3/8" vs. 1/2" tubing for IC

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

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.

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!

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.

thebikingengineer said:

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.

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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)

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: https://www.homebrewtalk.com/wiki/index.php/Immersion_Chiller

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.

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.

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.

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.

Stirring is essential of course, but how long it takes to reach pitching temp is very much coupled to the tap water temp. If it's 85, you will NEVER reach pitching temp (70). Que the discussion of icewater pumping and prechillers, etc... ;-)

Bobby_M said:

Stirring is essential of course, but how long it takes to reach pitching temp is very much coupled to the tap water temp. If it's 85, you will NEVER reach pitching temp (70). Que the discussion of icewater pumping and prechillers, etc... ;-)

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From experience, I know once I am 10 F above my tap water temp, the law of diminishing returns kicks in big time.
If I can get from boiling to 100 F in 10 minutes, then (maybe) get to 50-60 F in another 5-10 minutes, why would I want to try to get from 100 to 95 F if would take 15-30 minutes.
I think the faster you can get to pitching temps the better.

It seems crazy that 25' of 3/8" coil has more surface area than 50' of 1/2". Ya gotta show me those calcs. I can tell you that, empirically, my 1/2" cools in like 10 mins where the 3/8" took 30 mins. That's just my $0.02

Hawkie333 said:

It seems crazy that 25' of 3/8" coil has more surface area than 50' of 1/2". Ya gotta show me those calcs. I can tell you that, empirically, my 1/2" cools in like 10 mins where the 3/8" took 30 mins. That's just my $0.02

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It might make more sense if you didn't have the numbers backwards!

Ar you doing 5, or 10 gal boils? If you are, or are ever going to, do tens, you'd be better off to use the 1/2, and add another 25' to it. These two peices can either be soldered/brazed together with a coupling, or stacked one on top of the other, and teed together outside the pot fairly easily.

As previeously posted, Surface area/volume and temp of tap H2O are very important, but also necessary, is the correct flow rate. If the water slows down too much (there's a lot of pressure drop through 50' of 3/8" (1/4" I.D.)), then it will accept too much heat before it leaves the chiller, and be useless as a transfer medium for the rest of the pipe length.

Therefore, 1/2" (of the same length) more surface area, AND a much higher flow rate = much quicker cooling.

Sea said:

It might make more sense if you didn't have the numbers backwards!

Ar you doing 5, or 10 gal boils? If you are, or are ever going to, do tens, you'd be better off to use the 1/2, and add another 25' to it. These two peices can either be soldered/brazed together with a coupling, or stacked one on top of the other, and teed together outside the pot fairly easily.

As previeously posted, Surface area/volume and temp of tap H2O are very important, but also necessary, is the correct flow rate. If the water slows down too much (there's a lot of pressure drop through 50' of 3/8" (1/4" I.D.)), then it will accept too much heat before it leaves the chiller, and be useless as a transfer medium for the rest of the pipe length.

Therefore, 1/2" (of the same length) more surface area, AND a much higher flow rate = much quicker cooling.

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I initially bought a 85 gph fountain pump. 50' of 3/8" tubing made an ass out of it.
Using a 240 gph pump, and it delivers a medium circulation (about 1/2 of what faucet is wide open).
Also, it's enough to put the discharge water back into my ice water bucket.
I'm assuming that once the discharge water temp drops below what my tap water temp is, the process will increase in efficiency.
I'm brewing a lager on Saturday, so I'm going to try to get my wort down to 50 F. By the time I whirlpool and transfer to the fermenter, I'm hoping for no higher than 55 F, then pitch.

Sea said:

It might make more sense if you didn't have the numbers backwards!

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AAAAHHHH.....I'm a knucklehead. That's what I get for trying to comment on thermodynamics at the end of the graveyard shift

thebikingengineer said:

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.

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That's not even necessary. In any heat transfer problem, the limiting factor is the amount of heat that can be conducted away from the heat source. The larger (shorter) tubing only adds 37% more thermal mass while the longer 3/8in tubing presents almost 100% more surface area. Assuming we were approaching boiling temperatures (at full flow) in the chiller water, more water flow *might* help with an over saturation problem, but we're not even close to that.

For a less technical example, consider your car radiator. The radiator hose and the radiator core both flow EXACTLY the same volume per unit of time. Given that the only difference between the two is surface area, which dissipates more heat? Obviously, the core. Would a 37% increase in hose size, and a 50% decrease in core surface area be more efficient? Most certainly not.

Barring water pressure issues, it would be best to use 50ft of 3/8" if you are limited to 25 vs. 50. As a previous poster said, if you can use 50ft of 1/2, that's an even better solution. Always circulate the wort.

Brewer3401 said:

Using a 240 gph pump, and it delivers a medium circulation (about 1/2 of what faucet is wide open).

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Sounds right. Most home faucets are 8-10gpm (480-600 gph)