Building services engineering/Chilled water systems

Referring to Wikipedia's definition of chilled water, chilled water systems comprise network that at it's simplest provides methods to reject heat from demand-side systems (e.g. air handling units, fan coil units, etc.) through water to ambient conditions. The different components of a chilled water system can be broken down as follows:

Most often referred to as a chiller, this piece of machinery utilizes either compressors or types of high-energy reservoirs to induce a refrigeration cycle. This refrigeration cycle is responsible for accepting heat from high temperature (return water) water and rejecting it somehow to atmosphere. The heat rejection of a chiller may be done directly through the air, via machines known as air-cooled chiller, or it may be through the rejection of heat via cooling tower, known as condenser water cooled chillers.

In order to deliver chilled water to the desired end-source, a network or series of pipes are required to transport the medium from generation to point of consumption. Along the way, pipes will diverge, converge, and contain any number of appurtenances for control and balancing of the system. Every length of pipe and every device on the water-side of the system incurs pressure losses. The sum of these pressure losses at any given moment of operation is known as total dynamic heat (TDH), and the pump is the component responsible for inputting the work energy necessary to supply the water at the desired flow rate and pressure.

The design and planning of a chilled water system involves the application and study of:

• fluid mechanics
• control systems
• building energy modeling
• heat and mass transfer

Each of these disciplines can be used to break down the problem of providing chilled water, at the appropriate temperature, pressure, time and location at optimum costs, and minimum energy consumption.

• w: Chilled water