JP3219558B2 - Density meter for cryogenic fluids - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cryogenic fluid density meter installed in a storage tank of a cryogenic fluid having a non-uniform density (for example, slush hydrogen).

[0002]

2. Description of the Related Art As a cryogenic fluid having a non-uniform density, there is slush hydrogen in which solid hydrogen and liquid hydrogen are mixed. FIG. 4 shows an example of a conventional slash hydrogen production test dewar equipped with a density meter. Reference numeral 1 denotes a slush hydrogen container, which has a hollow double structure, and reduces heat entering the slush hydrogen 3 from the surroundings by a vacuum heat insulating layer 2. Reference numeral 4 denotes a liquid nitrogen container, which has a hollow double structure having a vacuum heat insulating layer 5 like the slush hydrogen container 1.

[0003] The liquid nitrogen container 4 is filled with liquid nitrogen 6, and since the heat of invasion from the ambient room temperature is absorbed as latent heat of vaporization of the liquid nitrogen 6, the liquid nitrogen 6 is supplied to the slush hydrogen container 1 installed inside. Intrusion heat is reduced. The slush hydrogen container 1 and the liquid nitrogen container 4 are made of transparent glass for observing the production state of slush hydrogen. Also on the outer surface to reduce radiation heat, the aluminum deposition such emissivity except where the observation window make lower processing is given. The liquid nitrogen container 4 is fixed to the support 7 by a rubber band 8. The slush hydrogen container 1 is fixed to an upper flange 9 by a rubber band 10, and the upper flange 9 is fixed to a support 7 by a rod 11.

Reference numeral 12 denotes a shield plate, and the upper flange 9
The heat that enters the slush hydrogen container 1 from the slush hydrogen container 1 is reduced. 13
Is a pipe for supplying liquid hydrogen, and 14 is a pipe for evacuation.

[0005] The slush hydrogen vessel 14 is connected to a vacuum pump (not shown) via a vacuum pump 14 and a slush hydrogen container 1 is provided.
It is manufactured by intermittently depressurizing and increasing the pressure inside (intermittent depressurization method). Reference numeral 15 denotes a stirrer, and 16 denotes a motor for driving the stirrer, which stirs solid hydrogen and liquid hydrogen generated by an intermittent depressurization method to produce sherbet-like slush hydrogen. Reference numeral 20 denotes an electrode for a capacitance type density meter,
It is hung from the upper flange 9 by the support rod 23 and installed in the slush hydrogen 3.

[0006] Next, will be described with reference to FIG. 5 a detailed structure of the electrostatic capacitance type density meter as a conventional densitometer shown in FIG.

There are holding frames 21a and 21b made of an insulator on the upper and lower sides, and opposed electrodes 20a and 20b are vertically arranged therebetween. The holding frames 21a, 21b are fixed rods 22a,
It is fixed so as to sandwich the electrode at 22b. Upper holding frame 2
1 a is suspended by the support rod 23 on the upper flange 9 of the slush hydrogen container 1.

[0008] Lead wires (not shown) are connected to the electrodes 20a and 20b, and an AC voltage is applied to measure the generated AC current.

The method for measuring the density will be described below.

When the dielectric constant of the slush hydrogen 3 sandwiched between the electrodes 20a and 20b is ε, and the capacitance is C, the following equation is established.

C = Coε + Cd (1) Here, Co and Cd are constants determined by the electrode shape and the like.

On the other hand, the frequency f between electrodes having a capacitance C
When the AC voltage E is applied, Expression (2) is established between the AC voltage E and the flowing AC current I.

C = I / (2πfE) (2) Accordingly, the capacitance C is obtained, and the dielectric constant ε is obtained from ε = (C−Cd) / Co (3) obtained by modifying the equation (1).

The density ρ is obtained by a physical property table previously obtained as a relationship between the dielectric constant ε and the density ρ, or Clausius-Mossot.
It can be obtained using the equation ti = ρ (pε−1) / (ε + 2) (4) Note that p is a constant and is approximately 1.

[0015]

The above-mentioned conventional apparatus has the following problems. (1) For a mixture of solid and liquid phases, such as slush hydrogen,
A solid phase having a high density sediments below a liquid phase having a low density, and it is difficult to obtain a completely uniform state even by stirring with a stirrer. Therefore, since the density becomes non-uniform, the local density is measured, and the average density of the whole cannot be measured. (2) for blocking radiant heat from the ambient to the slush hydrogen and the like cryogenic fluids, the outer surface of the glass container is a radiation rate should make lower by aluminum deposition or the like, the manufacturing cost is high.

[0016]

The present invention employs the following means to solve the above-mentioned problems.

That is, as a cryogenic fluid density meter, a container for storing a cryogenic fluid having a non-uniform density and a mirror surface having a low emissivity are disposed so as to face each other along the inner surface of the container.
And the lower side is located near the lower surface of the container
Is, the upper side is provided with a first electrode and a second electrode disposed near the subsurface of the cryogenic fluid is placed in the container, most of the cryogenic fluid in the vessel and the first electrode second It was made to exist between two electrodes.

[0018]

In the above means, the cryogenic fluid of non-uniform density contained in the container has a dielectric constant which varies according to the density. Therefore, when the capacitance between the first electrode and the second electrode is measured, a value corresponding to the average dielectric constant of the fluid existing between the first electrode and the second electrode, that is, the average density is obtained.
That is, the average density of the fluid can be measured.

The shape and arrangement of the first electrode and the second electrode are such that most of the fluid in the container exists between them, so that a more accurate average density of the entire fluid in the container can be measured. it can. It is also located facing the inside of the container.
And the upper side is placed near the level of the cryogenic fluid in the container.
Outer surface of the electrode, with the lower side placed near the bottom of the container
Has a low emissivity because it is polished to a mirror surface.
In addition, the amount of heat entering the cryogenic fluid from outside can be reduced.
In addition, radiant radiation such as aluminum deposition on the outer surface of the container
No need to perform processing to lower the rate, reducing costs
Can be measured.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described with reference to FIGS.

The parts described in the prior art will be assigned the same reference numerals and their explanation will be omitted, and the parts related to the present invention will be mainly described.

In FIG. 1, a lower holder 31 made of an insulator having an outer surface having the same shape as the bottom surface a of the slush hydrogen container 1 for storing the slush hydrogen 3 is provided in contact with the lower surface of the container 1. The electrode 30 is disposed thereon. A ring-shaped upper holding frame 32 made of an insulator is arranged on the upper side of the electrode 30.

The details of the electrode 30 are shown in FIGS. The outer surfaces of the first electrode 30a and the second electrode 30b are formed along the inner surface of the container 1. These are opposed to each other, and the outer surface thereof is disposed in contact with the inner surface of the container 1, and is fixed by the lower holding table 31 and the upper holding frame 32.

At this time, a predetermined gap c is provided between the opposing sides. The lower sides d of the electrodes 30a and 30b are arranged as close to the bottom surface a of the container 1 as possible, and the upper side e is arranged near the lower surface of the liquid level b of the slush hydrogen 3 in the container.

The outer surfaces of the electrodes 30a and 30b are mirror-polished.

Further, the first electrode 30a and the second electrode 30b are connected to a capacitance meter (not shown).

In the above, when the capacitance of the first electrode 30a and the second electrode 30b is measured, the first electrode 30a and the second
An average dielectric constant ε of the slush hydrogen 3 existing between the electrodes 30b, that is, a value corresponding to the average density is obtained. That is, the average density of the slush hydrogen 3 can be measured.

The shape of the first electrode 30a and the second electrode 30b
The arrangement is such that the majority of the fluid in the container 1 is present between them, so that even if the mixing is poor, the container 1
More accurate average density of the slush hydrogen 3 in the inside can be measured.

Since a gap c is provided between the electrodes 30a and 30b, the inside slush hydrogen 3 can be observed from the outside. Further electrodes 30a, the outer surface of the 30b because that is a mirror-like, heat entering from outside emissivity rather low is reduced. In addition, there is no need to separately deposit aluminum or the like, so that cost can be reduced.

[0030]

As described above, according to the present invention, the average density of the entire cryogenic fluid having a non-uniform density in the container can be better measured, and the radiation of the outer surface of the container can be improved.
Processing to lower the Iritsu becomes unnecessary, it is possible to provide an inexpensive dense <br/> meter accuracy rather high.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of the overall configuration of an embodiment of the present invention.

FIG. 2 is an exploded view of the electrode unit of the embodiment.

FIG. 3 is a perspective view of an electrode unit of the embodiment.

FIG. 4 is a sectional view of the entire configuration of a conventional example.

FIG. 5 is a detailed view of an electrode section of the conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Slash hydrogen container 2,5 Vacuum insulation layer 3 Slash hydrogen 4 Liquid nitrogen container 6 Liquid nitrogen 7 Support stand 8,10 Rubber band 9 Upper flange 11 Upper flange support rod 12 Shield plate 13 Liquid hydrogen supply pipe 14 Vacuum inlet 15 Stirrer DESCRIPTION OF SYMBOLS 16 Motor 20, 20a, 20b Density meter electrode 21a, 21b Holding frame 22a, 22b Fixed rod 23 Density meter support rod 30, 30a, 30b Density meter electrode 31 Lower holding table 32 Upper holding frame

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Claims (1)

(57) [Claims] 1. A and container holding a density uneven cryogenic fluids, are disposed opposite along the inner surface of the container, the outer surface is
Both are in mirror-like, the lower side arrangement near the low surface of the container
The upper side is located near the liquid level of the cryogenic fluid.
A first electrode and a second electrode, wherein the majority of the cryogenic fluid in the container is present between the first electrode and the second electrode. Density meter for fluids.