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Confused about Specific Heat

hotspurdotus

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I'm trying to adjust the specific heat of my equipment profile. I have a 10 gallon Igloo mash tun, and I'm consistently getting mash temperatures that are higher than I expect. I've current got the specific heat set to .25, but I'm getting confused about which way to adjust it.

The mouseover in Beersmith 2.1 says 'a higher number will result in higher infusion temperatures to offset equipment loss'.

The online help on equipment profiles, however, says, Mash Tun Specific Heat - The specific heat of your mash tun - generally this is a number between 0.10 and 0.50 with lower numbers associated with all metal mash tuns such as stainless steel and higher numbers representing plastic thermal coolers.

Am  I crazy or do those two directions contradict each other? Which way should I adjust my specific heat, and are there other settings I can change to ensure I get the proper mash temp?
 
It wouldn't surprise me if the help files contradicted each other.  ::)

What if you change it one way, then update the profile in a recipe, and see which way the infusion temp goes? That is how I did it, just kept adjusting until it matched a few recipes. Not sure if perfection is possible, but I deal with being within 2 degrees currently.

For a 12 gallon Igloo I am at .30 specific heat and 10 pound weight of mash tun. I left the grain heat in the advanced settings st the default for now.
 
Honestly, I would suggest looking first at more-obvious factors that have a bigger impact on that variance, such as water volumes.  Verify all the water additions and any dead space, etc. 

The specific heat numbers "are what they are" and thousands of brewers with similar set-ups use them as given without making changes. 
 
hotspurdotus said:
Am  I crazy or do those two directions contradict each other? Which way should I adjust my specific heat, and are there other settings I can change to ensure I get the proper mash temp?

Nope, they don't contradict.

The longer a material takes to change and adopt a stable temperature, the greater its insulation value. Hence the higher specific heat number. Copper goes very quickly from cold to hot and back to cold again. It is a poor insulator (in other words, a very good conductor). Stainless takes longer to make the transition, so the number goes up, a little. Glass and plastic take even longer to transition, with a cooler having a layer inside its walls that is a very poor conductor of heat. Thus, even larger numbers for them.

But, then there is the question of if you're pre heating that insulation. You need to input the mashtun temperature in your mash profile and check the "adjust temp for equipment" button in the recipe design view. If you uncheck it, then BS only adjusts for the grain temperature.
 
Brewfun, this is not correct. Specific heat is the amount of heat it takes to raise the temperature of a gram of material by 1 degree Celsius. Time is not a factor.

Thermal conductivity is the measure of the insulation property of a material. It measures how quickly heat flows from one area of a material to another.

These two properties are controlled by different characteristics of the atoms or molecules and the crystal lattice in question. 

Thermal conductivity is dominated by the freedom of electrons to move through the material. Interestingly, it is directly related to electrical conductivity... Even though heat and electricity are very different forms of energy. 

Heat capacity / specific heat is driven by the degree of crystalline structure and the mechanical ability of the atoms or molecules to interact mechanically with their neighbors.

There is no general relationship between these two properties of materials. Materials with all combinations of specific heat and thermal conductivity exist.

That said, I agree with your directions for how to solve the problem here.
 
Alternatively, uncheck the "adjust for..." box, and add water to your mlt that is about 10f above the target temperature.  Let the water sit until it cools to the target temperature.  Then dough in. This takes the specific heat of the mlt out of the equation. 

This is my practice.  In actuality, I dough in a few degrees high (5f).  Then I stir the mash until my temp stabilizes at my desired temperature.  Typically, I take a ph measurement and make a ph adjustment (acid addition), so this gives me the thermal leeway for that additional stirring.
 
tom_hampton said:
Brewfun, this is not correct. Specific heat is the amount of heat it takes to raise the temperature of a gram of material by 1 degree Celsius. Time is not a factor.

Thermal conductivity is the measure of the insulation property of a material. It measures how quickly heat flows from one area of a material to another.

(snip)

That said, I agree with your directions for how to solve the problem here.

Well, shoot. Ya got me! Absolutely correct, Tom.

I was trying to simplify and illustrate the seeming contradiction for the original poster, in the same way you succinctly stated it. I over simplified.

The last line of your reply was my goal.
 
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