Device for determining the flow rate of a medium in a pipeline

Abstract

The invention relates to a device (1) for determining the flow rate of a medium (2) in a pipeline (3), wherein the device (1) has a vortex tube (4), an evaluation unit (18), a first temperature sensor (12) and a first pressure sensor (13), wherein the first temperature sensor (12) and the first pressure sensor (13) are arranged upstream of an inlet opening (11) of the vortex tube (4) and are designed to detect a temperature and a pressure of the medium (2), wherein a second temperature sensor (14) is arranged in a part (6) of the vortex tube (4) with the colder partial flow (7) and a third temperature sensor (15) is arranged in a part (8) of the vortex tube (4) with the warmer partial flow (9), wherein at least one characteristic map is stored in the evaluation unit (18), by means of which the flow rate is determined as a function of the sensor values.

Description

[0001] The invention relates to a device for determining the flow rate of a medium in a pipeline.

[0002] In a wide variety of applications, knowing the flow rate of a medium, especially a gaseous medium, is important. Various methods for determining the flow rate are known.

[0003] Examples of these methods include the Coriolis measuring principle, the pressure difference measurement principle using an orifice plate, and the vortex meter measuring principle. The latter, for example, counts the vortices caused by a body. All of these measuring principles become more cost-intensive with increasing temperature and pressure. Furthermore, the harsh operating conditions impair measurement accuracy. In pressure difference measurement, the orifice plate causes a pressure difference, which cannot be neglected when determining the system's characteristic curve.

[0004] From EP 3 754 305 A1 a generic device for determining the flow rate of a medium in the pipeline is known.

[0005] A similar device is known from the article Cebeci, Ismail et al.: The effects of orifice nozzle number and nozzle made of polyamide plastic and aluminum with different inlet pressures on heating and cooling performance of counter flow Ranque-Hilsch vortex tubes: An experimental investigation. In: International Journal of Refrigeration, No. 72, 2016, pp. 140-146. - ISSN 0140-7007.

[0006] The invention is therefore based on the technical problem of creating a robust device for determining the flow rate of a gaseous medium in a pipeline.

[0007] The solution to the technical problem is achieved by a device having the features of claim 1. Further advantageous embodiments of the invention emerge from the subclaims.

[0008] The device for determining the flow rate of a gaseous medium in a pipeline comprises a vortex tube, an evaluation unit, a first temperature sensor, a second temperature sensor, a third temperature sensor, and a first pressure sensor. The first temperature sensor and the first pressure sensor are arranged upstream of an inlet opening of the vortex tube and are designed to detect a temperature and a pressure of the medium. The second temperature sensor is arranged in a part of the vortex tube with the colder partial flow, and the third temperature sensor is arranged in a part of the vortex tube with the warmer partial flow. At least one characteristic map is stored in the evaluation unit, by means of which the flow rate is determined depending on the sensor values. The characteristic map is determined in advance, for example, using empirical measurements. The characteristic maps can be tailored to a specific medium.The device is suitable for a wide variety of gaseous media. Temperature sensors are relatively inexpensive, robust, and have a wide measuring range.

[0009] In this case, a second pressure sensor is additionally arranged in the part of the vortex tube with the colder partial flow, wherein the evaluation unit is designed to compensate for process deviations using the data from the second pressure sensor. This is based on the following consideration: If the temperature of the first temperature sensor and the pressure of the first pressure sensor are constant, the temperature difference between the second and third temperature sensors depends exclusively on the flow rate and the pressure at the second pressure sensor must behave in the same way, i.e. an increasing flow rate must correlate with an increased pressure at the second pressure sensor. If, on the other hand, the temperature difference changes, but the pressure at the second pressure sensor remains the same, this indicates that another parameter (e.g. the pressure and / or the temperature at the inlet) has fluctuated.

[0010] On the output side, the two partial flows are preferably reunited in the vortex tube and fed back into the pipeline.

[0011] In one embodiment, a mixing valve is located at the outlet of the vortex tube. This mixing valve allows the two partial streams to be homogenized, thus preventing the formation of stratifications of the medium with different temperatures.

[0012] In an alternative embodiment, a Y-shaped pipe section is arranged at the outlet of the vortex tube to combine the two partial flows.

[0013] In a further embodiment, the vortex tube is designed as a controllable vortex tube with an electric, pneumatic or electro-pneumatic drive. The controllable vortex tube, for example, keeps the temperature of the cold partial flow constant. The controllable vortex tube is designed with a movable spindle and a cone, a diaphragm or other geometry to change the cross-section so that a constant temperature is achieved in the tube. Particularly when measuring the flow of condensable media such as steam or similar gases, the appropriate control using a controllable vortex tube prevents condensation of the working medium. The control must be designed so that for these condensable media, the temperature of the cold partial flow is calculated from the saturation temperature of the working medium at the corresponding pressure (measured with the pressure sensor in the colder partial flow) plus a temperature difference (e.g.5 K). When measuring a non-condensable medium such as air or similar, a constant superheat of the warm partial flow can be maintained for control purposes, so that the temperature at the warm partial flow is equal to the determined temperature at the inlet of the medium plus a predefined temperature difference (e.g. 20 K).

[0014] In a further embodiment, a fourth temperature sensor is arranged behind the outlet of the vortex tube so that the temperature of the outflowing medium can be controlled.

[0015] In another embodiment, the gaseous medium is water vapor.

[0016] The invention is explained in more detail below using preferred embodiments. The figures show: Fig. 1 a device for determining the flow rate of a medium in a pipeline in a first embodiment and Fig. 2 a device for determining the flow rate of a medium in a pipeline in a second embodiment.

[0017] In the Fig. 1 schematically shows a device 1 for determining a flow rate of a medium 2 in a pipeline 3. The device 1 has a vortex tube 4. The vortex tube 4 has an inlet 5, a part 6 with a colder partial flow 7, a part 8 with a warmer partial flow 9 and an outlet 10. A first temperature sensor 12 and a first pressure sensor 13 are arranged upstream of the inlet 5 with its inlet opening 11. A second temperature sensor 14 is arranged in part 6 and a third temperature sensor 15 is arranged in part 8. A second pressure sensor 16 is arranged in part 6. A mixing valve 17 is arranged at the outlet 10 of the vortex tube 4. Finally, an evaluation unit 18 is shown, in which at least one characteristic map is stored.

[0018] The flow rate ṁ of the gaseous medium 2 depends on the pressure p1 at the first pressure sensor 13, the inlet temperature T1 at the first temperature sensor 12 and the temperature difference ΔT between the warm partial flow 9 and the cold partial flow 7. The temperature difference ΔT is determined from the difference between the measured values ​​T3 at the third temperature sensor 15 and the measured values ​​T2 at the second temperature sensor 14. This relationship is stored in the characteristic map of the evaluation unit 18. The data p2 of the second pressure sensor 16 is used to compensate for process deviations and to determine the characteristic map of the temperature change as a function of the pressure flow rate ṁ for variable inlet conditions for pressure and temperature.

[0019] In principle, the second pressure sensor 16 can also be arranged on the part 8 with the warm partial flow 9. However, due to the higher temperatures, the requirements are somewhat higher, so the arrangement in the colder partial flow 7 is more cost-effective.

[0020] In the Fig. 2 shows a further embodiment of the device 1, which essentially corresponds to the embodiment according to Fig.1. The only difference is that the vortex tube 4 is controllable. Depending on the medium 2 (condensable or non-condensable), the temperature sensor of the cold or warm partial flow is used for control, so that the corresponding temperature remains constant and a given temperature difference arises between the cold and warm partial flow. In the example shown, the temperature sensor 14 of the colder partial flow 7 is used for control. The vortex tube 4 has a drive 19 with a spindle 20 and a cone 21. Furthermore, a fourth temperature sensor 22 is arranged at the outlet 10 of the vortex tube 4. List of reference symbols 1 device 2 Medium 3 pipeline 4 vortex tube 5 Entrance Part 6 7 colder partial flow Part 8 9 warmer partial flow 10 Exit 11 Entrance opening 12 first temperature sensor 13 first pressure sensor 14 second temperature sensor 15 third temperature sensor 16 second pressure sensor 17 Mixing valve 18 Evaluation unit 19 Drive 20 spindle 21 pins 22 fourth temperature sensor

Claims

[1] Device (1) for determining the flow rate of a medium (2) in a pipeline (3), wherein the device (1) comprises a vortex tube (4), an evaluation unit (18) and three temperature sensors (12, 14, 15), wherein the first temperature sensor (12) is arranged in front of an inlet opening (11) of the vortex tube (4) and is designed to detect a temperature of the medium (2), wherein the second temperature sensor (14) is arranged in a part (6) of the vortex tube (4) with the colder partial flow (7) and the third temperature sensor (15) is arranged in a part (8) of the vortex tube (4) with the warmer partial flow (9), wherein the flow rate is determined in the evaluation unit (18) as a function of the sensor values, characterized byin that the device (1) has a first pressure sensor (13) and a second pressure sensor (16), wherein the first pressure sensor (13) is arranged in front of the inlet opening (11) of the vortex tube (4) and is designed to detect the pressure of the medium (2), wherein the second pressure sensor (16) is arranged in the part (6) of the vortex tube (4) with the colder partial flow (7), wherein at least one characteristic map is stored in the evaluation unit (18), by means of which map the flow rate is determined as a function of the sensor values ​​of the temperature sensors (12, 14, 15) and of the first pressure sensor (13), wherein the evaluation unit (18) is designed to compensate for process deviations by means of the data of the second pressure sensor (16). [2] Device (1) according to claim 1, characterized by that a mixing valve (17) is arranged at an outlet (10) of the vortex tube (4). [3] Device (1) according to claim 1, characterized bythat a Y-shaped pipe section is arranged at an outlet (10) of the vortex tube (4). [4] Device (1) according to one of the preceding claims, characterized by that the vortex tube (4) is designed as an adjustable vortex tube (4). [5] Device (1) according to claim 4, characterized by that the adjustable vortex tube (4) has a drive (19), a spindle (20) and a cone (21). [6] Device (1) according to claim 5, characterized by that the drive (19) is designed to keep the temperature of the colder partial flow (7) constant. [7] Device (1) according to one of the preceding claims, characterized by that a fourth temperature sensor (20) is arranged behind the outlet (10) of the vortex tube (4). [8] Device (1) according to one of the preceding claims, characterized by that the medium (2) is water vapor.

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