Patent Application
20240027095
Embodiments relate to a variable air volume (VAV) swirl diffuser, in particular, but not exclusively, for use as a ceiling swirl diffuser with integrated VAV terminal unit to maintain control of the room air temperature and/or indoor air quality (IAQ), as part of an installed air delivery system.
Many buildings have air conditioning or ventilation systems that distribute air throughout the building through ducts connected to diffusers. The diffusers distribute supply air, usually heated or cooled, into the spaces to be air conditioned or ventilated. The supply air may pass through VAV terminal units that each vary the supply air supplied to a group of several diffusers, so as to vary the cooling or heating capacity provided to the thermal zone served by that group of diffusers. Air handler fan speed may be controlled to a static pressure setpoint upstream of the VAV terminal units, and the static pressure setpoint may be reset as a function of thermal load.
Standard ceiling diffusers in buildings are usually designed to discharge air horizontally above head height, with a throw that substantially covers the footprint of the space served by each diffuser. For such standard diffusers that have fixed horizontal discharge, high airflow rates generally increase throw, often producing over-throw, which may cause draughts where air streams from adjacent diffusers clash or where air streams hit obstructions such as walls or bulkheads. In contrast, low airflow rates generally produce reduced throw, often causing zones of stagnation and of increased air temperature beyond the throw of the diffuser, whilst cold spots or even draughts may occur close to or beneath each diffuser due to dumping of cold, dense supply air into the occupancy space. In VAV cooling applications, such standard ceiling diffusers may, therefore, produce discomfort whenever overthrow or underthrow occurs due to the discharge of high or low airflow rates when thermal loads are high or low, respectively.
Ceiling swirl diffusers generally provide higher levels of thermal comfort and efficiency, especially in VAV applications, than four-way blow ceiling diffusers or similar low induction air diffusion devices. The highly inductive swirl discharge of ceiling swirl diffusers draws in and mixes large quantities of room air into the discharged supply air stream, rapidly breaking down the supply-to-room temperature differential to provide more uniform temperature distribution throughout the occupancy space whilst simultaneously bringing about rapid discharge velocity decay. This reduces draught risk at high airflow rates, improving thermal comfort in the space. The high induction characteristics also increase the effective air changes per hour in the space, reducing the risk of stagnation at lower airflow rates, thereby further improving thermal comfort. ADPI (Air Diffusion Performance Index) values in excess of 90%, i.e. of enhanced comfort, are readily achieved.
Ceiling swirl diffusers also provide potential to achieve fan energy savings by allowing supply air temperature to be reduced to a level that would otherwise cause dumping. This is because high induction brings about strong dilution of the supply air stream with room air, thereby reducing the density difference between the supply and room air. Even so, VAV turndown to approximately 25 to 30 percent of the maximum airflow rate for a sound pressure level of NC 30, and a minimum specific airflow rate of approximately 1 L/s/m2 typically define the lower operating limits for premium fixed vane ceiling swirl diffuser systems operating in cooling mode, especially if the temperature differential between supply and room air is high (often as high as 16 K). As a result, in order to prevent dumping and avoid stagnation, the minimum airflow rate that a VAV system may be turned down to is often higher than the airflow rate required to satisfy thermal load or indoor air quality (IAQ) criteria. This causes fan energy to be wasted, as it results in unnecessarily high airflow rates when thermal loads are low. It also causes discomfort due to overcooling the space unless even more energy is wasted reheating the supply air before it is discharged. Alternatively, if lower airflow rates are nevertheless used then reheat of the supply air may still be required to prevent dumping, again wasting energy.
In order to increase the range of thermal loads that can be dealt with by each VAV system, and to reduce the minimum permissible airflow rate of the diffusers and the minimum specific airflow rate of the diffuser system, the design of a VAV terminal unit with associated diffusers may be replaced with a system design of actuator driven variable geometry VAV diffusers. Such diffusers are each equipped with a VAV damper that has variable geometry discharge that changes the effective discharge aperture of the diffuser, or changes the aperture directly upstream of the fixed vanes of the diffuser, so that VAV airflow rate adjustment may be achieved from each diffuser whilst maintaining a substantially constant discharge velocity when the diffuser is operated at a substantially constant static pressure. Such operation limits the extent to which throw is reduced as the diffuser airflow rate is throttled, allowing for a greater degree of throttling, which potentially improves comfort by reducing the risk of overcooling and dumping as well as of stagnation in the space, whilst also reducing energy consumption by reducing both fan energy and reheat requirements. This solution additionally enables each diffuser to be controlled as an independent VAV terminal, rather than as part of a larger VAV group, thereby further improving thermal comfort and energy savings by reducing the size and increasing the number of thermal zones in the system, as each diffuser may be an independent thermal zone.
Adjustable VAV dampers in such variable geometry VAV diffusers are typically regulated by means of thermally or electrically powered actuators. Hybrid actuator solutions also exist comprising thermal actuators with electrically heated jackets to allow the actuator to respond to a heat output modulated by an electric controller, as do pneumatically operated actuators, especially for explosive environments.
Thermally powered actuators convert temperature change into an axial push/pull motion of a piston via a mechanical force exerted onto the piston by a phase change expansion material encased in a thermally conductive housing. Advantageously, thermal actuators require no external power source or controls, eliminating the need for power supply and wiring, as they are entirely thermally driven, and are generally maintenance free for about ten years.
On the other hand, an electrical actuator generally includes a temperature sensor connected to a computing device which operates an electrically powered actuator (e.g. an electric motor) when certain predetermined temperatures are sensed. It is to be realised therefore that the term ‘thermal actuator’ as used herein includes a sensor and actuator in one since these devices react mechanically to changes in temperature.
For cooling-only applications, only one thermal actuator is typically required to sense room air temperature. The room air temperature setpoint is usually manually adjustable in a range from 20° C. to 26° C., or thereabouts. A supply air jet within a housing located behind the diffuser face plate typically draws in room air through a room air inlet and across the thermal actuator by entrainment so that the thermal actuator, which is hidden from view, responds to the room air temperature. The mixture of supply air and entrained room air is then discharged back into the room well clear of the room air inlet.
For combined cooling/heating applications, two or more thermal actuators are required: at least one to respond to room air temperature as described above, and at least one other in communication with the supply air to engage cooling or heating mode operation in response to the supply air temperature.
Electrically powered actuators are typically powered by a low voltage external power supply, such as 24 V, which may be daisy-chained from one diffuser to the next. Each diffuser is equipped with an electrically operated actuator (typically a brushless DC motor or stepper motor) that drives the VAV damper. The diffusers, which usually include a PC board, may communicate with one another or with remote controls or sensors via comms wiring or wirelessly, such as via Wifi. Typically, comms wiring is used, and is often combined with the power supply wiring into a common cable. While more expensive than a thermal actuator solution, the electric actuator diffusers allow for improved and more energy efficient operation, such as through PI (proportional-integral) or adaptive VAV damper control, global adjustment of cooling and heating setpoints as a function of outdoor temperature or other relevant parameters, minimum airflow rate adjustments based on indoor air quality, operation of diffusers based on occupancy, “voting” by the diffusers for an integrated determination of mechanical plant cooling/heating mode rather than this being entirely independent of the diffusers, and so on.
Electric actuator variable geometry VAV diffusers may house some electronic sensors and may include sensors located remotely. For example, remote sensors may be located in a casing at chest height on a wall in the room and may include a room air temperature sensor with setpoint adjustment buttons, a humidity sensor, a VOC or CO2 sensor to measure room indoor air quality, and a PIR sensor to determine whether the room is occupied. A supply air temperature sensor may be located in the diffuser to determine cooling/heating operation. The diffuser airflow rate may be determined by means of a pressure sensor in the diffuser that measures the total or dynamic air pressure through the diffuser spigot, or via one or more hot wire anemometer sensors in the diffuser that measure air velocity. This allows VAV airflow control independent of system static pressure to be achieved, further improving temperature control. It also facilitates ease of commissioning. A PIR sensor may optionally be located in the diffuser face to determine whether the space is occupied, and an induction system that draws in room air may additionally be incorporated in the diffuser to allow room air temperature to be measured, thereby, in most cases, dispensing with the need for remote sensors unless indoor air quality or humidity are to be measured, as electric actuator variable geometry VAV diffusers of the current art do not have sufficient space to house these sensors. The elimination of remote sensors is often sought after, as this facilitates ease of tenancy fit-out changes (no cabling to reroute) or reduces maintenance requirements (no need to replace sensor batteries if communications are wireless or to deal with wireless interference cutting communications).
The most widely used thermal or electric variable geometry VAV diffusers have a square face designed to fit into a standard ceiling grid (typically approximately 600 mm×600 mm square). Visible parts are largely made of powder coated metal. A top-entry spigot, for connection to a supply duct, is usually located at the apex of a hood shaped housing that extends down to the perimeter of the diffuser face. Alternatively, a connection box with side-entry spigot may be placed over the diffuser, typically sealing to the back of the diffuser housing outer edges, in which case supply air flows from the supply air duct via the side-entry spigot into the connection box, and then into the top-entry spigot of the diffuser. An actuator driven, centrally located and substantially horizontally aligned damper plate or damper vane array is located beneath the diffuser housing. The actuator drives the damper plate or vane array to adjust the vertical aperture between the damper plate or vane array and the diffuser housing to meter the airflow at substantially constant velocity (for a given supply air pressure) for discharge through the diffuser face. When viewed in plan-view, the most common arrangement is that a broad, continuous, square or round, discharge slot surrounding a large square or round face plate, called a plaque, discharges the supply air directly towards the diffuser perimeter, for the supply air stream to then attach, via Coanda effect suction, to the ceiling and spread in a substantially 360° pattern away from the diffuser, without dumping. The VAV actuator(s), damper mechanism and induction system (if present) are substantially located above the large plaque which screens these components and is usually removable for access to them. The substantially horizontal damper plate or vane array, located above the plane of the plaque, obstructs, at least in part, the air path to the continuous discharge slot.
Instead of discharge through a continuous discharge slot, a flat face swirl diffuser, comprising a round array of substantially radially aligned swirl vanes centred about a round hub, is sometimes used. The hub replaces the plaque of the non-swirl diffuser variant but is generally somewhat smaller so that the active area of the swirl vanes is not too restricted. The VAV actuator(s), damper mechanism and induction system (when used) are substantially located behind the hub. The damper plate or vane array, located above the plane of the diffuser face, obstructs, at least in part, the air path to the swirl vanes. The plurality of swirl vanes is typically folded or pressed in a substantially radial pattern, with round outer boundary, into the metal face of the diffuser. These vanes break the discharged supply air up into a multitude of air streams that are each discharged in a direction that, in plan-view, is substantially perpendicular to the radial alignment of the two directly adjacent swirl vanes. These air streams attach to the ceiling and spread in a substantially 360° pattern away from the diffuser.
U.S. Pat. Nos. 4,523,713, 6,857,577 B2 and 6,176,777 B1 describe widely used actuator driven variable geometry VAV diffusers that have a continuous discharge slot surrounding a plaque. U.S. Pat. Nos. 4,231,513 and 10,337,760 include embodiments that describe variable geometry VAV diffusers with swirl diffuser discharge.
Whilst offering many advantages, actuator driven variable geometry VAV diffusers of the prior art suffer from numerous shortcomings, which it may be desirable to overcome.
Most manufacturers of such prior art actuator driven variable geometry VAV diffusers recommend that the AHU (air handling unit), supply air fan and associated branch duct dampers be controlled to maintain a predetermined static pressure setpoint (which may be varied during operation) at a location approximately two thirds along the active length of the branch duct to which the diffusers are connected, the active length being the length between the first and last diffuser take-offs on that branch duct.
Multiple such diffusers are typically connected via flexible ducts to one or more branch ducts. Each diffuser has a minimum permissible static pressure, which is typically 12 Pa, at which its induction system (if present) can operate and at which the diffuser can operate in a stable fashion without dumping. Each diffuser also has a maximum recommended static pressure, typically of 60 Pa, to prevent excessive airflow noise generation.
Due to additional duct pressure losses (e.g. in the flexible ducts connected to the diffusers, from balancing dampers serving individual diffusers, or caused by changing pressure distribution in the entire duct system as diffuser dampers open and close) such a static pressure measurement point at a single and remote point in a duct cannot be representative of the actual static pressure at each diffuser. Consequently, some diffusers may well operate at less than their minimum permissible static pressure, leading to compromised performance and possible dumping, or a safety factor may be added, in which case the entire system will run at an excessive air pressure, thereby wasting energy and generating excessive noise. Moreover, if the single duct static pressure sensor were to fail then static pressure control in that duct will be lost, potentially causing the entire system to fail.
In the prior art, if the airflow rate of each diffuser is to be determined then each diffuser is typically equipped with several velocity sensors or with a pressure sensor (measuring dynamic or total pressure) connected to an array of pressure measuring points. Several velocity sensors or an array of pressure points are required in order to average out asymmetric air velocity distribution in the diffuser spigot due to bends in the duct directly upstream of the diffuser. Even so, both solutions tend to be inaccurate, especially at higher airflow rates, due to the asymmetric and often turbulent on-flow conditions into each diffuser spigot. Furthermore, dynamic pressure sensors become increasingly inaccurate when airflow rates are low, due to dynamic pressure being a function of air velocity squared, and accurate velocity sensors are extremely expensive.
In order to minimise HVAC costs, it is often desirable to discharge as much air per diffuser as possible without creating draughts, excessive airflow noise, or requiring too much fan pressure. For the prior art actuator driven variable geometry VAV diffusers described in the above patents, the top-entry spigot configuration necessitates the diffuser housing to be low in profile to allow installation into ceiling voids of restricted height. The substantially horizontally orientated damper plate or vane array imparts abrupt changes in direction to the air path, has a restricted discharge aperture due to the low-profile diffuser housing, and at least partially obstructs the continuous discharge slot. This increases the pressure loss of the diffuser, thereby increasing system fan energy requirements.
Flexible ducting typically connected to the top-entry diffuser spigots typically rests on the adjacent ceiling tiles before “goose-necking” through an almost 90-degree upward curve and then a more than 90-degree downward curve to the connection point on the diffuser spigot. These abrupt and opposite bends strongly increase duct pressure drop and cause strongly asymmetric airflow onto the diffuser spigot, resulting in excessive noise and asymmetric discharge from the diffuser face. Additionally, if the diffuser is equipped with a total or dynamic air pressure sensor in the diffuser spigot to determine the airflow rate, then the accuracy of these measurements is severely compromised, resulting in incorrect airflow control.
While one of the key purposes of variable geometry VAV discharge is to target substantially constant throw across a broad VAV range of operation, this, in fact, is not achieved, as throw is proportional to the square root of the product of volume flow rate and discharge velocity, and variable geometry VAV diffusers of the prior art vary the volume flow rate of the discharged airstream at a substantially constant velocity (for a given supply air static pressure) of the discharged airstream, thereby affecting throw substantially as a function of the square root of the airflow rate. Consequently, as the airflow rate discharged by actuator driven variable geometry VAV diffusers of the prior art decreases, so too does the throw, and hence the threat of stagnation and heat build-up further afield increases, compromising thermal comfort and indoor air quality, or closer spacing between diffusers is required by increasing the number of diffusers, which increases capital cost.
As the discharge pattern from the broad and continuous discharge slot is not highly inductive, draughts occur, especially at higher airflow rates, and such discharge is generally not suitable for a supply air temperature of less than 12° C. This may cause discomfort and increases the system airflow rates necessary—and hence the number of diffusers required—to cool the space, increasing fan energy requirements.
The use of a swirl discharge face instead of a broad, continuous slot reduces draught risk and may allow lower supply air temperatures to be used but adds substantial further restrictions to the air path. Only a small percentage of the diffuser face is available to be fully active due to obstruction by the damper plate, and the airflow is further restricted by the additional abrupt changes in airflow direction that the swirl vanes impart. Diffuser airflow noise increases noticeably, the maximum permissible diffuser airflow rate drops substantially, and the maximum permissible operating pressure is significantly reduced in a bid to prevent excessive airflow noise. More diffusers are required to serve the space, adding to capital cost, a greater need for static regain duct design may be required to minimise pressure distribution variations in the duct system, adding to capital cost and often rendering such diffusers unsuitable for retrofit applications unless existing ducting is replaced, and the VAV operating range is reduced, increasing operating costs and compromising thermal comfort.
The ceiling void height in modern multi-storey buildings is extremely restricted in order to reduce the overall height of these buildings, to thereby reduce their overall construction costs. Diffusers with top-entry spigots require substantial ceiling void height for the supply air duct to be routed to approach from one side and then curve through at least 90 degrees to attach to the top-entry spigot. Even if the diffusers are equipped with a side-entry connection box, the connection box needs to be relatively high so that the supply air can easily flow from the connection box into the top-entry spigot of the diffuser. The higher the diffuser airflow rate the greater this height needs to be. The space requirements of diffusers with relatively large airflow rates are therefore often too high to fit into the ever more common restricted ceiling void spaces, requiring either more diffusers to be used, which increases capital cost, or resulting in excessively sharp or even kinked flexible duct bends onto the top of each diffuser, dramatically increasing pressure drop, noise and fan energy requirements.
New-build, multi-storey commercial buildings are initially air conditioned for the base building design, which consists largely of open-plan floor plates which ideally have a small number of ceiling diffusers each discharging a large air quantity across a large floor area. This helps minimise the base building HVAC costs. Once tenanted, tenancy fit-outs occur, in which parts of each floor are partitioned into offices, meeting rooms, etc, each of which is then typically conditioned by means of diffusers that often discharge relatively small air quantities (if the room served is small), while open-plan areas remain largely unchanged from the base-building installation. The larger airflow base building diffusers of the prior art that need to be replaced by counterparts suitable for smaller airflow rates generally cannot be repurposed for such smaller airflow rates, as their top-entry spigots are too large to connect to smaller ducts and their large damper system sizing is not able to provide proper VAV authority over smaller airflow rates. These extremely costly VAV diffusers of the prior art become superfluous, and effectively have to be thrown away to be replaced by additional, extremely costly, smaller airflow rate prior art VAV diffusers. This increases the HVAC costs of tenancy fit-outs.
Space availability beneath the damper plate or vane array of electric actuator variable geometry VAV diffusers of the prior art is extremely limited due to the restricted height of the low-profile diffuser housing and the space requirements of the damper motor and mechanism. There is generally insufficient space to fit more than the PC board, room temperature sensor and PIR sensor, and associated induction system without increasing diffuser height or throttling diffuser airflow. This is especially so if the diffuser has a swirl face as the induction system, including its inlet and outlet, must fully fit into and seal to the smaller sized hub of the swirl face. Consequently, remote sensors are still required to house bulky CO2, VOC and RH room air sensors. This adds to project costs and reduces flexibility for tenancy fit-outs.
Due to space constraints outlined above, the induction systems of prior art VAV diffusers are extremely restricted, especially in variable geometry VAV diffusers with swirl discharge. Their air inlets are under-sized and their induction chambers are short, resulting in a low induction ratio and weak secondary airflow from the room into the induction system. This not only causes a slow thermal response time to room temperature changes, but also leads to inaccurate steady state room temperature measurements as thermal bridging (especially from swirl vanes to the hub) can significantly affect the boundary layer air temperature beneath the hub as well as in and around the induction inlet unless a strong secondary airflow into the induction system is used to dilute this air with more representative room temperature air. The induction systems of such prior art diffusers are not able to generate such strong secondary airflow due to the space restrictions above the diffuser plaque or, in particular, the smaller sized swirl face hub. The accuracy of room air temperature sensing is compromised, resulting in poor indoor air temperature control, reduced comfort, and increased HVAC energy costs.
In order to somewhat boost secondary airflow into the induction system, relatively high primary airflow rates are sometimes used in actuator driven variable geometry VAV diffusers of the prior art. This limits the VAV range of operation, especially if the maximum airflow rate is low, leading to discomfort and energy wastage due to overcooling when thermal loads diminish.
Given that the diffuser induction systems operate continuously, energy is additionally wasted discharging primary cooled/heated airflow into spaces even when they have no air conditioning requirement, such as when the HVAC system is active but the diffusers in question serve spaces that are untenanted or that are unoccupied.
A diffuser unit for supplying air to a space, the diffuser unit comprising:
The damper apertures and damper doors may be configured and operable to maintain a substantially constant velocity or throw of air discharged from the air deflector.
The pressure plenum, damper compartment and or damper doors may comprise one or more surfaces configured to impart a tangential velocity to air flowing into the damper compartment. The surface may be angled.
In certain embodiments (e.g.
In such embodiments a constant velocity of air discharged from the outlet may be maintained, at least for a portion of possible positions of the damper doors.
In further embodiments (e.g.
The unit may be a ceiling diffuser unit adapted to be mounted to a ceiling defining the space. Alternatively, the diffuser unit may be adapted to be mounted at a location towards an upper part of the space. For example, the unit may, in certain embodiments, be suspended from a ceiling or roof and located above head-height.
The diffuser unit may have a perforated baffle plate associated with the air inlet of the pressure plenum.
The pressure plenum may be a connection box. The pressure plenum may have a low or substantially zero dynamic pressure relative to a duct connected to the air inlet of the pressure plenum.
The damper compartment may be radially symmetric.
The damper compartment may be frusto-conical.
Each damper door may be moved between an open position and a closed position.
One or more damper doors may comprise a vane extending tangentially to a surface of the damper compartment. Alternatively, or in addition, the damper compartment may have a plurality of edges defining the apertures, the damper compartment having vanes formed at the edges.
The vanes may extend away from an outer surface of the damper compartment (e.g.
The damper doors may be connected to a control mechanism. The control mechanism may be a sliding mechanism causing the damper doors to slide with respect to the compartment and thereby open and close the respective apertures.
There may be a single mechanism for all doors so that the position of each door relative to the corresponding aperture is the same for all damper doors.
The damper doors may be formed by a sheath which engages with, and slides relative to, the damper compartment.
Alternatively, a plurality of damper doors may each have a corresponding door control mechanism, each corresponding door control mechanism acting independently so the plurality of doors may selectively be moved relative to the corresponding aperture to open or close the aperture.
One or more damper doors may be mounted for pivoting movement about a respective axis relative to the damper compartment (e.g.
The axes of rotation of the damper doors may be vertical or may be inclined. Where the axes are vertical they may be orientated substantially normal to the plane of the discharge face of the diffuser unit. The axes may be orientated to be substantially coincident with the surface of a cylinder. Where the axes are inclined, the axes may be orientated to be substantially coincident with the surface of a cone.
The axes of rotation of the damper doors may be parallel to a diffuser centre-line or may be inclined thereto. Where the axes are parallel they may be orientated substantially normal to the plane of the discharge face of the diffuser unit. The axes may be orientated to be substantially coincident with the surface of a cylinder. Where the axes are inclined, the axes may be orientated to be substantially coincident with the surface of a cone.
The door may substantially provide a seal to the corresponding aperture when in the closed position.
Each door may have a trailing edge. The trailing edge may be formed with serrations. The serrations may be one or more of: saw-tooth, sinusoidal or irregular. The one or more doors may be formed from a perforated or porous material at the trailing edge.
The profile of the trailing edge may diverge from a profile of a portion of the damper door excluding the trailing edge. The damper door may comprise a sealing edge. The sealing edge may be located at, or proximate to, the trailing edge. The trailing edge may diverge from a tangent to a surface of the damper door at the sealing edge. The trailing edge may have an arcuate profile. The arc may extend towards the compartment.
The terms “leading” and “trailing” are used with reference to an airflow when the unit is in use, unless the context indicates otherwise.
The damper doors may comprise a respective surface upon which airflow impinges, wherein at least one of the surfaces is formed with one or more protrusions to reduce a noise generated by air flowing over the surface. The respective surfaces may form respective trailing edges. The respective surfaces may form respective sealing edges.
The shape of the protrusions may be in the form of one or more of: substantially planar, a sawtooth, rectangles, triangles, truncated triangles, substantially sinusoidal or irregular. The protrusions may protrude from the surface at an angle, which may be between 200 and 90°, or between 30° and 60°. A closest spacing between adjacent protrusions may be between 0.5 mm and 5 mm, or between 1 mm and 3 mm. The protrusions may have a width of between 1 mm and 2 mm, or between 3 mm and 10 mm. One or more damper doors may have a first set of protrusions with one of the aforementioned shapes and a second set of protrusions with another of the aforementioned shapes. The damper doors may have more than two sets of protrusions, each with different shapes.
The protrusions may be vortex generators. Further or alternative shapes of the protrusions may comprise a distorted pyramid with a triangular base, a blade shape or one or more hemispheres.
As well as, or in addition to protrusions formed at the surface of the damper door, the damper compartment may comprise one or more vanes formed at an edge defining an aperture.
The damper compartment may comprise an inlet surface for forming a seal with a corresponding door. The inlet surface may describe a rounded inlet upstream of a sealing site. The rounded inlet may have a radius between 5 mm and 30 mm, most preferably between 10 mm and 20 mm. The rounded inlet may help to reduce noise.
One or more doors may comprise a lock for locking a position of the door relative to the corresponding aperture. The lock may lock the door in a closed position. The lock may be manually operable and accessible through the discharge element.
The unit may comprise a first door type and a second door type. The first door type may be smaller than the second door type. A circumferential extent of the first door type may be less than a circumferential extent of the second door type. The unit may comprise a plurality of doors of the first door type and a plurality of doors of the second door type. Doors of the first door type may alternate with doors of the second door type through a circumference of the damper compartment. Alternatively, there may be twice as many doors of the second type than doors of the first type. There may be one or more sets of doors of the second type, each set comprising two or more doors of the second type. Each set of doors of the second type may alternate with doors of the first type through a circumference of the damper compartment.
At least one door may comprise a switch arranged to be activated when the door is in a fully closed position or in a fully open position. Alternatively, or in addition, the compartment may comprise a switch positioned to be activated by closure or full opening of at least one door. The switch may be activated by a door actuator. The switch, when activated may signal a zeroing of a position of the corresponding door. There may be a switch associated with each door.
The unit may comprise one or more blanking segments for obstructing a portion of airflow though the unit. The one or more blanking segments may be located to block the discharge element. There may be two blanking segments. Each segment may be shaped as a wedge. The wedge may be a 90° wedge. (
The damper apertures may be substantially symmetrically arranged around a periphery of the compartment.
The arrangement of the apertures may be radially symmetric.
The unit may comprise an actuator for opening and closing the doors. The actuator may be connected to a sensor. The sensor may be a supply air sensor arranged to measure supply air temperature. The sensor may be a room air sensor arranged to measure an air temperature of the space.
The unit may comprise a supply air sensor and a room air sensor. Each of the supply air sensor and the room air sensor may be connected to a corresponding actuator, or to the same actuator.
The actuator may comprise one or more arms which engage with respective damper doors. Where the compartment is frusto-conical, the arms may translate in a direction substantially parallel to a central axis of the compartment. The arms may be connected to a connection ring. The actuator may further comprise a drive for incrementally translating a position of the arms. The drive may engage with the connecting ring. The drive may comprise a stepper motor or a brushless DC motor. The doors may be pushed open by supply air pressure onto their respective arms. Furthermore, gravity may pull the doors open onto their respective arms. The arms may be magnetically engaged with respective doors.
In an alternative embodiment, the arms may translate rotationally relative to the damper compartment. The arms may translate both rotationally relative to the damper compartment and linearly in a direction substantially parallel to a central axis of the compartment.
The unit may comprise a translating ring and a docking ring. Where the actuator comprises a plurality of arms, one or more of the arms may have a locking mechanism wherein the locking mechanism selectively engages the respective arm with either the translating ring or the docking ring. (
The air deflector may comprise a perforated plate. The air deflector may comprise a multi-cone diffuser.
The air deflector may comprise a swirl diffuser with a plurality of discharge elements, the discharge elements being substantially radially arranged. The air deflector may comprise more than one swirl diffuser. In an embodiment the air deflector comprises two or three, or more, swirl diffusers. Where the outlet comprises more than one swirl diffuser, the swirl diffusers may be located adjacent to one another.
The discharge element may comprise blades. Each blade may have a trailing edge and a leading edge.
The diffuser unit may comprise a core portion delimited from the damper compartment by a core conduit.
Although the core portion is centrally located in the embodiments illustrated and discussed, it is to be realised that in further embodiments the core portion may be located elsewhere.
The core conduit may comprise a shroud, the shroud having an inlet into which air from the pressure plenum enters the shroud, and an outlet through which air exits the shroud.
The core portion may house one or more actuators.
The core portion may comprise a divider dividing the core portion into an upper portion associated with the pressure plenum and a lower portion associated with the space into which the air is discharged by the diffuser unit during use. The divider may be formed with one or more induction inlets. The induction inlets may be nozzles. The divider may have a removable proximal portion that seals to a distal portion wherein the distal portion is formed with the nozzles. The removable proximal portion may facilitate removal of the actuator for maintenance (
The core portion may comprise a cap and the cap may be perforated.
The cap may be manually removable to provide access to the core portion. Where the core portion houses one or more sensors such as temperature sensors and/or pressure sensors, a manually removable cap may provide relatively easy access to these sensors (and any other components, such as one or more actuators, housed in the core portion) for maintenance purposes, without requiring removal of the entire unit.
The core portion may comprise a second inlet located in the lower portion wherein airflow through the induction inlets causes an induced airflow through the perforations in the cap into the shroud through the second inlet to form a combined airflow which exits the shroud through the outlet. The second inlet may be located in an upper part of the lower portion.
The unit may comprise a protrusion located in the lower portion of the core portion separating the perforations in the cap from the shroud outlet. Where the shroud is rotationally symmetric (e.g. in the shape of a partial cone or cylinder), the protrusion may extend along a line parallel to a central axis of the shroud. The protrusion may form the second inlet located in the lower portion of the shroud. The protrusion may be formed by a cylinder.
The induction inlet may be configured to impart a swirl to the combined airflow. Where the induction inlet comprises one or more nozzles, the nozzles may be angled relative to a central axis of the unit.
The unit may comprise an induction damper. The induction damper may be operable between a closed position in which induced airflow is restricted or prevented and an open position in which induced airflow is permitted.
Where the unit comprises an actuator for opening or closing the damper doors, the induction damper may be connected to the actuator. The actuator may act to close the damper doors and move the induction damper to a closed position. The actuator may act to open the damper doors and move the induction damper to an open position. The actuator may act to first close the damper doors and then move the induction damper to a closed position. The actuator may act to first move the induction damper to the open position and then open the damper doors. The actuator may act so that the induction damper is open when the damper doors are open.
The core portion may comprise a first sensor located in the upper portion and/or a second sensor located in the lower portion.
The first sensor may sense a temperature of air in the pressure plenum and the second sensor may sense temperature in the space. The first and/or second sensor may be a thermal actuator. The first and/or second sensor may be connected to a corresponding actuator for actuating the aperture doors.
The unit may comprise one or more pressure sensors for measuring a static pressure of the supply air relative to a static pressure of the space. In an embodiment, the pressure sensor is located in the lower portion with a snorkel extending into the pressure plenum outside of the damper compartment and the upper portion. Where the unit comprises an induction damper, the induction damper may, in a closed position, close the upper portion to the pressure plenum. In this case, having a snorkel with an inlet which extends directly into the pressure plenum, and not into the upper portion, may allow for pressure measurements even when the induction damper is closed.
A method of diffusing an airflow using a diffuser unit, the diffuser unit comprising:
The damper door may describe a damper door angle. The damper door angle may be related to an amount of airflow permitted through the corresponding aperture.
The swirl airflow within the damper compartment may have a pitch angle. The pitch angle may be a pitch of the swirl airflow relative to a plane of a face of the air deflector for a majority of the swirl airflow in the compartment.
An airflow rate and pitch angle of the swirl airflow within the compartment may increase with increasing damper door angle.
The method may further comprise maintaining an attachment between an airstream exiting the air deflector and a face of the air deflector. The air deflector may comprise diffuser blades, wherein the method comprises maintaining the attachment by the diffuser blades. The air deflector may comprise a perforated plate, wherein the method comprises maintaining the attachment by the perforated plate acting as a baffle plate.
The method may comprise closing the damper door and achieving an elevated throw from the air exiting the air deflector. The method may comprise closing the damper door. Closing the damper door may achieve a higher distal tangential velocity relative to a proximal tangential velocity of the swirl airflow within the damper compartment. The airstream exiting the air deflector may then comprise an extended throw and a reduced airflow rate. The static pressure within the pressure plenum may be substantially constant. A throw of the airstream exiting the air deflector may be substantially constant as the damper doors close or may be greater than if the tangential velocity distribution of the air deflector were substantially constant.
The method may comprise substantially or fully closing the damper door. A small but non-negligible swirl airflow may be formed in the compartment when the damper door is substantially or fully closed. In this case, the airstream exiting the diffuser unit via the air deflector may do so in a swirl in the plane substantially parallel to the discharge face of the discharge unit.
The unit may comprise more than one door. The method may comprise locking one or more doors.
The unit may comprise a blanking segment and the method may comprise using the blanking segment to obstruct a portion of airflow though the unit.
The method may comprise sensing a temperature of a supply air and/or a temperature of the space. The doors may be operated in response to a determined temperature. The doors may be operated in dependence on a temperature of a supply air and/or a temperature of the space.
The unit may comprise an induction chamber having induction inlets, the method comprising drawing air into the induction chamber from the space through induction caused by an airstream through the induction inlets derived from the pressure plenum to form a combined airflow which exits through the diffuser outlet. The induction chamber may be defined by a divider situated in a core portion of the diffuser unit.
The combined airflow which exits through the diffuser outlet may do so in a substantially 360° pattern in the plane substantially parallel with the diffuser face. The combined airflow which exits through the diffuser outlet may project away from the diffuser outlet in the direction substantially parallel to the plane defined by the face of the diffuser outlet. The combined airflow which exits through the diffuser outlet may act to arrest leakage from the damper doors. This may help to prevent short-circuiting of the leakage into the induction chamber.
A further embodiment relates to a method of determining an airflow rate for a diffuser unit, the diffuser unit comprising:
The damper compartment and the damper apertures may be arranged so that air entering the damper compartment through the damper apertures from the pressure plenum forms a swirl before exiting the damper compartment through the air deflector.
The position of the door may be operable between an open position and a closed position, and a plurality of intermediate positions between the open position and the closed position.
The door may be actuated by a drive. The position of the door may be determined with reference to the drive. The drive may increment a counter and the position may be determined with reference to the counter.
The unit may comprise a switch which is activated when the door is closed or open to zero the counter.
In the following detailed description, reference is made to accompanying drawings, which are not to scale and which form a part of the detailed description.
The same part number is used for the same part if it appears across multiple figures.
The illustrative embodiments described in the detailed description, depicted in the drawings and defined in the claims, are not intended to be limiting. Other embodiments may be utilised, and other changes may be made without departing from the spirit or scope of the subject matter presented. It will be readily understood that the aspects of the present disclosure, as generally described herein and illustrated in the drawings can be arranged, substituted, combined, separated and designed in a wide variety of different configurations, all of which are contemplated in this disclosure.
Embodiments will now be described, by way of example only, with reference to the accompanying drawings in which:
The embodiments, as described herein, relate generally to an air diffuser assembly for ceiling discharge with an air supply supplied from a pressure plenum or duct.
For reasons of simplicity, the illustrations below show the diffuser discharge openings largely coincident with a plane that is coincident with the diffuser discharge plane. It will be appreciated by persons skilled in the art that the discharge openings need not be coincident with a plane (for example, they may lie on a curved surface) and that they need not be coincident with the diffuser discharge plane (which, for example, may be a perforated plate further downstream).
For reasons of simplicity, power supply and communications cabling to diffusers and within diffusers is not shown.
It will be appreciated by persons skilled in the art that numerous variations and/or modifications may be made as shown in the specific embodiments without departing from the spirit or scope of the description. The present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive.
Any reference to prior art contained herein is not to be taken as an admission that the information is common general knowledge, unless otherwise indicated.
Also shown in
For maintenance access from room 18, diffuser face plate 1b may fold down to provide access to damper 6 and the associated mechanism, actuators 10a, 10b and 10c, sensors 10e and 10f, and PC board 10d, or the above components may be attached to removable diffuser face plate 8.
Advantageously, the changes in throw to a terminal velocity of 0.25 m/s of diffuser airstream 9a, or 9a′ and 9a″, due to changes in position of damper 6, are not as great as they would be if both the airflow rate and static pressure of supply airstream 3 were to be increased or decreased simultaneously, as would occur if damper 6 were located well upstream of diffuser spigot 4, as throw is proportional to the square root of airflow rate multiplied by the square root of the discharge velocity, but discharge velocity, in the VAV diffuser of the prior art described above, is maintained to be substantially constant. The resultant reduced sensitivity of throw to airflow rate adjustment reduces the degree of over-throw and under-throw of the diffuser airstream 9a, or 9a′ and 9a″, into room 18, thereby potentially improving comfort levels in the occupancy space compared to those that would have been achieved in a traditional VAV system with non-variable geometry VAV diffusers (often referred to as fixed aperture diffusers). A further advantage is that discharged airflow 9, or 9′ and 9″, can be turned down to a lower airflow rate without dumping given that Coanda effect attachment of diffuser airstream 9a, or 9a′ and 9a″ to the ceiling is maintained even at extremely low airflow rates due to the substantially constant velocity of discharged air stream 9, or 9′ and 9″.
Inaccurate airflow measurements also occur at low airflow rates due to the extremely low dynamic pressure of airstream 3a when the velocity of supply airstream 3 is low, as dynamic pressure is proportional to the square of the velocity, and the air velocity is very low at low airflow rates.
The top entry of supply duct 5 requires substantial ceiling void height H1 (typically 500 mm to 800 mm), which may be disadvantageous.
Disadvantageously, face plate 8 protrudes into room 18 as it is lower than the plane of ceiling grid underside 2′, which may be architecturally undesirable.
For optimised airflow rate adjustment authority by damper 6 without excessive pressure drop, the ratio of the diffuser spigot 4 area to the annular area of maximum damper aperture 7a should be substantially constant for all diameters—and hence for the maximum airflow rate capacities—of diffuser spigot 4, which requires that both the diameter of damper 6 and the maximum stroke A1 of aperture 7a increase approximately in direct proportion to the diameter of diffuser spigot 4. Diffuser spigot 4 is usually round and typically available in one of five nominal diameters, viz 150 mm, 200 mm, 250 mm, 300 mm and 350 mm, suitable for increasing ranges of airflow up to approximately 300 to 330 L/s at a maximum sound power level of approximately 45 dB(A), which equates to a sound pressure level of approximately NC 30 in room 18 based on 10 dB room absorption, and hence damper 6 as well as the maximum damper stroke A1 of aperture 7a are typically sized to suit these different diffuser spigot diameters; though it should be noted that the diffuser static pressure at approximately 300 to 330 L/s is typically well in excess of 40 Pa, which is substantially above the preferred maximum static pressure of 30 Pa to minimise fan energy requirements. Consequently, diffuser dampers and associated mechanism stroke are not interchangeable between diffuser spigot sizes if optimum performance is to be achieved across all spigot sizes.
Also shown is induction nozzle 11, located behind diffuser hub 8a, discharging primary airstream 12 and inducing secondary airstream 13 into induction channel 15, both of which are then discharged through hub discharge opening 15a, and drawing replenishment airstream 14 from room 18 via face plate inlet 14a across room temperature sensor 10e.
Advantageously, high induction swirl diffuser discharge 9a, 9a′ and 9a″ may improve thermal comfort in room 18 at both high and low airflow rates, and enables the use of a lower temperature of supply airstream 3 without dumping.
Advantageously, no part of diffuser 1b protrudes into room 18 as no part is located below the plane of diffuser face 1, which in turn is substantially coincident with the plane of ceiling grid underside 2′.
Potentially disadvantageously, the multiple abrupt changes in direction of the air from supply airstream 3 to diffuser airstream 9a′ and 9a″ result in an extremely high pressure drop and airflow noise generation, especially at high airflow rates. Furthermore, damper 6 blocks discharged airstream 7′ and 7″ from blowing onto the full radial length of each swirl blade 17, resulting in inactive swirl blade portions 17a even at high airflow rates when damper 6 is fully open, causing a high pressure drop of the active swirl blade portions 17a′. This further increases pressure drop and airflow noise, whilst severely limiting maximum airflow capacity, typically to less than 200 L/s at a sound power level of 45 dB(A), whilst also creating supply stream eddies 7s and eddy discharge 7s′ towards diffuser hub 8a, partially short-circuiting into induction inlet 14a, thereby leading to inaccurate room temperature sensing by room temperature sensor 10e.
Substantial ceiling void height H1, typically of 450 to 750 mm, is required, which may be disadvantageous.
Maintenance access to damper 6 and the associated mechanism, actuator 10c, sensors 10e and 10f, and PCB 10d is not available from room 18 due to space restrictions and the complexity that would be required to seal induction system components against the positive pressure of diffuser chamber 16.
As with the non-swirl actuator VAV diffusers of the prior art shown in
Supply air 3 passes through side-entry spigot 4′ into connection box 20. Bellmouth inlet extension 4″ attached to diffuser spigot 4 directs supply airstream 3a′ onto pressure tube array 10h with substantially uniform dynamic pressure 3d′ to achieve reliable dynamic pressure readings by pressure sensor 10g when supply airstream 3a′ is high.
In order to ensure substantially unrestricted airflow of supply airstream 3a′, a connection box height H2 of approximately 350 mm is required for a supply airflow rate 3 of approximately 200 L/s.
Not shown are embodiments with a connection box height H2 of approximately 250 mm and which exclude bellmouth inlet extension 4″, pressure sensor 10g and dynamic pressure tube array 10h (which would provide unstable dynamic pressure measurements in the absence of bellmouth inlet extension 4″). It will be apparent to a person skilled in the art that such embodiments will result in substantially increased pressure drop and airflow noise, and will not be suitable for applications that require the volume flow rate of supply air 3 to be determined within diffuser 1c.
Damper 6 is perforated and is sealed via bellows 6′ to shroud 6″ that, in turn, seals to the proximal portion of swirl blades 17 radiating from hub 8a, all of which encompass damper chamber 16′. Pilot airstream 7″′ flows into damper chamber 16′ and is discharged by the proximal portion only of swirl blades 17 into room 18 as discharged pilot airstream 9″′ which attaches to diffuser face 1 and surrounding ceiling (not shown) by Coanda effect suction as diffuser pilot airstream 9a″′, which induces low velocity discharged airstream 9 in
The minimum turndown percentage and the minimum airflow rate are pressure dependent. For example, if system static pressure rises above the pressure (typically approximately 30 Pa) at which supply airstream 3 is equal to a desired diffuser design airflow rate delivered when damper 6 is fully open, then pilot airstream 7″′ and discharged pilot airstream 9″′ will increase to above 25% of the desired diffuser design airflow rate. For example, if the system static pressure at the diffuser were to rise from 30 Pa to 60 Pa (which is the typical maximum permissible pressure to prevent excessive noise generation) then the effective diffuser turndown would increase from 25% to 35% relative to the design airflow rate. Such high and pressure dependent diffuser turndown is disadvantageous.
An alternative cooling-only embodiment (not shown) does not include the supply air thermal actuator 10b.
Aperture 7a is adjusted by rotary damper 6a rotating on ball bearings or sliders 22 in response to room air thermal actuator 10a and supply air thermal actuator 10b expanding or contracting due to the temperature of room air and supply air drawn across each, respectively. Not shown is a supply air fan or motorised damper blowing supply air 3 at a substantially constant static pressure upstream of side-entry spigot 4′ into connection box 3.
Advantageously, no part of diffuser 1d protrudes into room 18 as no part is located below the plane of diffuser face 1, and hence below the plane of ceiling grid underside 2′.
In an alternative embodiment spigot 4′ is located on top of connection box 20.
In yet a further embodiment, diffuser 1d is freely suspended in room 18, rather than diffuser face 1 resting in ceiling grid 2.
A divider, in the form of a mounting plate 42, divides the cavity in the core here encapsulated by the shroud 6″ into a primary chamber 54 and a secondary chamber 14b. A protrusion, here in the form of a cylinder 6″′, extends up from the region near the face of the diffuser unit and into the second chamber forming a venturi wall. The void between the venturi wall 6″′ and the mounting plate 42 forms an induction inlet 15′. The conduit between the venturi wall 6″′ and shroud 6″ forms a venturi.
Primary air 12′ flows across supply thermal element 10b in primary chamber 54, before being discharged by induction nozzle array 11′ into induction channel 15 as primary airstream 12 to induce secondary airstream 13 from secondary chamber 14b through induction inlet 15′ above venturi wall 6″′ into the upper portion 52 of induction channel 15, with both airstreams then being combined and discharged as discharged pilot airstream 9″′ by the proximal portion only of swirl blades 17 contained within shroud 6″, thereby drawing replenishment airstream 14 into secondary chamber 14b and across room thermal actuator 10a from room 18 via face plate inlet 14a in hub cap 8b.
As better illustrated in
Primary airstream 12 is typically no more than about 10% of supply airstream 3 when damper 6 is fully open, as shown in
It will be apparent to a person skilled in the art that since diffuser throw (not shown) to a fixed terminal velocity (typically taken as 0.25 m/s) is proportional to the square root of the product of volume flowrate and discharge velocity, diffuser throw at a medium airflow rate, as generated by medium damper aperture 7a in
Alternative embodiments utilising an electric actuator, rather than one or more thermal actuators, to rotate rotary damper 6a are possible.
Many alternative embodiments of rotary damper 6a and damper housing 6b are possible to achieve swirl 23 of substantially constant distal tangential velocity in cyclone plenum 16″ for both high and medium damper aperture 7a settings, corresponding to high and medium airflow rates 7, respectively, and hence may achieve substantially constant distal velocity of discharged airstream 9 and diffuser airstream 9a across a broad range of damper apertures 7a for supply airstream 3 of substantially constant static pressure at side-entry spigot 4′. Examples of two such alternative embodiments are shown in
The rotary damper doors shown in
Advantageously, no part of diffuser 1d protrudes into room 18 as no part is located below the plane of diffuser face 1, which in turn is substantially coincident with the plane of ceiling grid underside 2′.
In an alternative embodiment, spigot 4′, through which supply airstream 3 enters connection box 20, is located on top of connection box 20 instead of on the side.
In yet a further embodiment, diffuser 1d is freely suspended in room 18, rather than diffuser face 1 resting in ceiling grid 2.
For a given static pressure in connection box 20, the airflow rate and swirl pitch angle β of damper airstream 7 relative to a plane parallel to diffuser face 1 (
When damper aperture 7a is fully open, as shown in
In comparison to fully open damper aperture 7a and for the same static pressure in connection box 20, when damper aperture 7a is open to a medium setting (not shown) supply airstream 3 of reduced airflow rate passes into connection box 20 through side-entry spigot 4′ via perforated baffle plate 21, which spreads supply airstream 3, to flow into cyclone plenum 16″ as damper airstream 7 of reduced airflow rate and high tangential velocity (i.e. similar in velocity to when damper aperture 7a is fully open) to be discharged through 360°, in a plane substantially parallel with diffuser face 1, by discharge cone 100 into room 18 as discharged airstream 9 of reduced airflow rate with swirl of higher distal tangential velocity and lower proximal tangential velocity towards shroud 6″, which is deflected by at least the distal portion of swirl blades 17 external to shroud 6″ to attach to diffuser face 1 and surrounding ceiling (not shown) by Coanda effect suction as diffuser airstream 9a of reduced airflow rate that spreads in a plane substantially parallel to diffuser face 1, achieving a higher throw of diffuser airstream 9a, in a plane substantially coincident with or parallel to diffuser face 1, relative to that which would be achieved if the velocity were uniformly spread across swirl blades 17 external to shroud 6″.
Similar to the airflow patterns shown in
In comparison to the embodiments shown in
Additionally, the latter may have the advantage that compression door seals can readily be made to be air tight when damper doors 6a′ shut, whereas the sliding action of rotary damper 6a in the former is more challenging to seal and is likely to result in leakage or increased friction to the operation of rotary damper 6a.
An alternative embodiment, not shown, has leading edge barbs curved upwards to a steeper leading edge angle than the angle ε of swirl vane 17 relative to a plane parallel to diffuser face 1.
A further embodiment, not shown, has a successively increasing leading edge absolute angle of attack of the barb 17′ tip by varying angle θ shown in X Sec A-A from a large value for a distal barb 17′ to a small value for a proximal barb 17′, and in which θ≤s.
The non-uniform absolute orientation of leading edge barbs 17′, whereby, when progressing in a proximal direction, the absolute angle of attack in side view of each successive barb tip is increased by decreasing 0, and each successive barb tip is toed out in plan view such that δ2>δ1, is advantageous in reducing both noise and air pressure drop, in particular for the embodiments shown in
Curved leading edge barbs 17′ on their own are a preferred embodiment as they are more effective at reducing noise than trailing edge serrations 17″, are aesthetically less obtrusive, and additionally reduce diffuser pressure drop.
Preferred dimensions for H1 are 5 mm to 20 mm, for Wl are 1 mm to 5 mm, for R are 5 mm to 50 mm, for Ht are 5 mm to 20 mm, and Wt are 1 mm to 5 mm, and for s are 200 to 50°.
Advantageously, no part of diffuser 1d protrudes into room 18 as no part is located below the plane of diffuser face 1, which in turn is substantially coincident with the plane of ceiling grid underside 2′.
In an alternative embodiment, spigot 4′, through which supply airstream 3 enters connection box 20, is located on top of connection box 20 instead of on the side.
In yet a further embodiment, diffuser 1d is freely suspended in room 18, rather than diffuser face 1 resting in ceiling grid 2.
For a given static pressure in connection box 20, the airflow rate and swirl pitch angle β of damper airstream 7 relative to a plane parallel to diffuser face 1 (
Fully open damper aperture 7a, as described for
When operating at the same static pressure in connection box 20 as above with damper aperture 7a open to a medium setting (not shown), damper airstream 7 of reduced airflow rate and high tangential velocity (i.e. similar in velocity to when damper aperture 7a is fully open) generates swirl with higher distal tangential velocity and lower proximal tangential velocity that is deflected by perforated baffle plate 17′ to be discharged through 360°, in a plane substantially parallel with diffuser face 1, substantially by the distal portion of diffuser baffle plate 17′ external to shroud 6″ into room 18 as discharged airstream 9 of reduced airflow rate and swirl of higher distal tangential velocity and lower proximal tangential velocity, to attach to diffuser face 1 and surrounding ceiling (not shown) by Coanda effect suction as diffuser airstream 9a of reduced airflow rate that spreads in a plane substantially parallel to diffuser face 1, achieving a higher throw of diffuser airstream 9a relative to that which would be achieved if the velocity were uniformly spread across baffle plate 17′ external to shroud 6″.
When damper door 6a′ is strongly throttled or fully closed but leaking, damper airstream 7 is discharged with swirl 23, improving the stability and increasing rotational momentum of discharged airstream 9 at very low airflow rates, thereby improving throw when strongly throttled or facilitating Coanda effect suction to diffuser face 1, reducing the risk of dumping when leaking, and enabling variable air volume (VAV) turndown to extremely low airflow rates, including to less than 15% airflow of that which is achieved when damper aperture 7a is fully open.
In comparison to the embodiment shown in
As described in
As described in
Similarly, as described in
Advantageously, substantially balanced static air pressure on damper doors 6a′ allows for substantially pressure independent operation of the damper doors as it eliminates or reduces the air pressure forces on the damper mechanism and actuator(s), which is especially beneficial for thermal actuators, as these are extremely weak.
Disadvantageously, especially for electrically actuated VAV diffusers in which it is highly beneficial for damper doors 6a′ to seal fully shut, a substantially centrally located door axis of rotation 6a″ on each damper door 6a′ causes greater complexity in sealing the top and bottom of each damper door 6a′ shut in comparison to the embodiment shown in
Electric actuator 10c is connected to worm gear 26, which drives worm nut 27, which is fixedly connected to both induction damper 29 and the bottom of damper spring 28, which is in compression and pushes a plurality of damper spokes 30 towards the underside of induction damper 29, which in turn acts as a stop beyond which damper spokes 30 cannot travel. Damper spokes 30 are fixedly attached to translating ring 31, to which a plurality of damper arms 32 is fixedly attached, each terminating in one of a plurality of magnets 32′. The plurality of magnets 32′ is arranged relative to an equal number of damper doors 6a′ (shown indicatively only in
In an alternative embodiment, induction damper 29 is located above damper housing 6b and is mechanically linked to worm nut 27 to open upwards from damper housing 6b.
The airflow rate of supply air stream 3 is calculated by the processor (not shown) on PC board 10d or by a remote processor as a function of the static air pressure in connection box 20 and the position of worm nut 27, which in turn determines the door angle α of damper doors 6a″. The processor may determine the position of worm nut 27 by counting the number of rotations of worm gear 26 and by zeroing the position of electric actuator 10c when worm nut 27 is fully down by means of a micro-switch 40 (shown in
In an alternative embodiment, shroud slots 30′ are at an acute angle relative to diffuser centre-line 0.
For a given static pressure in connection box 20, the velocity of damper airstream 7 in
In
Each magnet 32′ corresponding to a damper door 6a′ is located within a door recess 6a′2 of that damper door, whereas each magnet 32′ corresponding to a half-sized damper door 6a′1 is located directly on damper door 6a′1. For ease of comparison, unlabelled dashed lines in
Turbulators 6a3 may, alternatively, be fashioned as vortex generators, with one embodiment being a plurality of non-planar solids (refer to
An alternative vortex generator embodiment where the vortex has a blade shape with parallel front and back edges, a sloping top edge, and sloping sides, is shown in
In a further embodiment, not shown, turbulators 6a3 are a plurality of hemispherical protrusions of 1 to 2 mm radius at a centre-line spacing of 3 to 5 mm.
Further embodiments of turbulators 6a3 may consist of any combination of the turbulators described above.
In an alternative embodiment, half-sized damper doors 6a′1 may be individually locked closed, or may be unlocked to open and close, as described in
Electric actuator 10c is connected to sun gear 38, which meshes with and drives planetary gears 38′1 and 38′2, which in turn mesh with and rotate within ring gear 38″, which is fixedly attached to housing 6b and centred about diffuser centre-line 0. The axes of rotation of planetary gears 38′1 and 38′2 are attached to cam sleeve 39, which rotates within shroud 6″ about diffuser centre-line 0, and is axially constrained from movement parallel to diffuser centre-line 0 by constraining slot 41′ about constraining pins 39′ fixed to shroud 6″. Constraining slot 41′ lies substantially in a plane parallel to diffuser face 1.
As shown in
Induction pins 39″′ slide in shroud slots 30′, which are parallel to diffuser centre-line 0, thereby rotationally constraining translating ring 31 about diffuser centre-line 0. Not shown is a feature that similarly constrains induction damper 29 from rotation about diffuser centre-line 0.
In
In
Advantageously, the removal or installation of the components described above and shown in
Also shown removed from diffuser 1d is mounting plate 42, which is connected to pressure sensor 10g by pressure tube 10g″. Electric actuator 10c is fixedly attached to the underside of mounting plate 42, with electric actuator shaft 10c′ protruding through mounting plate 42. Supply air temperature sensor 10f, hidden from view, also protrudes through mounting plate 42.
The above embodiment provides access from below the diffuser, without requiring removal of the diffuser from ceiling grid 2 (not shown) for installation, removal or replacement of PC board 10d, all sensors (including 10e, 10f, 10g, 10h), Bluetooth antenna 10d1 and electric actuator 10c.
The above embodiment provides access from below the diffuser, without requiring removal of the diffuser from ceiling grid 2 (not shown) for installation, removal or replacement of PC board 10d, all sensors (including 10e, 10f, 10g, 10h), Bluetooth antenna 10d1 and electric actuator 10c.
Additionally, when dampers doors 6a′ and half-sized damper doors 6a′1 are fully open, microswitch 40 is activated by arm 40″ attached to induction damper 29 or worm nut 27, zeroing electric actuator 10c to the fully open position.y. The bottom edges of damper doors 6a′ substantially abut inlet cone 101, reducing door edge vortices to reduce pressure drop and noise. Discharge cone 100, abutting distal edges of swirl vanes 17, further reduces pressure drop and noise.
Nozzle array 11′ shown in
Diffuser 1d provides greater distal discharge velocity and reduced proximal discharge velocity for extended throw of diffuser airstream 9a in a plane parallel to diffuser face 1 when damper doors 6a are partially throttled, achieving a specific airflow rate of less than 0.4 L/s/m2 (relative to room 18 floor area) at an ADPI (Air Diffusion Performance Index) in excess of 90% when turned down to 15% of the maximum airflow rate for various maximum airflow rate configurations of damper doors 6a′ and half-sized damper doors 6a′1, at approximately 30 Pa static in connection box 20 and at a supply-to-room air temperature differential of −15 K.
Diffuser 1d reduces the vertical temperature gradient in room 18 when providing part-load heating due to the greater distal discharge velocity and reduced proximal discharge velocity achieved when damper doors 6a are partially throttled, thereby extending the throw of diffuser airstream 9a and increasing agitation of the air in room 18. This improves comfort by reducing the risk of a “warm head/cold feet” sensation for occupants of room 18.
The maximum airflow rate of supply air 3, so as not to exceed either a sound pressure level in room 18 of NC 30 (based on 10 dB room absorption) or a static pressure of 30 Pa in connection box 20, is approximately 230 L/s for neck size DN of diameter 355 mm, and approximately 450 L/s for neck size DN of diameter 500 mm.
The minimum face dimension G1′ is approximately 495 mm for neck size DN of diameter 355 mm and 595 mm for neck size DN of diameter 500 mm, suitable for a minimum ceiling grid centre-line dimension G1 of approximately 500 mm and approximately 600 mm, respectively, with connection box 20 having a wall thickness of up to 25 mm, suitable to achieve an R1 thermal insulation rating.
Spigot 4′ typically has a maximum effective diameter of approximately 300 mm for neck size DN of diameter 355 mm, and of approximately 400 mm for neck size DN of diameter 500 mm.
The minimum connection box height H3 is 200 mm, based on connection box 20 having a wall thickness of up to 25 mm, suitable to achieve an R1 thermal insulation rating. Typical connection box height H3 varies from 250 mm to 450 mm, depending on the maximum airflow rate of supply air 3.
The corners and edges of connection box 20 may be facetted 20′ to facilitate installation of the assembled diffuser unit, comprising diffuser 1d and connection box 20, into ceiling grid 2 from below without requiring dismantling of ceiling grid 2.
The latter embodiment may be preferred for the following reasons:
Vertical damper axes of rotation 6a″′ potentially result in restricted onflow-chamber 120 relative to a side wall of connection box 20, thereby potentially restricting the flow of damper airstream 7 onto damper doors 6a′, whereas inclined damper axes of rotation 6a″ increase the average distance from a connection box 20 side wall to damper doors 6a′, as indicated by shaded area 110, providing improved airflow from onflow-chamber 120 onto damper doors 6a′, reducing pressure drop and providing more uniform discharge from damper doors 6a′.
Shaded area 110, created by inclined damper axes of rotation 6a″, provides a path for supply air 3 (not shown) to pass intermediate damper doors 6a′ (shown) as it travels from side-entry spigot 4′ (shown as hidden detail) to damper doors 6a′ proximate a connection box 20 side wall located substantially opposite side-entry spigot 4′ (not shown, as this assembly is located behind the viewer of
In
In comparison to vertisubstantiually parallel damper axes of rotation 6a″′, inclined damper axes of rotation 6a″ orientate damper doors 6a′ to direct damper airstream 7 partially towards multi-cone deflector 7c, especially when damper doors 6a′ are fully open, thereby reducing pressure drop and noise.
In comparison to substantially parallel damper axes of rotation 6a″′, inclined damper axes of rotation 6a″ orientate damper doors 6a′ to open partially downwards (assuming diffuser centre-line 0 is vertically orientated, as would be the case if diffuser face 1 is horizontal) and hence gravity assists in pulling damper doors 6a′ open onto magnets 32′.
In comparison to substantially parallel damper axes of rotation 6a″′, inclined damper axes of rotation 6a″ orientate damper doors 6a′ to open partially in a direction parallel to diffuser centre-line 0, facilitating a simple worm gear (26) mechanism with direct stepper motor (10c) drive, to open and close damper doors 6a′ via movement of damper arms 32 in a direction parallel to diffuser centre-line 0.
Not shown is an alternative embodiment with damper axes of rotation substantially radially aligned about diffuser centre-line 0 in diffuser neck DN1 (
An air delivery system incorporating the diffuser described herein may provide the potential for substantial energy savings, increased VAV turndown, increased spread when turned down, full shut-off, lower supply air temperature, and more effective performance, as well as for improved thermal comfort, enhanced indoor air quality, reduced capital cost, increased flexibility to change, and enhanced aesthetics.
HVAC systems that deliver supply air to spaces via actuator driven VAV cyclone swirl diffusers in accordance with embodiments may be designed to operate in HVAC systems with variable speed drive fans or that incorporate devices, such as duct pressure control dampers, to potentially reduce airflow during periods of low thermal load, thereby saving fan energy. This is because a diffuser as described by certain embodiments, in which supply air is discharged substantially in the plane or parallel to the plane of the ceiling, may have the supply air supplied at a lower temperature (as low as 7° C., in comparison to 10° C. to 12° C. for the prior art) and hence at a lower airflow rate (typically 30% less airflow) for the same cooling capacity and without creating draughts.
Additionally, a diffuser in accordance with embodiments may have a greater VAV range of operation (typically 20% greater) as it can be turned down to a far lower airflow rate, equating to a pressure independent turndown to 6 L/s, or 15% or less of diffuser maximum airflow rate, than comparable swirl diffusers of the prior art, which typically have a pressure dependent turndown ratio to 25%, equating to turndown to a value greater than 25% when subjected to a pressure greater than the design pressure (to 35%, for example, if system pressure increases from a design static pressure of 30 Pa at the diffuser to 60 Pa). A lower minimum airflow rate may reduce the risk of overcooling the space or of requiring reheat to prevent overcooling, thereby potentially improving comfort and reducing energy costs.
A further potential advantage is that a diffuser in accordance with embodiments may achieve substantially greater airflow rate turndown at a supply-to-room temperature differential of −15 K and an ADPI in the room in excess of 90%, and maintain substantially constant throw in a plane parallel to the diffuser face, or achieve greater throw than is provided by a comparable swirl diffuser of the prior art when turned under the same conditions, thereby potentially increasing the floor area that may be served by a single diffuser. This may reduce the number of diffusers required, potentially saving capital costs.
Additionally, the maximum airflow rate that may be discharged by a diffuser as described by some embodiments may be greater than that of a comparable swirl diffuser of the prior art (more than 75% greater), thereby potentially allowing a smaller number of diffusers to be used (potentially 40% fewer diffusers), for diffusers that fit into a ceiling grid of approximately 600 mm×600 mm, or a smaller diffuser face size to be selected, such as one suitable for a 500 mm×500 mm ceiling grid up to a maximum airflow rate of 230 L/s at a sound pressure level in the room of NC30 (based on 10 dB room absorption), hence further reducing capital costs and improving aesthetics.
Further embodiments may allow the airflow rate range of the diffuser to be reconfigured, and additionally, for this to be done in situ without removal of the diffuser from the ceiling. This may provide flexibility for tenancy changes, such as for a diffuser that previously served a large space requiring a large airflow rate to be reconfigured to serve a small space requiring a small airflow rate. Importantly, this may be achieved without reducing the diffuser turndown ratio or minimum airflow rate. Diffusers of the prior art do not include such features.
Embodiments of the diffuser may include airflow rate determination by means of static pressure measurements within the connection box mapped to the position of the damper doors. This may allow diffuser airflow rate to be relatively accurately determined even at low airflow rates, and additionally may allow the actual diffuser static pressure to be determined for each diffuser so as to potentially allow system pressure to be controlled (e.g. via the system fan) to relatively accurately maintain at least each diffuser's minimum permissible static pressure, which is typically 10 Pa, or to achieve the required static pressure of the diffuser with the highest demand. Moreover, measuring static pressure at each diffuser may provide redundancy. If a pressure sensor were to fail then only the actual static pressure at that one diffuser would be lost (and may be estimated from the other pressure sensors), potentially without compromising operation of the entire system or causing system failure.
Some embodiments may incorporate room air induction systems to allow integrated sensing of room air temperature, humidity (RH) and indoor air quality (CO2 or VOC), thereby potentially obviating the need for external wiring of remote sensors.
Embodiments of the diffuser may include an induction system that discharges through 360° in a plane parallel to the diffuser face, thereby arresting leakage when damper doors are closed, preventing draughts due to dumping, and preventing short-circuiting of leakage or of supply air discharged by the diffuser into the induction system and hence improving the accuracy of integrated sensing of room air temperature, humidity and indoor air quality (CO2 or VOC), and providing uniform distribution of the discharged primary and secondary air of the induction system to the conditioned space.
Embodiments that further include an induction damper may allow each diffuser to be fully shut off, for example when the space served is unoccupied, which may be sensed by an optional integrated PIR sensor, thereby potentially saving energy.
Furthermore, embodiments with an induction damper may allow the induction damper position to be adjusted to deliver a constant airflow rate to the induction system to provide pressure independent minimum airflow discharge from the diffuser equal to the minimum airflow rate required for operation of the induction system.
Diffusers according to embodiments may have a lower profile than comparable diffusers of the prior art that deliver a similar airflow rate, thereby potentially reducing the ceiling void height requirement for a given diffuser airflow rate. This may allow larger airflow rates to be achieved per diffuser for a given ceiling void height, potentially reducing the number of diffusers required, or it may allow the building slab-to-slab height to be reduced. Substantial capital cost savings may be achieved.
Blanking segments may be used in embodiments to alter discharge direction from 360° to 270°, 180°, or 2×90° patterns when viewed in plan-view, which may allow the diffusers to be placed close to walls or other obstructions.
Embodiments may provide access through the diffuser hub whilst the diffuser is in situ in the ceiling, for removal or replacement of any sensor, the PC board or the electric actuator, thereby potentially facilitating ease of maintenance and reconfiguration of the diffuser for tenancy changes.
Embodiments of the diffuser may include noise suppression features such as serrations, turbulators and trailing edge diffusers, which may allow diffuser operation even when supply air static pressure is high, thereby making such diffusers suitable for non-static regain duct design systems, such as constant velocity or equal friction duct designs. This may simplify new-build duct design and make diffusers in accordance with embodiments suitable for retrofit applications in which existing ductwork is to be reused.
In the claims which follow and in the preceding description, except where the context requires otherwise due to express language or necessary implication, the word “comprise” or variations such as “comprises” or “comprising” is used in an inclusive sense, i.e. to specify the presence of the stated features but not to preclude the presence or addition of further features in various embodiments.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2020902971 | Aug 2020 | AU | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/AU2021/050923 | 8/20/2021 | WO |
