Check out this introduction to heat exchangers made by the American Petroleum Institute.  This is a good basic primer to understand how heat exchangers work in an industrial plant.  Ameritube produces copper alloys heat exchanger tube in C70600, C71500, C12200, C44300, Monel and other alloys.  Ameritube also distributes duplex, super duplex, stainless and carbon steel for these same applications, including nickel alloys such as Monel 400, Nickel 200, and C-276.  Below you can find additional heat exchanger pictures where Ameritube tubing was installed.