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Chilled Beams TROX USA for Laboratory HVAC Applications
• • • • • • • • • • • TROX USA
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Chilled Ceilings and Beams
• • • • • • • • • • • Chilled Ceilings and Beams Early 1980’s 1980 1990 2005 Chilled Ceilings Buildings well insulated for heating Advent of personal computers Need to remove heat from space Limited space available Chilled ceiling systems were first developed in Scandinavia in the 1970’s. Summer design conditions for this region were quite moderate and allowed buildings to use natural ventilation, however, they were very well insulated due to rigorous winter design (heating) requirements. This (heating) was accomplished from low level locations. The advent of personal computers caused significant heat build up due to the heavy insulation. Some means of removing that heat was required and existing buildings had little or no overhead space to accommodate air ducts. Chilled ceilings offered an ideal solution as they took very little space and were very efficient in the removal of the space heat.
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Principle of Operation
Chilled Ceiling Panels • • • • • • • • • • • CWS = 59 to 62ºF CWR = 62 to 66ºF 55% Convective 45% Radiant Chilled ceilings transfer derive some 55% of their heat transfer through radiation from heat sources within the space. The human body’s heat transfer is about 70% radiant, while heat transfer equipment within the space is only 10 to 20% radiant. These systems therefore focus on the conditioning of the occupants while isolating much of the heat generated by the equipment and lighting. Chilled ceilings (and beams) usually employ supply water temperatures between 60 and 62F, (well above normal space dew points) to assure that condensation does not occur. They are also fitted with dew point monitoring or moisture sensing controls as a safety net.
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Radiant Effect on Occupants
Chilled Ceiling Panels • • • • • • • • • • • 77° F 74.5° F Dry Bulb Temp. Effective Radiant Temp. It is generally acknowledged that the space temperature can be maintained some 2 to 3F warmer when chilled ceilings are used due to their radiant effect which is not measured by normal space temperature sensors. Another feature of chilled ceilings is that they are essentially self-regulating in that their return water temperature is a direct function of the heat sources in the space. If little or no sources are present the water simply return s at a lower temperature without sub-cooling the space resulting in far greater individual comfort control.
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Chilled Ceiling Systems
• • • • • • • • • • • Chilled Ceiling Systems Improved thermal comfort Typically combined with displacement ventilation system Low turbulence intensity decreases draft risks Chilled ceiling systems offer excellent thermal comfort and space ventilation as they are typically combined with a low turbulence displacement ventilation system. Chilled ceiling systems rely on a separate air distribution system to ventilate and dehumidify the space.
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Chilled Ceiling Systems
• • • • • • • • • • • Chilled Ceiling Systems Improved thermal comfort Minimal space requirements No additional space required in ceiling cavity Easy to install in retrofit applications Chilled ceilings require only 6 to 8 inches of ceiling cavity depth. Due to the space allocation for lights, sprinkler heads and supply/return grilles the ratio of active area to gross ceiling area is usually a maximum of 75%. Therefore, the chilled ceiling capacity is about 18 BTUH/FT2.
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Chilled Ceiling Systems
• • • • • • • • • • • Chilled Ceiling Systems Improved thermal comfort Minimal space requirements Low energy cooling solution High heat transfer efficiencies using water Low transport costs Chilled ceiling systems also offered a low energy solution. The heat transfer capacity is four times that of air on a weight basis. As transport costs are primarily dependent on volume flow rate, the horsepower required to transport cooling energy by means of air is 25 to 30 times that required to transport the same amount of energy by means of water!
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Flow Cross Section Ratio
• • • • • • • • • • • Cooling Capacity Comparison 1 : 327 Flow Cross Section Ratio 18“ x 18“ Air Duct 1“ diameter Water Pipe This slide illustrates the efficiency of a hydronic HVAC delivery system to that of an all air strategy. The same cooling can be delivered in a 1” diameter pipe as that delivered by an 18” x 18” air duct!
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Chilled Ceiling Systems
• • • • • • • • • • • Chilled Ceiling Systems Improved thermal comfort Minimal space requirements Low energy cooling solution Limited Cooling Capacity 25 BTUH/FT2 of active panel 18 BTUH/FT2 of floor area (based on 70% active ceiling) Despite the energy savings inherent to the chilled ceiling solution, their applicability is often limited by their cooling capacity. Chilled water temperatures must be maintained at or above the space dew point temperature to avoid condensation. Under such conditions, the cooling capacity of the chilled ceiling panels is limited to about 25 BTUH/ft2 of active panel. As lights, sprinklers and other elements must also be mounted in the ceiling chilled ceiling elements can only comprise about 70% of the total ceiling. This translates to about 18 BTUH/ft2 sensible cooling per square foot of floor area. As such chilled ceilings are not feasible for conditioning perimeter areas with large sensible cooling requirements.
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Chilled Ceilings and Beams
• • • • • • • • • • • Chilled Ceilings and Beams Early 1990’s 1980 1990 2000 2005 Chilled Ceilings Passive Beams Increased equipment loads Greater occupant densities In the 1980’s, chilled ceilings became popular throughout northern Europe. However, as the density of electronic equipment in offices increased it became obvious that chilled ceilings could not adequately cool perimeter spaces. In the early 1990’s passive chilled beams replaced chilled ceilings in these areas. Inadequate perimeter cooling Technology revolution
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• • • • • • • • • • • Passive Chilled Beams Ceiling manufacturers begin to sell high free area perforation panels competitively Convective coils replace ceiling panels Passive beams rely on natural convection to transport warm air vertically to the beam location. The term “passive” is applied to beams which have no air connection, thus no mechanical means of inducing air through the coil. Passive beams may be either recessed or exposed. Exposed beams may be either surface mounted or pendant mounted. The cabinet encasing the beam can be customized to almost any appearance the architect might desire.
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Passive Chilled Beams Concrete soffit • • • • • • • • • • •
• • • • • • • • • • • Passive Chilled Beams Concrete soffit Chilled beams are also hydronic cooling solutions but their heat transfer is primarily (about 85%) convective. Instead of relying on a cool radiant surface, chilled beams circuit warm recirculated room air through a convective cooling coil. Warm air rising in the space pools at the lower level of the slab. This pooling causes the air to contact the chilled water coil. The cooled air then falls naturally into the space due to its negative buoyancy
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Passive Chilled Beam Air Distribution Pattern • • • • • • • • • • •
• • • • • • • • • • • Passive Chilled Beam Air Distribution Pattern Typical air flow pattern for recessed and exposed passive chilled beams. This shows the ideal installation with under floor air distribution, high level distribution can be used but careful selection is required tp avoid there high level diffusers interfering with the passive chilled beams.
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Passive Chilled Beams Exposed Beams Recessed Beams
• • • • • • • • • • • Exposed Beams Passive chilled beams can be either recessed (photo above left) or exposed (photo above right). When recessed beams are utilized, care must be taken to assure that the ceiling surface directly below and adjacent to the beam is of a sufficient free area to allow the air to pass through the surface. Usually this free area should be at least 50%. Recessed Beams
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Passive Beam Components
• • • • • • • • • • • Passive Beam Components Support Rods This slide illustrates the mounting of an exposed beam. Heat Transfer Coil Separation Skirt Optional Cabinet
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H is between 4 and 12 in. Z should be ≥ 0.33B
Passive Chilled Beams Interior Area Installation • • • • • • • • • • • H is between 4 and 12 in Z should be ≥ 0.33B Z H In order to provide a sufficient path for the return and supply of the recirculated air, the recommendations in this slide should be observed. B B x 2
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Passive Chilled Beams Perimeter Installation B B x 1.5
• • • • • • • • • • • When mounted adjacent to a perimeter wall, the inlet area of the beam may be reduced as the buoyancy of the rising air is typically greater. B B x 1.5
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Passive Beam Installations
• • • • • • • • • • • Passive Beam Installations This project uses chilled ceilings for interior spaces while (recessed) passive beams are used in perimeter and conference areas.
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Passive Beam Installations
• • • • • • • • • • • Passive Beam Installations This project is a credit card call center which uses exposed passive beams throughout. The space ventilation and dehumidification is affected by an underfloor air distribution system.
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Chilled Ceilings and Beams
• • • • • • • • • • • Chilled Ceilings and Beams Mid 1990’s 1980 1990 2000 2005 Chilled Ceilings Passive Beams Active Beams Like chilled ceiling systems, passive beams required a separate air supply to dehumidify and ventilate the space. In the early 1980’s, contractors began to request that the air supply be integrated into the chilled beam so a separate air outlet was not required. This led to the development of active chilled beams. Continually increasing sensible loads Greater occupant densities Gypsum board tiles become common Combine cooling and ventilation
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Active Chilled Beams Concrete soffit Primary air supply
• • • • • • • • • • • Active Chilled Beams Concrete soffit Primary air supply Suspended Ceiling Active chilled beams discharge primary air through induction nozzles to induce room air over an integral heat transfer coil. Here it is reconditioned then mixed with the primary air stream for reintroduction to the space. The induction of the air through the coil significantly enhances the cooling capacity of the unit.
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Active Chilled Beam Air Distribution Pattern • • • • • • • • • • •
• • • • • • • • • • • Active Chilled Beam Air Distribution Pattern The resultant space air diffusion is similar to that affected by a ceiling slot diffuser, that is a fully mixed system.
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Active Chilled Beams Sensible loads up to 70 BTUH/FT2
• • • • • • • • • • • Active Chilled Beams Sensible loads up to 70 BTUH/FT2 Primary air delivered at conventional (50 to 55ºF) temperatures at or near minimum ventilation flow rate Can be used with fiberglass ceiling tiles or without any ceiling Active beams have significantly higher cooling capacities than either passive beams or radiant ceilings. Due to their induction capabilities, active beams may also incorporate heating coils. TROX DID series ceiling induction diffusers are examples of active beams.
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Active Beam Installation
• • • • • • • • • • • Active Beam Installation This slide illustrates an installation of TROX DID 600 active beams in a trading area where sensible loads up to 100 BTUH/ft2 exist.
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Active Beam Installation
• • • • • • • • • • • Active Beam Installation This slide illustrates another view of the previous installation of TROX DID 600 active beams.
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Comparative Energy Costs
• • • • • • • • • • • Comparative Energy Costs $1.50 Cost to chill water Cost to transport water Cost to cool air Cost to transport air LEGEND $1.00 $0.80 Typical Annual HVAC Energy Cost ($/FT2) $0.48 This slide illustrates the relative energy consumption of a hydronic cooling system (with either natural or forced ventilation) versus a VAV (all air) system. Chilled Ceiling with Natural Ventilation Passive Beam with Displacement Ventilation Active Chilled Beam VAV System
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Active Chilled Beams For Laboratory HVAC Applications
• • • • • • • • • • • 1990 2000 2005 Chilled Ceilings Passive Beams Active Beams Recently, several major engineering firms involved in laboratory design began to research the advantages of chilled beams when applied to laboratory spaces. Active Beams for Lab HVAC
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Laboratory Design Issues
• • • • • • • • • • • Laboratory Design Issues Space sensible heat gains of 60 to 70 BTUH/FT2 Space ventilation requirements of 6 to 8 ACH-1 Laboratories where chemicals and gases are present require 100% OA All air systems require 18 to 22 ACH-1 to satisfy sensible load Although the required number of air changes in make up air driven laboratories are often high due to a high density of fume hoods, most laboratories are not so densely populated. Many general use laboratories have very high sensible heat gains due to a large amount of electronic equipment and thermal processes. Sensible gains of 65 to 70 BTUH/ft2 are not uncommon. The ventilation rates for these laboratories are mandated at 6 to 8 ACH-1 but all of the ventilation air must be outside air due to the use of gases and chemicals within the space. In order to condition the space, all air systems (100% outside air) must supply 18 to 22 ACH-1, far more than the mandated ventilation rate. All of this air must be conditioned to 55˚F at the air handler before being delivered to the space.
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Active Chilled Beams in a General Use Laboratory • • • • • • • • • • •
• • • • • • • • • • • Active Chilled Beams in a General Use Laboratory Sensible Heat Gain = 65 BTUH/FT2 Ventilation Rate = 8 ACH-1 8’ Active Beams 12 CFM/LF 44 ft. 22 ft. T This slide illustrates a laboratory with TROX DID 600 series chilled beams. The space sensible gain is 65 BTUH/ft2 and the mandated ventilation rate is 8 ACH-1. The piping and ductwork connections are also illustrated. Note that the installation requires a single space thermostat and chilled water valve and two constant air volume regulators.
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Active Chilled Beams in a General Use Laboratory • • • • • • • • • • •
• • • • • • • • • • • Active Chilled Beams in a General Use Laboratory Sensible Heat Gain = 65 BTUH/FT2 All Air Solution = 18 ACH-1 Ventilation Rate = 8 ACH-1 Air-Water Solution = 8 ACH-1 8’ Active Beams 12 CFM/LF 44 ft. 22 ft. 12’ o.c. As the chilled beams are capable of removing about 60% of the space heat by means of their chilled water coil, the system is capable of conditioning the laboratory with an airflow rate equal to the specified minimum ventilation rate (8 ACH-1). In this case, only 45% of the total space sensible heat gain (5.25 tons) is removed by air while the remainder is removed by the chilled water coil within the beam. An all air system would have required an airflow rate of 18ACH-1 to accomplish the required space conditioning!
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Case Study Laboratory Design for Pharmaceutical Company
• • • • • • • • • • • Case Study Laboratory Design for Pharmaceutical Company Location: St. Louis, MO Outdoor Design Conditions: 94DB/75WB Laboratory Space: 54,000 FT2 Minimum Ventilation Rate: 8 ACH-1 Space Sensible Heat Gain: 72 BTUH/FT2 A major laboratory designer recently compared the use of active chilled beams to an all air (variable air volume system) for a pharmaceutical laboratory in St. Louis, MO.
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Sensible Cooling Chiller System
• • • • • • • • • • • Equipment Requirements Equipment Conventional VAV Active Chilled Beam Air Handling Units 180,000 CFM 72,000 CFM Cooling 1,477 Tons 587 Tons Heating 21,617 lbs/hr 8,588 lbs/hr Duct Distribution 285,493 lbs. 214,120 lbs. Control Points 800 Chilled Beams 1,056 Piping Distribution 4,200 LF Sensible Cooling Chiller System 200 Tons The chilled beam system allowed the airflow requirements to be reduced to 8 ACH-1 versus 20 ACH-1 required at design conditions for the VAV system. The air handler’s design refrigeration capacity was also reduced proportionally since a dedicated chiller was planned for the chilled water supply to the beams. The refrigeration capacity of the air handling unit for the VAV system was designed to handle the space load (332 tons) and the load (1145 tons) associated with conditioning the outside air(180,000 CFM) to 55˚F. The air handling unit for the chilled beam system was tasked with 40% of the space load (or 133 tons) plus the load (454 tons) of conditioning the outside air to 55˚F. The reduced airflow requirements of the chilled beams also resulted in a significant reduction in ductwork sizes. Approximately 33% savings in sheet metal was realized. The dedicated chiller was sized to handle 60% of the total space load (332 tons). It should also be noted that the operating efficiency of this chiller was enhanced some 40% due to the higher temperatures (50/56) of the supply and return chilled water!
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Cooling Energy Requirement
• • • • • • • • • • • Cooling Energy Requirement Example 1000 FT2 LAB (10’ CLGS) TSHG = 70 BTUH/FT2 VENTILATION = 8 ACH-1 8.0 7.0 6.0 TOTAL ENERGY, ALL AIR SOLUTION 5.0 4.0 TOTAL COOLING ENERGY (kW) TOTAL ENERGY, AIR-WATER SOLUTION 3.0 45% 2.0 The annual cooling energy savings of the chilled beams for this example averaged 45% less than that for the VAV system. Chilled beam air side cooling 1.0 Chilled beam water side cooling 60 65 70 75 80 85 90 OUTDOOR TEMPERATURE (°F)
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Overall 35% Reduction in Energy Costs
Energy Comparisons Case Study, 93/75F Outdoor Design • • • • • • • • • • • Active Chilled Beam (Parallel Sensible Cooling) Reduced fan power – 32 % from Base VAV Reduced cooling energy – 46 % from Base VAV Reduced ductwork sizes – ACPH to 6-8 ACH-1 Higher Pumping energy – 15% - Offset by other savings Higher cooling system efficiencies Overall 35% Reduction in Energy Costs The designer also estimated the fan energy use to be 32% less than that of the VAV system. The pumping energy was slightly higher but was a relatively insignificant part of the total energy usage. In summary, the designer identified the overall energy savings to be 35%.
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Overall 25% Reduction in Energy Costs
Energy Comparisons Modified for 80/64F Outdoor Design • • • • • • • • • • • Active Chilled Beam (Parallel Sensible Cooling) Reduced fan power – 32 % from Base VAV Reduced cooling energy – 30 % from Base VAV Reduced ductwork sizes – ACPH to 6-8 ACH-1 Higher Pumping energy – 15% - Offset by other savings Higher cooling system efficiencies Overall 25% Reduction in Energy Costs The application of such a system in a mild climate (80/64F design), would result in a smaller (but still significant) cooling energy savings. In total, the overall energy savings would still be 25%.
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Sensible Cooling Chiller System
• • • • • • • • • • • Equipment Requirements Equipment Conventional VAV Active Chilled Beams Air Handling Units $2,264,335 $899,610 Cooling $1,627,799 $646,717 Heating $244,267 $97,046 Duct Distribution $1,481,709 $1,111,282 Control Points $1,200,000 $1,140,000 Chilled Beams $1,652,984 Piping Distribution $266,444 Sensible Cooling Chiller System $265,373 Totals $6,818,109 $6,079,456 The equipment costs for the chilled beam system were also found to be less than that of a VAV system. Although the beams (including the chiller and piping system) themselves were quite expensive ($6,500 per ton of space cooling), the savings in the air handling unit and refrigeration plant far exceeded this cost. The overall cost of the chilled beam solution was about 10% below that of a VAV (all air) solution.
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Chilled Ceilings and Beams
• • • • • • • • • • • Chilled Ceilings and Beams TROX USA
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