How has a "brick" been determined?

[dick murton]

in the calculations for chilling requirements for fermenting, how has the term "Brick" has been determined. Is this a calculation, or simply a value that has been determined to work? And why the term "Brick" anyway?

Just interested

Thanks

[plh]

It is a very general number for the heat created during fermentation.

[dick murton]

Thanks, but can anyone expand on the calculations / reasoning behind this? Thanks

[Johnson_Thermal]

It is actually "Brix" (Bx) named after Adolf Brix, the dude who came up with the scale. It is a measure of the sugar content of an aqueous solution on a mass basis.

https://en.m.wikipedia.org/wiki/Brix

Converting sugars to alcohol is an exothermic reaction. I won't go into more detail than that because I am pretty rusty at writing balanced chemical equations but that how the numbers below are derived.


250-280 Btu/lb (IP)

There is a range there because I have seen both of these values published.

580 kj/kg (SI)


The mass value listed is the mass of fermentables not the total mass of the wort.

The heat of fermentation is calculated by looking at the beginning and final Brix. The "delta Brix" represent the mass of fermentables converted. Multiply that mass by the heat of fermentation cancels out the mass and leaves you with energy, either BTU or Kilojoules depending on the units you are using.

You then take that total amount of BTUs, then divide by the time to get BTU/HR or kW.

Note that there is an assumption that the fermentation rate is linear from beginning to end. My understanding (just a mechanical engineer not a brewer) is that the fermentation is more active at the beginning that towards the end. This means the heat of fermentation is not linear from beginning to end either.

However, when other loads are added up, particularly crash cooling, and the diversity of the number of fermenters use which are not all undergoing active fermentation, this non-linear behavior becomes pretty moot.

Note the similar phenomon occurs in bulk cooling of fresh produce. Even though the plants (stems, flowers, fruits, tubers) are not in the ground their cells are still alive and under going cell respiration which is also exothermic as it is the conversion of sugars to CO2.

Hope this makes sense. I welcome brewers with a better understanding of the physiology and chemistry to clarify it correct.

Regards,

Jeff Johnson
(Not with Johnson Thermal despite the user name )









Sent from my Pixel 5 using Tapatalk

[dick murton]

Thanks. That starts to make much more sense of the calculations I have seen. One of them called "bricks" BRIX, so I was wondering if this was something based on this. All the calcs I have found / seen use the same value - 15 bricks (or brix in that one case) and a fermentation time of 70 hours, which is certainly too long for peak rate of fermentation and heat production, and I guess the standard values were confusing me. But if those two values varied .... well of course there would be different results. But using standard values because that works pretty well, perhaps particularly for a micro brewery rather than a mega brewery (which I am more used to, and where the other figures come from), also makes sense. For what it is worth, I have a couple of other more "back to basics" formulae (from the large breweries / academics), so will now have the opportunity to compare results.

That makes sense. Thanks again

[Johnson_Thermal]

I think for a large brewery, slicing up the time component in smaller pieces would yield a more accurate results that would be worthwhile. You are basically doing an integral.

For a small brewery, the variations in calculation would be in between standard sizes for the most part. My definition of large vs small if pretty loosey goosey. When I say large I am thinking an AB facility to maybe like Stone.

Everything smaller than that would be "small."





Sent from my Pixel 5 using Tapatalk

[dick murton]

I'm not that familiar with Stone, but I am thinking of small breweries being perhaps 5,000 litre brewlength, and anything bigger than 10,000 litre going into large with probably anything much above 5000 brewing several times a day with semi or fully automated kit (though I used to brew with totally manual 80,000 litre (500 UK barrel) kit. How times change! Cheers