JP3785016B2 - Thermal conductivity measuring device - Google Patents

Description

【００２３】
前述したように、熱伝導率の測定に際には流れにより持ち去られる熱量が少ないことが重要なので、熱伝導率センサ１０，１１０上の流速は遅いほどよい。また、速い応答速度での測定が求められので、サンプル到達時間は短いほどよい。表１から分かるように、図８に示した従来の熱伝導率測定装置では、図７に示した従来の熱伝導率測定装置と比較して、熱伝導率センサ１１０上の流速は改善されたが、その代わりにサンプル到達時間が長くなった。これに対して、図１に示した熱伝導率測定装置によれば、サンプル到達時間を維持しつつ、熱伝導率センサ１０上の流速を改善することができる。また、図４に示した熱伝導率測定装置によれば、図１に示した熱伝導率測定装置よりも、熱伝導率センサ１０上の流速およびサンプル到達時間の両方を更によくすることができる。つまり、図１，図４に示した熱伝導率測定装置によれば、熱伝導率センサ１０上の流速とサンプル到達時間との両方を両立できると言える。
【００２４】
（参考例）
図６は、本発明による熱伝導率測定装置に関連する参考例の構成を示す断面図である。ここで、図６（Ａ）は流路４４の軸方向を含む断面を示しており、図６（Ｂ）は図６（Ａ）におけるVIB−VIB′線方向の断面を示している。図６において、図１，図４と同一部分を同一符号をもって示し、適宜その説明を省略する。
図１，図４に示した熱伝導率測定装置は流路ブロック１ａ，１ｂにキャビティ５ａ，５ｂが形成された構成となっているが、図６に示した熱伝導率測定装置は流路４４内にキャビティ４５が設けられた構成となっている。
【００２５】
このキャビティ４５は、上面が開口された円筒状の容器４２と、この容器４２内に挿入されたキャンケース２１とにより構成されている。キャンケース２１上には熱伝導率センサ１０が配置されており、容器４２の開口された面には焼結金属板３３がはめ込まれている。容器４２は焼結金属板３３がはめ込まれた面が流路４４の上流側に向くように流路４４内に配置され、流路ブロック４１の内壁に固定された支持部材４３により支えられている。
焼結金属板３３は図４に示した金網３２と同様の機能を有するものである。つまり、流路４４内の流体とキャビティ４５内の流体とは、焼結金属板３３を介して分子拡散のみにより交換される。このため、流路４４内の流れ４６が焼結金属板３３と直交していても、流路４４内の流れ４６によってキャビティ４５内に強制対流は生じない。よって、図６に示した熱伝導率測定装置でも、図４に示した熱伝導率測定装置と同程度の測定精度および応答速度を得ることができる。
【００２６】
前述したように、流路４，４４とキャビティ５ａ，５ｂ，４５との境界に金網３１，３２または焼結金属板３３を設けることが本発明の特徴である。しかし、流路４，４４内の流体の流れ６，４６がキャビティ５ａ，５ｂ，４５内に及ぼす影響を低減する効果が得られればよいので、流路４，４４とキャビティ５ａ，５ｂ，４５との境界に配置するものは、多くの孔がある多孔体であればよい。この多孔体としては、金網３１，３２および焼結金属板３３の他に、テフロン等の樹脂網、パンチングプレート、多孔質セラミック板などを使用できる。
また、多孔体に関しては、キャビティ５ａ，５ｂ，４５内の流れを遅くするために、孔の径が小さいことが望ましい。また、キャビティ５ａ，５ｂ，４５内の流体の置換を速く行えるように、単位面積当たりの孔数が多く、孔の深さが浅いことが望ましい。
【００２７】
また、本発明でいう流体とは気体と液体の総称であり、本発明による熱伝導率測定装置では気体および液体のいずれに対しても効果が得られるが、特に液体に対する効果が大きい。
なお、特開平５−２３２０５２号公報には、センサの上流側または下流側に金網を設けて、センサ上の流速を遅くするという技術が開示されている。しかし、この技術は、金網の設けられている場所が流路とキャビティの境界ではなく、流路の途中である点で、本発明と構成が異なる。また、流速が遅くなると言っても、結局はセンサ上の一定方向の流れはなくならないという点で、作用効果が異なるものである。したがって、上記公報は、本発明の進歩性を否定する資料とはなり得ない。
【００２８】
【発明の効果】
以上説明したように、本発明による熱伝導率測定装置では、流路ブロックに形成されたキャビティの流路への開口部に多孔体が設けられている。この多孔体により流速が低減されるので、キャビティの深さを深くせずに、熱伝導率センサ上の流れを遅くすることができる。したがって、応答速度を維持しつつ、測定精度を高めることができる。また、熱伝導率センサ上では大きな渦状の流れがなく、流速が変化するということもないので、測定の安定性がよくなる。
【００２９】
また、流路内の流体とキャビティ内の流体とが分子拡散のみにより交換されるように多孔体を設計することにより、熱伝導率センサを多孔体に近接配置しても、熱伝導率センサは強制対流による影響を受けずに精度よく測定することができる。この場合、応答速度を極めて速くすることができる。また、このように設計された多孔体を使用すれば、流路の流速が変化しても強制対流による影響をほとんど受けずに測定を行えるので、流量制御を厳密に行う必要がないという効果も得られる。
【図面の簡単な説明】
【図１】 本発明による熱伝導率測定装置の第１の実施の形態の構成を示す断面図である。
【図２】 発熱抵抗式熱伝導率センサの構造を示す斜視図である。
【図３】 図１に示した金網付近の流体の挙動を示す模式図である。
【図４】 本発明による熱伝導率測定装置の第２の実施の形態の構成を示す断面図である。
【図５】 図４に示した金網付近の流体の挙動を示す模式図である。
【図６】 本発明による熱伝導率測定装置に関連する参考例の構成を示す断面図である。
【図７】 従来の熱伝導率測定装置の一構成例を示す断面図である。
【図８】 従来の熱伝導率測定装置の他の構成例を示す断面図である。
【符号の説明】
１，１ａ，１ｂ，４１…流路ブロック、２ａ，２ｂ…貫通孔、３…窪み、４，４４…流路、５ａ，５ｂ，４５…キャビティ、６，４６…流路内の流体の流れ、７…渦、８…分子拡散、１０…発熱抵抗式熱伝導率センサ、１１…基台、１２…メンブレン、１３…スリット、１４…発熱体、１５ａ，１５ｂ…電極パッド、２１…キャンケース、２２…ステンレスの支持板、２３ａ，２３ｂ…リードピン、３１，３２…金網、３１ａ，３２ｂ…網目、３３…焼結金属板、４２…容器、４３…支持部材。[0001]
BACKGROUND OF THE INVENTION
TECHNICAL FIELD The present invention relates to a thermal conductivity measuring apparatus for retaining a fluid guided by a flow path in a cavity and measuring the thermal conductivity of the fluid with a sensor disposed in the cavity, and more particularly to a fluid around the sensor. The present invention relates to a thermal conductivity measuring device provided with a means for optimizing the behavior of the heat.
[0002]
[Prior art]
This type of thermal conductivity measuring device is used for adjusting the amount of heat when supplying LNG (liquefied natural gas), for example, utilizing the fact that the amount of heat per unit volume is proportional to the thermal conductivity.
FIG. 7 is a cross-sectional view showing a configuration example of a conventional thermal conductivity measuring device. In this thermal conductivity measuring device, the flow path 104 is constituted by the inner walls of the flow path blocks 101 and 101a, and the cavity 105a is constituted by a depression formed on the inner wall of the flow path block 101a. The depth of the cavity 105a is, for example, about 10 mm.
[0003]
A heating resistance thermal conductivity sensor 110 is disposed at the bottom of the cavity 105a. The heating resistance type thermal conductivity sensor 110 has a heating element (not shown). This heating element is driven at a constant temperature by a control circuit (not shown). Since the energy deprived from the heating element changes corresponding to the thermal conductivity of the fluid to be measured, the thermal conductivity of the fluid to be measured can be obtained by obtaining the supply energy required to maintain the constant temperature from the voltage value change, etc. Can be measured.
[0004]
When measuring the thermal conductivity, the heat deprived from the heating element of the thermal conductivity sensor 110 is based on (1) heat escaping to the fluid by thermal conduction (heat propagation by molecular motion) and (2) forced convection. It consists of the sum of heat carried away by the flow of fluid and (3) other heat (radiation heat, heat escaping to a device such as the base of the thermal conductivity sensor 110). Among these, the heat related to the thermal conductivity of the fluid is only (1) the heat that escapes to the fluid by heat conduction. Therefore, in order to measure the thermal conductivity with high accuracy, it is desirable to perform the measurement in a state in which the heat other than this, particularly the heat removed by the flow (2) is zero. That is, it is desirable to measure the thermal conductivity in a state where the fluid is stationary (a state where the flow velocity is zero).
[0005]
However, in the thermal conductivity measuring apparatus shown in FIG. 7, since the depth of the cavity 105a is relatively shallow, a convection 107 having a fast flow is generated in the cavity 105a due to the fluid flow 106 in the flow path 104. (The thickness of the arrow indicating the convection 107 represents the speed of the convection 107). Therefore, since the flow on the thermal conductivity sensor 110 is fast and the heat carried away by this flow is large, the measurement accuracy of the thermal conductivity is extremely low.
[0006]
FIG. 8 is a cross-sectional view showing another configuration example of a conventional thermal conductivity measuring device. In this thermal conductivity measuring device, the depth of the cavity 105b is made deeper by D than the cavity 105a in FIG. For example, there is one in which D = 20 mm and the depth of the cavity 105b is about 30 mm. By increasing the depth of the cavity 105b, the convection 108 in the cavity 105b is delayed. Therefore, since the flow on the thermal conductivity sensor 110 becomes slow, the measurement accuracy of the thermal conductivity is increased.
[0007]
[Problems to be solved by the invention]
In the thermal conductivity measuring device used in the field of process automation such as the above-described LNG supply control, it is required to measure the thermal conductivity of the fluid to be measured that changes every moment at a high response speed. This response speed is greatly related to the sample arrival time in the cavity 105b. The “sample arrival time in the cavity 105b” is the time for the measurement target to reach the thermal conductivity sensor 110 in the cavity 105b from the opening of the cavity 105b (the boundary between the cavity 105b and the flow path 104). Say. The shorter the sample arrival time, the faster the response speed. In the case of the thermal conductivity measuring apparatus shown in FIG. 8, the depth of the cavity 105b is increased in order to increase the measurement accuracy, so that the sample arrival time becomes longer, and the response speed is higher than that of the thermal conductivity measuring apparatus shown in FIG. It was too late. As described above, the conventional technique cannot increase the measurement accuracy while maintaining the response speed.
[0008]
Note that the actual fluid flow is not as simple as indicated by the arrows. The time and path of staying in the cavities 105a and 105b are not uniform, and are gradually replaced while mixing with the fluid that originally existed. Therefore, to be precise, the sample arrival time is the time (= replacement time) until the ratio of the existing sample to the new sample reaches the predetermined value (= replacement time). I defined like this.
[0009]
The present invention has been made to solve such a problem, and an object thereof is to improve measurement accuracy while maintaining a response speed in a thermal conductivity measuring device.
[0010]
[Means for Solving the Problems]
To achieve the above object, a thermal conductivity measuring apparatus according to the present invention, a flow path block that forms a flow path for guiding the fluid, formed in the passage block so as to face the flow path and fluid retention And a heat generation type thermal conductivity sensor that is provided in the cavity and measures the thermal conductivity of the fluid, and a porous body that is provided in the opening to the flow path of the cavity . When the fluid in the flow path passes through the porous body, the flow velocity is reduced. For this reason, the flow on the sensor can be slowed down without increasing the depth of the cavity. That is, since the flow on the sensor can be slowed without increasing the sample arrival time in the cavity, the measurement accuracy can be improved while maintaining the response speed.
[0011]
The thermal conductivity measuring device according to the present invention is designed such that the porous body exchanges the fluid in the flow path and the fluid in the cavity only by molecular diffusion. If the porous body is designed in this way, the fluid flow based on forced convection is eliminated even in the vicinity of the porous body in the cavity. For this reason, even if the sensor is arranged close to the porous body, the sensor can be accurately measured without being affected by forced convection. In this case, since the sample arrival time is extremely short, the response speed can be extremely increased.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
(First embodiment)
FIG. 1 is a cross-sectional view showing a configuration of a first embodiment of a thermal conductivity measuring device according to the present invention. This figure shows a cross section including the axial direction of the flow path 4.
As shown in FIG. 1, the flow path 4 which guides the fluid is comprised by the inner wall of each flow path block 1 and 1a. A through hole 2a is formed in the flow path block 1a, and a cavity 5a is configured by the through hole 2a and the can case 21 inserted into the through hole 2a. The cavity 5 a is a space facing the flow path 4 and retains the fluid guided by the flow path 4. The cavity 5a has a depth of 5 mm. The can case 21 is made by pouring glass into a case made of Kovar.
[0013]
A heating resistance thermal conductivity sensor 10 is disposed on the can case 21 which is the bottom of the cavity 5a. The thermal conductivity sensor 10 is a sensor that measures the thermal conductivity of a fluid.
FIG. 2 is a perspective view showing the structure of the heating resistance type thermal conductivity sensor 10. A membrane 12 is formed at the center of the base 11. The lower part of the membrane 12 is hollow (not shown). The cavity inside the base 11 communicates with the outside of the base 11 through a large number of slits 13 formed in the membrane 12. A heating element 14 made of a resistor pattern is formed on the membrane 12. Electrode pads 15a and 15b are connected to both ends of the heating element 14, respectively. A thermal conductivity sensor 10 having such a structure is described in, for example, Japanese Patent Laid-Open No. 5-232052.
[0014]
Returning to the description of FIG. A stainless support plate 22 having a hole 22a through which lead pins 23a and 23b extending from the can case 21 are welded is welded to the bottom surface of the can case 21, that is, the surface continuous to the outer wall of the flow path block 1a. The electrode pads 15a and 15b of the thermal conductivity sensor 10 shown in FIG. 2 are connected to lead pins 23a and 23b, respectively, and are pulled out to the outside and connected to an external circuit (not shown).
Furthermore, a metal mesh 31 having a large number of meshes is provided at the boundary between the flow path 4 and the cavity 5a, which is a feature of the present invention. Here, “the boundary between the flow path 4 and the cavity 5a” refers to the opening of the cavity 5a. A recess 3 is formed around the through hole 2a on the inner wall side of the flow path block 1a, and a wire mesh 31 is welded to the recess 3 portion. Although FIG. 1 shows an example in which one wire mesh is installed, a plurality of wire meshes may be installed in an overlapping manner.
[0015]
FIG. 3 is a schematic diagram showing the behavior of the fluid near the wire mesh 31. This figure is an enlarged view of a portion III surrounded by a dotted line in FIG. The fluid in the flow path 4 flows into the cavity 5 a through the mesh 31 a of the metal mesh 31. For example, when the fluid is LNG and the wire mesh 31 is about 60 mesh (the number of meshes 31a per inch is 60 and the wire diameter is 0.12 mm, the length of one side of the mesh 31a is 0.3 mm). The small vortex 7 is formed near the mesh 31a in the cavity 5a by the flow force of the flow path 4. However, since the force of the vortex 7 is weak, the forced convection due to the vortex 7 hardly occurs in the cavity 5a. Accordingly, although depending on the type of fluid and the flow velocity, if the thermal conductivity sensor 10 is separated from the wire mesh 31 by about 5 to 10 mm, a flow based on forced convection hardly occurs on the thermal conductivity sensor 10.
[0016]
Therefore, the flow on the thermal conductivity sensor 10 can be slowed without increasing the depth of the cavity as in the conventional thermal conductivity measuring device shown in FIG. That is, since the flow on the thermal conductivity sensor 10 can be delayed without increasing the sample arrival time in the cavity 5a, the measurement accuracy can be increased while maintaining the response speed of the thermal conductivity measuring device.
In the conventional thermal conductivity measuring device shown in FIG. 7 or FIG. 8, there is a large vortex flow (convection 107, 108) on the thermal conductivity sensor 110, and the flow velocity is not constant. For this reason, the conventional thermal conductivity measuring device has a drawback that the measurement result is not stable. In contrast, the thermal conductivity measuring apparatus shown in FIG. 1 does not have a large vortex flow on the thermal conductivity sensor 10 and is not affected by the flow velocity, so that the measurement stability is improved. can get.
[0017]
(Second Embodiment)
FIG. 4 is a cross-sectional view showing the configuration of the second embodiment of the thermal conductivity measuring device according to the present invention. FIG. 5 is an enlarged view of a portion V surrounded by a dotted line in FIG. 4, and is a schematic diagram showing the behavior of the fluid in the vicinity of the wire mesh 32. In these drawings, the same parts as those in FIGS. 1 to 3 are denoted by the same reference numerals, and the description thereof is omitted as appropriate.
In the thermal conductivity measuring apparatus shown in FIG. 4, the wire mesh 32 is specifically designed so that the fluid in the flow path 4 and the fluid in the cavity 5 b are exchanged only by the molecular diffusion 8.
[0018]
The conditions under which the fluid is exchanged only by the molecular diffusion 8 are the viscosity / density of the fluid, the size of the molecule, the diameter / depth / shape of the mesh (hole) 32a of the wire mesh (porous body) 32, and the wire mesh (porous body) 32. Since it changes due to the unevenness of the surface, it cannot be said unconditionally.
For example, in the case of LNG whose main component is liquefied methane, if a wire mesh of 0.04 mm and a 200 mesh wire mesh (a wire mesh having 200 meshes 32a per inch) 32 is used, the length of one side of the mesh 32a Is 0.09 mm and the depth is about 0.04 mm, and fluid exchange by molecular diffusion 8 alone is possible.
In the case of gas, high accuracy can be obtained even if the exchange of fluid is not limited to molecular diffusion. However, if only molecular diffusion is used, a finer metal mesh 32 may be used than in the case of liquid.
[0019]
If the wire mesh 32 is designed in this way, the fluid flow based on forced convection is eliminated even in the vicinity of the wire mesh 32 in the cavity 5b. For this reason, even if the thermal conductivity sensor 10 is disposed close to the wire mesh 32 at a distance of about 1 to 2 mm, the thermal conductivity sensor 10 can be measured with little influence from forced convection. In this case, since the sample arrival time is extremely short, the response speed can be extremely increased.
[0020]
Further, when forced convection can be generated in the cavities 105a and 105b by the flow in the flow path 104 as in the conventional thermal conductivity measurement device, the flow speed of forced convection also changes according to the change in the flow speed in the flow path 104. . For this reason, in order to perform a stable measurement, it was necessary to control the flow velocity in the flow path 104 accurately and constantly. However, the thermal conductivity measuring apparatus shown in FIG. 4 can perform measurement with almost no influence from forced convection as described above, so that it is not necessary to strictly control the flow velocity in the flow path 4. A secondary effect is also obtained.
[0021]
Here, in the conventional thermal conductivity measurement device and the thermal conductivity measurement device according to the present invention, the flow velocity on the thermal conductivity sensor and the sample arrival time are compared. Table 1 shows the flow rate and sample arrival time on the thermal conductivity sensors 10 and 110 in the conventional thermal conductivity measuring device (FIGS. 7 and 8) and the thermal conductivity measuring device according to the present invention (FIGS. 1 and 4). It is a table | surface which shows an example.
[0022]
[Table 1]

[0023]
As described above, since it is important that the amount of heat carried away by the flow is small when measuring the thermal conductivity, the slower the flow rate on the thermal conductivity sensors 10, 110 is, the better. Moreover, since measurement at a fast response speed is required, the shorter the sample arrival time, the better. As can be seen from Table 1, the flow rate on the thermal conductivity sensor 110 is improved in the conventional thermal conductivity measurement device shown in FIG. 8 as compared with the conventional thermal conductivity measurement device shown in FIG. However, the sample arrival time was longer instead. On the other hand, according to the thermal conductivity measuring apparatus shown in FIG. 1, the flow velocity on the thermal conductivity sensor 10 can be improved while maintaining the sample arrival time. Further, according to the thermal conductivity measuring device shown in FIG. 4, both the flow rate on the thermal conductivity sensor 10 and the sample arrival time can be further improved as compared with the thermal conductivity measuring device shown in FIG. . That is, according to the thermal conductivity measuring device shown in FIGS. 1 and 4, it can be said that both the flow rate on the thermal conductivity sensor 10 and the sample arrival time can be achieved.
[0024]
( Reference example )
FIG. 6 is a cross-sectional view showing a configuration of a reference example related to the thermal conductivity measuring device according to the present invention. 6A shows a cross section including the axial direction of the flow path 44, and FIG. 6B shows a cross section in the VIB-VIB 'line direction in FIG. 6A. In FIG. 6, the same parts as those in FIGS. 1 and 4 are denoted by the same reference numerals, and the description thereof is omitted as appropriate.
1 and 4 has a configuration in which cavities 5a and 5b are formed in the flow path blocks 1a and 1b. However, the thermal conductivity measurement apparatus illustrated in FIG. The cavity 45 is provided inside.
[0025]
The cavity 45 includes a cylindrical container 42 having an upper surface opened and a can case 21 inserted into the container 42. The thermal conductivity sensor 10 is disposed on the can case 21, and a sintered metal plate 33 is fitted on the opened surface of the container 42. The container 42 is disposed in the flow path 44 so that the surface on which the sintered metal plate 33 is fitted faces the upstream side of the flow path 44, and is supported by a support member 43 fixed to the inner wall of the flow path block 41. .
The sintered metal plate 33 has a function similar to that of the wire mesh 32 shown in FIG. That is, the fluid in the flow path 44 and the fluid in the cavity 45 are exchanged only by molecular diffusion through the sintered metal plate 33. For this reason, even if the flow 46 in the flow path 44 is orthogonal to the sintered metal plate 33, forced convection does not occur in the cavity 45 by the flow 46 in the flow path 44. Therefore, even with the thermal conductivity measurement device shown in FIG. 6, it is possible to obtain the same measurement accuracy and response speed as the thermal conductivity measurement device shown in FIG.
[0026]
As described above, it is a feature of the present invention to provide the wire nets 31, 32 or the sintered metal plate 33 at the boundary between the flow paths 4, 44 and the cavities 5a, 5b, 45. However, since it is only necessary to obtain an effect of reducing the influence of the fluid flows 6 and 46 in the flow paths 4 and 44 on the cavities 5a, 5b and 45, the flow paths 4 and 44 and the cavities 5a, 5b and 45 What is disposed on the boundary of the substrate may be a porous body having many pores. As the porous body, in addition to the metal nets 31 and 32 and the sintered metal plate 33, a resin net such as Teflon, a punching plate, a porous ceramic plate, and the like can be used.
Further, regarding the porous body, it is desirable that the diameter of the hole is small in order to slow down the flow in the cavities 5a, 5b, 45. Further, it is desirable that the number of holes per unit area is large and the depth of the holes is shallow so that the fluid in the cavities 5a, 5b, 45 can be replaced quickly.
[0027]
The fluid in the present invention is a general term for gas and liquid, and the thermal conductivity measuring device according to the present invention is effective for both gas and liquid, but is particularly effective for liquid.
Japanese Patent Laid-Open No. 5-232052 discloses a technique in which a wire mesh is provided on the upstream side or the downstream side of the sensor to reduce the flow velocity on the sensor. However, this technique differs from the present invention in that the location where the wire mesh is provided is not in the boundary between the flow path and the cavity but in the middle of the flow path. Even if the flow rate is slow, the effect is different in that the flow in a certain direction on the sensor does not disappear after all. Therefore, the above publication cannot be a material that denies the inventive step of the present invention.
[0028]
【The invention's effect】
As described above, in the thermal conductivity measuring device according to the present invention, the porous body is provided in the opening to the flow path of the cavity formed in the flow path block . Since the flow velocity is reduced by this porous body, the flow on the thermal conductivity sensor can be slowed without increasing the depth of the cavity. Therefore, the measurement accuracy can be increased while maintaining the response speed. In addition, since there is no large vortex flow on the thermal conductivity sensor and the flow velocity does not change, the measurement stability is improved.
[0029]
Also, by designing the porous body so that the fluid in the flow path and the fluid in the cavity are exchanged only by molecular diffusion, the thermal conductivity sensor Measurements can be made accurately without being affected by forced convection. In this case, the response speed can be extremely increased. In addition, if a porous body designed in this way is used, even if the flow velocity of the flow path changes, measurement can be performed with almost no influence from forced convection, so there is no need to strictly control the flow rate. can get.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing a configuration of a first embodiment of a thermal conductivity measuring device according to the present invention.
FIG. 2 is a perspective view showing a structure of a heating resistance type thermal conductivity sensor.
FIG. 3 is a schematic diagram showing the behavior of the fluid in the vicinity of the wire mesh shown in FIG.
FIG. 4 is a cross-sectional view showing a configuration of a second embodiment of a thermal conductivity measuring device according to the present invention.
FIG. 5 is a schematic diagram showing the behavior of the fluid near the wire mesh shown in FIG. 4;
FIG. 6 is a cross-sectional view showing the configuration of a reference example related to the thermal conductivity measuring device according to the present invention.
FIG. 7 is a cross-sectional view showing a configuration example of a conventional thermal conductivity measuring device.
FIG. 8 is a cross-sectional view showing another configuration example of a conventional thermal conductivity measuring device.
[Explanation of symbols]
1, 1a, 1b, 41 ... flow path block, 2a, 2b ... through hole, 3 ... depression, 4, 44 ... flow path, 5a, 5b, 45 ... cavity, 6, 46 ... flow of fluid in the flow path, DESCRIPTION OF SYMBOLS 7 ... Eddy, 8 ... Molecular diffusion, 10 ... Heat generation resistance type thermal conductivity sensor, 11 ... Base, 12 ... Membrane, 13 ... Slit, 14 ... Heating element, 15a, 15b ... Electrode pad, 21 ... Can case, 22 ... Stainless steel support plate, 23a, 23b ... lead pin, 31,32 ... wire mesh, 31a, 32b ... mesh, 33 ... sintered metal plate, 42 ... container, 43 ... support member.

Claims (2)

A channel block forming a channel for guiding fluid;
A cavity formed in the flow path block so as to face the flow path and in which the fluid stays,
An exothermic thermal conductivity sensor provided in the cavity and measuring the thermal conductivity of the fluid;
A thermal conductivity measuring device comprising: a porous body provided so as to constitute a part of an inner wall surface of the flow path at an opening portion of the cavity to the flow path. In the thermal conductivity measuring device according to claim 1,
The thermal conductivity measuring device is characterized in that the porous body is designed such that the fluid in the flow path and the fluid in the cavity are exchanged only by molecular diffusion.

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