The working principle of charge air coolers with full expanding compact system is high temperature
air flow through the fins, transfer the heat by convection to the outer wall of cooling tubes, the
tube wall transfer the heat to the inner wall, then the water in the tubes take away the heat by convection, to complete the heat transfer.
 Working principle |  Tube for charge air cooler |  Fin for charge air cooler |
http://www.vrcoolertech.com/cooler/charge-air-cooler/charge-air-cooler-for-gas-generator-set.html