JP7489012B2 - Fluid temperature measuring device and protective tube used therein - Google Patents

Description

The present invention relates to a temperature measuring device that is installed in a fluid flow path such as a pipe to measure the temperature of the fluid, and a protective tube used therein.

Conventionally, this type of temperature measurement device has a structure in which a hollowed-out protective tube called a thermowell is inserted into the fluid flow path through a support tube attached to a mounting hole drilled in the side wall of the pipe, and a thermometer is installed inside the protective tube (see, for example, Patent Document 1). The protective tube exposed to the fluid is constantly vibrating due to the generation of Karman vortices on the downstream side, and when the vibration frequency approaches the natural frequency of the protective tube, resonance occurs and the tube swings wildly. As a result, there is a risk that the tube will interfere with the external support tube and be damaged, or that the internal thermometer will interfere with the inner surface of the protective tube and be damaged.

To avoid this resonance phenomenon of the protective tube, it is necessary to design the protective tube so that its natural frequency is large when it is installed, and to reduce (generally less than 0.8) the ratio of the frequency caused by Karman vortices to the above-mentioned natural frequency (frequency caused by Karman vortices / natural frequency of the protective tube). For example, it is effective to shorten the insertion length (amount of protrusion) of the protective tube into the fluid flow path, but a shorter insertion length will also affect the temperature measurement.

The applicant has previously proposed a protective tube that can be easily attached to the support tube on-site, that can reliably achieve the effect of preventing the occurrence of resonance by increasing the natural frequency with the collar (contact piece), and that does not require precise control of the dimensional accuracy of the fit between the contact piece and the support tube (see Patent Document 1). However, in this case, problems may arise due to the combination with the support tube and wear of the collar, depending on the usage conditions.

JP 2010-107430 A

In view of the above situation, the present invention aims to provide a temperature measuring device that can suppress the occurrence of Karman vortices downstream of the protective tube, thereby preventing flow-induced vibration of the protective tube and damage to the thermometer inside.

In light of this current situation, the inventors conducted extensive research and discovered that Karman vortices occur regularly from the separation point of the boundary layer distribution of the flow that occurs around the protective tube due to the pressure difference of the flow, but that if the position of this separation point can be made variable, the movement of the separated fluid becomes unstable, the negative pressure area that occurs downstream of the protective tube becomes smaller, and Karman vortices become less likely to occur, which led to the completion of this invention.

That is, the present invention includes the following inventions.
(1) A device for measuring the temperature of a fluid, comprising a protective tube attached to a fluid flow path and a thermometer inserted into the protective tube, wherein the protective tube comprises a cylindrical tube body with a closed tip and a pressure-receiving member supported on the outer circumferential surface of the tube body so as to be rotatable around the axis of the tube body, and the presence of the pressure-receiving member forms an uneven shaped region on the outer circumferential surface of the protective tube in the circumferential direction.

(2) The temperature measuring device according to (1), in which the pressure-receiving member is composed of a cylindrical body supported rotatably on the outer surface of the tube body and a protrusion protruding from the outer periphery of the cylindrical body, and the uneven shape is formed by the protrusion protruding outward.

(3) The temperature measuring device according to (1) or (2), in which the pressure-receiving member has convex fins extending in the axial direction or in a diagonal direction inclined from the axial direction, and the uneven shape is formed by the fins protruding outward.

(4) The temperature measuring device according to (3), wherein a plurality of the fins are provided at intervals in the circumferential direction.
(5) The temperature measuring device according to any one of (1) to (4), wherein the pressure-receiving member is rotatably supported on the outer circumferential surface of the tube main body via a bearing member.

A protective tube used in a fluid temperature measuring device according to any one of (1) to (5), characterized in that the protective tube comprises a cylindrical tube body with a closed tip, and a pressure-receiving member supported on the outer circumferential surface of the tube body so as to be rotatable about the axis of the tube body, and the presence of the pressure-receiving member forms an uneven shaped region on the outer circumferential surface.

According to the temperature measuring device of the present invention described above, the pressure-receiving member with the uneven shaped area rotates in response to the flow of fluid, irregularly disturbing the separated fluid flow and suppressing the generation of Karman vortices downstream of the protective tube, thereby preventing flow-induced vibration of the protective tube and damage to the thermometer inside.

1 is a perspective view showing a temperature measuring device according to a representative embodiment of the present invention. FIG. 4 is an explanatory diagram showing a protective tube and a thermometer inserted into the protective tube, which constitute the temperature measuring device. FIG. FIG. 4 is an explanatory diagram showing the tip portion of the temperature measuring device. 5 is a cross-sectional view taken along line AA in FIG. 4 . FIG. 11 is an explanatory diagram showing a modified example of the temperature measuring device according to the present invention. FIG. 13A is an explanatory diagram showing another modified example of the temperature measuring device, FIG. 13B is a cross-sectional view taken along the line BB of FIG. 13A, and FIG. 13C is a cross-sectional view showing yet another modified example. FIG. 11 is an explanatory diagram showing still another modified example of the temperature measuring device. Appearance photographs of each sample of Example 1 and Comparative Example 1 Photographs showing the state of the liquid surface after Example 1 and Comparative Example 1 were moved.

Next, an embodiment of the present invention will be described in detail with reference to the attached drawings.

As shown in Figs. 1 and 2, the temperature measuring device 1 of the present invention measures the temperature of a fluid and is composed of a protective tube 2 attached in a state where it protrudes into the fluid flow path, and a thermometer 3 inserted into the protective tube 2. For the thermometer 3, a wide variety of conventional thermometers can be used, such as a sheathed thermocouple or a sheathed resistance thermometer.

The protective tube 2 is composed of a cylindrical tube body 4 with a closed tip, and a pressure-receiving member 5 supported on the outer circumferential surface of the tube body 4 so as to be rotatable around the axis of the tube body 4. Both the tube body 4 and the pressure-receiving member 5 are made of stainless steel, which is heat-resistant and corrosion-resistant, but are not limited to this.

Due to the presence of this pressure-receiving member 5, an unevenly shaped region R1 is formed on the outer circumferential surface of the protective tube 2 in the circumferential direction. In other words, the unevenly shaped region R1 rotates as the pressure-receiving member 5 rotates. By providing this rotating unevenly shaped region R1, the temperature measuring device 1 of the present invention makes the flow of the fluid to be measured irregular, preventing vibration of the protective tube 2 due to the generation of Karman vortices.

The tube body 4 is a tubular member whose tip is sealed and whose internal space is isolated from the outside except for the opening on the base end side so that the thermometer 3 inside is not exposed to the fluid. In this example, the outer peripheral surface has a circular circumferential surface shape in cross section overall, but this is not limited to this as long as it can rotatably support the pressure-receiving member 5. A male screw portion 41 is provided on the outer peripheral surface of the base end 4b of the tube body 4, which screws into a mounting hole formed in the tube wall or the like that serves as the fluid flow path, and a female screw groove 42 is provided on the inner peripheral surface of the base end opening into which the male screw portion 31 of the base end of the thermometer 3 screws.

The pressure-receiving member 5 is composed of a cylindrical body 50 that is rotatably supported on the outer surface of the tube body 4, and a protrusion 51 that protrudes from the outer periphery of the cylindrical body 50. The outwardly protruding protrusion 51 and the outer periphery of the cylindrical body 50 form the uneven region R1 described above.

The cylindrical body 50 is a stainless steel cylindrical member, and both ends 50a, 50b are rotatably supported on the outer circumferential surface 40 of the tube body 4 via bearing members 6. The bearing members 6 are rolling bearings, particularly ball bearings that can stably support the cylindrical body 50 in the axial direction as well as the radial direction. Reference numerals 7A, 7B denote ring-shaped retaining members that abut and position the bearing members 6, and are fixed to a predetermined axial position on the outer circumferential surface 40 of the tube body 4 by set screws 70.

By changing the positions of the pressing members 7A and 7B, it is possible to change the axial position of the pressure-receiving member 5 as appropriate. However, taking into consideration the efficiency of heat transfer to the thermometer 3, it is preferable to set the axial position of the pressure-receiving member 5 so that the tip 4a of the tube body 4, which corresponds to the position of the thermometer tip 3a where the temperature measuring part of the thermometer 3 is located, protrudes from the pressure-receiving member 5 toward the tip side.

In this embodiment, the cylindrical body 50 is configured to be able to rotate smoothly relative to the tube body 4 by the bearing member 6, but it is of course also possible to omit the bearing member 6 and have the tube body 4 directly fitted loosely within the cylindrical body 50 by reducing the gap between the cylindrical body 50 and the tube body 4. Also, instead of the base end side pressing member 7B, a locking protrusion that can also abut and stop the bearing member 6 may be provided on the outer circumferential surface of the tube body 4.

The protrusions 51 are preferably fins with convex stripes extending in the axial direction or in a diagonal direction inclined from the axial direction. In particular, in this example, they are corrugated fins extending in the axial direction, and a plurality of these corrugated fins (protrusions 51) are provided on the outer circumferential surface of the cylindrical main body 50 at predetermined intervals in the circumferential direction, and the corrugated fins and the outer circumferential surface of the cylindrical main body 50 form the uneven region R1.

In addition to the convex portions 51 being continuous in the axial direction as in this example, multiple convex portions 51 may be provided at intervals in the axial direction as shown in FIG. 6. They may be other than convex fins, for example, they may be provided with multiple dome-shaped protrusions.

Also, as shown in Figures 7(a) and (b), instead of providing a convex portion 51, a concave portion 52 (in this example, a concave groove with a bottom) may be provided on the outer peripheral surface of the cylindrical body 50, and this may be used as the pressure-receiving member 5. The presence of such a pressure-receiving member 5 forms an unevenly shaped region R1 on the outer peripheral surface of the protective tube 2. The unevenly shaped region R1 formed of such a concave portion 52 can also rotate the pressure-receiving member 5 in response to the flow of fluid, irregularly disrupting the flow of fluid.

Furthermore, the pressure-receiving member 5 may be formed by penetrating the recesses 52 in Figs. 7(a) and (b), and instead of being cylindrical, the cylindrical body 50 may be formed as a fence-like tube consisting of annular members at both ends and multiple connecting rods extending in the axial direction that connect them, as shown in Fig. 7(c). With such a pressure-receiving member 5, an uneven region R1 is formed on the outer circumferential surface of the protective tube 2, and the pressure-receiving member 5 can be rotated in response to the flow of fluid, causing irregular disturbance to the flow of fluid.

As shown in Figure 8, a preferred embodiment is one in which multiple independently rotating pressure-receiving members 5 are connected in the axial direction. In this case, the uneven region R1 formed on the outer circumferential surface of the protective tube 2 is composed of multiple divided regions R2 that rotate independently, so that each divided region R2 is more likely to rotate in response to the flow of fluid, and the flow of fluid can be more effectively disturbed.

The above describes the embodiments of the present invention, but the present invention is not limited to these examples, and can of course be embodied in various forms without departing from the spirit of the present invention.

Next, we will explain the results of an experiment in which samples of Example 1, which is a protective tube for a temperature measuring device according to the present invention, and Comparative Example 1, which is a conventional protective tube that does not rotate and has no uneven shaped areas, were moved through a liquid at a constant speed in a lateral direction perpendicular to the axis to confirm whether or not a Karman vortex was formed downstream.

(sample)
Fig. 9(a) is a photograph of the appearance of Example 1, and Fig. 9(b) is a photograph of the appearance of Comparative Example 1. Example 1 has substantially the same structure as the structure shown in the representative embodiment of Figs. 1 to 5, except that the convex portion 51 is a flat convex strip extending in an oblique direction.

Specifically, a cylindrical body with an outer diameter of 16 mm and a length of 100 mm is attached to the outer surface of a tube body with a sealed end with an outer diameter of 10 mm and a length of 250 mm, and a pressure-receiving member consisting of four flat convex portions with a height of 15 mm, a thickness of 1 mm and a length of 80 mm, protruding from the outer surface at intervals in the circumferential direction, the pressure-receiving member being rotatably attached around the axis. The sample of Comparative Example 1 has a structure consisting of only the tube body of Example 1, and is a tube body with an outer diameter of 10 mm and a length of 250 mm, and a sealed end. There are no irregularities on the outer surface, and no rotatable pressure-receiving member exists.

(experimental method)
Two containers measuring 330 mm in length, 1000 mm in width, and 190 mm in height were prepared, and a predetermined liquid (a mixture of 15 liters of water (tap water), 3.75 liters of laundry starch, and 0.12 liters of paint (silver)) was placed into each container. Example 1/Comparative Example 1 were each held by the base end in the hand and immersed vertically about 50 mm from the tip into the liquid, and moved laterally at a constant speed of about 30 cm/sec while maintaining this immersion depth and posture.

(Experimental result)
10(a) and (b) are photographs showing the state of the liquid surface after the movement of Example 1 and Comparative Example 1, respectively. In Comparative Example 1, it can be seen that Karman vortexes are generated as shown in Fig. 10(b). In contrast, in Example 1, it can be seen that the vortexes and flow on the downstream side are disturbed, and the generation of Karman vortexes is suppressed.

It was also confirmed that the pressure-receiving member rotated slightly during the experiment in Example 1 in conjunction with the above movement. From these experimental results, it can be seen that the pressure-receiving member with the uneven shaped area rotates in response to the flow of fluid, irregularly disrupting the flow of fluid and suppressing the generation of Karman vortices downstream of the protective tube.

REFERENCE SIGNS LIST 1 Temperature measuring device 2 Protective tube 3 Thermometer 3a Tip portion 4 Tube body 4a Tip portion 4b Base end portion 5 Pressure receiving member 6 Bearing member 7A, 7B Pressing member 31 Male thread portion 40 Outer circumferential surface 41 Male thread portion 42 Female thread groove 50 Cylindrical body 50a, 50b End portion 51 Convex portion 52 Concave portion 70 Setscrew R1 Concave-convex region R2 Divided region

Claims (6)

A fluid temperature measuring device comprising a protective tube attached to a fluid flow path and a thermometer inserted into the protective tube,
The protective tube is
A cylindrical tube body with a closed tip;
a pressure-receiving member supported on the outer circumferential surface of the pipe body so as to be rotatable about the axis of the pipe body;
A temperature measuring device characterized in that, due to the presence of the pressure-receiving member, an uneven shaped region is formed along the circumferential direction on the outer circumferential surface of the protective tube. the pressure-receiving member is composed of a cylindrical body rotatably supported on the outer surface of the pipe body and a protrusion provided on an outer periphery of the cylindrical body,
2. The temperature measuring device according to claim 1, wherein the uneven shape is formed by the convex portions projecting outward . The pressure-receiving member includes a convex fin extending in an axial direction or in an oblique direction inclined from the axial direction,
3. The temperature measuring device according to claim 1, wherein the uneven shape is formed by the outwardly protruding fins. The temperature measuring device according to claim 3, wherein the fins are provided in a plurality of circumferentially spaced locations. The temperature measuring device according to any one of claims 1 to 4, wherein the pressure-receiving member is rotatably supported on the outer circumferential surface of the tube body via a bearing member. A protective tube for use in the fluid temperature measuring device according to any one of claims 1 to 5,
A cylindrical tube body with a closed tip;
a pressure-receiving member supported on the outer circumferential surface of the pipe body so as to be rotatable about the axis of the pipe body;
A protective tube characterized in that due to the presence of the pressure-receiving member, an uneven region is formed on the outer circumferential surface along the circumferential direction.

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