Do I have turbulent flow in my chiller?

So this question comes up a lot so I finally took the time and crunched the numbers. People often ask, 'how can I make my chiller more efficient?' An answer that commonly pops up is, 'add a wire to the inner diameter of the tube to increase turbulence.' I often chime in to say I am 90% sure that the flow is already turbulent, so adding a wire will do nothing. Well, I finally ran the numbers to see what kind of liquid flow rates we need to get turbulent flow in our chillers. To determine which type of flow exists in your tubing calculate the following:
Flow rate of the fluid in GPM - Q Specific gravity of the fluid - G Pipe inside diameter in inches - D Fluid viscosity in centipoise - V Use the following equation to determine the REYNOLDS NUMBER: REYNOLDS NUMBER = RE = [3160 x Q x G] / [D x V]
Flow conditions with a Reynolds Number greater than 4000 is fully developed turbulent flow. A Reynolds Number less than 2000 is laminar flow. It requires a Reynolds number greater than 4000 to maintain accuracy.
So we set up the equation to find a flow rate (Q) for a given tube to maintain turbulent flow. We will assume our numbers are for water. Wort will be very close to this and if anything would trend to more turbulent flow.
G = 1 g/cm3 V = 1.0020 cP RE = 4000 D = desired tubing Q (gpm) = [4000 x D x V] / [3160 x G] = [4000 x D x 1.0020] / [3160 x 1] Q (gpm) = [4008 x D] / 3160 so... for a 1/2" diameter tube Q (gpm) = [4008 x 1/2] / 3160 = 0.634 gpm
This means in order to maintain a turbulent flow in a perfectly straight pipe with a 1/2" diameter, the water must be flowing at 0.634 gallons per minute. Add the turns we have in our chillers and that number drops significantly. for 5/8" tubing Q = 0.793 gpm. Typical garden hose flow is between 5-6.5 gallons per minute. Basically, we always have turbulent flow so extra baffles are just a waste and are slowing down fluid flow. I hope this helps to answer some questions.
Cheers,
Justin

 

[DMCarson]

I use a drill motor and a stainless steel jiffy mixer(5-10 gal) which creates a very efficient tornado of post boil wort forcing it through my wort chiller(while ground water is ran through it) which is 3/8" nom(1/2" od) copper (cant remember but either 10' or 20'). I got the thing for about 50$ and I cooled 5.5 gal to 66 degrees in 6 minutes, my 10 gallon batch (10.5 g or post boil wort) cooled to 68 degrees in 8 minutes, both produced condensation on the outside of my SS converted keg/keggle. The mixer fits perfectly in the middle of the corney diameter size chiller. I drained my wort and pitched.

 

[HoeBrew]

Unrelated to the turbulent flow, that is one of the coolest looking wort chillers I have seen... (slow-clapping)

 

[Norselord]

its not the turbulent flow within the coil that is limiting heat transfer - it is the motion across the coil for the liquid being cooled that is going to be more important - since it has the higher relative thermal mass.