JP2012159484A - Mass flowmeter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a mass flowmeter applied to an artificial heart etc. which is a small and lightweight mass flowmeter reducing pressure loss without a moving part, using a bent tube, and capable of a simple flow rate measurement.SOLUTION: A mass flowmeter using a bent tube is provided with a pressure sensor for static pressure detection on a peripheral part of flow path of the bent tube and a pressure sensor for static pressure detection on a corresponding inner periphery of the flow path. A differential pressure is determined from the output difference of the both pressure sensors, and a flow rate is calculated from the differential pressure.

Description

  The present invention relates to a mass flow meter, and more particularly to a mass flow meter using a bent tube. Suitable for small and lightweight equipment that requires simple flow rate measurement, such as flow rate of fluid and gas flowing through plant piping such as petroleum, petrochemical, chemical, cleaning water for bottles, cleaning liquid for wafers and substrates, chemicals, etc. A simple mass flow meter.

Conventionally, as mass flowmeters using a bent tube, Patent Documents 1 to 3 and Patent Document 4 previously filed by the applicant are known. These are all due to measuring the distortion of the pipeline due to the centrifugal force of the fluid in the bent pipe section.
In addition, there are also known ones by measuring the concentration difference of fluid in a bent pipe part (Patent Document 5), and ones that measure the influence of Coriolis force by applying vibration to the pipe (Patent Document 6).

JP 2007-218775 A JP 2009-150671 A JP 2010-66184 A Japanese Patent Laid-Open No. 4-76519 Japanese Patent Laid-Open No. 9-79881 JP-A-8-114476

For example, mass flowmeters applied to artificial hearts, etc. require simple flow measurement that is small, lightweight, has little pressure loss, and has no moving parts. There are problems in that the size of the device increases, and that movable parts exist.
Furthermore, the method using the pipe strain on the outer peripheral surface of the bent pipe has a problem that a measurement error occurs due to the distortion of the pipe surface when an external force is applied. Further, the method using strain on the pipe surface has a problem that the amount of strain is reduced depending on the material of the pipe and the measurement sensitivity is lowered. Moreover, since it is necessary to affix a strain gauge to two places of a bending pipe, it was necessary to measure the measurement sensitivity with respect to static pressure beforehand and to match the measurement sensitivity.

In order to solve the above-mentioned problems, the present invention provides a mass flow meter using a bent pipe, wherein a pressure sensor for detecting static pressure is provided on the outer peripheral part of the flow path of the bent pipe, and the static pressure is provided on the corresponding inner peripheral part of the flow path. A pressure sensor for detection is provided, a differential pressure is obtained from an output difference between both pressure sensors, and a flow rate is obtained from the differential pressure.
Further, the present invention provides a mass flow meter using a bent pipe, wherein a pressure introduction pipe for detecting static pressure is attached to the outer peripheral part of the flow path of the bent pipe, and pressure introduction for detecting static pressure is introduced to the corresponding inner peripheral part of the flow path. A pipe is attached, both pressure introducing pipes are connected to a differential pressure gauge, a differential pressure is obtained, and a flow rate is obtained from the differential pressure.
Further, the present invention provides a mass flow meter using a bent pipe, wherein a pressure sensor for detecting static pressure is provided on the outer periphery of the flow path of the bent pipe, and a pressure sensor for detecting static pressure is provided on the straight pipe portion. It is characterized in that a differential pressure is obtained from the output difference and a flow rate is obtained from the differential pressure.
Further, the present invention is a mass flow meter using a bent pipe, wherein a pressure introduction pipe for detecting static pressure is attached to the outer periphery of the flow path of the bent pipe, and a pressure introduction pipe for detecting static pressure is attached to the straight pipe section, Both pressure introduction pipes are connected to a differential pressure gauge to obtain a differential pressure, and a flow rate is obtained from the differential pressure.
Further, the present invention provides a mass flow meter using a bent pipe, wherein a pressure introduction pipe for detecting static pressure is attached to the outer peripheral part of the flow path of the bent pipe, and pressure introduction for detecting static pressure is introduced to the corresponding inner peripheral part of the flow path. A pipe is attached, and both pressure introduction pipes are connected to form a communication pipe. The flow rate of the flow generated in the communication pipe caused by the differential pressure is measured to determine the differential pressure from the flow rate, and the flow rate of the bent pipe is calculated from the differential pressure. It is characterized by seeking.

Since the mass flow meter of the present invention uses a static pressure that increases due to centrifugal force, the mass flow meter has less pressure loss than a differential pressure type flow meter using an orifice plate using pressure loss. Moreover, since the sensor is only a pressure gauge, there is no moving part.
Further, since the difference between the two pressure sensors is taken, the influence of static pressure and temperature change can be compensated.
Further, since the pressure inside the pipe is directly measured using the pressure introduction hole, the measurement sensitivity is high without being affected by the material of the pipe. Further, it is possible to eliminate the influence of external force applied to the bent pipe.
Further, in the system in which pressure is introduced into one differential pressure gauge, the flow rate can be measured with a single sensor.
In addition, instead of introducing into the differential pressure gauge, the pressure introducing pipe is communicated as a communicating pipe, and the communicating pipe is connected from the outside of the communicating pipe wall by, for example, a heat flow meter with a heating element and a temperature detector disposed downstream thereof. The differential pressure can be obtained by measuring the flow rate of the fluid, and in this system, the fluid and the sensor part are completely in non-contact, and the influence of the sensor member touching fluid such as blood can be eliminated.

It is a figure which shows 1st Example by the static pressure difference of the static pressure in the bending part outer periphery which is one Example of the mass flowmeter of this invention, and the static pressure in a bending part inner peripheral part. The figure which verified the 1st Example. The figure which shows 2nd Example of this invention. The figure explaining the example by the static pressure difference of the static pressure in the bending part outer peripheral surface of a bending pipe, and the static pressure in a straight pipe part (the 1). Fig. 2 Fig. 3 The figure which shows 3rd Example of this invention. The figure which shows the 4th Example. A fifth embodiment of the present invention in which an introduction pipe is connected to form a communication pipe.

In order to obtain the mass flow rate in the pipeline of the bent pipe, the relationship between the mass flow rate and the pipeline internal pressure is derived. When calculating the balance of force at the bent part, assuming that the angular velocity ω does not depend on the radius of curvature r of the bent part and is constant in the pipe cross section of the bent pipe, the static pressure rise at the bent part is The relationship of the angular velocity corresponding to the flow rate is as follows.
Δp = p ₁ −p ₀ = (1/2) · ρω ² · (r ₁ ² −r ₀ ² )
Here, ρ is density, p is static pressure, p ₁ is static pressure at the outer periphery of the bent portion increased by centrifugal force, p ₀ is static pressure at the inner peripheral portion of the bent portion reduced by centrifugal force, and r ₁ is the outer peripheral curvature radius of the curved tube, r ₀ is the inner peripheral curvature radius of the curved tube.
Therefore, it was shown that the angular velocity ω corresponding to the flow velocity in the bent pipe can be obtained from the static pressure difference Δp that increases due to the centrifugal force. If the angular velocity ω is obtained, it is assumed that ω does not depend on the curvature radius r of the bent portion in the pipe cross section, and therefore the flow rate Q can be obtained by calculation. Therefore, if Δp is measured, the mass can be obtained. The flow rate Q can be uniquely determined. In actual measurement, a calibration formula is obtained in advance by measuring the relationship between Δp and flow rate Q.

In the above description, the static pressure difference between the static pressure at the outer peripheral portion of the bent portion and the static pressure at the inner peripheral portion of the bent portion is obtained, but as described below, the static pressure at the outer peripheral surface of the bent portion and Since it was also found that there is a unique relationship between the static pressure difference with the static pressure at the straight pipe section and the mass flow rate, the static pressure at the outer peripheral surface of the bent section and the static pressure at the straight pipe section The mass flow rate can also be obtained from the static pressure difference.
In the bent pipe shown in FIG. 4, the static pressure on the outer peripheral surface of the bent portion is measured at the position A, and the static pressure of the straight pipe portion is measured at the position B. FIG. 4 shows the static pressure distribution, FIG. 5 shows the static pressure on the outer peripheral surface of the bent pipe, and FIG. 6 shows the static pressure increased by the centrifugal force. As boundary conditions for numerical fluid analysis, the flow velocity on the inflow side was set to 1.0 m / sec, and the static pressure on the outflow side was set to 100 mmHg. The bent pipe used for the analysis is a flow path having a pipe inner diameter of 12 mm, R30 (curvature radius [mm] at the bent portion of the tube central axis), and a 120 ° bent portion in the middle. A working fluid having a specific gravity of 1.05 and a viscosity of 3 mPas equal to blood was set.
The pressure distribution shown by the gradient of the bent portion of the bent pipe in FIG. 4 indicates that the pressure value is the same as the gray density expressed in a columnar shape at the left end of the figure. FIG. 5 is a diagram showing the static pressure (kPa) on the vertical axis and the distance (distance from inlet) [mm] along the pipe from the inlet on the horizontal axis. The positions indicated by B correspond to the positions A and B in FIG. FIG. 6 is a graph showing the static pressure difference [Pa] between A and B on the vertical axis and the flow rate [L / min] on the horizontal axis. Shows that there is a unique relationship. Therefore, if the static pressure difference Δp between the static pressure at the outer peripheral surface of the bent portion and the static pressure at the straight pipe portion is measured, the flow rate can be obtained by calculation. In actual measurement, a calibration equation is obtained in advance by measuring the relationship between Δp and the flow rate.

Example 1
FIG. 1 shows a first embodiment which is an embodiment of the present invention. In mass flowmeters using two types of pressure sensors, pressure sensors for centrifugal force measurement are attached to the outer periphery and inner periphery of the bend, and the signals measured by each sensor are amplified by an amplifier, and the pressure difference and flow rate are measured in advance. By inputting to a flow rate output device incorporating a calibration formula, the mass flow rate can be measured from the difference in pressure measured by each sensor.
In FIG. 2, the vertical axis represents the static pressure difference (Δpressure) [mmHg] and the horizontal axis represents the flow rate (flow) [L / min]. The pressure difference (plotted with dots) measured by the mass flowmeter of the example was compared, and it was confirmed that there was a correlation as shown in the figure.

(Example 2)
FIG. 3 shows a second embodiment of the present invention. In a mass flow meter using one type of pressure sensor, pressure introduction holes for measuring centrifugal force are provided in the inner peripheral portion and the outer peripheral portion of the bending portion, and the internal pressure is introduced from each pressure introduction hole to the differential pressure gauge through a pressure introduction pipe. The mass flow rate can be measured by amplifying the signal measured by the differential pressure gauge with an amplifier and inputting the signal into a flow rate output device in which a pressure differential and a flow rate calibration formula are previously incorporated.

(Example 3)
FIG. 7 shows a third embodiment of the present invention. In a mass flow meter that uses two types of pressure sensors, one pressure sensor for centrifugal force measurement is attached to the bent part, and a pressure sensor for static pressure / temperature compensation is attached to the straight pipe part, and the signal measured by each sensor Is amplified by an amplifier and input to a flow rate output device incorporating a pressure difference and flow rate calibration formula in advance, whereby the mass flow rate can be measured from the pressure difference measured by each sensor.

Example 4
FIG. 8 shows a fourth embodiment of the present invention. In a mass flow meter that uses one type of pressure sensor, a pressure introduction hole for centrifugal force measurement is provided on the outer periphery of the bent part, and a pressure introduction hole for static pressure / temperature compensation is provided on the straight pipe part. The internal pressure is introduced to the differential pressure gauge by the pressure introduction pipe. The mass flow rate can be measured by amplifying the signal measured by the differential pressure gauge with an amplifier and inputting the signal into a flow rate output device in which a pressure differential and a flow rate calibration formula are previously incorporated.

(Example 5)
FIG. 9 shows a fifth embodiment of the present invention. In the second embodiment, the pressure introducing pipe is introduced into the differential pressure gauge. However, in the fifth embodiment, the pressure introducing pipe is communicated to generate a flow by the differential pressure as a communicating pipe. From the outside of the communicating pipe, for example, The differential pressure is obtained by measuring the flow rate of the communication pipe with a thermal flow meter comprising a heating element and a temperature detector disposed downstream thereof.

  Compared to Coriolis flowmeters, electromagnetic flowmeters, and ultrasonic flowmeters that have been used for industrial use, the mass flowmeter of the present invention is overwhelmingly cheap and has a simple structure and measurement response. Therefore, it is a technology that can replace the flowmeter currently used in industry as it is. As a specific application example, it is conceivable to measure the flow rate of fluids and gases flowing through the piping of plants such as petroleum, petrochemicals, and chemicals, cleaning water for bottles, cleaning liquid for wafers and substrates, and chemicals.

Claims (5)

  In a mass flow meter using a bent pipe, a pressure sensor for detecting static pressure is provided on the outer periphery of the flow path of the bent pipe, and a pressure sensor for detecting static pressure is provided on the inner periphery of the corresponding flow path. A mass flowmeter characterized by obtaining a differential pressure from an output difference and obtaining a flow rate from the differential pressure.   In a mass flow meter using a bent pipe, a pressure introduction pipe for detecting static pressure is attached to the outer periphery of the flow path of the bent pipe, and a pressure introduction pipe for detecting static pressure is attached to the inner circumference of the corresponding flow path. A mass flow meter characterized in that an introduction pipe is connected to a differential pressure gauge to obtain a differential pressure, and a flow rate is obtained from the differential pressure.   In a mass flow meter using a bent pipe, a pressure sensor for detecting static pressure is provided on the outer periphery of the flow path of the bent pipe, and a pressure sensor for detecting static pressure is provided on the straight pipe section. And a flow rate is obtained from the differential pressure.   In a mass flowmeter using a bent pipe, a pressure introduction pipe for static pressure detection is attached to the outer periphery of the flow path of the bent pipe, a pressure introduction pipe for static pressure detection is attached to the straight pipe section, and both pressure introduction pipes are connected. A mass flow meter characterized in that a differential pressure is obtained by connecting to a pressure gauge, and a flow rate is obtained from the differential pressure.   In a mass flow meter using a bent pipe, a pressure introduction pipe for detecting static pressure is attached to the outer periphery of the flow path of the bent pipe, and a pressure introduction pipe for detecting static pressure is attached to the inner circumference of the corresponding flow path. The introduction pipe is connected to form a communication pipe, and the flow rate of the flow generated in the communication pipe caused by the differential pressure is measured to determine the differential pressure from the flow rate, and the flow rate of the bent pipe is determined from the differential pressure. Mass flow meter.