JP2021139739A - Thermal flowmeter - Google Patents

Abstract

To enable measurement by a thermal flowmeter in which effects of convection current, etc., are taken into account to be easily carried out.SOLUTION: A measurement tube 101 is used by being connected to pipings 103a, 103b in which the fluid to be measured is transported. The piping 103a connects to one end of the measurement tube 101 and the piping 103b connects to the other end of the measurement tube 101, the measurement tube 101 being connected in the middle of the piping. The tube axis of the measurement tube 101 is at 45° to the tube axes of the pipings 103a, 103b. The tube axis of the piping 103a and the tube axis of the piping 103b are parallel to each other. At a point where a sensor part 102 of the measurement tube 101 is installed, the angle between a direction in which gravity acts and the tube axis of the measurement tube 101 is 45°.SELECTED DRAWING: Figure 1A

Description

The present invention relates to a thermal flow meter, and more particularly to a thermal flow meter including a measuring tube connected to a pipe through which a fluid to be measured flows and a sensor provided in the measuring tube.

Technology for measuring the flow rate and flow velocity of fluid flowing through a flow path is widely used in the industrial and medical fields. There are various types of devices for measuring flow rate and flow velocity, such as an electromagnetic flow meter, a vortex flow meter, a Koriori type flow meter, and a thermal flow meter, and they are used properly according to the application. The thermal flow meter can also measure gas, and by installing the sensor on the outer peripheral surface of the pipe, there is basically no pressure loss, and there are advantages such as being able to measure the mass flow rate ( See Patent Document 1). Thermal flow meters include a type that measures the flow rate by the power consumption of the heater and a type that measures the flow rate by the temperature difference between the upstream and downstream of the heater.

Japanese Unexamined Patent Publication No. 11-190647

By the way, when the direction of the pipe is perpendicular to the ground, not only the heat transfer due to the flow but also the heat transfer due to the influence of convection occurs in the fluid transported in the discontinued publication. Due to this phenomenon, the thermal flow meter may not be able to measure an accurate flow rate. In particular, when the flow velocity is close to 0, the proportion of the influence of the above-mentioned convection becomes large, and the measured result greatly deviates from the actual flow velocity.

A technique for correcting the measurement result of the thermal flowmeter has been proposed in consideration of such an influence in advance (see Patent Document 1). However, since the influence of convection differs depending on the primary pressure and fluid characteristics, a large amount of data and complicated calculations are required to carry out the correction by the above-mentioned technique. Further, since the primary pressure is not always constant, it is necessary to dynamically acquire the primary pressure with a pressure sensor.

As described above, conventionally, there has been a problem that measurement by a thermal flow meter in consideration of the influence of convection cannot be easily performed.

The present invention has been made to solve the above problems, and an object of the present invention is to make it easier to perform measurement with a thermal flowmeter in consideration of the influence of convection.

The thermal flow meter according to the present invention is provided in contact with a measuring tube in which the angle formed by each tube axis is 45 ° and an outer wall of the measuring tube with respect to the pipe through which the fluid to be measured is transported. It is equipped with a heater that heats the fluid and a temperature measuring unit that is provided in contact with the outer wall of the measuring tube to measure the temperature of the fluid, and the difference between the temperature of the heater and the temperature of the fluid at a position that is not affected by the heat of the heater is set. It is provided with a sensor unit configured to output a sensor value corresponding to a state of heat diffusion in the fluid heated by the heater when the heater is driven so as to have a set temperature difference.

In one configuration example of the thermal flowmeter, the measuring tube is composed of a first tube provided with a sensor unit and a second tube connected to the first tube with an angle formed by each tube axis at 90 °. It is configured.

In one configuration example of the thermal flow meter, the measuring pipes are a first pipe provided with a sensor unit and a second pipe connected to the first pipe at an angle formed by each pipe shaft at 45 °. , The second pipe is composed of a third pipe connected to the second pipe with an angle formed by each pipe shaft at 45 °, and the first pipe and the third pipe have an angle formed by each pipe shaft of 90 °. It is said that.

In one configuration example of the thermal flow meter, the measuring pipe is connected in the middle of the pipe.

In one configuration example of the thermal flow meter, the pipe shaft of the pipe connected to one end side of the measuring pipe and the pipe shaft of the pipe connected to the other end side of the measuring pipe are parallel to each other.

In one configuration example of the thermal flowmeter, the angle between the direction in which gravity acts and the tube axis is 45 ° at the location where the sensor unit of the measuring tube is provided.

In one configuration example of the thermal flow meter, the temperature measuring unit measures the temperature of the fluid at a position upstream of the heater and is not affected by the heat of the heater, and the sensor unit measures the temperature of the heater and the temperature measuring unit. The power of the heater when the heater is driven so that the difference from the temperature of the fluid is the set temperature difference is output as a sensor value.

In one configuration example of the thermal flow meter, the temperature measuring unit is composed of a first temperature measuring unit, a second temperature measuring unit, and a third temperature measuring unit, and the first temperature measuring unit is a heater on the upstream side of the heater. The temperature of the fluid at the position not affected by the heat of the heater is measured, the second temperature measuring unit measures the temperature of the fluid at the position upstream from the heater, and the third temperature measuring unit is the heater. The temperature of the fluid at the position affected by the heat of the heater is measured on the downstream side, and the sensor unit makes the difference between the temperature of the heater and the temperature of the fluid measured by the first temperature measurement unit the set temperature difference. The temperature difference between the temperature of the fluid measured by the second temperature measuring unit and the temperature of the fluid measured by the third temperature measuring unit when the heater is being driven is output as a sensor value.

As described above, according to the present invention, the measuring tube provided with the sensor unit is in a state where the angle formed by each tube axis is 45 ° with respect to the piping through which the fluid to be measured is transported. , Measurement by a thermal flow meter considering the influence of convection can be carried out more easily.

FIG. 1A is a configuration diagram showing a configuration of a thermal flowmeter according to an embodiment of the present invention. FIG. 1B is a configuration diagram showing a configuration of a thermal flowmeter according to an embodiment of the present invention. FIG. 2 is a configuration diagram showing a more detailed configuration of the thermal flow meter according to the embodiment of the present invention. FIG. 3 is a configuration diagram showing a more detailed configuration of the thermal flow meter according to the embodiment of the present invention. FIG. 4 is a configuration diagram showing the configuration of another thermal flowmeter according to the embodiment of the present invention. FIG. 5 is a configuration diagram showing the configuration of another thermal flowmeter according to the embodiment of the present invention. FIG. 6 is a configuration diagram showing the configuration of another thermal flowmeter according to the embodiment of the present invention.

Hereinafter, the thermal flowmeter according to the embodiment of the present invention will be described with reference to FIGS. 1A and 1B. This thermal flowmeter includes a measuring tube 101 and a sensor unit 102. 1A and 1B show the side surface of the measuring tube 101.

The measuring tube 101 is used by being connected to the pipes 103a and 103b to which the fluid to be measured is transported. The measuring tube 101 can be made of, for example, plastic, glass, sapphire, metal, or the like. In this example, the pipe 103a is connected to one end of the measuring pipe 101, the pipe 103b is connected to the other end of the measuring pipe 101, and the measuring pipe 101 is connected in the middle of the pipe. Further, the tube axis of the measuring tube 101 is set to 45 ° with respect to the tube axes of the pipes 103a and 103b. The pipe shaft of the pipe 103a and the pipe shaft of the pipe 103b are parallel to each other. Further, in the pipes 103a and 103b, the pipe shafts are arranged horizontally or perpendicularly to the ground.

At the location where the sensor unit 102 of the measuring tube 101 is provided, the tube axis is 45 ° with respect to the ground, and at the location where the sensor unit 102 of the measuring tube 101 is provided, gravity acts in a direction perpendicular to the ground. The angle formed by the direction (y-axis direction) and the tube axis of the measuring tube 101 is 45 °. In FIG. 1A, the pipe axis of the pipe 103a and the pipe axis of the pipe 103b are in a direction (X-axis direction) perpendicular to the direction in which gravity acts (y-axis direction). On the other hand, in FIG. 1B, the pipe shaft of the pipe 103a and the pipe shaft of the pipe 103b are in the direction in which gravity acts (y-axis direction). According to the embodiment, as shown in FIGS. 1A and 1B, even if the pipe shaft of the pipe 103a and the pipe shaft of the pipe 103b are different by 90 °, the position where the sensor unit 102 of the measuring pipe 101 is provided. The angle formed by the y-axis direction and the tube axis of the measuring tube 101 is 45 °.

The sensor unit 102 includes a temperature measuring unit 111, a heater 112, a control unit 113, and a power measuring unit 114. The temperature measuring unit 111 is provided in contact with the outer wall of the measuring tube 101. The heater 112 is provided in contact with the outer wall of the measuring tube 101 on the downstream side of the temperature measuring unit 111. The temperature measuring unit 111 and the heater 112 are adhesively fixed to the outer wall of the measuring tube 101 with, for example, a heat conductive adhesive. The temperature measuring unit 111 measures the temperature of the fluid.

Here, the sensor unit 102 drives the heater 112 so that the difference between the temperature of the heater 112 and the temperature of the fluid at a position not affected by the heat of the heater 112 is a set set temperature difference. At that time, the sensor value corresponding to the state of heat diffusion in the fluid heated to the heater 112 is output. In the embodiment, the difference between the temperature of the heater 112 and the position of the control unit 113 that is not affected by the heat of the heater 112 measured by the temperature measuring unit 111, for example, the temperature of the fluid upstream of the heater 112 is set in advance. The heater 112 is controlled and driven so as to have a set temperature difference.

Further, the electric power measuring unit 114 measures and outputs the electric power of the heater 112 controlled by the control unit 113. The electric power output from the electric power measuring unit 114 constituting the sensor unit 102 becomes the sensor value. The flow rate calculation unit 115 calculates the flow rate of the fluid from the electric power (sensor value) of the heater 112 measured and output by the power measurement unit 114.

As is well known, when the heater 112 is driven so that the difference between the temperature of the heater 112 and the temperature of the fluid at a position not affected by the heat of the heater 112 is the set temperature difference, the heater 112 There is a correlation between the power consumed and the flow rate of the fluid. This correlation is also reproducible at the same fluid / flow rate / temperature. Therefore, as described above, the flow rate is calculated by using a predetermined correlation coefficient (constant) in the flow rate calculation unit 115 from the power measured by the power measurement unit 114 while the heater 112 is controlled by the control unit 113. Can be calculated.

As shown in FIG. 3, the temperature measuring unit (first temperature measuring unit) 111, the heater 112, the control unit 113, the temperature measuring unit (second temperature measuring unit) 116, and the temperature measuring unit (third temperature measuring unit) The sensor unit 102'can also be configured from 117. Each temperature measuring unit is provided in contact with the outer wall of the measuring tube 101.

The control unit 113 sets a preset temperature at which the difference between the temperature of the heater 112 and the temperature of the fluid measured at a position not affected by the heat of the heater 112 measured by the temperature measuring unit 111, for example, upstream of the heater 112 is set in advance. The heater 112 is controlled and driven so as to make a difference.

The temperature measuring unit 116 is provided in contact with the outer wall of the measuring tube 101 on the downstream side of the temperature measuring unit 111 and on the upstream side of the heater 112. Further, the temperature measuring unit 117 is provided on the downstream side of the heater 112 in contact with the outer wall of the measuring tube 101. The temperature measuring unit 116 and the temperature measuring unit 117 measure the temperature of the fluid.

The flow rate of the fluid can be calculated from the temperature difference between the temperature of the fluid measured by the temperature measuring unit 116 and the temperature of the fluid measured by the temperature measuring unit 117. In this example, the temperature difference between the temperature of the fluid measured by the temperature measuring unit 116 and the temperature of the fluid measured by the temperature measuring unit 117 is the sensor value.

As is well known, the heater 112 is driven so that the difference between the temperature of the heater 112 and the temperature of the fluid at a position not affected by the heat of the heater 112 becomes a preset set temperature difference. At that time, there is a correlation between the temperature difference between the temperature of the fluid upstream of the heater 112 and the temperature of the fluid downstream of the heater 112 and the flow rate of the fluid. This correlation is also reproducible at the same fluid / flow rate / temperature. Therefore, as described above, a predetermined phase is obtained from the difference (temperature difference) between the temperature measured by the temperature measuring unit 116 and the temperature measured by the temperature measuring unit 117 while the heater 112 is controlled by the control unit 113. The flow rate can be calculated by using the number of relations (constant).

As shown above, according to the embodiment. Even if the pipe axis of the pipe in which the pipe axis is arranged horizontally or perpendicularly to the ground is different by 90 °, the pipe axis is 45 ° with respect to the ground at the place where the sensor part of the measuring pipe is provided. , The characteristics such as the influence of convection are the same. In this way, if the characteristics of the measurement environment are the same, it can be used by common adjustment and calibration regardless of the usage pattern. As described above, according to the embodiment, the measurement by the thermal flowmeter in consideration of the influence of convection and the like can be carried out more easily.

By the way, as shown in FIG. 4, a measuring tube is formed from a first tube 104 provided with a sensor unit 102 and a second tube 105 connected to the first tube 104 with an angle formed by each tube axis at 90 °. 101a can also be configured.

Further, as shown in FIG. 5, the first pipe 104 provided with the sensor unit 102 and the second pipe 105a connected to the first pipe 104 at an angle formed by each pipe shaft at 45 °, and the second pipe 105a. The measuring tube 101b can also be configured from the third tube 106 connected to the two tubes 105a so that the angle formed by each tube axis is 45 °. The angle formed by the respective pipe axes of the first pipe 104 and the third pipe 106 is 90 °.

Further, as shown in FIG. 6, the measuring pipe 101 may be connected to the pipe 103a via the introduction pipe 107. In the introduction tube 107, the angle formed by each of the measuring tubes 101 and 103a is, for example, 22.5 °, and the sum of the two, that is, the respective tube axes of the measuring tube 101 and the measuring tube 103a. It is configured so that the angle between them is 45 °. By providing the introduction pipe 107 in this way and connecting the pipe 103a on the inflow side to the measuring pipe 101 at a stepwise angle, the curve of the flow path becomes gentle, the flow is less likely to be disturbed, and the measurement accuracy is improved. You will be able to improve.

In each drawing, the connection points of each pipe are represented by straight lines for ease of explanation. However, in carrying out the present invention, each connection point is rounded in order to avoid an adverse effect of disturbing the fluid flow. It is desirable to configure.

As described above, according to the present invention, the measuring tube provided with the sensor unit is set so that the angle formed by each tube axis is 45 ° with respect to the piping through which the fluid to be measured is transported. Therefore, the measurement by the thermal flow meter considering the influence of convection can be carried out more easily.

The present invention is not limited to the embodiments described above, and many modifications and combinations can be carried out by a person having ordinary knowledge in the art within the technical idea of the present invention. That is clear. As an example, in the present invention, the thermal flow meter that heats the fluid flowing through the measuring tube 101 by the heater 112 has been mentioned, but instead of the heater, an electronic cooling element (Pelche element or the like) is used to heat the fluid in the measuring tube. The technical idea of the present invention is similarly applicable to a cooling type thermal flow meter that cools and detects a temperature rise according to the flow rate and calculates the flow rate.

101 ... Measuring tube, 102 ... Sensor unit, 103a, 103b ... Piping.

Claims (8)

A measuring pipe in which the angle formed by each pipe axis is 45 ° with respect to the pipe in which the fluid to be measured is transported.
A heater provided in contact with the outer wall of the measuring tube to heat the fluid and a temperature measuring unit provided in contact with the outer wall of the measuring tube to measure the temperature of the fluid are provided, and the temperature of the heater and the heater of the heater are provided. The state of heat diffusion in the fluid heated by the heater when the heater is driven so that the difference from the temperature of the fluid at a position not affected by heat becomes a set temperature difference. A thermal fluid meter with a sensor unit configured to output the corresponding sensor value. In the thermal flow meter according to claim 1,
The measuring tube is characterized in that it is composed of a first tube provided with the sensor unit and a second tube connected to the first tube with an angle formed by each tube axis at 90 °. Thermal flow meter. In the thermal flow meter according to claim 1,
The measuring tube is
The first tube provided with the sensor unit and
A second pipe connected to the first pipe with an angle formed by each pipe shaft at 45 °.
It is composed of a third pipe connected to the second pipe with an angle formed by each pipe shaft at 45 °.
A thermal flowmeter characterized in that the angle formed by the first pipe and the third pipe is 90 °. In the thermal flow meter according to any one of claims 1 to 3,
The measuring pipe is a thermal flow meter characterized in that it is connected in the middle of the pipe. In the thermal flow meter according to claim 4,
A thermal flow rate characterized in that the pipe shaft of the pipe connected to one end side of the measuring pipe and the pipe shaft of the pipe connected to the other end side of the measuring pipe are parallel to each other. Total. In the thermal flow meter according to any one of claims 1 to 5,
The location where the sensor portion of the measuring tube is provided is a thermal flow meter characterized in that the angle formed by the direction in which gravity acts and the tube axis is 45 °. In the thermal flow meter according to any one of claims 1 to 5,
The temperature measuring unit measures the temperature of the fluid at a position upstream of the heater and not affected by the heat of the heater.
The sensor unit uses the power of the heater when the heater is driven so that the difference between the temperature of the heater and the temperature of the fluid measured by the temperature measuring unit becomes the set temperature difference. A thermal flowmeter characterized by outputting as a value. In the thermal flow meter according to any one of claims 1 to 6,
The temperature measuring unit is composed of a first temperature measuring unit, a second temperature measuring unit, and a third temperature measuring unit.
The first temperature measuring unit measures the temperature of the fluid at a position upstream of the heater and not affected by the heat of the heater.
The second temperature measuring unit measures the temperature of the fluid at a position upstream of the heater and affected by the heat of the heater.
The third temperature measuring unit measures the temperature of the fluid at a position downstream of the heater and affected by the heat of the heater.
The sensor unit drives the heater so that the difference between the temperature of the heater and the temperature of the fluid measured by the first temperature measuring unit becomes the set temperature difference, the second temperature. A thermal flow meter characterized in that the temperature difference between the temperature of the fluid measured by the measuring unit and the temperature of the fluid measured by the third temperature measuring unit is output as the sensor value.

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