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Author Topic: Wort Aeration - Pt. 3: Nothing vs. Pure Oxygen | exBEERiment Results!  (Read 16334 times)

Offline charles1968

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Re: Wort Aeration - Pt. 3: Nothing vs. Pure Oxygen | exBEERiment Results!
« Reply #60 on: October 23, 2015, 09:36:46 am »
Am I trying to make enough ergosterol for 5 gallons? I thought thats what oxygenation of the wort was for.

Sorry, my bad for forgetting that lots of brewers oxygenate the wort. I tend not to bother and either pitch a very healthy starter or dry yeast. Having said that, I do let the wort splash around a bit when siphoning, but I've never bothered shaking it or using oxygen.
« Last Edit: October 23, 2015, 09:41:07 am by charles1968 »

Offline charles1968

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Re: Wort Aeration - Pt. 3: Nothing vs. Pure Oxygen | exBEERiment Results!
« Reply #61 on: October 23, 2015, 09:40:47 am »
Clearly, but the real question is how much of the air rotates? At what height above the liquid is the air column rotation little enough to be meaningless?

If I used a stir plate I could answer that by doing a test with smoke.

And remember the very idea behind an Erlenmeyer flask's shape is it's ability to contain a swirling liquid. Air can be treated like a liquid.

Liquids don't float freely out of containers - gravity keeps them in place at the bottom of the flask. So they're very different in this context, despite both being fluids.

Offline klickitat jim

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Re: Wort Aeration - Pt. 3: Nothing vs. Pure Oxygen | exBEERiment Results!
« Reply #62 on: October 23, 2015, 11:24:24 am »
Ah, but without liquid in the flask it's an apples to oranges comparison, running a stir bar in air will move a lot more air than a vortex in a liquid.

There's no reason why you couldn't do the same test with water in the flask.

I'm no aero/fluid dynamics expert, but I don't see the vortex in liquid creating much of a vortex in the air. While the air vortex may create some motion, I'm doubting it would do much to aerate the wort.

Friction between the water surface and air would set up rotation in the air. i'm certain about that, but how much gas exchange there is with the outside air via a tight fitting foil cap is debatable.
Wouldn't the smoke have to be cooled to ambient temp and weigh the same as CO2 before it started to prove anything?

Offline Phil_M

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Re: Wort Aeration - Pt. 3: Nothing vs. Pure Oxygen | exBEERiment Results!
« Reply #63 on: October 23, 2015, 11:41:26 am »
Wouldn't the smoke have to be cooled to ambient temp and weigh the same as CO2 before it started to prove anything?

Agreed.

Liquids don't float freely out of containers - gravity keeps them in place at the bottom of the flask. So they're very different in this context, despite both being fluids.

CO2 doesn't float freely out of a container either, it diffuses. (Assuming no outside air movement.) So yes, eventually the CO2 will diffuse out of the container, but over a period of time based on the volume, pressure, and temperature.
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Offline a10t2

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Re: Wort Aeration - Pt. 3: Nothing vs. Pure Oxygen | exBEERiment Results!
« Reply #64 on: October 23, 2015, 11:46:38 am »
Food for thought: fermentation of a given volume of 10°P wort evolves about 20 volumes of CO2. Spread out over a day or two, it isn't exactly rushing out of the starter vessel.
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Offline klickitat jim

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Re: Wort Aeration - Pt. 3: Nothing vs. Pure Oxygen | exBEERiment Results!
« Reply #65 on: October 23, 2015, 12:00:54 pm »
Food for thought: fermentation of a given volume of 10°P wort evolves about 20 volumes of CO2. Spread out over a day or two, it isn't exactly rushing out of the starter vessel.
True but what if it's got a pelicle?

Offline a10t2

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Re: Wort Aeration - Pt. 3: Nothing vs. Pure Oxygen | exBEERiment Results!
« Reply #66 on: October 23, 2015, 12:05:28 pm »
True but what if it's got a pelicle?

I'd throw it out and make a new starter. :o
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Re: Wort Aeration - Pt. 3: Nothing vs. Pure Oxygen | exBEERiment Results!
« Reply #67 on: October 23, 2015, 12:49:31 pm »
I was attempting to avoid this portion of the conversation because it brings back nightmares of dealing with a professor that I considered to be one step above a member of the SS. :)  We are dealing with the Venturi effect when we are discussing outflow from a cone.  Gas flow accelerates as it exits a cone due to the conservation of mass, but the pressure drops across the orifice.  I do not see how a significant amount of O2 can move into the flask when the pressure inside the flask is higher than it is outside of the flask.  According to Graham's law, CO2 and O2 move from an area of higher pressure to an area of lower pressure.

Offline a10t2

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Re: Wort Aeration - Pt. 3: Nothing vs. Pure Oxygen | exBEERiment Results!
« Reply #68 on: October 23, 2015, 02:00:00 pm »
I do not see how a significant amount of O2 can move into the flask when the pressure inside the flask is higher than it is outside of the flask.  According to Graham's law, CO2 and O2 move from an area of higher pressure to an area of lower pressure.

Lower *partial* pressure, though. As CO2 displaces oxygen, diffusion acts to draw more in. If there's no significant O2 in the headspace, my question is the same as before: what's the mechanism for a starter with an airlock growing less yeast?
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Offline klickitat jim

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Re: Wort Aeration - Pt. 3: Nothing vs. Pure Oxygen | exBEERiment Results!
« Reply #69 on: October 23, 2015, 03:05:40 pm »
I wonder how a Gordon Graham graph would apply at some point

« Last Edit: October 23, 2015, 03:08:49 pm by klickitat jim »

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Re: Wort Aeration - Pt. 3: Nothing vs. Pure Oxygen | exBEERiment Results!
« Reply #70 on: October 23, 2015, 03:11:18 pm »
Lower *partial* pressure, though. As CO2 displaces oxygen, diffusion acts to draw more in. If there's no significant O2 in the headspace, my question is the same as before: what's the mechanism for a starter with an airlock growing less yeast?

Hopefully, you are not basing your assertion on Kai's work.  A lot his work is so horribly flawed that it has me casting doubt on the accuracy of all of it.

Offline Stevie

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Re: Wort Aeration - Pt. 3: Nothing vs. Pure Oxygen | exBEERiment Results!
« Reply #71 on: October 23, 2015, 03:13:55 pm »

I wonder how a Gordon Graham graph would apply at some point


Offline charles1968

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Re: Wort Aeration - Pt. 3: Nothing vs. Pure Oxygen | exBEERiment Results!
« Reply #72 on: October 23, 2015, 04:12:06 pm »
Ah, but without liquid in the flask it's an apples to oranges comparison, running a stir bar in air will move a lot more air than a vortex in a liquid.

There's no reason why you couldn't do the same test with water in the flask.

I'm no aero/fluid dynamics expert, but I don't see the vortex in liquid creating much of a vortex in the air. While the air vortex may create some motion, I'm doubting it would do much to aerate the wort.

Friction between the water surface and air would set up rotation in the air. i'm certain about that, but how much gas exchange there is with the outside air via a tight fitting foil cap is debatable.
Wouldn't the smoke have to be cooled to ambient temp and weigh the same as CO2 before it started to prove anything?

If you're comparing smoke in a spinning flask to smoke in a stationary flask, that doesn't matter.

Offline charles1968

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Re: Wort Aeration - Pt. 3: Nothing vs. Pure Oxygen | exBEERiment Results!
« Reply #73 on: October 23, 2015, 04:15:33 pm »
Wouldn't the smoke have to be cooled to ambient temp and weigh the same as CO2 before it started to prove anything?

Agreed.

Liquids don't float freely out of containers - gravity keeps them in place at the bottom of the flask. So they're very different in this context, despite both being fluids.

CO2 doesn't float freely out of a container either, it diffuses. (Assuming no outside air movement.) So yes, eventually the CO2 will diffuse out of the container, but over a period of time based on the volume, pressure, and temperature.

CO2 doesn't act like a kind of invisible water, it's much more buoyant, even if heavier than air. I reckon it would dissipate quickly if given a stir.

Offline charles1968

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Re: Wort Aeration - Pt. 3: Nothing vs. Pure Oxygen | exBEERiment Results!
« Reply #74 on: October 23, 2015, 04:21:12 pm »
I was attempting to avoid this portion of the conversation because it brings back nightmares of dealing with a professor that I considered to be one step above a member of the SS. :)  We are dealing with the Venturi effect when we are discussing outflow from a cone.  Gas flow accelerates as it exits a cone due to the conservation of mass, but the pressure drops across the orifice.  I do not see how a significant amount of O2 can move into the flask when the pressure inside the flask is higher than it is outside of the flask.  According to Graham's law, CO2 and O2 move from an area of higher pressure to an area of lower pressure.

Sure if there"s a steady gust of wind flowing out of the flask then O2 will have a hard time flowing in but there isn't that kind of mass flow generated by a yeast starter.