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.
Cooling or heating using conduction. Objects attached to the cold plate of the cooler are cooled directly by the assembly. The heat will be dispersed by the liquid. With a circulating circuit the heat can be dispersed to the environment by using a heat exchanger. The hot side can also be cooled directly by tap water (open circuit).