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**Brewer3401** · 07-24-2007, 01:55 PM

Anyone have any tech data on the difference(s) ?
Is 50' of 3/8" better than 25' of 1/2"

bigben · 07-24-2007, 02:16 PM

Well, I think total surface area is the most important thing...so if my calculations are correct...

50' of 3/8" = 58.875' of surface area
25' of 1/2" = 39.25' of surace area.

I think that's right...so I guess 50' of 3/8" is better because it has more surface area. Although maybe the amount of water at any given point has a lot to do with it. So, maybe a 1/2" of water can cool more in a given area than 3/8" of water.

Basically, I don't know.

mot · 07-24-2007, 02:18 PM

yep 3/8 does give you more surface area...but bens right who knows if the water in the 1/2 inch will cool more than the 3/8. Would need to do some testing and that kind of testing doesnt sound fun to me lol....any engineer here want to figure this out!

thebikingengineer · 07-24-2007, 03:22 PM

You'll probably have better luck with the 3/8". You'll never really max out the flow rate of the 1/2" tubing, and that extra 19' of area is pretty significant. To be more exact than this, you'd need to set up a thermodynamics problem, it would most likely be quite complicated, and it would only work in theory. Get your wort moving (via gentle stirring) while you're cooling to get down to temps very quick.

**Brewer3401** · 07-24-2007, 03:31 PM

Quote:

Originally Posted by thebikingengineer

You'll probably have better luck with the 3/8". You'll never really max out the flow rate of the 1/2" tubing, and that extra 19' of area is pretty significant. To be more exact than this, you'd need to set up a thermodynamics problem, it would most likely be quite complicated, and it would only work in theory. Get your wort moving (via gentle stirring) while you're cooling to get down to temps very quick.

Thanks for the info. I have a wort stirrer. I go from boiling to 100 F in 10 minutes. Have a new rig: 240 gph pump to push iced water directly to the IC. Haven't used yet, but tested and the coils get to 40 F, and the water exiting is down to 38 F. I'm projecting a 20 minute total to get to 50 F and using a LOT less ice than before (I used a pre-chiller, and never got the exiting water lower than 58 F)

**Bobby_M** · 07-24-2007, 03:31 PM

50 feet of 3/8" OD tubing has a surface area of 707 square inches.
25 feet of 1/2" OD is 471 incu.

I'm pretty sure the 3/8 is a better choice on many counts. It allows you to distribute the coils across a greater area of wort to reduce stratification. It also puts more of the overall coolant volume in contact with the copper to make sure it can pull heat. The only downside is that the coil will be a little flimsy on its own, I bound/spaced my coils with some copper wire to keep it a ittle more rigid.

I contributed some content in the wiki on this stuff: http://www.homebrewtalk.com/wiki/index.php/Immersion_Chiller

**Brewer3401** · 07-24-2007, 04:06 PM

I remember an article I read years ago about this. I thought they said the smaller diameter would work better - more surface area contacting the wort.

**Bearcat Brewmeister** · 07-24-2007, 04:16 PM

I did some calculations on this a year ago for a CFC (heat transfer + fluid mechanics) and you are correct - it only gives you the theoritical answer. The key is surface area to volume ratio. Smaller tube diameters have a higher surface area to volume ratio and are therefore more efficient. Smaller diameters should create a more turbulent flow which is critical in heat transfer. If the flow stays laminar, the water near the wall heats and forms a sort of insulative layer which reduces the heat transfer.

**evanmars** · 07-24-2007, 04:25 PM

Is the water in a 3/8" chiller after the first 25' still significantly cooler than the wort? If it isn't, it doesn't matter how much longer you make the coils. It isn't going to pull out any more heat.

However, if that is the case you could put in two separate 25' coils. That way you would have double the surface area. I'd figure that even if the temp of the wort was still hotter than the coil, this would work faster.

thebikingengineer · 07-24-2007, 07:31 PM

I've got one 25' 3/8 coil and can get 5.5 gals down to pitching temps in ~15 minutes with a whirlpooling method. I stick by spoon in with the IC (in the boil) and gently stir while I'm cooling. This gets the cool wort moving around the pot which brings the overall wort temperature down very quickly. The output water temperatures can get very, very hot. This lets me know that the process is working.