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How Do I Calculate Thermal Mass

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Tony

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I am building a 3 keg brewing setup and am currently using a 33 liter esky for mashing.

The esky seems to have a thermal mass of about zero acording to promash and the temperatures i achieve.

I was wondering how i would work out the thermal mass of a 50 liter SS keg, complere with false bottom etc. There must be a calculation thet can be done which will factor in the material the vessel is made of, the temperature of the vessel and the weight of the vessel.

Can anyone help with this or can someone who has a similar set-up give me a starting point to work with ??

thanks people.

cheers
 

sosman

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Tony said:
I am building a 3 keg brewing setup and am currently using a 33 liter esky for mashing.

The esky seems to have a thermal mass of about zero acording to promash and the temperatures i achieve.

I was wondering how i would work out the thermal mass of a 50 liter SS keg, complere with false bottom etc. There must be a calculation thet can be done which will factor in the material the vessel is made of, the temperature of the vessel and the weight of the vessel.

Can anyone help with this or can someone who has a similar set-up give me a starting point to work with ??

thanks people.

cheers
The esky absorbs heat so it must have a non-zero thermal mass. My 48L esky is about the same effective thermal mass as 1.5L of water. It is lower than the calculated thermal mass by a significant margin and I have only arrived at that after a few batches.

The thermal mass of a 50L keg would be its weight times the heat capacity of stainless steel. In practice though, the heating is uneven and losses might swamp the thermal mass. IIRC beersmith has a few default setups which might include your own.
 

bradmcm

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ProMash has pretty good helpfiles.

Basically reverse engineer the calculator.

Get your mash water and measure the temp.
Pour it into your mashtun and then remeasure the temp.

In the calculator enter your original temp and adjust the thermal mass until the final figure matches what you got.
 

johnno

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I'm usiing beersmith and have a 48 Qt Igloo which is about 45 litres or so. Anyone out there using the same program care to point me in the right direction about what my setting should be?

cheers
johnno
 

Guest Lurker

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Like Brad says you can experiment with different settings and reverse engineer. But to me it is simplest in any of those software packages to always set the thermal mass to zero. Do only one experiment, drop strike water temp water of about dough in volume in the esky, stir it around, measure the temp drop a couple of minutes later.

Then, after your software gives you the strike water temp (based on zero thermal mass) make your actual strike water temp higher by the amont of the drop you observed.

Its just easier to measure it in terms of temperature drop than converting that to a thermal mass by reverse engineering or whatever.
 

AndrewQLD

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Hi Johnno,

Try this from Beersmith,

Brew Pot (7.5 gal) and Cooler (48 qt)


Batch Size: 21 l Mash Volume: 45.43 L
Boil Volume: 27.28 L
Mash Tun Weight: 4.08 kg
Evaporation Rate: 10.0 % Mash Tun Specific Heat : 0.300 cal/g-deg C
Boil Time: 60.0 Mash Tun Deadspace: 0.95 L
Top-up for Boiler: 0.00 L Equip Hop Utilization: 100.0 %
Losses to Trub/Chiller: 1.89 L Cooling Loss (%): 4.0
Top up water for Fermenter: 0.00 L
Notes: 30 qt (7.5 gal) Turkey Fryer with 48 qt cooler Mash Tun
 

johnno

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Thanks GL and AndrewQld,
looks like i have a few things to try.

cheers
johnno
 

Ash in Perth

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gday. what kind of numbers are people getting for this?

mine ended upo being about 0.35 for promash (assuming ~20L to the first rib) on this system using 1m silicon hose to join the HLT tap to the mash tap to underlet:
http://www.aussiehomebrewer.com/forum/inde...st&p=142898

does this seem about right? it says for a 5kg grain mash at 3L/kg the water will be 78DegC. i want to make sure this seems ok before i mash in tommorow.

Cheers, Ash
 

Stuster

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The thermal mass for my system according to Promash is 0.17. I just have a really basic cooler as mash tun. What mash temp are you aiming for?
 

Screwtop

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gday. what kind of numbers are people getting for this?

mine ended upo being about 0.35 for promash (assuming ~20L to the first rib) on this system using 1m silicon hose to join the HLT tap to the mash tap to underlet:
http://www.aussiehomebrewer.com/forum/inde...st&p=142898

does this seem about right? it says for a 5kg grain mash at 3L/kg the water will be 78DegC. i want to make sure this seems ok before i mash in tommorow.

Cheers, Ash

Have most brewing software here, so ok I'm a software junkie, I like to mess around with software, there are likes and dislikes in all for me to date, but Beertools is getting better and better with Beta revision 14 now available for testing I can't wait, think it may eventually be the most user friendly, IMO anyway.

Have found that to get the same mash in temps with both Beersmith and Promash using same equipment, recipe, volumes and mash schedules that I have to reduce the thermal mass in Promash. When loading my equipment values into Beersmith I used the recommended .300 for a (plastic 0.300) Cooler mash tun. For the same resultant mash in water temp in Promash had to use 0.150. Prior to this my mash temps were too high using Promash, obviously they use different calc formulae.

Ash, you didn't mention your rest temp, so who would know if 78C is OK. Rule of thumb, mash temp plus 9C, amount of water depends on L/Kg you are using. Use your software, later you will be able to fine tune your equipment values from experience. Have some boiling water and frozen water in milk bottles available. Add a little boiling water to up the temp or dunk in a frozed milk bottle for a few seconds to drop your mash temp. Good luck.
 

Ash in Perth

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sorry guys the rest temp is just 66. 78 just seemed very high. its a thick stainless keg so the thermal mass would be considerably more than a cooler so this could be right then. i just dont want the mashg in temp too high. with my old mini setup the strike liquor only needed to be about 70 to get 66 but that was in a thin stainless pot.
 

Stuster

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To avoid that, you could preheat your mash tun then with some boiling water. You may have to guestimate the thermal mass figures then, but after one trial, you should be able to work it out.
 

Chilled

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Using promash, I use a thermal mass of around zero. But I put the required amount of strike H2O into the kettle and connect up pump lines and tun. Heat the water and circulate it from HLT to MLT to HLT etc, while I'm cracking the grain. When everything is at required strike temp ie water, tun, lines and pump I stop circulating, drain all water back into HLT and put the grain in. I then underlett. Usually have good success with doing it that way.
Chilled
 
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