My system of getting in the neighborhood of my mash temp and adjusting once I've hit what I'm gonna hit has worked so far, and I personally would rather get outside and brew some beer than calculate to the tenth of a degree what my strike water should be.

Everyone has their system; fired false bottoms and sparge arms with a RIMS system work great for some, and a homemade cooler with holes poked in aluminum foil and a measuring cup work great for others. For your average homebrewer, this number is something they can ignore safely, and I've done so for 5 years with no ill effects. If calculating it is your jam, by all means grab your pencil and TI-83 and calculate away. Satisfying your intellectual curiosity is never a bad thing, and if it's in service of making a beer that tastes great and wins awards, huzzah!

I've worked myself up into a powerful thirst, time to go make sure that saison i've got in my keg is still tasty...
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