DE8902922U1 - Fluid line with pressure measuring unit - Google Patents

Description

Fluid line with pressure measuring unit

The invention relates to a line through which fluid can flow, in the wall of which a first and at least one second measuring point for fluid pressure inside the line are arranged offset from one another in the direction of flow.

It is known to determine the fluid flow through pipes for air conditioning and/or ventilation systems by means of attached pressure measuring units. A measuring unit consists of several pressure measuring points, each of which is installed in the pipe path at different or spaced-apart pipe cross-sections. The flow rate of the fluid flowing through the pipe can be calculated from the pressure difference between the two measuring points offset in the direction of flow. If the flow or flow profile across the pipe cross-section exhibits irregularities or inhomogeneities, which are caused, for example, by elbow pipe sections or the like located nearby, the accuracy, reliability and safety of the pressure or flow measurement can be impaired with the known arrangement.

Consequently, the problem underlying the invention is to improve the measuring operation in a pressure measuring unit connected to a fluid line in terms of reliability, availability, safety and accuracy. To solve this problem, the invention proposes to provide additional, similar measuring points in a fluid line with the features mentioned at the beginning, which are arranged in pairs with the first and/or the second measuring point and diametrically opposite them.

Several pairs of pressure measuring points are arranged in the pipe wall, each axially offset from one another. According to the invention, each pair comprises at least two diametrically opposed pressure measuring points, so that the fluid pressure is measured at different points on the same pipe cross-section. Flow irregularities that occur in the vicinity of one of the two pressure measuring points arranged in the pair

i| can be eliminated by taking into account the measurement result

ness of the other pressure measuring point assigned in pairs

' 10 balanced, averaged or compensated. In addition, the arrangement of two independent flow points in the same line cross-section creates redundancy, which increases the reliability and availability of the measuring operation overall.
15

. Due to the measuring point arrangement according to the invention,

The fluid line can be designed with a variety of cross-sectional shapes. A practical design consists in

Fluid line is to be provided with a circular cylindrical pipe section with a longitudinally welded outer casing. As the weld seams run in the direction of the pipe's longitudinal axis, this makes it particularly easy to manufacture. An alternative embodiment of the invention is to

to use a circular cylindrical pipe section, the outer casing of which has a bent or flanged seam running along a helical line. The wall of the pipe can consist of one or more spirally wound sheet metal parts, the edges of which are connected to one another by bending. This particularly stabilizes the pipe cross-section mechanically.

In order to be able to connect several pipe sections in their longitudinal direction, in their end areas

Grooves or slots concentric to the pipe center axis are arranged in the outer casing. Lip seals, for example, can be inserted into these recesses in order to create a fluid-tight coupling of several pipe sections one behind the other.

In air conditioning or ventilation systems, it is often desirable to regulate the flow of fluid. From this point of view, a further development of the invention consists in arranging a throttle or shut-off device in the direction of flow behind the measuring point arrangement. This allows the pressure in the fluid line and the flow speed to be influenced in a targeted manner. To increase the regulation accuracy, the measuring points and the throttle device can be coupled to one another, e.g. within the framework of a control or regulating circuit. A practical implementation option for the throttle device is in the form of a butterfly valve, the throttle flap of which can be rotated about an axis transverse to the flow. The throttle flap serves as a damper of the flow energy.

The invention is particularly advantageously further developed in that a section of the fluid line is designed as a Venturi tube, with a pair of measuring points being arranged at the entrance to the Venturi tube and at the narrowest point of the Venturi tube. This further development of the invention by combining it with a Venturi tube is particularly useful for highly accurate flow measurement. A special development of this idea within the scope of the invention consists in the butterfly valve being arranged in the Venturi tube section. Since this section has a smaller cross-section compared to the neighboring pipe sections, a valve with a relatively small throttle valve cross-section can be used, in particular

when, in the preferred design, the throttle valve is placed in the area of the narrowest cross-section of the Venturi tube section.

Even when the butterfly valve is fully open, with the broad sides of its throttle valve aligned axially or in the direction of flow, the throttle valve triggers turbulence, disturbances, irregularities or inhomogeneities in the flow profile of the fluid, at least in its immediate vicinity, which result in a loss of pressure. This problem is taken into account by a particularly advantageous embodiment of the invention, according to which the throttle valve is arranged in such a way that its axis of rotation forms an angle of 45° at least with the nearest connecting line of measuring points assigned to one another in pairs - viewed in the direction of flow. This means that the greatest possible distance from the throttle valve and therefore from the adjacent areas of reduced pressure is achieved for each pressure measuring point. This arrangement has a beneficial effect on the accuracy of flow measurements in particular. In this case, it is fundamentally within the scope of developments according to the invention that - viewed in the direction of flow - the connecting lines of measuring points assigned to each other in pairs are aligned or overlap, i.e. lie in a single axial plane.

In order to protect the Venturi tube section important for flow measurement from the influences of the harsh environment and to achieve as uniform an outer contour of the fluid line as possible, according to another design the Venturi tube section is concentrically surrounded by an outer jacket section, the cross section of which is identical to the line sections adjoining the Venturi tube.

is congruent. The Venturi tube section forms an inner body around which an outer casing extends.

In order to be able to evaluate two pairs of pressure measuring parts lying opposite one another, it is advisable for their outputs to be connected via flexible cable hoses or tubes, preferably made of plastic, and to be externally accessible via a common connection point.

Further features, details and advantages emerge from the following description of preferred embodiments of the invention and from the drawings. In each case, they show in a schematic representation:

^Fig. 1 is a longitudinal view of a fluid line according to the invention,

Figure 2 is a longitudinal view of a modified fluid line,

Figure 3 is an enlarged view of the section surrounded by circle III in Figure 2,

Fig.4-6 Longitudinal views of further embodiments of the fluid line according to the invention, and

Figure 7 shows a cross section approximately along the line VII-VII in

Figure 6.
30

The fluid line shown in Figure 1 has a tubular, outer casing 1, which is held together by weld seams (not shown) running in the direction of the central longitudinal axis 2. The end sections 3 of the

The fluid line sections shown are each provided with grooves 4 running concentrically around the longitudinal axis 2, into which sealing rings, for example, can be inserted. The end sections 3 can thus serve as connecting pieces for further pipe sections. Between the end sections 3 there is a known Venturi tube section 5 which forms an inner body 6 protected by the outer casing 1. In the area of the entrance to the Venturi tube section 5 as well as in the area of its narrowest cross section, two diametrically opposed pressure measuring points 7a, 7b and 8a, 8b are installed in the wall of the outer casing 1 or the Venturi tube section 5. To measure the flow 9 based on the pressure difference between the Venturi tube entrance (measuring points

7) and its narrowest cross-section (measuring points 8), the opposite measuring points 7a and 7b or 8a and 8b are also functionally assigned to each other to form a measuring point pair.

The embodiment according to Figures 2 and 3 differs from that according to Figure 1 in that the seams 10 of the outer casing 1 run in a helical manner. According to the detail shown enlarged in Figure 3, the seam 10 is realized by means of a flange 11, in which the adjacent edges 12a, 12b of sections of the outer casing are bent into one another.

The embodiments according to figures ·? ana 5 differ from the previous ones by a throttle or damping element 13 located inside the line, which - viewed in the flow direction 9 - is arranged behind the Venturi tube section 5, i.e. immediately after its gradually expanding cross-section outlet. The throttle element 13 is in the example as a butterfly

lings valve is designed with a flap 15 which can be rotated 14 transversely to the flow direction 9 and which has the shape of a flat, extended circular ring and penetrates approximately the entire, largest inner diameter of the fluid line.
5

In contrast, the design according to Figure 6 has the difference that the throttle element is positioned within the Venturi tube section in the area of its narrowest cross-section. In this example shown, the rotation axis 14 is realized by a rod 16 that runs diametrically through the flap 15, the Venturi tube section 5 and the outer casing 1 around it, which is rotatably mounted in the walls of the outer casing 1 and the Venturi tube section 5. Its end protruding from the fluid line is rigidly connected to an adjusting lever 17.

According to the cross-sectional view of Figure 7 corresponding to Figure 6, in a preferred embodiment the rod 16 and thus the axis of rotation 14 are arranged rotated by an angle 19 of approximately 45° relative to the connecting lines 18 of two opposing pressure measuring points 7a or 7b or 8a or 8b, which run diametrically through the fluid line. Its apex lies approximately on the central longitudinal axis 2 of the fluid line (see Figure 6). According to Figure 7, the throttle element is in its fully open position, so that due to the sectional view according to VII-VII in Figure 6, the upstream part of the flap 15 is in axial alignment with the rod 16 (hidden by it in Figure 7). (Accordingly, the connecting lines of the measuring point pair 7a, 7b for the larger cross-section and the measuring part pair 8a, 8b for the smaller cross-section lie in a common, axially running plane or alignment. As schematically indicated in Figure 7,

For each pair of measuring points, the outputs of opposite measuring sensors 7a, 7b or 8a, 8b are combined by means of flexible, approximately semicircular cable hoses 20, 21 and led to the outside via connectors 22 opening into them.

Claims (12)

«ft * · ft ft > · · Protection claims 1. Fluid line, in the wall of which a first and a second measuring point for fluid pressure are arranged offset in the direction of flow, characterized in that the first (7a) and/or second measuring point (8a) are each assigned further, equally effective measuring points (7b, 8b) in pairs and are arranged diametrically opposite one another.
IO 2. Fluid line according to claim 1, characterized by a design as a circular cylindrical pipe section with a longitudinally welded outer jacket (1, Fig. 1) 3. Fluid pipe according to claim 1, characterized by a design as a circular cylindrical pipe piece, the outer casing (1) of which has a fold or a flanged seam (10, 11), each of which runs along a helical line (Fig. 2). 4. Fluid line according to claim 2 or 3, characterized by grooves or grooves (4) arranged in the end regions (3) and concentric with the pipe center line (2). in the outer jacket (1).
25 5. Fluid line according to one of the preceding claims, characterized by a throttle element (13) arranged behind the measuring points (7, 8) in the flow direction (9). 6. Fluid line according to one of the preceding claims, characterized by a butterfly valve arranged in the flow direction (9) behind the measuring parts (7, 8). ling valve, the throttle valve (15) of which can be rotated about an axis ,y (14) transverse to the flow (9). 7. Fluid line according to one of the preceding claims, characterized in that a line section is designed as a Venturi tube (5), at the inlet and at the narrowest cross section of which a pair of μωβ parts (7a, 7b b«w. 8a, 8b) are arranged. lü 8. Fluid line according to claim 6 and 7, characterized in that the butterfly valve is arranged in the Venturi tube section (5), preferably in the region of its narrowest cross section. 9. Fluid line according to claim 6 and 7 or 8, characterized by a throttle valve (15) arranged in such a way that its axis of rotation (14) is offset by 45° relative to the connecting line(s) (18) of pairs of measuring points (7a, 7b or 8a, 8b) assigned to one another (19) lies. 10. Fluid line according to one of the preceding claims, characterized in that in the flow direction (9) the connecting lines (18) of measuring points (7a, 7b or 8a, 8b) assigned to one another in pairs are aligned with one another. 11. Fluid line according to claim 7 and one of the preceding claims, characterized in that the Venturi tube section (5) is concentrically surrounded by an outer casing section (1), the cross section of which is congruent with the line sections (23) adjoining the Venturi tube (5). 12. Fluid line according to one of the preceding claims, characterized in that the outputs of measuring points (7a, 7b, 8a, 8b) assigned to one another in pairs are combined via flexible cable hoses (20, 21), preferably made of plastic, and are externally accessible via a common connection point (22).