Interesting conversation with a Mech. Engineer at Work

So as some of you may know, I work in a testing lab for military and commercial products. Today, I was talking to one of our engineers about building a beast of a CFC, but with a slightly different design than what you are all used to.

Essentially, we would use 3/4" ID tubing for the outside layer, 1/2" OD Tubing inside, and then (here's the kicker) 1/4 tubing inside the 1/2. Essentially the idea would be to use the outermost and innermost tubes for chilling water, and the middle tube for the wort. In theory, this should allow for extremely fast cooling times due to the increased exposure to cooling liquids.

The other thought would be to use the innermost tube for the wort, and the outer 2 tubes for cooling liquid to keep the inner cooling tube better insulated, and allow the outer cooling tube to accept some of the heat. We are just playing around with the idea, and if I can get enough money together, I may build one for the hell of it...

Outer - water,
middle - wort,
inner - water is the way to go

Water, water wort really has no point

Special Hops said:

Water, water wort really has no point

Click to expand...

My thoughts exactly. What would the top layer of water do?

The first idea would speed up cooling to a degree because of the increased surface area, but the amount would depend on the design. The inner tube would have a much lower mass flow rate, and would be limited on the amount of heat it could extract compared to an equivelent length of the outer tube.

I don't think the second idea would behave much differently than just a 1/4" line inside a 3/4" tube. the outer tube just provides additional water for cooling, but does so through conduction, rather than convection (mixing) that would happen without the tube.

Ultimately, how fast you cool the wort depends on the mass flow rates of the two liquids, the temp delta between them, and surface area available.

For all else being equal:
a) If you increase the temp delta, you increase the cooling rate.
b) If you increase the mass flow rate of the cooling water, you increase the amount of heat removed from the wort.
c) If you increase the surface area, you increase the rate that heat is transfered to the cooling medium.


there are limits to b) and c) when one side or the other equation gets saturated, but generally, bigger is better when it comes to speed.

two things I see from the first idea. You'll come up with a more compact counterflow chiller which is cool, but you also will have a harder time cleaning/chance of clogs because the wort path won't be a unobstructed.

Anyways, those be my thoughts on it.

it would keep the middle layer from getting to hot from the diffusion of heat of the wort. Either both ways (water water wort, or water wort water) will work equally efficiently or the water wort water one will work more efficiently. I dont believe the water water wort version will outperform the water wort water version. Thats a damn complicated response! I'm no thermal engineer (if that exists), I'm a musician, disregard everything I've said.

Based on the tubing sizes you listed, the water-wort-water setup would have three times the surface area exposed to coolant than the water-water-wort setup.

Seems like a really great idea.

All the water-water wort set-up would do is make the water out of your middle tube not be so hot when coming out of the chiller - at which point you don't care what it's temp is.

ok, well if you are going to spend that much on copper piping and fittings, you may as well buy a plate chiller.

Sounds like an ambitious project, have you established the flow rate for the wort, coolant temperature, coolant flow, and approach temperature. Might have a problem with friction in the wort path with small cross section area for fluid flow.

Cool to think about, but how would you terminate all of the tubing? Two of the right-angle step down tricks at each and? Talk about friction, your wort would be sore before it hit the carboy!
Still fun to noodle on though.

Sure, the theoretical cooling rate would be fantastic, but in reality, how fast can you push wort through the space you're providing? In either scheme (water/water/wort, or water/wort/water), you're severely limiting the flow volume via 1/4" tubing or 1/2" stuffed full of 1/4". It's a fantastic idea, but you may want to consider using some larger diameter tubing to maximize the effectiveness.

i could see the water water wort method working if the outside flow of water ran the same direcetion as the wort, and the middle fluid ran counter. That way the middle would be taking heat off the wort, and the outside taking heat off the middle more effectively than convection would have it. does that make any sense? i dunno....

i'd still do water/wort/water if i had the option, maximum surface area.

water/wort/water seems like an inventive idea. But, I've got two concerns:
1) starting with a traditional CFC, would it actually be any cheaper to add that third layer of tubing rather than just increasing the length of the standard design a bit for equal performance?
2) the cross section of the 1/4" tube is probably smaller than that of the area between the middle and outer tubes. (bear with me, hypothetical thought experiment here) The smaller volume/flow of water in that tube would therefore heat up more quickly (in a shorter distance down the chiller) than the chilling water in the outer tube, possibly saturating partway through. Then at a certain point along the chiller's length, the wort (still being cooled by the larger flow of water in the outer tube) would actually be COOLER than the water in the inner tube. Then the heat would be going back INTO the wort, to be removed by the outer tube, in which case you might as well not have the inner tube at all.

I know that's rather hypothetical, and I'm no bracket bender, but does that make any sense? I can definitely see how a water/wort/water system could be very effective due to the surface area, but it seems like you would have to be careful to make sure the flow rate in the inner and outer cooling tubes was somewhat balanced.

I'd have to agree that simply extending the length of an easy to build design would do the same thing and be cheaper too since the outside jacket can be anything.

We also recently threw around ideas about increasing surface area by using two smaller inner tubes (maybe 1/4" OD) inside the standard rubber outside jacket (maybe 3/4" ID garden hose).

Funkenjaeger said:

Then at a certain point along the chiller's length, the wort (still being cooled by the larger flow of water in the outer tube) would actually be COOLER than the water in the inner tube. Then the heat would be going back INTO the wort, to be removed by the outer tube, in which case you might as well not have the inner tube at all.

Click to expand...

We would find temperature equilibrium before the inner water would heat up the wort...

It would be easy to make the tubing larger diameters over all, however the price would SKYROCKET...

Still playing with ideas... I may have found my senior capstone project...

I considered such an idea (mine was just wort on the outside with water on the inside), but discarded it due to the difficulty of cleaning and sanitizing the wort passage. When you have the wort in the very middle you have a smooth walled passage for the wort that can be cleaned very easily. If you are passing the wort over a tube the potential for contamination is exponentially increased because of the numerous small crevices. Of course there are ways to mitigate this, like using a welder to fuse the fittings, but the additional time and effort turned me off.

I'd be very interested to see what the effectiveness of the result would be. A tube in shell cooler has some significant advantages over a plate chiller, namely beer porn quality and ability to pass pellet hops.

unfortunately your "tube in shell" design isn't as effective as a CFC or plate chiller. I just spoke with another one of our hydraulic engineers about his idea.

In theory, the three tube design with water outside, wort middle, and water inside would be about 30-40% more effective than a standard CFC. This is obviously in an ideal world and with the necessity for cleanliness at the bottom of the priorities list.

The idea of 2-4 tubes carrying the wort with an outer tube carrying the cooling water would be the most efficient, however having a manifold build to combine the inner tubes at the input and output sides would be costly. Fortunately, I have a master machinist at my disposal that loves cheap beer (red dog). I'll keep posting as our discussions continue.

Yuri_Rage said:

Sure, the theoretical cooling rate would be fantastic, but in reality, how fast can you push wort through the space you're providing? In either scheme (water/water/wort, or water/wort/water), you're severely limiting the flow volume via 1/4" tubing or 1/2" stuffed full of 1/4". It's a fantastic idea, but you may want to consider using some larger diameter tubing to maximize the effectiveness.

Click to expand...

Couldn't have said it better myself.

I think the one place you would benefit is the size of the CFC. Theoretically you could probably cut the size in half from say a dozen coils to six coils. Is that really something we're all looking for though?

I bet you could increase the efficiency of the CFC by introducing some type of "nub" throughout the coils, creating a more turbulent flow. If you were to take a cross-section of the CFC mid-cooling, you would notice the center of the wort to be hot, and anything along the walls of the copper tubing to be cool. Similarly for the water, close to the walls of the copper would be warm, and along the walls of the garden hose cool. If we could introduce some turbulence within the hose/copper, this could potentially "mock" putting an additional coil inside of the inner coil.

...okay, now I need a drink

You'de be better of with just a ragular CFC and making some sort of pre-chiller for the water.

the whole idea of this is to try and come up with a cfc that doesn't need a pre-chiller. If everyone just accepts what they already have, then we would lose all drive to try and increase efficiency in every thing we do.

Convoluted CFC's already exist which do increase the turbidity of the cooling water.

How about...

1. take an all-copper standard CFC
2. reverse it so the wort is in the outside pipe
3. put in a bucket/large pipe and run cold water through the inside tube as well as the bucket
4. ???
5. Profit!

This would achieve the water wort water effect but with larger tubing...

There's many more ways out there to cool wort than just a simple CFC, but where do you draw the line between efficieny and cost? If you have a water source that runs at 85°, it doesn't matter how good your chiller is, your wort won't get any colder than your cooling water. You'd spend less money and get more cooling by just making a 50' CFC rather than a water/wort/water exchanger.

hexmonkey said:

How about...

1. take an all-copper standard CFC
2. reverse it so the wort is in the outside pipe
3. put in a bucket/large pipe and run cold water through the inside tube as well as the bucket
4. ???
5. Profit!

This would achieve the water wort water effect but with larger tubing...

Click to expand...

Yea, or...take that all copper chiller, and surround it with a large PVC pipe.

Then run the cooling water on the inside tube and the PVC pipe, with the wort in the larger copper tube. That way you have cold water running on the outside, rather than just sitting there.

How about the water/wort/water with the middle tubing convoluted?

All of this is for a paper I've been working on for a while for cost effective Heat exchangers for home brewing... The issue with building a hybrid chiller (coil in bucket) style is that you aren't taking advantage of the counter flow chilling effect. Even with a coil with wort traveling down the coil towards the bottom of the bucket and then out, with a water input in the bottom of the sealed container and flowing out of the top, you still aren't getting the same efficiency of a CFC.

Does it have to be a CFC? I've wondered if adding thin "fins" such as you would find in a baseboard heating element, would greatly increase efficiency of a standard chiller. Downfall? A lot of work to build = $$

No duh, but it would probably be a lot easier/cheaper to build a regular, all copper CFC, then turn that whole thing into a 'tube in shell' design. That way, you have the efficiency of the CFC, PLUS you'd have cold water flowing on the outside of the CFC. Run the wort in the outer tube and you hit it from both sides!

I would thing that it would be cheaper, and you wouldn't have to worry about restricting your flow with the extra inner tube.

You're still not going to be able to chill down any more than the temp of the tap water. All the 25' garden hose-type CFC's I've seen in action do this no problem in the first pass.

The real issue with wort chilling in this fashion (CFC/plate) is not really the dynamics of chilling, but more getting the coolant water as cold as possible.

I disagree, by maximizing the efficiency of the chiller those of us who are blessed with cold tap water can completely avoid using ice or a more advanced contrivance for chilling the coolant water.

Also, there seems to be some confusion here with terminology; mostly in the "a square is a rectangle, but a rectangle is not necessarily a square"-type situation. Both "tube in shell" chillers and plate chillers are (usually) CFCs.

GearBeer said:

I disagree, by maximizing the efficiency of the chiller those of us who are blessed with cold tap water can completely avoid using ice or a more advanced contrivance for chilling the coolant water.

Also, there seems to be some confusion here with terminology; mostly in the "a square is a rectangle, but a rectangle is not necessarily a square"-type situation. Both "tube in shell" chillers and plate chillers are (usually) CFCs.

Click to expand...

I'm saying in my experience the chiller is already maxed out on efficiency. In one pass through, the wort ends up in the fermentor at the same temperature of the tap water. You can't get it colder without pumping colder water through either a pond-pump or prechilling.

I think the whole point to the OP is to maximize efficiency of a CFC. Sure you get your wort down to ground water temp when it comes out of the regular CFC, but how can we do the same thing using the less material & water? That's what efficiency is.

If we really wanted to we could build a whole elaborate refridgeration system that will get the wort to 70* in no time. It wouldn't be more cost efficient then a regular CFC though.

JMD87 said:

I think the whole point to the OP is to maximize efficiency of a CFC. Sure you get your wort down to ground water temp when it comes out of the regular CFC, but how can we do the same thing using the less material & water? That's what efficiency is.

If we really wanted to we could build a whole elaborate refridgeration system that will get the wort to 70* in no time. It wouldn't be more cost efficient then a regular CFC though.

Click to expand...

Right, but you're not going to do that through re-design of the chiller. You will do that through finding a way of cooling the incoming water out of the tap. Nothing doing with the actual chiller.

PseudoChef said:

Right, but you're not going to do that through re-design of the chiller. You will do that through finding a way of cooling the incoming water out of the tap. Nothing doing with the actual chiller.

Click to expand...

I kindly disagree. That's like saying we can't make our automobiles more efficient without using a different engine. Cars have become so efficient over the past 20 years, and it's because we keep trying to improve an existing design.

Few things, a plate chiller isn't really a CFC by any means. A plate chiller is set up to have a layer of cold water or cooling liquid sandwiched next to a plate of hot wort. The more sandwiches you make, the more efficient it becomes. The whole idea of the plate chiller is surface area of hot wort being exposed to a cooling liquid.

A "tube in shell" design is not a CFC either. This "hybrid" design is meant more as a reverse immersion chiller.

Don't forget, CFC means COUNTER FLOWING liquids. This counterflow design increases the efficiency.

As to what others have said regarding temp. differentials, etc., the whole point of trying to push the envelope on the CFC designs is from looking at HEX systems that the military currently uses. Obviously I can't tell you what they are, but this idea of mine mirrors one to some extent.

Obviously you cannot cool a hot liquid past the temperature of the cooling liquid, however if we can get to that thermal equalibrium faster, why would that be a problem? In the end it all comes down to a ratio of efficiency to cost. A standard CFC can be easily built, and it works, but why not try and make it work better? It's quite hard for people to DIY a plate chiller, however a CFC that costs the same as a plate chiller retail and is as effective as one, while being able to build it yourself seems like my ideal product...

JMD87 said:

I kindly disagree. That's like saying we can't make our automobiles more efficient without using a different engine. Cars have become so efficient over the past 20 years, and it's because we keep trying to improve an existing design.

Click to expand...

There's no way to use 70 degree water to chill wort to 65. You cool the water to 65, then you can chill wort to 65.

PseudoChef said:

Right, but you're not going to do that through re-design of the chiller. You will do that through finding a way of cooling the incoming water out of the tap. Nothing doing with the actual chiller.

Click to expand...

Thats the only way you could make the chiller more efficient... By lowering the temperature of your cooling water, you aren't increasing efficiency.

I suppose it depends on your definition of efficiency, however in my mind, I look at it like this: How can I make product "A" do the same thing it already does faster, without changing its input and output. The only way to do that is by changing the way it works. The whole principal of an HEX is to heat up or cool down a liquid by means of heat transfer over a large surface area.

PseudoChef said:

There's no way to use 70 degree water to chill wort to 65. You cool the water to 65, then you can chill wort to 65.

Click to expand...

Thats not what I'm trying to do. Lets assume that I can chill 212*F Wort to 70*F in 15 minutes using 70*F tap water.

Thus, (212-70)/15 would be my efficiency.

Now, I want to make (212-70)/(15/2)

Thats what I'm trying to do. I don't want to change the water temperature, I just want to increase efficiency.

Psst, a plate heat exchanger and a tube in shell are both counterflow applications.
The coolant runs the reverse of the liquid to be cooled.

I would agree as for the plate exchanger. What would be your definition for a tube in shell application in home brewing?

Ok, then that will depend on the flow rate of the wort. Are you using a pump or gravity?