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Episode #121 - Boiling Home Brewed Beer with Dr Charlie Bamforth

BeerSmith

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Boiling Home Brewed Beer with Dr Charlie Bamforth - BeerSmith Podcast #121
  http://beersmith.com/blog/2016/03/01/boiling-home-brewed-beer-with-dr-charlie-bamforth-beersmith-podcast-121/

Cheers,
Brad
 

brewfun

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Lyon1066 said:
How many BTU's would be required to provide a vigorous boil for 6 gallons of wort?

A btu is the amount of heat needed to raise 1 lb of water 1 degree farenheit. The btu number is always an hourly figure.

It takes about 1000 btu to create 1 lb of steam. A full gallon weighs about 8.33 lbs, so a gallon of boiloff takes about 8300 btu. The actual number goes up a little with wort because it takes more power to separate water from sugar with increasing concentration.

Maintaining a boil is the amount of heat needed to counteract the hourly cooling of the wort.

If you had a gallon of boiloff and your pot would lose 30 degrees if left for an hour, you'd need:

Wort: 30 * 7 * 8.33 = 1749
Boiloff: 8.33 * 1000 = 8300
Total: 10049 btu into the wort.

The burner itself would have to be bigger to account for wasted heat.
 

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What are the units for the 7?

Based on this, with a 12,000 but burner, there should be ~2,000 spare btu's for heat-losses in the system.  However, I am not able to achieve a rapid, or rolling, boil.

I am using a burner rated for 12,000 btu's, but have not be able the achieve more than a tepid boil.  The only way to get it rolling is by putting the lid on to retain the steam, heat.  I have avoided this, to ensure the volatiles are evaporating, but do cover 3/4's of the pot, letting the steam evaporate out the last 1/4.

My last batch did not have an appreciable DMS flavor, but then it's a Porter, so the threshold for tasting DMS may be higher. :D
 

brewfun

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Lyon1066 said:
What are the units for the 7?

Preboil gallons. Sorry, I thought that'd be obvious.

Based on this, with a 12,000 but burner, there should be ~2,000 spare btu's for heat-losses in the system.  However, I am not able to achieve a rapid, or rolling, boil.

You can expect burner waste heat to be about half, sometimes 2/3 of the btu's.

Kettle geometry also plays a part, since the wider the kettle, the more surface area of wort there is available to lose heat through evaporation. Covering it slightly isn't the end of the world, but you’ll want to upgrade your burner to improve your wort quality. The SMM to DMS change is more a factor of time, but boil vigor is important in driving it off.
 
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