JPS6096124A - Heat pipe for cooling underground cable line - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to an improvement in a heat pipe for cooling an underground cable line, which is laid along an underground cable line and suppresses a temperature rise due to heat generation of the cable.

[Prior art]

There is a heat pipe cooling method as a cooling method for underground cables (mainly ring cables).

In this method, a heat pipe is drawn into a conduit near the conduit where the cable is drawn, the heat generated by the cable is absorbed by the heat pipe, and the heat is carried to the heat dissipation part of the heat pipe. It is a mechanism that radiates heat from the inside to the outside.

This heat pipe cooling method is different from other water cooling methods and wind cooling methods, and there is a problem in that it is difficult to know whether or not it is working properly.

For example, in a water circulation cooling system used for indirect cooling inside a trough, it is possible to use 4i (f = edict) to indicate that the pump is operating normally if it is rotating; You can confirm that it is working properly. However, in the case of the heat pipe cooling method, the refrigerant moves through the closed pipe without the help of any power, boiling → vapor transfer →
Since the flow from coagulated silk to reflux is repeated, it is unclear whether or not it is operating normally, causing anxiety to users and equipment maintainers.

For example, if a pipe is damaged and there is no refrigerant inside, but it is not detected, the heat pipe will not be able to remove heat when the load on the cable increases, causing an abnormal temperature rise and dielectric breakdown. There is a risk of this happening. Therefore, it is essential to promptly detect loss of refrigerant in the heat pump due to pinholes, external injuries, etc. in order to ensure system reliability.

Generally, heat pipes for cooling underground cable lines use fluorocarbon-based refrigerants. A fluorocarbon detector is known as a device that detects a fluorocarbon gas leak. However, considering that it is not known where a leak point will occur in a long heat pipe, or that even if there is a leak, it will be blown away by the wind, it is not appropriate to use a fluorocarbon detector.

In addition, there are two ways to check the operation of the heat pipe: (A peephole is installed in the heat dissipation section, and maintenance personnel observe the condensation and dripping of refrigerant at appropriate intervals. If refrigerant is not dripping, it is determined that the heat nozzle is not operating. (2) Heat pipe When the temperature distribution in the longitudinal direction of the Heat Nomi Ib becomes uneven, for example, the temperature of the heat dissipation part is several degrees higher than the temperature of the heat absorption part (the part along the cable). Make sure to issue a warning from time to time.

However, with method (■), providing a peephole increases the number of sealing points with flanges and seals, which reduces reliability in terms of refrigerant leaks, and when there is no or only a small load on the cable, refrigerant condenses even if the heat pipe is normal. There are problems in that there is a possibility of erroneous detection because the amount is nonexistent or very small, and that it is inconvenient because 4i cannot be confirmed to be working unless it is directly observed. In addition, with method (■), when the load on the cable is small and the outside temperature is high, for example, the temperature at the heat absorbing part underground may be 20°C, and the temperature at the heat dissipating part exposed to the outside air may be 32°C, resulting in malfunction. ,
There is a problem.

OBJECT OF THE INVENTION] In view of the problems of the prior art as described above, an object of the present invention is to provide a method for reliably detecting whether or not the system is operating normally, regardless of the size of the load or the outside temperature. To provide a heat pipe for underground cable line cooling that can be used
be.

[Structure of the invention]

The heat pipe for cooling underground cable lines of the present invention, which achieves the above object, is filled with a refrigerant that always has a vapor pressure of 1 degree higher than atmospheric pressure at a temperature higher than the soil base temperature, so that the pressure inside the pipe is equal to atmospheric pressure. The device is characterized in that a pressure sensor that is activated when the pressure is applied is attached.

[Example of real power]

The drawings show a heat pipe according to an embodiment of the present invention and how it is used. 1 is soil, 2A and 2B are pipes buried underground, and 3 is a cable drawn into the two pipes. Reference numeral 4 denotes a heat pipe according to an embodiment of the present invention, whose heat absorbing fds 5 is drawn into the conduit IB, and the heat radiating part 6 is installed in the atmosphere a.

The heat generated by the cable 3 heats the soil 1 via the pipe line 2A, and further heats the heat absorption part 5 of the heat pipe 4 via the pipe line 2B. In the heat pipe 4, the enclosed refrigerant is vaporized by this heat. Vaporized refrigerant releases heat ￥'AS
6, where it is cooled and condensed. The condensed refrigerant passes through the wick on the inner surface of the tube and flows back to the heat absorption section 5. The heat absorbed by the heat absorption part 5 in this way is carried to the heat radiation part 6,
The heat radiating section 6 radiates the heat to the outside.

A pressure gauge 7 with an alarm contact is attached to the heat radiation part 6 of the heat pipe 4. This pressure gauge 7 detects the pressure inside the heat pipe 4, and the contact closes when the pressure inside the pipe becomes equal to atmospheric pressure, that is, when the difference from atmospheric pressure becomes less than a predetermined value.
or open), for example, lights up the special alarm lamp 8. In place of the warning lamp 8, a buzzer or a controller that operates in response to a contact closing signal may be provided.

Inside the heat pipe 4, a refrigerant is sealed which has a temperature higher than the soil failure base temperature and whose vapor pressure is always lower than atmospheric pressure.

Soil basal temperature is usually 17-25°C, and cable 3
When there is no load, the ambient temperature of the heat absorption part 5 of the heat pipe is about this temperature. The vapor pressure of the refrigerant decreases as the temperature decreases. If the vapor pressure drops to atmospheric pressure or lower near the soil base temperature, the above pressure gauge with alarm contact 7 indicates that the pressure inside the pipe is due to a refrigerant leak. It is not possible to determine whether the pressure has reached atmospheric pressure because of the temperature drop, or whether it has become atmospheric pressure due to the temperature drop.For this reason, the refrigerant sealed in Heater)/ξ Eve 4 is a vapor that is always more delicious than atmospheric pressure at a temperature higher than the soil base temperature. Use something that has pressure.

Usually, heat pipes for cooling underground cable lines are 30 to 5
The refrigerant H1 is set to operate at 0° C., and Freon 11 is used as a refrigerant because it has good compatibility with the heat pipe tube material and has a vapor pressure within a safe pressure range within the operating temperature range. However, since Freon 11 has a boiling point of 23.8° C., its vapor pressure is equal to or lower than atmospheric pressure near the soil base temperature. Therefore, the use of Freon 11 is not appropriate.

The following table shows the vapor pressure (in kg/c abs) of refrigerants that can be used in the heat pipe of the present invention.
) is shown.

According to these data, a refrigerant with a Freon 12 ratio of 5 to 3 ow 1%, which is a mixture of 70 N 11 and Freon 12, always has a vapor pressure higher than atmospheric pressure at a temperature above the soil failure base temperature. Moreover, the pressure does not become extremely high even at around the maximum operating temperature of 50°C.

Also, 70n 114 alone or 70n 114 and 70n 1
The same applies to a refrigerant in which the ratio of 70 ton 12 is 20% or less by mixing 2 and 12.

When such a refrigerant is used, there is almost no load on the cable, and even if the ambient temperature of the heat pipe 4 is around the soil base temperature, as long as the heat pipe 4 is normal,
The pressure inside the pipe becomes higher than atmospheric pressure. Therefore, if the pressure gauge with alarm contact 7 detects that the pressure inside the pipe is equal to atmospheric pressure, it means that the refrigerant is leaking and the heat pipe 4
This indicates that it is not working properly.

The pressure gauge with alarm contact has excellent durability and can be connected to the heat pipe by welding.

Therefore, there is no risk of refrigerant leakage caused by installing this pressure gauge.

In the above embodiment, a pressure gauge with an alarm contact was used as the pressure detector, but any pressure gauge may be used as long as it can detect that the pressure inside the pipe has become equal to atmospheric pressure.

〔Effect of the invention〕

As explained above, according to the present invention, the inside of the pipe becomes atmospheric pressure only when a refrigerant leak occurs, and this is detected by a pressure detector, so regardless of the size of the cable load or the high or low outside temperature. First, it is possible to reliably detect whether or not the heat pipe is operating normally, which greatly contributes to improving the reliability of the underground cable line system.

[Brief explanation of drawings]

The drawing is a sectional view showing an underground cape urinary tract cooling heat pipe according to one embodiment of the present invention and its usage state. 1...Soil, 2A, 2B...Pipeline, 3
・・・・・・Cable, 4・・・Heat knife, 5・・・Heat absorption part, 6... Heat radiation part, 7.
...Pressure gauge with alarm contact, 8...Buttock lamp.

Claims (2)

[Claims] (1) A refrigerant that always has a vapor pressure higher than atmospheric pressure at a temperature higher than the soil base temperature is sealed, and a pressure detector is attached that operates when the pressure inside the pipe becomes equal to atmospheric pressure. Heat pipe for cooling underground cable lines. (2) The heat pipe according to claim 1, wherein the pressure detector is attached to a heat radiation part of the heat pipe.