Chilled water system pdf

Mechanical engineers who design chilled water plants are the target audience for the guide. All of the material in the guide is relevant to this group, although experienced engineers can briefly review Chapter on loads and Chapter on equipment and then refer to this material as necessary. System designers may get the most use from this manual by familiarizing themselves with chilled-water-system basics and understanding the benefits of various options.

Thereafter, when a specific job will benefit from these advantages, consult appropriate sections of the manual in detail. A chilled water system is a cooling system in which chilled water is circulated throughout the building or through cooling coils in an HVAC system in order to provide space cooling. Systems that employ water chillers are commonly called chilled-water systems.

When designing a chilled-wat er system , one of the first issues that must be addressed is to determine which type of water chiller to use. The 1-pipe system is poorly suited to chilled water distribution for several reasons. The water quantity used in chilled-water systems is usually considerably higher than that used for heating because the unit coils work on smaller temperature differentials in the cooling mode than in the heating mode. A chiller and pump are disabled when excess flow rate in the bypass line is high enough to still have excess flow after a primary pump is turned off.

A typical chiller uses the process of refrigeration to chill water in a chiller barrel. What type of system uses heat to create chilled water? How does a chilled water system work ? What are the Common applications of a chilled water system?

Do all closed chilled water systems need water treatment? The control valves and control systems on equipment served by the chilled water system must be capable of accurate low load control and close off across the building pump shutoff head. Use of a separate bridge interface system for unusual or special cooling loads is required. Primary-secondary system bypass sizing. as PDF File (. pdf ), Text File (.txt) or view presentation slides online.

The condenser side of a chilled water system can be either air-cooled or water -cooled. Air-cooled chillers must be located outdoors in order for the condenser to reject heat. The importance of pressurizing the air is that it determines the pressure that the chilled water must achieve before the expansion tank accepts volume. For example, the closed tank has a pressure of 14. As the chilled water pressure increases above 14.

Base Design: 4Tons 0. This level of in most systems. When the load on the coil is zero, the valve is returning “unused” chilled water at essentially supply temperature. Cold return water “unloads” the chillers, causing them to operate inefficiently. Chilled water systems comprise the majority of larger built-up applied commercial cooling systems.

Chilled water from this system shall not be used for any application where the temperature of the heat exchanger surface in contact with the chilled water exceeds degrees F. The building pump must be selected for the building system head and flow requirements. Peterson, PE, FASHRAE P2S Engineering, Inc.

The chilled water supply temperature must be cold enough to dehumidify the air, but not too cold that the chiller freezes. The typical chilled water temperatures are shown below. C If the chilled water system is a glycol mixture, then the lowest temperature may be different than what is shown above. In a heating system this occurs when the system is heated form its coldest fill temperature to operation temperature. In a chilled water system this expansion occurs when the system is shut down and the system temperature rises from operating to ambient.

Water -Cooled Chiller Characteristics The use of the cooling tower gives water -cooled systems an efficiency edge over air-cooled systems and RTUs. In addition, unlike RTUs, which circulate cool air through ducts, all chillers circulate chilled water to air-handler units, where fans push air across heat exchanger coils to deliver cooling. System enable Chilled water and condenser water pumps start BEFORE the chiller startup System disable Chilled water and condenser pumps run for a period of time AFTER chiller is disabled. One articleeven predicts the fidemisefl of primary-secondary systems.

While there is no question that the primary-only system has many ad-vantages, the primary-secondary system may still be preferable for some.