loss calculation

[robange]

Does this make sense:

I did a test. i boiled 5 gallons of water to determine evap loss. I lost 1.1 gallons before chilling and then an additional .29 when cooled. Total loss of 1.39 gallons. If Im going for 6.5 gallon batches does the math 1.39 / 5 = .278

which gives me a per gallon loss. So if im doing 6.5 gallon batches I should be able to multiply 6.5 x .278 = 1.807 gallon loss.

Does this math work?

 

[944play]

I'd think that at the same rate of heat (say, 20,000 btu) you'd get a similar amount of boiloff but a proportional thermal expansion, which should be around 4%.

(6.5 - 1.1) x 0.96 = ~5.2

 

[Yooper]

Right- you won't boil off more (or less) with a different amount of liquid in the same pot if you use the same amount of heat. So whatever you boiled off when you did a 5 gallon boil is what you'll boil off in a 7 gallon boil. You MAY have a light difference in cooling shrinkage, but it should be minimal.

When I make a 10 gallon batch, I start with 12 gallons. When I make a 5 gallon batch, I start with 7 gallons. I "lose" 2 gallons over the course of the boil plus what is left behind in trub. That never changes/

 

[robange]

So no matter what my loss is going to be 1.39, whether i do 5, 6.5 or 8 gallon batches. correct?

 

[robange]

actually that seems pretty clear, thnx for the input.

 

[Yooper]

So no matter what my loss is going to be 1.39, whether i do 5, 6.5 or 8 gallon batches. correct?

Yes. It may vary slightly due to shrinkage during cooling, but not that much.

 

[robange]

thank you