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.
“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:
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.
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?
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.
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.
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)
I’m not really a huge fan of BeerSmith. There is a lot of fluff in there. Personal Excel sheets are the way to go in my opinion. There is nothing in BeerSmith that a person couldn’t do in Excel. The Beer Cloud or whatever they call it is not worth the price of admission.
In order to use BeerSmith, you have to customize it to your system or it will give you tons of incorrect information. And yes, it takes into account mash tun mash as a default. That can be changed, as can nearly any other factor. Spending $21 on BeerSmith saved me from having to build yet another spreadsheet (it’s the main part of my day job, which is to say that I don’t want to spend more time on it).
