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Re: Sugar calculations
Efficiency is indeed a can of worms. BeerSmith picks the nit by reporting
two efficiencies - mash efficiency (conversion + lauter or to-the-kettle)
and total brewhouse efficiency (to-the-fermentor). But as you mention
BeerXML uses "total brewhouse efficiency" in the recipe/equipment
definitions. I think the typical way of calculating here is all
fundamentally flawed - efficiency is a function of both the equipment and
the recipe; trub loss can be significantly higher with a high hop load if
you filter before the fermentor (needed with plate chillers) or use leaf
hops. Also lauter efficiency varies with OG and sparge method. This is a
hot button issue for me and it's one of the top items on my personal todo
list to try to rectify, or at least decouple the issues somehow.
Just off the top of my head I propose adding equipment parameters for "mash
efficiency", "vol loss per pellet hop oz/g", "vol loss per leaf oz/g", and
maybe "mash efficiency loss per OG point". Existing trub loss would be a
constant across recipes and would be chiller/deadspace/break loss. Zeroing
the loss fields would keep things the same for the folks who don't filter
anything or just don't care. I will add a blueprint for this soon.
Adding more confusion is that definition of "brewhouse efficiency" varies
depending on who you talk to. There's a bit of discussion here:
there's lots more if you search homebrewtalk. So, I like to use "total
brewhouse efficiency" to clarify when possible.
PS Hey all, another new guy here.
On Fri, Mar 8, 2013 at 8:43 AM, Philip Lee <rocketman768@xxxxxxxxx> wrote:
> On Thu, Mar 7, 2013 at 9:12 PM, mik firestone <mikfire@xxxxxxxxx> wrote:
>> In a small word, the brewnote efficiency calculations are rather messed
>> up. I'm using the postboil gravity when I should be dealing with the
>> preboil. I'm trying to unwind this right now but I keep running into weird
>> I am specifically looking at Recipe::recalcBoilGrav() and trying to
>> figure out why the boil gravity (aka, SG) is worried about trub/chiller
>> losses. Trub/chiller loss shouldn't have anything to do with the preboil
>> gravity, should it?
> You'd think it wouldn't have anything to do with it. However, there is a
> nit to be picked...
> BeerXML says the recipe efficiency is brewhouse efficiency, which is
> "to-the-fermentor" efficiency. Meaning, if I have 5.00 kg grain with 76%
> yield (3.80 kg sugar), and my brewhouse efficiency is 70%, I get 5.00 kg *
> 0.76 * 0.70 = 2.66 kg into the fermentor. Now, how would you go about
> finding how much sugar is in the kettle? Since the recipe's efficiency is
> "to-the-fermentor", we can't use that number directly; we need
> "to-the-kettle" efficiency. Since you are always losing some amount of
> sugar at each step of the brewing process, it must be the case the your
> "to-the-kettle" efficiency is somewhat higher than your "to-the-fermentor"
> efficiency. How much more?
> eff_tokettle = eff_tofermentor / (1 - trubChillerLoss/finalVolume)
> To extend the previous example, suppose my final volume is 20 L and I lose
> 1 L in the transfer from kettle to fermentor.
> eff_tofermentor = 0.70
> trubChillerLoss = 1 L
> finalVolume = 20 L
> sugar_kettle = 2.66 kg / (1 - 1L/20L) = 2.80 kg (73.7% efficiency to
> sugar_lost = 1L/20L * 2.80 kg = 0.14 kg
> sugar_fermentor = 2.80 kg - 0.14 kg = 2.66 kg (70.0% efficiency to
> I highly doubt any other software is picking this nit, but it definitely
> exists. You can see for this typical example that all your OG-related
> numbers would be off by about 4% if you don't calculate the kettle
> efficiency to be different from the brewhouse efficiency.
> Philip G. Lee
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