Downdraft extractor hood with flat channel arrangement

Abstract

The invention relates to a flat duct arrangement (1) for a downdraft extractor hood (100), wherein the flat duct arrangement (1) has a first duct section (2) for connection to a downdraft extractor hood (100) and a second duct section (3) for connection to at least one recirculation outlet (200), characterized in that the flat duct arrangement (1) has a Y-shaped flat duct section (4) in the direction of flow from the first duct section (2) to the second duct section (3) with an air inlet (5) facing the first duct section (2) and two air outlets (6) facing the second duct section (3).

Description

[0001] The invention relates to an arrangement comprising a downdraft extractor hood and a flat duct arrangement, wherein the flat duct arrangement has a first duct section for connection to a downdraft extractor hood and a second duct section for connection to at least one recirculation outlet. Such a flat duct arrangement is described in DE 10 2015 103 034 A1. A recirculation outlet is known from DE 10 2017 109 986 B4. Another flat duct arrangement for a downdraft extractor hood is shown in DE 10 2018 113 818 B9. Duct arrangements for extractor hoods are also known from DE 20 2007 005757 U1, DE 91 03 108 U1, DE 10 2008 050723 A1 and DE 36 15 476 A1. Flat ducts are described in DE 20 2006 006756 U1. A guideline for the design of duct systems is published by McGill et al.: "The Fundamentals of Duct System Design", December 31, 2003.

[0002] Using existing flat duct systems, a downdraft extractor hood, for example, can be fluidically connected via a duct system to a recirculation outlet installed in the base of a kitchen cabinet for extracting cooking fumes from a hob. The recirculation outlet represents the greatest flow resistance in the flat duct system. Due to the often very low base heights, the air outlet area of ​​the recirculation outlet cannot be arbitrarily increased to reduce flow resistance. In typical installation situations, the maximum height of the recirculation outlet in the base of a kitchen cabinet is often limited to 60 mm.

[0003] The object of the invention is therefore to further develop a flat duct arrangement of the type described above in such a way that it has the lowest possible flow resistance and allows energy-efficient operation of a downdraft extractor hood.

[0004] This problem is solved by an arrangement having the features of claim 1. The dependent claims each relate to advantageous embodiments of the invention.

[0005] Accordingly, the flat duct arrangement is designed to include a Y-shaped flat duct section running from the first duct section to the second, with one air inlet facing the first duct section and two air outlets facing the second duct section. This Y-shaped section is designed to split the volume flow from the downdraft extractor hood into two partial flows and to change the cross-sectional area. The two air outlets of the Y-shaped flat duct section each terminate in a 90° elbow. The inlet cross-section of the air inlet and both outlet cross-sections of the air outlets of the Y-shaped flat duct section are arranged in a horizontal plane. The outlet cross-section of the 90° elbow is arranged in a vertical plane.Thus, the 90° pipe bend is arranged at a transition of the flat duct arrangement, in which the flat duct arrangement is diverted from a vertical course in the direction of flow for the extraction of vapors from the hob into the base area of ​​a piece of furniture to a horizontal course in the direction of flow for the passage of vapors through the base of the piece of furniture.

[0006] The arrangement according to the invention thus allows the second channel section to be designed in two parts, for example, comprising two fluidically separated fluid channels, in particular flat channels. The fluid channels can have a combined cross-section that is larger than the cross-section of the first channel section. Furthermore, the fluid channels, if designed as flat channels, can have a smaller dimension in one dimension, for example, in the vertical direction, compared to single-piece flat channels, and yet still provide a sufficient or even a larger total opening cross-section compared to arrangements known from the prior art.

[0007] The two air outlets facing the second duct section can be connected directly or via a fluid channel, such as a flat duct, to separate recirculation outlets, or to a single recirculation outlet. Given the limited height available due to the building structure, this wider outlet can cover both air outlets or the outlets of the fluid channels connected to it. In both cases, the air outlet area of ​​the recirculation outlets can be increased, thus reducing pressure loss. This, in turn, allows the flat duct arrangement, and especially the connected downdraft extractor hood, to operate energy-efficiently due to the reduced flow velocities.

[0008] The two air outlets facing the second duct section can be arranged horizontally side by side and lead directly or indirectly into the same recirculation outlet or into two separate recirculation outlets. If the two air outlets lead into the same recirculation outlet, the recirculation outlet can be correspondingly wider, given a limited height due to structural constraints. If the two air outlets facing the second duct section lead into separate recirculation outlets, the recirculation outlets can be arranged directly next to and adjacent to each other, or at a distance from one another.

[0009] If the air outlets facing the second duct section are each fluidically connected to the same recirculation outlet or to separate recirculation outlets via a separate flat duct, the flat duct can, for example, be designed as the duct described in EP 3 401 613 B1.

[0010] The second duct section can have two fluidically separated sub-duct sections downstream of the Y-shaped flat duct section. These fluidically separated sub-duct sections can each be designed as a flat duct and are preferably arranged horizontally side by side. They can be spaced apart from each other or arranged directly adjacent to one another. The two sub-duct sections can open into the same recirculation outlet or into separate recirculation outlets. For example, the two sub-duct sections can have the same flow cross-section and preferably the same cross-sectional area. Particularly preferably, the two sub-duct sections are identically designed so that they generate the same flow resistance.

[0011] The two partial duct sections can each lead into a recirculation outlet, whereby the recirculation outlet of the two partial duct sections is the same recirculation outlet and extends as a continuous recirculation outlet over the outlet cross-sections of both partial duct sections.

[0012] The recirculation outlet can have a recirculation filter or be a recirculation filter itself. Accordingly, the two duct sections can lead to the same recirculation filter or to separate recirculation filters. The recirculation outlet or the recirculation filter can have an exhaust grille on its outer surface, for example, a louvered grille with horizontal air outlet louvers.

[0013] The two duct sections can terminate in different recirculation outlets, preferably spaced apart by more than the horizontal width of one of the two duct sections. Such embodiments allow for the recirculation outlets to be positioned at distances from each other, for example in the base of different kitchen cabinets, even in installation situations where there is insufficient space to arrange a horizontally wide recirculation outlet or several recirculation outlets side by side, thus achieving better space utilization.

[0014] At least one of the two duct sections can be designed, at least partially, as a flexible duct, for example, a flex duct, with at least one variable radius of curvature. This measure also contributes to the flexible connection of the recirculating air outlets, which are arranged variably according to the site-specific boundary conditions, to the flat duct arrangement.

[0015] The length of the first channel section can be shorter in the flow direction than the length of the second channel section in the same direction. The length of the first channel section can preferably be as short as structurally possible in order to maximize the length of the second channel section. Due to this division of the second channel section into two, it offers greater structural flexibility with regard to widening the channel cross-section to reduce flow resistance.

[0016] The duct length of the first duct section, from a connection of the first duct section for a downdraft extractor hood to the Y-shaped flat duct piece, can be less than the duct length of the second duct section, from a connection of the second duct section for a recirculation outlet to the Y-shaped flat duct piece.

[0017] The inlet cross-section of the air intake and both outlet cross-sections of the air outlets of the Y-shaped flat duct section can be arranged in parallel planes to each other. The two outlet cross-sections of the air outlets of the Y-shaped flat duct section can be arranged in the same plane.

[0018] The 90° pipe bend can have at least one projection on its outer radius, which has a horizontal bearing surface. The projection can be rib- or plate-shaped. The horizontal bearing surface can be aligned with the outer surface of the outlet cross-section of the 90° pipe bend on a side of the 90° pipe bend facing away from the Y-shaped flat duct section. The 90° pipe bend is thus prepared to support the flat duct assembly, in particular a vertically running duct section, and thereby mechanically relieve the connection of the flat duct assembly to the downdraft extractor hood.

[0019] The Y-shaped flat duct section, with its two air outlets, can each connect to a 90° pipe bend via a reducer. The reducer can connect to one of the outlets of the Y-shaped flat duct section with a first flat duct connection cross-section and to the 90° pipe bend with a second flat duct connection cross-section. At least one shorter side of the first flat duct connection cross-section can have a larger dimension than a shorter side of the second flat duct connection cross-section.

[0020] The sum of the cross-sectional areas of the air outlets of the Y-shaped duct section can be larger than the cross-sectional area of ​​the air inlet of the Y-shaped duct section. Preferably, the sum of the cross-sectional areas of the air outlets can be at least 20% larger than the cross-sectional area of ​​the air inlet.

[0021] The air outlets and preferably also the air inlet of the Y-shaped flat duct section can each have a rectangular cross-section, with an aspect ratio of the cross-section of the air inlet preferably being between 1:2.2 and 1:2.5.

[0022] If the second channel section downstream of the Y-shaped flat channel section comprises two fluidically separated sub-channel sections with rectangular cross-sections, these can be arranged horizontally opposite each other, adjacent, or spaced apart, with their shorter sides facing each other. The aspect ratio of the combined cross-sections of the sub-channel sections can be between 1:3.5 and 1:4.5, and preferably 1:4. The combined cross-sections can thus form a total cross-section composed of the two cross-sections of the sub-channel sections, with the sub-channel sections being joined via their shorter sides to form a continuous rectangular cross-section. The dimensions of this combined cross-section are determined, on the one hand, by the dimensions of the shorter sides of the sub-channel sections and, on the other hand, by the sum of the dimensions of the longer sides of the cross-sections.

[0023] The air outlets and the air inlet can each have a rectangular cross-section, wherein a height of the respective cross-section, which runs perpendicular to a width of the respective cross-section, is less than the width.

[0024] The ratio between the height of the air inlet cross-section and the heights of the air outlet cross-sections can be at least 3:2.

[0025] The Y-shaped flat duct section can have a divider with two divider walls diverging in the flow direction, by which the volume flow entering through the air inlet is divided into two partial volume flows. The divider and its divider walls can be arranged symmetrically to a center line of an inlet cross-section of the air inlet of the Y-shaped flat duct section.

[0026] The two divider walls can abut each other on the air inlet side and diverge from each other at an acute angle in the direction of flow.

[0027] The flat channel arrangement can have a hydraulic diameter of at least 8 cm and particularly preferably a hydraulic diameter of at least 8.5 cm.

[0028] A division of the volume flow into two equal partial volume flows is particularly preferred. The outlet cross-sections of the air outlets facing the second duct section of the Y-shaped flat duct can have a maximum duct height of 60 mm, thus enabling installation in the base of a piece of furniture with a particularly low base height.

[0029] The Y-shaped flat duct section is particularly preferably arranged closer to a connection point for a downdraft extractor hood than to a connection point for a recirculation outlet in the direction of flow of the flat duct arrangement, because an early division of the volume flow can lead to an overall reduction in the flow resistances of the duct arrangement.

[0030] Further details of the invention are explained with reference to the figures below. These show: Fig. 1 a flat duct arrangement with connected downdraft extractor hood and recirculation outlet according to the prior art; Fig. 2 a flat duct arrangement according to the prior art as well as two embodiments of the flat duct arrangement according to the invention; Fig. 3 an installation situation of an arrangement according to the invention in a perspective view; Fig. 4 the embodiment according to Fig. 3 in the side view; Fig. 5 an exploded view of an arrangement consisting of a Y-shaped flat duct section according to the invention with a reducer and 90° pipe bend attached thereto; and Fig. 6 a detailed view of an embodiment of a Y-shaped flat duct section according to the invention.

[0031] The Fig. 1 Figure 1 shows a flat duct arrangement 1 according to the prior art. This arrangement has a vertical first duct section 2, via which the flat duct arrangement 1 is connected to a downdraft extractor hood 100. The flat duct arrangement 1 further has a horizontal second duct section 3, via which the flat duct arrangement 1 is connected to a recirculation outlet 200 designed as a recirculation filter. The first and second duct sections 2, 3 are connected to each other via a 90° elbow 7. At least the first and second duct sections 2, 3 are designed as flat ducts 300, which have a substantially rectangular duct cross-section. A suitable flat duct is described, for example, in EP 3 401 613 B1. A suitable elbow 7 is shown, for example, in EP 1 788 259 B2. A recirculating air outlet 200 designed as a base ventilation box is described in DE 10 2017 109 986 B4.

[0032] The Fig. 2 shows, in comparison, a flat duct arrangement 1 according to the state of the art (far left in the illustration according to Fig. 2 ) and two embodiments of a flat channel arrangement 1 according to the invention (center and right in the view according to Fig. 2 Accordingly, the flat duct arrangements 1 according to the invention have a Y-shaped flat duct section 4 in the flow direction from the first duct section 2 to the second duct section 3. The Y-shaped flat duct section 4 has an air inlet 5 facing the first duct section and two air outlets 6 facing the second duct section 3. The opening cross-sections of the air inlet 5 and the air outlets 6 are arranged in parallel planes to each other, with the air outlets 6 preferably being arranged in the same plane, respectively, with respect to the opening cross-sections of the inlet 5 and the outlets 6. The air outlets 6 open into a reducer 12, by which the flat duct cross-section of the air outlets 6 is reduced, particularly in its height, to a cross-section of the two partial duct sections 3.1, 3.2. The reducers 12 each lead into a 90° pipe bend 7, to which one of the sub-channel sections 3.1, 3.2 is connected downstream.

[0033] In the embodiments according to the invention, the second channel section 3 is divided into a first sub-channel section 3.1 and a second sub-channel section 3.2. In particular, the sum of the cross-sectional areas of the two sub-channel sections 3.1, 3.2 is larger than the cross-sectional area of ​​the first channel section 2, so that the volume flow guided through the flat channel arrangement 1 encounters less flow resistance in the region of the second channel section 3 compared to the first channel section 2. Accordingly, it can be provided that the Y-shaped flat channel section 4 is arranged as far forward as possible in the flow direction, thus making the first channel section 2 as short as possible. The two in Fig. 2 The embodiments of the invention shown differ in particular in that, in the central embodiment, the two partial channel sections 3.1, 3.2 open into the same recirculation outlet 200, which is designed as a recirculation filter. Compared to the recirculation outlet 200 of the embodiment according to the prior art, this outlet can be made correspondingly wider and, accordingly, can have a larger opening cross-section due to its greater width, given a specific installation height or, if necessary, a slightly reduced installation height due to structural conditions. In the embodiment shown in Fig. 2 In the embodiment of the invention shown on the right, the two partial duct sections 3.1, 3.2 are designed as flexible hoses, which makes it possible to arrange the two recirculation outlets 200 flexibly, depending, for example, on the structural conditions. In contrast, the two partial duct sections 3.1, 3.2 open into separate recirculation outlets 200, whereby these recirculation outlets 200 are identical in construction to the recirculation outlet 200 according to the prior art (shown on the far left) or differ in their height and, in particular, may have a lower height.

[0034] In Fig. 3 and 4 Figure 1 shows an installation situation of a flat duct arrangement 1 according to the invention, in which the flat duct arrangement 1 fluidically connects a downdraft extractor hood 100 with a one-piece recirculation outlet 200 arranged in the base of the furniture 400. Referring to the Fig.2 is the one in the Fig. 3 and 4The embodiment shown corresponds at least structurally to the middle embodiment of the Fig. 2 The two duct sections 3.1 and 3.2 are designed to open into the same recirculation outlet 200, which can be a single piece, for example, with air guide vanes formed in one piece across the entire width of the recirculation outlet 200. The duct assembly 1 is connected to the extractor hood 100 via the first duct section 2. The first duct section 2 opens directly into the air inlet 5 of the Y-shaped flat duct section 4. The Y-shaped flat duct section 4 has mounting tabs 17 for attaching it to a vertical wall of the furniture 400. The Y-shaped flat duct section 4 opens into a reducer 12. The Y-shaped flat duct section 4 and the reducer 12 can be designed as a single piece or modularly, i.e., as separate components. The Y-shaped flat channel section 4 with the reducer 12 leads into a 90° pipe bend 7, which flows downstream into the second channel section 3 with the two sub-channel sections 3.1, 3.2.

[0035] The Fig. 4 It can further be seen that the 90° pipe bend 7 has a projection 9 on its outer radius 8, for example, at least one radially projecting web, which has a horizontal bearing surface 10 that is aligned with an outer edge 11 of the outlet cross-section of the 90° pipe bend 7 on a side of the 90° pipe bend 7 facing away from the Y-shaped flat duct section 4. In this way, the vertically extending part of the flat duct assembly 1, in particular the first duct section 2, is supported by the Y-shaped flat duct section 4 connected to it, including the reducer 12, so that the connection point of the flat duct assembly 1 to the downdraft extractor hood 100 is relieved of stress.

[0036] The overview of Fig. 3 and 4shows that, given a construction height of, for example, 60 mm in the base area of ​​the furniture 400, due to the use of the Y-flat duct piece 4 and the resulting multi-part nature of the second duct section 3, the second duct section 3 can be made significantly wider, thus allowing a larger opening cross-section for the recirculation outlet 200.

[0037] The order according to Fig. 5 The diagram, consisting of a Y-shaped flat duct section 4, a reducer 12, and a 90° pipe bend 7, illustrates the modular design of these components according to one embodiment of the invention. In particular, the Y-shaped flat duct section 4 and the reducer 12 can be formed as single pieces. A multi-part design of the Y-shaped flat duct section 4 and the reducer 12 is particularly advantageous for flexibly adapting to different base heights while simultaneously allowing the Y-shaped flat duct section 4 to be designed as a single, uniform part. This is because the opening width of the flat duct connection cross-section 14 of the reducer 12 precisely determines the height of the outlet cross-section of the second duct section 3. In particular, it can be provided that the pipe bend 7 does not undergo any change in cross-section. However, in one embodiment, it is conceivable that the change in cross-section occurs within the pipe bend 7 during the 90° flow redirection.Corresponding 90° pipe bends with cross-sectional changes are known from the prior art.

[0038] The embodiment according to Fig. 6 Figure 1 shows a Y-shaped flat duct section 4 with a reducer 12 integrally molded onto it, wherein the Y-shaped flat duct section 4 with its two air outlets 6 is connected via a reducer 12 each into a 90° pipe bend 7 (see Figure 1). Fig. 5 ) can terminate. The reducer 12 terminates with a first flat duct connection cross-section 13 in the Y-shaped flat duct section 4 and with a second flat duct connection cross-section 14 in the 90° pipe bend 7 (not shown). The shorter side of the first flat duct connection cross-section 13 has a larger dimension than the shorter side of the second flat duct connection cross-section 14 in order to reduce the duct cross-section to a height dimension permitted in the base area of ​​a piece of furniture.

[0039] The sum of the areas A2 of the cross-sections of the air outlets 6 of the Y-shaped flat duct section 4 is greater than the area A1 of the cross-section of the air inlet 5 of the flat duct section 4. Preferably, the sum of the areas A2 of the cross-sections of the air outlets 6 is at least 20% greater than the area A1 of the cross-section of the air inlet 5. The air outlets 6 and the air inlet 5 can each have a rectangular cross-section, wherein a height L1, L2 of the respective cross-section, which is perpendicular to a width L3, L4 of the respective cross-section, is smaller than the width L3, L4. Reference symbol list:

[0040] 1 Flat duct arrangement 2 First duct section 3 Second duct section 3.1 First sub-duct section 3.2 Second sub-duct section 4 Y-flat duct section 5 Air inlet 6 Air outlet 7 Pipe bend 8 Outer radius 9 Projection 10 Base surface 11 Outer side 12 Reducer 13 First flat duct connection cross-section 14 Second flat duct connection cross-section 15 Divider 16 Divider wall 17 Mounting bracket 100 Downdraft extractor hood 200 Recirculation outlet / recirculation filter 300 Flat duct 400 Furniture A1 First surface A2 Second surface L1 First height L2 Second height L3 First width L4 Second width

Claims

1. Arrangement comprising a downdraft extractor hood (100), a flat duct arrangement (1) and at least one circulating air outlet (200), wherein the flat duct arrangement (1) has a first duct section (2) connected to the downdraft extractor hood (100) and a second duct section (3) connected to the at least one circulating air outlet, characterized in that the flat duct arrangement (1) has, in the flow direction from the first duct section (2) to the second duct section (3), a Y flat duct piece (4) with an air inlet (5) facing the first duct section (2) and two air outlets (6) facing the second duct section (3), which Y flat duct piece (4) is designed to divide a volume flow coming from the downdraft extractor hood (100) into two partial flows and to carry out a change in cross section, wherein the Y flat duct piece (4) opens with its two air outlets (6) in each case into a 90° tube bend (7), wherein an inlet cross section of the air inlet (5) and both outlet cross sections of the air outlets (6) of the Y flat duct piece (4) are arranged in a horizontal plane, and wherein an outlet cross section of the 90° tube bend (7) is arranged in a vertical plane, and wherein the 90° tube bend (7) is arranged at a transition of the flat duct arrangement (1), in which transition the flat duct arrangement (1) is diverted from a vertical profile in the flow direction for discharging vapors from a hob into a base region of a piece of furniture (400) into a horizontal profile in the flow direction for conducting the vapors through a base of the piece of furniture (400).

2. Arrangement (1) according to claim 1, in which the second duct section (3) has, downstream of the Y flat duct piece (4), two partial duct sections (3.1, 3.2) which are fluidically separated from one another and which are preferably arranged next to one another in the horizontal direction.

3. Arrangement (1) according to claim 2, in which the two partial duct sections (3.1, 3.2) have an identical flow cross section and preferably the same cross-sectional area.

4. Arrangement (1) according to claim 2 or 3, in which the two partial duct sections (3.1, 3.2) open into a circulating air outlet (200), wherein the circulating air outlet (200) of the two partial duct sections (3.1, 3.2) is the same circulating air outlet (200) and extends as a continuous circulating air outlet (200) over outlet cross sections of the two partial duct sections.

5. Arrangement (1) according to claim 2 or 3, in which the two partial duct sections (3.1, 3.2) open into different circulating air outlets (200) which are preferably spaced apart from one another by more than a horizontal width of one of the two partial duct sections.

6. Arrangement (1) according to claim 5, in which at least one of the two partial duct sections (3.1, 3.2) is formed at least in sections as a flexible duct with at least one variable radius of curvature.

7. Arrangement (1) according to one of the preceding claims, in which a duct length of the first duct section (2) in the flow direction is shorter than a duct length of the second duct section (3) in the flow direction.

8. Arrangement (1) according to claim 7, in which the duct length of the first duct section (2) from a connection of the first duct section (2) for a downdraft extractor hood (100) to the Y flat duct piece is smaller than the duct length of the second duct section (3) from a connection of the second duct section (3) for a circulating air outlet (200) to the Y flat duct piece (4).

9. Arrangement (1) according to one of the preceding claims, in which an inlet cross section of the air inlet (5) and both outlet cross sections of the air outlets (6) of the Y flat duct piece (4) are arranged in parallel planes with respect to one another.

10. Arrangement (1) according to claim 9, in which the two outlet cross sections of the air outlets (6) of the Y flat duct piece (4) are arranged in the same plane.

11. Arrangement (1) according to one of the preceding claims, in which the 90° tube bend (7) has at its outer radius (8) at least one projection (9) which has a horizontal contact surface (10) which, on a side of the 90° tube bend (7) facing away from the Y flat duct piece (4), is aligned with an outer side (11) of the outlet cross section of the 90° tube bend (7).

12. Arrangement (1) according to one of the preceding claims, in which the Y flat duct piece (4) opens with its two air outlets (6) via in each case one reducing piece (12) into the 90° tube bend (7), wherein the reducing piece (12) opens with a first flat duct connection cross section (13) into the Y flat duct piece (4) and with a second flat duct connection cross section (14) into the 90° tube bend (7), and wherein at least one shorter side of the first flat duct connection cross section (13) has a larger dimension than a shorter side of the second flat duct connection cross section (14).

13. Arrangement (1) according to one of the preceding claims, in which the sum of the areas (A2) of the cross sections of the air outlets (6) of the Y flat duct piece (4) is greater than the area (A1) of the cross section of the air inlet (5) of the Y flat duct piece (4), wherein preferably the sum of the areas (A2) of the cross sections of the air outlets (6) is greater by at least 20% than the area (A1) of the cross section of the air inlet (5).

14. Arrangement (1) according to one of the preceding claims, in which the air outlets (6) and the air inlet (5) of the Y flat duct piece (4) each have a rectangular cross section, wherein an aspect ratio of the cross section of the air inlet (5) is between 1:2.2 and 1:2.5.

15. Arrangement (1) according to one of the preceding claims, in which the second duct section (3) has, downstream of the Y flat duct piece (4), two partial duct sections (3.1, 3.2) which are fluidically separated from one another and have a rectangular cross section and which are arranged with their shorter sides lying opposite one another next to one another in the horizontal direction, wherein an aspect ratio of the combined cross sections of the partial duct sections (3.1, 3.2) is between 1:3.5 and 1:4.5 and preferably 1:4.

16. Arrangement (1) according to one of the preceding claims, in which the air outlets (6) and the air inlet (5) each have a rectangular cross section, wherein a height (L1, L2) of the respective cross section which runs perpendicular to a width (L3, L4) of the respective cross section is smaller than the width (L3, L4).

17. Arrangement (1) according to claim 14, in which the ratio between the height (L1) of the cross section of the air inlet (5) and the heights (L2) of the cross sections of the air outlets (6) is at least 3:2.

18. Arrangement (1) according to one of the preceding claims, in which the Y flat duct piece (4) has a divider (15) with two divider walls (16) which diverge in the flow direction and of which the volume flow flowing in via the air inlet (5) is divided into two partial volume flows, wherein the divider (15) is arranged with its divider walls (16) symmetrically with respect to a centre line of an inlet cross section of the air inlet (5) of the Y flat duct piece (4).

19. Arrangement (1) according to claim 16, in which the two divider walls (16) adjoin one another on the air inlet side and diverge from one another at an acute angle in the flow direction.

20. Arrangement (1) according to one of the preceding claims, which has a hydraulic diameter of at least 8 cm and particularly preferably a hydraulic diameter of at least 8.5 cm.

Images