District cooling means the centralized production and distribution of cooling energy. Chilled water is delivered via an underground insulated pipeline to office, industrial and residential buildings to cool the indoor air of the buildings within a district. Specially designed units in each building then use this water to lower the temperature of air passing through the building's air conditioning system.
The output of one cooling plant is enough to meet the cooling-energy demand of dozens of buildings. District cooling can be run on electricity or natural gas, and can use either regular water or seawater.
District cooling is measured in refrigeration ton which is equivalent to 12000 BTU's per hour
District cooling systems can replace any type of air conditioning system, but primarily compete with air-cooled reciprocating chiller systems serving large buildings which consume large amounts of electricity.

I made tutorial videos of three parts showing step by step design of 5000 TR DCP using REVIT MEP.