DJ_L3ThAL said:
e. Its goverened by the rules/fundamentals of thermodynamics.
Moad's isn't... EDIT: I should also say that IC's and plate chillers are too..
Shell and tube are the most popular, which are generally counter - flow, but a very different physical beast to the CFC's for brewing. They are popular because they are easy to fabricate, can be inspected easily and can be built to take high pressure.
"the rules of thermodynamics" mean that you still have a certain volume /mass of high energy liquid (delicious wort) that needs to follow the second law and give its precious energy to something cooler. The first law says that you will need more than 1:1 cool water:wort unless you are only chilling from 30°C.
The zeroeth law says that if you don't have any flow and just let it sit there in the plate chiller it will all balance out at some point. But since we are not at steady state, we need some differential temps, some flow and some surface area.
The surface area (ignoring turbulence) of a plate chiller will give you more power than a small length of copper tube. This means that for the same flow/fluid properties you will get your wort closer to your cooling water temp. Or, for the same target temperature, you can slightly reduce your flow RATE. You may use less water, but it means your cooling water just gets hotter - no first law breaking allowed.
Or, you know, whatever. If you have a special CFC I'd love to get one...