Inside
Insights
Chilled Beams:
Not your everyday weapon
against heat
Steve Tredinnick, PE, Vice President of Energy Services, Syska Hennessy Group
for increased cooling output. Active (aka
“ventilated”) chilled beams (ACBs) are the
same as passive but incorporate additional
conditioned ventilation air introduced
through high-velocity jets along the length
of the unit. ACBs act as an induction unit
(back to the future from the 1960s) to
actively induce room air through the coil
to be cooled.
There are many shapes and sizes of
both types of chilled beams, from rectilinear slots to 24-inch squares and rectangles. There are also varieties of both passive and active chilled beams that incorporate other elements – e.g,, lights, sprinklers, speakers, space occupancy sensors
and smoke detectors – in a multi-service
beam configuration. These can be surface-mounted, suspended or recessed in a lay-in ceiling. Common manufacturers are
Frenger, Dadanco, Trox, Krantz, Carrier
(ACB) and Halton.
Editor’s Note: “Inside Insights” is a
column designed to address ongoing issues
of interest to building owners, managers
and operating engineers who use district
energy services.
The last few installments of this column have focused on heating terminal units and useful temperature ranges. So to
be fair, in this edition we will discuss an
emerging cooling technology that for the
past 10 years or so has been receiving a
great deal of attention from designers and
consultants: chilled beams.
Although the name does create a
vision of a large, exposed structural member
filled with chilled water, in reality this is not
so, since these beams have no structural
value for supporting building elements.
Neither are they some sort of Star Trek energy
beam used by Captain Kirk and Scotty to
put the Romulans ‘on ice’; nor are they a
new-fangled drink (Jim Beam on the rocks!
Shaken, not stirred!).
So now that we know what they are
not, what exactly are chilled beams? Chilled
beams (CBs) are typically two-pipe cooling
terminal units (some are three- and four-pipe
configurations) that only provide sensible
cooling to the space. By “sensible” I mean
dry heat from lights, equipment, people,
the building envelope, etc., since chilled
beams do not directly remove latent heat
or dehumidify.
Chilled-beam technology should not
be confused with radiant cooling, although
there are some similarities. Chilled beams
rely mostly on convective and not radiant
heat transfer. The convective cooling
method ‘turns over’ the room air several
times more than with a standard overhead
air system.
Types of Chilled Beams
There are two major types of chilled
beams: passive and active. Passive (aka
“static”) chilled beams (PCBs) consist of a
finned coil in a housing that uses natural
convection for cooling and is mounted
below or flush with the ceiling. Warmer
room air at the ceiling (or in the ceiling
plenum) is induced into the unit by the
cold air falling from the unit. Hybrid units
also exist that incorporate a radiant panel
Where Did They Come From?
Although the first actual uses of chilled
beams were in Europe, they have similarities
with the old high-pressure perimeter induction air systems introduced by Carrier in
the late 1930s. With these, high-velocity
streams of cold air induced room air circulation. The colder, high-pressure air systems
enabled the air-handling units and ductwork
to be smaller.
It is believed that the first radiating
CBs were installed at the Volvo plant in
Gothenburg, Sweden, in the late 1960s.
In the early 1970s the Swedes used the
first CBs with primary supply-air features.
Those savvy Swedes – they are into everything! CBs have been a hot item for the
past 15 or so years in Europe and Australia
and are also becoming more frequently used
and investigated in the U.S. They offer
Courtesy Dadanco.
This illustration of an active chilled beam indicates both the primary air connection (front center) as well
as four-pipe water connections (right-hand side).
