JPS6112629B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a vertical electric heater.

Among the large electric heaters, in nuclear reactor simulation experiments, the temperature is equal to the core temperature of the nuclear reactor.
It is used as a heat generating source that generates high temperatures of over 1000℃.

Electric heaters for this purpose use a high-pressure heat medium as shown in Figure 1 in order to eliminate unstable gas flow and suppress gas stagnation and pulsation.
Most of them are vertical type, in which He gas at 700°C is introduced into the interior through a gas inlet 2 provided at the bottom of the pressure vessel 1, and flows out through a gas outlet 3 provided at the upper part, and a hollow cylindrical heater element 4 is used. In order to prevent blurring, the upper end is often fixed to the upper tube plate 5 by hanging as shown in the figure.

By the way, in an electric heater, in order to increase the electrical resistance, the thickness of the heater element 4 is made thinner.
It is necessary to reduce the diameter, and in order to increase the heat transfer area, it is necessary to increase the length of the heater element 4.

However, in the above-mentioned vertical electric heater, if the thickness of the heater element 4 is made thinner, the diameter is made smaller, and the length is longer, it will not be able to withstand its own weight at high temperatures of 1000°C or more and will melt, so It cannot be done for a long time. Therefore, a sufficient heat transfer area cannot be obtained.

Further, the upper tube plate 5, on which the upper end of the heater element 4 is suspended and fixed, has a thick wall, low electrical resistance, and a large heat capacity, so it receives heat transfer from the heater element 4, becomes high temperature, and is subjected to extremely large thermal stress. Moreover, this upper tube plate 5 is supported and fixed to the inner surface of the pressure vessel 1 via a spacer 6,
In addition, since the upper ends of a large number of heater elements 4 are supported and fixed, there is little room for thermal expansion.
Therefore, the thermal stress cannot be absorbed and relaxed, resulting in deformation and damage, and furthermore, one end of the heater element 4, which is suspended and fixed to the upper tube plate 5, is also damaged, which impedes the flow of the He gas and prevents the He gas from flowing. There were problems such as not being able to heat to the required temperature.

The present invention has been made in order to solve the problems of the conventional vertical electric heater, and instead of increasing the length of the hollow cylindrical heater element, an outer cylindrical tube is provided concentrically around the outer periphery of the heater element through an electrical insulating material. hand,
The heat transfer surface of the heater element was increased by passing He gas inside and outside of the heater element, and the upper end of the heater element was extended upward without being suspended from the upper tube plate and covered with insulation material at the top of the pressure vessel. It is an object of the present invention to provide a vertical electric heater that is suspended and fixed in a low-temperature space so that no thermal stress is applied to the upper tube plate.

An embodiment of the vertical electric heater according to the present invention will be described below with reference to FIGS. 2 and 3. 1' is a pressure vessel, and the straight body extends from the gas inlet 2' at the lower part to the gas outlet 3' at the upper part. A heat insulating material 7 is stretched to a required thickness on the inner peripheral surface of the section, and an upper tube sheet 5, an intermediate tube sheet 5', and a lower tube sheet 5'' are placed at regular intervals in an internal space 9 held by a reflector 8. are supported and fixed to the inner circumferential surface of the pressure vessel 1' via a spacer 6.A large number of hollow cylindrical heater elements 4' with thin walls are arranged at equal intervals on these tube plates 5, 5', 5''. penetrated,
This heating element 4' is extended upward, and its upper end is penetrated through a heat insulating material 10 that seals the upper end of the internal space 9, and the heat insulating material 10 and the heat insulating material 11 filled in the top of the pressure vessel 1' are connected to each other. It is supported and fixed to an element receiver 13 in a low temperature space 12 isolated by. That is, as shown in FIG. 3, the flange 4a provided at the upper end of the heater element 4' is sandwiched between the flange 13b of the cylindrical body 13a of the element receiver 13 and the retainer plate 14, and is secured by tightening with bolts 15. . The upper end internal space of the heater element 4' surrounded by the heat insulator 10 is sealed, and the heater element 4' in the gas outlet space 16 between the heat insulator 10 and the upper tube sheet 5 is sealed.
A large number of gas discharge holes 17 are provided at regular intervals on the outer peripheral surface of the
is drilled. Upper tube plate 5 to lower tube plate 5''
An outer cylindrical tube 18 is disposed concentrically around the outer periphery of the heater element 4' and is supported and fixed to each tube sheet 5, 5', 5'', and the outer cylindrical tube 18 is placed above and above the upper tube sheet 5. In the downwardly penetrating portion of the lower tube plate 5″,
As shown in FIG. 4, notches 19 are provided on three sides, and protrusions 21 provided on three sides of the inner peripheral surface of the cylindrical electrical insulating material 20 fitted to the outer tube 18 are fitted into the notches 19. The heater element 4' is slidably supported by the protrusion 21. Further, as shown in FIG. 5, a cylindrical electrical insulating material 20' is fitted onto the inner circumferential surface of the upper portion of the intermediate tube plate 5' of the outer cylindrical tube 18, and a spacer 2 is fitted onto this electrical insulating material 20'.
A heater element 4' is slidably supported via 2. Internal space 9 of the pressure vessel 1'
In the lower half of the gas inlet space 24 between the heat insulating material 23 whose lower end is sealed and the lower tube plate 5'', an annular cylinder 27 with a number of through holes 26 formed in the inner circumferential wall 25 is provided to allow the gas to flow through. The opening surface of the lower end of the heater element 4' faces the inside of this annular cylinder 27, and a large number of gases are formed on the outer peripheral surface of the lower end of the heater element 4'. An introduction hole 28 is bored.

A bar 29 is attached to the lower end of the heater element 4', and this bar 29 hermetically passes through the heat insulating material 23 and is electrically connected to a booth bar 31 attached to the water-cooled electrode 30. The element 4' is electrically connected to the pressure vessel 1' via the element receiver 13 and its support member 13'.

In the vertical heater of the present invention configured as described above, when the water-cooled electrode 30 is energized, the water-cooled electrode 30 is energized, the heater element 4' is energized via the booth bar 31 and the bar 29, and the element receiver 13 and support member 13' are energized. is grounded to the pressure vessel 1' through the heater element 4', forming one star connection.
is heated. On the other hand, He gas at 700°C, which is a high-pressure heat medium, enters the annular cylinder 27 of the gas inlet space 24 from the gas inlet 2' through the through hole 26 bored in the inner circumferential wall 25 of the annular cylinder 27. The gas is discharged and enters the hollow cylindrical heater element 4' through the lower end opening surface of the heater element 4' and the gas introduction hole 28 on the outer peripheral surface of the lower end, and also from the lower end opening surface of the outer cylindrical tube 18 on the outer periphery of the heater element 4'. The outer tube 18
Go inside. The heater element 4' is sufficiently heated through the inside and outside, and enters the gas outlet space 16 from the gas discharge hole 17 on the outer peripheral surface of the upper end of the heater element 4' and the upper end opening surface of the outer cylindrical tube 18, and the gas flows into the gas outlet space 16. It exits from outlet 3' at a temperature of 1000℃.

However, the heater element 4', which is red hot at high temperature, becomes lower at the bottom and higher at the top due to heat exchange with the He gas, creating a temperature difference and causing thermal stress.
The heating element 4' is electrically insulated from the outer tube 18 by insulating materials 20, 20' and can slide downward, and furthermore, it extends upward and its upper end is separated by insulating materials 10, 11. Since it is supported and fixed to the element receiver 13 in the low temperature space 12, this heater element 4' is attached to each tube plate 5, 5', 5''.
It thermally expands downward without being constrained by it, and in other words, extends and slides downward to absorb and relieve thermal stress.

Further, the upper, middle, and lower tube plates 5, 5', and 5'' are separated by the heater element 4' and the outer tube 18 as described above, and the outer tube 18 and the heater element 4' are separated by the insulating materials 20, 20'. Since the heater element 4' is electrically insulated and supported so as to be able to slide, the heater element 4' is not restrained by the heater element 4' and does not receive direct heat transfer from the heater element 4'. Therefore, each tube sheet 5,
5' and 5'' receive heat transfer from the outer tube 18 whose temperature has increased due to the radiant heat of the heater element, and even if the upper tube sheet 5 and lower tube sheet 5'' come into contact with He gas and rise in temperature, each of these tubes Since there is almost no temperature difference in any part of the plates 5, 5', 5'' themselves, little thermal stress is generated.

As detailed above, in the vertical electric heater of the present invention, an outer cylindrical tube is provided concentrically around the outer periphery of the heater element, and He gas is passed inside and outside the heater element for heating. Since the surface is used as a heat transfer surface, the heat transfer area per unit length is doubled, and the heat exchange efficiency of He gas is extremely high. Therefore, a sufficient heat transfer area can be obtained without increasing the length of the heater element as in the conventional case.

Alternatively, instead of suspending the heater element from the upper tube sheet, the upper end of the heater element is suspended in a low-temperature space covered with an insulating material at the top of the pressure vessel, and the middle of the heater element is fixed concentrically to each tube sheet. Since it is slidably inserted and supported within the cylindrical pipe via an electrical insulating material,
Even if a temperature difference occurs between the upper and lower parts of the heater element due to heat exchange with He gas, and thermal stress occurs, it can thermally expand downward without being restrained by the outer tube, absorbing and relieving the thermal stress. .

Furthermore, the tube sheet does not receive direct heat transfer from the high-temperature heater element, nor is it restrained by the heater element, so even if there is heat transfer from the outer tube that receives radiant heat from the heater element, Even if heat is received due to contact with gas, there is almost no temperature difference in the tube sheet itself, and the occurrence of thermal stress is extremely small. Therefore, the tube sheet will not be deformed or damaged, so not only the heater element but also the outer tube will not be damaged, and the flow of He gas will not be hindered.
It is possible to reliably heat He gas sufficiently to the required temperature.

In addition, in the gas inlet space, an annular cylinder with a large number of through holes drilled at equal intervals in the inner circumferential wall is provided to communicate with the gas inlet, and gas inlet holes are provided on the outer circumferential surface of the lower end of the heater element in addition to the lower end opening. Since it has been drilled,
Since the gas entering from the gas inlet flows uniformly inside and outside each heater element without causing unstable flow, there are many excellent effects such as no overheating due to gas stagnation.

[Brief explanation of the drawing]

Figure 1 is a vertical cross-sectional view of a conventional vertical electric heater.
FIG. 2 is a longitudinal sectional view of the vertical electric heater of the present invention;
FIG. 3 is an enlarged vertical cross-sectional view showing the hanging support state of the heater element in the vertical electric heater of the present invention, FIG. 4 is an enlarged cross-sectional view taken along line A-A in FIG. 3, and FIG. FIG. 4 is an enlarged cross-sectional view taken along the line B-B in FIG. 3; 1'...Pressure vessel, 2'...Gas inlet, 3'...
...Gas outlet, 4'...Heater element, 5
...Upper tube sheet, 5'...Middle tube sheet, 5''...Lower tube sheet, 6...Spacer, 7...Insulating material, 8...
Reflector, 9...Inner space, 10, 11...
Heat insulating material, 12... Low temperature space, 13... Element holder, 13'... Support member, 14... Pressing plate, 15
...Bolt, 16...Gas outlet space, 17...
Gas discharge hole, 18... Outer tube, 19... Notch, 2
0... Electrical insulating material, 21... Protrusion, 22... Spacer, 23... Heat insulating material, 24... Gas inlet space, 25... Inner peripheral wall, 26... Through hole, 27... Annular tube, 28 ...Gas introduction hole, 29...Bar, 30
...Water-cooled electrode, 31...Booth bar.

Claims (1)

[Claims] 1. In a vertical electric heater in which gas is introduced from the bottom and discharged from the top, a hollow cylindrical heating element penetrates each tube sheet and extends upward, and the element is heated in a low-temperature space with its upper end separated by a heat insulating material. The upper end of the heater element is supported and fixed to the receiver and surrounded by a heat insulating material.The inner space at the upper end of the heater element is sealed, and a large number of gas discharge holes are drilled on the outer circumferential surface of the heater element in the gas outlet space connected to the gas outlet. An outer cylindrical tube is arranged concentrically around the outer periphery of the heater element from the upper tube sheet to the lower tube sheet, and is slidably supported on each tube sheet via an electrical insulating material. A vertical cylinder having a gas inlet hole formed therein, and an annular cylinder having a plurality of through holes formed in its inner circumferential wall in the gas inlet space below the heater element and communicating with the gas inlet. type electric heater.