WO2000050819A1

WO2000050819A1 - Air diffusor

Info

Publication number: WO2000050819A1
Application number: PCT/SE2000/000286
Authority: WO
Inventors: Lennart KARLÉN
Original assignee: Asservo Ab
Priority date: 1999-02-12
Filing date: 2000-02-14
Publication date: 2000-08-31
Also published as: SE9900476D0; DE10084109T1; AU2956200A; SE9900476L; SE523772C2

Abstract

The present invention relates to an air spreading device for fresh outdoor air ducts, designed to introduce fresh air into the rooms in a building. The device is designed to be mounted in front of a fresh air duct, which has an opening close to the interior side of a window, preferably in or on a window board below a window and above the opening of a window apparatus, which opening is directed upwards, which air spreading device has a curved surface with openings, through which air jets are spread in a direction, which is perpendicular to the respective opening, the air spreading device being designed to prevent draughts from occurring also at low fresh air temperatures, energy being saved in this way. The curved surface (Y) of the spreading device (1) is substantially completely provided with very small holes or slits, which are smaller than 5mm, the air with a relatively low temperature, preferably 10-18°C, preferably having a flow speed per meter window of about 5-15 1/s per meter window, the introduced fresh air being spread through the openings (0) in several hundred jets, in diverging directions into the room, subsequent to which an admixture into the warm room air will be done at a very short distance from said convex surface (Y).

Description

AIR DIFFUSOR

TECHNICAL FIELD

The present invention relates to an air spreading device, mounted on ducts, designed to introduce fresh outdoor air into a room in a building. The device is mounted in front of a duct for introduced air, which has an opening adjacent the interior side of a window, preferably in or on top of a window board below a window and above the opening of a window apparatus, which opening is directed upwards, which air spreading device has a curved surface with openings, through which air jets are spread in a direction, which is perpendicular to the respective opening, the air spreading device being designed to prevent draughts from occurring also when the temperatures of the introduced air flow are low, energy being saved in this way.

BACKGROUND ART

In the above-mentioned technical field many patent applications have been filed regarding various types of air apparatuses, air spreading units, used to, at the end of an air duct, spread introduced fresh air into a room. SE 9600320 and 354 711 as well as DE 1 215 896 show examples of such aparatuses.

However, so far the problem of admixing introduced fresh air into the warm and stationary room air, without draughts occurring in the living space, has not been solved in a satisfactory way, despite innumerable similar technical solutions .

Several different types of products on the market are provided with i.a. slits and tube shaped openings with a certain length, which guide the air in the desired direction in the room. The purpose is to maintain the impulse of the air flow and reduce the resistance, the pressure drop in the device, in order to reduce the losses in the system.

The ventilation ducts and the window apparatuses are generally mounted in casettes adjacent the window, which window apparatuses are equipped with radiators and cooling coils in order to, by means of a room temperature control, be able to adjust the temperature of the introduced air, before it is blown into the room, the air flow being directed upwards with a high impulse, which means, that the temperature of the introduced air must be kept high in order to prevent the feeling, that draughts occur, e.g. in a work place, when the air passes through the upwardly directed openings of the window apparatus and through the grating, which covers the opening in the casette.

By means of these window apparatuses, which generate an air flow, which flows out below a grating, a screen or the like in the window board, room air is drawn, through co-ejection, through the cooling coils and heat radiators of the window apparatus, noise, which often can be annoyingly high, occurring in the window apparatus and the particle contents in the living area becoming relatively high, when the co-ejected room air rises from the floor level. The driving powers of this secondary flow are created by the primary air flow through an ejector action.

The air from the window apparatus to the rooms is directed upwards and recieves an impulse upwards through an opening in the window board, which usually has a rectangular shape. The air then flows upwards along the window and can, to a certain degree, be controlled by slanting or tilting the grating, the screen or the like, which usually is made of a plate or a plastic material, in various directions of the upwardly directed air flow. Also, the gratings or screens of the window boards may only constitute a visibility screening and a protection against things being dropped into the window apparatus.

The window apparatuses direct with an impulse the air upwards through said grating, along the window and towards the ceiling and subsequently the air flow reaches the space above the living area and flows towards waste air outlet openings, which often are positioned close to the ceiling, which means, that the air usually flows beside and above the living area in the room. In case the air has a high temperature, which is normal, the thermology will give the air an additional lift towards the ceiling and in the living area the air exchange will be low. The primary air movement upwards towards the ceiling generates a vortex in the room, in which old air from the corridor fills the room along the floor, when the door is open, and this old air constitutes a substantial portion of the air in the working place.

In case the temperature of the air flow through the window apparatus is lowered, the air will instead turn aside, when it has reached a certain elevation upwards along the window. The reason for this is, that the weight of the cold air along the window will counteract the impulse upwards and will bring the air downwards towards the floor. Thus, a cool air flow from the window apparatus through the above-mentioned grating will not be mixed with the room air but will cause a feeling of draught and a draught along the floor.

The air speed through the nozzles in a window apparatus is usually high in order to create a negative pressure, required to create a co-ejection of the room air. The high speed results in a high noise level, which sooner or later may develop into annoying sounds, caused by dust and dirt, which have been accumulated in the window apparatus due to the co-ejection of the room air from the floor level and due to the grating, which is open upwards .

Also, it is difficult to clean the window apparatus and consequently the casettes with the window apparatuses will collect dust and other types of dirt, which partially follow the air upwards. This is a sanitary problem, since the window apparatuses in this way actively contribute to keeping the dust particles suspended in the air.

Several other air devices on the market are provided with a perforated surface , which functions as a boundary between the air duct and the room. The perforated surface is then often selected to constitute a surface layer or a portion of the design and is not selected and designed as an active portion of the construction of the device in order to influence the specific aerodynamic properties of the device.

It is difficult in practice to, in a predetermined, particular way, guide the introduced air through a perforated air device without causing a feeling of draught in the living area of the room. The reason for this is, that a special relationship is required between the amounts of the air flows, the size of the air spreading unit, the temperature difference between the introduced air and the room air as well as the size of the admixture zone, which can be accepted, i.e. the distance between the unit and the living area, which in an office room is close to the window wall, since the room normally is equipped with a writing table close to the window. The writing table usually is combined with a table portion at an angle. These pieces of furniture result in, that the working place and then also the living area will be positioned 0,5-2 meters from the window.

BRIEF DISCLOSURE OF THE INVENTION

The purpose of the present invention is to eliminate the above-mentioned inconveniences, when fresh air is introduced through ducts, and to develop a spreading device, which can spread introduced air, which has a substantially lower temperature than what is usual, in an efficient way from a duct close to a window into a room and past a working place, a flow of cold air from the window simultaneously being counteracted and consequently a feeling of draught not being experienced, not even at low temperatures of the introduced air.

In accordance with the invention the above-mentioned problems will be solved by providing the curved surface of the air spreading device substantially completely with very small holes or slits, which are smaller than 5 mm, the air with a relatively low temperature, preferably 10- 18°C, having a small flow speed per meter window, about 5-15 1/s per meter window, the introduced air being spread through the openings in several hundred jets, in diverging directions into the room, subsequent to which an admixture into the warmer room air being obtained at a very short distance from the convex surface.

In accordance with the invention it is possible to mix air masses with different gas properties, due to temperature and speed, in a very efficient and draught- free way.

Also, in accordance with the invention a device is developed , which can be easily applied to different fresh air ducts, e.g. window apparatuses in window boards, and which allows the air flow into the room to be reduced, a pleasant indoor climate being obtained in this way, allows the co-ejection of air around the window apparatus to be reduced, allows finely divided introduced fresh air in several hundred jets to flow into the room and consequently several hundred jets of fresh air of a lower temperature to be mixed with almost stationary room air, the fresh air flowing into the room without draughts occurring but rather the feeling of fresh introduced air being expericenced.

BRIEF DESCRIPTION OF DRAWINGS

Fig. 1 shows a first embodiment of the invention, mounted in a window board with a built-in window apparatus, seen in a lateral cross-section ;

Fig. 2 is a lateral view of the embodiment shown in Fig. 1, mounted in a window board according to Fig. 1 ; and

Fig. 3 is a lateral view of another embodiment of the invention, mounted in a window board.

DESCRIPTION OF PREFERRED EMBODIMENTS

One embodiment of the invention is shown in Fig. 1. In a cross-section it is shown, how a window apparatus 4,5,6 is positioned below a window 2. This apparatus is connected to a ventilation duct 7, which extends along the interior side of the facad wall of the house and is provided with detours to window apparatuses 4,5,6 below the windows. The window apparatus can be provided with radiators and cooling coils in order to, when the room temperature is to be controlled, be able to control the temperature of the introduced air, before it is blown into the room. The air blown into the room is directed upwards by means of nozzles 5 and is then fed through an opening 3 in a window board B. Above opening 3 an air distributor 1 is mounted, designed to distribute or spread the introduced air from window apparatus 4,5,6 upwards past window 2 and past the work place, which usually is positioned close to the window, a portion of the table being placed at an angle to the window 2. Air distributor 1 comprises a perforated grate having very small openings 0 with a size of a few millimeters, the surface of the grate being curved and convex, seen from the room, which grate is shown in more detail in Fig. 2, in which the air distributor is shown in a lateral and vertical view and it is shown, how air flows 9 are blown into the room at an angle of 90° from each separate hole in the curved surface.

In Fig. 3 air distributor 1 is shown in a lateral view in the same way as in Fig. 2, but now it has an assymetrical shape, its largest height, shown by arrow 10, being displaced towards window 2. At the areas of the air distributor close to the window a large opening 8 is provided, which allows a reduced flow resistance and consequently a larger air flow per surface unit than through the remaining portion of air distributor 1. Since this flow through opening 8 is directed towards window 2, it provides a greater counteraction against cold air flow or draughts from the window.

The curved shape of air distributor 1 allows the introduced air to be spread over a large angle into the room, since the air flow through the holes is directed at right angles from the surface of the air distributor. The perforation consisting of many small openings in the surface is a prerequisite of an admixture of a cold introduced air flow into a warm air in the room, several hundred jets of cold introduced air being spread into the warmer air in the room. It is most advantageous, that the introduced air can be kept at a low temperature. The heat excess in a normal office room is removed from the room together with the ventilation flow and the introduced air can be centrally heated through the recovery of heat from the waste air. This is sufficient to heat the introduced air, even if the efficiency of the recovery is limited. The result will be a ventilation system, which does not require any addition of primary heat to the rooms or the building. No joint ejection of room air through the heat radiators and the cooling coils is required any more. This air path can be closed in the existing air ducts and also reduces a possible cooling requirement during the hot season, when not heated exterior air can be introduced and spread according to the invention past the work place and into the room.

The spreading pattern of the introduced air can be varied by changing its temperatures. The heating sources on the work table as well as the heat of the bodies of people in the room make the air rise towards the ceiling, which air brings along impurities such as carbon dioxide, odors, moisture etc. The dust from textiles or the like settles towards the floor and low horizontal surfaces and consequently the cleaning of the room will gradually reduce the presence of dust in the room. The air in the room will become substantially free from particles at the breathing height in the room. The waste air will often have a temperature of 22-25°C, when it reaches a central heat exchanger unit and consequently no extra heat is required to heat the introduced air, which generally will have a temperture of 10-18°C, which is substantially lower than the usual temperatures of the introduced air via window apparatuses, which often have a temperature of up to 25-30°C. Consequently the energy cost can be reduced to a minimum. The air spreading device functions according to a few different physical principles, of which a system has been made in order to achieve an efficient functioning. The purpose is to admix a flow of introduced air having a low temperature into a room air mass, which is not moving and has a higher temperature . The admixture preferably is to be carried out quickly. According to the invention the admixture is to be carried out within an area very close to the perforated discharge surface.

According to the invention the introduced air flow will be slowed down by means of a surface having a certain small flow resistance. This surface constitutes the limiting surface of a closed geometrical body, into which the air flows. The flow resistance in the surface results in a positive pressure in said body. According to Bernoulli's theorem the pressure will be evenly spread against the limiting surfaces of the body. The positive pressure in the body drives a secondary flow out through all the openings in the limiting surface, to the same extent through all the openings. The number of the openings is several hundred. Around each secondary jet a turbulent zone is formed, in which air from the air mass is admixed with the air flow and the impulse of the air flow is reduced. At the same time the volume flow in the core of the secondary flow is reduced according to known flow dynamics. This means, that the intensity of the core flow is reduced as a function of the distance from the opening and will have completely ceased at a certain distance. In this way the introduced air has been completely admixed into said stationary air mass. Due to an efficient admixture also an air flow with a low temperature can be introduced to a room without the appearance of draught discomforts. By varying the geometrical design of the air spreading device the air mixture can be guided in a predetermined direction through the air mass, since each secondary air jet leaves the limiting surface of the air spreading device in a direction, which is perpendicular to it (Bernoulli's theorem) . Thus, the holer, do not need any duct length in order to guide the air in a predetermined direction. Thus, the envelope surface can be very thin and the envelope surface of the spreading device can be shaped in such a way, that it exposes the major partial surface in that direction, in which in the first place the air is supposed to stream. That amount of secondary jets, which then results in a weak impulse in the same direction, allows the mixed air mass to move in the first place perpendicular to this partial surface.

Due to the fact, that new fresh air continuously is being introduced into the room , the air mixture will be moving slowly towards the waste air exhaust valves . Heat sources heat the air mixture, which rises. The air mixture will then be drawn towards heat sources in the room, e.g. human beings present in the room.

Thanks to the invention the living area of human beings will in the first place be ventilated in the room. Consequently the ventilation efficiency will be improved.

Claims

CLAIMS :

l.An air spreading device for fresh outdoor air ducts , which are used to introduce fresh air into rooms in a building, the device being designed to be mounted in front of a fresh air duct, which has an opening close to the interior side of a window, preferably in or on a window board below a window, which air spreading device has a curved surface with openings, through which air jets are spread in a direction, which is prependicular to the respective opening, the air spreading device being designed to prevent the ocurrence of draughts also when the temperatures of the introduced fresh air are low, energy being saved in this way,

c h a r a c t e r i z e d in that the curved surface (Y) of the air spreading device (1) substantially completely is provided with very small holes or slits (0), which are less than 5 mm, the fresh air with a relatively low temperature , preferably 10-18°C, preferably having a flow per meter window of about 5-15 1/s per meter window and the introduced fresh air being spread through the openings (0) in several hundred jets, in diverging directions into the room, subsequent to which an admixture of the fresh air into the warmer room air is done at a very short distance from the convex surface (Y) .

2.An air spreading device according to claim 1, c h a r a c t e r i z e d in that said curved surface (Y) is designed in such a way, that the highest point on the curved surface is positioned on that portion of the spreading device, which is positioned close to the surface of the window (2).

3.An air spreading device according to claim 2,

c h a r a c t e r i z e d in that said curved surface (Y) consists of several plane surfaces, which are connected to each other with an angle beteen them.

4.An air spreading device according to claim 2,

c h a r a c t e r i z e d in that in the curved surface (Y) at least one comparatively large hole or slit (8) is positioned in that portion, which faces the window (2) .