Cooling (or heating) using convection. For example, this principle can be used to cool/heat equipment or the air within a closed (instrumentation) cabinet. The coolers are easily installed by making a hole in the housing.
Cooling (or heating) of a liquid or gas using conduction. The heat is generally absorbed by a liquid and dispersed to the surrounding air by the heat sink. For the best heat transfer turbulators are installed in the liquid channels.