Radiators: they are found in old houses and considered to be charming, they are the bane of small children who do not believe mommy when she says "don't touch that, it's hot" and they are able to keep a home toasty all winter long. Radiators are one of the most common forms of water to air heat exchangers around. These heat exchangers are not only found in residential and commercial settings but also designed for automotive vehicles of various shapes and sizes as well as being apart of some electronic systems. The old-fashioned but still present radiators used to heat a space are able to do so by way of a boiler that heats up water and then circulates it through the radiators in individual rooms to heat the air in each one. Central heating radiators are often made from cast iron or copper, both of which hold onto the heat and cast it into the room well. Aesthetically, radiators are now a trend and there are therefore many size, styles and colors to choose from. The system radiators employ is actually steeped in Ancient Roman central heating techniques. Utilizing heated water underneath their floor boards to warm up public baths and buildings as well as private homes, they called their system a hypocaust. So water to air heat exchangers, which can also now function in air to water heat exchanges too, are one of the oldest heating systems around. This same sort of process is also utilized to a smaller extent within refrigerators and the hot water heaters that supply bath, shower and sink water. Outside of a residential context, various styles of water to air heat exchangers are used in the aerospace industry as well as marine, pharmaceutical, medical, oil and gas and photonic industries. Source: heatexchangers.org
Source:
http://www.heatexchangers.org/2011/10/20/water-to-air-heat-exchanger/