FI59175B - MAINTENANCE FOR TREATMENT OF TRYCK DIFFERENCES AND VOLUME AVIA MEDIUM STROEMNING - Google Patents

Description

R3r * l ΓβΊ «« ANNOUNCEMENT rQ17r JHa lBJ (11) UTLÄGGNINGSSKRIFT ^ ^ $ (45) ^ w ^ (51) Kv.llu / lm.a.3 o 01 P 5/14 FINLAND — FINLAND <*) Pat «nttlhtk «Mui - PK« ntm6lutinf 790233 (22) H * k * mltjrfUvI — Amttknlnpd »* 25.01.79 * * (23) The beginning of the cloud — Glltfghttsdig 25.01.79 (41) Become Public - Blivlt offcntllg 26.07.80

Patent and Registration Office ... ......... .

_ _, (44) Nihttvikslpunon | -

Patent · oeh registerstyrelsen AinMca »utiagd och utl. Finland (Fl) (72) Pauli Grönberg, Espoo, Finland-Finland (Fl) (7 * 0 Seppo Laine (5 * 0 Measuring device for measuring the pressure difference and the volume flow of a medium in a flow channel - Measurement of the difference between the flow rate and the volume flow in the medium flow) The present invention relates to a measuring device for measuring the pressure difference and the volume flow of a medium in a flow channel, which device comprises - an annular flow resisting plate arranged substantially coaxially in the flow channel so as to leave an opening in the plate, with a plate on either side of it and with a number of openings, such as relatively small holes or notches, for detecting the pressure on both sides of the plate, and measuring means connected to tubular members for measuring the difference in pressure across the plate.

Previously known volumetric flow measurement methods and devices require a virtually undisturbed flow profile at the measurement point in order for the measurement error to be small enough with a reasonable amount of work. In general, in practical installation cases, the flow profile is not sufficiently undisturbed without special flow straightening and smoothing devices, because the flow channels do not have sufficiently long straight channel sections where the flow profile would have time to equalize. Thus, the measurement accuracy has remained poor. In some cases, a reliable measurement result has not been reasonably achievable.

In the past, there have been no measuring and control devices that can be used to measure and adjust the volume flows of ventilation systems to the designed values with sufficient effort and precision, even under disturbed flow conditions.

2,59175

Today, more than half of the energy loss in buildings is due to ventilation. In the future, energy saving measures in buildings will require sufficiently precise management of energy flows. This is not possible unless the volume flows (= energy flows) of the air exchange plants can be measured more reliably and adjusted more easily.

The object of the invention is to provide a volume flow measuring device for a medium flow, which is primarily suitable for measuring the air flows of a ventilation plant significantly more accurately than the current practice, even when the flow profile is strongly disturbed. The measuring device is intended for fixed installation in a ventilation system. The measuring device can be used in various structural shapes in circular, oval, rectangular and other shaped flow channels and openings.

With regard to the state of the art related to the invention, reference is made to the applicant's previous Finnish patent application No. TÖOT ^ + O. It is an object of the present invention to further develop the measurement methods and apparatus disclosed in the aforementioned patent applications.

It is a particular object of the invention to provide a measuring device which, when detecting a pressure difference, provides an even more accurate and larger reading and thus a higher volumetric flow measurement accuracy. It is also intended to provide greater measurement accuracy, especially in highly disturbed, e.g. asymmetric, flow profiles. In any case, the device according to the invention easily achieves a measurement accuracy of better than 5 · ..10%, even in difficult conditions.

In order to achieve the above and later objects, the invention is mainly known for an annular flow opening between the outer circumference of an annular plate and the inner surface of the channel.

According to a preferred embodiment of the invention, the measuring device comprises an annular plate with which the necessary measurable pressure difference is obtained. The outer radius of this flange is substantially smaller than the inner radius of the measuring channel. Attached to both sides of said plate are tubular members provided, preferably on both sides, with small-diameter holes through which pressure is detected on both sides of the flow resistance. Preferably, said annular plate and the tubular members attached thereto are arranged coaxially with the flow channel.

With the measuring device according to the invention, e.g. the following practical advantages: - flow disturbances do not significantly affect the operation and accuracy of the measuring device, 3 59175 - the volume flow can be easily determined with a single differential pressure measurement, - the measuring device can be used at both low and high flow rates - the measured pressure difference is large compared to the flow resistance , simple design, - the measured pressure difference remains stable, the measuring device provides sufficient measuring accuracy even in disturbed flow - the measuring device is suitable for use in flow ducts or openings of different cross-sections, eg in ventilation system blowers and outlets, - measuring device is suitable for both gas and liquid volumes - the direction of flow has no effect on the operation of the measuring device, - the measuring device has no need for space outside the duct or opening, is also suitable for use as a volume flow control device. in the so-called together the so-called. as a measuring control device.

The invention will now be described in detail with reference to two different embodiments of the invention shown in the figures of the accompanying drawing, to the details of which the invention is not limited.

In the drawing, Figure 1 shows an axial central section of a measuring device according to the invention fitted in an air flow duct.

Fig. 2 shows the same as Fig. 1 in a partial section perpendicular to the flow direction.

Fig. 3 shows, in a manner similar to Fig. 2, an embodiment of the invention used in a cross-sectional channel of rectangular cross-section.

4,591 75

Figure 4 shows a cross-sectional view of a detailed implementation of a measuring device according to the invention.

According to Figures 1 and 2, the measuring device according to the invention consists of an annular plate 10, on both sides of which annular tubular members 12 are attached, the interior of which is connected by pipes 14 outside the channel 16 to hoses 15 leading to a pressure gauge. The annular tubular members 12 preferably have small diameter holes 13 on both sides which open substantially perpendicular to the flow direction F. Through said small holes, a pressure difference A p is obtained, which is provided by a flow resistance, in this case an annular plate. With regard to the measurement method according to the invention, reference is made in this connection to the applicant's earlier Finnish patent application No. 780740.

The average diameter c of the annular tubular members 12 and the annular plate 10 is substantially smaller than the diameter d of the flow channel 16. The latter dimension d is considerably larger than the outer diameter b of the annular plate 10. Thus, according to the invention, there is an annular space B between the inner surface of the flow channel 16 and the outer edge of the annular plate 10, through which the flow can pass. The annular plate 10 has an opening A with a diameter of a. A second part of the flow channel flow F passes through this opening A. The above dimensions a, b, c and d are chosen so that the highest possible measurement accuracy is achieved under different measurement conditions. An example of a suitable dimensioning is the dimensions shown in the figures. Then a large d / c ^ 1.3.

According to Figure 3, the measuring device according to the invention is arranged in a channel 16 'with a rectangular cross-section. In this embodiment, the flow resistor is a ring plate 10 ', which is also rectangular in shape with an opening A' in the middle and a ring space B 'inside the channel 16' outside it.

The tube members 12 ', located on both sides of the annular plate 10' as described above, are provided with small-diameter holes 13 on both the outside and the inside, through which a representative pressure difference (Λρ) is obtained in this case from the rectangular flow channel 16 '.

The notations in Figures 1, 2 and 3 have mutual dimensions of the flow channel 16,16 'and the ring plate 10,10', preferably in the following range 591 75 5 1 <- - 3 and 1 <- 3. One suitable dimension is -1.3.

c c c

Figures 3 show the same dimensions as in Figure 1. Dimensions a, b, c and d illustrate the above-mentioned horizontal dimensions of the rectangular ring and the corresponding vertical dimensions a ', b', c 'and d'. According to Figure 3, the walls of the channel 16 'and the rectangular annular plate 10' are coaxial.

According to Figure 4, two tubular members 12 'are attached to the annular plate 10. This attachment is effected by bending the strips formed by the perforations 19 made in the material of the ring plate 10 on the shoulders at the other edge of the tubular members 12 '. The side 18 of the tubular members 12 'opposite to the shoulders 17 is planar. The tubular members have small diameter holes 13 as described above. The profile shape of the tubular member 12 'according to Figure 4 and the fastening of the tubular member as shown are particularly preferred embodiments of the invention.

Although only the small-diameter perforation 13 of the annular tubular member 12 has been discussed above, it will be appreciated that instead of perforation, a corresponding narrow slit or several successive slits or perforations of different shapes may be used.

The measuring device according to the invention can be applied to very different channel cross-sections, even those in which the channel walls are formed as combinations of planar and curved walls.

Also within the scope of the invention are applications in which more than one non-closed ring shape of a pair of tube member-flow resistor plates as described above is used. One such suitable embodiment of the invention is such that two or more nested annular plates with a pair of pipe members 12 corresponding to its cross-sectional shape are arranged in the flow channel, so that an annular flow space remains between these annular plates as well as between the outer annular plate and the channel wall.

The invention is in no way narrowly limited to the details described above by way of example only, which may vary within the scope of the inventive idea defined by the following claims.

Claims (2)

6,591 75 A measuring device for measuring the differential pressure and the volume flow of a medium flow in a flow channel (16) ,. which device comprises an annular flow-resisting plate (10, 10 ') arranged substantially coaxially with the flow channel (16) so as to leave an opening (A) in the plate (10, 10'), at least two tubular members (12, 12 ') or the like, arranged substantially coaxially with the plate (10, 10) on either side thereof and having a plurality of openings (13), such as relatively small holes or notches, for detecting the pressure on both sides of the plate (10, 10 ') and measuring the pressure means connected to the tubular members (12, 12 ') for measuring the pressure difference across the plate (10, 10'), characterized by an annular flow opening (B) between the outer circumference of the annular plate (10, 10 ') and the inner surface of the channel (16). Measuring device according to claim 1, characterized in that the outer diameter or outer dimension (b) of said annular plate (10, 10 ') is substantially smaller than the diameter (d) of the flow channel (16, 16').