Water Systems

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1-Types Of Water systems:

Water systems that are part of an air conditioning system and that link the central plant,chiller / boiler, air-handling units (AHUs), and terminals may be classified into the following categories according to their use as the following:

1.1-Chilled Water System:

In a chilled water system, water is first cooled in the water chiller—the evaporatorof a reciprocating, screw, or centrifugal refrigeration system located in a centralized plant—to a temperature of 40 to 50°F (4.4 to 10.0°C).

It is then pumped to the water cooling coils in AHUs and
terminals in which air is cooled and dehumidified. After flowing through the coils, the chilled water increases in temperature up to 60 to 65°F (15.6 to 18.3°C) and then returns to the chiller.

Chilled water is widely used as a cooling medium in central hydronic air conditioning systems. When the operating temperature is below 38°F (3.3°C), inhibited glycols, such as ethylene glycol or
propylene glycol, may be added to water to create an aqueous solution with a lower freezing point.

1.2-Evaporative-Cooled Water System:

In arid southwestern parts of the United States, evaporative cooled
water is often produced by an evaporative cooler to cool the air.

1.3-Hot Water Systems:

These systems use hot water at temperatures between 450 and 150°F (232
and 66°C) for space and process heating purposes.

1.4-Dual-Temperature Water System:

In a dual-temperature water system, chilled water or hot water
is supplied to the coils in AHUs and terminals and is returned to the water chiller or boiler mainly through the following two distribution systems:

- Use supply and return main and branch pipes separately.
- Use the common supply and return mains, branch pipe, and coil for hot and chilled water supply and return.

The changeover from chilled water to hot water and vice versa in a building or a system depends mainly on the space requirements and the temperature of outdoor air. Hot water is often produced by a boiler; sometimes it comes from a heat recovery system.

1.5-Condenser Water System:

In a condenser water or cooling water system, the latent heat of condensation is removed from the refrigerant in the condenser by the condenser water.

This condenser water either is from the cooling tower or is surface water taken from a lake, river, sea, or well. For an absorption refrigeration system, heat is also removed from the solution by cooling water in the absorber.

The temperature of the condenser water depends mainly on the local climate.

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