Thermal expansion?

[LostHopper]

What is the difference in measured volume of boiling wort vs chilled (70 F) wort?

Is it 4-5%?

I hope I asked that correctly. If boiling wort is at the 7 gallon mark in my kettle, what will it measure when chilled to 70 F?

 

[schematix]

1 gallon at room temp will be 1.04 gallons at boil.

If you can measure more accurately than that you can get more precise.

 

[BobBailey]

Four percent from room temperature to boil temperature. You can figure right in the middle of that for mash temperature.

 

[jrgtr42]

Honestly, at homebrew scale, the difference is not worth talking about. When you're looking at commercial level of hundreds or thousands of gallons, then it may become something to think about.

 

[day_trippr]

Well that's just wrong, imo. You don't have to run a megabrewery to appreciate thermal expansion.
Try brewing 10 gallon batches without accounting for volume vs temperature change and your gravities will be AFU...

Cheers!

 

[schematix]

Well that's just wrong, imo. You don't have to run a megabrewery to appreciate thermal expansion.
Try brewing 10 gallon batches without accounting for volume vs temperature change and your gravities will be AFU...

Cheers!

Gravity measurements are always taken at room temp. Even when they're not, they are (or should bee) corrected back to room temp.

As long as you only use room temp volume measurements you don't need to worry about the 4%, assuming you know you don't need the 4% extra space.

I find it very very important for dialing in batch sizes so i can make sure i can get 2 full kegs with minimal waste. Both my pre and post boil volumes are recorded at boil temps so in order to relate that back to kegs i need to know. 4% of wort needed for a 10 gallon batch is almost half a gallon, that's quite a bit to be short by in a keg.

 

[Druman07]

1 gallon at room temp will be 1.04 gallons at boil.

If you can measure more accurately than that you can get more precise.

Good to know.

 

[Big Monk]

Gravity measurements are always taken at room temp. Even when they're not, they are (or should bee) corrected back to room temp.

As long as you only use room temp volume measurements you don't need to worry about the 4%, assuming you know you don't need the 4% extra space.

I find it very very important for dialing in batch sizes so i can make sure i can get 2 full kegs with minimal waste. Both my pre and post boil volumes are recorded at boil temps so in order to relate that back to kegs i need to know. 4% of wort needed for a 10 gallon batch is almost half a gallon, that's quite a bit to be short by in a keg.

^^^^
This!

I hear “shrinkage” talked about as if it were a loss. Expansion and contraction is only used for volume tracking and has no real bearing on anything.

 

[Druman07]

I measure volumes using a ruler dipstick so it does have impact, though very minor. But I feel like I am just a little smarter now..

 

[Big Monk]

I measure volumes using a ruler dipstick so it does have impact, though very minor. But I feel like I am just a little smarter now..

You are spot on.

Tracking volume across the brew day, at temp, with either a ruler or kettle markings, is the only reason to care about expansion/contraction of wort.

 

[Rev2010]

Knowing all this just serves for piece of mind when trying to ensure correct volumes. Taking hops/trub out of the equation for simplicity, if I want 5.2G into the fermenter and I have recorded my boil off rate to be 1.25G per hour that gives me 6.45 gallons volume preboil. At boil however the kettle markings will show a volume of 6.7 gallons. By the time we fully runoff and sparge those preboil numbers are not longer as useful and one needs to account for the expansion if you want to verify your levels. Nothing wrong with him asking this question.


Rev.

 

[Big Monk]

Knowing all this just serves for piece of mind when trying to ensure correct volumes. Taking hops/trub out of the equation for simplicity, if I want 5.2G into the fermenter and I have recorded my boil off rate to be 1.25G per hour that gives me 6.45 gallons volume preboil. At boil however the kettle markings will show a volume of 6.7 gallons. By the time we fully runoff and sparge those preboil numbers are not longer as useful and one needs to account for the expansion if you want to verify your levels. Nothing wrong with him asking this question.


Rev.

Absolutely not. It’s a good question.

I do 1.03 for Mash and 1.04 for boil.

I just always like to clarify that contraction/expansion should not be involved in gravity calcs as a loss.

 

[LostHopper]

Knowing all this just serves for piece of mind when trying to ensure correct volumes. Taking hops/trub out of the equation for simplicity, if I want 5.2G into the fermenter and I have recorded my boil off rate to be 1.25G per hour that gives me 6.45 gallons volume preboil. At boil however the kettle markings will show a volume of 6.7 gallons. By the time we fully runoff and sparge those preboil numbers are not longer as useful and one needs to account for the expansion if you want to verify your levels. Nothing wrong with him asking this question.


Rev.

Thank you rev.

Exactly the reason for my question! I kept coming up a little short into the fermenter and I've been looking at each step of my primitive system to see where I was "losing" volume. Nothing was a major loss or measurement discrepancy but just something I needed to account for so I ended up with the proper post-boil volume.

 

[haeffnkr]

I am scratching my head... I have always had to compensate for expansion.....or at least I thought I had to but not today??

Today I brewed and did not see any expansion or shrinkage, It had been a while since I brewed so just tested my setup with some water.
I put 15 gallons of cold 57 degree water in my setup. 16 inch diameter "extra tall keggle" eBK ... 5500 w element. I watched the whole time... I lost about .25 gallons water by the time I got to boiling. LOST not gain/expanded. I will check it again tomorrow when it cools naturally.

I am at about 600 altitude in MO.

15 gallons x 4% is .6 gallons... I expected 15.6 gallons at the boiling mark .... but stopped the boil at 14.75 Did I loose .6 gallons plus .25 in evaporation?

Today when i was brewing .... my 15 gallon level did not go down when I started the chill.. it stayed at 15, boiling to 40 F

I have a site tube that is calibrated... gallon by gallon.
Any ideas?

thanks haeffnkr

 

[Qhrumphf]

Also important for the oft quoted dilution/boiloff equation, V1*G1=V2*G2.

If your preboil volume is hot and you're using post-chill volume, that math for gravities won't line up.

Either correct for temp, or measure volume at the same temp (immediately prior to boil and immediately after when wort is 210-211 on either end works for me).

 

[Vale71]

I have a site tube that is calibrated... gallon by gallon.

Calibrated at what temp? As the sight tube is attached to the kettle it will heat and cool and therefore expand and shrink with it and the measurement will be inaccurate at temperatures different than what the setup was calibrated for.
Part of the expansion of heated wort is expansion of the wort itself and part of it is due the expansion of the kettle. That's why old breweries who still use copper vessels use slightly different expansion coefficients than those who use only stainless steel kettles.

 

[BobBailey]

There's a problem with you volume measurement(s). Physics wins this argument every time.

 

[haeffnkr]

These pics show what I tested ....

I did not have a starting pic of the temp and level... but the temp of the starting water was 57F and right at 15 gallons on the dip tube/in pot.

To answer the other poster ...The dip tube was calibrated with room temp water...gallon by gallon with a jug of water that measured exactly 8.3X pounds. ..actually it was probably closer to the 57 I used today...tap water/ground water is still fairly cold in MO now. Is the difference of 57 degree water vs 70 degree water X 15 negligible? ... probably not ? But lets proceed.

The current temp after this pot sitting all night is 92 F and the water contracted back to the almost original size.

I lost approximately 1.25 gallons of water due to evaporation due to the hour of heating the water to get from 57 to boiling. Once I got to boiling I turned off the system. It was pretty dry here in MO yesterday ... I saw 27% on my humidity meter once when I looked.
I see AJ has stated more than once about evaporation losses - up to 10% per hour.
https://www.homebrewtalk.com/forum/threads/wort-shrinkage.444052/#post-5695888

AJ says... 15 x . 1 = 1.5 gallons ... I lost 1.25 overall as my evap rate was less than 10% it seems.

but ...
if thermal expansion is 4% over 70F... then 14.75, the amount i had at the end of the short boil 14.75 x .04 = .59 ... so I should have 14.15 in the kettle.. not 13.75... I can only assume the evaporation continued even after the heat was stopped.

I am confident my system did not leak.. but I will check it again today and stat this over again.

I still have not solved the mystery as to why my dip tube level go down after my wort was chilled.

Any holes in these theories? thanks for you help - haeffnkr

 

[Jtvann]

While physics never loses, common sense can win.

Just do an actual full wet test run. Run water water through an entire brew session, keeping track of volumes and specific temperatures used. In the end you can very easily totally negate the losses to cooling by combining that number with system losses.

I'd wager a bet that theres enough discrepancy between the 6 gallon mark on a brew kettle and the 6 gallon mark on the fermenter to be about as much or more than a 4% cooling loss. The only way to be exact is to take actual measurements

 

[mongoose33]

These pics show what I tested ....

I did not have a starting pic of the temp and level... but the temp of the starting water was 57F and right at 15 gallons on the dip tube/in pot.

To answer the other poster ...The dip tube was calibrated with room temp water...gallon by gallon with a jug of water that measured exactly 8.3X pounds. ..actually it was probably closer to the 57 I used today...tap water/ground water is still fairly cold in MO now. Is the difference of 57 degree water vs 70 degree water X 15 negligible? ... probably not ? But lets proceed.

The current temp after this pot sitting all night is 92 F and the water contracted back to the almost original size.

I lost approximately 1.25 gallons of water due to evaporation due to the hour of heating the water to get from 57 to boiling. Once I got to boiling I turned off the system. It was pretty dry here in MO yesterday ... I saw 27% on my humidity meter once when I looked.
I see AJ has stated more than once about evaporation losses - up to 10% per hour.
https://www.homebrewtalk.com/forum/threads/wort-shrinkage.444052/#post-5695888

AJ says... 15 x . 1 = 1.5 gallons ... I lost 1.25 overall as my evap rate was less than 10% it seems.

but ...
if thermal expansion is 4% over 70F... then 14.75, the amount i had at the end of the short boil 14.75 x .04 = .59 ... so I should have 14.15 in the kettle.. not 13.75... I can only assume the evaporation continued even after the heat was stopped.

I am confident my system did not leak.. but I will check it again today and stat this over again.

I still have not solved the mystery as to why my dip tube level go down after my wort was chilled.

Any holes in these theories? thanks for you help - haeffnkr


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If you're not accounting for evaporation then you don't have numbers that are going to be meaningful.

Looking at your setup....keggles. Do you cover the keggles when heating? Two things result--one is they'll heat faster because you're losing heat energy to the creation of steam. Second is you'll get condensation against that lid which can then drip back into the keggle.

All that said, if water is heated from 70F to 212F, it *has* to expand if not enclosed in a pressure vessel. If you're not seeing that in your system, you're either losing a lot to evaporation, or you have a leak, or your measurement system is flawed somehow.

 

[kh54s10]

Beersmith uses 4%. I set that in my equipment profile years ago and have never thought about it again. I find that the rest of the processes are variable enough that there is nothing I do that I need that 4% to work with. I know how much I need to collect preboil to end up with what I want in the fermenter. That still varies by about a quart each time. Sometimes more sometimes less.

 

[Big Monk]

Just a general reminder: thermal expansion is not a gain and thermal contraction is not a loss.

I still see people referring to it as a loss. It’s just a corrective factor for volume.