Chilling Fast vs Slow (flow rate)?

[boondocksaint]

I have a Kal clone set up (3 20 Gal kettles; Electric Control Panel; two Chugger pumps, etc) and use the same CFC chiller recommended on the (www.theelectricbrewery.com) website.

Chilling Post boil: My usual set up is to use my old immersion chiller in a bucket with ice/water and run the water from the sink - through the immersion chiller (in ice water) - then through the CFC - and back to the sink to drain.
The wort is run from the BK through the pump and through the CFC.

My brew buddy and I have been having a disagreement about the flow rate of both the water and wort and which is more efficient. He wants to run the wort much faster and recirc back through the BK; while the water is running full blast. I feel like slowing the wort way down and running it through (once) is the way to go.

I know on the Brew Day Step By Step section, Kal recommends running it through once and straight into the fermentor.
Should the flow rates match? Is there a benefit or potential issues with one over the other (fast vs slow)?

Cheers all!
*If this topic has already been litigated, please feel free to point me in that direction!

 

[JohnSand]

I remember a similar thread about immersion chillers. I think the conclusions were mixed. I do believe that the cooling water can go through so fast that it doesn't have time to absorb the heat. With my IC, I slow the flow down as the wort cools, just judging by the feel of the discharged water. If it isn't hot, it isn't working.

 

[McMullan]

I find reducing water flow rate increases relative cooling efficiency as the temperature difference between wort and cooling water gets smaller. With both my IC and CFC. It seems to be a very dynamic process and not governed by a single predictable factor. Initially, I'll have the water on full blast. By the end of cooling, it's on a trickle.

 

[tripelthelightfantastic]

my pump + IC has a constant flow rate, slowing the flow rate down as the wort gets cooler is a good idea i need to try by restricting the output tube...
While its not related to flow rate, one thing i find gives me a big temp drop is stirring the wort or using the IC to stir the wort and distribute the cold temp from the IC

 

[McMullan]

one thing i find gives me a big temp drop is stirring the wort or using the IC to stir the wort

This is why I moved to recirculating through an CFC, to break up temperature stratification in the kettle.

 

[tripelthelightfantastic]

a CFC would make a nice Easter gift - can you use it for hop stands?

 

[McMullan]

a CFC would make a nice Easter gift - can you use it for hop stands?

Yes, I do. Whole hops in a spider mainly and sometimes through a HopRocket, too. If it's just a half batch I'll use the IC without recirculating.

 

[tripelthelightfantastic]

nice - thanks McMullan. now to find one to buy

 

[Scout]

I think you are right, if the flow is too fast it won't cool as efficiently. I have a plate chiller and set up the flow so that the wort comes out at or close to pitching temp. I think of it as cooling during the transfer to fermenter. Two birds with one stone kinda thing.

 

[ryan_george]

If your goal is absolute maximum cooling rate (minimal cooling time), you want both flows to be as high as possible. The hottest wort in contact with the coldest coolant will give the greatest heat/energy transfer - this is not up for debate, that's science.

Depending on your setup you may not want full flow on each, for example if you are running through a CFC directly to your fermenter. In this case you will need to adjust the wort and coolant flow to achieve your desired output temperature. I would still aim for higher flow on both systems (rather than less) so that you achieve a faster overall cooling time. Someone with a very efficient CFC may need to have their wort on full flow and back off the coolant (so as to not overcool). Someone with a less efficient CFC may need to run full coolant and back off the wort flow. If you are using an IC and performing a "bulk cool" then you still want the wort recirculating as much as possible and the coolant flow as high as possible.

I see it mentioned a lot that if you run the coolant too fast it "won't have time to absorb the heat". Yes, the coolant might be coming out "cold", but it is flowing faster and still pulling more heat out of the system (on a time basis) than if you run it slow and the coolant is coming out warm. To maximize the heat transfer you want the greatest difference in temperature between the two fluids.