Wow, a big thanks for the idea from me as well. I got the bug and made one myself from an older unused kettle pick-up tube (hence the threaded end on the contraption).
Here is a wide shot for you.
and... a close-up showing the holes better.
For all those wondering, I ran this directly after my Blichmann Thrumometer (which takes my 1/2" tubing down to a 3/8" tubing size restricting the flow). I used spare unused parts from my brewery so I went with a brass 3/8" nipple soldered to a copper 45* street elbow that is of course soldered to the rest of the old copper kettle pick-up. I like it because drilling into the hex meant the perfect placement for the holes to be right as the device expands back into 1/2" causing the Venturi effect. I tried it with water and had noticeable aeration. I only did two holes and think that is plenty. I plugged one hole while testing and noticed no difference until both were plugged. Someone could comment if I need more or not and am just not noticing it, but I can always add more if I need to.
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this look like a good idea to me...
Is there any concern with contamination/infection?
I guess if we rinse/soak the sprayer/dispenser after each use, we should have less risk here... Am I right?
You're right, this is called a Venturi tube. The principle is that the piece of tube with the holes in it has to be a smaller diameter than the rest of the tubing. This makes the wort speed up through the restriction and cause a pressure drop, sucking air in through the holes. If you you restrict it again at the end with a spraying nozzle, you'll lose the benefit.
One thing you can try is to cut your siphon hose about halfway up and insert the venturi tube there so that there is a foot or two of hose below it. This will allow the air bubbles more time and distance to swirl in the moving wort. This will expose the wort to more surface area of air and should improve oxygenation
I tried the aeration gadget based on the above concept on my last brew session. I only had 1 or 2 pin holes in the venturi tube.
Best aeration yet
Awesome gadget... but I was reading Danstar's page last night and they said aerating with dry yeast is unnecessary. I will assume you built a starter with it... cause then its necessary according to them.
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Interesting point, nomorese1. Here's some stuff I cut-and-pasted from Danstar's website.
Quote:
Yeast need a trace amount of oxygen in an anaerobic fermentation such as brewing to produce lipids in the cell wall. With out O2 the cell cannot metabolize the squalene to the next step which is a lipid. The lipids make the cell wall elastic and fluid. This allows the mother cell to produce babies, buds, in the early part of the fermentation and keeps the cell wall fluid as the alcohol level increases. With out lipids the cell wall becomes leathery and prevents bud from being formed at the beginning of the fermentation and slows down the sugar from transporting into the cell and prevents the alcohol from transporting out of the cell near the end of the fermentation. The alcohol level builds up inside the cell and becomes toxic then deadly.
Lallemand packs the maximum amount of lipids into the cell wall that is possible during the aerobic production of the yeast at the factory. When you inoculate this yeast into a starter or into the mash, the yeast can double about three time before it runs out of lipids and the growth will stop. There is about 5% lipids in the dry yeast.
In a very general view:
At each doubling it will split the lipids with out making more lipids (no O2). The first split leaves 2.5% for each daughter cell. The second split leaves 1.25% for each daughter cell. The next split leaves 0.63%. This is the low level that stops yeast multiplication. Unless you add O2 the reproduction will stop.
When you produce 3-5% alcohol beer this is no problem. It is when you produce higher alcohol beer or inoculate at a lower rate, that you need to add O2 to produce more yeast and for alcohol tolerance near the end of fermentation. You definitely need added O2 when you reuse the yeast for the next inoculum.
If you prepare a starter culture you will need added O2. in the starter and perhaps in the main mash as a precaution. You will need to follow the precautions as mentioned above. If the mash is designed to produce 3-5% alcohol you may not need added O2. Brewing above that needs added O2.
So, the way I read this is that Danstar says "There are enough lipids in our dry yeast that aeration isn't as important, for 'standard' beer." Interesting. This may also play into the many anecdotal accounts we see here on fast and powerful fermentation starts with Nottingham.
Nevertheless, I aerate the wort no matter what I'm pitching into it. It's an ingrained part of my process -- and, IMO, still necessary to make the best beer one can.
It's not much aeration compared to 5 gallons, but think about it like this; it's aerating in small amounts, but there's also a small amount of wort in the racking cane at any one time. It's also moving at a constant flow.
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There is a very fine line between "hobby" and "mental illness."
The venturi is an awesome idea for brewing and will produce significantly better aeration than shaking and likely better than using an aeration system (air pump etc.).
Joe Camels comments should be taken to heart. Fewer, larger holes will be significantly better.
Also, the higher velocity the flow (the larger the pressure drop) the more air per volume of wort will be drawn into the stream. So a 3/8 cane with two large (relative) holes would be better than a 1/2 cane with a bunch of holes.
Also, the idea of moving the venturi up the line will make a big difference as the contact time between the air and the wort will be increased.
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