Low energy consumption hvac systems for green buildings using chilled beam technology

International Journal of Advanced Research in Engineering and Technology (IJARET), ISSN
0976 – 6480(Print), ISSN 0976 – 6499(Online) Volume 4, Issue 3, April (2013), © IAEME
316
LOW ENERGY CONSUMPTION HVAC SYSTEMS FOR GREEN
BUILDINGS USING CHILLED BEAM TECHNOLOGY
Syed Moazzam Ali
Technical Director,
Taiba Engineering Consultants
Dr.Balu Naik Banoth
Professor JNTUH
ABSTRACT:
The movement toward sustainable building designs is being driven largely by
environmentally-sensitive building owners and/or their prospective tenants. There are also heightened
concerns about assuring a proper indoor environment at all times and conditions for the building
occupants. In addition to providing temperature control, a fully effective HVAC system must also
address many other indoor environmental issues that affect occupant comfort, productivity and health
such as ventilation air, air distribution, humidity control, noise levels, etc.
As these owners and their consultants weigh their HVAC system alternatives, they often find
that chilled beam systems are the ideal "green" solution for many buildings. There is also a persuasive
overall comfort and economic argument for the use of active chilled beam systems over other of the
more conventional systems choices. While relatively new in India, chilled beam systems are proven
and are successfully being used in Europe since a decade.
The chilled beam system promotes excellent thermal comfort, energy conservation and efficient use
of space due to the high heat capacity of water used as heat transfer medium. It is an energy efficient
HVAC technology which works on dry cooling principle.
Chilled beams system would be examined which would show energy conservation and has
potential to save 30-40% HVAC energy consumption to a conventional Air conditioned Building
case. The simulation results would be encouraging, and they would confirm the advantage of the
application of these Chilled beams system cooling strategies.
1.0 INTRODUCTION
Chilled beam systems are used mostly in the nonresidential buildings. These are commercial
buildings, offices, hotels, banks, universities, schools and hospitals. Typical applications are cellular
and open plans offices, hotel rooms, hospital wards, retail shops, bank halls etc
Chilled beam systems are primarily used for cooling, heating and ventilating spaces, where
good indoor environmental quality and individual space control are appreciated. These systems are
INTERNATIONAL JOURNAL OF ADVANCED RESEARCH IN
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ISSN 0976 - 6480 (Print)
ISSN 0976 - 6499 (Online)
Volume 4, Issue 3, April 2013, pp. 316-324
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317
dedicated outdoor air systems meant to be applied primarily in spaces where internal humidity loads
are moderate.
2.0 OVERVIEW OF CHILLED BEAMS
“A cooled element or cooling coil situated in, above or under a ceiling which cools
convectively using natural or induced air flows. The cooling medium is usually water.”
There are two basic types of chilled beams: active and passive.
2.1 Active chilled beams (ACB) uses a pre-cooled (and dehumidified) primary air using chilled water
in a quantity needed to meet the room latent load and ensure good air quality for the occupied area.
The cooled and dehumidified primary air absorbs the space latent load; ensuring the chilled beam coil
operating without condensation. The chilled beam then cools or heats the induced air to meet the room
sensible load and react to the room thermostat requirements.
Active chilled beams operate using the induction process. During induction, the primary air
discharges under pressure through nozzles located within the device. This high velocity incoming
primary air creates a negative pressure in the inlet portion of the beam thereby inducing room air
through the beam coil where it mixes with the cold primary air. This mixed air is then discharged
through the outlet slot of the beam into the room, resulting in a total airflow quantity 3 to 4 times
greater than the primary airflow. We refer to this ratio of total air to primary air as the induction ratio.
“A convector with integrated air supply where primary air, induced air or primary air plus
induced air passing through the cooling coils. The cooling medium in the coil is water.”
2.2 Passive chilled beams (PCB) work using natural convection. Air cooled by the coil inside the
beam becomes denser than the surrounding room air and therefore flows downward into the room.
The difference in density combined with the height of the beam induces room air down through the
beam coil. Thus passive beams mainly provide a downward airflow in the room. This downward flow
induces air from the room upward to the ceiling level and then through the beam coil. Unlike an active
chilled beam, the passive chilled beam delivers treated primary ventilation air directly to the space
and not through the chilled beam. Nevertheless, like the active chilled beam, this ventilation air must
be sufficiently dehumidified to meet the entire latent room load. To avoid drafts in spaces with low
ceilings do not locate passive beams above workstations with sedentary occupants. Both remixing and
displacement terminal devices provide good comfort in the room in combination with passive beams.
“The cooled element or cooling coil fixed in, above or under a ceiling fitted with a cooling
coil mainly convectively using natural airflows. The cooling medium is usually water” Chilled Beams
offer a quiet indoor air free from draught. In a typical Chilled beam, the air is cooled by means of
supplying chilled water and the supply of air flow rate is dimensioned to meet the indoor air quality
requirements.
2.3 Advantages of chilled beam systems over conventional designs
Chilled beam systems are suitable for use in high sensible cooling load applications or where
individual temperature control is required. Compared with a system where the cooling duty is
supplied entirely by air (all-air systems), a chilled beam system reduces the fan power requirements
and space needed for air- handling plant equipment and ducting.
TABLE - 1
S.No SYSTEM Energy Noise Output (w/m²)
1 FCU (Fan Coil Unit) Medium / High Medium 100-200
2 VAV (Variable Air Volume) Low/Medium Low/Medium 100-200
3 VRF (Variable Refrigerant Volume) Medium / High Medium 150-200
4 Chilled Beam Low Low 100-300

318
2.4 Chilled beam systems have the following advantages:
Fan Energy Savings: In general the design intent is for the central system to circulate only the
amount of air needed for ventilation and latent load purposes, with the active chilled beams providing
the additional air movement and sensible cooling and/or heating required through the induced room
air and secondary water coil. In this manner the amount of primary air circulated by the central system
is dramatically reduced (often 60-70% less than conventional "all air" systems).
Essentially active chilled beams transfer a large portion of the cooling and heating loads from the less
efficient air distribution system (fans and ductwork) to the more efficient water distribution system
(pumps and piping).
The net result of this shift in loads with active chilled beam systems is lower energy
consumption and operating costs. Fans are the largest consumer of energy in most commercial
buildings. With active chilled beam systems the fan energy is dramatically reduced due to the
relatively small amount and low pressure of the primary air being circulated by the central system.
Chiller Energy Savings: While the size of the chiller in an active chilled beam system would
normally be the same as that needed in a conventional "all air" system, its effective hours of operation
(or loading) could be significantly less if the system employs a water-side economizer to serve the
Active Chilled Beams. This is due to the relatively warmer secondary water temperatures (typically
56 — 58 °F) used by the Active Chilled Beams which allows the cooling load to be satisfied for more
hours using the water-side economizer.
Also, if separate chillers are serving the central air handlers and the active chilled beams, the
COP of the chiller serving the Active Chilled Beams would also be much higher due to the relatively
warmer water temperatures used by the Active Chilled Beams.
Heating Energy Savings: As the Active Chilled Beams normally provide sufficient heating
capacities at relatively moderate hot water temperatures (110 – 130 °F) there is also an opportunity to
maximize the efficiency of condensing boilers through the relatively low water temperatures being
returned to the boilers. With the relatively low water temperatures required, using geothermal heat
pumps to satisfy the heating loads is also practical.
Excellent Indoor Air Quality and Odour Control
The full ventilation air requirements are delivered to the zones at all times and at all load
conditions.
Superior Humidity Control: Humidity control at all sensible load conditions are also assured as the
constant volume primary air is delivered with the proper moisture content to satisfy the latent loads.
Excellent Air Movement and Uniform Air Temperatures: Improved comfort through excellent air
movement and uniform air temperatures throughout the room, with little concern about potential
drafts and dumping at part load conditions. As the airflow and resulting air movement is constant at
all load conditions and the induced room air is typically 3-4 times the amount of primary air, the
temperature of the mixed air being continuously discharged into the room is generally more moderate
than with conventional systems.
Other factors positively affecting the overall building costs when using active chilled beam
systems include:
There are no electrical line power connections to the active chilled beams which can
significantly reduce electrical wiring installation costs. In some cases this can result in reducing the
overall electrical infrastructure in the building due to greatly reduced fan power requirements.

319
Very Low Noise Levels
a) Decouples ventilation load from room sensible + latent loads resulting in better temperature
control and fan energy savings.
b) Typical supply air temperature is 64-66 °F exiting the chilled beam maximizing occupant
comfort. Conventional systems deliver cold air at 55 °F with the potential of creating drafts if
poor mixing occurs
c) Reduced plenum space required (units are ~12” tall), good for retrofit applications
d) Some units incorporate fluorescent lighting fixtures and fire sprinkler heads.
e) Some units offer directional air flow pattern control, optimizing comfort and preventing drafts
f) Water moves energy through the building and is much more effective than air approximately
600 x heat transfer capacity (6o
F vs 20o
F ∆T), But Still little quantity of ventilation air is
needed.
g) Chilled beams provide benefits in life cycle costs: Low maintenance cost, Good energy
efficiency.
h) Free cooling possible in cold and temperate climate
i) Chilled beams system is a hygienic system
j) No filters to be changed or cleaning of drain pans for condensate
k) Easy cleaning of coils and surfaces, only once in every 5 years
l) Chilled beams operate with a dry cooling coil
m) No condensate collection system
n) Primary air should be dehumidified in the air handling unit
2.5 Increased energy efficiency:
Water-based systems transfer energy more efficiently than air-based systems. By
transferring the heating and/or cooling load to water based system, energy requirements and
operational costs may be significantly reduced.
Reduced mechanical footprint: Water distribution systems are a fraction of the size of air
distribution systems, reducing the ceiling space needed for the HVAC system and increasing available
floor space.
Lower maintenance costs: These systems are simple and efficient, with Low maintenance costs.
Increased thermal comfort: These systems are very quiet and require significantly reduced air
volumes, leading to a reduced risk of drafts.
Improved indoor air quality: These systems do not require air to be recirculated throughout the
building to achieve heating or cooling, and are typically coupled with 100% outside air systems
Low energy consumption (passive beams in particular)
Superior Comfort & Performance (passive beams in particular)
Quiet, draft-free and thermally stable environment
Part-radiation, part-convection heat transfer is more comfortable than all convection air system
Self-adaptable output, Resistant to tampering and de-commissioning
Health
Once-through, no-recycling air system, No ‘sick-building-syndrome’, Humidity control
Building design efficiency
Small plant rooms and risers, Small ceiling space
When the active chilled beams are sized at the typical inlet static pressures of 0.5" w.c. or less, very
low noise levels are achieved as the new technology nozzles are whisper quiet and there is no terminal
unit fan or motor in or near the occupied spaces.

320
Chilled Beam system typical Design considerations for the chilled water and primary air
a) Assume spaces with normal ceiling heights (9-10 ft), apply chilled beams in with cooling
loads of 25-30 Btu/ft² of floor area. This capacity limitation is primarily due to the maximum
possible air velocity in the space. Cooling Capacity to avoid draughts in the occupied zone:
Active chilled beams is typically 250 W/m (max 350 w/m), Passive chilled beams is 150 W/m
(max250w/m), Cooling demand in the space typically less than 80W/floor-Sq.m (Max 120
W/floor-Sq.m) and Heating demand less than 40 W/floor-m2.
b) Chilled beams uses warmer chilled water from the secondary side of the cooling plant (or
from mixing of primary and secondary water) at an inlet temperature from 57-61 °F to
prevent condensation from occurring on the beam coil. This equates to a primary supply air
temperature of approximately 65 °F.
c) Special humidity (condensation) sensors should be installed on the chilled beam coil that
close the water control valve if the RH gets to 90% on the incoming chilled water pipe.
Alternatively, use an atmospheric RH sensor in combination with an air temperature sensor to
reset the supply water temperature upward closer to 60 °F during conditions when
condensation might occur.
d) It is important for the DOAS system to adequately dehumidify the primary ventilation air
such that it can absorb all of the latent loads in the zone. The DOAS leaving air temperature
(LAT) should be in the 44-55 °F dry bulb range with approximately 44-45 °F dew point (DP)
to ensure there is no condensation on the beam coil. The lower end of the ranges should be
used when the zone latent loads are higher, such as conference rooms, school classrooms, etc.
while the higher end of the range may be used in applications with low zone latent loads.
e) Chilled beams offer a simple design process with superior final efficiency. Designing with
chilled beams is very similar to conventional system design. Chilled beams available in the
U.S. generally have a 3:1 induction (room air to ventilation, or primary, air) ratio, are capable
of 100 to 200 CFM of primary air per 6 ft of beam, and provide from 4,000 Btuh to 8,000
Btuh of sensible cooling per 6 ft of beam. Airflow, cooling, and sound performance vary
considerably by manufacturer.
f) Chilled beams should be installed and placed correctly in the space. In general the Chilled
Beam Width ranges from 0.3m to 0.6m, and lengths range from 0.6m to 3.0m.
g) Active Chilled Beams recirculate room air through a unit-mounted coil, driven by ventilation
air (primary air) with mixing ratios as high as 6:1 (discharge air to primary air). They have
relatively shallow depth with clearance requirements generally less than 0.3m.
Figure 1 – Positioning of Chilled Beams
2.7 Problems with Chilled Beam Air Conditioning
Active chilled beams should not be considered a silver bullet in terms of addressing high
sensible cooling requirements in all spaces. Certain spaces are well suited to chilled beam use, and
others are not appropriate for this technology.

321
Areas that may not be suitable for active chilled beams may include, but are not limited to:
Large vestibules/atriums, latent load is difficult to control and could be addressed via other design
strategies, High latent cooling requirements: kitchens, pools, locker •rooms, spas, gymnasiums, etc.
Cost: Slightly higher than conventional VAV system, mainly due to novelty factor
Limited experience: Risk factor and potential litigations
Vested interests: Contractors protecting investment in sheet metal shops, Consultants not rewarded
for additional engineering and development.
Technical: Duct leakage: unsuitable technologies cannot air-condition glasshouse with chilled beams:
need efficient building envelopes, Noise from valves, Creative energy absorbed in energy modelling
and ticking off rating system charts.
3.0 Design procedure:
Selection of thermal environment load: Room air temperature (summer/winter)
Selection of the indoor air quality level and air flow rate: Fresh air flow temperature, Infiltration
through walls –pressure, temperature, Relative humidity in the space, Primary air cooling coil
temperature, Humidity balance
Calculation of required cooling and heating capacity: Heat loads, Heat losses, Comfort conditions,
cooling effect of primary air
Adjustment of building design parameters: Decrease electrical load losses by better solar shading
and improved window type
Selection of chilled beam type: Active beam (exposed/integrated), Passive beam
Selection of inlet water temperature: Temperature climate, Location of the building
Selection of water temperature and air water flow rate: Temperature difference, Water flow rate
Selection of water temperature and air water flow rate: Specific cooling capacity of beam,
Specific primary air flow rate
Noise level and system pressure loss calculation: Selection of room controls, Rom air temperature
is controlled by modeling water flow rate, two port valves, and Air flow rate
Air and water distribution system: Dehumidification of AHU, 3 port mixing valves in cooling pipe
to keep the inlet water temperature in design value, Free cooling equipment’s in chiller
3.1 Duct Design and Working Static Pressures
It is generally preferable to consider a low-velocity downstream ducting strategy. The main
ducts may be sized as they would normally for offices at 1,200 fpm to 2,400 fpm (6 m/s to 12 m/s).
Active chilled beam projects often are installed using round spiral downstream ducting. A good rule
of thumb would be to restrict the branch ducting to less than 600 fpm (3 m/s).
Typical operating static pressures range from 0.3 in. w.c. to 1.2 in. w.c. (75 Pa to 300 Pa) at
the pressurization plenum of the beam.
At 1 in. w.c. (250 Pa), the acoustic signature of a single active chilled beam in a typical room
could be as low as 29.5 Dba. Supercharging beam applications by considering working static
pressures between 0.75 in. w.c. to 1 in. w.c. (185 Pa to 250 Pa) is fundamentally a sound approach
from an optimization perspective in terms of first costs
3.2 Beam Placement and Room Air Distribution
Average room air velocity is 30 fpm [0.15m/s]. Air discharge temperature from ACBs range
between 64°F to 66°F (18°C to 19°C).
3.3 Installation
Operating weight is approximately 15 lb/ft (6.8 kg/m) for 2 ft (600 mm) wide, double
deflection units. Hanging a beam from the structure is through four adjustable hanging brackets that
can be fastened to the concrete under floor via threaded rod or aircraft cable.

322
3.4 Water-Side Control
Chilled water temperatures for ACB loops range between 55°F to 61°F (12.7°C to 16.1°C)
although the space design conditions and the minimum ventilation rates dictate that the beams receive
59°F to 61°F (15°C to 16.1°C) The separation between the secondary chilled water supply
temperature, and both the dew point of the primary air and dew-point design of the space, is the
technique used to prevent condensation on the beam-mounted cooling coil
3.5 Air-Side Control
Discharge air from the DOAS is used to dehumidify the space. It is often quite common to
service the makeup air unit with 45°F (7.2°C) chilled water. As such, 51°F to 52°F (10.6°C to 11.1°C)
dew-point temperatures supplied to the occupied zone are relatively easy to achieve in many areas of
the country by slightly oversizing the evaporator coils. Coil face velocities less than 400 fpm (2 m/s)
increases the coil residence time and lowers the overall fan static pressure to further decrease system
operating costs. Duct discharge temperature of 54°F to 55°F (12.2°C to 12.7°C).
4.0 CASE STUDY ON MODELLING CHILLED BEAM SYSTEM IN HAP
LOCATION: HYDERABAD, ANDHRA PRADESH, INDIA.
CLIMATE: Tropical Climate
Temperature: 106 °F, Humidity: 80%, Latitude: 17.5°, Longitude: 78.5°
Summer Dry Bulb 106 °F,
Summer Wet Bulb 78 °F,
Winter Dry Bulb 55 °F,
Summer Daily Range 14 °F
Room design set point of 75 °F/50% RH (~ 55 °F DP)
Cooling coil LAT 55 °F.
4.1 Design Considerations:
Primary air from DOAS unit enters beam @ 44-55 °F
Resulting supply air to room @ 64-66 °F
Chilled beam system is a 4-pipe cooling & heating system with cooling and heating provided in the
beam.
Terminal Units are selected as the Equipment Type and 4-pipe Fan Coil as the System Type.
"Common Ventilation System" is HAP's term for the DOAS unit.
The chilled water plant for chilled beam systems needs to operate at two supply water
temperatures. The DOAS needs to receive cold water at a supply temperature like 44 °F in order to
condense sufficient moisture out of the outdoor air stream to handle the space latent load.
Figure 2 Active Chilled Beam for the case study. Drawing is prepared using RevitMEP

323
Figure 3 Active Chilled Beam – Isometric Layout for the case study. Drawing is prepared using
RevitMEP
Floor Areas and Window-to-Wall Ratios
Proposed
Design Baseline
Total Conditioned Floor Area
(ft²)
1,485 1,485
Total Floor Area (ft²) 1,485 1,485
Window to Wall Ratio 6 % 6 %
Gross Wall Area (ft²) 1,919 1,919
Vertical Window Area (ft²) 118 118
Performance Rating Table - Performance Rating Method Compliance
End Use
Proce
ss
Baseline
Building
Units
Baseline
Building
Results
Proposed
Design
Energy
Type
Proposed
Design Units
Proposed
Building
Results
Percent
Savings
Space Heating No Energy kWh 98,127 Electric Energy kWh 8,363 91 %
Demand kW 11.7 Demand kW 1.0 92 %
Space Cooling No Energy kWh 50,115 Electric Energy kWh 33,661 33 %
Pumps No Energy kWh 7,768 Electric Energy kWh 8545 -10 %
Demand kW 1.0 Demand kW 1.1 -10 %
Heat Rejection No Energy kWh 13,719 Electric Energy kWh 10,742 22 %
Energy Totals
Baseline Total
Energy Use (kBTU)
654,558
Proposed Total Energy
Use (kBTU)
276,919 58 %
Baseline Annual
Process Energy
(kBTU)
34,926
Proposed Annual
Process Energy (kBTU)
34,926 0 %

324
Energy Cost and Consumption by Energy Type - Performance Rating Method Compliance
Proposed Design Baseline Design
Energy Type Energy Use Energy Use
Electric 80,933 kWh 191,840 kWh
Subtotal (Model
Outputs)
276,919 kBTU 654,558 kBTU
Energy Use
Net Proposed Design
Total
276,919 kBTU
Percent Savings Energy Use Intensity
Energy
Proposed
Design
(kBTU/ft²)
Baseline
Design
(kBTU/ft²)
Summary Data 57.7 % 186.47 440.66
CONCLUSION:
In conclusion, chilled beams are becoming more popular. They provide many operational and
design advantages, as discussed. By decoupling the ventilation loads from the zone sensible and latent
loads, the terminals are designed to handle lower total airflow quantities, thereby using smaller
equipment while resulting in uniform air distribution, high air-change rates and uniform temperatures
in the zone with fewer drafts. It is important to account for the zone latent loads in design
considerations and to ensure proper sizing of the DOAS including the ventilation air loads plus the
zone latent loads, while the chilled beams are sized to handle the zone sensible loads only.
Although they are not the solution for every space within commercial and institutional
buildings, the strengths of active chilled beams are becoming a more useful tool to handle challenging
spaces in today’s high performance buildings.
REFERENCES
1) Design Considerations for Active Chilled Beams. By Darren Alexander,P.Eng. And Mike
O’Rourke
ASHRAE Journal, September 2008
2) REHVA Guidebook No 5, Chilled Beam Application Guidebook Maija Virta (ed.), David Butler,
Jonas Gräslund, Jaap Hogeling, Erik Lund Kristiansen, Mika Reinikainen, Gunnar Svensson.
3) Sevcon Price Chilled Beam. PTP (Price Training Programs). Hydronic Heating/Cooling Systems
4) Engineered Systems January 2011 , (Page 30 ~36) Practical Implementation Of Chilled Beams For
Offices. BY PETER RUMSEY, P.E., FASHRAE, AND JOHN WEALE, P.E., LEED® AP
5) Chilled Beams for User Wellbeing and Sustainable Buildings. Halton
6) Chilled Beam systems as a new HVAC possibility By, Muzaffar Ali and Vishal Chauhan
7) http://www.activechilledbeam.com.
8) P.S.Joanna, Jessy Rooby, Angeline Prabhavathy, R.Preetha and C.Sivathanu Pillai, “Behaviour Of
Reinforced Concrete Beams With 50 Percentage Fly Ash” International Journal Of Civil Engineering
& Technology (IJCIET) Volume 4, Issue 2,2013, Issn Print : 0976 – 6308, Issn Online : 0976 - 6316

Low energy consumption hvac systems for green buildings using chilled beam technology

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