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Chilled Beam Design Guide TB012309 Chilled Beam Design Guide Trox USA, Inc. Telephone 770-569-1433 4305 Settingdown Circle Facsimile 770-569-1435 Cumming Georgia www.troxusa.com USA 30028 e-mail [email protected] Contents Introduction to Chilled Beams 3 Chilled Beam Selection 27 Passive chilled beams 3 Passive beams selection 27 Active chilled beams 5 Passive beam performance data 28 Selection examples 31 System Application Guidelines 8 Active beam selection 32 Active beam selection examples 35 Benefits of chilled beams 8 Chilled beam applications 9 Performance Notes 38 Multiservice Chilled Beams 11 Active Beam Performance Data 39 System Design Guidelines 14 Coil pressure loss data 39 DID600 series beams 44 Comfort considerations 14 DID620 series beams 52 DID300 series beams 62 Air side design 15 Water side design 19 Chilled Beam Specifications 68 Control considerations 21 Installation and commissioning 24 Notice to Users of this Guide This Guide is intended for the sole use of professionals involved in the design and specification of TROX chilled beam systems. Any reproduction of this document in any form is strictly prohibited without the written consent of TROX USA. The content herein is a collection of information from TROX and other sources that is assumed to be correct and current at the time of publication. Due to industry and product development, any and all of such content is subject to change. TROX USA will in no way be held responsible for the application of this information to system design nor will they be responsible for keeping the information up to date. 2 Introduction Chilled beams have been employed in European HVAC There are two basic types of chilled beams (see figure sensible cooling only applications for over twenty years. 2). Passive chilled beams are simply finned tube heat Within the past few years they have become a popular exchanger coil within a casing that provides primarily alternative to VAV systems in North America. The convective cooling to the space. Passive beams do not growing interest in chilled beams has been fueled by incorporate fans or any other components (ductwork, their energy saving potential, ease of use as well as nozzles, etc.) to affect air movement. Instead they rely their minimal space requirements. on natural buoyancy to recirculate air from the conditioned space and therefore needs a high free area Chilled beams were originally developed to supersede passage to allow room air to get above the coil and the outputs achieved by passive radiant cooling ceiling cooled air to be discharge from below the coil. As they systems. Sensible cooling capacities of “chilled” ceilings have no provisions for supplying primary air to the are limited by the chilled water supply temperature space, a separate source must provide space (must be maintained above dew point to prevent ventilation and/or humidity control, very typically condensation from forming on their surfaces) and the combined with, but not limited to, UFAD. The air source total surface area available that can be „chilled‟. commonly contributes to the sensible cooling of the Obviously, this area is limited as other services space as well as controlling the space latent gains. (lighting, fire protection, air distribution & extract etc.) limit the degree of employment of the active ceiling surface such that their maximum space sensible cooling capacity is very typically less than 25 BTUH per square foot of floor area. As this is not sufficient for maintaining comfort especially in perimeter areas, chilled beams very quickly became the preferred solution in so much as they occupied less space, had fewer connection and most importantly offered sensible cooling outputs 2 to 3 times that of „chilled‟ ceilings. INTRODUCTION TO CHILLED BEAMS Passive Chilled Beam Chilled beams feature finned chilled water heat (Exposed Beam Shown) exchanger cooling coils, capable of providing up to 1100 BTUH of sensible cooling per foot of length and are designed to take advantage of the significantly higher cooling efficiencies of water. Figure 1 illustrates that a one inch diameter water pipe can transport the same cooling energy as an 18 inch square air duct. The use of chilled beams can thus dramatically reduce air handler and ductwork sizes enabling more efficient use of both horizontal and vertical building space. 18“ x 18“ Air Duct Active Chilled Beam Figure 2: Basic Beam Types 1“ diameter Water Pipe Active chilled beams utilize a ducted (primary) air supply to induce secondary (room) air across their Figure 1: Cooling Energy Transport integral heat transfer coil where it is reconditioned prior to its mixing with the primary air stream and subsequent Economies of Air and Water discharge into the space. The primary air supply is typically pretreated to maintain ventilation and humidity control of the space. The heat transfer coil 3 Passive Chilled Beams provides sensible cooling, it is not used to condense or combine resulting in a higher velocity in the occupied provide latent cooling. space. Air discharge across the face of the beam should be avoided as this can reduce the cooling output Further discussion of the performance, capacities and by inhibiting the flow of warm air into the heat ex- design considerations for each type of beam is provided changer coil. in the following sections of this document. Passive Chilled Beam Variations PASSIVE CHILLED BEAMS Passive chilled beams may be located above or below Passive chilled beams are completely decoupled from the ceiling plane. When used with a suspended ceiling the space air supply and only intended to remove sensi- system recessed beams, TROX TCB-RB, are located a ble heat from the space. They operate most efficiently few inches above the ceiling and finished to minimize when used in thermally stratified spaces. their visibility from below. Figure 4. illustrates such a recessed beam application. Figure 3. illustrates the operational principle of a pas- sive beam. Warm air plumes from heat sources rise naturally and create a warm air pool in the upper portion of the space (or ceiling cavity). As this air contacts the coil surface, the heat is removed which causes it to drop back into the space due to its negative buoyancy relative to the air surrounding it. The heat is absorbed lifting the chilled water temperature and is removed from the space via the return water circuit. About 85% of the heat removal is by convective means, therefore the radiant cooling contribution of passive chilled beams is minimal and typically ignored. Figure 4: Recessed Beam Installation Recessed beams are concealed above the hung ceiling and should also include a separation skirt (TCB-RB- Skirt) which assures that the cooled air does not short circuit back to the warm air stream feeding the beam. Recessed beams (TROX series TCB) may be either uncapped (standard) or capped (more commonly known as shrouded) (see figure 5). Capped or shrouded beams have a sheet metal casing which maintains separation between the beam and the ceiling air cavity which is often used for the space return air passage. This also provides acoustical separation be- tween adjacent spaces. Figure 3: Passive Beam Operation Passive chilled beams are capable of removing 200 to 650 BTUH of sensible heat per linear foot of length Separation Skirt depending upon their width and the temperature difference between their entering air and chilled water mean temperature. The output of the chilled beam is Figure 5: Capped Passive Beam usually limited to ensure that the velocity of the air dropping out of the beam face and back into the Passive beams mounted flush with or below the ceiling occupied zone does not create drafts. surface are referred to as exposed beams. Most ex- posed beams (e.g., TROX TCB-EB and PKV series) are It should also be noted that the air descending from a furnished within cabinets designed to enhance the ar- passive beam „necks‟ rather like slow running water out chitectural features of the space as well as assure the of a faucet. This slow discharge can be effected by necessary air passages for the beam. other air currents around it and should passive beams be installed side by side, the two airstreams will join and 4 Active Chilled Beams TROX Passive Chilled Beams TROX USA offers 2 ranges of passive chilled beam as Primary air the core engine behind the variants. supply TCBU series beams offer a full range of 1 & 2 row recessed and exposed passive beams. Suspended PKVU series beams are 1 row passive beams ceiling with or without exposed cabinets. Figure 6 illustrates an exposed passive beam in whose cabinet other space services (lighting, smoke and occupancy detectors, etc.) have been integrated. Such integrated beams are referred to as integrated or multi- service chilled beams (MSCB). As with recessed beams, it is generally recommended that the cross Figure 7: Active Chilled Beam Operation sectional free area of the passage into an exposed chilled beam be equal to at least one its width. For more information on these beams see pages 27-31. well. In these cases, displacement ventilation and con- ditioning will be used to produce a thermally stratified room environment. Active chilled beams typically operate at a constant air volume flow rate, producing a variable temperature discharge to the space determined by the recirculated air heat extraction. As the water circuit can generally extract 50 to 70% of the space sensible heat genera- tion, the ducted airflow rate can often be reduced ac- cordingly, resulting in reduced air handling requirements as well as significantly smaller supply (and ex- haust/return) ductwork and risers. Active chilled beams can provide sensible cooling rates as high as 1100 BTUH per linear foot, depending on their induction capabilities, coil circuitry, and chilled water supply temperature.
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