ASHRAE Journal - October 2023 - 53

TECHNICAL FEATURE
FIGURE 1 Working principle of an active chilled beam.13
Primary Air Plenum
Primary Air
Nozzles
Secondary Air
Mixing Chamber
Supply Air
Occupied Zone
Heat Exchanger
signifi cant fraction of this energy use in buildings
comes from HVAC systems,4,8 as people spend up to
90% of their time indoors.9 The Global Carbon Capture
and Storage (CSS) Institute published projections
about the increasing need for cooling equipment in
Europe.10 Hence, sustainable space-cooling technologies
are desired. The IEA's future projections regarding
the growth of global electricity demand for
space cooling show similar stats, as shown in
Online Figure 1,11 which can be found with all online
fi gures at https: tinyurl.com/JournalExtras.
Chilled Beam Operation Principle
An important part of reducing global energy use
and environmental impact is reducing energy
consumption inside buildings. Chilled beam
systems have proven to be a trusted solution for heating,
ventilation and air conditioning since its beginning
in the 1980s. During the past two decades, the use of
active chilled beam (ACB) systems as promising airconditioning
systems has become increasingly prevalent
all over the world. However, studies on air distribution
of ACB systems are still inadequate. Chilled beam
systems are primarily used for cooling and ventilation
in spaces that appreciate good indoor environmental
quality and individual space control.
ACBs are connected to the ventilation ductwork,
with the high temperature of cold water between 14°C
and 18°C (57°F and 65°F) to avoid condensation on the
cooling coil12,13 and the low temperature of hot water
between 30°C and 45°C (86°F and 113°F). Processed air
from the AHU is forced into the set of nozzles as primary
air. The purpose of the nozzles is to provide high-speed
primary air and consequently create high dynamic
pressure and low static pressure to facilitate induction,
i.e., pressure differences between the mixing chamber
and room. The ductwork takes this outdoor air to the
primary air plenum. The secondary air passes through
the cooling coil.
The heat in the room is taken away by the chilled or
warm water inside the heat exchanger. The primary air
is mixed with the secondary air in the mixing chamber
and supplied into the occupied zone as a mixture called
supply air13,14 (Figure 1). ACBs usually require less ceiling
space (up to 0.3 m [1 ft]) and ductwork, classifying it into
distinct architecture for offi ce setups.15
Chilled beam can be classifi ed into ACB and passive
chilled beam (PCB), according to the air-conditioning
requirement (Figure 2).16 Due to the advantages of
providing noise control, thermal comfort and energy
effi ciency with less space requirements, ACBs have
been spreading and increasing in popularity in Asia,
North America and Europe.17 They are used widely
in hospitals, laboratories, schools and commercial
FIGURE 2 Chilled beam.16
4
2
1
5
6
3
1. Primary Air (Dehumidifi ed Outdoor Air).
2. Primary Air is Supplied Through Nozzles.
3. Primary Air Supply Induces Room Air
To be Recirculated Through the Heat
Exchanger of the Chilled Beam.
4. Recirculated Room Air and the Primary
Air are Mixed Prior to Diffusion in the
Space.
5. Cold Water Connection.
6. Warm Water Connection.
buildings.18 Most people spend their time in artifi cial
environments, so the possibility of sick building
syndrome and human disease increased; both of them
are making people suffer as a result of poor indoor air
quality and thermal environments.19
Kosonen, et al.,20 have performed experiments
including 24 occupants existing at a simulated offi ce
using four different cooling systems (Figure 3, from
right): (A) mounted local radiant cooling panels with
mixing ventilation, (B) chilled beam with radiant panel,
(C) chilled beam and (D) radiant ceiling. The results
show there is no big difference for thermal conditions
between radiant and convective systems, and those
conditions are accepted for all body thermal sensation in
all cooling systems.
Kosonen, et al.,21 discussed the effect of thermal load
and airfl ow distribution of chilled beams in a test room.
Experimental results showed there is an increase in
the maximum velocity with increasing the heat load and
so on. Thermal load location did not have a signifi cant
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ASHRAE Journal - October 2023

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