Heat exchangers are systems that are used for the transfer of thermal energy from one flowing substance to another. The system is often used for a confined heated liquid to pass though a cool liquid. The heat naturally gravitates to the cooler liquid causing the exchange in temperature. The car radiator is a familiar example of this principal. Water that has passed though the engine becomes hot but also keeps the engine cool. As it passes through the reservoir of the radiator, the heat is transferred out of the flow. It then returns to the engine much cooler and able to maintain a safe operating temperature.
This same principle is used in heat exchangers for both industrial and residential radiant heating and cooling applications, reclaiming a heat stream from manufacturing, or waste decomposition. Geothermal systems also use this principle by circulating a liquid or gas through a pipe deep below ground where the temperatures remain constant year round. Where the pipe emerges from ground they pass through a device and exchange thermal energy with the atmosphere. Another system will take air from a normally warmer room and transfer the heat to a colder room.
Some residential applications include heating such as solar and central along with geothermal. Other examples are floor heating, ice melting, pool heating and household hot water. Industrial applications may be waste-water and landfill heat recovery, oil and boiler coolers, refrigeration condensers and evaporators, and chilled water systems.
Thermal energy can be harnessed and transferred to where it is needed from virtually anywhere by utilizing this basic principal. It is not only environmentally beneficial, but economically as well.