Brochure

The Science of Air Separation
The air in a closed hydronic system is managed
by using one of two techniques. In the Air Control
method, the air cushion and system water actually
touch. During the fill and system pressurization step,
all excess air is vented and the required air is stored
in a compression tank where it acts as a cushion for
the expansion and contraction of the system water
volume. Changes in the system temperature and
pressure change the solubility of air in water. The air
separator constantly removes entrained air as the
system air solubility falls.
In the Air Elimination method, a flexible diaphragm,
or bladder, physically separates the system water
and the air cushion. The entire hydronic system,
piping, radiation and boiler of chiller is completely
purged of air during the initial fill and any free air
introduced later is separated in the air separator
and vented to atmosphere.
• Tank can be mounted on the floor.
• Air cushion and system water do not touch.
• Tank smaller than standard tank for a given system.
PUMP
AIR
SYSTEM LOAD
AIR CONTROL SYSTEM
WATER
Pressure
reducing valve
Compr
ession tank
BOILER
SYSTEM LOAD
AIR ELIMINATION SYSTEM
Pressure
reducing valve
High capacity
automatic air vent
(Vented to atmosphere)
SYSTEM LOAD
BLADDER
TANK
PUMP
BOILER
77
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The separation of air from water is described by Henry’s Law and Stokes’
Law. Henry’s Law describes the amount of air water can hold in solution
depending on the temperature and pressure. Higher pressure or lower
temperature water can absorb or hold more air in solution than water that
is warmer or at lower pressure. Even the narrow temperature range of
chilled water systems demonstrates the effect of temperature on solubility.
Air bubbles released from fresh tap water as it rises to room temperature
show how a small change in temperature will give off free air from solution.