Is the dead space really a problem when doing a full volume mash?

[doug293cz]

Thanks to @kohalajohn for this level of detail, but I think I'll push the big "ignore" this thread button.
Y'all have fun, but I have completely lost interest in seeing any more on this topic.

Do you really feel that it is necessary to tell everyone that you are going to ignore a thread? Isn't it better to just quietly disappear, rather than cluttering up the thread with information that is useless to those who are interested in the thread?

Brew on

 

[mac_1103]

Do you really feel that it is necessary to tell everyone that you are going to ignore a thread?

Are you really ignoring someone if you tell them that you're ignoring them?

OK, maybe that should be in the random drunken thoughts thread.

 

[tracer bullet]

15%

I did a rough calculation on my Anvil a while back and it's in the neighborhood of 30% of the cross-sectional area where the mash pipe sits.

 

[doug293cz]

I did a rough calculation on my Anvil a while back and it's in the neighborhood of 30% of the cross-sectional area where the mash pipe sits.

Can you supply some numbers on your unit:

Inside diameter of the vessel​

Diameter of the malt pipe​

Distance between bottom of malt pipe and bottom of vessel​

Distance between bottom of malt pipe and top of any perforations in malt pipe​

​

This data would allow some rough estimates of the worst case loss of lauter efficiency from not homogenizing the wort before pipe draining.

Brew on

 

[Dave C01]

I have a Brewzilla So I have a solid wall mash pipe instead of a bag. And that means that the wort between the walls of the pipe and the outside of the machine, does not move around much. Can be called "dead space"

And it's a surprisingly large amount. Since it's on the outside, geometry evidently tells us that it's a lot of volume. Liters and liters of it.

But is this a problem? Some online say it is. Some AIO owners lift and lower the pipe. You have to be careful with that, with a Brewzilla as our bottom plate is loose and lowering too fast will upset it and pour out grains. But you can do it. And that would certainly mix up the waters nicely.

My last batch I followed some advice and directed the recirc hose into a lifting hole and did a brief recirc in the dead space that way. But that was also a hassle, as the wort just ran down one section and I had to keep rotating the pipe to get at all of it.

And tonight, after my second sip of whisky, I suddenly wondered if it's even a problem.

ok, so this strike water in between the walls is not actively involved with the grist. It's not doing the job of saccharification.

But in a full volume mash, who cares. I sometimes do a 6 liter pour over, instead of a full volume. That sparge water never did any saccharification work at all. And that's fine.

Seriously, is this dead inner wall space thing, actually a problem?

Thanks in advance for your input. Picture below, as we all like pictures


View attachment 878291

 

[tracer bullet]

Can you supply some numbers on your unit:

Anvil 6.5 which I put about 6lbs of grain and 4+1/8 gallons of water into, for mashing my last brew (Pale Ale).

11+5/8 ID for unit
10" even for pipe
2+1/4" from bottom of pipe feet to mesh platform inside it (which is ~ 3/8" higher than the outside edge of the pipe itself)
No perforations

 

[kohalajohn]

I see Bobbi has a sophisticated method of diverting recirc both over the bed and in between the walls.

My question is there much benefit to just shoving in a separate hose, a couple times during the mash?

I have a second metal recirc arm and elbow and a thin hose on it, that fits in the lifting hole. I could run this for a few minutes, hopefully mixing the stagnant wort with the rest of it, and then put back the main recirc arm over the grain bed.

 

[doug293cz]

Anvil 6.5 which I put about 6lbs of grain and 4+1/8 gallons of water into, for mashing my last brew (Pale Ale).

11+5/8 ID for unit
10" even for pipe
2+1/4" from bottom of pipe feet to mesh platform inside it (which is ~ 3/8" higher than the outside edge of the pipe itself)
No perforations

Ok, I put together a quick-n-dirty spreadsheet to calculate the possible best case and worst case lauter efficiencies for AIOs with malt pipes. It calculates what you should get for lauter efficiency if you left out the malt pipe and did a brew-in-a-bag, and also calculates the lauter efficiency for the same inputs if there was zero mixing of extract (sugar, etc.) with the water between the malt pipe and vessel wall. In the real world you would expect some amount of diffusional mixing, so actual lauter efficiency would be somewhat higher than the worst case calculation.

Without the malt pipe, for 6.5 lb of grain mashed in 4.125 gal of water (volume assumed at 68°F, if volume was measured at a different temp, results would be a little different), and 100% conversion efficiency the lauter efficiency would be 74.4%. With the malt pipe the lauter efficiency would be 67.7%. In the first case the pre-boil SG would be 1.0513, and with the pipe 1.0465.

I calculate your gap cross sectional area as 26% of the vessel cross sectional area, and 35% of the pipe cross sectional area. So, the Anvil with it's larger pipe to vessel gap than a Brewzilla shows a larger delta in lauter efficiency between best case and worst case.

Brew on

 

[doug293cz]

I see Bobbi has a sophisticated method of diverting recirc both over the bed and in between the walls.

My question is there much benefit to just shoving in a separate hose, a couple times during the mash?

I have a second metal recirc arm and elbow and a thin hose on it, that fits in the lifting hole. I could run this for a few minutes, hopefully mixing the stagnant wort with the rest of it, and then put back the main recirc arm over the grain bed.

As shown in this post, the maximum difference in lauter efficiency between complete wort homogenization prior to lautering vs. 0 mixing of the water in the pipe-vessel gap is ~3% for a beer with a pre-boil gravity of ~1.040. Since you will get a little mixing with the liquid in the gap, the actual difference will be smaller than that.

The above is for the Brewzilla, where the pipe to vessel gap is about 14 mm. On the other hand, an Anvil has about a 20 mm gap, so the difference in lauter efficiencies between homogenizing and not homogenizing will be larger.

So, how much effort do you want to put into reducing that less than 3% loss?

Brew on

 

[tracer bullet]

Without the malt pipe, for 6.5 lb of grain mashed in 4.125 gal of water (volume assumed at 68°F, if volume was measured at a different temp, results would be a little different), and 100% conversion efficiency the lauter efficiency would be 74.4%. With the malt pipe the lauter efficiency would be 67.7%. In the first case the pre-boil SG would be 1.0513, and with the pipe 1.0465.

Cool to know the details, thank you. I will continue to do the lift & lower thing a couple times during the mash and probably to suggest it to others as well. Nice to have #'s on it.

 

[kohalajohn]

Thanks. @doug293cz , I'm not going to bother.

 

[kohalajohn]

I must say, it's been a journey, this efficiency thing.

When I recently returned to brewing I saw this talk of varying efficiencies and thought it was the goal. That if I could not reach high efficiency numbers that meant I was a bad man, with a shameful secret and that the internet would recoil as the mere mention of my name.

Ha. Now I'm just going to make beer I like.

 

[hungupdown]

As shown in this post, the maximum difference in lauter efficiency between complete wort homogenization prior to lautering vs. 0 mixing of the water in the pipe-vessel gap is ~3% for a beer with a pre-boil gravity of ~1.040. Since you will get a little mixing with the liquid in the gap, the actual difference will be smaller than that.

The above is for the Brewzilla, where the pipe to vessel gap is about 14 mm. On the other hand, an Anvil has about a 20 mm gap, so the difference in lauter efficiencies between homogenizing and not homogenizing will be larger.

So, how much effort do you want to put into reducing that less than 3% loss?

Brew on

I'm prepared to put in 5 seconds of effort, where that will prevent a 5% loss on efficiency.
Eg BZ full volume mash. 6kg grain,; 1 litre/kg absorbtion ratio.

 

[Peebee]

I must say, it's been a journey, this efficiency thing. ...

You're right! Fascinating stuff, when I began to realise it was directly connected with an issue I was trying to deal with (I prefer to "Full-Boil-Volume-Mash" too): "Recoverable dead-space" not "Efficiency". I'd get runaway strike temperatures calculated if I wasn't careful, and the day came that I wasn't careful, and I couldn't no-longer figure out how I'd fix it. But I started reading this thread ...

The "3.5 litres" of "recoverable dead-space" around the Grainfather malt pipe isn't quite as simple as I'd presumed, the volume under the malt-pipe is recirculated, the volume up the sides isn't (I've upgraded to their V3 Malt Pipe too). It matters (?) because of mash-thickness calculations it seems to me (now), except if full-boil-volume-mashing I've already excluded myself from "mash-thickness" and "efficiency" concerns. Some even doubt mash-thickness's connection with efficiency (just try and find what optimum mash thickness is). So, why am I concerned about "recoverable dead-space"?

I never worried about "efficiency" or "mash thickness" before. So, now, I don't worry about "recoverable dead-space" either. I either mash at "Full-BATCH- Volume" (plus the non-recoverable losses like "boil-off", dead-space and grain/hop absorption), "Three-Quarter-Batch-Volume" (if I fancy a bit of a sparge) or "Half-Batch-Volume". Brewing suddenly becomes that much simpler. I too can just concentrate on making beer I like!





(Ah ... the internet still recoils at the mere mention of my name. That bit didn't work.)