A thermal mass flowmeter probe

Abstract

The present invention discloses a thermal mass flowmeter probe, which includes a hollow outer shell, a heating element with temperature detection function and a temperature detection element; the heating element is arranged at the lower end inside the outer shell, and its lower end face is in the same plane as the lower end face of the outer shell and is axially perpendicular to the outer shell; the temperature detection element is arranged inside the outer shell and is thermally isolated from the heating element. Compared with the prior art, the heating element in the thermal mass flowmeter probe of the present invention is arranged at the lower end inside the outer shell and the lower end face is axially perpendicular to the connecting shaft of the thermal mass flowmeter. Therefore, while the heating element is well protected, it can also have good thermal contact with the fluid, thereby improving the measurement accuracy of the thermal mass flowmeter probe. In addition, the heating element and the temperature detection element are thermally isolated, reducing the influence of the heating element on the temperature detection element, making the measurement of the fluid temperature more accurate, and thus the flow measurement more accurate.

Description

Technical Field

[0001] The present invention relates to the technical field of metering devices, and particularly to a thermal mass flowmeter probe. Background Art

[0002] Existing thermal flowmeters all have a heating element with a temperature detection function and a temperature detection element. The temperature detection element is used to measure the temperature T1 of the fluid, and the heating element automatically heats to a temperature T2 higher than the fluid temperature. Existing thermal flowmeters are generally divided into two types:

[0003] The first type is a constant power thermal flowmeter, and its working principle is: the temperature detection element measures the temperature T1 of the fluid, and the heating element automatically heats to the temperature T2. When fluid flows through the temperature detection element and the heating element, a part of the heat of the heating element will be carried away by the fluid, causing the temperature of the heating element to drop. Since the heating power of the heating element remains constant, the faster the fluid flow rate, the more heat is carried away, and the greater the temperature drop of the heating element. Thus, the mass flow rate of the fluid can be measured through the functional relationship between the fluid flow rate and the temperature drop value of the heating element.

[0004] The second type is a constant temperature difference thermal flowmeter, and its working principle is: the temperature detection element measures the temperature T1 of the fluid, and the heating element automatically heats to the temperature T2. When fluid flows through the temperature detection element and the heating element, a part of the heat of the heating element will be carried away by the fluid, causing the temperature of the heating element to drop. By automatically adjusting the heating power of the heating element, the temperature difference between the temperature detection element and the heating element is kept constant. The faster the fluid flow rate, the more heat is carried away, and the greater the heating power of the heating element. Thus, the mass flow rate of the fluid can be measured through the functional relationship between the fluid flow rate and the increase in the heating power of the heating element.

[0005] During the process of measuring the mass flow rate of the fluid, the heating element and the temperature detection element are inserted into the pipeline to measure the fluid flow rate. In order to protect the heating element and the temperature detection element from being damaged during installation and operation, a mechanical protection device is provided around the heating element and the temperature detection element. However, the additional mechanical protection device has a negative impact on fluid dynamics, which will cause turbulence that changes with the fluid velocity and pressure changes, and further leads to measurement uncertainty. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide a thermal mass flowmeter probe that can improve the measurement accuracy.

[0007] To solve the above technical problems, the present invention provides a thermal mass flowmeter probe, which includes a hollow outer shell, a heating element with temperature detection function, and a temperature detection element; the outer shell is connected to the end of the connecting shaft of the thermal mass flowmeter for installing the thermal mass flowmeter probe; the heating element is arranged at the lower end inside the outer shell, and its lower end face is in the same plane as the lower end face of the outer shell and perpendicular to the axial direction of the connecting shaft; the temperature detection element is arranged inside the outer shell and is thermally isolated from the heating element.

[0008] A further technical solution thereof is: the temperature detection element is arranged at the lower end inside the outer shell, and its lower end face is in the same plane as the lower end face of the outer shell.

[0009] A further technical solution thereof is: heat insulation material is filled between the heating element and the temperature detection element, and the thermal conductivity of the heat insulation material < 1.0 W / m·K.

[0010] A further technical solution thereof is: the heating element includes a first substrate and a heater attached to the back of the first substrate, and the front surface of the first substrate constitutes the lower end face of the heating element.

[0011] A further technical solution thereof is: the temperature detection element is arranged above the heating element inside the outer shell and is in thermal contact with the outer shell.

[0012] A further technical solution thereof is: the outer shell includes an upper shell and a lower shell connected to the lower end of the upper shell. The temperature detection element is arranged inside the upper shell and is in thermal contact with the upper shell. The thermal conductivity of the upper shell > 1.0 W / m·K. The heating element is arranged at the lower end inside the lower shell. The lower end face of the lower shell constitutes the lower end face of the outer shell. The thermal conductivity of the lower shell < 1.0 W / m·K.

[0013] A further technical solution thereof is: the temperature detection element includes a second substrate and a temperature sensor attached to the back of the second substrate, and the front surface of the second substrate constitutes the lower end face of the temperature detection element.

[0014] A further technical solution thereof is: the heater is a resistance temperature sensor.

[0015] A further technical solution thereof is: the resistance temperature sensor is a platinum resistance.

[0016] A further technical solution thereof is: the temperature sensor is a resistance temperature sensor or a digital temperature sensor.

[0017] Compared with the prior art, the heating element in the thermal mass flowmeter probe of the present invention is arranged at the lower end inside the housing, and its lower end face is perpendicular to the axial direction of the connecting shaft. When the thermal mass flowmeter probe is vertically inserted into the fluid pipeline, the lower end face where the heating element is located is parallel to the flow direction of the measured medium, and the fluid can flow on the lower end face of the heating element. Therefore, while the heating element is well protected, it can also have good thermal contact with the fluid, thereby improving the measurement accuracy of the thermal mass flowmeter probe. In addition, the heating element and the temperature detection element are thermally isolated, reducing the influence of the heating element on the temperature detection element, making the measurement of the fluid temperature more accurate, and thus the flow measurement more accurate. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following will briefly introduce the drawings required for use in the embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0019] Figure 1 Schematic perspective view of the first embodiment of the thermal mass flowmeter probe of the present invention;

[0020] Figure 2 Exploded structural view of the first embodiment of the thermal mass flowmeter probe of the present invention;

[0021] Figure 3 Cross-sectional view of the first embodiment of the thermal mass flowmeter probe of the present invention;

[0022] Figure 4 Schematic perspective view of the second embodiment of the thermal mass flowmeter probe of the present invention;

[0023] Figure 5 Exploded structural view of the second embodiment of the thermal mass flowmeter probe of the present invention;

[0024] Figure 6 Cross-sectional view of the second embodiment of the thermal mass flowmeter probe of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0025] To enable those of ordinary skill in the art to more clearly understand the purpose, technical solutions, and advantages of the present invention, the following further elaborates on the present invention in conjunction with the drawings and embodiments.

[0026] Refer to Figures 1 to 3 , Figures 1 to 3The first embodiment of the thermal mass flowmeter probe of the present invention is shown. In the embodiment shown in the attached drawings, the thermal mass flowmeter probe 100 is arranged at the end of the connecting shaft 200 that can be inserted into the fluid pipeline. The thermal mass flowmeter probe 100 includes a hollow outer shell 30, a heating element 10 with temperature detection function, and a temperature detection element 20 thermally isolated from the heating element 10. The outer shell 30 is connected to the end of the connecting shaft 200 of the thermal mass flowmeter for installing the thermal mass flowmeter probe; the heating element 10 is arranged at the lower end inside the outer shell 30, and its lower end face is in the same plane as the lower end face of the outer shell 30 and is axially perpendicular to the connecting shaft 200; the temperature detection element 20 is arranged at the lower end inside the outer shell 30, and its lower end face is in the same plane as the lower end face of the outer shell 30 and is axially perpendicular to the connecting shaft 200.

[0027] The connection of the thermal mass flowmeter probe 100 to the controller and the technical solution of how to achieve flow detection both belong to the prior art and will not be elaborated here. The lower end faces of the heating element 10 and the temperature detection element 20 are both axially perpendicular to the connecting shaft 200, indicating that the lower end faces of the heating element 10 and the temperature detection element 20 are both perpendicular to the central axis 101 of the connecting shaft 200.

[0028] Based on the above design, the heating element 10 and the temperature detection element 20 of the thermal mass flowmeter probe in the present invention are both arranged at the lower end inside the outer shell 30 and the lower end faces are axially perpendicular to the connecting shaft 200. When the thermal mass flowmeter probe is vertically inserted into the fluid pipeline, the lower end face where the heating element 10 is located is parallel to the flow direction of the measured medium, and the fluid can flow on the lower end faces of the heating element 10 and the temperature detection element 20. Therefore, while the heating element 10 and the temperature detection element 20 are well protected, they can also have good thermal contact with the fluid, thereby improving the measurement accuracy of the thermal mass flowmeter probe 100. In addition, the heating element 10 and the temperature detection element 20 are thermally isolated, reducing the influence of the heating element 10 on the temperature detection element 20, making the measurement of the fluid temperature more accurate, and thus the flow measurement more accurate.

[0029] The heating element 10 and the temperature detection element 20 are arranged side by side at the lower end of the housing 30. The heating element 10 includes a first substrate 11 and a heater 12 attached to the back surface of the first substrate 11. The heater 12 can be a heater with temperature detection function in the prior art, and such heaters are commercially available, so they will not be elaborated herein. The front surface of the first substrate 11 constitutes the lower end surface of the heating element 10. The temperature detection element 20 includes a second substrate 21 and a temperature sensor 22 attached to the back surface of the second substrate 21. The front surface of the second substrate 21 constitutes the lower end surface of the temperature detection element 20. Preferably, the thermal conductivity of the first substrate 11 and the second substrate 21 > 1.0 W / m·K, that is, carrier materials with high thermal conductivity can be selected for preparation, such as ceramics (such as alumina or aluminum nitride ceramics) or aluminum and other materials.

[0030] In some embodiments, the heater 12 is a resistance temperature sensor, and the temperature sensor 22 is a resistance temperature sensor or a digital temperature sensor. Preferably, the resistance temperature sensor is a platinum resistance, and the platinum resistance can be a chip platinum resistance, a thick film platinum resistance or a thin film platinum resistance.

[0031] In some embodiments, an insulating material is filled between the heating element 10 and the temperature detection element 20, and the thermal conductivity of the insulating material < 1.0 W / m·K. In this embodiment, the insulating material is selected as epoxy resin.

[0032] In some embodiments, the connecting shaft 200 and the housing 30 are both prepared from materials with a high thermal conductivity of thermal conductivity > 1.0 W / m·K, for example, prepared from metal materials. The heating element 10 and the temperature detection element 20 are both thermally isolated from the housing 30. Specifically, thermal isolation between the housing 30 and the heating element 10 and the temperature detection element 20 can be achieved by potting, or an insulating component with a thermal conductivity < 1.0 W / m·K is provided between the housing 30 and the heating element 10 and the temperature detection element 20. Preferably, the connecting shaft 200 and the housing 30 are integrally formed.

[0033] Continue to refer to Figure 2 and Figure 3In this embodiment, an adapter board 40 is provided within the housing 30. Several conductive pins 41 are plugged into the adapter board 40. One end of each of the conductive pins 41 is connected to the heater 12 and / or the temperature sensor 22, and the other end is connected to the controller via leads. It is understood that when both the heater 12 and the temperature sensor 22 are resistance temperature sensors, the conductive pins 41 are connected to the heater 12 and the temperature sensor 22, and the conductive pins 41 are then electrically connected to the controller via leads. When the temperature sensor 22 is a digital temperature sensor, the digital temperature sensor is directly electrically connected to the controller via leads. In this embodiment, the heater 12 and the temperature sensor 22 are welded and fixed by the adapter board 40, and information detected by the heater 12 or the temperature sensor 22 is transmitted to the controller via the conductive pins 41. The adapter board 40 in this embodiment facilitates circuit connection between the controller and the heater 12 and the temperature sensor 22.

[0034] Reference Figures 4 to 6 , Figures 4 to 6 A second embodiment of a thermal mass flowmeter probe according to the present invention is illustrated. In the embodiment shown in the accompanying drawings, a thermal mass flowmeter probe 100 is disposed at the end of a connecting shaft 200 that can be inserted into a fluid pipeline. The thermal mass flowmeter probe 100 includes a hollow housing 30, a heating element 10 with a temperature sensing function, and a temperature sensing element 20 thermally isolated from the heating element 10. The housing 30 is connected to the end of the connecting shaft 200 of the thermal mass flowmeter for mounting the thermal mass flowmeter probe. The heating element 10 is disposed at the lower end of the housing 30, with its lower end surface coplanar with the lower end surface of the housing 30 and axially perpendicular to the connecting shaft 200. The temperature sensing element 20 is disposed within the housing 30, above the heating element 10, and in thermal contact with the housing 30.

[0035] The housing 30 includes an upper housing 31 and a lower housing 32 connected to the lower end of the upper housing 31. The temperature detection element 20 is disposed inside the upper housing 31 and in thermal contact with the upper housing 31. The upper housing 31 is made of a material with a high thermal conductivity of >1.0 W / m·K, for example, a metal material. The lower housing 32 is made of a material with a thermal conductivity of <1.0 W / m·K. The heating element 10 is disposed at the lower end of the lower housing 32. The lower end surface of the heating element 10 is in the same plane as the lower end surface of the lower housing 32 and is axially perpendicular to the lower housing 32. The lower end surface of the lower housing 32 constitutes the lower end surface of the housing 30.

[0036] The connection between the thermal mass flowmeter probe 100 and the controller and the technical solution for realizing flow detection both belong to the prior art and will not be elaborated here. The lower end face of the heating element 10 is axially perpendicular to the connecting shaft 200, indicating that the lower end face of the heating element 10 is perpendicular to the central axis 101 of the connecting shaft 200.

[0037] Based on the above design, the heating element 10 of the thermal mass flowmeter probe in the present invention is arranged at the inner lower end of the housing 30 and the lower end face is axially perpendicular to the connecting shaft 200. When the thermal mass flowmeter probe is vertically inserted into the fluid pipeline, the lower end face where the heating element 10 is located is parallel to the flow direction of the measured medium, and the fluid can flow on the lower end face of the heating element 10. Therefore, while the heating element 10 is well protected, it can also have good thermal contact with the fluid, thereby improving the measurement accuracy of the thermal mass flowmeter probe 100. In addition, the temperature detection element 20 is arranged above the heating element 10 to achieve thermal isolation between the two, reducing the influence of the heating element 10 on the temperature detection element 20, making the measurement of the fluid temperature more accurate, and thus the flow measurement more accurate.

[0038] The heating element 10 includes a first substrate 11 and a heater 12 attached to the back of the first substrate 11. The heater 12 can be a heater with temperature detection function in the prior art, and such heaters can be obtained in the commercial market and will not be elaborated here. The front surface of the first substrate 11 constitutes the lower end face of the heating element 10; the temperature detection element 20 includes a second substrate 21 and a temperature sensor 22 attached to the back of the second substrate 21. The front surface of the second substrate 21 constitutes the lower end face of the temperature detection element 20. Preferably, the thermal conductivity coefficients of the first substrate 11 and the second substrate 21 are > 1.0 W / m·K, that is, the first substrate 11 and the second substrate 21 can be prepared from carrier materials with high thermal conductivity coefficients, such as ceramics (such as alumina or aluminum nitride ceramics) or aluminum and other materials.

[0039] In some embodiments, the heater 12 is a resistance temperature sensor, and the temperature sensor 22 is a resistance temperature sensor or a digital temperature sensor. Preferably, the resistance temperature sensor is a platinum resistance, and the platinum resistance can be a surface-mounted platinum resistance, a thick-film platinum resistance or a thin-film platinum resistance.

[0040] In some embodiments, the connecting shaft 200 and the upper housing 31 are made of metal materials, the connecting shaft 200 and the upper housing 31 are integrally formed, and the upper housing 31 is threadedly connected to the lower housing 32.

[0041] In some embodiments, the shape of the first substrate 11 is a centrally symmetric figure (such as a rectangle, a rhombus, a square, a circle, etc.), so that the measurement error caused by the installation rotation angle can be eliminated or greatly reduced, which is convenient for installation and improves the measurement repeatability.

[0042] The above are only the preferred embodiments of the present invention, and do not impose any formal restrictions on the present invention. Those skilled in the art can make various equivalent changes and improvements on the basis of the above embodiments. Any equivalent changes or modifications made within the scope of the claims shall fall within the protection scope of the present invention.

Claims

1. A thermal mass flowmeter probe, characterized in that, The thermal mass flowmeter probe includes: A hollow housing for installing the thermal mass flowmeter probe, which is connected to the end of the connecting shaft of the thermal mass flowmeter; A heating element with temperature detection function, arranged at the lower end inside the housing, and its lower end face is in the same plane as the lower end face of the housing and perpendicular to the axial direction of the connecting shaft; A temperature detection element, arranged inside the housing and thermally isolated from the heating element, the temperature detection element is located above the heating element and in thermal contact with the housing; The housing includes an upper shell and a lower shell connected to the lower end of the upper shell. The temperature detection element is arranged inside the upper shell and in thermal contact with the upper shell. The thermal conductivity of the upper shell > 1.0 W / m·K. The heating element is arranged at the lower end inside the lower shell. The lower end face of the lower shell constitutes the lower end face of the housing. The thermal conductivity of the lower shell < 1.0 W / m·K; The heating element includes a first substrate and a heater attached to the back of the first substrate. The front face of the first substrate constitutes the lower end face of the heating element.

2. The thermal mass flowmeter probe according to claim 1, wherein The temperature detection element includes a second substrate and a temperature sensor attached to the back of the second substrate. The front face of the second substrate constitutes the lower end face of the temperature detection element.

3. The thermal mass flowmeter probe according to claim 1, characterized in that, The heater is a resistance temperature sensor.

4. The thermal mass flowmeter probe according to claim 3, wherein, The resistance temperature sensor is a platinum resistance.

5. The thermal mass flowmeter probe according to claim 2, wherein: The temperature sensor is a resistance temperature sensor or a digital temperature sensor.

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