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**AZ_IPA** · 06-15-2009, 04:03 AM

I tried some searches and came up with not too much...

here's my question - what's the general consensus for flow rates for a gravity fed CFC system?

- boil kettle wide open and CFC hose wide open?
- boil kettle 1/2 open CFC hose wide open?
- boil kettle wide open and CFC hose 1/2 open?
- both half open?

my intuition says that with my ~62*F tap water, I want as much contact with the hot wort as possible...

thanks!

JMSetzler · 06-15-2009, 04:43 AM

The slower your flow rate from the boil kettle and the higher your flow rate through the hose, the closer to that 62° you will get...

**AZ_IPA** · 06-15-2009, 06:25 PM

Quote:

Originally Posted by JMSetzler

The slower your flow rate from the boil kettle and the higher your flow rate through the hose, the closer to that 62° you will get...

I would think you would want them both at about the same right - if the water is flowing too fast it won't pick up enough heat, right?

**Bobby_M** · 06-15-2009, 06:50 PM

If we're talking about the 3/8" OD x 25' deal, you should be able to run wort wide open, tap water at about 1/2 and get within a couple degrees of the coolant temp especially on a gravity drain. If you find that the wort output is a bit too cool, you can throttle back the coolant even more which is common in the winter. When my tap is 45F, I pump the wort full speed and have the coolant valve at about 1/8th open.

When coolant temp hits 70F in mid summer, I run the wort at about 1/2 and the coolant at full. That gets the wort out at about 73F. You'll have to experiment and measure the wort output temp often.

**dstar26t** · 06-15-2009, 06:56 PM

If you're going to experiment with water before using wort, keep in mind that water is more easily cooled than wort. I found it to be ~7 degrees under similar circumstances if I remember correctly.

**AZ_IPA** · 06-15-2009, 08:20 PM

Thanks for the input fellas.

yes Bobby, it's a 3/8" OD x 25' with a gravity drain. I'll start wide-open wort and 1/2 coolant, and adjust as needed.

goatchze · 06-15-2009, 08:59 PM

AZ,

Don't forget that the height of your kettle over the exit of your CFC is going to make a difference. The velocity of the wort leaving the CFC (if we neglect friction) is

v=Sqrt(2gh)

where
v=velocity, ft/s
g=accel gravity (32.2 ft/s^2)
h=height from fluid level in kettle to bottom of CFC, ft

your volumetric flow, then is V=v*Pi*r^2

where
V=volumetric flow, ft^3/s
Pi=3.14
r=diameter of copper tube in ft

Point is: the bigger the h, the faster the wort flows. The faster the wort flows, the faster the water will need to flow through a fixed exchanger!

JMSetzler · 06-15-2009, 09:23 PM

Quote:

Originally Posted by goatchze

AZ,

Don't forget that the height of your kettle over the exit of your CFC is going to make a difference. The velocity of the wort leaving the CFC (if we neglect friction) is

v=Sqrt(2gh)

where
v=velocity, ft/s
g=accel gravity (32.2 ft/s^2)
h=height from fluid level in kettle to bottom of CFC, ft

your volumetric flow, then is V=v*Pi*r^2

where
V=volumetric flow, ft^3/s
Pi=3.14
r=diameter of copper tube in ft

Point is: the bigger the h, the faster the wort flows. The faster the wort flows, the faster the water will need to flow through a fixed exchanger!

There is a terminal velocity that you failed to mention

If the height of the fluid drain from the kettle is 60' or so above the ground, the draining wort will reach terminal velocity where elevating the source any higher would not impact the flow rate

**AZ_IPA** · 06-15-2009, 09:34 PM

Quote:

Originally Posted by JMSetzler

There is a terminal velocity that you failed to mention

If the height of the fluid drain from the kettle is 60' or so above the ground, the draining wort will reach terminal velocity where elevating the source any higher would not impact the flow rate

well, then I'm screwed - mine is about 75' above the ground

I ran 5.75 gallons of water through it yesterday in about 17 minutes, so I'm assuming a drain time of ~20 for wort

JMSetzler · 06-15-2009, 10:31 PM

Quote:

Originally Posted by AZ_IPA

well, then I'm screwed - mine is about 75' above the ground

I ran 5.75 gallons of water through it yesterday in about 17 minutes, so I'm assuming a drain time of ~20 for wort

I have very little experience with counterflow chillers. I built one way back in the early days of my homebrewing. I didn't like it much and switched back to my IC. I even had a submersible pump that was connected to a rheostat where I could control my flow through the chiller. It was fun to build but for some reason that I can't exactly explain, I just like the IC.

I'm thinking about buying another submersible pump and using it with the immersion chiller and recirculating ice water in the warmer months...