For a long time now, a compressor has been the usual means of achieving cooling, and is what is usually meant when referring to machine cooling. Compressor-powered chillers are very flexible for cooling a building. The cooling can either be supplied to the cooling coil in an air handling unit or to chilled beams in each room.
All chillers are based on a closed circuit filled with refrigerant, e.g. CFC/freons or ammonia-based fluids. When a compressor raises the pressure of the refrigerant medium, it heats and evaporates into a gas. When the medium then passes a heat exchanger/condenser, it cools and condenses and reverts to its liquid state. Next, when the fluid passes an expansion valve, the pressure falls rapidly, which then cools the refrigerant. The fluid then passes over yet another heat exchanger, called an evaporator. Inside this, the cold in the refrigerant is transferred to a cooling medium (water or air) which then finally directs the cooling to where it is needed.