JPH0735670A - Density meter for fluid of extremely low temperature - Google Patents

Abstract

PURPOSE:To enable measurement of a more accurate average density of the whole of a fluid by shaping and disposing first and second electrodes so that most of the fluid in a vessel may be present between them. CONSTITUTION:A first electrode 30a and a second electrode 30b are so shaped that the outside surfaces thereof are along the inside surface of a vessel 1, and the electrodes are opposed to each other, while the outside surfaces are so disposed as to be in contact with the inside surface of the vessel 1. The lower sides of the electrodes 30a and 30b are disposed as near to the bottom surface (a) of the vessel 1 as possible, while the upper sides thereof are so disposed as to be near to the lower side of a liquid surface (b) of slush hydrogen 3, for instance, in the vessel 1. Since the electrode 30a and the electrode 30b are shaped and disposed so that most of a fluid in the vessel 1 may be present between them, a more accurate average density of the slush hydrogen 3 in the vessel 1 can be measured even when a state of mixture is bad.

Description

Detailed Description of the Invention

[0001]

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

[0002]

2. Description of the Related Art There is slush hydrogen which is a mixture of solid hydrogen and liquid hydrogen as a cryogenic fluid having a non-uniform density. FIG. 4 shows an example of a dewar for a slush hydrogen production test in which a conventional density meter is installed. Reference numeral 1 denotes a slush hydrogen container, which has a hollow double structure, and the vacuum heat insulating layer 2 reduces heat entering the slush hydrogen 3 from the surroundings. A liquid nitrogen container 4 has a hollow double structure having a vacuum heat insulating layer 5 like the slush hydrogen container 1.

Liquid nitrogen 6 is filled in the liquid nitrogen container 4, and the invasion heat from the ambient room temperature is absorbed as the latent heat of vaporization of the liquid nitrogen 6, so that the slush hydrogen container 1 installed inside is absorbed. Invasion heat is reduced. The slush hydrogen container 1 and the liquid nitrogen container 4 are made of transparent glass for observing the production status of slush hydrogen. Further, in order to reduce the radiant heat, the outer surface is subjected to processing such as aluminum vapor deposition to increase the emissivity except for a portion which becomes an observation window. The liquid nitrogen container 4 is fixed to a support base 7 by a rubber band 8. The slush hydrogen container 1 is fixed to the upper flange 9 by the rubber band 10, and the upper flange 9 is fixed to the support base 7 by the rod 11.

Reference numeral 12 is a shield plate, and the upper flange 9
To reduce the heat entering the slush hydrogen container 1. Thirteen
Is a pipe for supplying liquid hydrogen, and 14 is a pipe for vacuuming.

For the slush hydrogen, the pipe 14 for vacuuming is connected to a vacuum pump (not shown), and the slush hydrogen container 1
It is manufactured by intermittently reducing the pressure and increasing the pressure (intermittent pressure reduction method). Reference numeral 15 is a stirrer, and 16 is a motor for driving the stirrer. The solid hydrogen produced by the intermittent depressurization method and the liquid hydrogen are stirred to produce sherbet-like slush hydrogen. 20 is an electrode for a capacitance type density meter,
It is suspended from the upper flange 9 by the support rod 23 and installed in the slush hydrogen 3.

FIG. 4 shows the detailed structure of the present capacitance type density meter.

Insulating holding frames 21a and 21b are provided on the upper and lower sides, and electrodes 20a and 20b facing each other are vertically arranged between them. The holding frames 21a and 21b are fixed rods 22a,
It is fixed so that the electrodes are sandwiched by 22b. Upper holding frame 2
1a is hung on the upper flange 9 of the slush hydrogen container 1 by the support rod 23.

A lead wire (not shown) is connected to the electrodes 20a and 20b, an AC voltage is applied, and the generated AC current is measured.

The method of measuring the density will be described below.

When the permittivity 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 is applied between the electrodes having the capacitance C.
When the AC voltage E is applied, the equation (2) is established between the AC voltage I and the flowing AC current I.

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

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

[0015]

The above-mentioned conventional device has the following problems. (1) In a mixture of solid and liquid phases such as slush hydrogen,
The solid phase having a high density settles downward from the liquid phase having a low density, and it is difficult to achieve a completely uniform state even by stirring with a stirrer. Therefore, the density becomes non-uniform, so that the local density is measured and the average density of the whole cannot be measured. (2) In order to block radiant heat from the surroundings to cryogenic fluid such as slush hydrogen, it is necessary to increase the emissivity on the outer surface of the glass container by vapor deposition of aluminum or the like, which increases the manufacturing cost.

[0016]

The present invention takes the following means in order to solve the above problems.

That is, as a density meter for a cryogenic fluid, a container for containing a cryogenic fluid having a non-uniform density, a container placed along the inner surface of the container and facing each other, and a lower side of which is near the lower surface of the container, A first electrode and a second electrode whose upper side is near the liquid surface of the cryogenic fluid are provided so that most of the cryogenic fluid in the container exists between the first electrode and the second electrode. I chose

[0018]

In the above means, the cryogenic fluid having a non-uniform density contained in the container has a dielectric constant which varies depending on 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.

Since 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, a more accurate average density of the entire fluid in the container can be measured. it can.

[0020]

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

The parts described in the conventional example are given the same reference numerals and the description thereof will be omitted, and the parts relating 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 containing the slush hydrogen 3 is provided in contact with the lower surface of the container 1. The electrode 30 is arranged thereon. An upper holding frame 32 made of a ring-shaped 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 in a shape along the inner surface of the container 1. These are arranged so as to face each other and have their outer surfaces in contact with the inner surface of the container 1, and are fixed by the lower holding base 31 and the upper holding frame 32.

At this time, a predetermined gap c is provided between the opposite sides. Further, the lower sides d of the electrodes 30a and 30b are arranged as close as possible to the bottom surface a of the container 1, and the upper sides e are arranged so as to be 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-finished.

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

When the electrostatic capacities of the first electrode 30a and the second electrode 30b are measured in the above, the first electrode 30a and the second electrode 30a are measured.
The value corresponding to the average dielectric constant ε of the slush hydrogen 3 existing between the electrodes 30b, that is, the average density is obtained. That is, the average density of slush hydrogen 3 can be measured.

Shapes of the first electrode 30a and the second electrode 30b
The arrangement is such that most of the fluid in the container 1 is present between them, so that the container 1
A more accurate average density of slush hydrogen 3 inside can be measured.

Since the gap c is provided between the electrodes 30a and 30b, the slush hydrogen 3 inside can be observed from the outside. Further, since the outer surfaces of the electrodes 30a and 30b are mirror-like, the emissivity is high and the heat entering from the outside is reduced. In addition, there is no need to separately deposit aluminum, and costs can be reduced.

[0030]

As described above, according to the present invention, it is possible to better measure the average density of the entire cryogenic fluid having a non-uniform density in the container, and to provide a highly accurate density meter. be able to.

[Brief description of drawings]

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

FIG. 2 is an exploded view of an electrode portion of the same embodiment.

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

FIG. 4 is a cross-sectional view of the overall configuration of a conventional example.

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

[Explanation of symbols]

 1 Slash Hydrogen Container 2,5 Vacuum Insulation Layer 3 Slash Hydrogen 4 Liquid Nitrogen Container 6 Liquid Nitrogen 7 Support 8,10 Rubber Band 9 Upper Flange 11 Upper Flange Support Rod 12 Shield Plate 13 Liquid Hydrogen Supply Pipe 14 Vacuum Outlet 15 Stirrer 16 Motors 20, 20a, 20b Densitometer electrodes 21a, 21b Holding frame 22a, 22b Fixed rod 23 Densitometer support rods 30, 30a, 30b Densitometer electrode 31 Lower holding stand 32 Upper holding frame

Claims (1)

[Claims] 1. A container for containing a cryogenic fluid having a non-uniform density, and a container which is disposed facing each other along the inner surface of the container, has a lower side near the lower surface of the container and an upper side of the liquid of the cryogenic fluid. A first electrode and a second electrode which are close to each other below the surface, and is configured such that most of the cryogenic fluid in the container exists between the first electrode and the second electrode. Density meter for cryogenic fluid.