It is the most important type of air conditioning, in which the air is cooled and generally dehumidified. The schematic arrangement of atypical summer air conditioning system is shown by figure........

source

How it does work;

source

The outside air flows through the damper, and mixes up with recirculated air (which is obtained from the conditioned space). The mixed air passes through a filter to remove dirt, dust and other impurities. The air now passes through a cooling coil. The coil has a temperature much below the required dry bulb temperature of the air in the conditioned space. The cooled air passes through a perforated membrane and looses its moisture in the condensed from which is collected in a sump. After that, the air is made to pass through a heating coil which heats up the air slightly. This is done to bring the air to the designed dry bulb temperature and relative humidity.

Now the conditioned air is supplied to the conditioned space by a fan. From the conditioned space a part of the used air is exhausted to the atmosphere by the exhaust fan or ventilators. The remaining part of the used air(known as recirculated air) is again conditioned. The outside air is sucked and made to mix with the recirculated air in order to make up for the loss of conditioned air through exhaust fans or ventilation from the conditioned space.