In many large refrigeration and air conditioning installations, it is desirable to use a cooling coil installed some distance from each other. For refrigerant supply to these coils and all refrigerant lines leading to them from the Central refrigerating machines are very expensive. It is connected with the complex and careful design of pipelines to avoid the return of oil and refrigerant problems.
Systems of water cooling resolve these issues. The components of the primary cooling system are closely grouped in a small area; this keeps the design and installation costs to a minimum, thus avoiding the potential problems associated with extensive refrigerant. The evaporator is called the cooler is used for cooling water. Cooling water circulates in each of several heat exchanger, as shown here in the unit. In a sense, the chilled water acts as a secondary refrigerant system, but water does not change state. He remains liquid, throughout each of its heat transfer steps.
As shown, the typical water temperature at the inlet of the heat exchanger is about 44F.
Return water from these coils 54F, or about 10F warmer than in tap water. Water piping system is less costly to design and install than the refrigerant piping system. Water circulates do cooling is also much cheaper. Leakage problems occur less and is easier to detect and correct than they are on a similar system of cooling pipelines. The figure shown here can be repeated for each floor of the building. When the water temperature at coil below freezing point, antifreeze is added to the cooling solution. This solution is pumped each unit as needed.
The same idea can be used to power many small heat exchanger on each floor. The previous design supplied one or two large heat exchanger on each floor and a controlled temperature zone, with all-air systems. All water systems, as shown here, however, manages each zone with a small private air handler is called "fan-coil." Chilled water is supplied for each fan coil. Hmm, that feeds the system with water cooling for large air cleaning or a small fan coils can use the D-X or flooded design...
Refrigeration 
