Hello to you all. First time brewer here.
I have a little experiment
Instead of using Cooper pipe I thought using small car cabin heater. Mine is old and dirty but it is just to prove the theory.
Dimensions are 17x17.2.5 cm with two 16mm connections
Surface area is exactly the same as surface of copper pipe 8m long 14mm in diameter.
Water: 10L at 100C
Water was running medium speed through cooler/radiator
Temperature of water 20C
From 100 to 20C in 13min
You have diagram in pictures.
This is and old car cooler only for this test. There is a new one from the box waiting for your opinions.
There are models twice in size that I believe could cold much more wort in same time.
There is also option for placing one like this in bucket of ice before the main in the wort.