Mechanical Systems for Buildings

CHILLED BEAMS

2014

STUDENT: JULIA KONNOVA

1

Executive Summary

Mechanical Systems are very important parts of the building, as they provide comfortable

environment for the occupants and equipment inside, including building structure itself and its

materials.

Heating, ventilation and air conditioning, known as HVAC, consists of many components and

elements in order to maintain a high performance of the whole system. Each building has its

own unique requirement for the HVAC system depending on the factors, such as climate zone,

loads, type of the building, available energy sources etc.

The design process for engineers includes the following stages:

- Calculation heat, cool loads and lost - Selecting equipment - Design duct system - Coordination between architects and other engineers.

Additionally to major tasks, to provide good design also means solving a complex of problems, such as: - Reduction of noise and air velocity - Maintenance - Control and Aesthetic view. Energy consumption, purity and initial cost of the system also plays crucial role in the system choice. New green efficient technologies were invented to solve these problems. Chilled Beam technology is one of them. As it is green, energy-efficient and effective system, low at first cost and easy in maintenance - it should not be surprising that chilled beam technology gaining an increasing popularity within an architectural and engineering practice.

2

Table of content

Executive Summary 2

Introduction 4

Overview of HVAC systems 5

Chilled Beams 6

Types of chilled beams. Passive Chilled Beam 7

Active Chilled Beam. Multiservice Chilled Beam 8

Benefits of Chilled Beams. 9

Design consideration and limitation. Conclusion 11

References 12

Appendix

Photo 8. Schematic design of passive chilled beam system paired with air-side system. 13 Photo 10, 11. Sample of implementation of passive chilled beam within office space. 14 Photo 12,13. Schematic design of Active chilled beam system paired with air-side system. 15 Photo 14, 15. Scheme of active chilled beam in cooling and heating mode. 16 Photo 16. Scheme of performance chilled beam within temperature space. 16 Photo 17-20. Design variations of chilled beams. 17

3

Introduction.

As HVAC systems take a priority part in the power consumption of the building and its life cycle,

exploration of new energy efficient technologies becomes increasingly important nowadays.

In the following report The Chilled Beams technology was investigated as energy efficient

cooling and heating system, being a decent alternative to the conventional VAV system.

The topics such as,

-Types of chilled beams,

-Application,

-Principle of work,

-Benefits, as well as

-Comparing analysis of energy saving and initial cost are covered.

Schematic drawings and photos are provided within the report and additionally in the Appendix,

illustrating each of the subjects described in details.

4

Overview of HVAC systems.

Conventional HVAC distribution components are categorized as:

Air-Side Components Water-Side Components

Ductwork Piping

Fans Valves

Air-handling units Pumps

Terminal units Expansion Tanks

Diffusers, registers, grills Heat exchangers

Terminal units

Furthermore, systems subdivided on three types: All-Air Systems, All-Water Systems, and Air-

Water Systems. Each of them have own advantages and disadvantages and assigned by

engineers depending of is more appropriate for particular climate zone, load, type and size of

the building, maintenance etc.

Duct system or ductwork is a network of ducts that are subdivided within that system depending

of service provided by each duct or channel. There are following types: An Outdoor air, Return

air, Exhaust (relief) air, mixed air, Supply air, Supply air inlets, and Return air outlets.

As it was mentioned before, in order to maintain comfortable and healthy conditions of indoor

climate and air purity, additional devices are included within the HVAC system.

Such as, carbon dioxide sensor that controls ventilation rate during periods of occupancy but

receive reduced outside air during unoccupied periods, which provides a substantial savings in

energy.

Relative humidity sensors are typically used to control humidification and/or dehumidification

equipment in environments such as retail stores, restaurants, schools, hospitals, office

buildings, data processing centers, warehouses, and food storage buildings. Dry air during

heating season can cause breath difficulties and skin discomfort, while high humidity is a cause

of moister and condensation that provides breeding ground conditions bacteria and fugs.

The recommended average relative humidity level is between 35% and 45%. This range will

provide the best comfort for people, furniture and electronic equipment.

However, conventional HVAC systems consumed large amount of energy to pump and heat or cool the air; required additional space for duct clearance and as a result increasing of the building height. Also, it is often characterized with perceived air velocity and noise level. For All-Water Systems, for example, additional ventilation is required. The explored Chilled Beam System, however, is able to solve some of these issues of conventional HVAC Systems and benefit them for a better mutual performance.

5

Chilled Beams. Chilled beams are interested as an attractive alternative to variable air volume (VAV) systems and have been proven to be effective in conditioning both new and existing buildings. Flexible and easy in installation and maintenance, energy efficient and cost effective, they are alternative to other conventional cooling systems. In spite of this system still paired with displacement ventilation systems, it allows to reduce the size of the ducting system and air handlers by one third. That saves not only space within a building, but cause energy reductions from 20 to 50%, depending on the system design, building details, and climate zone. Finned-tube radiators positioned within the ceiling surface, chilled beams can be integrated into a ceiling grid or left exposed. This technology is most applicable to interior environments where heat gain in the space – solar radiation, people, or equipment heat – is the primary factor of air flow quantities, such as: • Post-secondary educational facilities • Office buildings • LEED & Green buildings • Data centers • Television studios • Load driven laboratories • Healthcare facilities

• Retrofit of existing “Induction Unit” installations (circa 1950-1970) The principle of work is achieved on their cooling effect by convection, using finned elements

through which water at 59°F to 65°F is circulated, providing adequate cooling with minimal air

movement, noise level and fan power.

Photo 1 - Chilled beam (Photo source: Trox)

6

Types of Chilled Beams.

There are three types of chilled beams: Passive, Active and Multi-Service.

Passive Chilled Beams work with natural convection. Perforated metal tiles allow warm air to flow from the occupied zone to up the beam in the ceiling cavity. The warm air rises to the radiator, is cooled, and then descends naturally without any mechanical fans. This is a passive technology that operates purely from natural or free convection. It typically employed to offset perimeter heat gain in a building and often paired with displacement ventilation system. X-Wing chilled beam represents the very latest development in passive beam technology. Its convection ability couples with exchange energy by way of long-wave radiation. That means that X-Wing retains a high cooling effect even when the air temperature in the room is relatively low (e.g. at night or when the building is unoccupied). In this way large amounts of cold energy can be stored in the building structure during low load periods, and used to offset heat gains when the need arises.

Photo 2, 3.

X-Wing chilled beam. Cross section.

Due to natural convection, passive

chilled beams cannot be used in heating

mode since warm air will not naturally

drop from the ceiling into a room.

X-Wing Passive chilled beam

7

Active Chilled Beams (ACB) offer increased cooling capacity by using forced air to induce

convection over the elements. Conditioned primary air is supplied directly from air handling unit,

as ACB integrated into the building's primary ventilation air system.

The primary air is then supplied to the room through diffusers built into the beam. The induction

nozzles create a pressure differential across a cooling coil, “inducing” air flow from the room

across the coil and supplying cool air back to the room.

Because they rely upon powered air

movement, rather than just

buoyancy, active beams can also be

used for heating by supplying hot

water to the heat exchanger. So

they can provide either heating or

cooling, depending on the

temperature of the water supplied to

the coil.

Photo 5. Cross-sectional schematic of an active chilled beam. Both fresh ventilation air (introduced through nozzles) and warm recirculated air are cooled as they pass by the chilled beams cooling coils. Either 2-pipe or 4-pipe designs are available. The benefit of the 4-pipe configuration being that some zones can receive cold water for space cooling while other zones simultaneously receive hot water for space heating. Multi-Service Chilled Beams in addition to cooling and heating abilities may also act as a conduit to supply other building services such as lighting, speaker systems, IT systems, fire protection (sprinklers and detectors), acoustic insulation, Building Automation System sensors, and photocells. These additional settings economize ceiling surface and make design more attractive as all elements are not spread but hidden within one contemporary designed device.

Photo 4. Temperature Map.

Photo 6. Multi-Service Chilled Beam.

8

Benefits of Chilled Beams. Ventilation Many of the benefits derived from chilled beams come from their ability to recirculate the air within a space. When necessary, fresh ventilation air can be provided via conventional means or as part of an “Active Chilled Beam” system. Maintenance Depending upon the type of installation, chilled beams contain few or no moving parts. The fact that there are no internal fans or filters to repair or clean accounts for a long life expectancy and hassle free operation. In general, all maintenance associated with a chilled beam system will be at the central plant and a simple vacuuming of the beams once a year. Control In order to achieve proper interior thermal comfort, the building automation system or building operator can chose to control chilled beams individually, or controlling grouped regions of chilled beams. Acoustics Passive beams are virtually noise free, as no fans are incorporated into the system. However, active beams utilize relatively low airflow rates—typically around 40 CFM. It is recommended to incorporate a suitable acoustic in-fill membrane into the design to enhance sound absorption, without inhibiting air flow to or from the beam. Aesthetics Chilled beams can be integrated into a ceiling grid or left exposed. Aesthetic considerations may also include minimizing the visual impact of the beam. Manufacturers may work with design teams to customize the appearance of the chilled beams through molds and extrusions that better adapt to the facility’s architecture. In addition, the design and layout of chilled beams may incorporate key infrastructure components, such as lights, sprinkler heads, speakers, sensors, air nozzles, smoke detectors, and voice/data cables. Lower First Cost Water is much denser fluid than air. It is able to trap or transfer a lot more heat comparing to air. Besides generally 80 to 85% less cost to pump water, than the cost to blow air, it is also space savings. It would take a 14-in-by-14-in air duct to transport the same amount of heat as can be transported by a 1-in pipe of water. As the main volume of the primary air supplied in the room is entrained, or induced, across the chilled beam coil, the air-handling unit is only responsible for delivering a small portion of required airflow to the space. Thus, the primary airflow is what’s needed to handle the space’s ventilation, dehumidification requirements and remove sensible load, while chilled beam increase rest needed cooling. Using typical 55 F primary air, the chilled beam will handle 60 to 70% of the sensible load, potentially reducing the airflow required from the air handler by 60 to 70%. With fewer air changes needed, ductwork, air-handling units, exhaust fans, chillers, and boilers can all be downsized.

Photo 7. Air duct vs Water Pipe.

9

Chilled beams enable users to reduce greatly fan energy by adding a small amount of pump energy. The more the water does the work, the more efficient the system becomes. In new construction, this avoided first cost can help to offset the cost of the chilled beam units and infrastructure. In the following example, Chillers and boilers was reduced roughly by 60%, as the amount of air for conditioning was also reduced by 60% by using chilled beams. In spite of, reducing cost for air Handling Units, cooling, heating, ducts and control points in chilled beam system, it require additional costs for the beams, pipes and chiller. However, in summary with airside costs analysis showed that Chilled beam system has still lower initial cost comparing to the conventional VAV system. Analysis showed that it is a more efficient system for less money.

Energy Savings Chilled beams can provide potential energy reductions from 20 to 50%, depending on the system design, building details, and climate zone. One particular energy saving advantage of chilled beams is the ability to use higher chilled water supply temperatures (65°F to 59°F). This allows the chiller system to operate more efficiently and to potentially make greater use of waterside economizer control. In addition, chilled beams allow fans to operate at lower speeds, as chilled beam system required 60% less air than the VAV system. It means that both the fans and chiller are doing less work to achieve the same amount of cooling as in a conventional system. The boiler capacity could also be reduced by as much as 60% during winter because it is bringing in 60% less outside air.

The following comparing

analysis showed reducing

the transport energy (fans

and pumps) by 32%;

cooling energy by 46% and

overall HVAC energy by

35% if chilled beams are

used instead of

conventional VAV system.

10

Design consideration and limitation.

Humidity Control In humid climates, humidity controls may be a necessary addition to chilled beam systems. If not properly controlled, humidity levels may cause condensation on the surface of chilled beams. To avoid this problem, the internal humidity must be controlled such that the beam temperature is always above the dew point temperature of the air. A rule of thumb states that relative humidity should be kept below 50°F to 55°F dew point. This is equivalent to a maximum relative humidity of 50% to 55% at 72°F. The coil itself is slightly warmer than the water inside (with accurate latent load and primary airflow calculations, in addition to effective control strategies), condensation is easily avoided. If it is not possible to control the humidity in the space, chilled beams may not be the preferred method for providing space cooling. Maximum Capacity Chilled beams may not be an effective solution for spaces with exceptionally high cooling loads, which would require an impractical number of chilled beams to be installed in the ceiling. Spaces with such loads will likely be better served by a conventional cooling system. Conclusion.

After investigation of Chilled beams technology, I formed a certain opinion that it is very

sufficient, cost and energy effective, easily integrated within any contemporary design

multipurpose mechanical system.

As chilled beams subdivide on two types – passive that implement only cooling effect, and

active that provide both cooling and heating; should be considered most efficient application of

one or another type. In my opinion, in regions with dominated hot climate conditions as Arabic

countries, South America or California coast, application of passive chilled beams is sufficient

choice. While in regions requiring seasonal switches from heating to cooling, application of

active chilled beams would be a definite asset for the whole HVAC system.

Furthermore, the integration of other services, such as lighting, speaker systems, sprinklers and

detectors, into both passive and active beam, make them a multiservice system. This, as well as

opportunity to customize design and save celling height makes these devices highly

sophisticated and desired for every contemporary design from aesthetic point of view.

This system is not only energy effective, but also not required complex maintenance and

provides more comfort for people, as it maintains constant temperature, without or few air

movement and noise, comparing to the air-conditioning split or VAV systems. Its working regime

easily controls. Depending on design – one or a group of beams can be stopped at any time, or

at the same time it could work on cooling, while other group works on heating.

Comparing analysis also shows that even first cost of chilled beam system is less than first cost

of convention VAV system. In other words, it is a more efficient system for less money!

Additionally, not only new designed building could gain all advantages of the chilled beams, but

integration within an existing building saves energy of current HVAC system, as it would require

less energy for fans too cool or heat same areas.

11

References:

[1] http://energydesignresources.com/media/2621/EDR_eNews_069.pdf?tracked=true

E-News. Energy design resources. Issue 69. February 2010.

[2] http://housewares.about.com/od/humidifiersdehumidifiers/qt/humiditylevels.htm

[3] Mechanical and Electrical Systems in Architecture, Engineering and Construction, 5/e

Frank R. Dagostino and Joseph B. Wujek

[4] http://www.labdesignnews.com/articles/2013/12/chilled-beams-lab-applications

[5] http://www.automatedbuildings.com/news/feb12/articles/alc/120124021101alc.html

[6] http://continuingeducation.construction.com/article_print.php?L=5&C=463

[7] http://www.frenger.co.uk/products/multiservice-chilled-beams/principles-and-benefits-of-

multiservice-chilled-beams.html

12

Appendix.

Photo 9. Active and Passive Beams in cooling mode.

Photo 8. Schematic design of passive chilled beam system paired with air-side system.

13

Photo 10, 11. Sample of implementation of passive chilled beam within office space.

14

Photo 12,13. Schematic design of Active chilled beam system paired with air-side system.

15

Photo 14, 15. Scheme of active chilled beam in cooling and heating mode.

Photo 16. Scheme of performance chilled beam within temperature space.

16

Photo 17-20. Design variations of chilled beams.