System for measuring time-resolved flow-through processes of a medium and method for determining the coefficient of thermal expansion using said system

Abstract

The present invention relates to a time-resolved flow-through process measurement system for a medium, comprising an inlet (12), an outlet (14), and a flow meter (10) arranged between the inlet (12) and the outlet (14), comprising at least a pump (48), a density sensor (50), a temperature sensor (51), and electrical or electronic components. To avoid having to measure the density at exactly the same temperature as the volume, the present invention proposes that the density sensor (50) or a conduit section (56) immediately upstream of the density sensor (50) leading to the density sensor (50) be in heat-conducting contact with heat-generating electrical or electronic components, and that the rotation speed of the pump (48) be controlled. Correspondingly, the present invention relates to a method for determining the coefficient of thermal expansion, in which the density and temperature of a medium heated by a heat-generating electrical or electronic component are measured by a density sensor (50) and a temperature sensor (51) at two different rotation speeds of the pump (48), and the coefficient of thermal expansion is calculated from the measurements of the density sensor (50) and the corresponding measurements of the temperature sensor (51).

Description

[Technical field]

[0001] The present invention relates to a time-resolved flow-through process measuring system for a medium, which comprises an inlet, an outlet and a flowmeter arranged between the inlet and the outlet, which comprises at least a pump, a density sensor, a temperature sensor and electrical or electronic components, as well as a method for determining a thermal expansion coefficient using the time-resolved flow-through process measuring system for a medium. [Background technology]

[0002] Systems of this kind have been known for many years and are used, for example, for injection quantity measurement in internal combustion engines. For example, DE 1 798 080 describes an electronically controlled flowmeter with an inlet and an outlet, between which a rotary displacer in the form of a gear pump is arranged and in a conduit parallel to the displacer a piston is arranged in a measuring chamber. To determine the flow rate, the displacement of the piston in the measuring chamber is measured by means of an optical sensor. Based on this signal, the speed of the gear pump is continuously readjusted in the evaluation and control unit so that, if possible, the piston is always returned to its starting position so that only a small flow occurs in the bypass conduit. The flow rate within a specified time interval is thus calculated from the number of revolutions or partial revolutions of the gear pump, measured by an encoder, and the known delivery volume of the gear pump during one revolution.

[0003] A flow measuring device constructed in such a manner is also described in German Patent No. 10331228. In order to determine the exact injection flow curve, the gear pump is respectively set to a constant speed before the injection starts, and then the movement of the piston is measured and used to determine the injection curve.

[0004] In order to further avoid measurement errors due to fluctuations in the density of the medium being measured, a system for measuring the time-resolved flow-through process of a medium is described in EP 3073228 A1, in which a conduit section of the flow meter can be bypassed using a bypass conduit in which a pump and a density sensor are arranged in series so that an accurate statement can be made about the existing density of the medium being measured at the correct time, which can be used to calculate the mass flow rate from the measured volumetric flow rate.

[0005] It is also known from DE 10 2010045521 A1 to determine the thermal expansion of a fuel by introducing the fuel into a measurement volume and supplying the fuel in the measurement volume with energy. The pressures in the initial and final states are measured and the thermal expansion is calculated from the pressure difference. The measurements thus obtained can also be used to draw conclusions about the mixture of substances used.

[0006] In measuring instruments currently available on the market, in order to avoid conversion to the temperature at which the volumetric flow is measured, an attempt is made to determine the density as accurately as possible at the temperature at which the volumetric flow is also measured, since for such a conversion the exact coefficient of thermal expansion must be known. It is also not possible to convert the measured volumetric flow to the volumetric flow at the reference temperature without the coefficient of thermal expansion, which requires a corresponding pretreatment of the medium. However, it has been shown that a premeasurement of the coefficient of thermal expansion is often not sufficient, since the composition of the medium to be measured changes to a certain extent. Furthermore, especially due to miniaturization, there are often heat-generating components in the vicinity of the density sensor, which causes the problem that the temperature at the density sensor differs from the temperature of the medium at the flowmeter itself. This leads to the need for a conversion to volume or density at the gear temperature, for which the exact coefficient of expansion must be known. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] German Patent No. 1798080 [Patent Document 2] European Patent Publication No. 3073228 [Patent Document 3] German Patent Publication No. 102010045521 Summary of the Invention [Problem to be solved by the invention]

[0008] It is therefore an object of the present invention to provide a time-resolved flow-through process measuring system for a medium, as well as a method for determining the thermal expansion coefficient using said system, with which the thermal expansion coefficient can be determined as accurately as possible without the need to use additional measuring devices for this purpose or to measure a separate sample, and which leads to improved measurement results compared to known systems and methods in that it can be used in the calculation of a standardized volumetric flow-through or mass flow rate. In particular, the object is to avoid the need to measure the density at exactly the same temperature as the volume in order to obtain an accurate measurement value. [Means for solving the problem]

[0009] This problem is solved by a system for time-resolved flow-through process measurement of a medium having the features of claim 1 as well as a method for determining the thermal expansion coefficient using the system according to claim 11.

[0010] For a time-resolved flow-through process measuring system for a medium, this object is solved in that the density sensor or the conduit section leading to the density sensor immediately upstream of the density sensor is in heat-conducting contact with a heat-generating electric or electronic component and the pump is speed-controlled, because with such an arrangement it is possible to carry out the method according to the invention, in which the density and temperature of the medium heated in the heat-generating electric or electronic component are measured with a density sensor and a temperature sensor at two different rotation speeds of the pump, and the thermal expansion coefficient is calculated from the measured values ​​of the density sensor and the associated temperature sensor. Usually, the rotation speed is permanently changed and a number of measurements are made accordingly. This calculation is then carried out for two different measured values ​​at two different speeds, for example using the formula: γ=1 / (T2-T1)(ρ1 / ρ2-1). A temperature sensor is often integrated in the density sensor, so that the measured temperature also corresponds to the temperature at the density sensor. First, a measurement is made at a first specified rotation speed of the pump. This means that the medium reaches the density sensor at a first temperature, which is slightly higher because the density sensor or the conduit directly leading to the density sensor is in thermally conductive contact with the heat generating component. A first density is then measured for a first temperature that is higher than the temperature of the medium conveyed in the rest of the flowmeter. If, for example, the pump speed is then increased, more cold medium is circulated from the flowmeter, which medium acts as a corresponding heat sink, resulting in a decrease in temperature at the temperature sensor and a different density at the density sensor located close to the heat source, i.e. at the heat generating component, which results in a density measurement different from the first measurement. Thus, by varying the pump speed, multiple measurements can be made at different temperatures, so that the coefficient of thermal expansion can be calculated very accurately in a highly dynamic manner. This mechanism can therefore be used to actively track the fluid properties in the flowmeter.

[0011] It is also advantageous if the density sensor comprises a particularly controllable heat source, i.e. the heat source is preferably integrated into the density sensor. In this case, the heat source is controlled instead of the amount of circulated fluid. This can then be considered as equivalent to circulating volume control with a pump, which therefore rotates at a constant speed. A combination of both control methods is of course also possible. This increases the complexity, but in that case the temperature control becomes more flexible and a higher integration level can be achieved.

[0012] Preferably, the flowmeter comprises a main conduit, through which the inlet is fluidly connected to the outlet, a displacer is arranged within the main conduit, the main conduit can be bypassed by means of a bypass conduit branching off from the main conduit between the inlet and the displacer and opening into the main conduit between the displacer and the outlet, a pressure differential transducer is arranged within the bypass conduit, the displacer is driven by a drive motor controllable by an electronic unit depending on the pressure difference present at the pressure differential transducer, the drive motor or electronic unit of the displacer acts as a heat-generating electric or electronic component in heat-conducting contact with the density sensor or the conduit section leading to the density sensor immediately upstream of the density sensor. Correspondingly, the medium is heated by the electronic unit and / or the drive motor of the displacer in the conduit section leading to the density sensor immediately upstream of or at the density sensor. Such a flowmeter operates with high accuracy and can be realized within a relatively small installation space. By using electronic and / or electrical components as the heat source for tracing the fluid characteristic curve, additional components for determining the coefficient of thermal expansion are eliminated.

[0013] In a preferred further development of the system, the conduit section of the main conduit or the bypass conduit can be bypassed by means of a second bypass conduit in which the pump and the density sensor are arranged in series. Thus, the density of the medium can be determined during the measurement without feedback effect on the measurement circuit, since circulation occurs in the bypass. The medium absorbs heat from the bypassed conduit section of the main conduit or the bypassed conduit. The medium that is not heated by the electronic components, i.e. the main flow in the bypass line or main conduit, accordingly acts as a heat sink, whereby the circulated medium flow is cooled again.

[0014] Preferably, the pump is driven via a second drive motor and is controllable by a control unit, the control unit and / or the drive motor acting as a heat-generating electric or electronic component in heat-conducting contact with the density sensor or with a conduit section leading to the density sensor immediately upstream of the density sensor. The second drive motor is controlled by the control unit with at least two different speeds to allow a determination of the thermal expansion coefficient possible from two measurements. This determination of the thermal expansion coefficient becomes more accurate as the number of measurements taken at different speeds of the pump increases.

[0015] Also in this way, for the above method, the medium can be heated in a second drive motor and / or control unit of the pump in the conduit section of the bypass line upstream of the density sensor or at the density sensor. This gives the possibility for the drive motor or the control unit of the pump to act as a heat source and thus to operate along a characteristic curve. Thus, in addition to driving the displacer, the drive of the pump can also directly act as a heat source, which may be preferred from the point of view of the design of the system. Also, the medium can additionally or alternatively be heated by a heating element that is provided specifically for this purpose.

[0016] In order to eliminate the influence on the flowmeter measurements and in particular on the pressure differential transducer as a result of the bypass line, the pump is configured to be pulsation-free, in particular as a Tesla pump. This also eliminates errors in the measurements of the density sensor, which can itself be excited to oscillate due to the pulsation of the medium if it is designed as a MEMS sensor, for example, or in the case of a macroscopic sensor. The Tesla pump conveys the fluid based on the existing viscosity of the fluid, without the need to use vanes, simply using adhesion forces. For this purpose, several disks arranged next to each other, between which the medium is introduced in the middle, are rotated by a drive motor, so that the medium is conveyed tangentially in the direction of rotation and radially outward due to viscosity and adhesion due to the outward increasing speed. This results in an efficient pulsation-free conveyance.

[0017] In a more advanced embodiment, the Tesla pump is placed upstream of the density sensor in the bypass conduit in the conveying direction of the medium, thereby preventing air bubbles in the area of ​​the sensor from reaching the pump during start-up, which would not be able to be conveyed by the Tesla pump due to insufficient adhesion of the medium, and would otherwise significantly reduce the efficiency of the pump.

[0018] It is also advantageous if the second bypass conduit branches off from the first bypass conduit between the inlet and the pressure differential transducer and opens into the first bypass conduit: on the one hand, this location is very accessible, so that short connecting lines are sufficient, and on the other hand, it allows the medium to circulate directly without creating a flow in the measuring chamber, thus preventing any influence on the flowmeter measurement.

[0019] In order on the one hand to measure the temperature at the same place as the density and on the other hand to simplify the mechanics of the system, the temperature sensor is integrated into the density sensor.

[0020] In addition, the structure of the system is simplified in that the control unit for the second drive motor of the pump is integrated into the electronic unit.

[0021] Thus, a time-resolved flow-through process measurement system for a medium is provided, as well as a method for determining the thermal expansion coefficient using said system, with which the flow characteristic curve of the respective medium used can be traced directly in the flowmeter in order to determine the thermal expansion coefficient of the medium in a highly dynamic manner with high accuracy. The obtained values ​​can thus be used in the calculation of the mass and volumetric flow-throughs determined in the flowmeter, which therefore also have a higher accuracy. No additional components are required for this purpose. Instead, when tracing the characteristic curve, the components that generate heat in any case are used as heat sources and the cooler medium is used as heat sinks.

[0022] The system for time-resolved flow-through process measurement of a medium according to the invention, as well as the method for determining the thermal expansion coefficient using said system, are explained below on the basis of non-limiting example embodiments shown in the figures. [Brief description of the drawings]

[0023] [Figure 1] 1 is a schematic diagram of the basic structure of a time-resolved flow-through process measurement system for a medium according to the present invention; [Diagram 2] FIG. 1 is a perspective view of a time-resolved flow-through process measurement system for a medium with the body partially cut open. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0024] The time-resolved flow-through process measurement system of the present invention, shown in FIG. 1, comprises a flowmeter 10 having an inlet 12 and an outlet 14 and a second bypass conduit 16 by means of which a conduit section 18 of the flowmeter 10 can be bypassed.

[0025] Through the inlet 12, the medium to be measured, in particular fuel, flows from a device which generates a flow entering the main conduit 20 of the flowmeter 10. A rotary displacer 22 in the form of a double gear pump is arranged in this main conduit 20. Downstream of the displacer 22, the main conduit 20 terminates in an outlet 14. The rotary displacer 22 is driven by a drive motor 24 which is coupled to a coupling or gearbox and which is controlled by an electronic unit 25.

[0026] A first bypass conduit 26 branches off from the main conduit 20 between the inlet 12 and the rotary displacer 22 and opens again into the main conduit 20 downstream of the rotary displacer 22 between the rotary displacer 22 and the outlet 14, and is fluidly connected to the inlet 12 and the outlet 14, like the main conduit 20. A translational pressure differential transducer 28 is arranged in this bypass line 26, which transducer consists of a measuring chamber 30 and a piston 32 arranged in the measuring chamber 30 so as to be freely displaceable, the piston 32 having the same specific gravity as the measuring medium, i.e. fuel, and being cylindrical like the measuring chamber 30, so that the measuring chamber 30 has an inner diameter that substantially corresponds to the outer diameter of the piston 32. When a pressure difference between the front and rear sides of the piston 32 is applied, a displacement of the piston 32 from its rest position occurs. The displacement of the piston 32 is therefore a function of the applied pressure differential. A displacement sensor 34 is arranged in the measuring chamber 30, which is operatively connected to the piston 32 and in which a voltage is generated that is dependent on the magnitude of the displacement of the piston 32. This displacement sensor 34 is attached to the measuring chamber 30 and is in particular a magnetoresistive sensor that converts the field strength of a magnet 36 acting on it into a voltage. For this purpose, the magnet 36 is attached to the center of gravity of the piston 32. However, an optical sensor may also be used as the displacement sensor 34.

[0027] The displacement sensor 34 is also connected to the electronic unit 25, which is accordingly used to evaluate the measured value of the displacement sensor 34 and convert it into a control signal for the drive motor 24, which is controlled in such a way that the piston 32 is always in a defined starting position. The rotary displacer 22 thus always approximately compensates in conveyance the pressure difference occurring at the piston 32 due to the injected medium. This means that if the piston 32 is displaced to the right, the pump speed is increased as a function of the magnitude of this displacement and vice versa. For this purpose, the displacement of the piston 32 or the volume displaced thereby in the measuring chamber 30 is converted by a transfer function into the required pumping volume of the rotary displacer 22 or into the speed of the drive motor 24, and the drive motor 24 is supplied with a current accordingly. However, the electronic unit 25 also includes heat-generating power semiconductors for driving the drive motor 24.

[0028] A pressure measuring element 40 is arranged in the measuring chamber 30 and a temperature measuring element 42 is arranged immediately behind the rotary displacer 22, which continuously measure the pressure and temperature occurring in this area and then supply them to the electronic unit 25 so that changes in density in the measuring chamber 30 can be taken into account in the calculations.

[0029] A series of measurements are performed such that when calculating the total flow rate determined by the electronic unit 25, both the flow rate in the bypass line 26 resulting from the movement or position of the piston 32 and the volume displaced in the measuring chamber 30 and the actual flow rate of the rotary displacer 22 within a fixed time interval are taken into account, and both flow rates are added together to determine the total flow rate.

[0030] The flow rate in the piston 32 is determined, for example, by differentiating the displacement of the piston 32 in an electronic unit 25 connected to a displacement sensor 34 and then multiplying it by the base area of ​​the piston 32 to obtain the volumetric flow through the bypass line 26 during the time interval.

[0031] The flow rate through the rotating displacer 22, and therefore the main conduit 20, can be determined from determined control data for controlling the displacer 22, or can be calculated using the rotational speed as measured directly at the displacer 22 or drive motor 24, for example by an optical encoder or magnetoresistive sensor.

[0032] In this embodiment, the second bypass conduit 16 branches off from the bypass conduit 26 between the inlet 12 and the measurement chamber 30, bypassing the conduit section 18 and re-entering the bypass conduit 26 upstream of the measurement chamber 30. This second bypass conduit 16 could branch off and re-enter at any other location in the main conduit 20 or the bypass conduit 26, but the second bypass conduit 16 should not bypass either the displacer 22 or the differential pressure transducer 28.

[0033] Between the branch 44 and the opening 46 into the bypass conduit 26, a pulsation-free pump 48 in the form of a Tesla pump and a density sensor 50 are arranged in series, one after the other, in the bypass conduit 16. Usually, a temperature sensor 51 is also included in the density sensor 50 so that the temperature at which the density is measured is precisely known. This density sensor 50 may be defined, for example, as a MEMS sensor measuring according to the Coriolis principle. The Tesla pump 48 is driven by a second drive motor 52, which is controlled by a control unit 54, which in this embodiment is integrated in the electronic unit 25. Thus, the second drive motor 52 and the density sensor 50 with the temperature sensor 51 are electrically connected to the electronic unit 25, so that the measured values ​​of the density sensor 50 can be used to improve the calculated flow values ​​with additional information on the density of the medium and to control the Tesla pump 48, thereby ensuring a flow through the density sensor 50, the measured values ​​of which would otherwise deviate from the actual values ​​measured in the measuring chamber due to flow stagnation. The non-pulsating delivery of the Tesla pump 48 also prevents erroneous readings from the sensor 50.

[0034] This is because the sensor 50 always oscillates at a precisely defined frequency, which depends on the design of the sensor. MEMS sensors have a much higher oscillation frequency than conventional sensors due to their compact design. For typical density sensors, the oscillation frequency is between 100Hz and 1kHz, and for MEMS sensors it is usually 1kHz or higher. Thus, if the Tesla pump 48 were to generate pulsations close to the oscillation frequency of the sensor 50, the sensor 50 would be disturbed, and pump pulsations should be avoided. Thus, the conduit section 18 of the bypass conduit 26 is bypassed by means of the second bypass conduit 16 when pumped by the Tesla pump 48, creating a circuit flow across the conduit section 18 from the opening 46 of the bypass conduit 16 to the bypass conduit 26 to the branch 44, in particular because ideally the rotary displacer 22 completely compensates the pressure differential across the piston 32, and therefore ideally no flow occurs in the bypass conduit 26.

[0035] The flow cross section of the bypass conduit 26 of the flowmeter 10 is significantly larger than that of the second bypass conduit 16, which has a diameter of, for example, about 4 mm, so that a relatively small flow is required to create the required pressure difference. The absence of pulsation of the pump 48 and such a smaller flow amount ensures that there are virtually no feedback effects on the control circuits of the displacer 22 and the pressure differential transducer 28 due to unwanted flows or pulsations. Thus, accurate additional information is provided to the electronic unit 25, which can be used both in controlling the displacer 22 and in calculating the through flow, thereby further improving the results.

[0036] In order to be able to use the measured values ​​of the density sensor 50, it is necessary that this sensor 50 measures the density of the medium at exactly the same temperature at which the flowmeter 10 operates, i.e. the temperature present in the measuring chamber 30 or the displacer 22. However, this is usually not the case, since the temperature and therefore the density at different locations in the system, usually through ambient heat, can be different, which causes measurement deviations. This is further increased with the demand for smaller measuring devices, since the influence of heat-generating components, such as from the electronic unit 25, on the sensors 50, 51 increases. This is especially true at small flow rates, since in that case only small amounts of conditioned new medium are transported into the sensor 50. As a result, even the smallest heat source is sufficient to cause significant heating of the medium. It is possible to condition the entire sensor with a separate conditioning path, thereby reducing this effect. However, this represents a significant limitation of the sensor 50, especially in mobile applications, since there is no conditioning circuit that can be connected to the sensor.

[0037] In order to still be able to use the measured values, a conversion of the determined volumetric flow-through is required, whereby the temperature difference and thus the resulting volume difference are compensated for. However, for such a conversion, the thermal expansion coefficient of the respective medium used must be known. This is also necessary whenever a measurement volume for a certain reference temperature must be determined. In the past, samples were sent to a laboratory to determine the thermal expansion coefficient, but this is no longer sufficient today, since the composition of the fuel to be measured changes frequently and therefore there is a demand for a highly dynamic determination of the expansion coefficient.

[0038] In accordance with the present invention, to determine the coefficient of thermal expansion, the density sensor 50, or the conduit section 56 of the second bypass conduit 16 which leads directly to the density sensor 50, is coupled to or positioned in close proximity to heat generating components of the existing system such that heat transfer occurs, with each heat generating component acting as a heat source.

[0039] In this embodiment, it can be seen in FIG. 2 that the density sensor 50 and the conduit section 56 of the second bypass conduit 16 leading to the density sensor 50 are arranged close to the drive motor 24 of the displacer 22 and the electronic unit 25, so that heat transfer to the medium occurs and the electronic unit 25 and the drive motor 24 act as a heat source. As a result, the medium reaching the density sensor 50 has a slightly higher temperature than the medium in the bypass conduit 26 and the main conduit 20 and the measuring chamber 30. This difference is now used to operate along the temperature characteristic curve of the medium by driving the Tesla pump 48 at at least two, but usually several, different speeds. These different speeds result in different temperatures at the density sensor 50 and also at the temperature sensor 51, because as the flow rate increases, the influence of the cooler medium injected from the bypass line 26 acting as a heat sink increases and the influence of the heat source formed in the electronic unit 25 decreases, since this heat source acts on the medium for a shorter time. In this way, different densities at different temperatures can be measured by the density sensor 50 and thus by the temperature sensor 51, from which the coefficient of thermal expansion can then already be calculated for two different temperatures using the formula: γ=1 / (T2-T1)(ρ1 / ρ2-1). The accuracy of the determined coefficient of thermal expansion is improved, especially in the case of non-linear media with a non-constant coefficient of thermal expansion, by making it possible to trace the entire characteristic curve and to determine the coefficient of thermal expansion using a larger temperature spectrum. For example, in solutions containing water, the coefficient of expansion varies significantly with temperature, so that the maximum possible number of measurements must be made for such solutions. Also, the respective determined pairs of density and temperature values ​​can be weighted, which can for example reduce the influence of older measurements, so that after a certain period of time, older value pairs are not taken into account when determining the coefficient of thermal expansion.

[0040] Furthermore, by tracing the characteristic curve, it is possible to determine the composition of the fuel used, if the characteristic curve of the corresponding known fuel is stored. It is also possible to fully evaluate the characteristic curve with its slope change or reversal point, as is the case for water, for example.

[0041] In summary, a method for determining the coefficient of thermal expansion and a time-resolved flow-through process measurement system for a medium suitable for the method are provided, by means of which the coefficient of thermal expansion can be determined in a highly dynamic manner within existing equipment and used in the calculation of the injected fuel quantity to further improve the accuracy of the results. By using this method, it is possible to eliminate the need to measure the density at exactly the temperature at which the volume is measured, since the coefficient of expansion is available for conversion. This is especially necessary due to the steady miniaturization of measuring equipment. Convertible to a reference temperature.

[0042] The flowmeter thus continuously calculates the flow process with a high degree of time resolution with high precision and, in particular with regard to the thermal expansion coefficient of the medium, provides additional data for controlling the system or for evaluating the measurement results in comparison with known configurations.

[0043] It will be clear that the invention is not limited to the described embodiment, but various modifications are possible within the scope of protection of the main claims. In principle, other continuously operating flowmeters can be used, or bypass conduits can bypass the corresponding conduit section at another location of the flowmeter. Also, other components such as the drive motor or the control unit of the Tesla pump are used as heat sources. In other flowmeters, other heat-generating components are used for the purpose of tracking the characteristic curve.

Claims

1. An entrance (12); An exit (14); and a pump (48), a density sensor (50), a temperature sensor (51), and electrical or electronic components disposed between the inlet (12) and the outlet (14); A flow meter (10); A time-resolved flow-through process measurement system for a medium, comprising: the density sensor (50) or a conduit section (56) immediately upstream of the density sensor (50) leading to the density sensor (50) is in thermally conductive contact with the heat generating electrical or electronic components, and the pump (48) is speed controlled. A system characterized by:

2. the flow meter (10) comprises a main conduit (20), the inlet (12) is fluidly connected to the outlet (14) via the main conduit (20), a displacer (22) is disposed within the main conduit (20), the main conduit (20) is bypassable using a bypass conduit (26), the bypass conduit (26) branches off from the main conduit (20) between the inlet (12) and the displacer (22) and opens into the main conduit (20) between the displacer (22) and the outlet (14); a pressure differential transducer (28) disposed within said bypass conduit (26); The displacer (22) is drivable by a drive motor (24) controllable by an electronic unit (25) depending on the pressure difference present across the pressure differential transducer (28); the drive motor (24) of the displacer (22) or the electronic unit (25) acts as a heat-generating electrical or electronic component in thermally conductive contact with the density sensor (50) or with the conduit (56) immediately upstream of and leading to the density sensor (50); 2. A system for measuring a time-resolved flow-through process of a medium according to claim 1.

3. the conduit section (18) of the main conduit (20) or the bypass conduit (26) can be bypassed using a second bypass conduit (16) in which the pump (48) and the density sensor (50) are arranged in series; 3. A system for time-resolved flow-through process measurement of a medium according to claim 2.

4. the pump (48) being driven via a second drive motor (52) and controllable by a control unit (54), the control unit (54) and / or the second drive motor (52) acting as a heat generating electrical or electronic component in thermally conductive contact with the density sensor (50) or the conduit (56) immediately upstream of and leading to the density sensor (50); 4. A system for measuring a time-resolved flow-through process of a medium according to claim 2 or 3.

5. The pump (48) is a non-pulsating pump.

5. A system for time-resolved flow-through process measurement of a medium according to claim 4.

6. The non-pulsating pump (48) is a Tesla pump.

6. A system for measuring a time-resolved flow-through process of a medium according to claim 5.

7. The Tesla pump (48) is arranged upstream of the density sensor (50) in the conveying direction.

7. A system for time-resolved flow-through process measurement of a medium according to claim 6.

8. the second bypass conduit (16) branches off from the bypass conduit (26) between the inlet (12) and the pressure differential transducer (28) and opens into the bypass conduit (26); 4. A system for measuring a time-resolved flow-through process of a medium according to claim 3.

9. The temperature sensor (51) is integrated into the density sensor (50).

9. A system for measuring a time-resolved flow-through process of a medium according to any one of claims 1 to 8.

10. the control unit (54) of the second drive motor (52) of the pump (48) is integrated into the electronic unit (25); 5. A system for time-resolved flow-through process measurement of a medium according to claim 4.

11. 11. A method for determining the thermal expansion coefficient of a medium according to any one of claims 1 to 10, comprising the steps of: the density and temperature of a medium heated by a heat-generating electrical or electronic component are measured by a density sensor (50) and a temperature sensor (51) at two different rotational speeds of the pump (48), and the thermal expansion coefficient is calculated from the measurements of the density sensor (50) and the corresponding measurements of the temperature sensor (51), A method comprising:

12. 12. A method for determining the coefficient of thermal expansion according to claim 11, using a time-resolved flow-through process measurement system for a medium according to claim 2, comprising the steps of: the medium is heated in an electronic unit (25) of a pump (48) and / or in a second drive motor (52) in a conduit (56) leading to the density sensor (50) immediately upstream or at the density sensor (50); A method comprising:

13. 12. A method for determining the coefficient of thermal expansion according to claim 11, using a time-resolved flow-through process measurement system for a medium according to claim 3, comprising the steps of: the medium from the bypassable conduit section (18) of the main conduit (20) or the bypass conduit (26) absorbs heat from the medium flow in the second bypass conduit (16); A method comprising:

14. 12. A method for determining a coefficient of thermal expansion according to claim 11, comprising a time-resolved flow-through process measurement system for a medium according to claim 4, comprising: the pump (48) is driven by a second drive motor (52) which is controlled by a control unit (54) with at least two different speeds at which the temperature and density measurements are performed by the density sensor (50) and the temperature sensor (51); A method comprising:

15. 15. A method for determining the coefficient of thermal expansion according to claim 14, using a time-resolved flow-through process measurement system for a medium according to claim 4, comprising the steps of: the medium is heated in a second drive motor (52) of the pump and / or in the control unit (54) of the second drive motor (52) in a conduit section (56) of a second bypass conduit (16) upstream of or at the density sensor (50); A method comprising:

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