Device for controlling an air volumetric flow

Abstract

The invention relates to a device for regulating an air volume flow rate, in particular in an air distribution network, comprising a central air channel (24) having a cross-section through which a flow can flow, and a throttle valve (6) arranged in the central air channel (24). The through-flow cross-section (70) can be varied by means of the throttle valve (6). The inner flow element (3) has a housing (30), the circumference of which increases in the direction away from the throttle valve (6). The central air channel (24) has a taper (251) and a subsequent rewidening (252) in the region of the flow element. As a result, a curved flow channel (8) is produced between the housing (30) of the inner flow element (3) and the rewidening (252), said channel terminating towards the outside of the device. The device according to the invention enables a simple adjustment of the volumetric flow rate, a simple measurement of the volumetric flow rate, and an optimal flow distribution when used as an inlet valve.

Description

Technical Field

[0001] The invention relates to a device for regulating an air flow, in particular an inlet valve or an outlet valve. Background Art

[0002] Air distribution networks are used, in particular, in buildings for ventilation and exhaust air and partly for air conditioning of rooms. Controlled residential and office ventilation installations are now well-established systems which use central or decentralized ventilation devices.

[0003] A wall opening, ceiling opening or floor opening of a building has an air duct with an insert, which is connected to an air distribution network. Such an air duct changes the shape of the air flow and / or adjusts the air volume flow. Some of the inserts enable the air volume flow to be regulated. Depending on the direction of the flow entering or leaving the room, the insert is called an inlet valve or an outlet valve. The insert delimits a cross section in the air duct, wherein the size of the delimitation is partially selectable.

[0004] Inlet valves, ie valves through which air flows into the room, generally have the disadvantage that they distribute the outflowing air unevenly. People sitting or lying down who are directly exposed to the outflowing air may feel uncomfortable.

[0005] The exhaust valve, ie the valve through which the air flows out of the room, usually has a different shape than the intake valve, which results in a noisier appearance in the room.

[0006] Furthermore, such inlet and outlet valves cannot usually be adjusted in the installed state or can only be adjusted with relatively great effort. Another disadvantage is that, depending on the degree of adjustment of the valve, the individual components of the valve protrude to varying degrees into the room, protrude compared to the building wall and impair the visual appearance of the room.

[0007] WO 2022 / 101056 A1 discloses an air volume throttle valve having an air guide body in the form of a rotor blade. The air guide body is formed by a first air guide unit and a second air guide unit, respectively, which can be twisted relative to each other so that the spacing between the air guide bodies can be changed, thereby changing the flow-through cross section of the air channel. The device enables a free change in the flow cross section while the location of the narrowest flow cross section remains unchanged. This makes it easier to control the valve. Summary of the invention

[0008] It is therefore an object of the present invention to provide an improved device for regulating a volume flow.

[0009] This object is achieved by a device having the features of claim 1 .

[0010] The device according to the invention for regulating the air volume flow, in particular the air volume flow in an air distribution network, has a central air channel with a cross section through which flow can flow and a throttle valve arranged in the central air channel, wherein the cross section through which flow can flow can be changed by means of the throttle valve. In addition, the device has an internal flow element with a housing, the circumference of which increases in the direction away from the throttle valve. The central air channel has a tapering portion and a subsequent re-widening portion in the region of the flow element. As a result, a curved flow channel is generated between the housing of the internal flow element and the re-widening portion, which flow channel ends toward the outside of the device. The tapering portion is preferably spaced apart from the throttle valve.

[0011] The separation of the inner flow element and the throttle valve and the formation of a central air channel in the region of the inner flow element according to the invention make it possible to form a flow channel whose flow cross section remains constant when the setting of the throttle valve is changed. Depending on the embodiment, the flow cross section of the flow channel is constant over its entire length or it changes in the flow direction. The taper and the subsequent widening again influence the flow distribution in a positive way.

[0012] The flow cross section that remains the same usually points away from the throttle valve and toward the building space. In the case of an air inlet valve, the flow cross section is the outflow cross section or outflow cross section. In the case of an air outlet valve, the flow cross section is the air inlet cross section.

[0013] The device according to the invention has several advantages:

[0014] Since the flow cross section in the region facing the building interior remains unchanged even if the throttle valve setting is changed, the visual appearance of the space also remains essentially or completely unchanged.

[0015] Furthermore, the measurement of the volume flow is simplified by maintaining the same flow cross section, since it is possible to unambiguously associate aerodynamic forces or other measured variables proportional to the flow velocity with the volume flow.

[0016] Furthermore, the separation enables the device to be designed independently of the shape of the throttle valve in the region of the inner flow element. In the case of an air inlet valve, the flow distribution of the air flow entering the building space is optimized.

[0017] Furthermore, the noise-optimized form can be formed in a simpler manner.

[0018] In the device according to the invention, the inner flow element widens toward the building space. The central air channel tapers and widens again, so that a curved flow channel is generated between the inner flow element and the widening. This creates an air inlet valve with an air flow deflected in the radial direction.

[0019] Preferably, the device has a housing, which forms a central air channel and has an inner wall, which forms a tapering and a re-widening. Preferably, the housing is substantially cylindrical. Preferably, the housing has a first circumferential guide surface, a second circumferential guide surface and a projection located therebetween. Preferably, the first guide surface faces the throttle valve, and preferably, the second guide surface extends parallel to the outer housing of the inner flow element. The design allows a valve that can be easily assembled with optimized flow guidance, in particular due to the specific design of the inner wall of the substantially cylindrical housing.

[0020] The curved flow channel preferably has a cross section that remains the same when the setting of the throttle valve is changed. On the one hand, this improves the visual appearance, because the valve always looks the same. In addition, there are more possibilities for where the sensor element for determining the volume flow can be placed. Since the flow channel extends over a visible length, the radial deflection of the outflow is optimized.

[0021] The sensor element for determining the volume flow is preferably an interfering body which is introduced into the outflow channel or, in the case of an exhaust valve, into the inflow channel and around which the air flows.

[0022] When the inner flow element widens in a bell-shaped manner, an optimally uniform, radial outflow is achieved. Due to the Coanda effect, the outflowing or outflowing air flows along the convex surface and is thus distributed along the wall surface. This avoids uncomfortable air flows directed directly downward from the cover.

[0023] The radial distribution of the outflow is further increased if the widened portion has a bell-shaped inner wall.

[0024] The flow channel delimited by the inner wall and the bell-shaped flow element preferably has a cross section over its entire length that does not change when the setting of the throttle valve is changed. This not only facilitates the measurement of the volume flow, but also minimizes possible flow noise, since the air channel facing away from the throttle valve can be designed as a downstream sound-absorbing element.

[0025] In a preferred embodiment, the inner flow element is fixed in position. In a further embodiment, the inner flow element is fixed in position at least with respect to the axial direction and / or the inner flow element is fixed in position at least with respect to the tapering and the re-widening. This also improves the appearance, since the flow element and thus all components of the valve always protrude into the space to the same extent.

[0026] Advantageously, the exhaust valve can be designed identically to the intake valve without geometric adaptation. The exhaust valve can be completely identical or it can differ in the shape of the throttle valve, since the exhaust valve is hardly or not visible from the outside anyway in the installed state.

[0027] Advantageously, a space with a plurality of valves can achieve a uniform appearance even when the flow volumes of the valves are adjusted differently. For the reasons stated, the inlet valves and the outlet valves are preferably designed identically, at least with the exception of the shape of the throttle valve.

[0028] Preferably, the casing and / or the tapering and / or the widening again of the flow element are designed rotationally symmetrically. This optimizes the distribution of the outflowing air flow. Preferably, the curved flow channel is annular.

[0029] In a preferred embodiment, the device has a housing which forms the central air duct and has an inner wall which forms the tapering and the re-widening. As a result, the device can be manufactured cost-effectively and compactly.

[0030] In a preferred embodiment, a measuring cell is provided for determining the volume flow. The measuring cell is preferably arranged in the region of the flow cross section which remains the same, ie in the flow channel.

[0031] In a preferred embodiment, the measuring cell has a sensor element which is arranged in the flow channel. This facilitates the determination of the volume flow. V=v×A applies here, where A is the cross section of the flow channel which remains constant. The force or other physical measured variable acting on the sensor element is therefore proportional to the velocity v and thus to the volume flow V.

[0032] The measuring unit can thus be designed simply and cost-effectively. Known sensors for velocity detection can be used, such as hot-wire anemometers. Preferably, a spring-loaded interference element exposed to the flow is used. The return force caused by the spring mechanism can be achieved, the deflection of the spring being equivalent to the force exerted by aerodynamics and thus the volume flow can be calculated.

[0033] Preferably, the inner flow element has a through-opening which extends from the throttle valve to a side opposite the throttle valve. This embodiment has several advantages.

[0034] On the one hand, the measuring unit can be fastened in the interior of the internal flow element in a space-saving manner. In addition, a display can be arranged in the interior, preferably in the middle plane, in order to read out the currently existing volume flow. This can be achieved, for example, by means of a mechanical pointer that moves along a scale according to the existing volume flow.

[0035] On the other hand, in the installed state of the device, the throttle valve can be adjusted via the through-opening. This can be achieved, for example, with a screwdriver, an Allen wrench or other hand tool, which is guided through the through-opening to the adjustment mechanism of the throttle valve. Alternatively or additionally, the throttle valve has a rotating device that enables manual adjustment. The rotating device is preferably arranged at the second throttle valve component. As a result, the volume flow can be changed quickly and in a simple manner.

[0036] In other specific embodiments, both the measuring unit and the throttle valve adjustment device are designed electrically, so that an automatic regulation in accordance with a desired value can be carried out in the interior by means of a controller.

[0037] It is also advantageous that both the scale for the volume flow and the adjusting mechanism of the throttle valve can be reached via the through-opening. This makes it easier to adjust the valve to the desired volume flow.

[0038] Preferably, the through-opening can be repeatedly closed and opened by means of a cover when the device is installed. Preferably, the cover can be removed without tools and can be fastened again. The visual appearance in the room is improved due to the cover. Preferably, the cover surface is approximately flush with the building wall or the room ceiling. The internal flow element is thus preferably closed flush with the ceiling. Preferably, the cover surface is designed to match the building wall, and the cover surface is preferably flat.

[0039] The throttle valve is preferably adjustable by means of a rotary mechanism.

[0040] In a preferred embodiment, the throttle valve has blades that can be rotated relative to one another in order to change the cross section through which the flow can pass. Preferably, the throttle valve is designed with multiple blades in order to improve the effect of the rectifier.

[0041] In one embodiment, a throttle valve according to WO 2022 / 101056 A1 is constructed. In other embodiments, the throttle valve is also rotor-shaped, but has other components. Alternatively, the throttle valve is a baffle or other unit for changing the cross section. However, in a preferred embodiment, the throttle valve always has a curved inlet surface, which forms an aerodynamically favorable body. This characteristic is enhanced in the following way: the outer contour of the throttle element or throttle disk is added to the shape of the rigid throttle element in the unthrottled state so that it enters completely or as completely as possible into the rigid throttle element.

[0042] In a preferred embodiment, the throttle valve can be adjusted manually. In other embodiments, the throttle valve can be adjusted, preferably even regulated, in a motor-driven manner as an alternative or in addition to the manual adjustability.

[0043] Further embodiments are described in the dependent claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Preferred embodiments of the present invention are described below with reference to the accompanying drawings, which are only used for illustration and should not be interpreted as limiting. In the accompanying drawings:

[0045] Figure 1 shows a longitudinal section through a device according to the invention installed in a wall;

[0046] Figure 2 Shows the basis for viewing from below Figure 1 A stereoscopic view of the device;

[0047] Figure 3 Shows the basis for observation from above Figure 1 An exploded view of the device;

[0048] Figure 4 Shows the basis for viewing from below Figure 1 An exploded view of the device;

[0049] Figure 5 Shows the basis for observation from above Figure 1 A perspective view of the device in a first position of the throttle valve; and

[0050] Figure 6 Shows the basis for observation from above Figure 1 A perspective view of the device in a second position of the throttle valve. DETAILED DESCRIPTION

[0051] Figure 1 A valve V according to the invention is shown installed in a wall opening 10 in a wall 11. The wall opening 10 is preferably part of an air distribution network of a building.

[0052] The valve V is an air outlet valve which conducts air from the building space into the wall opening 10 or it is an air inlet valve which directs air from the air distribution network through the wall opening into the building space.

[0053] The valve V is described below as an inlet valve, wherein the valve is designed identically with respect to its function as an outlet valve.

[0054] The valve V has a housing 2 which is held in a wall opening 10. For this purpose, the housing preferably has a circumferential first flange 21, preferably in the form of a flexible sealing ring and / or clamping ring.

[0055] An inner flow element 3 is arranged in the housing 2, which extends toward the building interior. The inner flow element 3 is preferably designed with a through opening and is closed by means of a cover 5. In the example described, the inner flow element 3 is designed essentially hollow with an intermediate cover having a central hole. Thus, there is a through opening extending from the throttle valve to the end that reaches the building space side.

[0056] Preferably, a measuring cell 4 for determining the volume flow is arranged in the inner flow element 3 . A sensor element 41 of the measuring cell 4 projects into the flow channel 8 .

[0057] The flow channel 8 is formed between the inner flow element 3 and the inner wall of the housing 2 .

[0058] In the upper region, ie the region facing away from the building interior, a throttle valve 6 is arranged on the housing 2 . The inner flow element 3 is preferably fastened to the throttle valve 6 .

[0059] The throttle valve 6 has an adjustable mechanism for selectively narrowing the central air passage 24. The central air passage 24 is Figure 3 The central air channel is defined by the inner diameter of the housing 2. The flow-through cross section of the central air channel is defined by the area of ​​the central air channel 24 through which the air flow can flow. The flow-through cross section can be changed by means of the throttle valve 6.

[0060] Downstream in the flow direction of the throttle valve 6, i.e. towards the building interior, the cross section through which the flow can flow can no longer be changed in the central air channel 24. The central air channel tapers and then widens again. This can be achieved by inserting it into the housing 2. Preferably, however, as shown here, the inner wall of the housing 2 is designed to be correspondingly curved.

[0061] The inner wall forms an upper, circumferential first guide surface 250, which faces the throttle valve 6. The inner wall ends in a circumferential projection 251 pointing toward the flow element 3. Following the projection 251 is a lower, circumferential second guide surface 252. The second guide surface 252 is inclined with respect to the longitudinal axis L. The second guide surface is preferably convex, i.e., it is curved toward the longitudinal axis L.

[0062] The outer housing 30 of the inner flow element 3 extends parallel to the second guide surface 252. Together, they form a flow channel 8, which has a cross section over its length that does not change, i.e. remains the same, when the setting of the throttle valve is changed. However, the cross section can vary along the flow direction depending on the embodiment. In particular, the cross section of the outflow opening of the valve V remains unchanged regardless of the change in the flowable cross section in the region of the throttle valve 6.

[0063] The outer housing 30 is preferably designed in a bell-shaped manner and the second guide surface 252 is preferably the negative image of a corresponding bell-shaped shape.

[0064] The valve V is preferably arranged flush with the surface of the wall 11 or it protrudes only insignificantly from the wall, as in Figure 1 . A change in the flowable cross section by means of the throttle valve 6 does not cause a change in the outflow region of the valve V, that is, the axial position of the inner flow element 3 does not change. The position of the inner flow element relative to the wall 11 therefore remains unchanged. As already mentioned, the outflow cross section of the flow channel 8 also does not change.

[0065] exist Figures 2 to 6 The individual components of the valve V according to the invention can be clearly seen in FIG. Figure 3 and Figure 4 The exploded view shows the individual components from two perspective views.

[0066] The housing 2 is substantially cylindrical in shape. The housing has a first housing region 20 and a second housing region 22 with a web 200 pointing upward toward the throttle valve 6. A first circumferential flange 21 is arranged between them. The first flange can be sprayed on, molded in one piece, or fastened to the rest of the housing 2 in another manner.

[0067] A second flange 23 is integrally formed at the lower end of the housing 2, which is preferably rigid. The second flange serves as a stop when the valve V is pushed into the wall opening 10, as in Figure 1 The second flange forms a closure for covering irregularities in the surrounding wall 11 .

[0068] In the example described, the throttle valve 6 is designed with rotor-like blades. As mentioned at the outset, the throttle valve can also be designed in another way.

[0069] The throttle valve 6 shown here has a first throttle valve element 60, a second throttle valve element 61 and a third throttle valve element 62. The second throttle valve element 61 can rotate relative to the first throttle valve element and the third throttle valve element 60, 62 about the valve longitudinal axis L. The first throttle valve element and the second throttle valve element 60, 62 are connected to each other in a rotationally fixed manner.

[0070] The first throttle valve member 60 has a central first hub part 600 and at least three first blades 601 extending radially away from the central first hub part 600. In the example described, there are exactly three blades 601. A flange 602 is molded on the end side of the free end of the first blade 601, which engages in the tab 200 of the housing 2, so that the first throttle valve member 60 is connected to the housing 2 in a rotationally fixed manner.

[0071] The first throttle valve member 60 has a hook 603 protruding downward, which protrudes through a curved, elongated peripheral through-opening 613 in the second hub part 610 of the second throttle valve member 61 and engages in a receiving opening 622 of the third hub part 620 of the third throttle valve member 62. As a result, the first blade 601 is located superimposed on the third blade 621 of the third throttle valve member 62. The first blade and the third blade preferably each constitute a curved surface, in particular a curved inflow surface.

[0072] The second throttle valve part 61 located therebetween has the same number of second blades 611, which extend radially from the second hub part 610. The second blades 611 are preferably flat, unlike the first and third blades 601, 621. The second blades can be twisted relative to the first and third blades 601, 621, so that the through-opening 70 between the blades of the throttle valve, which can flow through, changes in its size. This Figure 5 and Figure 6 Clearly shown in.

[0073] exist Figure 5 In the embodiment, the second blade 611 is significantly twisted relative to the first blade and the third blade 611, 621. The through-opening 70 and thus the variable flow-through cross section of the valve V are relatively small. Figure 6 In the embodiment, the second blade 611 overlaps with the first and third blades 601 , 621 , so that the through-opening 70 and thus the changeable through-flow cross section of the valve V are maximized. Therefore, the through-opening 70 defines the changeable through-flow cross section of the valve V.

[0074] Preferably, a snap hook 612 or another tactile element is present, which, on the one hand, provides feedback to the operator during manual adjustment of the throttle valve and, on the other hand, holds the twisted second blade 611 in its position.

[0075] Preferably, there is an end stop 604 for each second blade 611. In the example described, the end stop 604 is a downwardly projecting side wall at the first blade 601.

[0076] On the underside of the second hub part 610 there is a downwardly projecting adjustment sleeve 614 in the center. The adjustment sleeve is accessible from the side of the valve facing the building wall 11 so that the second throttle valve part 61 can be rotated by means of a hand tool, for example an Allen key.

[0077] The inner flow element 3 is fastened to the throttle valve 6. The inner flow element is preferably connected to the throttle valve by means of a latching element 623. Figure 1 and Figure 3 The latching element 623 can be seen in FIG.

[0078] The inner flow element 3 has a bell-shaped housing 30, which widens away from the throttle valve 6. The outer surface of the housing 30 is preferably flat, that is, smooth. The flow element 3 has a lowermost end side 31, which is preferably flat. The flow element 3 is essentially hollow and open on both end sides. This creates an access from the outside to the adjustment sleeve 614 of the throttle valve 6.

[0079] The measuring unit 4 is arranged in the cavity of the inner flow element 3. The measuring unit comprises a helical spring 40, a sensor element 41 in the form of a pointer and a scale 42. The sensor element 41 is connected to the helical spring 40 at a first end and the helical spring extends from the flow element 3 into the flow channel 8 with an opposite second end. For this purpose, the flow element 3 has a corresponding slot 300 in the housing 30, which can be Figure 4 The scale 42 is fixed in position in the cavity, wherein the scale points downward so that it can be clearly seen by the user in the installed state. Preferably, the scale is arranged on the underside of the intermediate cover 32. Depending on the air flow flowing through the flow channel 8, the position of the sensor element 41 and thus the pointer relative to the scale 42 changes. Thus, the air volume can be read directly or at least calculated. Depending on the type of construction of the scale 42, it is also possible to detect only a change in the air volume.

[0080] The measuring unit 4 shown is only one of a number of possible variants. In another embodiment, the sensor element is rotatably held at the wall of the flow element. A helical spring is provided between the wall and the sensor element, which generates a corresponding reset force. The tip of the sensor element points to the scale again. In the example, the scale is preferably a component placed separately from the flow element, but the component is always in the cavity of the flow element.

[0081] In another embodiment, the sensor element is held linearly displaceably relative to the flow element and is moved along a straight scale. The restoring force is again achieved by means of a helical spring.

[0082] The valve V also has a cover 5 for closing the lower inlet opening of the inner flow element 3. Figure 3 and Figure 4 Preferably, the cover has a flat, round base plate 50 with a preferably flat outer surface 51. On the opposite side, the base plate 50 has ribs 52 protruding upwards for clamping the cover 5 into the second flange 31 of the inner flow element 3.

[0083] The cover 5 can be removed in order to adjust the throttle valve 6 and to determine the current volume flow according to the scale. Figure 2 It can be clearly seen in.

[0084] The device according to the invention allows simple controllability of the volume flow, simple measurement of the volume flow and, when used as an inlet valve, optimal flow distribution.

[0085] Reference numerals list

[0086] 10 Wall openings

[0087] 11 walls

[0088] 2 Shell

[0089] 20 First shell area

[0090] 200 splices

[0091] 21 First flange

[0092] 22 Second shell area

[0093] 23 Second flange

[0094] 24 Central air duct

[0095] 250 first guide surface

[0096] 251 Protrusion

[0097] 252 second guide surface

[0098] 3 Internal flow elements

[0099] 30 housing

[0100] 300 Long Hole

[0101] 31 end side

[0102] 32 Middle plane

[0103] 4 measuring units

[0104] 40 coil spring

[0105] 41 sensor elements

[0106] 42 scale

[0107] 5 Cover

[0108] 50 substrates

[0109] 51 end face

[0110] 52 ribs

[0111] 6Throttle valve

[0112] 60 first throttle valve component

[0113] 600 first hub component

[0114] 601 first blade

[0115] 602 flange

[0116] 603 Hook

[0117] 604 end stop

[0118] 61 Second throttle valve component

[0119] 610 second hub component

[0120] 611 second blade

[0121] 612 buckle hook

[0122] 613 peripheral through opening

[0123] 614 Adjustment sleeve

[0124] 62Third throttle valve component

[0125] 620 third hub component

[0126] 621 third blade

[0127] 622 Accommodate opening

[0128] 623 locking element

[0129] 70 through opening

[0130] 8 flow channels

[0131] V-Valve

[0132] L Longitudinal axis

Claims

1. A device for regulating an air volume flow, in particular an air volume flow in an air distribution network, The device comprises a central air duct (24) with a flow-through cross section and a throttle valve (6) arranged in the central air duct (24), wherein the flow-through cross section (70) can be varied by means of the throttle valve (6), It is characterized in that The device also has an inner flow element (3) with a housing (30), the circumference of which increases in a direction away from the throttle valve (6), and The central air channel (24) has a tapering (251) and a subsequent widening (252) in the region of the flow element, whereby a curved flow channel (8) is produced between the housing (30) of the inner flow element (3) and the widening (252), which ends toward the outside of the device.

2. The device according to claim 1, wherein the device has a housing (2), which forms the central air duct (24) and has an inner wall, which forms the tapering portion (251) and the re-widening portion (252).

3. Apparatus according to claim 2, wherein the housing (2) is substantially cylindrical.

4. The device according to any one of claims 2 or 3, wherein the housing (2) has a first circumferential guide surface (250), a second circumferential guide surface (252) and a projection (251) located therebetween.

5. The device according to claim 4, wherein the first guide surface (250) faces the throttle valve (6).

6. The device according to claim 4, wherein the second guide surface (252) extends parallel to the outer housing (30) of the inner flow element (3).

7. The device according to any one of claims 2 to 6, wherein the housing (2) can be held in a wall or ceiling opening in a clampable manner.

8. The device according to claim 1, wherein the device can be arranged flush with the surface of a wall or ceiling or protrudes only inconspicuously.

9. The device according to claim 1, wherein the flow channel (8) has a cross section over its length which remains constant when the setting of the throttle valve is changed. 10 . The device according to claim 1 , wherein the inner flow element ( 3 ) widens in a bell-shaped manner. 11 . The device according to claim 1 , wherein the re-widening portion ( 252 ) has an inner wall that widens in a bell-shaped manner.

12. An apparatus according to any one of claims 1 to 11, wherein when the flow-through cross-section (70) changes, the internal flow element (3) remains fixed in position in the axial direction of the apparatus with respect to the tapered portion (251) and the re-widened portion (252).

13. The device according to any one of claims 1 to 12, wherein the housing (30) of the flow element (3) and / or the tapered portion (251) and / or the re-widened portion (252) are designed to be rotationally symmetrical.

14. The device according to any one of claims 1 to 13, wherein the device has a housing (2), which forms the central air duct (24) and has an inner wall, which forms the tapering portion (251) and the re-widening portion (252).

15. The device according to any one of claims 1 to 14, wherein a measuring unit (4) is present for determining the volume flow. 16 . The device according to claim 9 , wherein the measuring cell ( 4 ) has a sensor element ( 41 ) which is arranged in the flow channel ( 8 ).

17. The device according to claim 1, wherein the inner flow element (3) has a through-opening which extends from the throttle valve (6) to a side opposite the throttle valve (6).

18. Device according to claim 17 and optionally claim 15 or 16, wherein the measuring cell (4) is fastened in the inner flow element (3).

19. The device according to claim 17, wherein in the installed state of the device, the throttle valve (6) is adjustable via an inlet opening in order to change the throughflow cross section (70). 20 . The device according to claim 17 , wherein the access opening can be repeatedly closed and opened by means of a cover ( 5 ) in the installed state of the device.

21. The device according to claim 1, wherein the throttle valve (6) has blades (601, 611, 621) that can be twisted relative to one another in order to change the through-flow cross section (70).

22. The device according to any one of claims 1 to 21, wherein the throttle valve (6) has a curved inlet surface.

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