optimal CFC flow direction?

[Tom R]

I understand that wort and water flow opposite directions in a CFC.
But is cooling more efficient when the wort enters at the bottom of the coil, and the water at the top, or vice-versa? Does it matter at all?

 

[bailey mountain brewer]

I have mine set up so the wort comes in the bottom and the water enters the top. As far as I know it makes no difference.

 

[ScrewyBrewer]

The idea is that cooling water is introduced nearest to the point where wort enters the fermentor in an effort to cool the wort down close to the target pitching temperature. The cooling water then travels on in the direction to the point where the hottest wort enters the chiller, in an effort to pre-cool the hot wort.

In my experience, the improved efficiency of this configuration can easily be verified by measuring the temperature of the cooling water as it leaves the chiller, it can be ~20F degrees cooler than the hot wort entering the chiller. A 'convoluted counterflow chiller' increases the convection of the cooling water in the chiller by creating additional turbulence which further increases the cooling efficiency of the chiller.

 

[Tom R]

The idea is that cooling water is introduced nearest to the point where wort enters the fermentor in an effort to cool the wort down close to the target pitching temperature. The cooling water then travels on in the direction to the point where the hottest wort enters the chiller, in an effort to pre-cool the hot wort.

In my experience, the improved efficiency of this configuration can easily be verified by measuring the temperature of the cooling water as it leaves the chiller. A 'convoluted counterflow chiller' increases the convection of the cooling water in the chiller by creating the additional turbulence needed to increases the efficiency of the cooling water.

I'm sure we all agree that the two liquids flow opposite each other.
Let me re-phrase the question: Should the wort enter the top coil of the CFC, or the bottom one?

 

[ScrewyBrewer]

I'm sure we all agree that the two liquids flow opposite each other.
Let me re-phrase the question: Should the wort enter the top coil of the CFC, or the bottom one?

The configuration I use has the hot wort entering at the top and the cooled wort exiting at the bottom. This allows gravity to move the hot wort into the chiller and tap water pressure to move the cooling water up into the chiller.

 

[bailey mountain brewer]

It really does not matter, water is going to contact the same amount of surface area no matter which way it flows, up or down. Hell you can mount the coil sideways so it comes in on left and exits on the right if you want to. The temperature of your ground water matters more then anything with a CFC.

 

[eric19312]

Your configuration may be different from mine but I have the cold tap water going into the top and the cooled wort coming out of the top for reasons related to containing the mess when disconnecting.

First the hot cooling water comes out the bottom of the chiller and into a high temp hose leading downhill into a drain. All I have to do is unplug the hose at the cold water spigot and gravity will pull all the chilling water out of both hoses and the chiller. Then I can unhook the hoses from the chiller and put them away emptied of water.

Second I think I am able to contain the wort/trub mess a little easier when I finish pumping to the fermentor. I have two different hoses for the outflow from my chiller. One is shorty that has TC on one end to attach to the chiller and camlock on other end to attach to the whirlpool return on the kettle. The other one is about 10' long with TC on each end...used to pump from the chiller to the fermentor. To drain I close the ball valves on the kettle and the pump and the butterfly on the fermentor. I unhook the tube from the fermentor and catch the drip in a bucket and then drop the tube into the bucket. I keep the tube under the top of the chiller and unhook from the chiller. This lets the long tube that goes from my chiller to the fermentor fully empty into the bucket. Then I hook chiller and kettle back up with the shorty for further cleaning.

 

[bailey mountain brewer]

Your configuration may be different from mine but I have the cold tap water going into the top and the cooled wort coming out of the top for reasons related to containing the mess when disconnecting.

First the hot cooling water comes out the bottom of the chiller and into a high temp hose leading downhill into a drain. All I have to do is unplug the hose at the cold water spigot and gravity will pull all the chilling water out of both hoses and the chiller. Then I can unhook the hoses from the chiller and put them away emptied of water.

Second I think I am able to contain the wort/trub mess a little easier when I finish pumping to the fermentor. I have two different hoses for the outflow from my chiller. One is shorty that has TC on one end to attach to the chiller and camlock on other end to attach to the whirlpool return on the kettle. The other one is about 10' long with TC on each end...used to pump from the chiller to the fermentor. To drain I close the ball valves on the kettle and the pump and the butterfly on the fermentor. I unhook the tube from the fermentor and catch the drip in a bucket and then drop the tube into the bucket. I keep the tube under the top of the chiller and unhook from the chiller. This lets the long tube that goes from my chiller to the fermentor fully empty into the bucket. Then I hook chiller and kettle back up with the shorty for further cleaning.

This is exactly how I have mine set up, and for the same reasons. Only difference is that I use quick connects on all my fittings. But my transfer and clean up is the same. My chiller sits fairly close to floor level but I have a container that slides right under it to catch any drips and it is still high enough for gravity to flow when I disconnect the the cold water faucet.

 

[RufusBrewer]

If one method produces better results over the other, the explanation is going to interesting. I am going to assume if it makes a difference, the influence on the wort exiting the chiller is minimal.

One variable in using a CFC is the rate (e.g. gallons per minute) liquids go through the tubing. If you could figure which liquid would most benefit from using gravity "pulling" the water at a faster rate, that would give your answer.

Well that is my guess anyway.

Creating a reliable and repeatable test would be difficult in a typical homebrew set up would be difficult.

 

[Staticsouls]

Water temp
Material of cfc
Length of cfc tubing
Inner diameter of wort tube and water tube

These will be the biggest factors and variables in cooling. Colder water better cooling. Copper works better at heat transfer but is usually and undesirable vs stainless.

I've had the kegco cfc and it was so short it hardly changed the wort temp. I have the northern brewer cfc and while it works well the inner diameter of the wort tube is very small, and constricts flow. My best cooling practice uses my hlt with ice blocks. I recirculate the hlt water in the opposite direction the wort flows through the herms coil and I get single pass cooling everytime now matter the time of year or ground temp of water. Little things make big differences. I do introduce wort at the top of the coil so it all drains out the bottom if that makes any difference to you.

 

[Vale71]

I'm sure we all agree that the two liquids flow opposite each other.
Let me re-phrase the question: Should the wort enter the top coil of the CFC, or the bottom one?

Doesn't matter one bit. Both sides have liquid actively flowing through so natural convection plays no role at all in this case.

 

[TBA]

Can you use a CFC without a pump? Just gravity drawing the wort down and into the fermenter?

 

[eric19312]

Water temp
Material of cfc
Length of cfc tubing
Inner diameter of wort tube and water tube

How about flow rates of the chilling water and the wort
Also convoluted designs that increase surface area and/or disrupt laminar flows

 

[eric19312]

Can you use a CFC without a pump? Just gravity drawing the wort down and into the fermenter?

I tried this years ago with homebuilt CFC based on 25' copper tube in a garden hose. Higher gravity and very hoppy worts would literally get stuck in the hose and barely move. Got a pump.

 

[RufusBrewer]

Water temp
Material of cfc
Length of cfc tubing
Inner diameter of wort tube and water tube

These will be the biggest factors and variables in cooling. Colder water better cooling. Copper works better at heat transfer but is usually and undesirable vs stainless.

I am going to disagree with you here.

Difference in temperature between cooling water and wort is #1.

The volume (as in gallons per minute) of cooling water is a significant factor.

Cooling water volume is a greater factor than material and length of CFC. Between copper and SS (the materials we are talking) in practice are pretty close to being the same.

The length of the tubing is also not much of a factor (once you reach a certain point) when you consider the diminishing returns. Most of the transfer of heat happens early in the wort's journey where the temp differences is at it's peak. A 50' CFC is not much more effective than a 25' CFC. Certanly not 2 times

 

[Staticsouls]

Oh yeah that wasn't in a specific order or anything it was just a list of items that came to mind.

As far as length of coil it may not double the heat transfer but longer length would have longer contact time, depending on rate of flow. I would say optimal flow rate would be low and slow wort and fast cold water. The kegco has a large inner diameter wort tube and was very short, and it sucked balls. No matter what I did to the flow rate it would take forever.

 

[duncan.brown]

I agree with @RufusBrewer that the biggest factor is the temperature difference between the wort and the cooling water, your chillers ability to maintain that difference as the cooling water absorbs heat (related to the mass and flow of coolant), and the surface area of the chiller. @eric19312 is right that you want to avoid laminar flow as then heat is not efficiently distributed through the coolant and you get a smaller temperature gradient.

The law of heat conduction states that the rate of heat transfer through a material is proportional to the negative gradient in the temperature and to the area, at right angles to that gradient, through which the heat flows:

https://wikimedia.org/api/rest_v1/media/math/render/svg/2a39e44fe4fc81b72c154fc844c6ba9935c32bad
This equation doesn’t care how you define your x and y axes, so it doesn’t matter what direction you orient your chiller.

There may be other reasons for having wort in at the top and water at the bottom (e.g. gravity draining wort without a pump and relying on water pressure for cooling flow) but heat transfer is not one of the reasons.

 

[Tom R]

All interesting info, thanks.

I've been having the wort enter at the bottom of the coil, mostly for draining issues as mentioned above. Looks like I'll keep it that way.

 

[RufusBrewer]

Wort draining out the bottom is probably the method to give you the best overall results.

If you can, use clear or semi opaque tubing between the kettle and the CFC. Try to eliminate any air bubblesin that part of the tube.

If you are not using a pump, if you can, submerge the wort exhaust end in collected cooled wort. This will establish a siphon and aid in "pulling" wort through the CFC.

 

[Vale71]

There may be other reasons for having wort in at the top and water at the bottom (e.g. gravity draining wort without a pump and relying on water pressure for cooling flow) but heat transfer is not one of the reasons.

From a hydraulics standpoint that doesn't matter one bit either. All that matters when draining by gravity is the height differential between the liquid surface in the draining vessel and the liquid surface in the receiving vessel.