EP0507756A1

EP0507756A1 - A distribution plate

Info

Publication number: EP0507756A1
Application number: EP92850071A
Authority: EP
Inventors: Bertil Lars Gustav Liljegren; Anders Göte Lennart Svensson
Original assignee: Stifab AB
Current assignee: Stifab AB
Priority date: 1991-04-03
Filing date: 1992-04-02
Publication date: 1992-10-07
Anticipated expiration: 2012-04-02
Also published as: NO921290D0; DE69201505D1; FI100134B; SE502480C2; FI921246A; SE9100975D0; NO173956C; SE9100975L; DK0507756T3; NO173956B; NO921290L; FI921246A0; EP0507756B1; DE69201505T2

Abstract

The present invention relates to a distribution plate for low-velocity type supply air terminal devices which include a distribution chamber which functions to receive air flowing from a delivery channel and which includes a wall which extends parallel with the inflowing air and which is provided with a circular hole, wherein said air exits from the distribution chamber in a divergent flow pattern, and which distribution plate has means for mounting the plate in the circular holes and is provided with one or more openings. The inventive distribution plate is characterized in that one side of the plate is provided with air deflecting devices which protrude out from the plane of the plate. The air deflecting devices have an eyelid-like shape and cover and enclose from between about one third to about one half of the area of respective openings. The openings and the air deflecting devices together form a flow path which is adapted to deflect the air passing through the plate openings in an essentially loss free fashion. The openings and associated air deflecting devices are formed so that the air will exit through all openings in the plate in one and the same direction.

The invention also relates to the use of the inventive distribution plate in low-velocity type air supply terminal devices so as to achieve both horizontal and oblique flow of the exiting air.

Description

The present invention relates to an air distribution plate for low-speed type supply air terminal devices which include an air distribution chamber which functions to receive air flowing from a delivery channel and which has a wall which extends parallel with the inflowing air and which is provided with circular holes, wherein said air exits from the distribution chamber in a divergent flow pattern. The distribution plate has means for mounting the plate in the circular hole in said wall and the plate is provided with one or more openings.
One example of a low-speed supply air terminal device is described and illustrated in our earlier publication SEA-9000289-0. In the case of this device, the aforesaid wall is provided with fixed openings, wherein some of the openings function to cause the exiting air to pass obliquely rearwards in relation to the main direction of the exiting air flow, while other openings function to cause air to exit in a direction which is generally at right angles to the main flow direction of the exiting air. The openings are disposed in a mutually repetitive and consecutive pattern along the flow direction.
Other proposals for achieving a desired pattern of air flow from similar devices are known to the art. For example, it is proposed in DE-B-11 24 658 that a perforated wall through which air is intended to exit in a desired pattern is configured with slightly inclined parts and that the openings are formed in these inclined parts. In this way it is possible to compensate for the velocity of air flow, which otherwise gives rise to an oblique component in the exiting air flow, so as to result in an exiting air flow which passes generally perpendicular to said wall, which corresponds to the desired flow velocity according to the publication.
To the same end, there is proposed in SE-B-8105785-3 a distribution plate in the form of a perforated wall which functions to deflect a main flow of air into a plurality of secondary flows which exit on the other side of the wall via said perforations transversely to the direction of the main air flow. In this case, the perforated plate is comprised of a profiled sheet metal plate or disc provided with profiled parts which extend transversely to the direction of main air flow adjacent one or more perforations and therewith form flow deflecting means.The perforated wall obtains a saw-tooth or stepped configuration. In the case of this known device, it is essential that the deflectors which function to deflect the flow through the perforations are located downstream of the perforations and immediately adjacent thereto and at a distance therefrom which must at least be substantially smaller than the diameters of the perforation.
It is also known to use in air supply terminal devices, wall structures which are provided with circular openings into which loose deflectors of the kind described in DE-A1-29 41 276 are fitted. These deflectors are configured and mounted so that the air exiting from all of openings will be deflected generally perpendicular to the wall and therewith horizontally into the room.
US-A-2 909 112 describes an "air diffusor" which is placed in a closed ventilation duct, and which may be constructed so as to be rotatably mounted in circular openings. This air diffusor is provided with openings and deflector blades which face in towards the duct and partially cover the openings. The openings and the deflector blades associated therewith are arranged in groups at angles to one another, so that the air will be spread in all directions.
When air is delivered to a room with the aid of a supply air terminal device, problems such as the sensation of drafts (floor drafts, etc) can occur when the air is badly distributed. Among other things, this is due to the appearance of the vertical flow pattern, where the shortest possible so-called near zone or near field is desired. By near zone is meant the zone nearest the terminal device within which the sensation of a draft is first felt, and technically it is defined by the distance from the device at which the velocity of the air is 0.2 m/s. The horizontal flow pattern is also significant in obtaining the shortest possible near zone in all directions of air flow. Distribution of the air also affects the distribution of temperature within the occupied zone, and consequently it may also be of interest in this connection to measure the temperature in occupied zones. According to one ISO-standard the temperature of an occupied zone is measured at floor level (0.1 m above the floor surface) and also at a height of 1.1 m above the floor surface. In this case, the difference in temperatures should be as small as possible and preferably less than 3°C, in order to provide a comfortable atmosphere. It has been found that the behaviour of the air as it leaves the terminal device has a primary influence on the resultant near zone and temperature difference. An optimal result is obtained when the air is first caused to move upwards and then immediately downwards, as close to the terminal device as possible, preferably in the absence of any horizontal velocity component, and is then allowed to spread softly over the surface of the floor, after having lost momentum as a result of impact with the floor, while displacing stale air present in the room. The fresh incoming air should not be allowed to mix with the contaminated stale air to be evacuated upwards in the room.
The need for a near zone is not as pronounced in industrial buildings of large volumes and high ventilation requirements, and consequently a horizontal outflow of large quantities of air is often desired in achieving optimal ventilation. This cannot be achieved with the same kind of supply air terminal device as those used in other types of buildings or rooms in which a short near zone is desired and in which the exiting air flow must be directed obliquely upwards.
There is thus a need for a supply air terminal device of such flexibility as to guide the exiting air flow obliquely upwards in those rooms in which a short near zone is desired and which will also provide the horizontal flow of air required in large buildings or rooms which contain large volumes of air, such as industrial buildings and large storage facilities. It is also desirable to be able to control the pattern of the exiting air flow in accordance with the geometry of the room in which the device is installed and also in accordance with the furniture in the room. In the case of the majority of terminal devices known hitherto, it is only possible to vary the flow pattern by changing the velocity of the air, by interchanging the perforated walls or, in the worst case, by changing the supply air terminal device. In many instances, the desired pattern of air flow cannot be obtained even when these measures are taken. At times it is not possible or suitable to carry out the aforesaid measures. For example a supply air terminal device is often installed in a manner which makes it difficult or impossible to reposition the device in the room concerned. Examples of devices which cannot readily be repositioned are those which are built into walls or incorporated in other building structures.
An object of the present invention is to provide a simple solution to the aforesaid problems of improved ventilation flexibility of supply air terminal devices, so that such devices need not be exchanged or repositioned or require other comprehensive and time consuming modification thereto, or reconstruction,in order to satisfy requirements.
The invention is characterized by the features set forth in the following claims.
The inventive distribution plate is thus constructed so that is can be twistably and rotatably mounted in a respective circular hole in the wall of the distribution chamber of the supply air terminal device. The plate is provided with one or more openings and from about onethird to about one half of the area of each opening is covered and enclosed by a respective deflector arranged on one side of the plate, said deflectors being intended to deflect air which flows through the opening or openings, essentially without losses in flow. The deflectors have an eyelid-like configuration and thus protrude outwards from the plane of the plate. The deflectors and opening(s) form passageways for the air through the plate and are constructed so that the air will flow in generally the same direction through all openings. It is important to the function of the plate as a means for distributing and deflecting air in low speed supply air terminal device that each opening is able to deflect the exiting air so that it will flow either horizontally or obliquely downwards, depending on the function desired. Deflection shall take place in the absence of substantial losses in flow, since such losses will result in undesirable turbulence. When the device is to be used in a room where an obliquely outwards flow of exiting air is desired, the plate is mounted with its plain side, i.e. the side which is devoid of eyelid-shaped reflectors, facing towards the distribution chamber. The air will then first flow generally horizontally in through the plate opening or openings, whereafter the lower part of the air flow will be deflected successively upwards and outwards, whereas the upper part of the flow will follow its original course and flow perpendicular to the plane of the plate. When this air later meets the air that was deflected by the deflectors, it will in turn be deflected so as to form an upwardly and outwardly exiting air flow. Similarly, it is necessary that each opening is able to deflect air flowing from the distribution chamber such as to achieve a horizontal air flow in the absence of turbulence when the plate is mounted so that the side of the plate provided with said eyelid-shaped deflectors faces towards the distribution chamber.
By arranging the deflectors in the openings in accordance with the invention, so that they cover and enclose a part of respective openings, said part corresponding to about one third to about one half of the area of said opening, the plate will function to deflect air which passes therethrough in the desired direction, i.e. in an upwards-outwards direction in one position of the plate and in a horizontal direction in the reverse position of the plate, depending on how the plate is mounted in the hole in said wall. This horizontal air flow is achieved with the smallest possible flow losses, therewith avoiding undesirable turbulence at the deflectors, to the greatest possible extent.
In order to deflect the air flow in a manner which is substantially loss free, it is necessary for the air to be able to flow through the openings without essentially being throttled and/or in the absence of any appreciable turbulence. This is achieved by adapting the size of the openings in relation to the size of the deflectors, as described above. Furthermore, the deflectors shall protrude from the plate so as to form an opening, here called a fictive flow opening, which is partly defined by the eyelid-shaped device. The area of the fictive opening is the area that remains for the air to flow through if the area of the opening in the plane of the plate is covered. The fictive flow area is thus measured either at right angles to the plate, which is the case when the deflectors cover about one half of the area of the opening, or at an angle of less than 90° to the plate, when the deflector covers less than one-half of said area.
For the smallest possible throttling of air flow, the sum of the fictive area and the area not covered by the deflecting device shall be substantially equal to the total area of the opening on the opposite side of the plate. When deflection to provide an upwardly and outwardly moving air flow is desired, the flow of air through the plate openings can be described in the following manner. The upper part of the air flowing in through each opening will pass straight forwards without obstruction, until it has passed completely through the opening. The lower part of the air flow will pass in "its" channel of generally constant area while being deflected until the fictive flow opening has been reached. The two parts of the air flow will then be mixed together during deflection of the two air flows, so as to result in an upwardly and outwardly moving air flow.
For the purpose of obtaining the smallest possible flow losses, it is beneficial, in the majority of cases, to configure the deflectors so that when seen against the plate they will have a rounded cross-section, preferably a cross-section of circular-arcuate shape, on the inside of the device which is intended to deflect air. Although circular openings are preferred in the majority of cases, openings of other cross-sectional shapes can be chosen for different purposes. The openings may be arranged in a regular pattern in each distribution plate, for instance with an opening provided in the center of the plate and other openings arranged in a circle around the central opening.
With regard to the configuration of the deflecting devices, it is preferred to arrange each deflector over a respective opening of each separate distribution plate in mutually the same way.
The inventive distribution plate is suited for manufacture as a one-piece structure and can be produced, for instance, by moulding the plate from an appropriate plastic material. Each plate will suitably have a size which will enable it to be mounted in holes having a diameter of about 80 to 90 mm in the case smaller supply air terminal device, and to be mounted in holes of from 120 to 150 mm in diameter in the case of special industrial devices.
The invention also relates to the use of the inventive distribution plate in low-velocity the supply air terminal device. In this regard, each plate may be mounted in the perforated wall of the terminal device in a manner which will enable any desired air distribution pattern for a low-velocity supply air terminal device to be obtained. Thus, each of the plates can be rotated in its wall-mounted position or fully reversed, i.e. so that the side of the plate on which the deflectors are provided either faces towards or away from the distribution chamber, which affords a particularly flexible solution to the problem of air distribution in supply air terminal device. Thus, if the air is desired to exit completely horizontally from the device, the plates are either rotated through 90° from their normal position in which the eyelid-shaped devices facing towards the room to be ventilated cover the lower part of each opening or, as indicated above, are reversed, so that the eyelid-shaped deflecting devices towards the distribution chamber instead of towards the room to be ventilated, as in the normal case.
The invention will now be described in more detail with reference to the accompanying drawing, in which Figure 1 is a side view of an inventive distribution plate, Figure 2 is a front view of a preferred embodiment of the inventive plate, and figure 3 illustrates different forms of opening that can be used with the inventive plate.
Figure 1 illustrates a distribution plate 10 for a low-velocity supply air terminal device . The plate has three rows of openings 11 extending in the transverse direction of the plate. The cross-sectional area of each opening 11 is substantially constant in the transverse direction of the plate. Thus, the opening defining lines in each contemplated cross-section of the plate 10 are generally of equal size, as is shown by an upper line 12 parallel with a lower line 13. In this way there is formed within the plate 10 an opening 11 with the thickness of the plate 10 as its height and the cross-sectional area of the opening 11 as its base,
On one side of the plate 10, in the illustrated case the side turned to the right, a deflecting device 14 is mounted over each opening 11. When seen in a direction towards the plain or flat surface of the plate 10, each device 14 has the same shape as that part of the opening 11 covered by the device. In a direction perpendicular thereto, i.e. along the plane of the plate, each device 14 has an inner wall 15 which is curved so as to deflect air which passes through the opening 11. In the case of the Figure 1 embodiment, this inner wall 15 has a circular-arcuate configuration. Each device forms a flow opening 16 located against the plane of the plate 10 and outside said plane, in the illustrated case at right angles to the plane of the plate 10. As indicated by the broken line 16A, the flow opening defined by the device 14 may also be located in a plane which defines an acute angle with the plane of the plate 10. Each plate 10 is provided with snap-on devices 17 for mounting the plate 10 in a hole in a perforated wall of the supply air terminal device. The snap-on devices are constructed so as to enable the plate 10 to be pressed firmly into the hole without difficulty and to enable the plate 10 to be rotated to a desired position, e.g. a position in which the device 14 is directed horizontally instead of being directed vertically downwards in relation to the incoming air flow, as is normally the case. It must be possible to mount the plate 10 firmly in the wall with the aid of the devices 17, either with the deflectors 14 facing the direction of air flow or vice versa.
Figure 2 illustrates a preferred embodiment of the inventive distribution plate 10, which has circular openings 21 and deflectors 24 in the form of hemispherical shells. The illustrated embodiment also includes four mounting devices 27. Those parts of the plate 10 which are solid are shown in hatch, whereas the visible openings have been left plain.
Figure 3 illustrates conceivable forms of opening 11 other than the preferred circular form shown in Figure 2.

Claims

1. A distribution plate for low-speed type supply air terminal devices which include a distribution chamber which functions to receive air flowing from a delivery channel and which has a wall which extends parallel with the inflowing air and which is provided with a circular hole, wherein said air exits from the distribution chamber in a divergent flow pattern, and which distribution plate has means for mounting the plate in said circular holes and is provided with one or more openings, characterized in that one side of the plate is provided with air deflecting devices which protrude out from the plane of the plate; in that the air deflecting devices have an eyelid-like shape and cover and enclose from between about one third to about one half of the area of respective openings; in that the openings and the air deflecting devices together form a flow path which is adapted to deflect the air passing through the plate openings in an essentially loss free fashion; and in that the openings and associated air deflecting devices are formed so that the air will exit through all openings in the plate in one and the same direction.

2. A distribution plate according to Claim 1, characterized in that when seen in cross-section at right angles to the plane of the plate, the air deflecting devices have a rounded shape, preferably a circular-arcuate shape.

3. A distribution plate according to Claim 1 and Claim 2, characterized in that the openings are circular.

4. A distribution plate according to Claims 1-3, characterized in that the openings are arranged in a regular pattern.

5. A distribution plate according to Claims 1-4, characterized in that the plate is a one-piece structure.

6 The use of a distribution plate according to any one of Claims 1-5, in a supply air terminal device of the low-velocity kind, to achieve a horizontal flow of exiting air, said plate being so turned when mounting the plate in said circular hole that said air deflecting devices will face opposite to the direction of the incoming air flow.

7. The use of the distribution plate according to any one of Claims 1-5 in a supply air terminal device of the low-velocity kind to achieve an oblique flow of exiting air in relation to the plane of the plate, wherein when mounting the plate in said hole, the plate is turned so that the air deflecting devices will face in the direction of the incoming air flow.

8. The use according to Claim 7 for achieving a given, predetermined oblique flow of exiting air, wherein the plate is turned in said hole until the desired flow direction is obtained.