Add volume under false bottom setting

In the formula desitter came up with, he is assuming that the water under the false bottom does not lose heat to the grains, and this is false.  Even though it does not contact the grains directly (assuming that you add the water first and then the grains), the temperature will equalize in your mash tun.

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While you're not wrong about the mixing, my formula does take this equalization into consideration, and my comment does make sense when you think about the problem a little differently.

Try this, two volumes, Va and Vb are the volume of the mash water above and below the false bottom respectively. If I was to just mix the volume Va, at some calculated temperature Ta, with the grain (at temp Tg), then the mixture would equalize at a temperature Tt (lets say my target mash temperature) which is a function of Ta and Tg. If I then mix this volume with the volume Vb which is also at temperature Tt, the temperature of the new mixture would remain at Tt, as I am neither adding hotter nor colder water. But I am still accounting for the volume beneath the false bottom. Hence "the volume under the false bottom does not lose heat to the grains" is correct in this context, as the above volume and grains have already equalized to the same temperature as the below volume.

The formula uses this reasoning, but instead determines the strike water temperature required as a single infusion, rather than the multiple infusions at different temperatures given in the example above. It then uses this strike temperature to derive a new strike water temperature that also allows for heat lose due to the volume of your mash vessel in contact with the mash (if anything needs adjusting for accuracy due to heat dissipation it's this, but for simplicity sake, and to do it just as BeerSmith does, I left it like this).

The main concern I have, and I think many others do too, is that we are not getting our desired water-to-grain ratio due to part of the strike water volume being below the false bottom, and hence the mash becomes thicker. Although minimal changes in the water-to-grain ratio likely have little effect, I'm still concerned by the lack of consistency when varying the amount of grain. It may be true what you say with regards to the higher water-to-grain ratio mash efficiency increase offsetting the lower efficiency due to less sparging with larger grain bills, but I think the software should at least attempt to model what is really happening, and strive for accuracy if at all possible, especially in this case when it is a relatively simple addition to make.

Another easy quick trick in two easy steps.

For reference, my mash tun has an unrecoverable dead space of 0.25g, but the total volume under my false bottom is 2.75gal, thus 2.5 gallons are recoverable wort that will go into my boil kettle.

1) In the volumes tab for your Boil Kettle Equipment, Adjust the profile so the Kettle Top Up Volume is the actual unrecoverable dead space subtracted from the total Volume under the false bottom. In my case, that would be 2.5gallon. (2.75g - .25g = 2.5g, thus Kettle Top Up would be 2.5g)

2) Back in your recipe add the actual total volume under the false bottom in your recipe. In my case, 2.75gallons.


Now, your recipe will automatically deduct the correct volume from the sparge water and automatically account for the true unrecoverable dead space. This is assuming of course that you have already set your batch volume as well. This should also leave your efficiency settings the same as well.

Hope this helps.

Is this in the pipe line to be updated ?

desitter said:

Just adding my solution to this problem should anyone else stumble upon this post.

1.) Enter your correct deadspace (the actual water lost to the mash/lauter tun, not the volume under your false bottom) in the "Tun Deadspace" field of the mash profile.
2.) Tick Adjust Mash vol for Deadspace
3.) Enter your desired Water-to-Grain ratio as part of the strike mash step. Note the suggested water to add, and temperature at which to add it.
4.) Use the formula below to calculate a new Water-to-Grain ratio that includes the volume under your false bottom.

New ratio = [Suggested volume (step 3) + Volume under false bottom - Tun Deadspace (step 1)] / weight of grain

5.) Replace your desired Water-to-Grain ratio from step 3 with this new ratio.

The new Water-to-Grain ratio will now ensure that the updated strike volume fills the volume under your false bottom, while ensuring the volume above the false bottom that contacts the grains is still your desired ratio from step 3 + that added by ticking "Tun Deadspace". The given sparge volume will be correct, and the infusion temperature will be in the ball park (slightly off as the additional false bottom water is not in contact with grain to cool it). You could simple add all but the false bottom volume at the temperature recorded in step 3 (ignoring the strike temperature given with the new ratio), and the false bottom volume at the desired mash temperature. But I doubt it will really be an issue.

Example:
Batch size - 20.8 L, 60 min boil
7.73kg grain at 22.2 C
Targeted 65 C strike temp
Desired 3 L/kg Water-to-Grain ratio, with 7.75 L absorption
4L under false bottom
1L tun deadspace, 1.9L lost to both trub
4.21L/hour boil-off

Suggested strike volume is 24.2L, hence -
(24.2 + 4 - 1) / 7.73 = 3.52 new Grain-to-Water ratio

Using all the values given to me by beer smith:
New strike volume will be 28.23L at 70.6 degrees C (single infusion, light body, no mashout), with a sparge of 8.34L.
Pre-boil volume = 28.23 + 8.34(sparge) - 1(deadspace) - 7.75(absorption) = 27.82 L
Volume into fermentor = 27.82 - 4.21(evaporation) - 0.94 (shrinkage) - 1.9(trub) = 20.8L

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desitter I think this is the right way to approach the issue. The amount you enter for the tun deadspace should only reflect what you cannot recover. It does not matter whether the water underneath your false bottom is in direct contact with the grist. There are two effects at work:

1. Most brewers will stir the mash.
2. More importantly, even without stirring there is a lot of "movement" going on in the mash tun because of the water temperature (as in heat = fast moving molecules). So the mash thickness should be calculated based on the overall amount water in the mash tun, not only the amount of water that's above the false bottom. I think a good way of thinking about this is comparing the process to steeping a tea bag in a cup. Although the tea bag itself is only in direct contact with a small amount of surrounding water, the tea will diffuse after a little while because of the water temperature.

Therefore, if we want to get equal runnings from a one step batch sparge the second step should entail filling up the tun again with exactly half of the expected boiling volume and then completely draining it.

The first step should account for the real tun dead space (as in wort that cannot be recovered), the water absorption of the grain, and the amount of first runnings, i.e. half of the intended boiling volume. Note that if you are aiming for a certain water to grain ratio you can achieve this as outlined by desitter by mashing at that ratio (taking into consideration absorption and deadspace) and then filling up the mash tun so you get half of the boiling volume just before draining.

Now there's another problem with how beersmith calculates the deadspace. It adds one half of the entered amount to the first and second steps respecetively irrespective of ticking "Adjust mas vol for deadspace". I think this is a mistake as the whole deadsapce should be added to the first step because it is in fact not recoverable.

So overall I think we need two adjustments in the program

1) the tun deadspace should be accounted for in the mash thickness calulation and
2) the deadspace should be attributed to the first step only.

I would really really like to get a reply to this request as I think that beersmith is a great tool but this batch sparging issue, which many people stumble over is a flaw, especially since many rely on batch sparging because of its simplicity.

rippler said:

desitter said:

Just adding my solution to this problem should anyone else stumble upon this post.

1.) Enter your correct deadspace (the actual water lost to the mash/lauter tun, not the volume under your false bottom) in the "Tun Deadspace" field of the mash profile.
2.) Tick Adjust Mash vol for Deadspace
3.) Enter your desired Water-to-Grain ratio as part of the strike mash step. Note the suggested water to add, and temperature at which to add it.
4.) Use the formula below to calculate a new Water-to-Grain ratio that includes the volume under your false bottom.

New ratio = [Suggested volume (step 3) + Volume under false bottom - Tun Deadspace (step 1)] / weight of grain

5.) Replace your desired Water-to-Grain ratio from step 3 with this new ratio.

The new Water-to-Grain ratio will now ensure that the updated strike volume fills the volume under your false bottom, while ensuring the volume above the false bottom that contacts the grains is still your desired ratio from step 3 + that added by ticking "Tun Deadspace". The given sparge volume will be correct, and the infusion temperature will be in the ball park (slightly off as the additional false bottom water is not in contact with grain to cool it). You could simple add all but the false bottom volume at the temperature recorded in step 3 (ignoring the strike temperature given with the new ratio), and the false bottom volume at the desired mash temperature. But I doubt it will really be an issue.

Example:
Batch size - 20.8 L, 60 min boil
7.73kg grain at 22.2 C
Targeted 65 C strike temp
Desired 3 L/kg Water-to-Grain ratio, with 7.75 L absorption
4L under false bottom
1L tun deadspace, 1.9L lost to both trub
4.21L/hour boil-off

Suggested strike volume is 24.2L, hence -
(24.2 + 4 - 1) / 7.73 = 3.52 new Grain-to-Water ratio

Using all the values given to me by beer smith:
New strike volume will be 28.23L at 70.6 degrees C (single infusion, light body, no mashout), with a sparge of 8.34L.
Pre-boil volume = 28.23 + 8.34(sparge) - 1(deadspace) - 7.75(absorption) = 27.82 L
Volume into fermentor = 27.82 - 4.21(evaporation) - 0.94 (shrinkage) - 1.9(trub) = 20.8L

Click to expand...

2. More importantly, even without stirring there is a lot of "movement" going on in the mash tun because of the water temperature (as in heat = fast moving molecules). So the mash thickness should be calculated based on the overall amount water in the mash tun, not only the amount of water that's above the false bottom. I think a good way of thinking about this is comparing the process to steeping a tea bag in a cup. Although the tea bag itself is only in direct contact with a small amount of surrounding water, the tea will diffuse after a little while because of the water temperature.

Click to expand...

A suggestion for being able to understand what he is saying about the diffusion, you can research "entropy".  The "Theory of Entropy" states:

Entropy

In thermodynamics, entropy (usual symbol S) is a measure of the number of specific ways in which a thermodynamic system may be arranged, commonly understood as a measure of disorder. According to the second law of thermodynamics the entropy of an isolated system never decreases; such a system will spontaneously proceed towards thermodynamic equilibrium, the configuration with maximum entropy.

Basically, the sugars coming out of the grain will not stay with the grain, but will move and create an equilibrium throughout the wort. 

Thanks Scott, that's exactly what I was referring to.

On the mash profile calculations again, would this be something that could be corrected/updated in beersmith?

  In version 2.3 of BeerSmith you can enter the "Mash Tun addition" which represents space below the mash screen that is recoverable.  Basically the program will add more water to compensate for this but won't subtract it when you drain the mash tun going into the boil.

Cheers,
Brad