Trane SYS-APM001-EN manual Primary System Components, Chiller

For more details on the basic operation and components of a chilled-water system, consult another Trane publication, Chilled-Water Systems, part of the Air Conditioning Clinic Systems Series (TRG-TRC016-EN).

Primary System Components

Chilled-water systems consist of these functional parts:

•Chillers that cool the water or fluid

•Loads, often satisfied by coils, that transfer heat from air to water

•Chilled-water distribution pumps and pipes that send chilled water to the loads

•Condenser-water pumps, pipes, and cooling towers or condenser fans that reject heat from the chiller to ambient air

•Controls that coordinate the operation of the mechanical components together as a system

In most cases, the chiller’s purpose is to make water colder. Some chillers cool a mixture of water and other chemicals, most commonly added to prevent freezing in low-temperature applications. Other additives may be used to modify the properties of the fluid, thereby making it more suitable for its intended application. For the purposes of this manual, the term water can be understood to be any such acceptable fluid, with recognition of the diverse applications in which chillers are used.

The chiller rejects the heat extracted from the chilled water, plus the heat of compression (in the vapor-compression cycle), or the heat of absorption (in the case of an absorption chiller) to either the ambient air (air-cooled) or to another circuit of water (water-cooled). If the compressor-motor is refrigerant cooled, the chiller also rejects heat generated by motor inefficiency. Air-cooled condensers use fans to facilitate cooling by the ambient air. Water-cooled condensers typically use an evaporative cooling tower.

After the water has been chilled, it is distributed via pumps, pipes, and valves (the distribution system) to the loads, where a heat exchanger—for example, a cooling coil in an air-handler—transfers heat from the air to the chilled water, which is returned to the chiller.

Each component of the chilled-water system is explained in more detail in the following sections.

Specific application considerations for absorption chillers are addressed in another Trane publication, Absorption Chiller System Design (SYS-AM-13).

Chiller

There are a variety of water chiller types. Most commonly, they are absorption, centrifugal, helical rotary, and scroll. Some reciprocating chillers are also available. Chillers can be either air- or water-cooled. Major vapor-compression chiller components include an evaporator, compressor(s), condenser, and expansion device(s) (Figure 1). This manual discusses the chiller’s evaporator and condenser and their relationship to the chilled-water system.

SYS-APM001-EN Chiller System Design and Control 1