Abstract:
An air distribution device. The air distribution device an air distribution chamber arranged to receive a flow of ventilation air from the air outlet. The air distribution chamber further having one or more perforated throttling plates or meshes perpendicular to the inner perforated wall and perpendicular to the flow of ventilation air from the air outlet into the air distribution chamber. The air distribution device also includes a pressure equalization chamber formed between an inner air permeable front plate of the air distribution chamber and an outer front plate. A perforation-free area of the outer perforated front plate is smaller than the perforation-free area of the inner perforated front plate in order to equalize ventilation air pressure in the equalization chamber and to provide a uniform flow of air through the outer front plate.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims priority to EP application Serial No. 14151943.9 filed Jan. 21, 2014, the disclosure of which is hereby incorporated in its entirety by reference herein. 
       TECHNICAL FIELD 
       [0002]    The present invention relates to building heating, ventilation and air conditioning systems. More specifically, the invention relates to an air distribution device. 
       BACKGROUND 
       [0003]    Air ventilation systems consist of exhaust air ducts that are used to extract air from rooms and supply air ducts that are used to supply air to rooms. Air circulation between the supply air ducts and the exhaust air ducts via rooms is achieved either naturally or mechanically. Nowadays air circulation in buildings is usually achieved with Air Handling Units (AHU) that contain fans, heating or cooling elements, air filter racks or chambers, sound attenuators, and dampers. Air handling units are usually located on rooftops and they are connected to the exhaust air ducts and supply air ducts. The supply air ducts cannot be simply connected to room space via large uncovered openings because such large openings would lead to non-uniform air flow and draught which is unpleasant and harmful for occupants in the room space. Air distribution devices are used to distribute air uniformly in the room space. Air distribution devices are connected to air outlet ducts and usually comprise an array of openings arranged between the air outlet duct and the room space. 
         [0004]    In displacement ventilation systems supply air from air outlet ducts is supplied at floor level close to occupants and air is extracted to the exhaust air ducts via outlets located above occupied zone, for example, at ceiling height. Heated air rises upwards due to its lower density and is collected via the outlets to the exhaust air ducts. The benefit of displacement ventilation systems is superior indoor air quality because supply air does not mix with contaminated heated air as much as in solutions where supply air distribution is arranged centrally or above occupants. Heated air becomes contaminated due to contamination sources such as electronic systems, electrical systems and occupants. 
         [0005]    The challenge in the air distribution is most often to distribute air as uniformly as possible to a room without generating too much noise. This is especially important in the design of displacement ventilation systems where low-velocity air distribution devices are placed near the occupants. 
         [0006]    Problems in prior art air distribution devices include non-uniform air distribution and unacceptable noise levels. 
         [0007]    Therefore, it would be beneficial to have a solution which avoids the disadvantages of the prior art and where an air distribution device provides a uniform air distribution of supply air with reduced noise levels. 
       SUMMARY 
       [0008]    According to an aspect of the invention, the invention is an air distribution device, comprising: an air outlet for ventilation air; an air distribution chamber arranged to receive a flow of ventilation air from the air outlet, the air distribution chamber being bounded by at least an inner perforated wall allowing air to exit from the distribution chamber, an air impermeable wall opposite the air outlet and an air impermeable wall contiguous with the air outlet, wherein the air distribution chamber further comprises at least one perforated throttling plate or throttling mesh perpendicular to the inner perforated wall and perpendicular to the flow of ventilation air from the air outlet into the air distribution chamber; and a pressure equalization chamber bounded by the inner perforated wall, an outer perforated wall parallel to the inner perforated wall within a distance from the inner perforated wall, a section of the air impermeable wall opposite the air outlet and a section of the air impermeable wall contiguous with the air outlet, wherein a perforation-free area of the outer perforated wall is smaller than the perforation free area of the inner perforated wall in order to equalize ventilation air pressure in the equalization chamber and to provide a uniform flow of air through the outer perforated wall. 
         [0009]    In one embodiment of the invention, by perpendicular to the flow of ventilation air from the air outlet into the air distribution chamber is meant perpendicular to a longitudinal axis of the air distribution device, the longitudinal axis being between the air outlet, that is, the air impermeable wall having an opening to connect to the air outlet, and the air impermeable wall opposite the air outlet. 
         [0010]    In one embodiment of the invention, the air distribution chamber is also bounded by at least one air impermeable wall. 
         [0011]    In one embodiment of the invention, the air impermeable wall contiguous with the air outlet is flat. 
         [0012]    In one embodiment of the invention, the distance between the inner perforated wall and the outer perforated wall is between 10 millimeters and 30 millimeters. 
         [0013]    In one embodiment of the invention, a first perforated throttling plate or throttling mesh is mounted at a distance of less than millimeters 50 from the air outlet. 
         [0014]    In one embodiment of the invention, a second perforated throttling plate or throttling mesh is mounted at a distance of more than 300 millimeters from the air outlet. 
         [0015]    In one embodiment of the invention, a hydraulic diameter of perforations in the outer perforated wall is less than 3 millimeters. 
         [0016]    In one embodiment of the invention, the perforations in the inner perforated plate are circular. 
         [0017]    In one embodiment of the invention, the perforations in the outer perforated plate are circular. 
         [0018]    In one embodiment of the invention, the inner perforated wall and the outer perforated wall are flat. 
         [0019]    In one embodiment of the invention, the inner perforated wall and the outer perforated wall have a circular profile. The circular profile may be in the direction perpendicular to the incoming flow of air through the air outlet. 
         [0020]    In one embodiment of the invention, between the inner perforated wall and the outer perforated wall is mounted at least one annular support plate to maintain the distance from the inner perforated wall to the outer perforated wall and to limit a distortion of the pressure equalization chamber. 
         [0021]    In one embodiment of the invention, the inner perforated wall and the outer perforated wall have a semicircular profile. The semicircular profile may be in the direction perpendicular to the incoming flow of air through the air outlet. 
         [0022]    In one embodiment of the invention, the first perforated throttling plate or throttling mesh, or the second perforated throttling plate or throttling mesh, comprises at least one of a perforated metal plate, a perforated plastic plate, a metal mesh, a plastic mesh, a fiber mesh, a fabric mesh and a fiber mesh. 
         [0023]    The embodiments of the invention described herein may be used in any combination with each other. Several or at least two of the embodiments may be combined together to form a further embodiment of the invention. An air distribution device to which the invention is related may comprise at least one of the embodiments of the invention described hereinbefore. 
         [0024]    It is to be understood that any of the above embodiments or modifications can be applied singly or in combination to the respective aspects to which they refer, unless they are explicitly stated as excluding alternatives. 
         [0025]    The benefits of the invention are related to improved air distribution with diminished noise induced by the air distribution device. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0026]    The accompanying drawings, which are included to provide a further understanding of the invention and constitute a part of this specification, illustrate embodiments of the invention and together with the description help to explain the principles of the invention. In the drawings: 
           [0027]      FIG. 1  illustrates an air distribution device in one embodiment of the invention; 
           [0028]      FIG. 2  illustrates an air distribution device having a rectangular profile in one embodiment of the invention; and 
           [0029]      FIG. 3  illustrates an air distribution having a semicircular profile in one embodiment of the invention. 
       
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
       [0030]    Reference will now be made in detail to the embodiments of the present invention, examples of which are illustrated in the accompanying drawings. 
         [0031]      FIG. 1  illustrates a cross section of an air distribution device  100  in one embodiment of the invention. Air distribution device  100  is connected to a supply air duct  150  that provides ventilation air as supply air to air distribution device  100 . Air distribution device  100  comprises an air outlet plate  101  which has an air outlet opening  105  to which supply air duct  150  may be detachably mounted. The air outlet plate may be flat. On an opposite side of air distribution device  100  facing air outlet plate  101  there is an air impermeable plate  103  which may be flat. Air distribution device  100  has an interior space  108 , which acts as an air distribution chamber for supply air. Interior space  108  may be bounded from sides by at least one air impermeable sidewall such as sidewall  104  and sidewall  102  illustrated in  FIG. 1  and a perforated outer front plate  110  which acts as an air distribution surface for supply air into a room to be ventilated. In one embodiment of the invention, there is no air impermeable sidewall, but instead perforated outer front plate  110  has a circular profile. Front plate  110  may also be bent to have a semicircular, that is, a U-profile, which is why there may be only one air impermeable sidewall in one embodiment of the invention. A sidewall covering interior space  106  from view is not shown in  FIG. 1  for illustrative purposes. Behind outer front plate  110  in the direction of incoming supply air is mounted a perforated inner front plate  112  which is parallel to the outer front plate  110  and has similar profile as outer front plate  110 . 
         [0032]    Between inner front plate  112  and outer front plate  110  there is arranged a pressure equalization chamber  116  which is separated from interior space  106  by inner front plate  112 . The distance Wf between inner front plate  112  and outer front plate  110  is between 10 mm and 30 mm. In case the distance Wf exceeds significantly 30 mm air starts to flow between inner front plate  112  and outer front plate  110 . Perforated inner front plate  112  and perforated outer front plate  110  may have uniformly spaced holes or other type of perforations such as rectangles Inner front plate  112  has a larger hole-free area, that is, perforation-free area than outer front plate  110 . The hydraulic diameter of perforations in outer front plate may be less than 3 mm. If perforations in outer front plate  110  are circular their diameter may be less than 3 mm. The space between inner front plate  112  and outer front plate  110  may also be divided into at least two partitions or zones. The partitioning is achieved by at least one plate that is arranged between inner front plate  112  and outer front plate  110 . 
         [0033]    The space between inner front plate  112  and outer front plate  110  serves as a pressure compensation chamber for the air pressure gradient between interior space  106  and outside room air. Supply air duct  150  is illustrated in  FIG. 1  to be perpendicular to inner space  108  and inner front plate  112 . 
         [0034]    Interior space  108  is further divided into at least two air chambers with at least one air permeable separating plate perpendicular to inner front plate  112  and the at least one sidewall such as sidewall  104 . The at least one air permeable separating plate is substantially perpendicular to an incoming flow of ventilation air from supply air duct  150 . The at least one air permeable separating plate may be substantially parallel to air outlet plate  101  and substantially parallel to air impermeable plate  103 . The at least one air permeable separating plate acts as a throttling plate which slows down flow of air from supply air duct  150  across interior space  108 , which causes a reduction of noise in air distribution device  100 . The at least one air permeable separating plate is air permeable by virtue of perforations or holes. There is at least a first air permeable separating plate  132  which is mounted within a distance H 1  of less than 50 mm from air outlet plate  101  or a point of contact between air outlet plate  101  and inner front plate  112 . A first air chamber  120  is bounded by first air permeable separating plate or mesh  132  from the rest of interior space  108 . First air chamber  120  is located in an interior space between air outlet plate  101  and first air permeable separating plate or mesh  132 . In one embodiment of the invention, there is a second air permeable separating plate or mesh  142  which is mounted within a distance H 2  of over 300 mm from air outlet plate  101  or a point of contact between air outlet plate  101  and inner front plate  112 . Thus, in this embodiment there is a second air chamber  130  bounded by first air permeable separating plate or mesh  132  and second air permeable separating plate or mesh  142 . The rest of interior space not included in first air chamber  120  or second air chamber  130  may also be referred as third air chamber  140 . 
         [0035]    The flow of air through opening  105  in air outlet plate  101  is illustrated with arrow  10 . Air flow through first air permeable separating plate is illustrated with arrow  11 , whereas air flow through second air permeable separating plate  142  is illustrated with arrow  12 . Due to the throttling effect of first air permeable separating plate or mesh  132  part of air flowing through opening  105  in air outlet plate  101  is deflected to flow parallel to first air permeable separating plate or mesh  132 , as illustrated with arrow  13 . Similarly, second air permeable separating plate or mesh  142  causes part of air flowing through first air permeable separating plate or mesh  132  to be deflected as a flow parallel to second air permeable separating plate or mesh  142 , as illustrated with arrow  14 . Air flow deflected by air impermeable plate  103  is illustrated with arrow  15 . Pressure-equalizing airflows in pressure equalization chamber  116  are illustrated with arrows  16 ,  17  and  18 . Pressure equalization chamber  116  causes a uniform flow of air through whole outer front plate  110  as illustrated with vertical arrows in  FIG. 1  such as arrows  19  and  20 . 
         [0036]    In one embodiment of the invention, an air permeable separating plate or mesh may be, for example, at least one of a perforated metal plate, a perforated plastic plate, a metal mesh, a plastic mesh, a fiber mesh, a fabric mesh and a fiber mesh. The air permeable separating plate or the mesh throttles air flow and may be referred to as a throttling plate or a throttling mesh. 
         [0037]    In one embodiment of the invention, the small hydraulic diameter of the perforations in the outer perforated wall which may be less than 3 millimeters causes ventilation air through outer front plate  110  to form a plurality of small jets of air into which room air is induced. Thus, velocity of air from air distribution device  100  is reduced. 
         [0038]    In one embodiment of the invention, the interior space  108  is provided supply air via two supply air ducts. There may, for example, be a second opening for supply air in at least one of air outlet plate  101 , plate  103 , sidewall  102 , sidewall  104  and sidewall  106 . 
         [0039]      FIG. 2  illustrates an air distribution device having a rectangular profile in one embodiment of the invention. 
         [0040]    In  FIG. 2  there is illustrated an air distribution device that is structurally similar to air distribution device  100  illustrated in  FIG. 1 . The rectangular profile of air distribution device  100  is seen in the direction perpendicular to the airflow from a supply air duct to an internal space of air distribution device similar to internal space  108  in  FIG. 1 . Rectangular profile comprises sidewalls  102 ,  104  and  106  as well as inner front plate  112 . Sidewall  106  is shown only partially. 
         [0041]      FIG. 3  illustrates an air distribution device having a semicircular profile in one embodiment of the invention. 
         [0042]    The air distribution device illustrated in  FIG. 3  is functionally similar to air distribution device illustrated in  FIG. 1 . 
         [0043]    In  FIG. 3  outer front plate  110  is bent to a semicircular shape so that internal space  108  is bounded by outer front plate  110  and air impermeable sidewall  106  in transverse direction with respect to supply air flow coming into air distribution device  100 . Internal space  108  is also bounded an air supply plate  101  which has opening  105  to which air supply duct  150  is mounted. Opposite to air supply plate  101  is air impermeable plate  103 . Also inner front plate  112  is bent to a semicircular shape. The distance between outer front plate  110  and inner front plate  112  is arranged to be Wf, that is, between 10-30 mm. Thus, a radius of a semicircle formed by inner front plate  112  is smaller than a radius of semicircle formed by outer front plate  110  by Wf. As in  FIGS. 1 and 2 , the space between inner front plate  112  and outer front plate  110  acts as a pressure equalization chamber. There may be at least one support plate mounted between outer front plate  110  and inner front plate  112  such as support plate  114 , which keeps outer front plate  110  and inner front plate  112  at a uniform distance from each other and, thus, ensures that a shape of the pressure equalization chamber is not distorted. Support plate  114  has an outer edge which is fixed to outer front plate  110  and an inner edge which is fixed to inner front plate  112 . 
         [0044]    The embodiments of the invention described hereinbefore in association with the  FIGS. 1 ,  2  and  3  and the summary of the invention may be used in any combination with each other. At least two of the embodiments may be combined together to form a further embodiment of the invention. 
         [0045]    It is obvious to a person skilled in the art that with the advancement of technology, the basic idea of the invention may be implemented in various ways. The invention and its embodiments are thus not limited to the examples described above, instead they may vary within the scope of the claims.