Author Topic: Cooling shrinkage bug?  (Read 3179 times)

Offline Vicente.C

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Cooling shrinkage bug?
« on: May 10, 2017, 12:35:26 PM »
Hi,

First, excuse my bad English!

I have been thinking that cooling shrinkage in beersmith is a bug. If you change the shrinkage from 0% to 4%, the software compensate the "cooling loss" adding more sparge water, this has no sense for me. I don't understand how a shrinkage that it is not a real loss could be affect the total water needed.

In other words, If I set cooling shrinkage to 0% and I measure post-boil volume at room temperature, beersmith suggest use less sparge volume than if I set cooling shrinkage to 4% and I measure post-boil volume while wort is hot. As consequence, pre-boil gravity also change. How these numbers could be correct? Is the same brewing process, the only thing that change is how I measure post-boil volume. Shrinkage is only important if you are going to precisely measure your water at flame out, but should not be influencing total water needed.

Here you can find similar topics:

http://www.homebrewtalk.com/showthread.php?t=290185
http://www.homebrewtalk.com/showthread.php?t=225571
http://www.beersmith.com/forum/index.php?topic=8777.0
https://www.reddit.com/r/Homebrewing/comments/5l4lyk/cooling_shrinkage_and_gravity_in_beersmith/

What do you think about? I hope you can tell me if I'm omitting something important.

 


Offline Oginme

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Re: Cooling shrinkage bug?
« Reply #1 on: May 10, 2017, 06:01:42 PM »
The volumes of sparge water are to be measured at the temperature of addition, which means that the thermal expansion is configured into the volume.  When you set the thermal expansion to zero, it will give you the volume at room temperature effectively lowering the volume predicted. 

If you measure your wort from the mash tun or after pulling your bag of grains (for BIAB brewing) like I usually do, then the thermal expansion becomes a factor in measurement from BeerSmith to actual.  If the volumes were calculated at room temperature, then there would always be an offset in measured (at wort temp) versus the anticipated (at room temp) and the calculation for mash efficiency would also have that offset.

At the end of the boil, BeerSmith backs out the volume for the thermal expansion of the wort because most people measure the volume as volume into the fermenter and excess for trub and loss at room temperature (or close to it).

I have my thermal expansion set at 2.5% which is close to the thermal expansion at mashing temperatures and is where I will do my actual volume measurement of volume from mash and from sparge.

The pre-boil gravity is adjusted based upon the volume of water, which reacts to the thermal expansion value.  This may be, from my process calculations, an issue that should be addressed in the future by calculating the gravity based upon a 'room temperature' volume, especially since gravity readings should always be taken at room temperature (temperature of hydrometer calibration).  In the end, it really is a minor change to most of my brews and the actual error pretty much disappears in the error of my volume measurements with hot wort.

Recycle your grains, feed them to a goat!

Offline Vicente.C

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Re: Cooling shrinkage bug?
« Reply #2 on: May 11, 2017, 03:31:24 PM »
Ok, I understand your point of view. However, there are some issues:

1.  You said that sparge water and pre-boil wort include thermal expansion, but Brad Smith said in other post of this forum that thermal expansion is only included in post-boil volume.

2. If you change the percentage value in cooling shrinkage field, exactly the same "volume loss" is added to sparge water. This is clearly a simple volume compensation and not a thermal expansion of sparge water or pre-boil wort (which should be less than boil volume expansion). 
« Last Edit: May 12, 2017, 11:35:01 AM by Vicente.C »

Offline Oginme

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Re: Cooling shrinkage bug?
« Reply #3 on: May 11, 2017, 05:39:50 PM »
I saw what Brad said in the other post, but there is no other explanation of the strike and sparge volume changing proportionally to the value of the thermal expansion number entered into the equipment profile.  If, as Brad said, the water volumes are not thermally compensated, then they should not change as a function of the thermal expansion coefficient.  I did challenge him on his statement and have not had a response yet.

The mash volume (as full volume biab) changes with a change in the thermal expansion coefficient.  With a traditional mash infusion and sparge, the sparge water changes as the strike water volume is fixed within the mash profile.

In short, there is no other logical explanation for the volumes to change except as a function of thermal expansion and there is no driver for a change other than thermal expansion.

Recycle your grains, feed them to a goat!

Offline gizzygizmo

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Re: Cooling shrinkage bug?
« Reply #4 on: December 24, 2019, 08:13:05 AM »
I've seen the same thing... set shrinkage to 0% and the preboil SG changes.   The math also now works out (preboil SG * preboil volume / post-boil volume = OG).  if you multiply BS's provided preboil volume * SG and divide by post boil volume you will not get your actual OG.  You'll be off by a few points.

The volume "at mash temp" is being accounted for even though we cool our samples for measurement.  I would like to see this bug fixed.  The workaround we've been using is to set shrinkage to 0% and account adjust your pre/post boil volumes manually by multiplying by 103% or 104%.

 

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