Temperature sensor, mass flow meter equipped with temperature sensor, and mass flow control device

Abstract

A temperature sensor for a mass flow meter includes: a flow path for fluid flow; a temperature measuring element having a temperature measuring point at the center of the cross-section of the flow path; and a heat-spreading element located upstream of the temperature measuring point in the flow path. The heat-spreading element includes: a grid continuously arranged in any direction perpendicular to the direction of fluid flow; and a secondary flow path divided by the grid. Thus, a temperature sensor can be implemented that can obtain a temperature measurement value representing the temperature of the fluid even when the temperature of the fluid supplied to the mass flow meter from the outside changes.

Description

Technical Field

[0001] This invention relates to a temperature sensor for use in a mass flow meter. Background Technology

[0002] A mass flow control device is a device that includes a mass flow meter and a flow control valve, and controls the opening of the flow control valve so that the mass flow rate of the fluid measured by the mass flow meter matches a predetermined target value. Mass flow control devices are widely used for the purpose of quantitatively supplying gases used in the manufacturing processes of semiconductor manufacturing equipment. In recent years, various gases have been used with the advancement of semiconductor manufacturing technology. Among these gases, for example, there are gases that must be processed while maintaining a temperature higher than room temperature to prevent liquefaction within the flow path.

[0003] The volume and pressure of a gas can vary significantly with temperature. Therefore, in a mass flow control device, it is preferable to accurately measure the temperature of the gas flowing inside the device in order to supply gas with high precision. Conventional mass flow control devices include those equipped with temperature sensors for the purpose of measuring gas temperature. For example, Patent Documents 1 and 2 describe inventions of mass flow control devices with temperature sensors installed inside or on the surface of the main body, and Patent Document 3 describes an invention of a mass flow control device with a temperature sensor mounted facing the flow path within the main body.

[0004] Furthermore, compared to solids and liquids, gases have a very small heat capacity per unit volume. Therefore, when the temperature of the flow path inside the mass flow control device differs from the temperature of the gas it contacts, heat exchange occurs between them, posing a risk of temperature fluctuations for gases with low heat capacity. Conventional mass flow control devices utilize a metal block to cover the main body (base) and flow sensor, and a heater within the block maintains the overall temperature of the gas flow path at a high temperature (see, for example, Patent Document 4). Using such a mass flow control device ensures that the temperature of the gas flowing inside is the same as the temperature of the inner wall of the flow path it contacts, thus enabling a stable and quantitative supply of gases that readily liquefy at room temperature.

[0005] Existing technical documents

[0006] Patent documents

[0007] Patent Document 1: Japanese Patent Application Publication No. 7-230322

[0008] Patent Document 2: Japanese Patent Application Publication No. 2020-123065

[0009] Patent Document 3: Japanese Patent Application Publication No. 8-63235

[0010] Patent Document 4: International Publication No. 2015 / 141437 Summary of the Invention

[0011] The problem the invention aims to solve

[0012] However, in reality, gas temperatures can change for various reasons. As gas temperature changes, so do its volume and pressure; therefore, the flow rate controlled by the mass flow control device may sometimes deviate from the target value. Therefore, it is preferable to immediately detect and adjust the flow rate when the temperature of the externally supplied gas changes. However, in the aforementioned prior art mass flow control devices, since a temperature sensor is installed in the flow path inside the main body block with a large heat capacity, it is difficult to ensure that the temperature sensor output immediately corresponds to the changed gas temperature even if the gas temperature changes.

[0013] Therefore, it is conceivable to place a temperature sensor with a small heat capacity that is insulated from the main body inside the gas flow path of the mass flow control device. However, in this case, the temperature at the location of the temperature sensor's measuring point may not accurately reflect the temperature of the gas supplied to the mass flow control device. For example, when the cross-section of the flow path is circular, the gas flowing near the inner wall of the flow path is easily affected by the temperature difference between itself and the inner wall, resulting in temperature changes. In contrast, the gas flowing near the center of the flow path is essentially unaffected by the temperature of the inner wall. Therefore, even if the temperature at the measuring point near the center of the flow path is measured to avoid the influence of heat from the main body, it cannot be said that the measured value represents the overall temperature of the gas flowing in the flow path (e.g., the average temperature of the gas across the entire cross-section of the flow path). The same problem arises when the temperature of the gas supplied to the mass flow control device is constant, but the temperature of the gas flow path within the mass flow control device changes.

[0014] The present invention was made in view of the above-mentioned problems, and its object is to obtain a temperature measurement value representing the overall temperature of the fluid supplied from the outside to the mass flow control device, and to use the temperature measurement value to improve the accuracy of flow control.

[0015] Solution for solving the problem

[0016] The present invention provides a temperature sensor for use in a mass flow meter, wherein the temperature sensor comprises: a flow path for fluid flow; a temperature measuring element having a temperature measuring point at a predetermined position inside the flow path; and a heat equalization element disposed in the flow path upstream of the temperature measuring point, the heat equalization element comprising: a grid continuously arranged in any direction perpendicular to the direction of fluid flow; and a secondary flow path divided by the grid.

[0017] In the temperature sensor equipped with the structure of the present invention, vortices of fluid are generated on the downstream side of the grid, causing convection-based thermal movement. Additionally, thermal movement also occurs through conduction within the continuous grid and between the fluid flowing in the secondary flow path and the grid. Due to these effects of the heat-spreading member, fluid with a more uniform temperature distribution within the flow path reaches the downstream temperature sensing element compared to the case without a heat-spreading member.

[0018] In a preferred embodiment of the temperature sensor of the present invention, the flow path includes a heating element. In other embodiments, the present invention is an invention of a mass flow meter or mass flow control device incorporating the above-described temperature sensor.

[0019] The effects of the invention

[0020] The temperature sensor of this invention enables the acquisition of a temperature measurement value representing the overall temperature of the fluid flowing in the flow path. By using the acquired temperature measurement value, the flow rate measurement value of the fluid flowing in the flow path can be more appropriately corrected compared to the prior art, or the flow rate can be controlled with higher accuracy using the corrected flow rate measurement value. Attached Figure Description

[0021] Figure 1 This is a cross-sectional view showing an example of a mass flow meter equipped with the temperature sensor of the present invention.

[0022] Figure 2 This is a schematic diagram representing a cylindrical coordinate system that can be applied to the flow path.

[0023] Figure 3 This is a cross-sectional view illustrating the function of the heat dissipation component in the temperature sensor of the present invention.

[0024] Figure 4 This is a schematic diagram illustrating an example of the temperature distribution of a fluid flowing in the flow path of the temperature sensor of the present invention.

[0025] Figure 5 This is a schematic diagram illustrating an embodiment of the heat dissipation component included in the temperature sensor of the present invention.

[0026] Figure 6 This is a schematic diagram illustrating another embodiment of the heat dissipation component included in the temperature sensor of the present invention.

[0027] Figure 7 This is a schematic diagram illustrating another embodiment of the heat dissipation component included in the temperature sensor of the present invention.

[0028] Figure 8 This is a cross-sectional view showing the structure of a temperature sensor according to an embodiment of the present invention.

[0029] Figure 9 This is a graph showing the temperature measurement results at the first and second temperature measuring points of the temperature sensor based on the embodiments of the present invention and the temperature sensor of the comparative example. Detailed Implementation

[0030] Hereinafter, specific embodiments of the present invention will be described with reference to the accompanying drawings. Furthermore, the present invention is not limited to the embodiments described below. The present invention can be practiced in any manner without departing from the scope of the technical concept set forth in the appended specification, claims, and drawings.

[0031] The temperature sensor of the present invention is a temperature sensor for a mass flow meter, which includes a flow path, a temperature measuring component, and a heat dissipation component. Figure 1 This is a schematic diagram illustrating an example of a mass flow meter 7 equipped with the temperature sensor 1 of the present invention. The flow path 2 is a component through which fluid flows. The flow path 2 can be as follows: Figure 1 It can be constructed from a tube of predetermined thickness as illustrated, or it can be constructed from a perforated block-shaped body. The cross-section of the inner side of flow path 2 can be circular or other shapes. Figure 1 In the illustrated mass flow meter 7, the flow path 2 is composed of a straight cylinder with a certain diameter. A dashed line passing through the center of the flow path 2 represents its central axis. Figure 1 The image depicts a cross-section of the mass flow meter 7 cut by a surface containing the central axis. Figure 1 The hollow arrow indicates the direction of fluid flow inside flow path 2.

[0032] The temperature sensor 1 of the present invention includes a temperature measuring element 3 that measures the temperature of a fluid flowing in a flow path 2. The temperature measuring element 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 within the temperature measuring element 3 where the temperature of the fluid is measured. The temperature measuring element 3 continuously and precisely observes the constantly changing temperature of the fluid flowing in the flow path 2 at the temperature measuring point 3a fixed to the flow path 2. Because the temperature measuring element 3 measures the fluid temperature at a precise position, even if there is a deviation in the temperature distribution of the fluid within the flow path, the temperature measurement value obtained by the temperature measuring element 3 will not directly represent the overall temperature of the fluid. The overall temperature of the fluid refers to, for example, the average temperature of the gas across the entire cross-section of the flow path, as described above.

[0033] As will be detailed later, in the temperature sensor 1 of the present invention, the temperature distribution of the fluid in the radial direction of the flow path is made more uniform by the heat-spreading member 4. Therefore, even when the temperature measuring point 3a is located outside the center of the cross-section of the flow path 2, a temperature measurement value that is closer to the overall temperature of the fluid flowing in the flow path can be obtained compared with the prior art temperature sensor that does not have the heat-spreading member 4. From this point of view, the temperature measuring member 3 can have a temperature measuring point 3a at a predetermined position inside the flow path 2. In addition, as will be described later, multiple temperature measuring points can be provided in the temperature sensor 1 of the present invention.

[0034] In a preferred embodiment of the present invention, such as Figure 1 As illustrated, the temperature measuring point 3a is located at the center of the cross-section of the flow path 2, that is, near the central axis of the flow path 2. In this invention, "the center of the cross-section of the flow path" means a position near the central axis of the flow path 2, because it is far from the inner wall of the flow path 2 and therefore less susceptible to the effects of temperature changes in the flow path 2. For example, "the center of the cross-section of the flow path" can be defined as the area containing the possible positional error that might occur if the temperature measuring point were to be positioned on the central axis of the flow path 2. Therefore, the position of the temperature measuring point 3a does not need to be exactly the same as the position of the central axis of the flow path 2. Figure 1 The temperature sensor shown has a measuring point 3a located near the top of the protective tube 3b. The protective tube 3b is fixed to the flow path 2 such that the measuring point 3a is located at the center of the flow path 2.

[0035] Because the protective tube 3b is thinner and has a smaller cross-sectional area, heat from the flow path 2 is less likely to be conducted to the temperature measuring point 3a. That is, the flow path 2 and the temperature measuring point 3a of the temperature measuring component 3 are thermally separated. Therefore, the temperature measuring component 3 can measure the fluid temperature 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 the heat capacity of the temperature measuring component 3 containing the temperature measuring point 3a small, the temperature of the fluid measured by the temperature measuring component 3 can be made consistent with the actual temperature change of the fluid in a short time.

[0036] The temperature information measured at the temperature measuring point 3a of the temperature measuring component 3 is converted into an electrical signal and transmitted to the base 3c through the lead wire inside the protective tube 3b. It is then transmitted to the outside of the temperature measuring component 3 via the connector 3d and a cable (not shown), and finally converted into a temperature measurement value. As a specific element housed in the protective tube 3b, known temperature measuring elements such as a temperature-sensing resistor, a thermistor, or a thermocouple can be used.

[0037] For ease of future explanation, please refer to [reference needed]. Figure 2 To illustrate the cylindrical coordinate system applicable to flow path 2 of this invention. Figure 2 In this context, O is the origin of the cylindrical coordinate system. The origin O can be set at... Figure 1 Any position on the central axis of the flow path 2 shown, such as the end of the upstream side of the flow path 2.

[0038] From the origin O towards Figure 2 The axis L extending to the right of the origin is called the cylindrical axis. The position of the cylindrical axis L coincides with the position of the central axis of flow path 2. The positive direction of the cylindrical axis L is the same as the direction from the upstream side to the downstream side of flow path 2. From the origin O... Figure 2 The axis A extending upwards from the cylindrical coordinate system is called the polar axis. The direction of the polar axis A is used to determine the reference direction in a plane perpendicular to the cylindrical axis L of the cylindrical coordinate system. The direction of the polar axis A is, for example, perpendicular to... Figure 1 It is determined by ensuring that the vertical direction is consistent. Furthermore, in Figure 1 In the example shown, the protective tube 3b is arranged in the vertical direction; therefore, the direction of the polar axis A is consistent with the direction in which the protective tube 3b is located. The positive direction of the polar axis A can, for example, be aligned with... Figure 1 It is determined in a consistent bottom-up direction.

[0039] In a cylindrical coordinate system, the position of any point P can be represented using three coordinates: r, θ, and z, as P(r, θ, z). r is called the radius vector, and it is the distance between point P'(r, θ, 0) obtained by projecting point P onto a plane containing the origin O and perpendicular to the cylinder axis L, and the origin O. θ is called the azimuth angle, and it is the angle between the polar axis A and the line segment OP'. z is called the height, and it is the distance between point P and the plane containing the origin O and perpendicular to the cylinder axis L.

[0040] Refer again to Figure 1 The temperature sensor 1 of the present invention includes a heat dissipation member 4, and the heat dissipation member 4 is provided at a position upstream of the temperature measurement point 3a in the flow path 2. The heat dissipation member 4 includes a lattice 4a (not shown) continuously provided in an arbitrary direction perpendicular to the direction of fluid flow and a sub-flow path 4b (not shown) divided by the lattice 4a. In the present invention, "lattice" refers to a periodically arranged partition member. At the heat dissipation member 4, the flow path 2 is divided into a plurality of sub-flow paths 4b by the lattice 4a. That is, the lattice 4a constitutes the wall of the sub-flow path 4b, and the space between the lattices 4a constitutes the sub-flow path 4b.

[0041] The flow of the fluid passing through the flow path 2 and reaching the heat dissipation member 4 is divided by the lattice 4a and branches into flows flowing inside the plurality of sub-flow paths 4b. The sub-flow path 4b connects the upstream side and the downstream side of the heat dissipation member 4. The sub-flow path 4b can connect the inlet on the upstream side and the outlet on the downstream side of the heat dissipation member 4 using a single flow path, or a plurality of sub-flow paths 4b can converge inside the heat dissipation member 4 and branch again. The fluid flowing out from the sub-flow path 4b loses the partition member and merges again as a whole to form the fluid in the flow path 2.

[0042] The lattice 4a is continuously provided in an arbitrary direction perpendicular to the direction of fluid flow. Refer to Figure 2 , the direction of fluid flow refers to the positive direction of the cylindrical axis L. An arbitrary direction perpendicular to the direction of fluid flow refers to the direction of the vector OP' in an arbitrary azimuth angle θ. That is, the lattice 4a is continuously provided in an arbitrary direction in the plane perpendicular to the direction of fluid flow. Here, in the present invention, the lattice 4a is "continuously provided" means that the members constituting the lattice 4a are provided without interruption throughout the entire heat dissipation member 4 except for the part of the sub-flow path 4b. The detailed embodiments of the lattice 4a will be described later.

[0043] Next, the function of the heat dissipation member 4 included in the temperature sensor 1 of the present invention will be described. Figure 3 It is a cross-sectional view showing the function of the heat dissipation member 4. Figure 3 The lattice 4a of the exemplified heat dissipation member 4 is composed of a net woven with wires. The circular cross-section near the center of Figure 3 represents the cross-section of the horizontal lines constituting the net. In addition, the dotted line extending in the vertical direction represents the position of the vertical lines constituting the net. The heat dissipation member 4 is composed of a flat-woven net continuously provided in an arbitrary direction perpendicular to the direction of fluid flow. The space between the lattices 4a constitutes the sub-flow path 4b.

[0044] The fluid flows from Figure 3The fluid flows from left to right in flow path 2. The fluid reaching the heat exchanger 4 branches into multiple secondary flow paths 4b and passes through the heat exchanger 4, then merges again. At this point, the fluid whose flow is obstructed by grid 4a flows around to a position equivalent to the rear of grid 4a when viewed from the upstream side of flow path 2, forming vortices. The size of the vortex generated at the position closest to grid 4a is smaller than the size of grid 4a, but the size of the vortex formed at positions farther from that position is sometimes larger than the size of grid 4a. Although in Figure 3 It is not shown in the diagram, but vortices are also generated behind the longitudinal lines of the net.

[0045] exist Figure 3 Positioned to the left of the heat equalization component 4, the fluid flowing in flow path 2 moves uniformly at approximately the same velocity. This is known as laminar flow. In laminar flow, where there are no obstructions in the flow path, matter does not move in directions perpendicular to the fluid flow direction; therefore, there is essentially no thermal movement. Figure 3 The fluid flow after passing through the heat exchanger 4 is turbulent due to the presence of grid 4a at the right side of the heat exchanger 4, generating vortices caused by velocity differences. In particular, when the fluid is a gas, the lower viscosity of the gas compared to the liquid makes it easier to maintain a velocity difference and generate vortices. When vortices are generated, matter moves in a direction perpendicular to the fluid flow direction, resulting in convection-based thermal movement in this direction. The vortices generated downstream of grid 4a disappear at the point where they leave grid 4a downstream. After the vortices disappear, the movement of matter in the direction perpendicular to the fluid flow direction also disappears.

[0046] The generation of vortices based on lattice 4a varies with the Reynolds number. Figure 3 The Reynolds number of the lattice 4a shown is defined as a dimensionless number obtained by dividing the product of the fluid velocity and the diameter of lattice 4a by the dynamic viscosity of the fluid. When the Reynolds number is less than 40, the vortices generated behind lattice 4a represent a steady flow that does not change with time. When the Reynolds number exceeds 40, as... Figure 3 As illustrated, vortices are generated successively and flow backward, creating what is known as a Karman vortex street. This is a flow that changes regularly with a predetermined period. Furthermore, when the Reynolds number exceeds 500, the flow becomes what is known as turbulent flow, which varies irregularly in time and is also disordered in space. When turbulence occurs, the fluid mixes violently, promoting heat exchange.

[0047] The heat spreader 4 not only promotes convection-based heat transfer but is also effective for conduction-based heat transfer. As described above, the lattice 4a is continuously arranged in any direction perpendicular to the direction of fluid flow. For example, in a system composed of… Figure 3At the lattice 4a of the illustrated mesh, thermal movement can occur within the heat-equalizing component 4 in a direction perpendicular to the fluid flow direction due to heat conduction based on the lines constituting the mesh. Heat not only moves from one part of the lattice 4a to other parts, but also... Figure 3 As shown by the hollow long arrow, heat also moves between flow path 2 and grid 4a.

[0048] Next, the effects of the heat dissipation component 4 provided by the temperature sensor 1 of the present invention will be explained. Figure 4 This is a schematic diagram illustrating an example of the temperature distribution of a fluid flowing in the flow path 2 of the temperature sensor 1 of the present invention. Figure 4 In this diagram, assuming the temperature of flow path 2 is kept constant, the temperature distribution of fluid flowing into flow path 2 at a lower temperature, ΔT, is used as a reference temperature. The left and right ends of the graph represent the temperature of the inner wall of flow path 2, while the central part represents the temperature distribution of the fluid flowing in flow path 2 relative to the radial coordinate r. The center of the graph represents the temperature difference ΔT at the center of flow path 2.

[0049] Figure 4 (a) represents the temperature distribution of the fluid about to reach the heat spreader 4 in the radial direction of the flow path 2. The fluid flowing near the center of the flow path 2 is essentially unaffected by the temperature of the flow path 2, thus maintaining a relatively low temperature immediately after entering the flow path 2. In the fluid flowing near the inner wall of the flow path 2, such as... Figure 3 As shown by the hollow short arrow, heat moves from flow path 2 through conduction due to the temperature difference between flow path 2 and the fluid. Near the inner wall of flow path 2, the fluid velocity slows down due to frictional resistance; therefore, heat accumulates in the fluid during its flow in flow path 2. The result is as follows: Figure 4 As shown in (a), for the temperature distribution of the fluid, at the position in contact with the inner wall of the flow path 2, the temperature of the fluid is the same as the temperature of the flow path 2. As it moves away from the inner wall of the flow path 2, the temperature drops rapidly. Near the center, the temperature of the fluid is lower, resulting in a flat temperature distribution.

[0050] Figure 4 (b) represents the temperature distribution of the fluid immediately after passing through the heat exchanger 4. As described above, the lattice 4a constituting the heat exchanger 4 is capable of generating internal thermal movement based on conduction. This is achieved through interaction with... Figure 4The fluids in the temperature distribution shown in (a) remain in continuous contact, thereby heating the temperature of the location in grid 4a near flow path 2 to the same temperature as flow path 2. On the other hand, the temperature near the center of grid 4a remains lower. Thus, due to the temperature difference within grid 4a, heat transfer based on conduction occurs from the outer periphery of grid 4a towards the center, resulting in a temperature of grid 4a higher than that of the fluid in contact with it. Therefore, heat is supplied from the high-temperature grid 4a towards the low-temperature fluid through the secondary flow path 4b, which serves as the space between grids 4a. As a result, as... Figure 4 As shown in (b), with Figure 4 Compared to (a), the temperature distribution of the fluid near the inner wall of flow path 2 becomes more gradual. Additionally, compared to... Figure 4 Compared to (a), the temperature of the fluid near the center is slightly higher.

[0051] Figure 4 (c) represents the temperature distribution of the fluid as it reaches the temperature measuring element 3 after passing through the heat spreader 4. As mentioned above, the heat spreader 4 promotes convection-based thermal movement. In particular, it facilitates the generation of Karman vortex streets or turbulence, such as... Figure 3 As shown, vortices are generated not only behind grid 4a but also behind the secondary flow path 4b. Consequently, during the period from the state immediately after passing the heat exchanger 4 until the vortices disappear and the flow returns to steady flow, convection-based thermal movement occurs in a direction perpendicular to the direction of fluid flow. The result is as follows: Figure 4 As shown in (c), with Figure 4 Compared to (b), the temperature distribution reaching the temperature measuring element 3 becomes evenly distributed. Furthermore, compared to... Figure 4 Compared to (b), the temperature of the fluid near the center becomes even higher, and the temperature difference ΔT between the fluid and flow path 2 becomes smaller.

[0052] The above description explains the function and effect of the heat spreader 4 when the fluid temperature is lower than the temperature of the flow path 2. For the heat spreader 4 of this invention, even when the fluid temperature is higher than the temperature of the flow path 2, the direction of heat transfer is only opposite to... Figure 3 and Figure 4 In the opposite case, it will have the exact same effect.

[0053] In a preferred embodiment of the invention, the flow path 2 includes a heating element. As described above, when processing gas while maintaining a temperature higher than room temperature to prevent liquefaction of the gas within the flow path, it is preferable to keep all components in contact with the gas, represented by the flow path 2, at a high temperature by including heating elements. However, due to reasons such as structural design, some components may lack heating elements.

[0054] The heating element in flow path 2 can be, for example, a heater disposed around flow path 2. Alternatively, instead of a heater, an insulating material covering flow path 2 can be provided, or both a heater and an insulating material can be provided.

[0055] In a preferred embodiment of the invention, the grid 4a is composed of a mesh 4c woven from threads made of metal or alloy. Figure 5 This is a schematic diagram illustrating an embodiment of the heat-spreading component 4 included in the temperature sensor 1 of the present invention, showing a front view (a) and a side view (b) of the heat-spreading component 4 composed of a mesh 4c. It will be described later. Figure 5 The annular member 4f shown is preferably made of a wire formed of metal or alloy, which has excellent thermal conductivity, is thin but has sufficient strength, and therefore is a preferred component for the heat spreader 4. As for the metal or alloy constituting the mesh 4c, a material that does not corrode even when in contact with a fluid and has excellent thermal conductivity is preferred. Specifically, wires made of gold, nickel, stainless steel, etc., can be used.

[0056] As for the weaving method of the mesh 4c, other known weaving methods such as plain weave can be used. At the points where the threads of the mesh 4c come into contact with each other, heat transfer based on conduction can occur, thus the mesh 4c is continuously installed throughout the heat exchanger 4. Therefore, it can be said that the grid 4a formed by the mesh 4c is continuously installed in any direction perpendicular to the direction of fluid flow. To make heat conduction more reliable, the contact points between the threads can be firmly connected by means of diffusion bonding, welding, or brazing. Alternatively, multiple meshes 4c can be overlapped in the thickness direction to form the grid 4a.

[0057] The diameter of the wires constituting mesh 4c can be determined taking into account the Reynolds number and thermal conductivity mentioned above. For example, when the gas flow rate is 5.0 standard liters per minute and the diameter of flow path 2 is 8.0 mm, a wire diameter of 0.20 mm or more ensures the cross-sectional area required for thermal conductivity and promotes vortex generation. A wire diameter of 2.0 mm or less ensures the mesh size of mesh 4c and the number of wires per unit cross-sectional area of ​​flow path 2. Therefore, the wire diameter under the above flow conditions is preferably 0.20 mm or more and 2.0 mm or less. A wire diameter is more preferably 0.50 mm or more and 1.5 mm or less.

[0058] When the mesh size of mesh 4c, i.e., the spacing of grids 4a, is 0.10 mm or more, the size of the secondary flow path 4b can be ensured and pressure loss can be reduced. When the mesh size of mesh 4c is 1.0 mm or less, vortex generation can be promoted. Therefore, the mesh size is preferably 0.10 mm or more and 1.0 mm or less. The mesh size is more preferably 0.2 mm or more and 0.8 mm or less.

[0059] The grid 4a formed by the mesh 4c and the flow path 2 are preferably fixed together so that the heat from the flow path 2 can be easily conducted to the grid 4a. Thus, as... Figure 3 As shown by the hollow long arrow in the diagram, it is easy to make heat flow from flow path 2 to grid 4a or make heat flow in the opposite direction, resulting in a more uniform temperature distribution of the fluid.

[0060] In a preferred embodiment of the invention, the lattice 4a is composed of a porous body 4d, which is formed of metal or alloy. Figure 6 These are schematic diagrams illustrating other embodiments of the heat-spreading component 4 included in the temperature sensor 1 of the present invention, showing a front view (a) and a side view (b) of the heat-spreading component 4 composed of a porous body 4d. The porous body 4d, formed of metal or alloy, is obtained, for example, by sintering a powder body formed of metal or alloy; however, the manufacturing method of the porous body 4d is not limited to sintering, and various methods can be used to manufacture the porous body 4d. The porous body 4d formed of metal or alloy has excellent thermal conductivity and sufficient strength, and is therefore preferred as a component constituting the heat-spreading component 4. As the metal or alloy constituting the porous body 4d, a material that does not corrode even when in contact with a fluid and has excellent thermal conductivity is preferred. Specifically, stainless steel or the like can be used.

[0061] In the porous body 4d obtained by sintering powder particles formed of metal or alloy, heat transfer based on conduction can occur through the sintered necks formed at the points where the powder particles contact each other. Therefore, the porous body 4d is continuously arranged throughout the entire heat exchanger 4. Thus, it can be said that the lattice 4a composed of porous bodies 4d is continuously arranged in any direction perpendicular to the direction of fluid flow. Furthermore, by adjusting the size of the powder particles and the degree of sintering, continuous secondary flow paths 4b can be formed inside the porous body 4d. Multiple secondary flow paths 4b converge or branch again inside the heat exchanger 4d and penetrate the porous body 4d from one side to the other. The powder particles constituting the porous body 4d are irregular in shape and have a rougher surface compared to lines. Therefore, when the porous body 4d is used as the heat exchanger 4, fluid turbulence is easily generated.

[0062] When the diameter of the powder particles constituting the porous body 4d is 200 μm or more, the mesh size of the porous body 4d can be ensured, which can promote the generation of vortices. When the diameter of the powder particles is 500 μm or less, the contact area between the powder particles required for heat conduction can be ensured. Therefore, the diameter of the powder particles is preferably 200 μm or more and 500 μm or less. The diameter of the powder particles is more preferably 250 μm or more and 400 μm or less. Similar to the case of the mesh 4c, the grid 4a formed by the porous body 4d and the flow path 2 are preferably fixed together so that the heat of the flow path 2 can be easily conducted to the grid 4a.

[0063] In a preferred embodiment of the invention, the grid 4a is made of perforated metal, which is formed of metal or alloy. As is known to those skilled in the art, perforated metal is a flat metal plate with multiple through holes. Figure 7 These are schematic diagrams illustrating two embodiments of a heat-spreading component 4 made of perforated metal 4e. Figure 7 (a) and Figure 7 (b) are the front view and side view of the heat-spreading component 4 having the annular member 4f described later. Figure 7 (c) and Figure 7 (d) are the front view and side view of the heat spreader 4 without the annular member 4f, respectively. Perforated metal, formed of metal or alloy, has excellent thermal conductivity, is thin yet possesses sufficient strength, and is therefore preferred as a component constituting the heat spreader 4. Furthermore, as... Figure 7 (c) and Figure 7 As shown in (d), it is also possible to omit the through holes in the periphery (diagonal portion) of the punched metal 4e, thereby allowing the periphery of the punched metal 4e to function as a ring-shaped member 4f. As the metal or alloy constituting the punched metal 4e, a material that does not corrode even when in contact with a fluid and has excellent thermal conductivity is preferred. Specifically, a material formed by punching multiple through holes in a flat plate such as gold, nickel, or stainless steel can be used.

[0064] In the perforated metal 4e, thermal movement based on conduction is possible throughout the entire portion except for the part with the through holes. Therefore, the perforated metal 4e is continuously arranged throughout the entire heat exchanger 4. Thus, it can be said that the lattice 4a composed of the perforated metal 4e is continuously arranged in any direction perpendicular to the direction of fluid flow. Alternatively, multiple sheets of perforated metal 4e can be overlapped in the thickness direction to form the lattice 4a.

[0065] The spacing (pitch) between the through holes in the perforated metal 4e, the number of through holes per unit area, and the size of each through hole, as well as the specific structure of the perforated metal 4e, can be appropriately determined, for example, by considering factors such as ensuring the cross-sectional area required for heat conduction, promoting the generation of vortices on the downstream side, and suppressing excessive pressure loss. The lattice 4a formed by the perforated metal 4e and the flow path 2 are preferably fixed together so that the heat from the flow path 2 can be easily conducted to the lattice 4a. Thus, as... Figure 3 As shown by the hollow long arrow in the diagram, it is easy to make heat flow from flow path 2 to grid 4a or make heat flow in the opposite direction, thereby resulting in a more uniform temperature distribution of the fluid.

[0066] In a preferred embodiment of the invention, the heat spreader 4 includes an annular member 4f that impedes the flow of fluid near the inner wall of the flow path 2. Figure 5The heat-spreading member 4, as illustrated, has an annular member 4f around its periphery. The annular member 4f can be constructed, for example, using a flat plate made of metal or alloy, and can be a ring-shaped member with a through-hole formed in its center. The connection between the mesh 4c and the annular member 4f can be achieved, for example, by preparing two annular members 4f of the same shape and fixing them with the mesh 4c sandwiched between them. When the heat-spreading member 4 has the annular member 4f, thermal movement from the flow path 2 to the grid 4a occurs via the annular member 4f. Therefore, the grid 4a, constructed of the mesh 4c, etc., and the annular member 4f surrounding it are preferably fixed together to facilitate thermal movement between them.

[0067] like Figure 3 As shown, the annular member 4f in the heat-spreading component 4 has the function of obstructing the flow of fluid flowing near the inner wall of the flow path 2. The fluid obstructed by the annular member 4f flows downstream through the secondary flow path 4b closest to the annular member 4f. As a result, the fluid that has been heated or cooled during its flow near the inner wall of the flow path 2 changes its flow direction significantly and mixes with the fluid flowing near the center of the flow path 2. As a result, the deviation in the temperature distribution of the fluid can be reduced. In any of the embodiments of the heat-spreading component 4 described above, namely the mesh 4c, the porous body 4d, and the perforated metal 4e, the annular member 4f can be provided.

[0068] In addition, such as Figure 3 As shown, at least a portion of the fluid passing through the through-hole of the annular member 4f forms a large vortex behind the annular member 4f, extending radially outward from the through-hole of the annular member 4f and circling around the annular member 4f. This re-stirs the fluid flowing near the inner wall of the flow path 2, further reducing the deviation in the fluid's temperature distribution.

[0069] In a preferred embodiment of the present invention, the temperature sensor 1 includes a second temperature measuring component 5, which has a temperature measuring point located inside the flow path 2, excluding the center portion. In this embodiment, to distinguish it from the second temperature measuring component 5, the original temperature measuring component is referred to as the first temperature measuring component 3. Figure 1 As illustrated, the temperature measuring point 3a of the first temperature measuring component 3 and the temperature measuring point 5a of the second temperature measuring component 5 are both located on the same plane perpendicular to the direction of fluid flow. In this structure, the first temperature measuring component 3 and the second temperature measuring component 5 are located at the same position in the flow path 2, corresponding to the... Figure 1 The illustrated fluid flow direction is perpendicular to the fluid flow at two different locations on the same plane, and the fluid temperature is measured. From this, it is possible to infer... Figure 4 The temperature distribution shown in the example allows for a more accurate understanding of the fluid's temperature.

[0070] In another embodiment, the present invention is a mass flow meter 7, which includes a temperature sensor 1 according to the present invention and a flow sensor 6 for measuring the flow rate of a fluid flowing in a flow path 2. The flow rate measurement value of the fluid measured by the temperature sensor 1 is used to correct the flow rate measurement value of the fluid measured by the flow sensor 6. Since the temperature sensor 1 of 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. For example, Figure 1 As shown, the flow sensor 6 can be configured as a known thermal flow sensor that includes a branch pipe 6a that merges after branching from the flow path 2, a set of temperature sensing elements 6b provided in the branch pipe 6a, and a bypass 6c provided in the flow path 2. As the flow sensor 6, in addition to the thermal flow sensor, any known flow sensor such as a pressure flow sensor can be used, as long as it does not impair the effect of the present invention.

[0071] In another embodiment, the present invention is an invention of a mass flow control device 8, which includes: a mass flow meter 7 of the present invention; a flow control valve for controlling the flow rate of a fluid flowing in a flow path 2; and a control unit for sending a control signal to the flow control valve so that the flow rate measurement value of the fluid measured by the mass flow meter 7 becomes a predetermined target value. By using the flow measurement value provided by the mass flow meter 7 of the present invention, a mass flow control device 8 that can perform flow control with higher precision than conventional methods can be achieved.

[0072] Example

[0073] The effects of the present invention will be illustrated below using examples. First, a temperature sensor, as an example of the present invention, is shown below. Figure 8 As shown, a temperature sensor 1 is prepared, which includes a flow path 2, a first temperature measuring component 3, and a heat dissipation component 4. Figure 8 The temperature sensor 1 shown has the same characteristics as the flow sensor 6, except that it lacks the flow sensor 6. Figure 1 The temperature sensor 1 shown has the same structure. The first temperature sensing element 3 uses a sheathed temperature sensor with a built-in nickel-chromium / nickel-aluminum thermocouple and an outer diameter of 1.2 mm. The temperature sensing point 3a of the first temperature sensing element 3 is located at the center of the flow path 2 (the first temperature sensing point) (see the blackened circular mark in the figure). Furthermore, the actual position of the first temperature sensing point relative to the target center of the flow path 2 has an error within ±1.0 mm. Additionally, to prevent heat conduction from the flow path 2, the root of the first temperature sensing element 3 is fixed to the closed top end of the branch pipe (branch pipe 2a) that branches off from the flow path 2.

[0074] As the heat dissipation component 4, it uses a material made of Figure 5The component shown is composed of mesh 4c. Mesh 4c is made of stainless steel wire with a diameter of 0.8 mm, woven in a plain weave. The distance between the central axes of the wires is 1.8 mm. The inner diameter of the annular member 4f that fixes mesh 4c is 11.2 mm. Furthermore, the distance between the position of the heat-spreading member 4 on the central axis of the flow path 2 and the position of the first temperature measuring member 3 on the central axis of the flow path 2 is 36.8 mm.

[0075] A nitrogen cylinder (not shown) is supplied with nitrogen gas at an absolute pressure of 0.12 MPa and a gauge pressure of 0.02 MPa at a flow rate of 6.0 standard liters per minute (slm) to the inlet of the gas heater 9 via a mass flow control device (MFC) 8. Nitrogen gas at a pressure of 0.1 MPa flowing from the outlet of the gas heater 9 is supplied to the upstream side of the flow path 2. The gas heater 9 is a gas heater (model: WEX-S1-2U) manufactured by Watty Corporation of Japan. The set temperature of the gas heater 9 is set to 150°C, and nitrogen heating is started. Temperature measurement is initiated using the first temperature measuring element 3 and continued for approximately 30 minutes.

[0076] Next, the power supply to the gas heater 9 was cut off, and after the flow path 2 cooled to room temperature, the nitrogen supply was stopped. The position of the temperature measuring point of the aforementioned sheath-type temperature sensor was changed to a position offset 3.0 mm from the center of the flow path (second temperature measuring point 5a), forming the second temperature measuring element 5 (see the hollow circular mark in the figure). Furthermore, under the same temperature measuring conditions as the first temperature measuring element 3, measurements were continuously taken for approximately 30 minutes. Figure 9 The results of these two temperature measurements are represented by a solid line graph.

[0077] On the other hand, as a comparative example, a temperature sensor was used after removing only the heat-spreading component 4 from the temperature sensor 1 of the above embodiment. Temperature measurements were continuously performed at the first and second temperature measurement points for approximately 30 minutes each. Figure 9 The results of these two temperature measurements are represented by a dotted line graph.

[0078] according to Figure 9The data from the illustrated embodiment and comparative example show that, from the start of temperature measurement, the temperature of nitrogen gas rises rapidly, and after approximately two and a half minutes, the temperature rise slows down slightly. This is because the temperature of the gas heating heater 9 reaches the set temperature of 150°C. Comparing the temperatures at the first temperature measuring point 3a (center of flow path 2) and the second temperature measuring point 5a (3.0 mm from the center), in the comparative example without the heat spreader 4, the temperature difference exceeds approximately 20°C. In contrast, in the embodiment with the heat spreader 4, the temperature difference increases by approximately 15°C.

[0079] The data shows that in the temperature sensor 1 equipped with the heat-spreading component 4 of the present invention, the temperature of the first temperature measuring point 3a (the center of the flow path 2) becomes lower, while the temperature of the second temperature measuring point 5a (3.0 mm from the center) becomes higher. Compared with the prior art, the radial temperature distribution of the flow path becomes more uniform.

[0080] The function of the heat-spreading component 4, composed of mesh 4c, in the embodiment was investigated. Based on the diameter of the steel wire constituting mesh 4c being 0.8 mm, and the viscosity, density, and flow velocity of nitrogen, the Reynolds number, representing the length with the diameter of the steel wire under the conditions of the embodiment, was estimated to be approximately 69. Since this value is greater than 40 and less than 500, it is speculated that although no turbulence is generated on the downstream side of the heat-spreading component 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 flow of nitrogen in a direction perpendicular to the central axis of flow path 2 (radial direction of flow path 2), resulting in material movement in this direction. Consequently, it is believed that the temperature distribution becomes more uniform due to the convection-based thermal movement generated in the direction perpendicular to the flow.

[0081] Furthermore, in addition to the temperature measurements at the first temperature measuring point 3a and the second temperature measuring point 5a, the temperature outside the flow path 2 equipped with the heat-spreading component 4 was measured in this embodiment. The results showed that the temperature was 2°C to 3°C higher than in the comparative example without the heat-spreading component 4. This fact indicates that the mesh 4c constituting the heat-spreading component 4 becomes a heat medium (conductor), resulting in radial heat transfer based on conduction in the flow path 2. That is, it shows that the heat-spreading component 4 of the present invention not only promotes the aforementioned convection-based heat transfer but is also effective for conduction-based heat transfer.

[0082] Furthermore, in the above embodiments, the same temperature sensor is used for both the first measuring component 3 and the second measuring component 5. However, in a preferred embodiment of the present invention, separate temperature sensors can be used to construct the first measuring component 3 and the second measuring component 5. In this preferred embodiment, the temperatures of the fluid at the first temperature measuring point 3a and the second temperature measuring point 5a can be measured simultaneously. Even if the homogenization effect of the temperature distribution based on the heat spreader 4 is insufficient, as described above, it is possible to infer... Figure 4 The illustrated temperature distribution along the radial direction helps to more accurately grasp the temperature of the fluid.

[0083] Explanation of reference numerals in the attached figures

[0084] 1. Temperature sensor; 2. Flow path; 2a. Branch pipe; 3. Temperature measuring component (first temperature measuring component); 3a. Temperature measuring point (first temperature measuring point); 3b. Protective tube; 3c. Base; 3d. Connector; 4. Heat dissipation component; 4a. Grid; 4b. Secondary flow path; 4c. Mesh; 4d. Porous body; 4e. Perforated metal; 4f. Annular component; 5. Second temperature measuring component; 5a. Temperature measuring point (second temperature measuring point); 6. Flow sensor; 6a. Branch pipe; 6b. Temperature measuring element; 6c. Bypass; 7. Mass flow meter; 8. Mass flow control device (MFC); 9. Gas heater.

Claims

1. A temperature sensor used in a mass flow meter, wherein, This temperature sensor has the following features: Flow path, which allows fluid to flow; A temperature measuring component having a temperature measuring point at a predetermined location inside the flow path; and A heat spreader, located upstream of the temperature measuring point in the flow path, is configured to reduce the deviation in the radial temperature distribution of the fluid in the flow path. The heat dissipation component includes: A grid, which consists of periodically arranged separators, is continuously arranged in two or more different directions in a plane perpendicular to the direction of fluid flow. A secondary flow path, which is divided by the grid; as well as An annular member protrudes from the inner wall of the flow path toward the center of the cross-section of the flow path, obstructing the flow of the fluid flowing near the inner wall of the flow path.

2. The temperature sensor according to claim 1, wherein, The grid is made of a mesh woven from threads made of metal or alloy.

3. The temperature sensor according to claim 1, wherein, The lattice is composed of a porous body formed of metal or alloy.

4. The temperature sensor according to claim 1, wherein, The grid is made of perforated metal, which is formed of metal or alloy.

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

6. The temperature sensor according to any one of claims 1 to 4, wherein, The temperature sensor also includes a second temperature measuring component, which has a temperature measuring point located inside the flow path, excluding the center of the cross-section of the flow path. The temperature measuring points of the first temperature measuring component and the second temperature measuring component are both located on the same plane perpendicular to the direction of fluid flow.

7. The temperature sensor according to any one of claims 1 to 4, wherein, The flow path includes a heating element.

8. A mass flow meter, wherein, The mass flow meter includes a temperature sensor as described in any one of claims 1 to 7 and a flow sensor for measuring the flow rate of the fluid flowing in the flow path. The flow rate of the fluid measured by the flow sensor is corrected using the temperature measurement value of the fluid measured by the temperature measuring component.

9. A mass flow control device, wherein, This mass flow control device has the following features: The mass flow meter according to claim 8; A flow control valve that controls the flow rate of the fluid flowing in the flow path; and The control unit sends a control signal to the flow control valve so that the flow rate measured by the mass flow meter becomes a predetermined target value.

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