Counterflow cooler - lesson learnt

[Andy]

Recently I added a valve to the ouput end of my CFC to restrict the cooling water output, previously I had a valve on the input end and controlled the water flow through that. I had noticed that at the output end the water jacket wasn't fully enclosing the inner copper pipe, there were large air pockets. The output end valve was added to try and remove these air pockets by making the water build up at that point.

Using the new output end I can remove the air pockets by closing the valve for a couple of seconds and then opening it - the sudden release of the water pressure build up forces air out of the cooling jacket, great! BUT I found that I get much more efficient cooling if the output valve is then left wide open and control the flow via the input side valve. I'm not going to ponder on the thermodynamics of why this is this is the case but thought I'd pass my experience on to others with a valve on the output end of their CFC.

When I mean more efficient I mean *really* more efficient - I'd wondered why my previous brew (the first using the output end valve) used about twice the amount of cooling water as earlier (input end valve only) brews. Now I know

[BlightyBrewer]

I have both input and output valves on my cfc, but my garden hose in not clear so cannot see through. I tend to use both valves (don't know why)...

Thanks for the heads up andy - very useful info to know.

[jasonaustin]

Turbulence.
Similar to a fan. Air on the intake side is relatively smooth, whereas the output is turbulent.
Controlling CFC output causes water to flow in smooth, orderly manner within CFC.
Controlling CFC input causes turbulence within the CFC.
I would never have imagined it would cause any measurable difference though; interesting that you have. I only have a valve on output (for same reason as you - to ensure hose is filled properly). May add one to input now, as I'm always interested in reducing water usage.

[Andy]

Amen - I'm on a water meter and hate wasting water (I would even if I weren't on a meter...)

My last water bill was £40 and that's for a six month period