Author Topic: higher efficency w/ 10 gal batch than on a 5 gal ?  (Read 2296 times)

Offline denny

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Re: higher efficency w/ 10 gal batch than on a 5 gal ?
« Reply #15 on: April 16, 2011, 08:34:08 AM »
Then I agree, bed depth is probably the problem. 

Bed depth impacts efficiency?

In fly sparging, yes.  In batch sparging, very little to not at all.
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Offline Will's Swill

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Re: higher efficency w/ 10 gal batch than on a 5 gal ?
« Reply #16 on: April 16, 2011, 10:39:46 AM »

It was my understanding that if the mash bed wasn't deep enough that when sparging the water would move through to quickly and not extract the sugars as efficiently.

Huh.  But flow rate can be controlled, so I don't think this would be a problem.  I could maybe see that if you put the same amount of grist into two mash tuns, one that is wider than the other so that the grain bed depth is less, maybe the wider tun would have less efficiency since not as much sparge water flows past any particular grain.  Maybe.  I doubt it, but maybe.

On the other hand reducing the amount of grist in a particular tun would also reduce grain depth, like in the OP's case.  But that would mean that the sparge water flowing past any particular grain on the bottom of the tun would have a lower concentration of sugar, since it hasn't passed through as much grist.  I bet that would increase efficiency if anything.

I suspect the grain bed depth thing is one of those homebrewing urban legends like recirculating the mash until clear, trub removal, and CO2 blankets...  ;D
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Offline denny

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Re: higher efficency w/ 10 gal batch than on a 5 gal ?
« Reply #17 on: April 16, 2011, 11:06:04 AM »
Again, keep in mind that only applies if you fly sparge, not if you batch sparge.
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Offline tschmidlin

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Re: higher efficency w/ 10 gal batch than on a 5 gal ?
« Reply #18 on: April 16, 2011, 11:12:21 AM »
I suspect the grain bed depth thing is one of those homebrewing urban legends like recirculating the mash until clear, trub removal, and CO2 blankets...  ;D
Test it ;)
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Offline Will's Swill

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Re: higher efficency w/ 10 gal batch than on a 5 gal ?
« Reply #19 on: April 16, 2011, 11:17:32 AM »
Indeed!  Whaddaya think, IPA vs. IIPA?  Or perhaps same beer, but different batch sizes?  Hmm, with the different batch sizes I could finally do that blow-off vs no blow-off side-by-side that I've been meaning to do...

I also bought some long matches to mess around with the CO2 and see if it stays put.  But not until after taxes. 

This *$(^(*# forum can really provide a lot of procrastination opportunity.
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Offline tschmidlin

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Re: higher efficency w/ 10 gal batch than on a 5 gal ?
« Reply #20 on: April 16, 2011, 11:41:46 AM »
I think 5 gallons of pale ale and 10 gallons of IIPA, go for a big difference.  Same grist composition, mill setting, length of mash, etc.  The runoff speed is an interesting variable, do you run off at the same volume per time, or go for the same time for run off?

As for your match experiment, I doubt it will work.  It depends on how you do it, but keep in mind that there needs to be about 13%+ O2 in the air you're testing to maintain a flame.  I don't think anyone is saying that CO2 blankets are complete BS, there is some effect, especially if there isn't a lot of air currents.  But it's not rock solid like some people seem to think, and it will dissipate over time, if not from air currents then from diffusion.  If this didn't happen you'd suffocate in Death Valley.
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Offline Will's Swill

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Re: higher efficency w/ 10 gal batch than on a 5 gal ?
« Reply #21 on: May 30, 2011, 10:11:45 PM »
OK, the results are in.  12# grist v. 6# grist for two IPAs that are otherwise identical.  1 qt/# strike water plus 3 qts for foundation water.  1.75 qt/# at 167F for fly sparging.  The mash tun used for both was an insulated 5 gallon bucket with a false bottom, so the bed depth was approximately halved by going from 12# to 6#, and the depth difference was bigger than if I had used my rectangular cooler.  Each mash was three hours at 145F with an additional infusion of .25 qt/# boiling water at the 2:15 mark (stirred to return back down to 145F - iodine test on both was positive at 2 hours; figured I mashed too thick so I added water to thin it down; each showed fully converted at the 2:45 mark - and I know iodine shouldn't be trusted, but oh well).  I used the same flow rate for each sparge.

12# grist - 81% efficiency to kettle
6# grist - 84% efficiency to kettle

While the smaller bed depth apparently had a slightly higher efficiency, the difference is small and could be due to measurement or process error, or the simplistic way I calculate efficiency (points * volume/extract potential).  An interesting data point is that I lost .21 gal/# to the grist in the 12# mash, but only .14 gal/# in the 6# mash.  That by itself could account for the difference (there's virtually no deadspace in the mash tun)

A highly non-scientific test, but there ya go.
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Offline richardt

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Re: higher efficency w/ 10 gal batch than on a 5 gal ?
« Reply #22 on: May 31, 2011, 07:04:57 AM »
...  It depends on how you do it, but keep in mind that there needs to be about 13%+ O2 in the air you're testing to maintain a flame.  I don't think anyone is saying that CO2 blankets are complete BS, there is some effect, especially if there isn't a lot of air currents.  But it's not rock solid like some people seem to think, and it will dissipate over time, if not from air currents then from diffusion.  If this didn't happen you'd suffocate in Death Valley.

In nature, while rare, CO2 blankets can and do exist.  And the results are quite deadly.
http://vulcan.wr.usgs.gov/Glossary/Lakes/description_volcanic_lakes_gas_release.html
http://volcanoes.usgs.gov/hazards/gas/index.php

In homebrewing, CO2 blankets pose a great and invisible threat to homebrewers who brew in unventilated areas and/or in basements with propane burners. 
Be smart and brew outdoors and/or in well-ventilated areas.  Give that toxic gas somewhere to go.
CO2 in fermentation vats also can be lethal
http://www.brewsnews.com.au/2010/02/death-by-beer/

Offline tschmidlin

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Re: higher efficency w/ 10 gal batch than on a 5 gal ?
« Reply #23 on: May 31, 2011, 09:10:51 AM »
...  It depends on how you do it, but keep in mind that there needs to be about 13%+ O2 in the air you're testing to maintain a flame.  I don't think anyone is saying that CO2 blankets are complete BS, there is some effect, especially if there isn't a lot of air currents.  But it's not rock solid like some people seem to think, and it will dissipate over time, if not from air currents then from diffusion.  If this didn't happen you'd suffocate in Death Valley.

In nature, while rare, CO2 blankets can and do exist.  And the results are quite deadly.
http://vulcan.wr.usgs.gov/Glossary/Lakes/description_volcanic_lakes_gas_release.html
http://volcanoes.usgs.gov/hazards/gas/index.php
I've heard about those instances, but this isn't the same.  You want 100% CO2 (really 0% O2) over your beer to protect it, but relatively low levels of CO2 in the air can cause health problems for people.  From your second link:
Quote
Air with 5% CO2 causes perceptible increased respiration; 6-10% results in shortness of breath, headaches, dizziness, sweating, and general restlessness; 10-15% causes impaired coordination and abrupt muscle contractions; 20-30% causes loss of consciousness and convulsions; over 30% can cause death



In homebrewing, CO2 blankets pose a great and invisible threat to homebrewers who brew in unventilated areas and/or in basements with propane burners. 
Be smart and brew outdoors and/or in well-ventilated areas.  Give that toxic gas somewhere to go.
CO2 in fermentation vats also can be lethal
http://www.brewsnews.com.au/2010/02/death-by-beer/
There is a big difference in the amount of CO2 generated on a homebrew level compared to a commercial brewery.  I'm not saying there is no risk, but it is low risk.  I fermented 10 gallons in a closed bathroom recently, and whenever I went in there there was enough CO2 concentrated to burn my nostrils a little bit.  I wouldn't want to do more than that actively fermenting in a closed space.

Also, the larger danger from propane burners is carbon monoxide, CO.  CO binds very tightly to hemoglobin, much more so than O2.  There's more to it, but the end result is that your body doesn't get the oxygen it needs.  And that's bad. ;)
Tom Schmidlin

Offline 52mgtd

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Re: higher efficency w/ 10 gal batch than on a 5 gal ?
« Reply #24 on: June 05, 2011, 01:33:47 PM »
yes, I suspect there's more mass to hold the heat.  I love doing 5 gal reciped & getting 9 gallons of wort!