Author Topic: Mental Floss  (Read 1713 times)

Offline klickitat jim

  • I must live here
  • **********
  • Posts: 8460
    • View Profile
Mental Floss
« on: November 06, 2015, 06:39:05 AM »
Mark challenged us a recently to know our calculations. Thinking about it, aside from recipe building, the only one I really use on brew day is Strike Water. I'm lazy and use a calculator. But I know that the math is (.2 divided by how many quarts per pound) X (target temp minus grain temp) plus target temp.

That's all well and good, I can memorize it. Occasionally I have to look it up again if I've been using a calculator too long. But it would help retain it and understand it if I knew WHY that calculation works.

Who can explain in layman's terms without more math how that works?

Maybe once we have hashed out strike temp, I'll go after gravity and bittering and color. But one at a time.
« Last Edit: November 06, 2015, 06:41:38 AM by klickitat jim »

RPIScotty

  • Guest
Re: Mental Floss
« Reply #1 on: November 06, 2015, 11:55:18 AM »
Jim, this is a good article that gets into the nuts and bolts of the heat calcs for mashing:

http://byo.com/malt/item/627-feel-the-mash-heat

To paraphrase:

"When you mash grain at room temperature into hot water you are transferring heat from one to the other. The water loses heat to the grain and the grain increases in temperature until the two reach equilibrium. The goal is for the temperature at which equilibrium is reached to be your desired strike temperature. By adding grain at a certain temperature to water at a certain temperature, you can predict the final temp. Precision comes from understanding heat transfer. Every substance you encounter in the mash (grain, water, tun, etc.) has a specific heat constant. Specific heat is the amount of energy in the form of heat required to raise 1 Kg of malt by 1 degree......."

This thread gives some considerable time and energy to the derivation of the equation and it's relationship to Palmer's well known equation from how to brew, which is essentially a simpler heat transfer equation:

http://www.homebrewtalk.com/showthread.php?t=481047

The gentleman notes that the 0.2 constant from Palmer's equation comes from the fact that 20 lbs. of grain has as much specific heat as 1 gallon of water. Therefore 1 lb. of grain has the same specific heat as 0.05 gallons of water or 0.2 quarts of water.

Not sure if any of that helps.

Offline Phil_M

  • Senior Brewmaster
  • ******
  • Posts: 1689
  • Southern Maryland
    • View Profile
Re: Mental Floss
« Reply #2 on: November 06, 2015, 12:03:14 PM »
I'd typed up a response, but I think RPIScotty did a much better job than I did of explaining it. Thermodynamics aren't my strong suit.
Corn is a fine adjunct in beer.

And don't buy stale beer.

Online homoeccentricus

  • Brewmaster General
  • *******
  • Posts: 2008
  • A twerp from Antwerp
    • View Profile
Re: Mental Floss
« Reply #3 on: November 06, 2015, 12:54:10 PM »
For the intellectually challenged who only understand metric, I think the 0.2 constant would be 0.4. Is it correct to say that to heat 1 kg of grain it takes only 40% of the energy required to heat 1 liter of water?
Frank P.

Staggering on the shoulders of giant dwarfs.

RPIScotty

  • Guest
Re: Mental Floss
« Reply #4 on: November 06, 2015, 12:58:11 PM »
For the intellectually challenged who only understand metric, I think the 0.2 constant would be 0.4. Is it correct to say that to heat 1 kg of grain it takes only 40% of the energy required to heat 1 liter of water?

Correct. l/kg is of course the metric parallel to qts/lb.

Online tommymorris

  • Senior Brewmaster
  • ******
  • Posts: 1961
  • Tommy M.
    • View Profile
Mental Floss
« Reply #5 on: November 06, 2015, 01:09:30 PM »
I use a different equation to calculate strike temp.

Ts=Tm+20

Where Ts is the strike temp and Tm is the desired mash temp. Both temps are in degrees F.

This equation is optimized for my system. YMMV.

RPIScotty

  • Guest
Re: Mental Floss
« Reply #6 on: November 06, 2015, 01:15:36 PM »
I use a different equation to calculate strike temp.

Ts=Tm+20

Where Ts is the strike temp and Tm is the desired mash temp. Both temps are in degrees F.

This equation is optimized for my system. YMMV.

The empirical approach!

Offline AmandaK

  • Senior Brewmaster
  • ******
  • Posts: 1850
  • Redbird Brewhouse
    • View Profile
Re: Mental Floss
« Reply #7 on: November 06, 2015, 01:31:39 PM »
I use a different equation to calculate strike temp.

Ts=Tm+20

Where Ts is the strike temp and Tm is the desired mash temp. Both temps are in degrees F.

This equation is optimized for my system. YMMV.

That's what I did. My Sabco equation was Ts = Tm+10. Easy peasy.
Amanda Burkemper
KC Bier Meisters Education Director
BJCP Assistant Education Director
BJCP Master/Mead

Redbird Brewhouse - There's Always a Project
Our Homebrewed Wedding, AHA Article

Online homoeccentricus

  • Brewmaster General
  • *******
  • Posts: 2008
  • A twerp from Antwerp
    • View Profile
Re: Mental Floss
« Reply #8 on: November 06, 2015, 01:33:53 PM »
I use a different equation to calculate strike temp.

Ts=Tm+20

Where Ts is the strike temp and Tm is the desired mash temp. Both temps are in degrees F.

This equation is optimized for my system. YMMV.

That's what I did. My Sabco equation was Ts = Tm+10. Easy peasy.

You unmetric guys [EDIT: and gals]  are so lucky...  :(
Frank P.

Staggering on the shoulders of giant dwarfs.

RPIScotty

  • Guest
Re: Mental Floss
« Reply #9 on: November 06, 2015, 01:35:34 PM »
I use a different equation to calculate strike temp.

Ts=Tm+20

Where Ts is the strike temp and Tm is the desired mash temp. Both temps are in degrees F.

This equation is optimized for my system. YMMV.

That's what I did. My Sabco equation was Ts = Tm+10. Easy peasy.

While the empirical approach is best given the disparity of everyone's systems, Jim I think was concerned with the theoretical aspects.

Online tommymorris

  • Senior Brewmaster
  • ******
  • Posts: 1961
  • Tommy M.
    • View Profile
Re: Mental Floss
« Reply #10 on: November 06, 2015, 01:40:30 PM »

I use a different equation to calculate strike temp.

Ts=Tm+20

Where Ts is the strike temp and Tm is the desired mash temp. Both temps are in degrees F.

This equation is optimized for my system. YMMV.

That's what I did. My Sabco equation was Ts = Tm+10. Easy peasy.

While the empirical approach is best given the disparity of everyone's systems, Jim I think was concerned with the theoretical aspects.
But mine is easier to memorize.

Online tommymorris

  • Senior Brewmaster
  • ******
  • Posts: 1961
  • Tommy M.
    • View Profile
Mental Floss
« Reply #11 on: November 06, 2015, 01:43:01 PM »
PS. Thanks for sharing the theoretical info. I do maintain a spreadsheet where I have input all the math and I agree with many that it helps understanding.

That being said, this particular equation (strike water calc) never worked for me where the empirical approach is very reliable. So eventually I updated my spreadsheet to use the empirical equation.

RPIScotty

  • Guest
Re: Mental Floss
« Reply #12 on: November 06, 2015, 01:44:29 PM »
PS. Thanks for sharing the theoretical info. I do maintain a spreadsheet where I have imputed all the math and I agree with many that it helps understanding.

That being said, this particular equation (strike water calc) never worked for me where the empirical approach is very reliable. So eventually I updated my spreadsheet to use the empirical equation.

And that is the point. Theory often makes assumptions and simplifications to make the math easier. Theory should drive the empirical approach. The theory gets you in the ballpark, your notes and observations gets you the results.

Online homoeccentricus

  • Brewmaster General
  • *******
  • Posts: 2008
  • A twerp from Antwerp
    • View Profile
Re: Mental Floss
« Reply #13 on: November 06, 2015, 02:04:24 PM »
Beersmith must still be using another formula. When I compare Bs with the formula mentioned here I get almost 1C difference... (formula gives higher result)
Frank P.

Staggering on the shoulders of giant dwarfs.

RPIScotty

  • Guest
Re: Mental Floss
« Reply #14 on: November 06, 2015, 02:15:24 PM »
Beersmith must still be using another formula. When I compare Bs with the formula mentioned here I get almost 1C difference... (formula gives higher result)

Which equation?