Cold aisle is a layout design for server racks and other computing equipment in a data centre. Cold aisle data center design involves lining up server racks in alternating rows with cold air intakes facing one way and hot air exhausts facing the other. The rows composed of rack fronts are called cold aisles. See Data Centre Aisle Containment for more information.
An air conditioner's compressor contains a refrigerant. As it works, it sends this refrigerant through the system. As warm air blows across the coil that carries this refrigerant, the heat transfers to the refrigerant (cool always absorbs warm). A fan moves the cooled air through the ducting and out of vents that lead into the rooms of your house. The refrigerant returns to the compressor where the absorbed heat is moved outside. The refrigerant is then sent through the coil once again to continue the cycle.