Thermal mass flow meter and thermal mass flow controller

Abstract

The present application relates to the technical field of flowmeters, and provides a thermal mass flowmeter and a thermal mass flow controller, wherein the thermal mass flowmeter includes a main line and a flow sensor, wherein the main line has a main flow channel, and the flow sensor includes a first side pipe, a first thermistor, a second side pipe, and a second thermistor; the first thermistor is arranged on the first side pipe, and both ends of the first side pipe are connected to the main line; the second thermistor is arranged on the second side pipe; the thermal mass flowmeter also includes a side flow channel, a connecting flow channel, and an auxiliary valve, and both ends of the second side pipe are connected to the side flow channel; the connecting flow channel connects the side flow channel and the main flow channel, or the connecting flow channel connects the second side pipe and the main flow channel, and the auxiliary valve is arranged on the connecting flow channel. The above-mentioned thermal mass flowmeter can obtain a true flow value in any installation posture by arranging two groups of side pipes and thermistors on the main line, thereby solving the problem of poor flow measurement accuracy.

Description

Technical Field

[0001] The present application relates to the technical field of flow meters, and in particular to a thermal mass flow meter and a thermal mass flow controller. Background Art

[0002] Thermal Mass Flow Controller (MFC) is an instrument for measuring and controlling fluid flow, and is widely used in semiconductor manufacturing, biopharmaceuticals, environmental monitoring and other fields that require precise control of fluid flow. Its working principle is based on the heat change caused by the fluid passing through the sensor. The size of the fluid flow directly affects the sensor temperature. By monitoring this temperature change, the real-time flow of the fluid can be calculated.

[0003] The flow sensor is a key component of the thermal mass flow controller, which is generally composed of an upstream thermistor, a downstream thermistor, a capillary, and a control circuit. The principle is to heat the upstream thermistor and the downstream thermistor by loading current. When there is no fluid flowing in the capillary, the heating power of the two thermistors remains balanced; when there is fluid flowing in the capillary, the heat exchange between the fluid and the thermistor will cause the heating power of the two thermistors to change, and this change increases with the increase of the fluid mass flow rate. By measuring the voltage on the thermistor and converting it through the control circuit, the fluid flow rate can be converted into an electrical signal, thereby achieving accurate measurement of the mass flow rate.

[0004] like Figure 1 As shown, when the measuring part 21 of the flow sensor 20 is perpendicular to the direction of gravity, the fluid in the measuring part 21 of the flow sensor 20 is heated by the thermistor 22 to a temperature higher than the fluid temperature in the main flow channel 31 of the main pipe 30. Due to the temperature difference, the density of the fluid in the measuring part 21 of the flow sensor 20 is lower than the density of the fluid in the main flow channel 31 of the main pipe 30. Therefore, when the main valve 32 of the main pipe 30 is in the closed position, a density gradient will be formed and maintained by gravity, wherein the fluid with a lower temperature and a higher density is in the main flow channel 31, and the fluid with a higher temperature and a lower density is in the flow sensor 20, and no deviation is generated.

[0005] like Figure 2As shown, when the measuring part 21 of the flow sensor 20 is parallel to the gravity direction, the fluid in the measuring part 21 of the flow sensor 20 will be heated by the thermistor 22 to a temperature higher than the fluid temperature in the main channel 31. The fluid with a higher temperature and lower density in the measuring part 21 of the flow sensor 20 rises and enters the main channel 31 from the outlet of the flow sensor 20, and the fluid is cooled to form a downdraft; when the main valve 32 of the main pipeline 30 is in the closed position, the downdraft enters the flow sensor 20 through the inlet of the flow sensor 20 and is heated by the thermistor 22, thus forming a circulation loop. The above phenomenon of the spontaneous circulation of liquid or gas caused by gravity and temperature difference is called thermal siphon phenomenon.

[0006] Due to the existence of thermal siphon phenomenon, the electrical signal of the flow sensor will be detected and calculated through the acquisition circuit to determine whether flow is generated, resulting in flow measurement errors and affecting the flow measurement accuracy of the thermal mass flow controller. Utility Model Content

[0007] In view of this, the embodiments of the present application provide a thermal mass flow meter and a thermal mass flow controller to solve the problem of poor flow measurement accuracy.

[0008] In a first aspect of the present application, a thermal mass flowmeter is provided, comprising a main pipe and a flow sensor, wherein the main pipe has a main flow channel, the flow sensor is installed on the main pipe, the flow sensor comprises a first bypass pipe, a first upstream thermistor, a first downstream thermistor, a second bypass pipe, a second upstream thermistor, and a second downstream thermistor; the first upstream thermistor and the first downstream thermistor are arranged on the first bypass pipe, a first upstream interface and a first downstream interface are arranged at intervals along the flow direction of the fluid on the main pipe, and the two ends of the first bypass pipe are respectively connected to the first upstream interface and the first downstream interface; the second upstream thermistor and the second downstream thermistor are arranged on the second bypass pipe; the thermal mass flowmeter also comprises a bypass flow channel, a connecting flow channel and an auxiliary valve, a second upstream interface and a second downstream interface are arranged at intervals along the flow direction of the fluid on the bypass flow channel, and the two ends of the second bypass pipe are respectively connected to the second upstream interface and the second downstream interface; the connecting flow channel connects the bypass flow channel and the main flow channel, or the connecting flow channel connects the second bypass pipe and the main flow channel, and the auxiliary valve is arranged on the connecting flow channel.

[0009] The thermal mass flowmeter provided in the embodiment of the present application has the following beneficial effects: when in use, the auxiliary valve is first opened to allow the fluid in the main channel to enter the first side pipe, the second side pipe and the side channel, and the auxiliary valve is closed after the fluid stabilizes. At this time, the first side pipe feeds back the measurement signal, and the independent circulation loop formed by the second side pipe and the side channel feeds back the error signal generated by the thermal siphon effect. The error signal is removed from the measurement signal through the back-end acquisition circuit, so that the thermal mass flowmeter can obtain the true flow value in any installation posture, thereby solving the problem of poor flow measurement accuracy.

[0010] In some embodiments, the bypass channel is disposed on the main channel.

[0011] By adopting the above technical solution, it is only necessary to open a bypass channel on the main pipeline without adding additional pipelines, thereby simplifying the structure of the thermal mass flowmeter.

[0012] In some embodiments, the connecting flow channel is disposed on the main flow channel, and the connecting flow channel connects the main flow channel and the side flow channel.

[0013] By adopting the above technical solution, it is only necessary to open a connecting flow channel on the main pipeline without adding additional pipelines, thereby simplifying the structure of the thermal mass flowmeter.

[0014] In some embodiments, the bypass channel is arranged close to the main channel.

[0015] By adopting the above technical solution, the temperature of the fluid in the side flow channel is made closer to the temperature of the fluid in the main flow channel, so that the measurement result is more accurate.

[0016] In some embodiments, the bypass channel includes a third upstream channel, a third intermediate channel and a third downstream channel, the two ends of the third intermediate channel are respectively connected to the third upstream channel and the third downstream channel, the third intermediate channel extends along the flow direction of the fluid, and the second upstream interface and the second downstream interface are respectively arranged on the third upstream channel and the third downstream channel.

[0017] By adopting the above technical solution, the structure of the side flow channel is simplified, which is beneficial to the flow of fluid in the side flow channel.

[0018] In some embodiments, the second bypass pipe includes a second upstream pipe section, a second intermediate pipe section and a second downstream pipe section, two ends of the second intermediate pipe section are respectively connected to the second upstream pipe section and the second downstream pipe section, the second intermediate pipe section extends along the flow direction of the fluid, and the second upstream thermistor and the second downstream thermistor are arranged on the second intermediate pipe section.

[0019] By adopting the above technical solution, the structure of the second bypass pipe is simplified, which is beneficial to the flow of fluid in the second bypass pipe.

[0020] In some embodiments, the first bypass pipe includes a first upstream pipe section, a first intermediate pipe section and a first downstream pipe section, two ends of the first intermediate pipe section are respectively connected to the first upstream pipe section and the first downstream pipe section, the first intermediate pipe section extends along the flow direction of the fluid, and the first upstream thermistor and the first downstream thermistor are arranged on the first intermediate pipe section.

[0021] By adopting the above technical solution, the structure of the first bypass pipe is simplified, which is beneficial to the flow of fluid in the first bypass pipe.

[0022] In some embodiments, the thermal mass flowmeter further includes a laminar flow element disposed in the main flow channel, and the first upstream interface and the first downstream interface are respectively located on both sides of the laminar flow element in the flow direction of the fluid.

[0023] The laminar flow element is arranged in the main flow channel to form a stable laminar flow state and ensure the accurate flow separation between the flow rate flowing through the flow sensor and the flow rate in the main flow channel.

[0024] In some embodiments, the first side tube and / or the second side tube is a capillary tube.

[0025] By adopting the above technical solution, the flow sensor is less affected by temperature and pressure during measurement.

[0026] The second aspect of the present application provides a thermal mass flow controller, which includes a main valve and a thermal mass flow meter as described in the first aspect, wherein the main valve is installed at the fluid outlet of the thermal mass flow meter.

[0027] The thermal mass flow controller adopts any one or more embodiments of the thermal mass flow meter described above, and thus has the beneficial effects of the above embodiments, which will not be described one by one here.

[0028] The above description is only an overview of the technical solution of the present application. In order to more clearly understand the technical means of the present application, it can be implemented in accordance with the contents of the specification. In order to make the above and other purposes, features and advantages of the present application more obvious and easy to understand, the specific implementation methods of the present application are listed below. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for use in the embodiments or conventional technical descriptions will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0030] Figure 1 It is a structural schematic diagram of a first installation posture of an existing thermal mass flow controller;

[0031] Figure 2 It is a structural schematic diagram of a second installation posture of an existing thermal mass flow controller;

[0032] Figure 3 is a structural schematic diagram of a first installation posture of a thermal mass flowmeter provided in an embodiment of the present application;

[0033] Figure 4 yes Figure 3 Structural diagram of the central main pipeline;

[0034] Figure 5 yes Figure 3 Schematic diagram of the structure of the medium flow sensor;

[0035] Figure 6 is a structural schematic diagram of a second installation posture of a thermal mass flowmeter provided in an embodiment of the present application;

[0036] Figure 7 It is a schematic diagram of the structure of a thermal mass flow controller provided in an embodiment of the present application.

[0037] The meanings of the marks in the figure are:

[0038] 10. Thermal mass flow meter;

[0039] 11. Main pipeline; 111. Main flow channel; 112. First upstream interface; 113. First downstream interface;

[0040] 12. flow sensor; 121. first bypass pipe; 1211. first upstream pipe section; 1212. first intermediate pipe section; 1213. first downstream pipe section; 122. first upstream thermistor; 123. first downstream thermistor; 124. second bypass pipe; 1241. second upstream pipe section; 1242. second intermediate pipe section; 1243. second downstream pipe section; 125. second upstream thermistor; 126. second downstream thermistor;

[0041] 13, bypass channel; 131, third upstream channel; 1311, second upstream interface; 132, third intermediate channel; 133, third downstream channel; 1331, second downstream interface;

[0042] 14. Connect the flow channel;

[0043] 15. Auxiliary valve;

[0044] 16. Laminar flow element;

[0045] 17. Main valve;

[0046] 20. Flow sensor; 21. Measuring part; 22. Thermistor;

[0047] 30. Main pipe; 31. Main flow channel; 32. Main valve;

[0048] 100. Thermal mass flow controller. DETAILED DESCRIPTION

[0049] The following embodiments of the technical solution of the present application are described in detail in conjunction with the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present application, and are therefore only used as examples, and cannot be used to limit the scope of protection of the present application.

[0050] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by technicians in the technical field to which this application belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" in the specification and claims of this application and the above-mentioned figure descriptions and any variations thereof are intended to cover non-exclusive inclusions.

[0051] In the description of the embodiments of the present application, the technical terms "first", "second", etc. are only used to distinguish different objects, and cannot be understood as indicating or implying relative importance or implicitly indicating the number, specific order or primary and secondary relationship of the indicated technical features. In the description of the embodiments of the present application, the meaning of "multiple" is more than two, unless otherwise clearly and specifically defined.

[0052] Reference to "embodiments" herein means that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment of the present application. The appearance of the phrase in various locations in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0053] In the description of the embodiments of the present application, the term "and / or" is only a description of the association relationship of the associated objects, indicating that there may be three relationships. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. In addition, the character " / " in this article generally indicates that the associated objects before and after are in an "or" relationship.

[0054] In the description of the embodiments of the present application, the term "multiple" refers to more than two (including two). Similarly, "multiple groups" refers to more than two groups (including two groups), and "multiple pieces" refers to more than two pieces (including two pieces).

[0055] In the description of the embodiments of the present application, the orientations or positional relationships indicated by technical terms such as "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "vertical", "horizontal", "top", "bottom", "inside" and "outside" are based on the orientations or positional relationships shown in the accompanying drawings. They are only for the convenience of describing the embodiments of the present application and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation. Therefore, they should not be understood as limitations on the embodiments of the present application.

[0056] In the description of the embodiments of the present application, unless otherwise clearly specified and limited, technical terms such as "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, and it can be the internal connection of two elements or the interaction relationship between two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the embodiments of the present application can be understood according to the specific circumstances.

[0057] Thermosyphon refers to the phenomenon of spontaneous circulation of liquid or gas in thermal flow sensors due to gravity and temperature differences. When the flow sensor is in a vertical or inclined position, the temperature difference between the capillary tube of the flow sensor and the main flow channel of the main pipeline will produce natural convection, causing the fluid to circulate in the capillary tube and the main flow channel. This phenomenon may affect the measurement accuracy of the flow sensor. The specific mechanism is as follows:

[0058] Temperature differences create buoyancy: The flow sensor's heating element raises the temperature of the adjacent fluid, which reduces density and creates an upward buoyancy force.

[0059] Natural convection: Due to buoyancy, hot fluids rise and cold fluids sink, forming a natural convection cycle. This convection may not be consistent with the actual measured fluid flow direction, thus introducing errors.

[0060] Impact on measurement accuracy: This natural convection will interfere with the normal operation of the flow sensor, making the temperature difference detected by the flow sensor not entirely caused by the actual flow, thus affecting the measurement accuracy.

[0061] The first aspect of the present application provides a thermal mass flow meter. Figure 3 , Figure 4 and Figure 6The thermal mass flowmeter 10 includes a main pipe 11 and a flow sensor 12. The main pipe 11 has a main flow channel 111. The flow sensor 12 is installed on the main pipe 11. The flow sensor 12 includes a first bypass pipe 121, a first upstream thermistor 122, a first downstream thermistor 123, a second bypass pipe 124, a second upstream thermistor 125, and a second downstream thermistor 126. The first upstream thermistor 122 and the first downstream thermistor 123 are arranged on the first bypass pipe 121. The main pipe 11 is provided with a first upstream interface 112 and a first downstream interface 113 at intervals along the flow direction of the fluid. Both ends of the first bypass pipe 121 are connected to the first upstream interface 113. 112 is connected to the first downstream interface 113; the second upstream thermistor 125 and the second downstream thermistor 126 are arranged on the second bypass pipe 124; the thermal mass flowmeter 10 also includes a bypass channel 13, a connecting channel 14 and an auxiliary valve 15, and the bypass channel 13 is provided with a second upstream interface 1311 and a second downstream interface 1331 at intervals along the flow direction of the fluid, and the two ends of the second bypass pipe 124 are respectively connected to the second upstream interface 1311 and the second downstream interface 1331; the connecting channel 14 connects the bypass channel 13 and the main channel 111, or the connecting channel 14 connects the second bypass pipe 124 and the main channel 111, and the auxiliary valve 15 is arranged on the connecting channel 14.

[0062] The main passage 11 has a fluid inlet and a fluid outlet at both ends in the flow direction of the fluid, and both the fluid inlet and the fluid outlet are connected to the main passage 111. The fluid flows into the main passage 111 through the fluid inlet and flows out from the fluid outlet. The flow sensor 12 measures the flow rate of the fluid when the fluid flows through the main passage 11.

[0063] The present application does not limit the manner in which the flow sensor 12 is installed on the main pipe 11 . For example, the flow sensor 12 may be fixed to the main pipe 11 by welding, or the flow sensor 12 may be fixed to the main pipe 11 by fasteners.

[0064] The two ends of the first bypass tube 121 are connected to the first upstream interface 112 and the first downstream interface 113 respectively, and the tube cavity of the first bypass tube 121 and the main channel 111 form a circulation loop, and the fluid in the main channel 111 can continuously enter the first bypass tube 121. The first upstream thermistor 122 and the first downstream thermistor 123 are arranged on the first bypass tube 121, and can feed back the measurement signal of the main channel 111 when the fluid flows through the first bypass tube 121.

[0065] The two ends of the second bypass pipe 124 are connected to the second upstream interface 1311 and the second downstream interface 1331 respectively. When the auxiliary valve 15 is opened, the fluid in the main channel 111 can enter the second bypass pipe 124 and the bypass channel 13; when the auxiliary valve 15 is closed, the fluid in the main channel 111 can no longer enter the second bypass pipe 124 and the bypass channel 13. At this time, the second bypass pipe 124 and the bypass channel 13 form an independent circulation loop. Among them, the second upstream thermistor 125 and the second downstream thermistor 126 are arranged on the second bypass pipe 124, and can feedback the error signal generated by the thermal siphon effect when the auxiliary valve 15 is closed.

[0066] The first upstream thermistor 122 and the second upstream thermistor 125 are the same, and the first downstream thermistor 123 and the second downstream thermistor 126 are the same, so as to ensure that the error fed back by the second bypass tube 124 is the error in the first bypass tube 121 .

[0067] It can be understood that each thermistor can be a winding or a tubular structure, etc.

[0068] When the thermal mass flowmeter 10 provided in the embodiment of the present application is used, the auxiliary valve 15 is first opened to allow the fluid in the main channel 111 to enter the first side pipe 121, the second side pipe 124 and the side channel 13, and the auxiliary valve 15 is closed after the fluid is stable. At this time, the first side pipe 121 feeds back the measurement signal, and the independent circulation loop formed by the second side pipe 124 and the side channel 13 feeds back the error signal generated by the thermal siphon effect. The error signal is removed from the measurement signal through the acquisition circuit at the back end, so that the thermal mass flowmeter 10 can obtain the real flow value in any installation posture (for example, vertical state or inclined state), solving the problem of poor flow measurement accuracy. Moreover, it does not rely on a large number of experimental databases in the early stage, and can perform correction and calibration regularly in real time, which effectively simplifies the process and improves efficiency.

[0069] Please refer to Figure 4 In some embodiments, the bypass channel 13 is disposed on the main flow path 11 .

[0070] In this way, it is only necessary to open the bypass channel 13 on the main pipeline 11 without adding additional pipelines, thereby simplifying the structure of the thermal mass flowmeter 10 .

[0071] In other embodiments, the flow sensor 12 may also include a third bypass tube, and the lumen of the third bypass tube constitutes the bypass flow channel 13 .

[0072] Please refer to Figure 4 In some embodiments, the connecting flow channel 14 is disposed on the main flow channel 11 , and the connecting flow channel 14 connects the main flow channel 111 and the side flow channel 13 .

[0073] In this way, it is only necessary to open a connecting flow channel 14 on the main flow line 11 without adding additional pipelines, thereby simplifying the structure of the thermal mass flowmeter 10; moreover, the side flow channel 13 and the connecting flow channel 14 are both arranged on the main flow line 11, which is conducive to the connecting flow channel 14 connecting the main flow channel 111 and the side flow channel 13.

[0074] In other embodiments, the flow sensor 12 may also include a connecting tube, the lumen of the connecting tube forms a connecting flow channel 14 , and the connecting tube connects the first bypass tube 121 and the second bypass tube 124 .

[0075] In some embodiments, the bypass channel 13 is arranged close to the main channel 111 .

[0076] By adopting the above technical solution, the temperature of the fluid in the bypass channel 13 is closer to the temperature of the fluid in the main channel 111, so that the measurement result is more accurate.

[0077] Please refer to Figure 4 In some embodiments, the bypass channel 13 includes a third upstream channel 131, a third intermediate channel 132 and a third downstream channel 133, the two ends of the third intermediate channel 132 are respectively connected to the third upstream channel 131 and the third downstream channel 133, the third intermediate channel 132 extends along the flow direction of the fluid, and the second upstream interface 1311 and the second downstream interface 1331 are respectively arranged on the third upstream channel 131 and the third downstream channel 133.

[0078] The third intermediate flow channel 132 extends along the flow direction of the fluid, that is, the third intermediate flow channel 132 is parallel to the main flow channel 111; wherein, the third upstream flow channel 131 and the third downstream flow channel 133 both extend along the radial direction of the main flow channel 111. It can be understood that the third upstream flow channel 131 and the third downstream flow channel 133 can be arranged in parallel, that is, the angle between the third upstream flow channel 131 and the third intermediate flow channel 132 and the angle between the third downstream flow channel 133 and the third intermediate flow channel 132 are the same, for example, both are 90°; or, the angle between the third upstream flow channel 131 and the third intermediate flow channel 132 and the angle between the third downstream flow channel 133 and the third intermediate flow channel 132 can both be acute angles; or, the angle between the third upstream flow channel 131 and the third intermediate flow channel 132 and the angle between the third downstream flow channel 133 and the third intermediate flow channel 132 can both be obtuse angles.

[0079] By adopting the above technical solution, the structure of the bypass channel 13 is simplified, which is beneficial to the flow of fluid in the bypass channel 13 .

[0080] Please also refer to Figure 3 and Figure 5In some embodiments, the second bypass pipe 124 includes a second upstream pipe section 1241, a second intermediate pipe section 1242 and a second downstream pipe section 1243, the two ends of the second intermediate pipe section 1242 are respectively connected to the second upstream pipe section 1241 and the second downstream pipe section 1243, the second intermediate pipe section 1242 extends along the flow direction of the fluid, and the second upstream thermistor 125 and the second downstream thermistor 126 are arranged on the second intermediate pipe section 1242.

[0081] The second intermediate pipe section 1242 extends along the flow direction of the fluid, that is, the second intermediate pipe section 1242 is parallel to the main flow channel 111; wherein, the second upstream pipe section 1241 and the second downstream pipe section 1243 both extend along the radial direction of the main flow channel 111. It can be understood that the second upstream pipe section 1241 and the second downstream pipe section 1243 can be arranged in parallel, that is, the angle between the second upstream pipe section 1241 and the second intermediate pipe section 1242 and the angle between the second downstream pipe section 1243 and the second intermediate pipe section 1242 are the same, for example, both are 90°; or, the angle between the second upstream pipe section 1241 and the second intermediate pipe section 1242 and the angle between the second downstream pipe section 1243 and the second intermediate pipe section 1242 can both be acute angles; or, the angle between the second upstream pipe section 1241 and the second intermediate pipe section 1242 and the angle between the second downstream pipe section 1243 and the second intermediate pipe section 1242 can both be obtuse angles.

[0082] The circulation loop formed by the second bypass pipe 124 and the bypass flow channel 13 is a rectangular structure.

[0083] By adopting the above technical solution, the structure of the second bypass pipe 124 is simplified, which is beneficial to the flow of fluid in the second bypass pipe 124 .

[0084] Please also refer to Figure 3 and Figure 5 In some embodiments, the first bypass pipe 121 includes a first upstream pipe section 1211, a first intermediate pipe section 1212 and a first downstream pipe section 1213, the two ends of the first intermediate pipe section 1212 are respectively connected to the first upstream pipe section 1211 and the first downstream pipe section 1213, the first intermediate pipe section 1212 extends along the flow direction of the fluid, and the first upstream thermistor 122 and the first downstream thermistor 123 are arranged on the first intermediate pipe section 1212.

[0085] The first intermediate pipe section 1212 extends along the flow direction of the fluid, that is, the first intermediate pipe section 1212 is parallel to the main flow channel 111; wherein, the first upstream pipe section 1211 and the first downstream pipe section 1213 both extend along the radial direction of the main flow channel 111. It can be understood that the first upstream pipe section 1211 and the first downstream pipe section 1213 can be arranged in parallel, that is, the angle between the first upstream pipe section 1211 and the first intermediate pipe section 1212 and the angle between the first downstream pipe section 1213 and the first intermediate pipe section 1212 are the same, for example, both are 90°; or, the angle between the first upstream pipe section 1211 and the first downstream pipe section 1213 and the angle between the first downstream pipe section 1213 and the first intermediate pipe section 1212 can both be acute angles; or, the angle between the first upstream pipe section 1211 and the first downstream pipe section 1213 and the angle between the first downstream pipe section 1213 and the first intermediate pipe section 1212 can both be obtuse angles.

[0086] Optionally, the first bypass pipe 121 and the second bypass pipe 124 have the same shape and size.

[0087] By adopting the above technical solution, the structure of the first bypass pipe 121 is simplified, which is beneficial to the flow of the fluid in the first bypass pipe 121 .

[0088] Please also refer to Figure 3 and Figure 4 In some embodiments, the thermal mass flowmeter 10 further includes a laminar flow element 16 disposed in the main flow channel 111 , and the first upstream interface 112 and the first downstream interface 113 are respectively located on both sides of the laminar flow element 16 in the flow direction of the fluid.

[0089] The laminar flow element 16 is disposed in the main flow channel 111 to form a stable laminar flow state and ensure accurate flow separation between the flow rate passing through the flow sensor 12 and the flow rate in the main flow channel 111 .

[0090] In other embodiments, at certain small ranges, the laminar flow element 16 may not be provided in the main channel 111 .

[0091] In some embodiments, the first bypass tube 121 and the second bypass tube 124 are capillaries.

[0092] By adopting the above technical solution, the flow sensor 12 is less affected by temperature and pressure during measurement.

[0093] In other embodiments, the first bypass tube 121 is a capillary tube, and the second bypass tube 124 is other tubes with similar functions to the capillary tube; or, the second bypass tube 124 is a capillary tube, and the first bypass tube 121 is other tubes with similar functions to the capillary tube.

[0094] like Figure 7As shown, the second aspect of the present application proposes a thermal mass flow controller 100 , which includes a main valve 17 and the thermal mass flow meter 10 as described in the first aspect, and the main valve 17 is installed at the fluid outlet of the thermal mass flow meter 10 .

[0095] It should be noted that the flow sensor 12 also includes a control circuit, which controls the opening size of the main valve 17 according to the flow value measured by the flow sensor 12. The specific control process is as follows:

[0096] Sensor analog front-end circuit: includes pre-processing circuits for filtering, amplifying, calculating, multiplexing and other operations on analog signals, receives the analog signals uploaded back from the flow sensor 12 and transmits them to the ADC for collection.

[0097] Analog-to-digital converter (ADC): responsible for converting the analog signal collected by the flow sensor 12 and the analog signal of the NTC thermistor into a digital signal for processing by the microcontroller unit (MCU).

[0098] Microcontroller unit (MCU): MCU is the calculation and control center of the system. It receives the digital signal from the ADC, calculates the actual flow rate according to the Vu and Vd values ​​on the flow sensor 12 and the real-time detected NTC temperature value, and generates the corresponding control signal to be sent to the DAC.

[0099] Digital-to-Analog Converter (DAC): The DAC converts the digital control signal generated by the MCU into an analog signal, which is used to adjust the input control signal of the piezoelectric drive circuit to achieve precise control of the flow rate.

[0100] The thermal mass flow controller 100 adopts any one or more embodiments of the thermal mass flow meter 10 described above, and thus has the beneficial effects of the above embodiments, which will not be described one by one here.

[0101] The technical solution of this application has broad application prospects in achieving high-precision and high-stability flow control. The following are the known and potential technical and product application fields of this application, as well as their specific application methods:

[0102] Semiconductor manufacturing: The key steps in the semiconductor manufacturing process, such as chemical vapor deposition (CVD) and physical vapor deposition (PVD), require extremely high gas flow control accuracy. The installation posture flow correction technology of this application can provide more accurate flow data to ensure the consistency of the manufacturing process and the quality of the product.

[0103] Pharmaceutical Industry: In the field of biopharmaceuticals, especially in the process of culturing cells and producing drugs, accurate gas control is crucial. This application can improve the accuracy of flow control and ensure the accuracy and safety of drug synthesis.

[0104] Environmental monitoring equipment: In environmental protection fields such as air quality monitoring and water quality testing, continuous and accurate monitoring and control of sampling flow is required. This application can provide fast response and high-precision flow monitoring, improving the reliability of environmental monitoring.

[0105] Laboratory and scientific research equipment: Scientific research experiments often require precise control and measurement of extremely small gas or liquid flows. The technical solution of this application can provide precise flow control for various laboratories, supporting the accuracy and efficiency of scientific research work.

[0106] Chemical process control: In the field of chemical production and fine chemicals, the precise proportioning and control of fluids directly affects product quality. The technical solution of this application provides key control parameters for fine chemical processes by providing stable and accurate flow measurement.

[0107] Aerospace and Military Applications: In aerospace and military equipment, the accuracy and response time of flow control are critical to the performance of the entire system. This application can provide the required high-precision flow control in these demanding applications.

[0108] Food and Beverage Industry: In the production process of food and beverage, ensuring accurate gas and liquid addition is necessary to ensure the taste and quality standards of the product. This application can provide high-precision and high-stability flow control in these applications.

[0109] The above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present application, and should all be included in the protection scope of the present application.

Claims

1. A thermal mass flowmeter, characterized in that: The invention comprises a main pipe and a flow sensor, wherein the main pipe has a main flow channel, the flow sensor is installed on the main pipe, the flow sensor comprises a first bypass pipe, a first upstream thermistor, a first downstream thermistor, a second bypass pipe, a second upstream thermistor, and a second downstream thermistor; the first upstream thermistor and the first downstream thermistor are arranged on the first bypass pipe, the main pipe is provided with a first upstream interface and a first downstream interface at intervals along the flow direction of the fluid, and the two ends of the first bypass pipe are respectively connected to the first upstream interface and the first downstream interface; the second upstream thermistor and the second downstream thermistor are arranged on the second bypass pipe; the thermal mass flow meter also comprises a bypass flow channel, a connecting flow channel and an auxiliary valve, the bypass flow channel is provided with a second upstream interface and a second downstream interface at intervals along the flow direction of the fluid, and the two ends of the second bypass pipe are respectively connected to the second upstream interface and the second downstream interface; the connecting flow channel connects the bypass flow channel and the main flow channel, or the connecting flow channel connects the second bypass pipe and the main flow channel, and the auxiliary valve is arranged on the connecting flow channel.

2. The thermal mass flowmeter according to claim 1, characterized in that: The bypass channel is arranged on the main pipe.

3. The thermal mass flowmeter according to claim 2, characterized in that: The connecting flow channel is arranged on the main flow channel, and the connecting flow channel communicates the main flow channel and the side flow channel.

4. The thermal mass flowmeter according to claim 2, characterized in that: The side flow channel is arranged close to the main flow channel.

5. The thermal mass flowmeter according to any one of claims 1 to 4, characterized in that: The bypass channel includes a third upstream channel, a third intermediate channel and a third downstream channel. The two ends of the third intermediate channel are respectively connected to the third upstream channel and the third downstream channel. The third intermediate channel extends along the flow direction of the fluid. The second upstream interface and the second downstream interface are respectively arranged on the third upstream channel and the third downstream channel.

6. The thermal mass flowmeter according to any one of claims 1 to 4, characterized in that: The second bypass pipe includes a second upstream pipe section, a second intermediate pipe section and a second downstream pipe section, two ends of the second intermediate pipe section are respectively connected to the second upstream pipe section and the second downstream pipe section, the second intermediate pipe section extends along the flow direction of the fluid, and the second upstream thermistor and the second downstream thermistor are arranged on the second intermediate pipe section.

7. The thermal mass flowmeter according to any one of claims 1 to 4, characterized in that: The first bypass pipe includes a first upstream pipe section, a first intermediate pipe section and a first downstream pipe section, two ends of the first intermediate pipe section are respectively connected to the first upstream pipe section and the first downstream pipe section, the first intermediate pipe section extends along the flow direction of the fluid, and the first upstream thermistor and the first downstream thermistor are arranged on the first intermediate pipe section.

8. The thermal mass flowmeter according to any one of claims 1 to 4, characterized in that: The thermal mass flowmeter further includes a laminar flow element disposed in the main flow channel, and the first upstream interface and the first downstream interface are respectively located on two sides of the laminar flow element in the flow direction of the fluid.

9. The thermal mass flowmeter according to any one of claims 1 to 4, characterized in that: The first side tube and / or the second side tube is a capillary tube.

10. Thermal mass flow controller, characterized in that: It comprises a main valve and a thermal mass flowmeter as claimed in any one of claims 1 to 9, wherein the main valve is installed at a fluid outlet of the thermal mass flowmeter.

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