JPH04366093A - powder vacuum insulation - 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]

0001

[Industrial Application Field] The present invention relates to powder vacuum insulation,
In particular, the present invention relates to a powder vacuum heat insulating body in which a filter for preventing powder scattering is provided at an exhaust port for evacuating a powder vacuum heat insulating layer.

0002

[Prior Art] As a conventional powder vacuum insulation of this type,
A heat insulating container as shown in FIG. 6 has been proposed. This container is composed of a double structure having an opening 11 on one side, and includes an outer container 12 and an inner container 13 made of stainless steel, and a space 14 between the outer container 12 and the inner container 13. It has a powder vacuum insulation layer 15 formed on the outer container 12, and an exhaust cap 16 attached to the wall surface of the outer container 12. When this heat insulating container is used, the opening 11 is closed with a heat insulating lid to form a sealed space. The powder vacuum heat insulating layer 15 is formed by filling the space 14 with a heat insulating powder 18 such as fine silica powder, evacuating the space 14, and then sealing the space 14 to maintain the vacuum.

[0003] The exhaust cap 16 is used to evacuate the space 14, and has an exhaust port 19. A filter 17 for preventing powder scattering is attached to the exhaust port 19, and the filter 17 is made of compacted ceramic fiber, metal, soft plastic foam, or the like. That is, since the powder 18 has a scattering property, it is easily scattered during evacuation, and the filter 17 is provided to prevent this scattering. If scattering is not prevented, the exhaust pump may suck in the powder 18 and malfunction, or the powder 18 adhering to the sealing part of the exhaust cap 16 when sealing the exhaust port 19 may cause a sealing failure. It is common to provide a filter 17 as shown in FIG.

0004

[Problems to be Solved by the Invention] However, in the conventional powder vacuum insulated container described above, the filter 19 is directly attached to the exhaust port 18 having the diameter D1.
There is a problem in that the exhaust conductance of the space 14 becomes very small, and it takes a long time to evacuate the space 14.

SUMMARY OF THE INVENTION An object of the present invention is to solve these problems and increase the exhaust conductance of the filter, thereby shortening the time required for evacuation.

[0006]

[Means for Solving the Problems] In order to achieve the above object, the present invention provides a powder vacuum insulation layer formed to be able to maintain a vacuum in the internal space of a double-walled structure, and a vacuum evacuating layer for evacuating the space. an exhaust port provided on the wall of the structure for the purpose of
A filter for preventing powder scattering is provided in the space, which has a diameter larger than that of the exhaust port, and is disposed in the space so as to cover the exhaust port at a position away from the exhaust port.

[0007]

[Function] According to the above configuration, the filter is placed so as to cover the exhaust port at a position away from the exhaust port, so it is possible to increase the diameter of the filter without being affected by the diameter of the exhaust port. Therefore, the exhaust conductance of the filter can be significantly increased. Therefore, the flow rate of exhaust gas passing through the filter per unit time increases, and the evacuation time is shortened.

[0008]

[Embodiment] As shown in FIG. 1, the powder scattering prevention filter 17 is installed inside the space 14 at a position away from the exhaust port 19 of the exhaust cap 16 so as to cover the exhaust port 19, that is, the exhaust cap 16. It is located. This filter 1
7, for example, as shown in FIG. 2, a filter body 20 made of ceramic fiber blanket is compacted into a dish shape as shown, and then surrounded with a stainless steel wire mesh 21 and spot welded to the inner wall surface of the outer container 12. It is stuck by something like that. The diameter D2 of this filter 17 is larger than the diameter of the exhaust port 19. Note that metal, soft plastic foam, or the like can also be used as the material for the filter body 20.

According to the above configuration, since the filter 17 is disposed at a position away from the exhaust cap 16 so as to cover the exhaust cap 16, the diameter D of the filter 17 is
2 can be increased without being influenced by the diameter D1 of the exhaust port 19 of the exhaust cap 16. Therefore, the exhaust conductance of the filter 17 can be increased arbitrarily, the exhaust flow rate per unit time passing through the filter 17 can be increased, and the time required for evacuation can be shortened.

Table 1 shows the results of evacuation tests conducted on the conventional powder vacuum insulated container and the powder vacuum insulated container of the present invention. The test conditions were as shown in FIGS. 3(a) and 3(b): the volume of the space 14 of the container was 500 liters, the diameter D1 of the exhaust port 19 was 40 mm, and the filter 17 of the present invention was
The aperture D2 was set to 200 mm. Further, after filling the space 14 with a predetermined amount of silica-based powder 18 and compacting it, the powder 18 is baked while the exhaust pump 22 connected to the exhaust cap 16 pumps at a speed of 170 liters/se.
The space 14 was evacuated at step c. At this time, the pressure in the space 14 is measured by the Pirani vacuum gauge 23, and
The exhaust time was measured.

[0011]

[Table 1]

As is clear from Table 1, the effect of shortening the exhaust time by the present invention is remarkable. The reason why such excellent results were obtained is as follows. Generally, as shown in FIG. 4, when the inside of the container 31 is evacuated by the exhaust pump 33 via the conduit 32, the following equations (1) and (2) are used.
holds true.

[0013]Q=C(P1-P0)
...(1) 1/S1 = 1/C+1/S0
...(2) Here, Q = amount of gas exhausted (Torr・liter/sec) C = conduit 32
Conductance (liters/sec) P1 = Pressure at the outlet of the container (Torr) P0 = Pressure at the exhaust pump side (Torr) S1 = Pumping speed at the outlet of the container (liters/sec) S0 = Pumping speed at the exhaust pump side (liters/sec) ) (1) Expression shows that in order to increase the gas amount Q and shorten the exhaust time, the exhaust conductance C should be increased. Also (2
) The formula is, if the exhaust conductance C is small, S1 ≒ C
This means that increasing the exhaust speed S0 of the exhaust pump 33 has almost no effect. Regarding the exhaust conductance C, it is known that the following equation (3) holds true over a wide pressure range when the conduit 32 is circular and the gas is air at a temperature of 20°C.

C=182・(D4/L)・P+12.1・(D3
/L)・(1+252 PD)/(1+312 PD
) ... (3) Here, D = conduit 32
Diameter of (cm) L = Length of conduit 32 (cm) P = (P1 + P0 )/2 (Torr) This (3)
Using the equation, the exhaust conductance of the filter 34 as shown in FIG. 5 can be determined as follows. That is, since the filter 34 has a large number of ventilation holes 35, if the exhaust conductance of one ventilation hole 35 is Ci, then from equation (3), Ci=182・(d4/l)・P+12.1・
(d3 /l)・(1+ 252 P
d)/(1+312 Pd)
...(4) Here, d = diameter of the vent 35 (cm)
l = Thickness of filter 34 (cm) If the number of vents 35 is n, the exhaust conductance C0 of the entire filter 34 is C0 = ΣCi = nCi
…
(5) Here, n=(πD2 /4)/(πd2
/4) …(6) D=
Diameter (cm) of Filter 34 Since the average particle diameter of the powder 18 is usually several tens of microns, the diameter of the vent hole 35 of the filter 34 that prevents its scattering is considered to be about several microns.

The exhaust conductance of the filter 17 used in the above-mentioned evacuation test is determined as follows using equations (4) and (5). In the case of the conventional filter, l = 0.6 cm, D = D1 = 4 cm, d = 1 μm = 10-4 cm, P = 5 Torr, then Ci = 182 × (10-4) 4 /0.6
)×5+12.1× ((10 −4)3 /0.6
) ×(1+252
×5×10-4)/(1+312 ×5×10-4)
=1.52×10-13 +1.96×
10-11 = 1.98 x 10-11 liters /
sec n = (π×42 /4)/(π×
(10-4)2/4)=1.6×109 pieces
C0 =1.98×10-11×1.6×1
09 = 0.03 liters/sec, and it can be seen that the exhaust conductance C0 is very small and that this lengthens the exhaust time.

On the other hand, in the case of the filter of the present invention, l=6cm, D=D2=20cm, and d=1μ
When m=10-4cm and P=5Torr, Ci'=Ci=1.98×10-11 liters/sec n'=(π×202/
4)/(π×(10-4)2/4)=4.0×10
10 pieces C0'=1.98×10-11
×4.00×1010=0.79 liter/sec
Therefore, the exhaust conductance C0′ in the case of the present invention is
is approximately 26 times larger than the conventional exhaust conductance C0. Therefore, according to the present invention, the evacuation time is significantly shortened. Note that in order to shorten the exhaust time, it is possible to consider measures such as increasing the diameter D1 of the exhaust port 19 or increasing the number of exhaust ports 19, but this would result in lower sealing reliability and higher cost compared to the present invention. There are problems such as.

[0017]

[Effects of the Invention] As described above, according to the present invention, the filter is arranged at a position away from the exhaust port so as to cover the exhaust port, and the diameter of the filter is not affected by the diameter of the exhaust port. Therefore, the exhaust conductance of the filter can be significantly increased. Therefore, the flow rate of exhaust gas passing through the filter per unit time can be increased, and the evacuation time can be significantly shortened.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a powder vacuum insulation container according to an embodiment of the present invention.

FIG. 2 is an enlarged sectional view of the filter for preventing powder scattering in FIG. 1;

FIG. 3 is a sectional view of a vacuum evacuation test device for confirming the effects of the present invention.

FIG. 4 is an explanatory diagram of the exhaust conductance when the container is evacuated.

FIG. 5 is a perspective view of the filter for explaining the exhaust conductance of the filter for preventing powder scattering.

FIG. 6 is a sectional view showing an example of a conventional powder vacuum insulation container.

[Explanation of symbols]

12 Outer container 13 Inner container 14 Space 15 Powder vacuum insulation layer 17 Filter 19 Exhaust port D1 Exhaust port diameter D2 Filter diameter

Claims (1)

[Claims] 1. A powder vacuum insulation layer formed to be able to maintain a vacuum in an internal space of a double structure; an exhaust port provided on a wall of the structure for evacuating the space; Powder vacuum insulation characterized by having a powder scattering prevention filter having a diameter larger than the exhaust port and disposed within the space so as to cover the exhaust port at a position away from the exhaust port. body.