Temperature sensor, and mass flow meter and mass flow control device equipped therewith.

Abstract

In the present invention, a temperature sensor used in a mass flow rate meter is configured from a flow path through which a fluid flows, a temperature measurement means that has a temperature measurement point at the center of a lateral cross-section of the flow path, and a soaking means provided farther upstream in the flow path than the temperature measurement point. The soaking means is provided with a grating provided continuously in a discretionary direction perpendicular to the direction in which the fluid flows, and an auxiliary flow path that is branched by the grating. This makes it possible to realize a temperature sensor with which it is possible to acquire a temperature measurement value representing the temperature of a fluid that is supplied to a mass flow rate meter from the outside, even when the temperature of the fluid fluctuates.

Description

Technical Field

[0001] This invention relates to a temperature sensor used in a mass flowmeter.

Background Art

[0002] A mass flow control device includes a mass flowmeter and a flow control valve, and is a device that controls the opening of the flow control valve so that the mass flow rate of a fluid measured by the mass flowmeter matches a predetermined target value. The mass flow control device is widely used for the purpose of quantitatively supplying a gas used in the manufacturing process of a semiconductor manufacturing device. In recent years, with the progress of semiconductor manufacturing technology, various types of gases are being used. Among such gases, for example, there are gases that must be handled while maintaining a temperature higher than room temperature for the purpose of preventing liquefaction in the flow path.

[0003] The volume and pressure of a gas vary greatly depending on the temperature. Therefore, in order to quantitatively supply a gas with high accuracy in a mass flow control device, it is preferable to accurately measure the temperature of the gas flowing inside the mass flow control device. Some conventional mass flow control devices include a temperature sensor for the purpose of measuring the temperature of a gas. For example, Patent Documents 1 and 2 disclose inventions of mass flow control devices in which a temperature sensor is provided inside or on the surface of a main body block, and Patent Document 3 discloses an invention of a mass flow control device in which a temperature sensor is attached so as to face a flow path inside a main body block.

[0004] Furthermore, the heat capacity per unit volume of gas is very small compared to solids and liquids. Therefore, if the temperature of the flow path inside the mass flow control device differs from the temperature of the gas in contact with it, heat exchange occurs between the two, and the temperature of the gas with low heat capacity may easily change. Some conventional mass flow control devices have a main block (base) and flow sensor covered with a metal block, and a heater provided in the block can maintain the temperature of the entire gas flow path at a high temperature (see, for example, Patent Document 4). By using such a mass flow control device, the temperature of the gas flowing inside and the temperature of the inner wall of the flow path in contact with the gas can be made the same, so that a gas that easily liquefies at room temperature can be stably and quantitatively supplied. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 7-230322 [Patent Document 2] Japanese Patent Publication No. 2020-123065 [Patent Document 3] Japanese Patent Application Publication No. 8-63235 [Patent Document 4] International Publication No. 2015 / 141437 [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] However, in reality, the temperature of the gas may change for various reasons. As the gas temperature changes, the volume and pressure of the gas also change, which may cause the gas flow rate controlled by the mass flow control device to deviate from the target value. Therefore, it is preferable to immediately detect any changes in the temperature of the gas supplied from an external source and adjust the flow rate accordingly. However, in the conventional mass flow control devices described above, temperature sensors are installed in the main body block, which has a large heat capacity, or in the flow path inside it. As a result, even if the gas temperature changes, it is difficult to immediately adjust the output of the temperature sensors to reflect the changed gas temperature.

[0007] Therefore, it is conceivable to install a temperature sensor with a small heat capacity, insulated from the main block, inside the gas flow path of the mass flow control device. However, even in this case, the temperature at the temperature sensor's measuring point does not necessarily accurately reflect the temperature of the gas supplied to the mass flow control device. For example, if the cross-section of the flow path is circular, the gas flowing near the inner wall of the flow path is susceptible to temperature changes due to the temperature difference with the inner wall, while the gas flowing near the center of the flow path is hardly affected by the inner wall temperature. Therefore, even if the temperature is measured at a measuring point near the center of the flow path to avoid the influence of heat from the main block, the measured value cannot be said to be a representative value of the overall temperature of the gas flowing through the flow path (for example, the average temperature of the gas over the entire cross-section of the flow path). Similar problems arise when the temperature of the gas supplied to the mass flow control device is constant, but there is a change in the temperature of the gas flow path in the mass flow control device.

[0008] This invention has been made in view of the above-mentioned problems, and aims to improve the accuracy of flow rate control by obtaining a temperature measurement that represents the overall temperature of the fluid supplied externally to the mass flow control device and using it. [Means for solving the problem]

[0009] The temperature sensor according to the present invention is a temperature sensor used in a mass flow meter, comprising a flow path through which a fluid flows, a temperature measuring means having a temperature measuring point at a predetermined position inside the flow path, and a heat equalization means provided upstream of the temperature measuring point in the flow path, wherein the heat equalization means comprises a grid continuously provided in any direction perpendicular to the direction in which the fluid flows, and sub-flow paths divided by the grid.

[0010] In a temperature sensor with the configuration of the present invention, fluid vortices are generated downstream of the grid, causing heat transfer by convection. Heat is also transferred by conduction within the continuous grid and by conduction between the fluid flowing through the subchannels and the grid. Due to these actions of the heat equalization means, the fluid that reaches the downstream temperature measuring means has a more uniform temperature distribution within the flow path compared to when no heat equalization means is provided.

[0011] In a preferred embodiment of the present invention, the temperature sensor includes a heating means in the flow path. In another embodiment, the present invention is a mass flow meter or mass flow control device equipped with the above-mentioned temperature sensor. [Effects of the Invention]

[0012] The temperature sensor according to the present invention can acquire a temperature measurement that represents the overall temperature of the fluid flowing through the channel. By using the acquired temperature measurement, it is possible to correct the flow rate measurement of the fluid flowing through the channel more appropriately than with conventional technology, and to control the flow rate with higher precision using the corrected flow rate measurement. [Brief explanation of the drawing]

[0013] [Figure 1] This is a cross-sectional view showing an example of a mass flow meter equipped with a temperature sensor according to the present invention. [Figure 2] This is a conceptual diagram showing a cylindrical coordinate system that can be applied to a flow path. [Figure 3] This is a cross-sectional view showing the operation of the heat equalization means provided in the temperature sensor according to the present invention. [Figure 4]It is a schematic diagram showing an example of the temperature distribution of a fluid flowing through the flow path of the temperature sensor according to the present invention. [Figure 5] It is a schematic diagram showing an example of the heat equalizing means provided in the temperature sensor according to the present invention. [Figure 6] It is a schematic diagram showing another example of the heat equalizing means provided in the temperature sensor according to the present invention. [Figure 7] It is a schematic diagram showing another example of the heat equalizing means provided in the temperature sensor according to the present invention. [Figure 8] It is a cross-sectional view showing the configuration of the temperature sensor according to an embodiment of the present invention. [Figure 9] It is a graph showing the results of temperature measurements at the first temperature measurement point and the second temperature measurement point by the temperature sensor according to an embodiment of the present invention and the temperature sensor according to the comparative example.

Embodiments for Carrying Out the Invention

[0014] Embodiments for carrying out the present invention will be described below with reference to the drawings. Note that the present invention is not limited to the embodiments described below. The present invention can be implemented in any form as long as it does not deviate from the scope of the technical idea described in the specification, claims, and drawings attached to the application.

[0015] The temperature sensor according to the present invention is a temperature sensor used in a mass flow meter, and includes a flow path, temperature measuring means, and heat equalizing means. Fig. 1 is a schematic diagram showing an example of a mass flow meter 7 provided with the temperature sensor 1 according to the present invention. The flow path 2 is a member through which a fluid flows inside. The flow path 2 may be constituted by a tube having a predetermined thickness as illustrated in Fig. 1, or may be constituted by a block-shaped main body with a hole formed therein. The inner cross-section of the flow path 2 may be circular, or may have other shapes. In the mass flow meter 7 illustrated in Fig. 1, the flow path 2 is constituted by a straight cylinder having a constant diameter. The dashed line passing through the center of the flow path 2 indicates the central axis of the flow path 2. Fig. 1 depicts a cross-section of the mass flow meter � cut by a plane including the central axis. The white arrow in Fig. 1 represents the direction in which the fluid flows inside the flow path 2.

[0016] The temperature measuring means 3 included in the temperature sensor 1 according to the present invention measures the temperature of the fluid flowing through the flow path 2. The temperature measuring means 3 has a temperature measuring point 3a at a predetermined position inside the flow path 2. The temperature measuring point 3a refers to the position where the temperature of the fluid is measured in the temperature measuring means 3. The temperature measuring means 3 continuously observes the constantly changing temperature of the fluid flowing through the flow path 2 at the temperature measuring point 3a fixed to the flow path 2. Since the temperature measuring means 3 measures the temperature of the fluid pinpoint, when there is a bias in the temperature distribution of the fluid in the flow path, the temperature measurement value measured by the temperature measuring means 3 does not directly represent the temperature of the entire fluid as it is. As described above, the measurement value representing the temperature of the entire fluid refers to, for example, the average temperature of the gas across the entire cross section of the flow path.

[0017] As will be described in detail later, in the temperature sensor 1 according to the present invention, the temperature distribution of the fluid in the radial direction of the flow path becomes more uniform by the heat equalizing means 4. Therefore, even when the temperature measuring point 3a is located at a position other than the center of the cross section of the flow path 2, a measurement value closer to the temperature measurement value representing the temperature of the entire fluid flowing through the flow path can be obtained compared to a temperature sensor according to the prior art without the heat equalizing means 4. From such a viewpoint, the temperature measuring means 3 can have a temperature measuring point 3a at a predetermined position inside the flow path 2. Also, as will be described later, a plurality of temperature measuring points may be provided in the temperature sensor 1 according to the present invention.

[0018] In a preferred embodiment of the present invention, as illustrated in Figure 1, the temperature measuring point 3a is located at the center of the cross-section of the flow path 2, that is, close to the central axis of the flow path 2. In the present invention, "center of the cross-section of the flow path" refers to a position close to the central axis of the flow path 2, and away from the inner wall of the flow path 2, so that it is less affected by temperature changes in the flow path 2. For example, "center of the cross-section of the flow path" can be defined as a region that includes positional errors that may occur when attempting to place the temperature measuring point on the central axis of the flow path 2. Therefore, the position of the temperature measuring point 3a does not need to perfectly coincide with the position of the central axis of the flow path 2. The temperature measuring point 3a of the temperature sensor shown in Figure 1 is located near the tip of the protective tube 3b. The protective tube 3b is fixed to the flow path 2 so that the position of the temperature measuring point 3a is at the center of the flow path 2.

[0019] Because the protective tube 3b is thin and has a small cross-sectional area, heat from the flow path 2 is not easily conducted to the temperature measuring point 3a. In other words, the flow path 2 and the temperature measuring point 3a of the temperature measuring means 3 are thermally separated. Therefore, the temperature measuring means 3 can measure the temperature of the fluid without being affected by the temperature of the flow path 2. Furthermore, by making the wall thickness of the protective tube 3b as thin as possible and reducing the heat capacity of the temperature measuring means 3 including the temperature measuring point 3a, the temperature of the fluid measured by the temperature measuring means 3 can be matched to the actual temperature change of the fluid in a short time.

[0020] The temperature information measured at the temperature measuring point 3a of the temperature measuring means 3 is converted into an electrical signal, which travels through lead wires inside the protective tube 3b to the base 3c, and is transmitted to the outside of the temperature measuring means 3 through the connector 3d and a cable (not shown), where it is converted into a temperature measurement value. Specific elements housed in the protective tube 3b include, for example, known temperature measuring elements such as resistance thermometers, thermistors, and thermocouples.

[0021] To facilitate the following explanation, a cylindrical coordinate system applicable to the flow path 2 of the present invention will be described with reference to Figure 2. In Figure 2, O is the origin of the cylindrical coordinate system. The origin O can be set at any position on the central axis of the flow path 2 shown in Figure 1, for example, at the upstream end of the flow path 2.

[0022] The axis L extending from the origin O to the right in Figure 2 is called the cylindrical axis. The position of the cylindrical axis L coincides with the position of the central axis of the flow path 2. The positive direction of the cylindrical axis L coincides with the direction from the upstream side to the downstream side of the flow path 2. The axis A extending upward from the origin O in Figure 2 is called the polar axis. The direction of the polar axis A defines the reference direction in the plane perpendicular to the cylindrical axis L of the cylindrical coordinate system. The direction of the polar axis A can be set to coincide with, for example, the up and down direction in Figure 1. In the example shown in Figure 1, since the protective tube 3b is provided in the up and down direction, the direction of the polar axis A coincides with the direction in which the protective tube 3b is provided. The positive direction of the polar axis A can be set to coincide with, for example, the direction from the bottom to the top in Figure 1.

[0023] The position of any point P in a cylindrical coordinate system can be expressed as P(r,θ,z) using three coordinates: r, θ, and z. r is called the radial coordinate and is the distance between the origin O and the origin O. P'(r,θ,0) is the projection of point P onto a plane containing the origin O and perpendicular to the cylindrical axis L. θ is called the azimuth angle and is the angle between the polar axis A and the line segment OP'. z is called the height and is the distance between point P and the plane containing the origin O and perpendicular to the cylindrical axis L.

[0024] Referring again to Figure 1, the temperature sensor 1 according to the present invention includes a heat equalization means 4 provided upstream of the temperature measurement point 3a in the flow path 2. The heat equalization means 4 includes a grid 4a (not shown) provided continuously in any direction perpendicular to the direction of fluid flow, and sub-flow paths 4b (not shown) divided by the grid 4a. In the present invention, "grid" refers to partitions arranged periodically. In the heat equalization means 4, the flow path 2 is divided into a number of sub-flow paths 4b by the grid 4a. That is, the grid 4a constitutes the walls of the sub-flow paths 4b, and the spaces between the grids 4a constitute the sub-flow paths 4b.

[0025] The fluid flow that reaches the heat soaking means 4 through the channel 2 is divided by the grid 4a and branches into flows that flow inside a number of subchannels 4b. The subchannels 4b connect the upstream and downstream sides of the heat soaking means 4. The subchannels 4b may connect the upstream inlet and downstream outlet of the heat soaking means 4 with a single channel, or multiple subchannels 4b may merge and branch again inside the heat soaking means 4. The fluid that flows out downstream from the subchannels 4b loses its partition and the entire flow merges again to form the flow inside the channel 2.

[0026] The grid 4a is provided continuously in any direction perpendicular to the direction of fluid flow. Referring to Figure 2, the direction of fluid flow is the positive direction of the cylindrical axis L. Any direction perpendicular to the direction of fluid flow is the direction of vector OP' at any azimuth angle θ. That is, the grid 4a is provided continuously in any direction in the plane perpendicular to the direction of fluid flow. Here, in the present invention, "provided continuously" of the grid 4a means that the members constituting the grid 4a are provided without interruption throughout the entire heat equalization means 4, except for the portion of the subchannel 4b. Detailed embodiments of the grid 4a will be described later.

[0027] Next, the operation of the heat equalization means 4 provided in the temperature sensor 1 according to the present invention will be described. Figure 3 is a cross-sectional view showing the operation of the heat equalization means 4. The grid 4a of the heat equalization means 4 illustrated in Figure 3 is composed of a mesh woven with wire. The circular cross-section near the center of Figure 3 represents the cross-section of the weft threads that make up the mesh. The dashed lines extending vertically represent the positions of the warp threads that make up the mesh. The heat equalization means 4 is composed of a plain weave mesh that is continuously provided in any direction perpendicular to the direction of fluid flow. The spaces between the grid 4a constitute the sub-channels 4b.

[0028] The fluid flows through channel 2 from left to right in Figure 3. The fluid that reaches the heat soaking means 4 branches off into numerous subchannels 4b, passes through the heat soaking means 4, and then rejoins. At this time, at a position corresponding to the rear of grid 4a when viewed from the upstream side of channel 2, the fluid whose flow is obstructed by grid 4a bends around and forms vortices. The size of the vortices generated at the position closest to grid 4a is smaller than the size of grid 4a, but the size of the vortices formed at positions further away may be larger than the size of grid 4a. Although not shown in Figure 3, vortex generation also occurs behind the warp threads of the mesh.

[0029] To the left of the heat soaking means 4 in Figure 3, the fluid flowing through the channel 2 flows in an orderly manner at almost the same velocity. This is the state of so-called laminar flow. When the flow is laminar and there are no objects obstructing the flow in the channel, there is no mass transfer perpendicular to the direction of fluid flow, and therefore almost no heat transfer occurs. To the right of the heat soaking means 4 in Figure 3, the fluid flow after passing through the heat soaking means 4 becomes turbulent due to the presence of the grid 4a, and vortices are generated due to the velocity difference. In particular, when the fluid is a gas, the viscosity is lower than that of a liquid, so the velocity difference is easier to maintain and vortices are more likely to be generated. When vortices are generated, mass transfer occurs perpendicular to the direction of fluid flow, and therefore heat transfer by convection occurs perpendicular to the flow. Vortices generated downstream of the grid 4a disappear at a location further downstream from the grid 4a. After the vortices disappear, mass transfer perpendicular to the direction of fluid flow ceases again.

[0030] The vortex generation by grid 4a changes depending on the Reynolds number. The Reynolds number in grid 4a shown in Figure 3 is defined as a dimensionless number obtained by dividing the product of the fluid velocity and the diameter of grid 4a by the kinematic viscosity of the fluid. When the Reynolds number is less than 40, the vortices generated behind grid 4a are steady flow that does not change over time. When the Reynolds number exceeds 40, vortices are generated one after another and carried backward, as illustrated in Figure 3, creating a so-called Karman vortex street. This is a flow in which the flow changes regularly with a predetermined period. Furthermore, when the Reynolds number exceeds 500, the flow changes irregularly over time and becomes a so-called turbulent flow, which is also disturbed spatially. When turbulence occurs, the fluid is mixed violently, and heat exchange is promoted.

[0031] The heat equalization means 4 is effective not only in promoting heat transfer by convection but also in promoting heat transfer by conduction. As described above, the grid 4a is provided continuously in any direction perpendicular to the direction of fluid flow. For example, in a grid 4a composed of the mesh illustrated in Figure 3, heat transfer is possible within the heat equalization means 4 in a direction perpendicular to the direction of fluid flow due to heat conduction by the wires that make up the mesh. Heat moves not only from one part of the grid 4a to another, but also between the flow path 2 and the grid 4a, as shown by the long white arrow in Figure 3.

[0032] Next, the effects brought about by the heat equalization means 4 provided in the temperature sensor 1 according to the present invention will be explained. Figure 4 is a schematic diagram showing an example of the temperature distribution of a fluid flowing through the channel 2 of the temperature sensor 1 according to the present invention. In Figure 4, assuming that the temperature of the channel 2 is kept constant, the temperature distribution of the fluid when a fluid at a lower temperature than that temperature flows into the channel 2 is represented by a temperature difference ΔT with respect to the temperature of the channel 2. The left and right ends of the graph show the temperature of the inner wall of the channel 2, and the center shows the distribution of the temperature of the fluid flowing through the channel 2 with respect to the radial coordinate r. The center of the graph represents the temperature difference ΔT at the center of the channel 2.

[0033] Figure 4(a) shows the temperature distribution in the radial direction of the fluid flow path 2 just before it reaches the heat soaking means 4.2 The fluid flowing near the center is hardly affected by the temperature of channel 2, and therefore maintains the low temperature it had immediately after entering channel 2. The fluid flowing closer to the inner wall of channel 2 experiences heat transfer from channel 2 by conduction due to the temperature difference between channel 2 and the fluid, as shown by the short white arrows in Figure 3. interior wall At positions close to the inner wall of channel 2, the fluid velocity slows down due to frictional resistance, causing heat to accumulate in the fluid as it flows through channel 2. As a result, as shown in Figure 4(a), the temperature distribution of the fluid remains the same as the temperature of channel 2 at the point where it is in contact with the inner wall of channel 2, but the temperature decreases rapidly as it moves away from the inner wall of channel 2, resulting in a low and flat temperature distribution near the center.

[0034] Figure 4(b) shows the temperature distribution of the fluid immediately after passing through the heat equalization means 4. As described above, the grid 4a constituting the heat equalization means 4 allows for internal heat transfer by conduction. By continuing to contact the fluid having the temperature distribution shown in Figure 4(a), the temperature of the grid 4a near the channel 2 is heated to the same temperature as the channel 2. On the other hand, the temperature near the center of the grid 4a remains low. As a result, due to the temperature difference inside the grid 4a, heat is transferred by conduction from the outer periphery of the grid 4a towards the center, and the temperature of the grid 4a becomes higher than the temperature of the fluid in contact with the grid 4a. Then, heat is supplied from the high-temperature grid 4a to the low-temperature fluid passing through the subchannel 4b, which is the space between the grids 4a. As a result, as shown in Figure 4(b), the fluid's channel 2 interior wall The temperature distribution near the center is smoother compared to (a). Also, the temperature of the fluid near the center is slightly higher compared to (a).

[0035] Figure 4(c) shows the temperature distribution of the fluid after it has passed through the heat soaking means 4 and reached the temperature measuring means 3. As described above, the heat soaking means 4 promotes heat transfer by convection. In particular, when a Karman vortex street or turbulence is present, vortices are generated not only behind the grid 4a but also behind the subchannel 4b, as shown in Figure 3. As a result, from the state immediately after passing through the heat soaking means 4 until the vortices disappear and the flow returns to a steady flow, heat transfer by convection occurs in a direction perpendicular to the direction of fluid flow. Consequently, as shown in Figure 4(c), the temperature distribution when it reaches the temperature measuring means 3 becomes even smoother compared to (b). Also, the temperature of the fluid near the center becomes even higher compared to (b), and the temperature difference ΔT with the channel 2 becomes smaller.

[0036] The above description explains the operation and effect of the heat equalization means 4 when the fluid temperature is lower than the temperature of the flow path 2. Conversely, even when the fluid temperature is higher than the temperature of the flow path 2, the heat equalization means 4 in the present invention exhibits exactly the same operation and effect, except that the direction of heat transfer is reversed compared to the cases in Figures 3 and 4.

[0037] In a preferred embodiment of the present invention, the flow path 2 is equipped with a heating means. As described above, when handling gas while maintaining a temperature higher than room temperature in order to prevent liquefaction of the gas in the flow path, it is preferable that all components that come into contact with the gas, including the flow path 2, be equipped with a heating means to keep those components at a high temperature. However, some components may lack a heating means for reasons such as structural reasons.

[0038] The heating means provided in the flow path 2 can be, for example, a heater installed around the flow path 2. Alternatively, an insulating material may be provided to cover the flow path 2 instead of a heater, or both a heater and an insulating material may be provided.

[0039] In a preferred embodiment of the present invention, the grid 4a is composed of a mesh 4c woven from wires made of metal or an alloy. Figure 5 is a schematic diagram showing an embodiment of the heat equalization means 4 provided in the temperature sensor 1 according to the present invention, illustrating a front view (a) and a side view (b) of the heat equalization means 4 composed of the mesh 4c. The annular member 4f shown in Figure 5 will be described later. Wires made of metal or an alloy are preferred as components of the heat equalization means 4 because they have excellent thermal conductivity and sufficient strength even when thin. It is preferable to use a metal or alloy that does not corrode when in contact with fluid and has excellent thermal conductivity as the metal or alloy that constitutes the mesh 4c. Specifically, wires made of gold, nickel, stainless steel, etc., can be used.

[0040] Plain weave and other known weaving methods can be used for the mesh 4c. In a mesh 4c woven with wires, heat transfer by conduction is possible at the points where the wires are in contact with each other, so the mesh 4c is provided continuously throughout the entire heat distribution means 4. Therefore, it can be said that the grid 4a composed of mesh 4c is provided continuously in any direction perpendicular to the direction of fluid flow. To make heat conduction more reliable, the contact points between wires may be firmly connected by means of diffusion bonding, welding, or brazing. Alternatively, multiple meshes 4c may be stacked in the thickness direction to form the grid 4a.

[0041] The diameter of the wires constituting mesh 4c can be determined by considering the Reynolds number and heat conduction described above. For example, if the gas flow rate is 5.0 standard liters per minute and the diameter of the flow path 2 is 8.0 mm, a wire diameter of 0.20 mm or more ensures the cross-sectional area necessary for heat conduction and promotes vortex generation. A wire diameter of 2.0 mm or less ensures the mesh opening of mesh 4c and the number of wires per unit cross-sectional area of ​​the flow path 2. Therefore, a wire diameter of 0.20 mm or more and 2.0 mm or less is preferable for the above flow rates. A more preferable wire diameter is 0.50 mm or more and 1.5 mm or less.

[0042] When the mesh opening of the mesh 4c, i.e., the spacing between the grid 4a, is 0.10 mm or more, the size of the subchannel 4b can be ensured and pressure loss can be reduced. When the mesh opening of the mesh 4c is 1.0 mm or less, vortex generation can be promoted. Therefore, a mesh opening of 0.10 mm or more and 1.0 mm or less is preferable. A more preferable mesh opening is 0.2 mm or more and 0.8 mm or less.

[0043] Preferably, the grid 4a, which is composed of mesh 4c, and the channel 2 are fixed together so that heat from the channel 2 is easily conducted to the grid 4a. This facilitates the flow of heat from the channel 2 to the grid 4a or vice versa, as shown by the long white arrow in Figure 3, resulting in a more uniform temperature distribution of the fluid.

[0044] In a preferred embodiment of the present invention, the grid 4a is composed of a porous body 4d made of metal or an alloy. Figure 6 is a schematic diagram showing another embodiment of the heat equalization means 4 provided in the temperature sensor 1 according to the present invention, illustrating a front view (a) and a side view (b) of the heat equalization means 4 composed of the porous body 4d. The porous body 4d made of metal or an alloy can be obtained, for example, by sintering granular material made of metal or an alloy, but the method of manufacturing the porous body 4d is not limited to sintering, and the porous body 4d can be manufactured by various methods. The porous body 4d made of metal or an alloy has excellent thermal conductivity and sufficient strength, making it a preferred component for the heat equalization means 4. As the metal or alloy constituting the porous body 4d, it is preferable to use one that does not corrode even when in contact with fluid and has excellent thermal conductivity. Specifically, stainless steel can be used.

[0045] In the porous body 4d obtained by sintering granular material made of metal or alloy, heat transfer by conduction is possible through the sintered necks formed at the points where the granular material comes into contact with each other. Therefore, the porous body 4d is provided continuously throughout the entire heat-sensing means 4. Accordingly, it can be said that the grid 4a composed of the porous body 4d is provided continuously in any direction perpendicular to the direction of fluid flow. Furthermore, by adjusting the size of the granular material and the degree of sintering, continuous subchannels 4b can be formed inside the porous body 4d. Multiple subchannels 4b penetrate from one side to the other of the porous body 4d, merging and branching again inside the heat-sensing means 4. The shape of the granular material constituting the porous body 4d is irregular, and its surface is rougher than that of wire, so when the porous body 4d is used as a heat-sensing means 4, it is easy to generate fluid turbulence.

[0046] When the diameter of the granular particles constituting the porous body 4d is 200 μm or more, the mesh opening of the porous body 4d can be ensured, and the generation of vortices can be promoted. When the diameter of the granular particles is 500 μm or less, the contact area between the granular particles necessary for heat conduction can be ensured. Therefore, the diameter of the granular particles is preferably 200 μm or more and 500 μm or less. A more preferable diameter for the granular particles is 250 μm or more and 400 μm or less. As with the case of mesh 4c, it is preferable that the grid 4a composed of the porous body 4d and the flow channel 2 are fixed so that heat from the flow channel 2 is easily conducted to the grid 4a.

[0047] In a preferred embodiment of the present invention, the grid 4a is made of perforated metal made of a metal or alloy. As is well known to those skilled in the art, perforated metal is a flat metal plate with a plurality of through holes. Figure 7 is a schematic diagram showing two embodiments of a heat equalization means 4 made of perforated metal 4e. (a) and (b) are front and side views of a heat equalization means 4 equipped with an annular member 4f, which will be described later, and (c) and (d) are front and side views of a heat equalization means 4 without an annular member 4f. Perforated metal made of a metal or alloy has excellent thermal conductivity and sufficient strength even when thin, making it a preferred material for the heat equalization means 4. Furthermore, as shown in (c) and (d), by not drilling through holes in the peripheral portion (shaded portion) of the perforated metal 4e, it is also possible to make the peripheral portion of the perforated metal 4e function as an annular member 4f. It is preferable to use a metal or alloy that does not corrode when in contact with fluid and has excellent thermal conductivity as the metal or alloy that constitutes the perforated metal 4e. Specifically, a flat plate made of gold, nickel, stainless steel, or other material with multiple through-holes can be used.

[0048] In the perforated metal 4e, heat transfer by conduction is possible throughout the entire surface except for the areas where through-holes are drilled; therefore, the perforated metal 4e is provided continuously throughout the entire heat uniforming means 4. Accordingly, it can be said that the grid 4a, composed of perforated metal 4e, is provided continuously in any direction perpendicular to the direction of fluid flow. Multiple sheets of perforated metal 4e may be stacked in the thickness direction to form the grid 4a.

[0049] The specific configuration of the perforated metal 4e, such as the spacing (pitch) between through-holes, the number of through-holes per unit area, and the size of each through-hole, can be determined as appropriate, taking into consideration, for example, securing the cross-sectional area necessary for heat conduction, promoting the generation of vortices downstream, and suppressing an excessive rise in pressure loss. It is preferable that the grid 4a and the flow path 2, which are composed of the perforated metal 4e, are fixed so that heat from the flow path 2 is easily conducted to the grid 4a. This facilitates the flow of heat from the flow path 2 to the grid 4a or vice versa, as shown by the long white arrow in Figure 3, resulting in a more uniform temperature distribution of the fluid.

[0050] In a preferred embodiment of the present invention, the heat equalization means 4 includes an annular member 4f that obstructs the flow of fluid near the inner wall of the flow channel 2. The heat equalization means 4, which is composed of a mesh 4c as illustrated in Figure 5, is provided with an annular member 4f around the mesh 4c. The annular member 4f can be, for example, a donut-shaped member made of a flat plate made of metal or an alloy and having a through hole formed in the center. The connection between the mesh 4c and the annular member 4f can be achieved, for example, by preparing two annular members 4f having the same shape and fixing the mesh 4c between them. When the heat equalization means 4 is provided with an annular member 4f, the transfer of heat from the flow channel 2 to the grid 4a will occur via the annular member 4f. Therefore, it is preferable that the grid 4a, which is composed of a mesh 4c or the like, and the annular member 4f provided around it are fixed together in such a way that heat transfer between them is easy.

[0051] As shown in Figure 3, the annular member 4f in the heating means 4 has the effect of obstructing the flow of fluid near the inner wall of the flow path 2. The fluid flow obstructed by the annular member 4f flows out downstream through the sub-flow path 4b closest to the annular member 4f. As a result, the fluid that has been heated or cooled while flowing near the inner wall of the flow path 2 changes its direction of flow significantly while flowing through the flow path 2It is mixed with the fluid flowing near the center. As a result, the unevenness in the temperature distribution of the fluid is reduced. In any of the embodiments of the heat equalization means 4 described above, such as the mesh 4c, porous body 4d, and perforated metal 4e, an annular member 4f can be provided.

[0052] Furthermore, as shown in Figure 3, at least a portion of the fluid that has passed through the through-hole of the annular member 4f flows through a channel behind the annular member 4f, from the through-hole of the annular member 4f. 2 This creates a large vortex that spreads outward in the radial direction and curves around the annular member 4f. As a result, the fluid flowing near the inner wall of the channel 2 is stirred again, further reducing the unevenness in the fluid's temperature distribution.

[0053] In a preferred embodiment of the present invention, the temperature sensor 1 includes a second temperature measuring means 5 having a temperature measuring point located inside the flow path 2, but not at the center. In this embodiment, the original temperature measuring means will be referred to as the first temperature measuring means 3 in order to distinguish it from the second temperature measuring means 5. As illustrated in Figure 1, the temperature measuring point 3a of the first temperature measuring means 3 and the temperature measuring point 5a of the second temperature measuring means 5 are both located on the same plane perpendicular to the direction of fluid flow. In this configuration, the first temperature measuring means 3 and the second temperature measuring means 5 are located at the same position in the flow path 2, as shown in Figure 1. 1 The temperature of the fluid is measured at two different locations on the same plane perpendicular to the direction of fluid flow, as illustrated in the example. This allows for a more accurate determination of the fluid temperature by inferring the temperature distribution as illustrated in Figure 4.

[0054] In another embodiment, the present invention relates to a mass flow meter 7 comprising a temperature sensor 1 according to the present invention and a flow sensor 6 for measuring the flow rate of a fluid flowing through a flow path 2, wherein the flow sensor 7 corrects the flow rate measurement of the fluid measured by the flow sensor 6 using the fluid temperature measurement value measured by the temperature sensor 1. Because the temperature sensor 1 according to the present invention can accurately measure the temperature of the fluid, a mass flow meter 7 that can perform flow rate measurement with higher accuracy than conventional methods can be realized. The flow sensor 6 can be configured as a known thermal flow sensor, for example, as shown in Figure 1, including a branch pipe 6a that branches off from the flow path 2 and then rejoins, a set of temperature measuring elements 6b provided in the branch pipe 6a, and a bypass 6c provided in the flow path 2. As the flow sensor 6 is a known flow sensor, in addition to a thermal flow sensor, other known flow sensors such as a pressure flow sensor can be used, as long as they do not hinder the effects of the present invention.

[0055] In yet another embodiment, the present invention relates to a mass flow control device 8 comprising a mass flow meter 7 according to the present invention, a flow control valve for controlling the flow rate of fluid flowing through a flow path 2, and a control unit that provides a control signal to the flow control valve so that the fluid flow rate measurement value measured by the mass flow meter 7 becomes a predetermined target value. By using the flow rate measurement value provided by the mass flow meter 7 according to the present invention, a mass flow control device 8 that can perform flow rate control with higher accuracy than conventional methods can be realized. [Examples]

[0056] The effects of the present invention will be illustrated below using examples. First, as an embodiment of the present invention, a temperature sensor 1 was prepared, as shown in Figure 8, which includes a flow path 2, a first temperature measuring means 3, and a heat soaking means 4. The temperature sensor 1 shown in Figure 8 has the same configuration as the temperature sensor 1 shown in Figure 1, except that it does not include a flow sensor 6. As the first temperature measuring means 3, a sheath-type temperature sensor with an outer diameter of 1.2 mm and a built-in Alumel-Chromel thermocouple was used. The position of the temperature measuring point 3a of the first temperature measuring means 3 was set to the center of the flow path 2 (first temperature measuring point) (see the black circle in the figure). The error in the position of the actual first temperature measuring point relative to the target center of the flow path 2 was within ±1.0 mm. Furthermore, in order to eliminate heat conduction from the flow path 2, the base of the first temperature measuring means 3 was fixed to the closed end of a pipe (branch pipe 2a) that branched off from the flow path 2.

[0057] The heat uniforming means 4 used was constructed using the mesh 4c shown in Figure 5. The mesh 4c was made of plain-woven stainless steel wire with a diameter of 0.8 mm. The distance between the central axes of the steel wires was 1.8 mm. The inner diameter of the annular member 4f that fixed the mesh 4c was 11.2 mm. The distance between the position of the heat uniforming means 4 and the position of the first temperature measuring means 3 on the central axis of the flow path 2 was 36.8 mm.

[0058] Nitrogen gas with an absolute pressure of 0.12 MPa and a gauge pressure of 0.02 MPa was supplied from a nitrogen gas cylinder (not shown) to the inlet of a gas heating heater 9 via a mass flow control device (MFC) 8 at a flow rate of 6.0 standard liters per minute (slm). Nitrogen gas with a flow pressure of 0.1 MPa at the outlet of the gas heating heater 9 was supplied to the upstream side of the flow path 2. A gas heating heater (model number: WEX-S1-2U) manufactured by Watty Co., Ltd. was used as the gas heating heater 9. The gas heating heater 9 was set to a temperature of 150°C, and at the same time that the heating of the nitrogen gas was started, temperature measurement by the first temperature measuring means 3 was started and continued for approximately 30 minutes.

[0059] Next, the power to the gas heating heater 9 was turned off, and after waiting for the flow path 2 to cool to room temperature, the supply of nitrogen gas was stopped. The position of the temperature measuring point of the sheath-type temperature sensor was changed to a position shifted 3.0 mm outward from the center of the flow path (second temperature measuring point 5a), thereby configuring the second temperature measuring means 5 (see the white circle in the figure). Then, under the same conditions as the temperature measurement by the first temperature measuring means 3 described above, the measurement was continued for approximately 30 minutes. The results of these two temperature measurements are shown in the solid line graph in Figure 9.

[0060] On the other hand, as a comparative example, a temperature sensor was used which was obtained by removing only the heat soaking means 4 from the temperature sensor 1 of the above-described embodiment, and temperature measurements at the first and second temperature measurement points described above were continued for approximately 30 minutes each. The results of these two temperature measurements are shown in the dashed graph of Figure 9.

[0061] According to the data for the examples and comparative examples shown in Figure 9, the temperature of the nitrogen gas rises rapidly from the start of temperature measurement, and the temperature rise slows down somewhat after about 2.5 minutes. This is because the temperature of the gas heating heater 9 has reached the set temperature of 150°C. Comparing the temperature at the first temperature measurement point 3a (center of the flow path 2) and the temperature at the second temperature measurement point 5a (3.0 mm from the center) thereafter, in the comparative example without the heat equalization means 4, the temperature difference between the two exceeds approximately 20°C, whereas in the example with the heat equalization means 4, the temperature difference remains at approximately 15°C.

[0062] From this data, it can be seen that in the temperature sensor 1 equipped with the heat equalization means 4 according to the present invention, the temperature at the first temperature measurement point 3a (center of the flow path 2) becomes lower, and at the same time, the temperature at the second temperature measurement point 5a (3.0 mm from the center) becomes higher, resulting in a more uniform radial temperature distribution in the flow path than in the prior art.

[0063] Considering the operation of the heat soaking means 4, which is composed of mesh 4c in the embodiment, the diameter of the steel wire constituting the mesh 4c is 0.8 mm. Based on the viscosity, density, and flow velocity of the nitrogen gas, the Reynolds number, with the diameter of the steel wire as the representative length under the conditions of the embodiment, is estimated to be approximately 69. Since this value is greater than 40 and less than 500, it can be inferred that although turbulence does not occur downstream of the heat soaking means 4, a Karman vortex street is generated. A Karman vortex street is a flow that changes regularly with a predetermined period. As a result, a component is generated in the nitrogen gas flow in a direction perpendicular to the central axis of the flow path 2 (radial direction of the flow path 2), and mass transfer occurs in that direction. As a result, heat transfer by convection occurs in the direction perpendicular to the flow, and it is thought that the temperature distribution becomes uniform.

[0064] Furthermore, when the temperature outside the channel 2, where the heat uniforming means 4 is provided in the embodiment, was measured along with the temperature measurements at the first temperature measurement point 3a and the second temperature measurement point 5a described above, it was found that the temperature was 2 to 3°C higher than in the comparative example where the heat uniforming means 4 is not provided. This fact suggests that the mesh 4c constituting the heat uniforming means 4 acts as a heat medium (conductor), bringing about heat transfer by conduction in the radial direction of the channel 2. In other words, it is suggested that the heat uniforming means 4 according to the present invention is effective not only in promoting heat transfer by convection as described above, but also in heat transfer by conduction.

[0065] In the above-described embodiment, the same temperature sensor was used for both the first measuring means 3 and the second measuring means 5. However, naturally, in a preferred embodiment of the present invention, the first measuring means 3 and the second measuring means 5 can each be configured with separate temperature sensors. In this preferred embodiment, the temperature of the fluid at the first temperature measurement point 3a and the second temperature measurement point 5a can be measured simultaneously. Even if the effect of uniformizing the temperature distribution by the heat soaking means 4 is insufficient, as described above, the temperature of the fluid can be more accurately determined by estimating the temperature distribution in the radial direction illustrated in Figure 4. [Explanation of Symbols]

[0066] 1. Temperature sensor 2 channels 2a Branch piping 3 Temperature measurement means (first temperature measurement means) 3a Temperature measurement point (1st temperature measurement point) 3b Protection tube 3c base 3D connector 4 Heating means 4a grid 4b Sub-channel 4c mesh 4d porous body 4e Perforated Metal 4f Annular member 5 Second temperature measuring means 5a Temperature measurement point (second temperature measurement point) 6 Flow Sensor 6a Branch pipe 6b Temperature measuring element 6c Bypass 7 Mass flow meter 8 Mass Flow Controller (MFC) 9. Gas heating heater

Claims

1. A temperature sensor used in a mass flow meter, The system comprises a fluid channel through which a fluid flows, a temperature measuring means having a temperature measuring point at a predetermined position within the channel, and a heat equalization means provided upstream of the temperature measuring point within the channel, The heat equalization means comprises a grid continuously provided in any direction perpendicular to the direction of fluid flow, sub-channels divided by the grid, and annular members projecting from the inner wall of the channel toward the center of the cross-section of the channel and obstructing the flow of the fluid near the inner wall of the channel, thereby reducing the uneven distribution of the fluid temperature by generating turbulence or vortices of the fluid in a region downstream of the heat equalization means and upstream of the temperature measuring means. Temperature sensor.

2. A temperature sensor according to claim 1, The aforementioned grid is composed of a mesh woven from wires made of metal or alloy. Temperature sensor.

3. A temperature sensor according to claim 1, The aforementioned grid is composed of a porous body made of metal or alloy. Temperature sensor.

4. A temperature sensor according to claim 1, The aforementioned grid is made of perforated metal made of metal or an alloy. Temperature sensor.

5. A temperature sensor according to any one of claims 1 to 4, The temperature measuring means has a temperature measuring point at the center of the cross-section of the flow path. Temperature sensor.

6. A temperature sensor according to any one of claims 1 to 5, The system further comprises a second temperature measuring means having a temperature measuring point located inside the flow channel, but at a position other than the center of the cross-section of the flow channel, The temperature measuring point of the aforementioned temperature measuring means and the temperature measuring point of the second temperature measuring means are both on the same plane perpendicular to the direction of fluid flow. Temperature sensor.

7. A temperature sensor according to any one of claims 1 to 6, The aforementioned flow path is equipped with a heating means. Temperature sensor.

8. A temperature sensor according to any one of claims 1 to 7, and a flow sensor for measuring the flow rate of the fluid flowing through the channel, The temperature measurement of the fluid measured by the temperature measuring means is used to correct the flow rate measurement of the fluid measured by the flow sensor. Mass flow meter.

9. The device comprises a mass flow meter as described in claim 8, a flow control valve for controlling the flow rate of fluid flowing through the flow path, and a control unit that provides a control signal to the flow control valve so that the measured fluid flow rate measured by the mass flow meter becomes a predetermined target value. Mass flow controller.

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