Halton HVAC Handbook Chilled Bean Design Guide
Halton HVAC Handbook Chilled Bean Design Guide
Halton HVAC Handbook Chilled Bean Design Guide
Halton
Halton believes that high quality indoor air is the key to a healthier and more productive life. We make this possible by delivering leading indoor climate products and solutions, ranging from commercial buildings to Marine and offshore environments systems. Haltons broad chilled beam range offers solutions from active and passive chilled beams to service beams. Halton chilled beams are designed to provide advanced flexibility, comfort and competitive life cycle costs. Here are some of our references world-wide.
Halton active chilled beams create unique flexibility and good indoor climate conditions during the life cycle of the building.
Active beam range includes various outlook options for applications ranging from offices to hospital wardrooms.
Halton chilled beams adapt easily to different interior designs of the space. Installations vary from exposed to concealed.
Passive chilled beams offer various alternatives for installation of the products for renovations and new builds.
Active service beams integrate various building services e.g. luminaires, cabling, loud speakers, sprinklers into a single unit.
Passive beams are also available as service beam concept and can integrate various services into all-in-one solution.
Contents
1. Chilled beam system 2. Target definition 3. Active chilled beams 3.1 Active chilled beam system 3.2 Chilled beam system design 3.3 System design strategies 3.4 Design elements 3.5 Chilled beam model selection 3.6 Adaptable chilled beam concepts 3.7 Chilled beam orientation and ventilation arrangements 3.8 Operation range specification 3.9 Product selection 3.10 Indoor climate conditions design 3.11 Management of room conditions 3.12 Case study 4. Passive chilled beams 4.1 Passive chilled beam system 4.2 Chilled beam system design 4.3 Chilled beam model selection 4.4 Chilled beam orientation and ventilation arrangements 4.5 Operation range definition 4.6 Pre-selection and selection 4.7 Design of indoor climate conditions 4.8 Management of room conditions 5. Customised service beams 5.1 Luminaires and other integrated technical services
5 6
7 8 9 10 12 14 22 24 25 26 27 30
31 32 33 35 37 38 40 48
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Contents
3
Haltons chilled beam system is an air conditioning system for cooling, heating, and ventilation in spaces where good indoor climate and individual space control are appreciated. A chilled beam system provides comfortable thermal conditions with quiet and energy-efficient operation. The system can be realised with active or passive chilled beams, integrated multi-service chilled beams, or bulkhead-installed horizontal induction units.
2. Target definition
When the main targets for system operation and performance are set, indoor climate target values are specified. One of the key goals in designing good indoor climate conditions is to adjust the cooling and heating capacity to the level that meets both optimal comfort and energy-efficiency targets. In addition, module sizing and flexibility requirements are important factors influencing both design decisions and life-cycle cost management for the building. It is also important to take into account national and international standards and building codes. Indoor climate design conditions: Thermal conditions as specified in national or international standards or classifications Room air temperature or operative temperature Mean room air velocity or draught rate (DR) Internal surface temperatures and radiant asymmetry Air quality criteria as specified in national or international standards or classifications air quality often is indicated in terms of: Outdoor air flow rate CO2 concentration Sound level requirement is expressed as: Noise Criterion NC Sound pressure level Lp(A) Typical space design data Room and module dimensions Space usage, internal load and occupancy levels Window and wall types, and solar shading Life cycle costs: Target system investment cost level ($/ft2) Energy-efficiency targets' levels can be expressed as specific level of consumption of heating energy and air conditioning and electric power (fan power). The building should be classified according to these consumption levels. Maintenance level targets indicate: Predicted service intervals Labor demand Accessibility of service points Need to replace parts / replacement interval (valve, filter, motor, and other parts.) Flexibility for change: Flexibility requirements can be characterized with the required tasks when layout or the use of space changes: Need for office / meeting room changes Need to relocate internal walls Need for installation / reconnection of terminal units or control units Adjustment of airflow rates Adjustment of water flow rates Other adjustments (e.g. personal requirements) Order delivery chain: Targets for order delivery indicate the versatility of the terminal unit in terms of their models, sizes and operation parameters.
Indoor climate factor Unit Operative temperature Operative temperature Vertical temperature gradient Mean air velocity Mean air velocity Sound pressure level Sound pressure level Ventilation rate Ventilation rate Ventilation rate Design assumptions Winter Summer 0.3 ft / 0.3 ft Winter Summer Office rooms Landscape offices Office rooms Landscape offices Meeting rooms Occupancy: F F F fpm fpm NC NC cfm/ft2 cfm/ft2 cfm/ft2
Clothing:
office rooms 100 ft per person landscape offices 70 ft2 per person meeting rooms 50 ft2 per person 0.5 clo summer; 1.0 clo winter
Indoor climate target levels according to CEN report 1752, on maximum values for thermal conditions.
Target denition
6
Schematic diagram of a chilled beam system with both cooling and heating functions.
Ventilation Ventilation using active chilled beams is an efficient mixing ventilation application that results in uniform air quality. Supply air is discharged into the space through linear slots on either both sides or only one side of the chilled beam. Horizontal induction units have grilles for horizontal air supply. In demand-based ventilation applications, supply airflow can be increased by means of an integrated diffuser without affecting the heat transfer of the chilled beam. Cooling Active chilled beams use the primary air to induce and recirculate the room air through the heat exchanger of the unit, resulting in high cooling capacities and excellent thermal conditions in the space. High-temperature cooling enables the use of various free-cooling sources, like outdoor air, sea water and geothermal energy etc. Heating Integration of heating into chilled beams is recommended when the specific heating capacity of the chilled beam units is reasonably low (155 260 Btuh/ft), and the low heat transmission through the windows prevents a downdraught under the window. Low-temperature heating enables the use of various waste-heat sources. Alternatively to hydronic heating, electric heating can be integrated in chilled beam units.
Use of the space Changes in use of the space and layout changes with marginal churn costs. Optimized performance and unit cost for individual spaces with limitations in flexibility. Relatively high churn costs.
Efficiency of logistics Effective design, installation, and commissioning processes; streamlined logistics with a uniform product range. Need for individual product identification in design, ordering, delivery, and installation. Life-cycle performance Higher investments in more efficient chilled beams (greater difference), enabling savings in pipework central units and lower operation costs. Lower investment costs for chilled beams and higher total investment and operating costs.
Room temperature, summer Room temperature, winter Supply air temperature Water inlet temperature, cooling Water inlet temperature, heating Target duct pressure level Target water flow rate, cooling Target water flow rate, heating Noise criteria Note * Note **
Outdoor air flow rate / floor area, offices Outdoor air flow rate / floor area, meeting Outdoor air flow rate / effective unit length Additional air flow rate in meeting rooms Cooling capacity / floor area Cooling capacity / effective unit length Heating capacity / floor area Heating capacity / effective unit length
0.33 0.55 cfm/ft2 : 0.33 0.9 cfm/ft2 3.6 ... 9 cfm/ft 0 ... 53 cfm per unit 25 Btuh/ft2 250 Btuh/ft 4 Btuh/ft
2
150 Btuh/ft
It is reasonable to study the room air velocity conditions carefully It is reasonable to study the thermal conditions carefully
System design strategy Room air temperature Room air velocity Room air quality CO2- concentration Ventilation rate Cooling capacity levels Heating capacity Adaptable performance
Traditional concept 754 3.5 F ...50 fpm ... 60 fpm temporarily during peak loads 1000 ppm 0.375 cfm/ft2 (constant airflow in meeting rooms, or separate variable airflow application) 2040 Btuh/ft2 620 Btuh/ft2 Adaptation by increasing the number of terminal units.
900 ppm 0.31 cfm/ft2 (variable flow in meeting rooms) 2025 Btuh/ft2 612 Btuh/ft2 Halton Velocity Control (HVC) is designed at normal position (2). Adjustment in throttle (1) and full (3) position, when required. Adjustment of constant airflow rates and using Halton Air Quality (HAQ) control. Always perpendicular to perimeter wall Full flexibility in layout and application changes: no installation work during changes. Churn costs of 100130 $/ft2. Some extra cost for flexibility in room units, zones, and central system costs. Nozzle size, length, and effective length that are the same using adaptable active chilled beams.
Either parallel or perpendicular to perimeter wall Limited flexibility in layout and for changes in operation conditions. Churn costs of 7501000 $/ft2. Basic investment. Additional installations for variable flow application in meeting rooms. Various nozzle sizes, lengths, and effective lengths according requirements using basic active chilled beams. Water flow control and adjustment valves which are selected project- specifically and installed on site Eventual reselection of chilled beams after significant changes of use or size of the spaces Traditional commissioning comprising manual balancing of airflow rates using adjustment dampers manual balancing of water flow rates using adjustment valves
Product cost
Changes in space use and layout in the design and installation process Commissioning
No effect of changes in use or size of space on chilled beam selection Adjustment of chilled beams on site; no traditional commissioning needed. Constant-pressure control dampers in zones allow quick airflow rate adjustments and variable airflow in meeting rooms. Maximum limit flow valves allow quick adjustment of water flow rates without balancing need.
Design elements
10
Heating Proper system operation cannot be achieved by overdimensioning the heating capacities. In a modern office building, 8 15 Btuh/ft2 of floor area is typically sufficient heating capacity. The heating capacity of active beams is dependent on the primary airflow rate. This is why ventilation shall be in operation when heating is required. The heating capacity of active beams is typically 160 260 Btuh/ft, and the inlet water temperature should be 95 115 F to create sufficient mixing between the supply air and room air. Both window draught due to radiation and downward convective air movement during cold seasons need to be eliminated. An efficient control system is used. It is recommended to have room air temperature measurement integrated into a chilled beam, with heating control based on the room air temperature near the ceiling. The images present the room air velocities in the same space in three seasons: summer (1), spring (2) and winter (3). This study was performed using computational fluid dynamics (CFD) software. Air velocity is higher than 50 fpm in the green areas. In this type of installation, it is especially important to have windows with adequate thermal properties for avoiding excessively high room air velocities in intermediate seasons. Operation case study: Chilled beams parallel to the perimeter wall
Temperature conversion 17.7 C = 64 F 24 C = 75 F 28 C = 82 F 17 C = 62.6 F 20.2 C = 68 F 22 C = 71.6 F 13 C = 55.4 F 22 C = 71.6 F 25.4 C = 77.7 F
The images present the room air velocities in the same space in three seasons: summer (1), spring (2) and winter (3).
Design elements
11
Management of ventilation rates using Halton Air Quality (HAQ) control The air flow rate of the chilled beam is dependent on Effective length, Leff Chilled beam chamber pressure, DPm Nozzle size, Dnoz Halton Air Quality control unit adjustment position, AQ The chamber pressure is adjusted by changing the position (a) of the airflow adjustment damper to match available duct pressure at the room branch. Four nozzle sizes are available, to enable attaining the minimum supply air flow rate of the chilled beam at the set pressure level in a typical room module. There is no need to change or plug nozzles of the chilled beam. Halton Air Quality control allows increasing the chilled beam airflow rate to meet the ventilation requirements of spaces such as: office spaces: 0.3 0.6 cfm/ft2 meeting rooms: 0.7 0.9 cfm/ft2 Air flow control The ventilation requirements of meeting and team rooms vary greatly according to the occupancy level. Demand-based ventilation control using, e.g., CO2 sensors, contributes to a highly energy-efficient operation. In addition to manual adjustment damper operation, the HAQ damper can be equipped with an actuator controlled by a room controller.
By integrating the airflow control into the chilled beam unit, flexibility in use of the space is ensured. When rooms with constant and variable airflow rates are both served by the same distribution ductwork, constant pressure conditions are needed to guarantee the designed airflow rates. See the section Constant-pressure ductwork for efficiency for more information.
Office rooms.
Meeting room.
Primary airflow rate Room 1, 2, 3 4 Space type left Office Meeting room 3 2 HVC position right 1 2 Nozzles qv1 cfm 32 32 HAQ qv2 cfm 11 0 ... 53 Total qv1+ qv2 cfm 43 32 ... 85 Total qv1+ qv2 cfm/ft2 0.48 0.9
Halton ACE with air quality control. The Halton Air Quality control unit is on the top of the chilled beam, supplying air upward. It is recommended to position the beam at a minimum distance of 2 ft from the wall and 4 in from the ceiling. The Halton Air Quality control unit is adjusted manually or, alternatively, controlled by an actuator connected to a room controller. The HAQ unit can be retrofitted later as required. Also the actuator can be mounted later, when changes in room layout are implemented. Total airflow rate of the chilled beam unit can be 4 to 20 cfm/ft when equipped with HAQ control. The Halton Air Quality control unit does not increase the length of the chilled beam.
Halton ACE with air quality control in a meeting room.
Halton ACC with air quality control. In the Halton ACC solution, the air quality control unit is at the opposite end of the unit from the supply air connection. The throw pattern of the air quality control unit is bi-directional like that of the chilled beam. The effective length of a chilled beam equipped with air quality control unit (either manual or motorized version) is 2 ft shorter than the total length. The look of the Halton ACC unit is identical to that of the ABC chilled beam without HAQ unit.
Halton ACC with air quality control in a meeting room.
Management of room conditions using Halton Velocity Control (HVC) Halton Velocity Control is used for adjusting room air velocity conditions either when room layout changes (e.g., in cases where the partition wall is located near the chilled beam) or when local, individual velocity conditions need to be altered. Halton Velocity Control does not affect the primary supply air rate, but it does have a slight effect on the cooling and heating capacities of the unit. The capacities and velocities can be studied using the HIT Design software. It is recommended to design the chilled beam in the normal position in order to allow both minimization (throttle) and maximization (full) functions later in the buildings life cycle. Halton Velocity Control dampers are divided into sections to enable the desired adjustment of velocity conditions in different parts of the occupied zone. Depending on the length of the beam, optimal lengths of HVC damper modules are used as follows: ABC or ACC ABE or ACE 1 ft , 1 ft 8 in, and 2 ft 8 in 1 ft, 2 ft, and 2 ft 8 in
Halton Velocity Control provides manual velocity adjustment on both sides of the chilled beam, with three positions: 1 = throttle position, 2 = normal position, and 3 = boost position.
Adjustment of local velocity conditions is possible also in an open-plan office with Halton Velocity Control.
Partition wall located close to the chilled beam. Halton Velocity Control is adjusted to position 1 on one side and position 3 on the other.
Halton Velocity Control is available for both exposed and ceiling-installed chilled beams.
Halton Velocity Control in boost (3) and throttle (1) position in a Halton ACC chilled beam.
Halton Velocity Control in boost (3) and throttle (1) position in a Halton ACE chilled beam.
Case Study Flexibility for layout changes can be designed in with the HVC and HAQ concepts. Chilled beam installation adapts to different room sizes and layout, providing required capacities and maintaining good comfort level.
Primary airflow rate Room 1 2 3/Unit A 3/Unit B Space type left Office Office Office Office 3 3 1 3 HVC position right 1 3 3 1 Nozzles qv1 cfm 32 32 32 32 HAQ qv2 cfm 11 32 0 0 Total qv1+ qv2 cfm 43 64 32 32 Total qv1+ qv2 cfm/ft2 0.48 0.48 0.48 0.48
Constant-Pressure Air Distribution System Constant-pressure ductwork for efficiency In traditional active chilled beam systems, the ductwork is a proportionally balanced constant-air-flow distribution system. However, there are reasons it is beneficial or otherwise reasonable to arrange the airflow management using active constant-pressure control dampers. Among these are that chilled beams with pressure-dependent variable flow and constant flow are combined in the same ductwork sections and proper operation conditions are ensured frequent individual air flow adjustments of chilled beam units can be made without the need to balance the ductwork pressure control dampers allow zone ventilation operation hours locally, contributing to energy conservation in office buildings where tenants office hours tend to differ, for example Ductwork is divided into constant-pressure zones, allowing individual adjustment of the air flow rates of each room and continuous air flow control according to demand in meeting rooms. The ductwork is sized using low velocities (< 1200 fpm), taking into account the predicted max. flow rate in order to minimize pressure losses within the zone and to maintain the desired air flow accuracy and meet cooling capacity requirements. Ductwork balancing is not needed in constant-pressure duct systems when unitary airflow rates are adjusted (e.g., for office room space changes). Even constant airflow rates of office rooms can be integrated into the same ductwork as variable air flow rate control for meeting rooms. Typically, the use of units that are similar (in length or nozzle type), along with individual adjustment of airflow rates, allows effective commissioning of the system.
Fan pressure control Fan speed control is typically used when variable flow is required. In small and symmetric low-velocity ductwork, the need for zone dampers is not evident, but larger duct systems shall be divided into sections, where duct pressure is kept constant by means of zone dampers. Adaptation to the variable operation conditions of a
variable flow system can be realized with variable-speed drives controlled by frequency converters. The target is to maintain a duct pressure level that is as low as possible in order to save on fan power consumption. The pressure controller maintains a constant or optimized pressure level in the ductwork using a pressure sensor as feedback. The sensor measures the static pressure relative to prevailing pressure in the building.
The pressure sensors positioning is crucial for reliable operation and fan power consumption. Basic steps in positioning of the pressure sensor: Simulate the ductwork, and determine which index branch requires the highest pressure in the system Establish the location in the area at 2/3 3/4 of the distance between the terminal branch and the fan Study whether the set point pressure level would satisfy the demand in other branches In cases where no index duct section can be determined, multiple sensors should be used. The sensor with the actual highest demand provides the decisive feedback. Constant-pressure zones The accuracy of realized airflow rates and cooling capacities requires duct pressure that varies only slightly in the ductwork. Acceptable deviation of the target pressure level at the room branch duct is 0.04 0.08 in WC in order to achieve airflow rate inaccuracy of less than 10%. The practical zone size is dependent on: Ventilation rates, in cfm/ft2 Diversity of occupancy in meeting rooms The space available for ducts Practical duct dimensions The space layout plan Operation hour prediction for the spaces Supply and exhaust air arrangements In cases where the zone size is too great, the following problems can occur: Deviation from target air flow rates and cooling/ heating capacities Imbalance between supply and exhaust air Eventual noise problems Zone dampers allow different operations hours when, e.g., working hours in an office building vary between sections of the building. Zone size, in ft2, estimated according to ventilation rates
Ventilation rate Offices cfm/ft2 0.22 0.33 0.44 Meeting rooms cfm/ft2 0.9 0.9 0.9 Duct size D 16 in Percentage of meeting rooms 10% 6245 4630 3660 30% 4300 3600 3120 Duct size D 20 in Percentage of meeting rooms 10% 9740 7265 5760 30% 6675 5650 4900
A rough estimate of a typical zone size (in ft2), as presented in the table below, can be made on the basis of: Ventilation rates in offices and meeting rooms, in cfm per square foot Reservation for meeting rooms that are fully occupied simultaneously, as a percentage of zone size Max. circular duct size of the branch duct, in inches Ideally, the pressure sensor in a constant-pressure zone is in the middle of the zone in the supply duct. It is beneficial to use the same duct size, in order to benefit the static-pressure regain in the main branch duct. In the exhaust duct, the pressure sensor should be at the end of the main branch duct when under-pressure operation in the building is desired in a fully ducted exhaust system; otherwise, the sensor can be positioned in the middle of the ductwork. With common exhaust tracks the supply duct airflow rate, the supply/exhaust airflow rate balance can be maintained accurately.
Zone balance arrangements When in the zone there are both units with constant and units with variable flows, the exhaust is liable to pressure deviations due to higher pressure losses in the main branch duct and lack of regaining static pressure. The air flow balance in spaces in meeting rooms with variable flow can be realized in different ways: Ducted exhaust using a variable flow control damper Continuous balanced ducted exhaust for constant flow Transfer air via a grille to the corridor Common zone exhaust tracking the variable common supply airflow Transfer air via a grille to the corridor Common zone exhaust tracking the common variable supply flow
The common exhaust can take care of the air exhaust of meeting rooms and eventual open office areas.
Combination of ducted constant airflow exhaust and variable transfer to common exhaust.
Selection of active chilled beam air arrangements Active chilled beams should be positioned above workspaces to ensure comfortable velocity conditions. If the chilled beam is positioned close to a wall, an asymmetrical throw pattern is recommended. Minimum installation distances from walls and between parallel chilled beams are presented in the product data sheets. Exhaust air units have minor importance to the solutions operation.
Bi-directional air supply Perpendicular to exterior wall in offices (preferable), above the work area Parallel to exterior wall above work area Perimeter installation, with uni-directional supply Corridor installation limited application, depending on work area location and providing bi-directional supply horizontally and downward Uni-directional air supply Hotel guest rooms preferably above bed (above window as another option) Patient ward rooms preferably above bed either along side walls or parallel to exterior walls
Definition of design conditions and operation parameters Ventilation rates in spaces as rate per floor area (cfm/ft2) Ventilation rate in spaces as rate per person (cfm/ person) Cooling capacity demand in spaces, in Btuh/ft2, and actual breakdown of loads Heating capacity demand in spaces, in Btuh/ft2, and actual breakdown of loads Model rooms and operational parameters Room temperature Supply air temperature Water inlet temperature Target duct pressure level Target water flow rate
Verification of target design values with full-scale mock-up and CFD simulation Typical input values and operation ranges Room temperature for cooling Room temperature for heating Supply air temperature for cooling Supply air temperature for heating Water inlet temperature for cooling Water inlet temperature for heating Target duct pressure level for cooling Target water flow rate for cooling Target water flow rate for heating Outdoor air flow rate per unit floor area Outdoor air flow rate over effective length Cooling capacity per unit floor area Cooling capacity / beams effective length Heating capacity per unit floor area Heating capacity / beams effective length Comfort / PMV Draught rate (DR) Average room air velocity
(extreme target values in brackets) 73 77 F 68 72 F 61 66 F 61 66 F 57 61 F 95 113 F 0.3 0.5 inWC 0.32 1.6 gpm 0.16 0.65 gpm Offices: 0.33 0.55 cfm/ft2, meeting rooms: 0.33 0.9 (1.1) cfm/ft2 3.6 ... 9 cfm/ft 25 (38) Btuh/ft2 250 (400) Btuh/ft 4 (19) Btuh/ft2 150 (250) Btuh/ft -0.5 ... +0.5 < 15% Cooling: 45 fpm Heating: 35 fpm
1. Design data in cooling Insert the supply air flow rate and temperature 1, 5 3 2 Specify the temperature difference between the inlet and outlet water of the beam, or, optionally, insert the inlet water temperature and target water flow rate. Calculate the coil capacity using HIT Design, and 4, 6 compare the coil capacity against the requirement. Note the capacities transferred by the coil and primary air. 2. Chilled beam location and velocity control adjustment The location and number of chilled beams are specified (also, asymmetric positioning is possible). The HVC positions are set to allow adjusting the throw pattern in the space and providing the
Design data window in Halton HIT Design selection.
required velocity conditions in the occupied zone. To provide adaptability to load variations, use velocity control (HVC) position 2 (normal position). 3. Air quality control adjustment Set the HAQ airflow rate to match the required room airflow rate. HAQ control can be used to adjust the airflow rate at a specified duct pressure level. 4. Space results / unit performance Check the operation parameters against system operation conditions to verify that the operation parameters correspond to those of the system. 5. Design data in heating Analysis is as in the cooling case. 6. Space results / unit performance in heating
Room dimensions, occupied zone, and design criteria are specified in the Room window in Halton HIT Design.
Product selection
25
also that the predicted room conditions are acceptable, providing efficient air distribution: Supply air throw pattern and room air velocities (HVC position as in cooling) Supply jet adequately reaching occupied zone level Flow water temperature within recommended range Heating capacity Impact of the HVC arrangement Impact of the HAQ arrangement Study optional room modules Unit pressure drop (keep at the same level as
vmax in occupied zone: v3=0.15 m/s v3(dt=0)=0.10 m/s Heat sources and their location may influence to the velocity and direction of the jet. vlim = 0.20 m/s
v3
4.0 m
before) Operation with optional room cooling load levels / room usage Impact of HVC in other positions (1 and 3) Impact of the HAQ arrangement Operation in optional room module configurations If targets for indoor climate condition are not met, change the length and/or beam properties, or even the beam type
Study the supply air throw pattern properties and room air velocities (in design case) Room air velocities in occupied zone within set limits (non-isothermal and isothermal cases) Temperature difference between air jet and room air Distance at which the jet detaches from the ceiling (Ld) Pressure loss lower than the available pressure in the duct (check that the noise level is within the limits set) Adjustability of the air flow rate In cases involving several units; check the impact of jet interaction on occupied zone boundary velocities (refer to Lmin in the leaflet's quick selection table).
v3
4.0 m 4.2 m
Air flow measurement can be implemented accurately by measuring the chamber pressure of the chilled beam.
Adjustment and balancing methods Traditional Proper operation conditions for chilled beams are ensured by adjustment of airflow and water flow rates. Airflow rates can be adjusted by balancing the ductwork by means of zone balancing dampers and the balancing damper of each chilled beam. The balancing damper can be integrated into the chilled beam or into the connecting branch. K factors and safety distances are presented in the HIT Design software package. Airflow measurement can be implemented accurately by measuring the chamber pressure of the chilled beam. Also, system-powered self-balancing dampers can be used. A self-balancing damper increases the total pressure drop to 0.16 0.6 inWC. Additionally, in large systems, differential pressure Water flow rates can be adjusted via zone balancing valves and the balancing valve of each chilled beam. valves in the pipework zones may be needed to ensure appropriate pressure conditions. Even constant airflow rates of office rooms can be integrated into the same ductwork as variable air flow rate control for meeting rooms. Water flow rates can be controlled using an automatic flow limiter and combined control valve for each chilled beam, enabling individual changes in water flow rates without the need for balancing. Halton Adaptable In constant-pressure zones, the unitary airflow rate adjustment does not affect the airflow rates of other chilled beams. Commissioning can be implemented very effectively. Furthermore, balancing is not needed when unitary airflow rates are adjusted, e.g., for office room space changes.
Shut-off valve
Balancing valve
Room control sequences Room thermal conditions typically are controlled by adjusting hot and chilled water flow rates in each chilled beam by means of two-way valves. Control can be based on on/off, pulse-width-modulated (PWM), proportional, or proportional integral control. Demand-based control is based on remotely set set points determined by, e.g., schedulers, and settings can be adjusted locally by users according to their demands or by occupancy mode as detected by occupancy sensors. In meeting and team rooms, traditional temperature control can be complemented with an additional sequence for increasing outdoor airflow rate (Halton Air Quality control). This function responds rapidly to varying ventilation requirements. Proper heating operation can be ensured by using a combination of room and supply air temperature control in order to optimize the supplied air temperature to avoid an excessive vertical room temperature gradient.
Control sequence for heating and cooling.
Condensation prevention can be arranged in two stages: System flow water temperature control based on room air dew point calculation for critical locations. Locally in the room, using condensate detection to close the chilled water valve.
Room control applications Room control can be realized on the basis of functional requirements and the desired flexibility level using: A self-powered standalone controller An electric standalone controller A traditional communicative controller A temperature sensor, typically located in the wall-mounted user panel The control valve and actuator types are selected to match the required water flow rates and control sequences. The power supply (24 / 230 VAC) for controller, actuators, and sensors is supplied on the basis of the units selected.
Case 1. Air velocities (fpm) in the occupied zone with Halton Velocity Control in full position.
Case 1. Air velocities (m/s) in the occupied zone with Halton Velocity Control on in throttle position.
Case 1
20 % WP1 WP2 10 %
Chilled beams are installed perpendicularly to the external wall. Velocity conditions are presented with a cooling capacity of 16 Btuh/ft2 in two different cases: Halton Velocity Control in positions 3 and 1. Room air velocities were lower when induction through beams was lower, even though the cooling capacity was the same. The primary airflow rate was the same in both cases, and compensating cooling capacity was provided by increasing the water flow rate.
HVC 3
HVC 1
WP2
Case 2 Human responses were studied with chilled beams installed parallel to the external wall and two persons occupying the room. The number of people sensing a draught was clearly
WP1
(by about 60%) reduced during the maximum cooling capacity period with HVC in the throttle position (1). While the person near the window surface (WP2) felt slightly warmer (PMV increased from 0.4 to 0.7) when HVC was
Case study
30
Room temperature, summer Room temperature, winter Water inlet temperature, cooling Target water flow rate Sound level Note * Note **
Separately for ventilation Supply air temperature Outdoor air flow rate/ floor area, 61 66 F
It is reasonable to study the room air velocity conditions carefully It is reasonable to study the thermal conditions carefully
Ventilation and air diffusion arrangement The supply airflow rate shall be high enough to remove internal humidity loads. Cooling using chilled beams Required cooling capacities should be no more than 19 25 Btuh/ft . With well-dimensioned integrated
2
occupied zone in all seasons (winter, summer, and intermediate season) taken into account. The flow water temperature (typically above 57F) must be sufficiently high to avoid condensation in all operation conditions. If necessary, the inlet water temperature may be adjusted to compensate for outdoor or indoor conditions. A condensation sensor should be located in each zone. Water flow rates and pressure drops in chilled beams should be in line with chilled water pipework design and pumping cost target levels.
be realised. Thermal properties of the external walls and window construction should be reasonable. Airtight windows with effective solar shading are used. The cooling capacity of passive chilled beams is typically 150 250 Btuh/ft to avoid draughts in the occupied zone, especially underneath the unit. Operation shall be designed with conditions in the
Passive chilled beams installed in a suspended ceiling always require sufficiently large openings in the ceiling for the induced room air path. Location of chilled beams shall respect the minimum distances from walls and ceiling presented in the section Passive chilled beam orientation and ventilation arrangements.
Suitability for the lighting fixture locations Flexibility for layout changes Minimum distance between parallel beams Minimum distance between chilled beam and wall/ ceiling
Passive chilled beam location Chilled beam units shall be installed respecting minimum recommended distances from walls and ceiling in order to ensure effective convection and proper operating conditions:
Minimum distance between chilled beam units of L, to ensure effective operation: L = min. 3 x W When a passive chilled beam is installed above a perforated or grid ceiling, the following minimum distances should be respected: H3 = min. 1 in The open area percentage (OAP) of the suspended ceiling shall be sufficiently high to ensure proper functioning of the chilled beam. The minimum percentage of open area for perforation is 25%. The minimum hole diameter is 1/8 in. Side panel extensions can be used to improve buoyancy effect and thus cooling capacity.
Hsk, Correction factor, in Passive chilled beam installed above a perforated or grid ceiling.
Use HIT Design for calculation of cooling capacity, taking installation above the perforated ceiling with or without side panel extensions into account. Exhaust air unit location
4 6 12 16
In cases where chilled beams are installed above a suspended ceiling, exhaust units should not be installed above the suspended ceiling. Otherwise, exhaust unit position is of minor importance in the installation.
Definition of design conditions and operation parameters Cooling capacity demand in spaces, in Btuh/ft2, and actual breakdown of loads Heating capacity demand in spaces, in Btuh/ft2, and actual breakdown of loads Ventilation arrangement Diffuser type, size, and number Ventilation rates in spaces as rate per floor area, in cfm/ft2 Ventilation rate in spaces as rate per person, in cfm/
Verification of target design values with full-scale mock-up and CFD simulation.
person Model rooms and operational parameters Room temperature Supply air temperature Water inlet temperature Target duct pressure level Target water flow rate Maximum sound pressure level
Typical input values and operation ranges Room temperature for cooling Water inlet temperature for cooling Target water flow rate for cooling Cooling capacity per unit floor area Cooling capacity / effective beam length Comfort / PMV Draught rate (DR) Local mean room air velocity
(extreme target values in brackets) 73 77 F 57 61 F 0.32 1.6 gpm 25 (38) Btuh/ft2 250 (400) Btuh/ft -0.5 ... +0.5 < 15% Cooling: 45 fpm Heating: 35 fpm
8 x 13 x 9 104 ft2 75 F 42 cfm 64F 22 Btuh/ft2 2700 Btuh 491 Btuh 1931 Btuh DT = 14 degF 159 Btuh/ft
Water flow rate: 1.27 gpm Coil width (in) 12.4 18.3 24.2 12.4 18.3 24.2
Difference between room air and water mean temperatures, degF 11 91 143 190 108 177 225 13 116 182 241 135 220 280 14 132 211 283 155 258 330 15 147 234 303 170 284 364 16 163 253 322 186 310 395 17 176 279 362 203 335 426 18 190 301 401 217 358 457 20 232 335 465 253 418 532
Chilled beam APA cooling capacity, in watts per metre of effective length for water flow rate 1.27 gpm
CPA passive chilled beam quick-selection Cooling capacity over unit length (W/m) presented for water flow rate qmw = 1.27 gpm. Estimate the temperature rise in the chilled beam (typically 2 5 degF), and calculate the temperature difference between room air and water mean temperature. Check the temperature difference with the HIT Design software. Temperature difference Tr - (Tw1 + Tw2)/2, degF Where Tr Tw1 Tw2 Room temperature, F Water flow temperature, F Water return temperature, F
Water flow rate qmw, gpm 0.024 0.79 0.32 0.83 0.40 0.86 0.48 0.88 0.55 0.91 0.63 0.92 0.71 0.94 0.79 0.96 0.87 0.97 0.95 0.98 1.27 1
Correction factor of cooling capacities for water flow rates deviating from 1.27 gpm flow rate.
Selection Calculate the cooling and heating capacity of the selected chilled beam units by studying chilled beam performance in selected model rooms with desired operation parameters, using Halton HIT Design.
1. Design data in cooling Specify the temperature difference between the 1 2 inlet and outlet water of the beam or, optionally, insert the inlet water temperature and target water flow rate. Calculate the coil capacity using HIT Design, and compare the coil capacity against the requirement. 3 You can also insert the supply air flow rate and temperature for total cooling capacity calculation. 2. Chilled beam location and velocity control adjustment The location and number of chilled beams are specified (also, asymmetric positioning is possible). You can also add a person for evaluating the air velocity locally
Design Data window in Halton HIT Design selection.
directly below the chilled beam in the vicinity of the beam at floor level further from the chilled beam at floor level
3. Space results / unit performance Check operation parameters against system operation conditions to verify that the operation parameters respond to those of the system, as in the cooling case.
Room dimensions, the occupied zone, and design criteria are specified in the Room window in Halton HIT Design.
Cooling Room: Room size: Occupied zone: Room air: Heat gain: Perforated ceiling: Installation height: Inlet water temperature: Outlet water temperature: Water flow rate: Coil capacity: Water pressure drop: Velocity point v T
CPA-100-3900-315-1
Supply air flow rate 2.5 x 4.0 x 2.8 m h=1.8 m / dw=0.5 m 24.0 C / 50 % 700 W 2.70 m 15.0 C 16.7 C 0.080 kg/s 575 W 155 W/m 5.6 kPa vop ~0.15 m/s Dew point temperature: Velocity control: Supply air temperature: Jet outlet temperature: Primary air capacity: Total pressure drop: Total sound pressure level: Total cooling capacity: 20 l/s 2.0 l/(sm2 ) 18.0 C 21.4 C 143 W 718 W 72 W/m2 12.9 C -
vop
2.5 m
Study the velocities of the convective plume entering the occupied zones and room air velocities Plume velocities entering the occupied zones (in the design case) Room air velocities in the occupied zone Temperature difference between the plume and ambient room air Check the interaction of the falling convective plume of a chilled beam and supply air throw pattern Simultaneously with the performance values, verify that the predicted room conditions are acceptable, providing efficient air distribution. Supply jet adequately reaching the occupied zone level Supply air that is not directed directly to chilled beam air circulation
If indoor climate conditions targets are not met, then change the beam length or number of beams and/or beam properties or even beam type and diffuser type and/or location Study optional room modules Water flow rate (keep at the same level as before) Operation at optional room cooling load levels / room usage
Interaction of convective plumes of a chilled beam and a stationary person Note that the rising convective plume of a stationary
person affects the flow pattern of a chilled beam and that the prevailing velocities above the person are lower than in undisturbed flow created by a chilled beam.
Cooling Room: Room size: Occupied zone: Room air: Heat gain: Perforated ceiling: Installation height: Inlet water temperature: Outlet water temperature: Water flow rate: Coil capacity: Water pressure drop: Velocity point v T
CPA-100-3900-315-1
Supply air flow rate 2.5 x 4.0 x 2.8 m h=1.8 m / dw=0.5 m 24.0 C / 50 % 700 W 2.70 m 15.0 C 16.7 C 0.080 kg/s 575 W 155 W/m 5.6 kPa v3 ~0.25 m/s -2.6 C vop ~0.15 m/s Dew point temperature: Velocity control: Supply air temperature: Jet outlet temperature: Primary air capacity: Total pressure drop: Total sound pressure level: Total cooling capacity: 20 l/s 2.0 l/(sm2 ) 18.0 C 21.4 C 143 W 718 W 72 W/m2 12.9 C
2007.05
Cooling Room: Room size: Occupied zone: Room air: Heat gain: Perforated ceiling: Installation height: Inlet water temperature: Outlet water temperature: Water flow rate: Coil capacity: Water pressure drop: Velocity point v T
CPA-100-3900-315-1
Supply air flow rate 2.5 x 4.0 x 2.8 m h=1.8 m / dw=0.5 m 24.0 C / 50 % 700 W 2.70 m 15.0 C 16.7 C 0.080 kg/s 575 W 155 W/m 5.6 kPa v3 ~0.25 m/s -2.6 C vop ~0.05 m/s Dew point temperature: Velocity control: Supply air temperature: Jet outlet temperature: Primary air capacity: Total pressure drop: Total sound pressure level: Total cooling capacity: 20 l/s 2.0 l/(sm2 ) 18.0 C 21.4 C 143 W 718 W 72 W/m2 12.9 C -
2007.05
v3
v3
vop
vop
2.5 m
2.5 m
Adjustment and balancing methods Proper operation conditions for chilled beams are ensured by correct water flow rates. Water flow rates can be adjusted via zone balancing valves and the balancing valve of each chilled beam.
Room control Room thermal conditions typically are controlled by adjusting hot and chilled water flow rates in each chilled beam by means of two-way valves. Control can be based on on/off, pulse-width-modulated (PWM), proportional, or proportional integral control.
Water flow rates can also be controlled using an automatic flow limiter and combined control valve for each chilled beam, enabling individual changes in water flow rates without the need for balancing. Additionally, in large systems, differential pressure valves in the pipework zones may be needed to ensure proper pressure conditions.
Demand-based control is based on remotely set setpoints determined by, e.g., schedulers, and settings can be adjusted locally by users according to their demands or by occupancy mode as detected by occupancy sensors.
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Detectors Occupancy sensors allowing for demand-based ventilation and other occupancy-related features, as well as daylight sensors and smoke detectors, can be integrated into the chilled beam.
Controls Chilled beam delivery can include integrated two-way control valves with actuators and condensation sensors. When necessary, the beam structure can also include a room controller and the associated temperature sensor
Space for sprinklers National building codes typically require sprinkler installations to be carried out on the site. However, the sprinkler pipes can be attached above the beams and the pipe connections for individual sprinkler nozzles, to an accessory space in the middle of the beam.
Public address loudspeakers Public announcements or background music can be provided through built-in pre-wired speakers.
Cable shelves Cables for various services can be laid on cable shelves, which can be integrated in the chilled beam design in order to complete the elegant installation.
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