JP4576939B2 - Apparatus and method for monitoring vacuum reduction of vacuum insulation structure - Google Patents

Description

  The present invention relates to an apparatus and method for monitoring the degree of vacuum in a vacuum insulation structure, and in particular, when a thermal load abnormality occurs in an internal temperature maintenance system, the cause of the insulation structure is due to a decrease in the degree of vacuum in a vacuum chamber. The present invention relates to a monitoring apparatus and method capable of determining whether it is caused by a decrease in performance or an internal abnormality.

  Thermal insulation (cold insulation, heat shielding) using vacuum is for thermos, which is usually seen on a daily basis, and for industrial use at low temperatures with superconducting cables and tubes filled with cooling liquid inside and liquid nitrogen inside. Widely used for heat insulation of experimental devices (containers, tanks) (Patent Document 1). In this vacuum heat insulation, it is important to maintain the heat insulation structure or the inside of the vacuum chamber, which is an important part thereof, at a high vacuum. That is, if the degree of vacuum is somewhat reduced (atmospheric pressure is increased) for some reason, the heat conduction and convection are increased accordingly, and the heat insulation performance is greatly deteriorated.

  In such a vacuum heat insulation structure, if the vacuum degree of the heat insulation structure (or the vacuum chamber) is reduced due to some accident, the heat insulation performance is reduced, so the system to be used, that is, the heat insulation structure inside. The heat entering a certain tube or container or the heat dissipated from the tube or container will increase. However, an increase in intrusion heat and dissipated heat also occurs when unexpected heat generation or heat absorption occurs in a tube or container inside the vacuum heat insulating structure. Specifically, for example, in a liquid nitrogen cooling and circulation system for keeping a superconducting cable below a critical temperature, either heat insulation performance deteriorates due to a decrease in vacuum, superconductor deteriorates, or heat generation increases due to an accident. However, the heat input to the liquid nitrogen for cooling increases. As a result, the load on the cooling system increases.

  Therefore, when the intrusion heat or the dissipated heat increases, for example, when the load of the above-mentioned superconducting cable liquid nitrogen cooling circulation system increases, whether or not the cause is due to the deterioration of the performance of the heat insulating structure. It is unclear whether it is due to an accident on the tube or container side inside the structure.

  For this reason, even in such a case, in order to be able to clarify the cause or to determine which is the cause, an observation port is provided in the vacuum tank of the vacuum insulation structure, and a vacuum gauge is installed there to monitor the degree of vacuum. It is generally done.

  On the other hand, in industrial equipment and systems, the vacuum heat insulating structure is often made up of a plurality of vacuum chambers independent from each other in terms of airtightness. Specifically, for example, in a heat insulating structure for a cooling and circulating system of a superconducting cable, a plurality of vacuum heat insulating tanks or spaces held in a vacuum are arranged side by side along the direction of the superconducting cable wire. Also, unlike household items such as thermos, it is a multi-container type vacuum tank with two or three layers that are hermetically separated by metal thin plates to ensure multiple safety. is there.

  In such a case, it is not sufficient to simply install one vacuum gauge or one place. Further, even if it is found that the increase in heat load is caused by an abnormality on the vacuum heat insulating structure side, it is unclear whether a large number of tanks or multiple vacuum tanks have reduced the degree of vacuum. For this reason, it is necessary to install a vacuum gauge in each vacuum chamber.

  However, the observation port or the vacuum gauge itself may cause a deterioration in the degree of vacuum or cause other troubles. Moreover, it is not preferable that a large number of these are installed.

In particular, the vacuum insulation structure of equipment and systems used in the industry is required to maintain a vacuum of about 1 Pa to 10 ⁻⁷ Pa in order to ensure high performance. In general, an ionization vacuum gauge is used (Non-Patent Document 1). However, since the ionization vacuum gauge uses a filament, there is a risk of disconnection, and it is necessary to replace the vacuum gauge and its filament part in repairs at the time of disconnection and periodic inspections for prevention thereof. However, in order to make it possible to replace the vacuum gauge or the like while maintaining the vacuum degree of the vacuum chamber, the structure of the attachment part of the vacuum gauge becomes complicated, which may cause trouble.
JP-A-7-320564 Genichi Horikoshi, “Vacuum Technology”, 2nd Edition, The University of Tokyo Press, March 18, 1983, p. 62-63

  For the above reasons, in a heat insulating device using vacuum heat insulation such as a cooling circulation system of liquid nitrogen used to keep a superconducting cable below a critical temperature, an increase in heat entering from the outside or a constant temperature due to this When an abnormality such as an increase in the heat load of the holding system occurs, promptly determine whether the cause is a deterioration in the heat insulation performance due to a decrease in the degree of vacuum or whether the heat insulation structure is abnormal in the main body of the cooling circulation system. Development of technology that can be judged has been desired.

  In addition, in a vacuum heat insulating structure having a plurality of mutually independent vacuum chambers, it is desirable to develop a technology that can determine which vacuum chamber has undergone a decrease in vacuum when the degree of vacuum has decreased. It was.

  Furthermore, it has been desired to develop a technique that is less likely to cause a decrease in the degree of vacuum and that can detect where the vacuum has occurred.

  Furthermore, there has been a demand for the development of a technology that can be easily repaired, has little maintenance, and is low in cost.

The present invention has been made for the purpose of solving the above-described problems, and a temperature sensor is installed in a vacuum chamber of a vacuum heat insulating structure so that a decrease in the degree of vacuum can be monitored.
In addition, the temperature sensor installation location and mounting structure have been devised.

  According to the first aspect of the present invention, in the vacuum heat insulating structure capable of detecting the wall temperature on the high temperature side and the low temperature side of the vacuum chamber, the wall on either side is directly between the high temperature side and the low temperature side vacuum chamber wall. This is a monitoring device for lowering the degree of vacuum of a vacuum heat insulating structure, characterized in that a temperature measuring sensor that is not in contact is installed.

  In addition, in the detection of the wall temperature on the high temperature side and the low temperature side of the vacuum tank here, for example, when the low temperature side is nitrogen at 1 atm and is in a gas-liquid equilibrium state, it is known in advance that it is −196 ° C., The case where it is known beforehand that it is in the range of 10 ° C. to 30 ° C. because the high temperature side is room temperature is included. For this reason, the temperature measurement is not exact, as long as the degree of vacuum can be monitored regardless of direct or indirect, and there may be some error.

  The invention according to claim 2 is a monitoring device for lowering the vacuum degree of the vacuum heat insulating structure, wherein the temperature sensor is wrapped in a multilayer heat insulating sheet. Monitoring device.

  Thus, since the temperature sensor is wrapped in the multilayer heat insulating sheet or between the heat insulating sheets, it is not directly affected by the vacuum walls on the high temperature side and the low temperature side.

  The invention described in claim 3 is a monitoring device for lowering the degree of vacuum of the vacuum heat insulating structure, wherein the vacuum heat insulating structure has a plurality of independent vacuum chambers, and the temperature is set for each vacuum chamber. It is a monitoring device for lowering the degree of vacuum of a vacuum heat insulating structure characterized in that a sensor is installed.

  The invention according to claim 4 is a monitoring device for a decrease in the degree of vacuum of the vacuum heat insulating structure, wherein the vacuum heat insulating structure includes a device for detecting the occurrence of an abnormality of a thermal load. It is a monitoring device for reducing the degree of vacuum of a vacuum heat insulating structure, which is a target of heat insulation.

  The invention according to claim 5 is a monitoring device for a degree of vacuum reduction of the vacuum heat insulating structure, wherein the vacuum heat insulating structure is employed in a system for cooling a superconducting cable. This is a monitoring device for the vacuum degree of the vacuum heat insulating structure.

The invention according to claim 6 is a vacuum heat insulating structure capable of detecting the wall temperature of the high temperature side and the low temperature side of the vacuum chamber, and the wall on either side is directly between the high temperature side and the low temperature side vacuum chamber wall. It is a monitoring method of the vacuum degree reduction of the vacuum heat insulation structure by installing a temperature sensor that is not in contact,
When there is no abnormality in the degree of vacuum, the initial measurement step of detecting the wall temperature on the high temperature side and the low temperature side of the vacuum chamber in advance and measuring the temperature indicated by the temperature sensor under the detected wall temperature; Compare the temperature measured in the two measurement steps with the monitoring measurement step that actually measures the temperature indicated by the temperature sensor when the wall temperature on the high temperature side and the low temperature side of the vacuum chamber is the same as the initial measurement step. And a vacuum degree lowering determination step for judging whether or not the vacuum degree of the vacuum heat insulating structure is lowered.

  Invention of Claim 7 is a monitoring method of the vacuum degree fall of the said vacuum heat insulation structure, Comprising: The said vacuum heat insulation structure has several mutually independent vacuum tanks, The said temperature for every vacuum tank A method for monitoring a decrease in the degree of vacuum of a vacuum heat insulating structure, wherein a sensor is installed and the three steps are performed for each vacuum chamber.

  The invention according to claim 8 is a method for monitoring a decrease in the degree of vacuum of the vacuum heat insulating structure, wherein the vacuum heat insulating structure includes a system having a device for detecting the occurrence of an abnormal heat load. This is a method for monitoring a decrease in the degree of vacuum of a vacuum heat insulating structure, which is a target of heat insulation, and further includes a step of detecting an abnormality of a heat load.

  The invention according to claim 9 is a method for monitoring a decrease in the degree of vacuum of the vacuum heat insulating structure, wherein the vacuum heat insulating structure is employed in a system for cooling a superconducting cable. This is a method of monitoring the vacuum degree of the vacuum heat insulating structure.

  With the above configuration, according to the present invention, in the constant temperature holding system adopting the vacuum heat insulation structure, when a thermal load abnormality occurs, the cause is the deterioration of the performance of the heat insulation structure due to the decrease in the vacuum degree of the vacuum chamber. It is possible to easily and easily determine whether it is due to other abnormality of the system.

  Further, in a vacuum heat insulating structure having mutually independent vacuum chambers, when the vacuum degree is reduced, it is possible to quickly find out which vacuum tank has the reduced vacuum degree.

  Moreover, not only is it simple and low cost, but the number of accidents in which the degree of vacuum is reduced is reduced.

  In addition, it is excellent in terms of repair, maintenance and cost.

  Hereinafter, the present invention will be described based on the best mode.

(First embodiment)
FIG. 1 conceptually shows an apparatus for low-temperature experiments that employs a vacuum degree monitoring apparatus for a vacuum heat insulating structure according to a first embodiment of the present invention. In FIG. 1, 100 is an inner container. 101 is the exhaust pipe. 110 is a test object placed in the container. 150 is liquid nitrogen filled in the container. 151 is nitrogen gas in the upper part of the container. Reference numerals 201 and 202 denote heat insulating sheets on the inner side and the outer side, respectively. Reference numeral 300 denotes an external container whose outer surface is exposed to the external environment. Reference numeral 400 denotes a temperature sensor installed in the container 100 on the inner side. A temperature sensor 500 is installed to monitor the degree of vacuum installed between the heat insulating sheets 201 and 202 on the inner side and the outer side, or to detect a decrease in the degree of vacuum.

  In addition to the above, the container 100 on the inner side has a structure for loading and unloading a test object into the interior and supplying power for the test, and a filling and discharging mechanism for liquid nitrogen. Moreover, many heat insulation sheets may be piled up.

  In this low temperature experimental apparatus, the inner side container 100 and the outer side container 300 serve as walls of the low temperature side and high temperature side vacuum tanks (vacuum holding airtight containers) of the vacuum heat insulation structure, respectively. A high vacuum is maintained, which prevents air conduction and convection. Further, the two heat insulating sheets 201 and 202 on the inner side and the outer side mainly prevent heat transfer due to radiation and other convection. Then, the liquid nitrogen 150 filled in the inner container 100 is vaporized in accordance with the intrusion heat from the outside and the heat generation from the inner test object 110, so that the temperature in the inner container 100 is reduced to nitrogen. The boiling point is maintained at -196 ° C. The vaporized nitrogen is guided to a nitrogen gas meter (not shown) through the exhaust pipe 101, and the vaporization amount, that is, the heat load is constantly monitored.

  In this low temperature experimental apparatus, the temperature of the inner container 100 corresponding to the low temperature side wall of the vacuum chamber is always −196 ° C., and the temperature of the outer side container 300 corresponding to the high temperature side wall is installed indoors. Room temperature, ie approximately 10 to 30 ° C. For this reason, the temperature sensor 500 installed to detect the decrease in the degree of vacuum installed between the two heat insulating sheets 201 and 202 has the heat generated from the internal test object 110 as long as the heat insulating structure is sound. Even if there is an increase or decrease in the temperature, it shows a substantially constant temperature determined from its heat insulation characteristics, internal temperature and external temperature.

  However, when the heat insulation performance deteriorates due to a decrease in the degree of vacuum, the temperature sensor 500 shows a temperature different from the substantially constant temperature. Specifically, when the degree of vacuum is greatly reduced, it generally moves to the high temperature side due to the effect of air conduction.

  For this reason, when a thermal load abnormality occurs due to a decrease in the degree of vacuum, the temperature indicated by the temperature sensor 500 is viewed to determine whether the cause is due to an abnormality in the test object or the internal system. It can be easily understood whether it is caused by the deterioration of the performance of the vacuum heat insulating structure due to the lowering of the degree.

  In the above-described embodiment, the temperature sensor 400 in the inner container 100 is not necessary for the determination. However, it is necessary when there is no internal temperature holding mechanism or the internal temperature can vary within a certain range due to insufficient holding performance. In this case, the temperature indicated by the temperature sensor in the vacuum chamber is measured in advance at each internal temperature within the range where there is a possibility of fluctuations. It will be judged whether or not.

  In the above-described embodiment, the heat insulating sheets 201 and 202 are provided over the entire circumference between the inner container 100 and the outer container 300, but only in a portion that wraps the temperature sensor 500. It may be provided.

  In the above-described embodiment, the liquid inside the experimental apparatus is nitrogen, but this may be other substances such as neon, hydrogen, and argon.

  In the embodiment described above, since the high temperature side is room temperature, a temperature sensor for detecting the wall temperature on the high temperature side is not provided. However, in order to improve the reliability of measurement and detection, or on the high temperature side wall When it is difficult to estimate the temperature, a temperature sensor is also provided on the high temperature side as appropriate.

(Second Embodiment)
The present embodiment relates to application of a superconducting cable to a cooling system. This is shown in FIG. In FIG. 2, reference numeral 120 denotes a superconducting wire main body made of a superconductor, an insulating sheet, a protective tube thereof, or the like. 150 is liquid nitrogen. Reference numeral 160 denotes a metal inner tube for enclosing liquid nitrogen. Reference numeral 210 denotes a heat insulating sheet wound around the outer periphery of the metal inner tube 160 in a multiple manner. Reference numeral 360 denotes a metal outer tube that protects the heat insulating sheet. The metal inner tube 160, the heat insulating sheet 210, and the metal outer tube 360 form a vacuum heat insulating structure. For this reason, the space with the heat insulating sheet 210 is maintained at a high vacuum. Reference numeral 500 denotes a temperature sensor installed in the heat insulating sheet 210. Reference numeral 501 denotes a penetrating portion for guiding the measurement line for the temperature sensor 500 to the outside of the metal outer tube 360. Reference numeral 600 denotes a connection portion of a vacuum heat insulating structure provided in the middle of a long superconducting cable.

  The vacuum insulation structure for blocking heat from entering the cooling system of the superconducting cable has many pipe-type vacuum chambers that are mutually independent along the line direction of the superconducting cable. A temperature sensor for detecting a decrease in the degree of vacuum is provided in the vacuum space. For this reason, when deterioration of the performance of the heat insulation structure occurs, it is determined which one of the vacuum chambers by checking which temperature sensor shows an increase in temperature or a temperature different from that of other vacuum chambers. It is possible to easily detect whether the degree of vacuum is reduced.

  As mentioned above, although this invention was demonstrated based on the desirable embodiment, this invention is not limited to the said form. That is, for example, the following forms may be used.

  In addition to the vacuum insulation structure, another insulation structure and mechanical protection means therefor are provided.

  The vacuum heat insulating structure is for the purpose of blocking heat radiation from the inside of a heating test facility or the like.

  In the second embodiment, since it is buried in the ground, it is known in advance that the external high temperature side wall has the same temperature along the cable line direction as the internal low temperature side wall. Sometimes, the temperature indicated by the temperature sensor in a certain place is different from the temperature indicated by temperature sensors in many other places, or in combination with this, the vacuum degree of the vacuum chamber in the different place is lowered. Detect that.

It is a figure which shows notionally the apparatus for low-temperature experiments which employ | adopted the monitoring apparatus of the fall of the vacuum degree of the 1st Embodiment of this invention. It is a figure which shows notionally the cooling system of the superconducting cable which employ | adopted the monitoring apparatus of the fall of the vacuum degree of the 2nd Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 Inner side container 101 Exhaust pipe 110 Test object 120 Superconducting wire main body 150 Liquid nitrogen 151 Nitrogen gas 160 Metal inner pipe 201 Inner side heat insulation sheet 202 Outer side heat insulation sheet 210 Thermal insulation sheet 300 Outer side container 360 Made of metal Tube 400 temperature sensor 500 temperature sensor 501 penetrating part 600 connecting part of vacuum heat insulating structure

Claims (9)

  In a vacuum insulation structure that can detect the wall temperature on the high temperature side and the low temperature side of the vacuum chamber, a temperature sensor that does not directly contact either side wall is installed between the high temperature side and the low temperature side vacuum chamber wall A monitoring device for reducing the degree of vacuum of the vacuum heat insulating structure.   The said temperature sensor is wrapped in the multilayer heat insulation sheet, The monitoring apparatus of the vacuum degree fall of the vacuum heat insulation structure of Claim 1 characterized by the above-mentioned.   The vacuum heat insulating structure according to claim 1 or 2, wherein the vacuum heat insulating structure has a plurality of mutually independent vacuum tanks, and the temperature sensor is installed for each vacuum tank. Monitoring device for reduced vacuum.   The said vacuum heat insulation structure makes the system which has the apparatus which detects the generation | occurrence | production when abnormality of a thermal load arises as the object of heat insulation. Monitoring equipment for lowering the degree of vacuum in the vacuum insulation structure.   The vacuum insulation structure monitoring apparatus according to any one of claims 1 to 4, wherein the vacuum insulation structure is employed in a system for cooling a superconducting cable. In a vacuum insulation structure that can detect the wall temperature on the high temperature side and the low temperature side of the vacuum chamber, a temperature sensor that does not directly contact either side wall is installed between the high temperature side and low temperature side vacuum chamber walls It is a monitoring method of the vacuum degree reduction of the vacuum heat insulation structure by keeping,
When there is no abnormality in the degree of vacuum, the initial measurement step of detecting the wall temperature on the high temperature side and the low temperature side of the vacuum chamber in advance and measuring the temperature indicated by the temperature sensor under the detected wall temperature; Compare the temperature measured in the two measurement steps with the monitoring measurement step that actually measures the temperature indicated by the temperature sensor when the wall temperature on the high temperature side and the low temperature side of the vacuum chamber is the same as the initial measurement step. And a vacuum degree reduction judgment step for judging whether or not the vacuum degree of the vacuum heat insulation structure is lowered.   The vacuum heat insulating structure has a plurality of mutually independent vacuum chambers, the temperature sensor is installed for each vacuum chamber, and the three steps are performed for each vacuum chamber. Item 7. A method for monitoring a decrease in vacuum degree of the vacuum heat insulating structure according to Item 6.   The vacuum heat insulating structure is intended for heat insulation of a system having a device for detecting the occurrence of a thermal load abnormality, and further includes a step of detecting a thermal load abnormality. The monitoring method of the vacuum degree fall of the vacuum heat insulation structure of Claim 6 or Claim 7 characterized by the above-mentioned. 9. The method for monitoring a decrease in vacuum degree of a vacuum heat insulating structure according to claim 6, wherein the vacuum heat insulating structure is employed in a system for cooling a superconducting cable.

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