Immersion chiller upgrade tests, series vs parallel

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cfrazier77

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In a previous thread, https://www.homebrewtalk.com/f51/immersion-chiller-upgrade-redneck-fermentation-252421/ , it was suggested to split the incoming water and have it go to each coil, parallel. I had it set up for the water to go from one coil and into the second, series. I said that I would test the chiller both ways and had time this afternoon to do it.
https://www.homebrewtalk.com/attachment.php?attachmentid=28170&stc=1&d=1308793107
https://www.homebrewtalk.com/attachment.php?attachmentid=28171&stc=1&d=1308793245
Here are the details of the test.
I brought 10 gallons of water to boil in a keggle outside and it was 87 degrees.
The water temp out of the hose was 62.5 degrees.
I started cooling once I had a roiling boil. I took the temp at 10 minutes, the time at 90 degrees, and the time at 80 degrees.

Series,
After ten minutes, 102 degrees
90 degrees 12 minutes
80 degrees 17 minutes

Parallel
After ten minutes, 106 degrees
90 degrees 14 minutes
80 degrees 18 minutes

So it came out that series worked better in this case than parallel. So if you have a 25' immersion chiller adding a second coil can really improve cooling.

IMG_7292.jpg


IMG_7296.jpg
 
Wow. All things being equal (flow rate, water temp) I thought the parallel would be quicker than in series.
 
Wow. All things being equal (flow rate, water temp) I thought the parallel would be quicker than in series.

I think that running it in series allows the outflowing water to become hotter, making the system more efficient. The temperature difference between water flowing in and water flowing out is directly related to the efficiency of the system. Nice work.
 
Since there is almost no real difference, why not use the smaller coil as a prechiller. That will honestly work the best.
 
Hmmm.... this goes against what my heat transfer classes taught. Not quite buying it yet.

The energy transfer is proportional to the temp difference between the wort and coil. Lets use the entering and exiting coil temps to get an average coil temp. With shorter coils, the average temp will be lower, since surface area of 1 coil is half the surface area of the system of coils, and has less contact time with the wort.

With 2 coils, at a lower avg temp, (assuming same flowrate for parallel or series configuration), the parallel should cool significantly faster.

I'm guessing a restriction in the supply caused a reduction in water flow. Hence, the question of water volume above is extremely relevant.
 
Hmmm.... this goes against what my heat transfer classes taught. Not quite buying it yet.

The energy transfer is proportional to the temp difference between the wort and coil. Lets use the entering and exiting coil temps to get an average coil temp. With shorter coils, the average temp will be lower, since surface area of 1 coil is half the surface area of the system of coils, and has less contact time with the wort.

With 2 coils, at a lower avg temp, (assuming same flowrate for parallel or series configuration), the parallel should cool significantly faster.

I'm guessing a restriction in the supply caused a reduction in water flow. Hence, the question of water volume above is extremely relevant.

Yeah, this is curious to me as well.

With shorter coils, average temp should be lower. Also, if the supply hose, is significantly larger in diameter than the tubing, (garden hose, for example), then your flowrate through the parallel setup will be much higher, (think resistors in parallel vs. series, for you electrical nuts). Higher flowrate = faster, (though less efficient), cooling.

Of course, if the flow is provided by a kitchen sink, which is only using 3/8" supply hose, then the flowrate difference wouldn't be as pronounced.
 
yeah, I'm interested in how exactly you hooked up the water supply for series vs. parallel? Any supply restrictions would play a big factor in the efficiency of the parallel coils.
 
Since there is almost no real difference, why not use the smaller coil as a prechiller. That will honestly work the best.

I did not test just using the original 25' chiller. But from using it in the past it by itself takes at least 10 minutes longer than either method tried here.
 
Hmmm.... this goes against what my heat transfer classes taught. Not quite buying it yet.

The energy transfer is proportional to the temp difference between the wort and coil. Lets use the entering and exiting coil temps to get an average coil temp. With shorter coils, the average temp will be lower, since surface area of 1 coil is half the surface area of the system of coils, and has less contact time with the wort.

With 2 coils, at a lower avg temp, (assuming same flowrate for parallel or series configuration), the parallel should cool significantly faster.

I'm guessing a restriction in the supply caused a reduction in water flow. Hence, the question of water volume above is extremely relevant.

I used a garden hose, but I used a T to split the water. My other hobby is that I am a fire fighter and from that I know that this type of splitting, vs. a Y, reduces water flow. It was the only thing that I had available though to split the incoming water.

Sorry, I did not think to mention this before until I read this and the previous post. Please don't think that I have a desired outcome in this, I don't and don't care which works better other than wanting to use whichever is best.
 
Please don't think that I have a desired outcome in this, I don't and don't care which works better other than wanting to use whichever is best.

Well, I for one applaud you for

1) setting up an experiment, and
2) posting your results for analysis


I think the majority of posters out there don't bother experimenting, and of the ones that do, few of them post data (though they might post results).

For what it's worth, I use an immersion chiller with 2 runs of 25' 1/4" copper tubing, in parallel. Last brew session, I used about 10 gal of cooling water (at 75°F) to get my 5 gal of boiling wort down to 85°F. During the summer, I pitch warm and hopefully, my ferm chamber brings the temp down before the yeast get real active.

The hot, spent water goes into 5 gal buckets that I use as wash basins... that's the only reason I know I used 10 gallons. I cut off the hose when 2 were full. I did not, however, record the time it took to fill them. Maybe 30-40 min?

I suppose I could dust off my old textbooks and calculate my chiller's efficiency with the above #'s, but I try not be be such a nerd anymore. Now I have bigger things to worry about, like the damn rabbits eating my hops leaves.


I was thinking, did you stir the wort at all during either test? That's probably the greatest influence on efficiency, outside of the hardware setup.
 
I actually kinda expected your results, now the actual flow rate matters, but I have a suspicion that maintaining turbulent flow is more important for chiller operation. The other thing I noticed is while the results show a mathematically different result, but I am unsure how statistically significant the result is (IE there may be other unexplained differences that cause the different result such as wind speed, or changes in flow rate to your supply causing the difference).
Thanks for posting your results and taking the initiative to conduct an experiment.
 
Great work, it's nice to have some boots on the ground versus theory sometimes. I'm looking to upgrade my 25' chiller (either by doing the parallel/series trick or just getting a plate chiller) and this is quite helpful.

JP, how much did you crank open your chill water source? Just enough to get water flowing or did you really open it up? I'm just curious because I usually go through way more than 10 gallons of water in 30-40 minutes and would love some input on reducing that amount, what with summertime coming up and my well being quite, quite shallow.
 
Great work, it's nice to have some boots on the ground versus theory sometimes. I'm looking to upgrade my 25' chiller (either by doing the parallel/series trick or just getting a plate chiller) and this is quite helpful.

JP, how much did you crank open your chill water source? Just enough to get water flowing or did you really open it up? I'm just curious because I usually go through way more than 10 gallons of water in 30-40 minutes and would love some input on reducing that amount, what with summertime coming up and my well being quite, quite shallow.

My 2 coils are fed from a 3/4" 25' garden hose, with the spigot wide open. City water fed.

The 1/4" copper (and the required brass fittings) have a ton of flow resistance as compared to the 3/8" or 1/2" that others use. "Max efficiency" wasn't my primary design criteria; cost was. I got a good deal on 25' of 1/4" copper, so I bought 2 rolls (for less than the cost of a roll of 3/8"). I figured parallel flow would be the best way to use them.

We have to also define efficiency here. There is max efficiency per volume of water (slow flow would give max "efficiency" here), or per unit of time (fast flow would give max efficiency). Depends on what your goals are. I'd say most of us are going for shortest time.

Mine's efficient for water use, but not so much with respect to time.
 
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