For an air heat exchanger where one of the components is air or some other gas, the air side heat transfer coefficient will be much lower, so additional heat transfer surface area, this is where fin tube exchangers are typically used.
A finned tube heat exchanger will typically have tubes with fins attached to the outside of them and there will usually be a liquid flowing through the inside of the tubes and air or some other gas flowing outside of the tubes, where the additional heat transfer surface area due to the finned tube, increases the heat transfer rate.
An air heat exchanger like the condenser in an air conditioning unit is typically a fin tube exchanger. Another common fin tube air heat exchanger is the car radiator. The purpose of the car radiator is to cool the hot water in the tubes with the air passing through the Heat Exchanger.
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