Is a spiral really the most efficient shape for a wort chiller?

Is a spiral really the most efficient shape for a wort chiller? I'm just thinking out loud here because at a meeting we were talking about making a wort chiller and how to bend it.

BUT - is it the best shape? Why not a cone like a top with more longer rings near the top where the warm wort rises. Or why not like a spider web or some other pattern. Is a spiral just a default shape?

Spiral is easy to build and clean.

There have been many iterations of all manner of spagetti strung chillers.

Spiral is easier.

Well, spiral is better than straight. In order to improve on this you would need sharper corners to create more turbulent flow. You could do this is by using elbows. A lot of elbows. The small gain in efficiency would probably not merit all of the soldering.

I would think the more surface area of the chiller in contact with the wort the better. If you shape it like a top you rob the chiller of surface area.

A spiral chiller that is about the same diameter as the pot will produce a strong flow down the sides with an upwelling in the middle. But I stir my wort, so it hardly matters.

david-42 - that was what I was getting at - how does the wort flow when it's being chilled. Granted any gains are going to be minimal but I was curious what the MOST efficient way would be.

I don't understand why the down flow would be on the sides and up in the middle. What would cause this

Grinder12000 said:

david-42 - that was what I was getting at - how does the wort flow when it's being chilled. Granted any gains are going to be minimal but I was curious what the MOST efficient way would be.

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My simple spiral chiller cost me 30 bucks, took less than 5 minutes to assemble and chills 5 gallons of wort from boiling to 70 degrees in about twenty minutes. A more efficient iteration of this design might cool 10% faster. That's two minutes. That's not worth worrying about, in my opinion.

I don't understand why the down flow would be on the sides and up in the middle. What would cause this

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It's convection currents forced by cooler, denser wort sinking around the cooler, displacing the warmer wort to the surface.

I was talking about this with an enginerd at work that came from the nuclear energy world. He said the heat exchangers they use look more like a gatling gun (revolving barrel machine gun) they don't move but thats the best I can explain it w/o pics.

I've gotta agree... the amount of labor involved is not worth the small gains.

Flyin said:

I was talking about this with an enginerd at work that came from the nuclear energy world. He said the heat exchangers they use look more like a gatling gun (revolving barrel machine gun) they don't move but thats the best I can explain it w/o pics.

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Sounds like a shell and tube design. Catt22 made something like this. There is a thread around here somewhere...

WHY WHY WHY do people think I'm worried about making something faster - All I'm wondering is WHAT the most efficient configuration is.

I get quoted and STILL people respond with basically using my words!

Well, since a chiller is intended to cool the wort down quickly, efficiency would translate into speed. I suppose if you were in an area that had limited water resources, you might be looking at a more efficient chiller to cool in the same amount of time using less water, but that's not usually the case. If it's not a speed increase, what WOULD your definition of a more efficient cooler be?

Grinder12000 said:

WHY WHY WHY do people think I'm worried about making something faster - All I'm wondering is WHAT the most efficient configuration is.

I get quoted and STILL people respond with basically using my words!

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Maybe people equate efficient with faster when discussing cooling a hot liquid? Why don't you tell us what you'd like to hear, and we can work on it.

The efficiency depends on turbulence of the flow around the chiller, effective heat transfer through the heat exchanger, and allowing both fluids to fully absorb the heat of the other.

The shape of the chiller does not effect any of these. Flow within your chiller will always be turbulent (see my blog for a detailed explanation and the physics behind it). Making the flow within your wort turbulent is the most important thing. As long as the wort flow is turbulent, the shape of the chiller is ineffectual.

As a side note, I never understand why people care about chilling efficiency. Who cares? And why? The most efficient way to cool would be to have a very large heat exchanger and run the coolant very slowly. It will take way longer to chill but will be more efficient, but what is the point? To extend the brew day?

Just ram as much cold water through the chiller as you can. Chill fast and save the water for later if you need to. A 55g drum can be found for super cheap on CL if you are really concerned about it.

Grinder12000 said:

david-42 - that was what I was getting at - how does the wort flow when it's being chilled. Granted any gains are going to be minimal but I was curious what the MOST efficient way would be.

I don't understand why the down flow would be on the sides and up in the middle. What would cause this

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The downward flow is driven by the cooled wort being denser than the hot wort. Since the cooling occurs at the coils (near the outside), the upward flow has to be in the middle.

I spiraled mine from each end to meet in the middle then overlapped left and right so it looks like a ribcage. Im not sure if its any more efficient than a staight stack, but there is copper touching all areas of the wort. Plus it looks cool. I got the idea from some pics I saw here somewhere.

Convection currents within the beer will not be enough to have any appreciable agitation to the wort. That is why the shape is not a factor. Your cooling times will be MUCH longer if you do not actively move the wort around the chiller regardless of the shape of the heat exchanger.

I take hold of my chiller every couple of mins and move it up and down in the kettle a few times to stir. Each time I do that my thermo reading drops about 5 degrees.

Boerderij_Kabouter said:

Convection currents within the beer will not be enough to have any appreciable agitation to the wort. That is why the shape is not a factor. Your cooling times will be MUCH longer if you do not actively move the wort around the chiller regardless of the shape of the heat exchanger.

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*dropping out of lurk*

So then would Jamil's design with the recirulating doohickey, then be the "most efficient" (at least by the op's definition) design currently out there?





http://www.mrmalty.com/chiller.php

For those unfamiliar with it, you run your wort through a march pump and recirculated it through the propeller thingy which vortexes the wort as it moves around the chiller coils in the kettle.

I used it on a buddy's system didn't really seem to make an appreciable difference, in terms of time...But we were doing a 10 gallon batch, and it might have been to me that it took the same amount of time to do that then it does for me to do 5 gallons with my standard IC. I was drinking and cold, and I guess, really didn't stand there with a stopwatch timing it so I could be wrong.

The most efficient will be a plate chiller. Beyond that, jamil's whirlpool design is far and away the best.

I did a side by side with the same chiller when I first installed my recirculation system. No wort flow 45 minutes, with wort whirlpool 25. Both with 55º ground water 10g batches with a 50' 1/2" SS coil.

Constant wort movement is by far the biggest thing you can control in your cooling. It will have a larger effect even that coolant temp. If you are not moving the wort, you aren't really exchanging heat with the cold water.

To do an easy test:

1. start running your chiller, the waste water will be hot.
2. when the waste water starts to cool, move the chiller around
3. is that water heating back up like crazy?
4. I thought so.

It really is all simple thermodynamics, but a lot of people don't like to believe in science.

Boerderij_Kabouter said:

It really is all simple thermodynamics, but a lot of people don't like to believe in science.

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Meh, you call it science, I call it fermentation fairies...but it's really just the same thing using different names.

Grinder12000 said:

WHY WHY WHY do people think I'm worried about making something faster - All I'm wondering is WHAT the most efficient configuration is.

I get quoted and STILL people respond with basically using my words!

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Because most chillers are already more efficient than matters. The slowdown is not being able to push enough cold water through.

maskednegator said:

It's convection currents forced by cooler, denser wort sinking around the cooler, displacing the warmer wort to the surface.

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To further expand on this - the warmest part of the pot will be the center because you are cooling near the edges. That warmer wort will rise and cooler wort from the sides will come under to fill in. That causes a displacement around the edges at the top which will be filled by the rising warm wort. This convection is not a high volume turbulent flow but it is enough to move some wort around. You sort of see the effect in a "rolling boil" where the bubbles rise more in the center if you are heating evenly due to temp loss at the edge of the pot causing a sort of volcano look to the boil.

As to the original question of design efficiency of the coil in and of itself, I'd say you could probably do better with something that decreased the max distances between coils and wort (such as the ribcage design) but I think we don't worry about the design much because the bigger issues for heat transfer are temp differential and surface area so you can do a lot to increase your cooling efficiency without changing the simple design of the chiller. Inefficient or otherwise the water coming out of most of the basic designs is approaching the wort temp so you would need to drop your coolant temp to do much better - hench prechillers or recirculated icewater designs. It's an interesting theoretical question but without much practical application and that's why you aren't getting much in the way of a specific answer.

I know it is the internet and all, so you don't have to listen to me, but this thread and many others like it just make me want to grate my face against a cheese grater...

The convection formed in cooling wort will affect almost nothing. The movement is so slow and the convection so small that it takes forever. You don't have to believe me, it isn't my time being wasted.

Forced convection will cool tremendously faster than natural convection. This really isn't arguable.

I agree with BK 100% here. Any talk about which shape is better at creating convection currents is completely moot unless your ONLY goal is to skip a recirculation pump, skip motorized stirring, or skip physical stirring during chilling. I highly doubt that is the goal.

So, the short answer is that any shape that fits in your brew kettle and still allows for good physical agitation of the wort is the design which is already perfect.

I'll say it. Anyone who runs an IC with the wort sitting still is a wanker.