JP4042863B2 - Multi-vortex flowmeter using mass flow rate as switching point - Google Patents

Description

  The present invention includes a vortex flowmeter that measures volumetric flow and a thermal flowmeter that measures mass flow, and uses these two flowmeters according to the flow rate of the fluid to be measured flowing through the flow path. Regarding the meter, in detail, it relates to the switching point of the two flow meters.

  In order to measure the flow rate of the fluid to be measured flowing in the flow tube, a vortex flow meter or a thermal flow meter is used.

  As is well known, when a vortex generator is arranged in a fluid flow, the vortex flowmeter is the number of Karman vortices (vortex frequency) generated from the vortex generator within a unit time within a predetermined Reynolds number range. Is proportional to the flow rate regardless of gas or liquid. This proportionality constant is called the Strouhal number. Examples of the vortex detector include a thermal sensor, a strain sensor, an optical sensor, a pressure sensor, an ultrasonic sensor, and the like, which can detect a thermal change, a lift change, and the like due to the vortex. The vortex flowmeter is a simple flowmeter that can measure the flow rate without being affected by the physical properties of the fluid to be measured, and is widely used for measuring the flow rate of gas or fluid (see, for example, Patent Document 1).

  The thermal flow meter includes a temperature sensor (fluid temperature sensor) and a heating temperature sensor (heating temperature sensor), and is a heating temperature sensor (flow velocity) having the functions of a temperature sensor and a heating sensor. The temperature of the sensor (heater) is controlled to be a constant temperature difference with respect to the temperature measured by the temperature sensor. This is because the amount of heat taken away from the heater when the fluid to be measured flows is correlated with the mass flow rate, and the mass flow rate is calculated from the amount of heating power to the heater (see, for example, Patent Document 2). ).

  Patent Document 3 listed below discloses a technique for a multi-vortex flow meter that has both the function of a vortex flow meter and the function of a thermal flow meter. The multi-vortex flow meter can accurately measure from a minute flow rate to a large flow rate, and this point is particularly superior to other flow meters.

  In the multi-vortex flow meter, the function of the vortex flow meter and the function of the thermal flow meter are selectively used according to the flow state of the fluid to be measured flowing through the flow path of the flow tube. That is, measurement is performed by the function of the thermal flow meter in the minute flow rate region and the low flow rate region, and measurement is performed by the function of the vortex flow meter in the high flow rate region.

In vortex flowmeters, the sensitivity of the vortex detector becomes insufficient when the flow rate decreases and the vortex differential pressure decreases, so the multi-vortex flowmeter switches the function to the thermal flowmeter at a predetermined lower limit flow rate. Control is being made.
Japanese Patent No. 2869054 (Page 3, Fig. 1) JP 2004-12220 A (Page 6, FIG. 4) JP 2006-29966 A (page 4-8, FIG. 1-5)

  The inventor of the present application has found that, even if the flow rate is low, the vortex differential pressure increases as the pressure in the flow tube increases, and this makes it possible to lower the lower limit flow rate that is a criterion for switching the function of the flow meter. I would like to reflect this finding in the multi-vortex flowmeter. The inventor of the present application wants to measure the flow rate using the function of the vortex flowmeter as much as possible in order to take advantage of the vortex flowmeter.

  This invention is made | formed in view of the situation mentioned above, and makes it a subject to provide a better multi vortex flowmeter using a mass flow rate as a switching point.

  The multi-vortex flow meter using the mass flow rate of the present invention as a switching point according to the present invention, which has been made to solve the above problems, comprises a vortex flow meter that measures a volume flow rate and a thermal flow meter that measures a mass flow rate. A multi-vortex flow meter having a configuration in which these two flow meters are selectively used according to the flow rate of the fluid to be measured flowing through the flow path, wherein the switching point of the two flow meters is based on the mass flow rate, and the vortex flow meter The switching point mass flow rate Qm in a range larger than the minimum flow rate of the thermal flow meter and smaller than the maximum flow rate of the thermal flow meter is determined by Qm = K3 * √P (where P: pressure of the flow path (variable), K3: flow path) Area, eddy differential pressure, constant related to vortex differential pressure, constant at 1 ° C. at 0 ° C., and constant at 1 atm).

  The multi-vortex flowmeter using the mass flow rate of the present invention as a switching point according to the present invention, which has been made to solve the above-mentioned problems, comprises a vortex flow meter that measures the volume flow rate and a thermal flow meter that measures the mass flow rate. A multi-vortex flow meter having a configuration in which these two flow meters are selectively used according to the flow rate of the fluid to be measured flowing through the flow path, wherein the switching point of the two flow meters is based on the mass flow rate, and the vortex flow meter The switching point mass flow rate Qm in a range larger than the minimum flow rate of the thermal flow meter and smaller than the maximum flow rate of the thermal flow meter is determined by Qm = K4 * √ (P / T) (where P: pressure of the flow path (variable), T: Absolute temperature (variable) of the fluid to be measured, K4: Corresponding to the area of the flow path, vortex differential pressure, constant related to the vortex differential pressure, density of 1 atm at 0 ° C., pressure at 1 atm, and 0 ° C. Absolute temperature (273.15 ), Constant determined by) is characterized by.

  According to the present invention having such a feature, the function of the vortex flow meter is changed to the function of the thermal flow meter after the pressure is added, or the pressure and the temperature are added, or the thermal flow meter. From this function, the function of the vortex flowmeter is switched. The present invention pays attention to the fact that the higher the pressure, the higher the eddy differential pressure, and as a result, the sensitivity of the vortex flowmeter increases and it is possible to measure to a lower flow rate. By determining the switching point as in the present invention, the flow meter can be switched at an optimal (lowest possible) flow rate (flow velocity) even when the pressure and temperature fluctuate.

  According to the present invention, it is possible to provide a highly accurate multi-vortex flow meter that takes advantage of the vortex flow meter. Therefore, it is possible to provide a better multi-vortex flowmeter than before.

  Hereinafter, description will be given with reference to the drawings. FIG. 1 is a front view showing an embodiment of a multi-vortex flowmeter using the mass flow rate of the present invention as a switching point. 2 is a cross-sectional view taken along line AA in FIG. 1, and FIG. 3 is a cross-sectional view of the flow rate converter. Further, FIG. 4 is a diagram related to the description of the switching point, and FIG.

  1 and 2, reference numeral 1 indicates a multi-vortex flowmeter of the present invention. The multi-vortex flow meter 1 is configured to have both the function of a vortex flow meter and the function of a thermal flow meter. As will be described later, the multi-vortex flow meter 1 is configured to determine a switching point between two flow meters and switch the function of the flow meter based on the determined switching point. The multi-vortex flow meter 1 includes a vortex detection means 7 having a measurement mounting pipe 2, a pressure gauge 3, a measurement pipe 4, a vortex generator 5, and a vortex detector 6, a temperature sensor 8 and a heating temperature sensor 9. And a flow rate converter 11 for calculating a flow rate or a flow rate of a fluid to be measured (not shown) based on output signals from the vortex type detection unit 7 and the thermal type detection unit 10. Has been. In the following, each configuration will be described first with reference to FIGS. 1 to 3, and then switching points of the two flow meters will be described.

  The measurement attachment pipe 2 is detachably attached to the middle of the flow pipe 12 (not limited to the middle of the flow pipe 12 but may be attached to the end), and the flow path 13 is formed in the inside thereof. It is formed as such a cylindrical structure. Joints are formed at both ends of the measurement mounting pipe 2. The flow rate converter 11 is fixed to the outside of the measurement mounting pipe 2 by appropriate means. The flow path 13 formed in the measurement mounting pipe 2 has a circular cross section. A fluid to be measured flows in the flow path 13 in the direction of the arrow.

  A measuring tube 4, a temperature sensor 8, and a heating temperature sensor 9 are provided in the middle of the flow path 13. In addition, a pressure measurement unit 14 is formed on the upstream side of the measurement tube 4 and the like and in the vicinity of the measurement tube 4 (the arrangement is an example). The pressure measuring unit 14 is attached in such a state that the pressure gauge 3 is accommodated. The pressure measurement unit 14 has a part for housing the pressure gauge 3 and a part for introducing a part of the fluid to be measured flowing through the flow path 13. The pressure gauge 3 is for measuring the pressure of the fluid to be measured flowing through the flow path 13, and here, a known pressure gauge is used (however, the pressure gauge 3 can be used for the flow rate converter 11). . The pressure gauge 3 is attached to the flow rate converter 11 so as to be integrated. The pressure gauge 3 is integrated with the flow rate converter 11 at a position slightly upstream from the vortex detector 6, the temperature sensor 8, and the heating temperature sensor 9.

  The measuring tube 4 is formed in a cylindrical shape having a rectangular tube cross section (the shape is an example). The measuring tube 4 is formed so as to extend along the arrow direction in which the fluid to be measured flows. A vortex generator 5 and a pressure receiving plate 15 (described later) located on the downstream side of the vortex generator 5 are provided at a portion of the measurement tube 4 where the fluid to be measured flows. Outside the measuring tube 4, a temperature sensor holding unit 16 is provided to hold the tips of the temperature sensor 8 and the heating temperature sensor 9 (in this embodiment, it is integrated, but not limited to this). The measurement tube 4 is fixed to the vortex detector 6 via the connecting cylinder portion 17. In this embodiment, the vortex detector 6 connected to the measurement tube 4 is attached to the measurement attachment pipe 2 so as to be detachable.

  The vortex generator 5 is a part for generating a vortex inside the measurement tube 4 and is configured to face the flow of the fluid to be measured. In this embodiment, the vortex generator 5 is formed in a triangular prism shape (the shape is an example. Japanese Patent No. 2869054 of Patent Document 1 discloses several examples). The vortex generator 5 is provided in the opening portion of the measuring tube 4 on the side into which the fluid to be measured flows. The vortex generator 5 is provided so as to be located at the center of the opening of the measurement tube 4.

  Here, the vortex generated by the vortex generator 5 will be described. The vortex is separated from the position where the change in momentum generated by the flow of the fluid to be measured flowing into the opening portion of the measuring tube 4 along the vortex generator 5 is large, and the cross section of the vortex generator 5 is like this embodiment. In the case of a triangular shape, the triangular edge portion becomes the peeling point. The vortices that peel off and flow out of the vortex generator 5 are alternately generated in a staggered manner according to Karman's stable vortex condition, and flow out while forming a vortex array that maintains a constant vortex distance and vortex string distance. The distance between the vortices is the unit time calculated based on the number of vortices generated per unit time, that is, the vortex frequency and the flow rate obtained from the fluid flowing into the reference container such as the reference tank within a predetermined time. It can be obtained from the hit flow rate.

  The temperature sensor holding part 16 is formed so as to protrude from the lower wall of the measurement tube 4 in the horizontal direction, in other words, from both side walls of the measurement tube 4. The temperature sensor holding part 16 is not particularly limited, but is formed so that the shape in plan view is a triangle. The temperature sensor holding part 16 is formed in a shape in which the measuring tube 4 has a fin. The tip of each of the temperature sensor 8 and the heating temperature sensor 9 is inserted straight into the temperature sensor holding unit 16.

  The vortex detector 6 is a sensor for detecting vortices, and a pressure receiving sensor is used here. The vortex detector 6 includes a pressure receiving plate (sensor pressure receiving plate) 15 disposed on the downstream side of the vortex generator 5 in the measurement tube 4 and a pressure detection element plate provided inside the vortex detector 6. The fluctuating pressure (alternating pressure) based on the Karman vortex generated by the vortex generator 5 is detected by the pressure detecting element plate via the pressure receiving plate 15. In this embodiment, the vortex detector 6 is attached so as to be integrated with the flow rate converter 11.

  The vortex detection means 7 is provided for obtaining the flow velocity or flow rate of the fluid to be measured flowing in the measurement mounting pipe 2. The flow rate or flow rate of the fluid to be measured flowing in the measurement mounting pipe 2 is obtained by calculating the flow rate or flow rate of the fluid to be measured flowing in the measurement pipe 4 as the partial flow rate or partial flow rate of the measurement mounting pipe 2. It is supposed to be. This is based on the fact that the entire flow rate can be estimated if the flow is uniform even if a part of the pipe section of the measurement mounting pipe 2 is measured instead of the whole pipe cross section. That is, since the flow velocity distribution of the rectified fluid flowing through the straight pipe is given as a function of the Reynolds number, the flow velocity at a certain distance from the center of the measurement mounting pipe 2 is averaged in the measurement mounting pipe 2. It can be converted into a flow rate.

  As the temperature sensor 8 and the heating temperature sensor 9 constituting the thermal detection means 10, known ones are used. Here, the description of the specific configuration is omitted. The temperature sensor 8 of this embodiment is a rod-shaped temperature sensor, and the rod-shaped heating temperature sensor 9 is also a flow rate sensor (heater) having functions of a temperature sensor and a heating sensor. In this embodiment, the temperature sensor 8 and the heating temperature sensor 9 are attached to the flow rate converter 11 so as to be integrated.

  The temperature sensor 8 and the heating temperature sensor 9 protrude into the flow path 13 of the measurement mounting pipe 2, and the most advanced part is held by the temperature sensor holding part 16. Each temperature sensing part of the temperature sensor 8 and the heating temperature sensor 9 is arranged in the vicinity of the measuring tube 4. The temperature sensor 8 and the heating temperature sensor 9 are arranged side by side with the vortex detector 6 (the arrangement is an example. If the arrangement is made so as not to affect the vortex detection, the temperature sensor 8 and the heating temperature sensor 9 may be different. But shall be fine). It should be noted that each temperature sensing part of the temperature sensor 8 and the heating temperature sensor 9 may be elongated so as to protrude further from the temperature sensor holding part 16 to the center of the flow path 13 (measured from the outside). To avoid the effect of heat transmitted to the mounting pipe 2).

  The flow rate converter 11 has a converter case 18. Inside the converter case 18, an amplifier board 19 having a configuration such as a microcomputer is provided. The amplifier board 19 is connected to the transmission line 20 of the pressure gauge 3, the leads of the temperature sensor 8 and the heating temperature sensor 9, and the transmission line 21 of the vortex detector 6 (sensation in FIG. 3). The arrangement of the temperature sensor 8 and the heating temperature sensor 9 is changed for convenience, and is actually arranged at a position rotated by 90 °, and aligned with the transmission line 21 of the vortex detector 6 in the direction perpendicular to the paper surface of FIG. Arranged).

  The temperature sensor 8, the heating temperature sensor 9, and the transmission lines 20 and 21 are drawn into the converter case 18. The temperature sensor 8, the heating temperature sensor 9, and the transmission lines 20 and 21 are drawn into the converter case 18 without being exposed to the outside. The temperature sensor 8, the heating temperature sensor 9, the pressure gauge 3, the vortex detector 6, and the amplifier board 19 have functions as a flow rate measurement unit and a flow rate calculation unit.

  A converter cover 24 having a switch board 22 and a display board 23 is attached to the opening of the converter case 18 with a packing (not shown) interposed therebetween. A transmission cable 25 is connected to one side wall of the converter case 18.

  In the above-described configuration and structure, the multi-vortex flow meter 1 of the present invention is a vortex flow meter according to the state of the flow of the fluid to be measured flowing through the flow path 13 of the measurement mounting pipe 2, that is, based on the switching point described later. The function of the thermal flow meter can be used properly. Specifically, measurement is performed by the function of the thermal flow meter in the minute flow range and low flow region, and measurement is performed by the function of the vortex flow meter in the high flow region (as much as possible of the vortex flow meter). Measurement is made by function).

  The multi-vortex flow meter 1 of the present invention is designed to wrap to some extent the high flow rate measurement in the function of the thermal flow meter and the low flow rate measurement in the function of the vortex flow meter. A point is determined, and switching is performed by the flow rate converter 11 based on the determined switching point (the switching point will be described later).

  First, an operation when measuring a minute flow rate region or a low flow rate region, that is, an operation when measuring by the function of a thermal flow meter will be described. The heating temperature sensor 9 measures the flow rate based on the temperature detected by the temperature sensor 8. That is, in the flow rate measurement unit and the flow rate calculation unit in the flow rate converter 11, the heating temperature sensor 9 is heated so that the temperature difference between the temperature sensor 8 and the heating temperature sensor 9 is constant (for example, + 30 ° C.). (Make the current flow) and calculate the mass flow rate from the current value related to this heating. The calculated mass flow rate is converted into a predetermined unit, and then displayed on a display unit provided on the upper portion of the converter cover 24 or transmitted by the transmission cable 25 and displayed on a display device (not shown).

  As a supplementary explanation of the calculation of the mass flow rate, the heating temperature sensor 9 is cooled by the fluid to be measured when the fluid to be measured (not shown) is flowed in the direction of the arrow. In order to control the temperature difference with the temperature sensor 8 to be constant, it is necessary to further pass a current through the heating temperature sensor 9. At this time, it is known that the current flowing through the heating temperature sensor 9 is proportional to the mass flow rate, and the mass flow rate is calculated using this.

  Next, the operation in the case of performing measurement by the function of the vortex flow meter will be described. Fluctuating pressure (alternating pressure) based on Karman vortices generated by the vortex generator 5 is detected by the pressure receiving plate 15 and the pressure detecting element plate. Then, the flow velocity or flow rate of the fluid to be measured flowing in the measurement pipe 4 from the detection value in the vortex detector 6 is calculated as the partial flow velocity or partial flow rate of the measurement attachment pipe 2, and the measurement target flowing in the measurement attachment pipe 2 is obtained. Calculate the flow rate or flow rate (volume flow rate) of the fluid. The calculated flow velocity or flow rate is converted into a predetermined unit, and then displayed on a display unit provided on the upper portion of the converter cover 24 or transmitted by the transmission cable 25 and displayed on a display device (not shown).

  Regarding the switching related to the function of the flow meter performed in the flow rate converter 11, the measured value from the pressure gauge 3 is taken into the flow rate converter 11, and the switching point is determined in consideration of the taken measured value. Therefore, switching from the function of the thermal flow meter to the function of the vortex flow meter or from the function of the vortex flow meter to the function of the thermal flow meter is performed.

  The switching point will be described.

The vortex differential pressure ΔP has the following relationship.
ΔP = K * ρ * V ²
If this equation is transformed,
V ² = ΔP / (K * ρ) (1)
It becomes.

V: flow velocity ΔP: vortex differential pressure ρ: density K: constant

<Calculation of switching points 1>
Switch by mass flow (when only pressure is a variable).

The mass flow rate Qm is
Qm = π * R ² * V * ρ (2)
There is a relationship.

Qm: mass flow rate R: radius of the flow path 13

ρ = ρ0 * P / P0 (3)

ρ0: density of 1 atm at 0 ° C. P: absolute pressure [Mpaabs]
P0: 1 atm pressure ≈ 0.10133 [Mpaabs]

Substituting equation (2) into equation (1),
{Qm / (π * R ² * ρ)} ² = ΔP / (K * ρ)
It becomes.
If you arrange the left side to be Qm,
Qm = π * R ² * ρ * √ {ΔP / (K * ρ)}
It becomes.
Rewriting this formula,
Qm = π * R ² * √ (ΔP * ρ / K) (4)
It becomes.

Substituting (3) into (4),
Qm = π * R ² * √ (ΔP * ρ0 * P / P0 / K)
It becomes.
Further organizing
Qm = π * R ² * √ (ΔP * ρ0 / P0 / K) * √P (5)
It becomes.

Here, if K3 = π * R ² * √ (ΔP * ρ0 / P0 / K),
Equation (5) is
Qm = K3 * √P (6)
This function becomes the switching point (switching point mass flow rate Qm).

<Calculation of switching points 2>
Switch by mass flow (when pressure and temperature are variables).

The mass flow rate Qm is
Qm = π * R ² * √ (ΔP * ρ / K) (4)
There is a relationship.

The density ρ is
ρ = ρ0 * P / P0 * T0 / T (7)
There is a relationship.

T: Absolute temperature [K]
T0: absolute temperature corresponding to 0 ° C.≈273.15 [K]

Substituting equation (7) into equation (4),
Qm = π * R ² * √ (ΔP * ρ0 * P / P0 * T0 / T / K)
It becomes.
Further organizing
Qm = π * R ² * √ (ΔP * ρ0 / P0 * T0 / K) * √ (P / T) (8)
It becomes.

Here, if K4 = π * R ² * √ (ΔP * ρ0 / P0 * T0 / K),
Equation (8) is
Qm = K4 * √ (P / T) (9)
This function becomes the switching point (switching point mass flow rate Qm).

  In FIG. 4, the vertical axis represents mass flow rate [NL / min] (for convenience, the unit of normal flow rate (temperature and pressure reference values are set to 0 ° C. and 1 atm, respectively), and the horizontal axis represents pressure [Mpaabs]. The graph shows the switching point (thick solid line: upward curve), the minimum flow rate of the vortex flowmeter (dashed line: upward curve), the maximum flow rate of the thermal flowmeter (dashed line: straight line parallel to the horizontal axis) Each line is plotted. The switching point (bold solid line) shown in FIG. 4 is larger than the minimum flow rate (dashed line) of the vortex flow meter and smaller than the maximum flow rate (dashed line) of the thermal flow meter. According to the calculation of the switching point, the switching point (thick solid line) is determined to follow the minimum flow rate (dashed line) of the vortex flowmeter. Therefore, as can be seen from the graph by such a switching point (thick solid line), in the present invention, the flow rate can be measured using the function of the vortex flowmeter as much as possible.

  For comparison, the description will be made with reference to FIG. 5. In the graph of FIG. 5, the switching point (thick solid line) is fixed. Since the switching point (thick solid line) needs to be larger than the minimum flow rate (dashed line) of the vortex flowmeter and smaller than the maximum flow rate (dashed line) of the thermal flow meter, the switching point (thick solid line) is fixed. In this case, it is determined straightly so as to follow the maximum flow rate (broken line) of the thermal flow meter. Therefore, it is necessary to measure with a thermal flow meter even where it can be measured with a vortex flow meter. In general, thermal flow meters are known to be inferior to vortex flow meters in terms of accuracy, so fixing the switching point (thick solid line) has a significant impact on accuracy. Will end up. In the present invention, this point is solved.

  As described above with reference to FIGS. 1 to 5, according to the present invention, it is possible to provide a highly accurate multi-vortex flow meter 1 that takes advantage of the vortex flow meter. In other words, a better multi-vortex flow meter 1 can be provided than before.

  The higher the pressure, the higher the eddy differential pressure, resulting in higher sensitivity of the vortex flowmeter. Therefore, if the pressure is taken into account or the pressure and the temperature are taken into account, it becomes possible to measure to a low flow rate. At this time, the switching point of the present invention is useful. By determining the switching point as in the present invention, the flow meter can be switched at the optimum (lowest possible) flow rate (flow velocity) even if the pressure and temperature fluctuate.

  In addition, it goes without saying that the present invention can be variously modified without departing from the spirit of the present invention.

It is a front view which shows one Embodiment of the multi vortex flowmeter which uses the mass flow rate of this invention for a switching point. It is the sectional view on the AA line of FIG. It is sectional drawing of a flow rate converter. It is a figure which concerns on description of a switching point. It is a figure which concerns on the comparison description of a switching point.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Multi vortex flowmeter 2 Measurement installation piping 3 Pressure gauge 4 Measurement tube 5 Vortex generator 6 Vortex detector 7 Vortex detection means 8 Temperature sensor 9 Heating temperature sensor 10 Thermal detection means 11 Flow rate converter 12 Flow pipe DESCRIPTION OF SYMBOLS 13 Flow path 14 Pressure measuring part 15 Pressure receiving plate 16 Temperature sensor holding | maintenance part 17 Connection cylinder part 18 Converter case 19 Amplifier board 20, 21 Transmission line 22 Switch board 23 Display board 24 Converter cover 25 Transmission cable

Claims (2)

In a multi-vortex flowmeter with a configuration that uses a vortex flowmeter that measures volumetric flow and a thermal flowmeter that measures mass flow, and uses these two flowmeters according to the flow rate of the fluid to be measured flowing through the flow path,
The switching point of the two flow meters is based on the mass flow rate, and the switching point mass flow rate Qm in the range larger than the minimum flow rate of the vortex flow meter and smaller than the maximum flow rate of the thermal flow meter is Qm = K3 * √ Determined by P (where P: pressure of the flow path (variable), K3: flow area, vortex differential pressure, constant related to the vortex differential pressure, density of 1 atm at 0 ° C., pressure at 1 atm, Constant determined by
Multi-vortex flowmeter using mass flow rate as a switching point. In a multi-vortex flowmeter with a configuration that uses a vortex flowmeter that measures volumetric flow and a thermal flowmeter that measures mass flow, and uses these two flowmeters according to the flow rate of the fluid to be measured flowing through the flow path,
The switching point of the two flow meters is based on the mass flow rate, and the switching point mass flow rate Qm in the range larger than the minimum flow rate of the vortex flow meter and smaller than the maximum flow rate of the thermal flow meter is Qm = K4 * √ (P / T) (where P: pressure of the flow path (variable), T: absolute temperature of the fluid to be measured (variable), K4: area of the flow path, vortex differential pressure, vortex differential pressure related constant A constant determined by a density of 1 atm at 0 ° C., a pressure at 1 atm, and an absolute temperature (273.15 K) corresponding to 0 ° C.)
Multi-vortex flowmeter using mass flow rate as a switching point.

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