The bend in the exhaust pipe used for a smoke hood

Abstract

The present invention relates to a pipe bend, particularly an exhaust pipe for a fume hood, the pipe bend having an inflow side and an outflow side, and having a deflection of 60° to 120°, preferably 90°, wherein the pipe bend has at least one air guiding element that bends in the deflection direction and extends inside the pipe bend, characterized in that the pipe bend has a cross-sectional widening portion after the inflow side in the flow direction, particularly adjacent to the inflow side, and a cross-sectional tapering portion (18) before the outflow side, particularly adjacent to the outflow side, the direction of the bend of the outer wall of the bend deviates from the direction of a quarter circle, and has a protrusion located outside the apex of the bend, particularly downstream of the apex in the flow direction.

Description

Technical Field

[0001] This invention relates to a pipe bend, particularly an exhaust duct for a fume hood, the bend having an inflow side and an outflow side, and having a deflection of 60° to 120°, preferably 90°, wherein the bend has at least one air guiding element that bends in the deflection direction and extends inside the bend. Such a pipe bend is known, for example, from DE102016220527A1. Background Technology

[0002] In the case of ordinary pipe bends in exhaust ducts used for fume hoods, it is generally desirable to keep the pressure loss in the passage as low as possible. As is known, in areas of change in pipe direction, particularly in bends, the expected pressure loss is especially large because at least partially non-laminar airflow occurs due to airflow deflection in the bend, highly turbulent air separation, and associated turbulence. Air separation and turbulence not only contribute to pressure loss but also to noise generation, which is fundamentally undesirable and should be reduced to the lowest possible level. One approach to addressing these issues is to use air-guiding elements, but further improvements in achievable effects on noise generation and pressure loss reduction are still desirable. Summary of the Invention

[0003] Therefore, the object of the present invention is to further develop the above-mentioned type of pipe bend so that it causes the least possible noise and has the lowest possible pressure loss for the fluid flowing through it, especially air and steam.

[0004] This objective is achieved by a pipe bend according to an embodiment of the invention.

[0005] Therefore, the pipe bend is configured such that it has a cross-sectional widening portion downstream of the inflow side, particularly adjacent to the inflow side, and a cross-sectional narrowing portion upstream of the outflow side, particularly adjacent to the outflow side. The direction of the bend in the outer wall of the pipe bend deviates from the direction of a quarter circle, and it has a protrusion located outside the apex of the pipe bend, particularly downstream of the apex in the flow direction.

[0006] Since flow optimization requires an asymmetrical design of the pipe bend, it can be advantageous to define one side of the bend as the inflow side and the other side as the outflow side to optimize airflow. Alternatively, the pipe bend can be configured to have a larger cross-section than the connecting cross-section to minimize pressure loss, thereby expanding the flow cross-section in the region of the air guiding element. The cross-sectional expansion for this purpose can be directly adjacent to the inlet-side connecting cross-section. The connecting area can be in the form of a connecting sleeve. The cross-sectional expansion can extend over a short distance, particularly outside the deflection region of the pipe bend. The widening of the flow cross-section advantageously leads to a reduction in wall friction loss, and thus a reduction in pressure loss in the flow. Furthermore, the widening results in a decrease in flow velocity within the bend, and thus a reduction in inertial forces in the flow. A cross-sectional tapering can be provided immediately upstream of the outflow-side connecting cross-section in the flow direction. The cross-sectional tapering can extend over a short distance, particularly outside the deflection region of the pipe bend.

[0007] The purpose of the protrusion is to allow volumetric flow to follow a biomimetic orientation. To this end, the outer wall of the pipe bend, deviating from a quarter circle, ensures an initial constant distance between the outermost air guide elements in the outer region of the bend, where this distance increases after the apex of the bend. This is particularly advantageous when interacting with multi-part outer air guide elements. As a result, the flow approximates the biomimetic orientation, which improves the flow pattern in the pipe bend. The biomimetic orientation of the wall profile is based on the tortuosity of a riverbed to achieve a low pressure differential across the cross-section. The non-circular profile prevents locally high flow velocities.

[0008] It can be configured such that the radius of the inner wall of the pipe bend corresponds to the direction of a quarter circle. This means that, compared to the outer wall of a biomimetic pipe bend, the pipe bend can have a regular inner wall in the form of a quarter circle.

[0009] It can be configured such that, along the entire course of the bend, the cross-sectional area of ​​the pipe bend is larger than both the inflow and outflow cross-sections. This advantageously ensures that there is no undesirable pressure loss at any point in the pipe bend. In designs where the cross-sectional area varies between the inflow and outflow sides, for example, from a flat pipe to a round pipe, it can be configured such that the cross-sectional areas of the two different cross-sectional shapes remain substantially the same, with the intermediate pipe bend section always having a larger cross-sectional area.

[0010] It can be configured such that at least one air guiding element has a concave terminal edge on the inlet side of the pipe bend. This concave guide shape on the inlet side of the air guiding element ensures optimal flow guidance on the inlet side. The concave curvature can be achieved such that the center of the terminal edge protrudes more into the pipe bend than the terminal edge on the inner side of the adjacent wall, or retracts back into the pipe bend. This forces the flow away from the wall to reduce wall friction.

[0011] It can be configured such that the terminal edge of at least one air guiding element on the inflow side of the pipe bend protrudes into the inflow cross-section in the region of the opposing wall area. For this purpose, the outer region of the terminal edge can protrude into the connecting sleeve in a serrated manner. This allows flow to be detected at an early stage before being deflected in the bend. Furthermore, the guiding edge of the guide body can be optimized for tangential inflow to avoid impact losses.

[0012] It can be configured such that at least one air guiding element has a convex terminal edge on the outflow side of the pipe bend. This convex guide shape on the outflow side of the air guiding element ensures optimal flow guidance on the outflow side. The convex curvature can be achieved such that the center of the terminal edge protrudes more into the connecting sleeve compared to the terminal edge on the inner side of the adjacent wall.

[0013] It can be configured such that the central region of the end face terminal edge of at least one air guide element protrudes into the outflow cross-section on the outflow side of the pipe bend. Therefore, the tail edge of the guide element can extend towards the center of the pipe to achieve complete flow redirection before entering a straight air duct.

[0014] It can be configured such that at least one air guiding element has a comb-like or serrated toothed end edge on the outflow side of the pipe bend at its end face. It has been found that particularly low-noise flow can be achieved through the toothed end edge. The teeth can be, for example, a sharp-edged design or a wave-like design. It is also conceivable that the outflow end edge is both convex in shape and comb-like in form.

[0015] It can be configured such that at least one air guiding element has at least one traveling edge or traveling line arranged perpendicular to and / or parallel to the flow direction on its surface. Furthermore, multiple traveling lines, one arranged perpendicular to the flow direction behind another, or multiple traveling lines arranged parallel to the flow direction beside another, can be arranged on the surface of the air guiding element. Moreover, it is conceivable that these traveling edges are arranged in a grid-like manner on the surface of the air guiding element. The traveling edges can be arranged on one or both sides of the air guiding element. In particular, it is conceivable that the traveling edges are arranged on the suction side of the guide body to generate a turbulent boundary layer, thereby preventing flow separation and achieving lossless deflection. In particular, it can be configured such that, in the case of a guide body with a smaller radius, i.e., an inner guide body, the traveling edges are arranged in the front region when viewed from the flow direction. In particular, it can also be configured such that, in the case of a guide body with a larger radius, i.e., an outer guide body, the traveling edges are arranged in the rear region when viewed from the flow direction.

[0016] It can be configured such that the air guide element is multi-part, wherein the first part and the second part of the air guide element are offset from each other in the radial direction of the pipe bend.

[0017] Curved air guide elements can, in particular, be composed of two parts. However, alternatively, they can also be formed as three or more parts. For example, an air guide element can be formed from multiple air guide element sub-elements, each of which is straight and offset from adjacent air guide elements, thus arranging the sub-elements within the bend to define the arc. In this case, adjacent sub-elements can be rotated relative to each other by a corresponding angle. In a two-part design, the air guide element is preferably divided into halves along its length in the extending direction between opposing connecting cross-sections of the bend, for example at the apex of the air guide element.

[0018] In an embodiment, some elements may overlap each other in the overlapping area of ​​their facing ends. In this case, the two-part elements may be arranged such that they are offset from each other in the overlapping area. Preferably, they extend parallel to each other in the overlapping area.

[0019] In an alternative embodiment, some components may be aligned with their facing end faces. Preferably, they do not need to be precisely opposite each other. Instead, they may simply be arranged such that the end faces of the components are aligned in the radial direction of their curvature.

[0020] When a pipe bend has multiple curved air guide members, it can be configured such that the first curved air guide member has overlapping portion members of the type described above in the overlapping area, while the second curved air guide member has portion members facing each other, wherein their end faces are aligned in the radial direction of the curvature. For example, the curved air guide member with overlapping portion members can be an outer curved air guide member, while the curved air guide member with aligned end faces is an inner curved air guide member, which is configured to be closer to the inner radius of the pipe bend than the outer curved air guide member, and therefore has a smaller radius of curvature than the outer air guide member.

[0021] If the air guide element is designed as two parts, it can be specifically configured such that the first part and the second part are offset from each other at the apex of the air guide element.

[0022] It has been found that the spacing of some components in the radial direction of the curvature of the air guide element leads to a reduction in flow separation and thus suppresses the formation of turbulence in the pipe bend, ultimately reducing pressure loss and noise generation in the pipe bend compared to pipe bends known in the prior art.

[0023] The pipe bend can be configured to have multiple air guiding elements arranged substantially adjacent to each other in parallel within the bend, with the air guiding element closest to the outer wall of the bend being multi-part. The first and second part elements of the air guiding elements are offset relative to each other in the radial direction of the bend. The design of the outer air guiding element with at least two part elements ensures a reduction in flow separation, particularly in the edge regions of the bend where boundary layer separation is prone to occur.

[0024] Advantageously, the number of air guiding elements arranged adjacent to each other can be adjusted according to the diameter of the pipe bend, with more air guiding elements for larger diameters and vice versa.

[0025] It can be configured such that the pipe bend has three air guiding elements arranged parallel to each other in the pipe bend, with the middle air guiding element and the inner air guiding element each having a single-piece design.

[0026] It can be configured such that the distance between the air guiding elements increases toward the outer wall of the pipe bend, and the average distance between the outer air guiding element and the middle air guiding element is 1.4-1.8 times larger than the distance between the middle air guiding element and the inner air guiding element, preferably 1.5-1.7 times, and particularly preferably 1.6 times.

[0027] The distance from the inner air guide element to the inner wall of the pipe bend can be set to at most 20%, preferably at most 15%, and particularly preferably at most 9% of the average pipe bend radius. It has been found that, in particular, bringing the inner guide element closer to the inner radius of the pipe bend results in a significant improvement in flow behavior.

[0028] The tube bend can be configured with spaced-apart guide grooves on opposite inner sides for lateral insertion and fixation of the air guide element within the bend. A pair of separate, opposite, and aligned guide grooves can be provided in the tube bend for each air guide element or for each sub-element. The guide grooves can be designed so that the air guide element can only be inserted into the groove after prestress has been overcome. The assembly of the air guide element can depend on the joining method of the half-shell. For example, in the case of mirror welding, due to the automated process and mirror thickness, the air guide element can be pre-centered on one side of the half-shell by means of a covered injection-molded guide portion on the air guide element, and then thermally bonded.

[0029] The pipe bend can be configured to have an installation indicator, particularly in the form of an arrow, to indicate the installation direction on the outside of the bend. This simplifies and speeds up installation, and makes it particularly easy to identify the flow direction after the bend has been installed.

[0030] The installation indicator can be formed as a recess or accumulation of material in the bend. The installation indicator can be located on one side, top, or bottom of the bend, or a combination thereof.

[0031] In the inflow and / or outflow areas, the pipe bend may have connection points on both sides, and particularly at the center of the connecting element, through which the pipe bend can be connected to the adjacent pipe element.

[0032] It can be configured such that the pipe bend is a flat pipe bend or a transition bend from a rectangular flat pipe connection to a circular pipe connection, or vice versa.

[0033] The surface of the air guiding element facing the inner wall of the pipe bend can be configured to be double-curved, wherein the first curvature extends at least segmentally along the flow direction, and the second curvature extends at least segmentally perpendicular to the flow direction. The curvatures can optionally both be concave. Alternatively, the first curvature can be concave in the flow direction, corresponding to the curvature of the pipe bend, and the second curvature can be convex perpendicular to the flow direction toward the inner wall of the pipe bend, such that the air guiding element or these air guiding elements present a hyperbolic paraboloid. Attached Figure Description

[0034] Further features, advantages, and characteristics of the invention can be seen in the following description of preferred embodiments of the invention with reference to the accompanying drawings, in which:

[0035] Figure 1 This is a top view of an embodiment of the pipe bend according to the present invention;

[0036] Figure 2 This is a perspective view of an embodiment of the pipe bend according to the present invention;

[0037] Figure 3 This is a perspective view of another embodiment of the pipe bend according to the present invention;

[0038] Figure 4 This is a top view of another embodiment of the pipe bend according to the present invention; and

[0039] Figure 5 This is an exploded view of another embodiment of the pipe bend according to the present invention. Detailed Implementation

[0040] Figure 1A first embodiment of a pipe bend 1 in the form of a flat pipe according to the invention is shown, which deflects air to be discharged from the exhaust hood by 90°. The pipe bend 1 has an inflow side 10 and an outflow side 12, which define a flow direction x. Therefore, when installing the bend, care must be taken to ensure that it is inserted in the correct orientation so that exhaust gas flows in through the inflow side 10 and out through the outflow side 12. Three air guiding elements 3 are arranged in the pipe bend 1, wherein the air guiding element 3 closest to the outer wall 9 of the pipe bend comprises two partial elements 4 and 5, which overlap in an overlapping region 6 by means of opposing ends 2 and are offset from each other by d. The rear partial element 5 in the flow direction x is arranged closer to the inner wall 8 of the pipe bend than the front partial element 4. In the overlapping region 6, the partial elements 4 and 5 extend equidistantly from each other. Furthermore, the partial elements 4 and 5 extend equidistantly relative to adjacent intermediate air guiding elements 3, which in turn extend equidistantly relative to the innermost air guiding element 3. Air guide element 3 and components 4 and 5 each have a double concave curvature. The first curvature follows the orientation of the pipe bend 1, and the second concave curvature is characterized by the curvature of the components around their extension in the flow direction x, such that they are each concave toward the inner wall 8 of the pipe bend. In particular, it can be seen that the inner air guide element 3 has a larger second concave curvature than the intermediate air guide element, and the intermediate air guide element has a larger second concave curvature than each of the components 4 and 5 of the outer air guide element 3. Therefore, the inner air guide element 3 protrudes more toward the outer wall 9 of the pipe bend than the intermediate and outer air guide elements, and correspondingly, the intermediate air guide element protrudes more than the outer air guide element 3. Taking into account the different degrees of curvature radii at the locations of the different air guide elements 3, these different degrees of curvature result in optimal deflection of air at each point in the pipe bend. In the region between the apex of the pipe bend 1 and the outflow side 12, the outer wall of the pipe bend has a protrusion 19 pointing outwards from the pipe bend 1. This can be, for example, one-dimensional, such that the protrusion 19 is constant along the height direction of the pipe bend 1. Alternatively, the protrusion 19 can be bubble-shaped, such that its maximum elevation is located in the height direction at or approximately in the center of the pipe bend 1, and conversely, the region of the outer wall 9 of the pipe bend adjacent to the inner side 15 has no elevation or a relatively small elevation. In the flow direction x, the protrusion 19 can have an initial flat rise up to the apex of the protrusion 19 compared to the quarter-circle direction. After the apex of the protrusion 19, it can have a steeper descent down to the level of the quarter-circle compared to the rise. In the illustrated embodiment, the pipe bend 1 has a connecting sleeve on both the inflow side 10 and the outflow side 12, the connecting sleeve having the same connecting cross section 7. It can be seen that all the air guiding elements 3 extend substantially to the connecting sleeve.On the inflow side, a cross-sectional widening portion 17 is provided after the connecting sleeve, and on the outflow side 12, a cross-sectional tapering portion 18 is connected to the connecting sleeve on the outflow side. Therefore, in the region between the connecting sleeves, the pipe bend 1 does not have a point where its cross-section is less than or equal to the cross-section 7 of the connecting sleeve. Furthermore, it can be seen that the distance of the air guiding element 3 increases from the inner wall 8 of the pipe bend to the outer wall 9 of the pipe bend. The inner air guiding element 3 is arranged very close to the inner wall of the pipe bend, approximately at one-tenth of the width of the pipe bend. On the other hand, the outer air guiding element 3 is arranged away from the outer wall 9 of the pipe bend, and within a range of 1 / 3 to 2 / 3 of the width of the pipe bend.

[0041] Figure 2 Another embodiment of the pipe bend 1 is shown, which also has a connecting sleeve having the same connecting cross section 7 on both the inlet and outlet sides, wherein a cross section widening portion 17 connects to the inflow side 10, and a cross section tapering portion 18 is immediately arranged upstream of the outflow side 12. A plurality of assembly indicators 20 are arranged on the upper side of the pipe bend 1, implemented in the form of arrows. These assembly indicators indicate, on the one hand, the installation direction of the pipe bend 1 to the installer, and on the other hand, the flow direction x of the pipe bend 1 after installation. The installation indicators can be implemented by material recesses as shown, or alternatively by material thickening portions. Furthermore, it is conceivable that this bend 1 be highlighted with color on its outer side. Particularly as can be seen in the perspective view shown, the air guide element 3 has a concave terminal edge 11 on the inflow side, such that the average height of the air guide element 3 protrudes into the pipe bend 1 in the flow direction x relative to its outer edge located on the inner side 15 of the pipe bend. On the other hand, the terminal edge 13 of the air guide element 3 is convex on the outflow side, such that the average height of the air guide element 3 protrudes from the outer edge of the pipe bend 1 relative to the inner side 15 of the bend in the flow direction x. In the perspective view shown, the air guide element 3 closest to the inner wall 8 of the bend is not visible, but it also has terminal edges 11, 13, which are concave on one side and convex on the other. The air guide elements 3 are respectively fixed in the bend by guide grooves 16. Not shown, the guide grooves 16 associated with the air guide element 3 are formed on two opposing inner sides 15 of the bend 1 and are aligned with each other. Before assembling the half-shell of the bend 1, the air guide elements 3 can be inserted into them laterally or vertically. The air guide element also has traveling edges 14 or traveling lines, which, in the illustrated embodiment, are arranged in a grid pattern on the air guide element 3 and help improve airflow in the bend 1. The travel line can be a stepped material thickening formed on the air guide element 3.

[0042] Figure 3Another embodiment of the pipe bend 1 in its installed state is shown. This pipe bend also features, in particular, a protrusion 19 and three equidistantly extending air guide elements 3, wherein the air guide element closest to the outer wall 9 of the pipe bend is divided into two partial elements 4, 5. Specifically, it can be seen that the outflow-side terminal edge 13 of the air guide element 3 has a comb-like toothed end 22, which is molded along the direction of an owl's wing and ensures the quietest possible air guidance by reducing noise even at different flow rates.

[0043] Figure 4 Another embodiment of the pipe bend 1 according to the invention is shown. This pipe bend specifically has connection points 21 in the form of undercut locking elements, arranged on the outer sides, top, and bottom of the inflow and outflow sides of the pipe bend 1, and connectable to the pipe bend 1 via its connecting elements. In the illustrated embodiment, the assembly indicator 20 is implemented by a broad arrow, with additional arrows spaced apart at the tip of the broad arrow in the flow direction.

[0044] at last, Figure 5 An exploded view shows an embodiment of the pipe bend 1. The pipe bend has a lower shell and an upper shell, which are detachably connected to each other via a locking connection provided at the contact point. The shells separate the pipe bend 1 parallel to the deflection plane. Air guiding elements 3, or parts thereof 4, 5, are accommodated between the shells and can be fixed in guide grooves 16 on the inner sides 15 of the upper and lower shells of the pipe bend 1. Figure 4 Unlike the previous embodiment, the connection point 21 is now located on the side of the pipe bend 1.

[0045] The features of the invention disclosed in the foregoing description, drawings, and claims are essential for implementing the invention, either individually or in any combination.

[0046] List of reference numerals

[0047] 1. Pipe bend

[0048] 2 ends

[0049] 3 Air guiding elements

[0050] 4. First Part Components

[0051] 5. Second Part Components

[0052] 6. Overlapping areas

[0053] 7 Connecting cross sections

[0054] 8. Inner wall of pipe bend

[0055] 9. Outer wall of pipe bend

[0056] 10. Inflow side

[0057] 11. Concave terminal edge

[0058] 12 Outflow side

[0059] 13. Convex terminal edge

[0060] 14. Edge of Progress

[0061] 15 Inner side

[0062] 16 guide slots

[0063] 17. Cross-sectional widening section

[0064] 18. Tapered section of cross-section

[0065] 19. Protrusion

[0066] 20 Assembly Indicators

[0067] 21 Connection Points

[0068] 22. Comb-shaped toothed end

[0069] x Flow direction

[0070] D adjustment

Claims

1. A pipe bend (1) for an exhaust pipe of a fume hood, the pipe bend having an inflow side (10) and an outflow side (12), the pipe bend having a deflection of 60° to 120°, wherein, The pipe bend (1) has at least one air guide element (3) that bends in the deflection direction and extends inside the pipe bend (1), wherein the pipe bend (1) has a cross-sectional widening portion (17) adjacent to the inflow side (10) in the flow direction (x) and a cross-sectional tapering portion (18) adjacent to the outflow side (12) in front of the outflow side. The bend is characterized in that the direction of the bend of the outer wall (9) of the pipe bend deviates from the direction of a quarter circle and has a protrusion (19) located outside the apex of the pipe bend (1) and downstream of the apex in the flow direction (x). Thus, in the flow direction (x), compared with the direction of a quarter circle, the protrusion (19) has an initially flat rising portion up to the apex of the protrusion (19), and after the apex of the protrusion (19), the protrusion (19) has a steeper descending portion down to the level of a quarter circle compared with the rising portion.

2. The pipe bend (1) according to claim 1, wherein the radius of the inner wall (8) of the pipe bend corresponds to the direction of a quarter circle.

3. The pipe bend (1) according to claim 1 or 2, wherein the cross-sectional area of ​​the pipe bend is greater than the inflow cross-section and the outflow cross-section of the pipe bend (1) over the entire direction of the bend.

4. The pipe bend (1) according to claim 1, wherein at least one air guiding element (3) has a concave terminal edge (11) at the end face on the inflow side (10) of the pipe bend (1).

5. The pipe bend (1) according to claim 4, wherein the concave terminal edge (11) of at least one air guide element (3) on the inflow side (10) of the pipe bend (1) protrudes into the inflow cross section in the region of the opposite wall region.

6. The pipe bend (1) according to claim 1, wherein at least one air guiding element (3) has a convex terminal edge (13) on the end face of the outlet side (12) of the pipe bend (1).

7. The pipe bend (1) according to claim 6, wherein the central region of the end face terminal edge (13) of at least one air guiding element (3) on the outflow side (12) of the pipe bend (1) protrudes into the outflow cross section.

8. The pipe bend (1) according to claim 1, wherein at least one air guiding element (3) has a comb-shaped toothed end (22) on the end face of the outlet side (12) of the pipe bend (1).

9. The pipe bend (1) according to claim 1, wherein at least one air guiding element (3) has at least one traveling edge (14) arranged perpendicular to and / or parallel to the flow direction on its surface.

10. The pipe bend (1) according to claim 1, wherein the air guiding element (3) is multi-part, wherein the first part element (4) and the second part element (5) of the air guiding element (3) have an offset (d) relative to each other in the radial direction (R) of the pipe bend (1).

11. The pipe bend (1) according to claim 10, the pipe bend includes a plurality of air guide elements (3) arranged substantially side by side in parallel in the pipe bend (1), wherein the air guide element (3) closest to the outer wall (9) of the pipe bend is multi-part, wherein the first part element (4) and the second part element (5) of the air guide element (3) closest to the outer wall (9) of the pipe bend have an offset (d) relative to each other in the radial direction (R) of the pipe bend (1).

12. The pipe bend (1) according to claim 11, the pipe bend has three air guiding elements (3) arranged adjacent to each other in parallel in the pipe bend, the middle air guiding element and the inner air guiding element (3) each having a single-piece design.

13. The pipe bend according to claim 12, wherein the distance of the air guiding element (3) increases toward the outer wall (9) of the pipe bend, wherein the average distance from the outer air guiding element (3) to the middle air guiding element (3) is 1.4-1.8 times greater than the distance from the middle air guiding element (3) to the inner air guiding element (3).

14. The pipe bend (1) according to claim 11, wherein the distance between the inner air guiding element (3) and the inner wall (8) of the pipe bend is at most 20% of the average pipe bend radius.

15. The pipe bend (1) according to claim 1, wherein the pipe bend has spaced guide grooves (16) on opposite inner sides (15) for lateral insertion and fixation of air guiding elements in the pipe bend (1).

16. The pipe bend (1) according to claim 1, wherein the pipe bend has an installation indicator (20) for indicating the installation direction on the outside of the pipe bend (1).

17. The pipe bend (1) according to claim 1, wherein the pipe bend is formed as a flat pipe bend or as a transition bend from a rectangular flat pipe connection to a circular pipe connection, or vice versa.

18. The pipe bend according to claim 13, wherein the average distance from the outer air guide element (3) to the middle air guide element (3) is 1.5-1.7 times greater than the distance from the middle air guide element (3) to the inner air guide element (3).

19. The pipe bend according to claim 13, wherein the average distance from the outer air guide element (3) to the middle air guide element (3) is 1.6 times greater than the distance from the middle air guide element (3) to the inner air guide element (3).

20. The pipe bend (1) according to claim 14, wherein the distance between the inner air guiding element (3) and the inner wall (8) of the pipe bend is at most 15% of the average pipe bend radius.

21. The pipe bend (1) according to claim 14, wherein the distance between the inner air guiding element (3) and the inner wall (8) of the pipe bend is at most 9% of the average pipe bend radius.

22. The pipe bend (1) according to claim 16, wherein the installation indicator (20) is in the form of an arrow.

23. The pipe bend (1) according to claim 1, wherein, The pipe bend has a 90° deflection.

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