Chilled Water Systems
Cooling loads are often
highly variable. In order to track changes in cooling load,
chilled water systems must respond by varying chilled water
flow rate, chilled water temperature differential, or both.
Typical chilled water system design practice is based on
either a constant flow/variable temperature difference or
variable flow/constant temperature difference concept. These
are called respectively, constant volume and variable volume
systems.
Systems can also be classified according to the levels of
pumping present. Systems with a single level of chilled
water circulation pumps are called primary-only systems
and those with both circulating pumps for chillers and distribution
pumps are called primary-secondary systems. Some systems
may have load circulators as well, which are sometimes called
tertiary pumps.
In this section, a description of common chilled water system
types from the most basic comprehensive constant flow to
all variable flow systems is provided. For purposes of discussion,
chilled water pumping systems are divided into three categories
