HOMEBREW Digest #5522 Mon 09 March 2009

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  Wort chiller design... (Aaron Gallaway)
  Re: CO2 (steve alexander)
  Re: CO2 (Joe Walts)

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---------------------------------------------------------------------- Date: Sun, 8 Mar 2009 22:36:13 -0700 From: Aaron Gallaway <baseball_junkie at hotmail.com> Subject: Wort chiller design... To one, to All... I am at the tail end of rebuilding my brewery(finally got the engineer on my Tug weld my stand for me) and am planning a new chiller...would like some input from those with a PVC CF design. Planning 50' of 3/8" ID copper coiled to 5" coils fitted into a 2' section of 6" PVC with end caps and 5/8" hose barbs for cold water in and outs with a capped 4" length of PVC fixed in the middle of the coils to force the water to flow across the coils rather than pass through the center decreasing the heat exchange values. Any thoughts, ideas, suggestions and pictures would be greatly appreciated. Thanks, Aaron the Tugboater PS, my tug engineer turned fledgling home brewer seeks a quality honey brown recipe...anybody have one?? Return to table of contents
Date: Mon, 09 Mar 2009 07:05:14 -0400 From: steve alexander <steve-alexander at roadrunner.com> Subject: Re: CO2 AJ, as usual, produces a clear concise descriptive example; this time of CO2 at brewery scale. One aspect of carbonation and decarbonation that receives little attention is the rate at which equilibrium is approached. We all know that in addition to CO2 pressure we must apply agitation and/or, or in introduce CO2 via a stone to approach equilibrium rapidly ... but that's not quantitative. Then the opposite problem occurs when you open a bottle the rate at which it decarbonates varies wildly from a minor fizz to a gusher that will almost match a "mentos gusher". So what exactly is going on here ? I'm sure there is a diffusion eqn for the CO2 in solution/gas phase and the rate is probably related to surface areas and concentrations(pressures). That one I'm sure I can lookup and recognize. The decarbonation seems to often be more closely related to nucleation sites. It's easy to imagine that any beer, even the filtered stuff has enough particulate that shaking can cause an "upset". OTOH when we take pure seltzer water and shake it .... what happens ? Apparently the (at equilibrium) CO2 bubbles mixed into the water are sufficient to cause nucleation. That last one is a bit strange, but I'm not a physical chemist. I think there should be an entropy increase and a temperature decrease as beer decarbonates, so with enough carbonation perhaps we could dispense with fridges and chillers (joke). I think there are some pieces that perhaps AJ can explain wrt beer carbonation/decarbonation process. The usual sources ignore the transition and just suggest you add a certain amount of CO2 and dismiss the details of how this addition takes place with a handwaving mention of stones and pumps. Then there is an implicit assumption that CO2 is released at the appropriate rate when the bottle cap is popped or the beer is pushed past a tap. Obviously this is not always the case. > The obvious message here is that 6 kg of CO2 which do not end up in > the beer, are nevertheless paid for ($12) and (for those who worship > at the church of Al Gore) released to the atmosphere. In AJs example we are discussing 1000gal(3785L) of beer and quibbling about 17 kg of CO2 retained and perhaps another 6kg lost for carbonation. If this is a conventional strength and attenuation beer then it starts with ~476kg of extract, perhaps ~300kg is fermentables and fermentation release a bit under 150kg of CO2! IOW we only need about 15% of the CO2 for carbonation. Even in a brewery where fermentation CO2 is retained for use in carbonation there is a very large CO2 release. Twice as much CO2 is released as the beer drinker exhales, so this 1000gal of beer results in ~450kg of CO2 release. This might anger the AlGorites, except we can associate this CO2 release with the magical words (for those who with magical thinking processes) "renewable", or "recyclable" or "green" or some other claptrap. The carbon ultimately came from the atmosphere as the barley grew in fields and this makes it acceptable to some sects of AlGorism. Somehow the fact that petrol and coal carbon also originated in the atmosphere, tho' less recently, doesn't create any acceptance by that cult. BTW I'd like to introduce anyone who uses the phrase "renewable energy" to the first & second laws of thermodynamics - muddled thinking reflected in muddled terminology. Anyone interested in the energy problem should examine this free book, downloadable book from U.Cambridge Press. http://www.inference.phy.cam.ac.uk/sustainable/book/tex/sewtha.pdf The author, a Cambridge Physicist examines the energy issues in a highly readable and informative way. He dispels a lot of popular and political lunacy wrt grain ethanol, photovoltaics and the realistic role of wind, tidal and nuclear in any realistic future. His primary example is the highly populous UK, with a rather different resource mix, tho' he examines other places and the general issue in detail. His graphs of the EU carbon trade value shows a disastrous trend that we US'ers should examine closely given the new carbon cap&trade plans that Geithner estimates will cost over $800Bn. -S Return to table of contents
Date: Mon, 9 Mar 2009 10:25:46 -0500 From: Joe Walts <jwalts at gmail.com> Subject: Re: CO2 A.J. - I checked my calculations against yours and they all agree. I wasn't talking about atmospheric CO2 breakout. What I was trying to say is if you have a half-full keg of beer in equilibrium, the mass of CO2 in the beer is greater than the mass of CO2 in the headspace. At least, that's what the calculations claim. Are you saying that's true based on the reduction of gas pressure in solution? If so, it's pretty counter-intuitive (to me) and I'm glad that you can explain it. I changed the formulas in my spreadsheet to compute the headspace CO2 mass with the Redlich-Kwong equation instead of the Ideal Gas Law. Both methods gave similar answers and suggest that, at serving temperatures, the beer in a half-full keg holds a larger mass of CO2 than the headspace. Back to the original question. Joe K - are you referring to the common commercial brewing practice of adding CO2 through a carbonation stone (at around 30 psig) while slowly bleeding CO2 from the headspace to avoid overpressurizing the tank? It's wasteful of CO2, but it uses less energy than a pump and it's fast. I don't think there's any way to calculate the volume ahead of time unless you know the mass flowrate out of your bleed/relief valve. The basic procedure is to add CO2 for a set amount of time, check the beer's carbonation level with a Zahm & Nagel CO2 tester and repeat. With practice, you'll develop a sense of how much time it'll take to reach a desired carbonation level on your system. Joe Return to table of contents
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