US-12625103-B2 - Void fraction sensor, flowmeter using the same, and cryogenic liquid transfer pipe

US12625103B2US 12625103 B2US12625103 B2US 12625103B2US-12625103-B2

Abstract

A void fraction sensor according to the present disclosure includes an insulating inner pipe having a through hole through which a low-temperature liquid flows, at least a pair of electrodes mounted on an outer peripheral surface of the insulating inner pipe, and a heat insulating layer covering an outer peripheral side of the insulating inner pipe. A flowmeter according to the present disclosure measures a flow rate of a cryogenic liquid flowing through the through hole of the insulating inner pipe, and includes the void fraction sensor described above, and a flow velocity meter that measures a flow velocity of the cryogenic liquid flowing through the through hole.

Inventors

Katsumi Nakamura

Assignees

KYOCERA CORPORATION

Dates

Publication Date: 20260512
Application Date: 20211209
Priority Date: 20201209

Claims (16)

1 . A void fraction sensor, comprising: an insulating inner pipe having a through hole through which a cryogenic liquid flows; at least one pair of electrodes mounted on an outer surface of the insulating inner pipe; and a heat insulating layer covering an outer peripheral side of the insulating inner pipe, wherein the void fraction sensor further comprises: an annular portion provided at both ends of the insulating inner pipe; an outer pipe bonded to an outer peripheral portion of the annular portion and having a first insertion hole; and a first hermetic terminal provided in the first insertion hole and in which a conductive pin is fixed, the conductive pin connected to a corresponding electrode of the at least one pair of electrodes, in the first insertion hole, wherein the heat insulating layer is a vacuum space located between the insulating inner pipe and the outer pipe, wherein the first hermetic terminal comprises the conductive pin, a ceramic substrate having a disk shape and a first pin hole in a thickness direction in which the conductive pin is inserted, and an annular body surrounding an outer peripheral surface of the ceramic substrate, and the annular body is made of a Fernico alloy, an Fe—Ni alloy, an Fe—Ni—Cr—Ti—Al alloy, an Fe—Cr—Al alloy, an Fe—Co—Cr alloy, an Fe—Co alloy, an Fe—Co—C alloy, or an austenitic stainless steel having a nickel content of at least 10.4 mass %.
2 . The void fraction sensor according to claim 1 , wherein the insulating inner pipe comprises a metal pipe having a flange at at least one end of the insulating inner pipe, and the annular portion and the flange are welded or brazed together.
3 . The void fraction sensor according to claim 1 , wherein the insulating inner pipe is made of a low thermal expansion ceramic.
4 . A flowmeter for measuring a flow rate of a cryogenic liquid flowing through a through hole of an inner pipe, comprising: the void fraction sensor according to claim 3 ; and a flow velocity meter that measures a flow velocity of the cryogenic liquid flowing through the through hole.
5 . A cryogenic liquid transfer pipe comprising: the flowmeter according to claim 4 .
6 . A void fraction sensor, comprising: an insulating inner pipe having a through hole through which a cryogenic liquid flows; at least one pair of electrodes mounted on an outer surface of the insulating inner pipe; and a heat insulating layer covering an outer peripheral side of the insulating inner pipe, wherein the insulating inner pipe is composed of an even number of dividable ceramic members arranged in a circumferential direction, and the void fraction sensor further comprises: a housing surrounding the insulating inner pipe and having a second insertion hole and a connection hole communicating with the through hole of the insulating inner pipe; an annular portion located outside of the housing and having an axial hole coaxial with the insulating inner pipe; an outer pipe bonded to an outer peripheral portion of the annular portion and having a first insertion hole; a first hermetic terminal fixing a conductive pin in the first insertion hole, the conduct pin connected to a corresponding electrode of the at least one pair of electrodes; and a second hermetic terminal fixing the conductive pin in the second insertion hole, and a vacuum space is located at least between the outer pipe and the housing.
7 . The void fraction sensor according to claim 6 , wherein the first hermetic terminal and the second hermetic terminal each comprise the conductive pin, a ceramic substrate having a disk shape and a pin hole in a thickness direction in which the conductive pin is inserted, and an annular body surrounding an outer peripheral surface of the ceramic substrate, and the annular body is made of a Fernico alloy, an Fe—Ni alloy, an Fe—Ni—Cr—Ti—Al alloy, an Fe—Cr—Al alloy, an Fe—Co—Cr alloy, an Fe—Co alloy, an Fe—Co—C alloy, or an austenitic stainless steel having a nickel content of at least 10.4 mass %.
8 . The void fraction sensor according to claim 6 , wherein the insulating inner pipe has a recessed portion which is open toward the outside of the housing, and each electrode of the at least one pair of electrodes is mounted on a bottom surface of the recessed portion.
9 . The void fraction sensor according to claim 6 , wherein electrodes of the at least one pair of electrodes are individually mounted on each of at least the pair of opposing ceramic members among the even number of ceramic members.
10 . The void fraction sensor according to claim 6 , wherein the dividable ceramic members are bound by an annular binding body mounted on an outer peripheral side of the insulating inner pipe.
11 . The void fraction sensor according to claim 6 , wherein an end surface and/or an outer side surface of the insulating inner pipe is in contact with an inner surface of the housing.
12 . The void fraction sensor according to claim 6 , wherein the housing comprises a frame body accommodating the insulating inner pipe, and a cover portion sealing an opening of the frame body, an opening of the frame body and an opening of the cover portion each communicate with the through hole of the insulating inner pipe, and a metal pipe is welded or brazed to the frame body and the cover portion to communicate with the through hole via the opening of the frame body and the opening of the cover portion.
13 . The void fraction sensor according to claim 12 , wherein the annular portion is welded or brazed to the metal pipe.
14 . The void fraction sensor according to claim 6 , wherein the insulating inner pipe is made of a low thermal expansion ceramic.
15 . A flowmeter for measuring a flow rate of a cryogenic liquid flowing through a through hole of an inner pipe, comprising: the void fraction sensor according to claim 6 ; and a flow velocity meter that measures a flow velocity of the cryogenic liquid flowing through the through hole.
16 . A cryogenic liquid transfer pipe comprising: the flowmeter according to claim 15 .

Description

TECHNICAL FIELD The present disclosure relates to a void fraction sensor for measuring a void fraction of a cryogenic liquid such as liquid hydrogen, a flowmeter using the same, and a cryogenic liquid transfer pipe. BACKGROUND OF INVENTION With the recent trend of reducing greenhouse gas emissions, the use of hydrogen as a potent energy storage medium has been attracting attention. In particular, liquid hydrogen has a high volumetric efficiency and can be stored for a long period of time, and various techniques for utilizing liquid hydrogen have been developed. However, a method for accurately measuring the flow rate which is required in handling a large volume of liquid hydrogen for industrial use has not been established. A major reason for this is that liquid hydrogen is a fluid which is very easily vaporized and has a large fluctuation of gas-to-liquid ratio that fluctuates largely. That is, liquid hydrogen is a liquid having an extremely low temperature (boiling point −253° C.) and having very high thermal conductivity and low latent heat, which causes immediate generation of voids. Therefore, in a transfer pipe, liquid hydrogen is in a so-called two-phase flow in which gas and liquid are mixed. Because of the large fluctuation of the void content percentage, the flow rate of the liquid hydrogen cannot be accurately determined by only measuring the flow velocity in the pipe, as in ordinary liquids, when measuring the flow rate of the liquid hydrogen flowing in the pipe. In view of the above, a void fraction meter that measures a void fraction indicating a gas phase volume percentage of the gas-liquid two phase flow is under development. As such a void fraction meter, Non-Patent Document 1 has proposed a capacitance type void fraction sensor that measures capacitance using a pair of electrodes. CITATION LIST Non-Patent Literature Non-Patent Document 1: Norihide MAENO et al. (5), “Void Fraction Measurement of Cryogenic Two Phase Flow Using a Capacitance Sensor”, Trans. JSASS Aerospace Tech. Japan, Vol. 12, No. ists29, pp. Pa_101-Pa_107, 2014 SUMMARY Problem to be Solved A void fraction sensor according to the present disclosure includes an insulating inner pipe having a through hole through which a cryogenic liquid flows, at least one pair of electrodes mounted on an outer peripheral surface of the insulating inner pipe, and a heat insulating layer covering an outer peripheral side of the insulating inner pipe. A flowmeter according to the present disclosure measures a flow rate of a cryogenic liquid flowing through a through hole of an insulating inner pipe, and includes the void fraction sensor described above, and a flow velocity meter that measures the flow velocity of the cryogenic liquid flowing through the through hole. The present disclosure also provides a cryogenic liquid transfer pipe provided with the flowmeter described above. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic cross-sectional view illustrating a void fraction sensor according to an embodiment of the present disclosure. FIG. 2 is a schematic cross-sectional view illustrating a void fraction sensor according to another embodiment of the present disclosure. FIG. 3A is a cross-sectional view illustrating an assembly structure of the insulating inner pipe illustrated in FIG. 2. FIG. 3B is an explanatory view illustrating dividable ceramic members illustrated in FIG. 3A. FIG. 4 is a partially cutaway perspective view of a variation of the void fraction sensor illustrated in FIG. 2. FIG. 5 is a partially cutaway perspective view of the insulating inner pipe and its surrounding structure illustrated in FIG. 4. FIG. 6 is a perspective view of the insulating inner pipe illustrated in FIG. 4. DESCRIPTION OF EMBODIMENTS Hereinafter, a void fraction sensor according to an embodiment of the present disclosure will be described. A void fraction sensor that measures a void fraction when liquid hydrogen is used as a cryogenic liquid will be described. FIG. 1 illustrates a void fraction sensor 1 according to an embodiment of the present disclosure. As illustrated in FIG. 1, a void fraction sensor 1 includes an insulating inner pipe 2 having a through hole 3 through which liquid hydrogen flows, and an even number (two in the present embodiment) of electrodes 4 mounted on an outer surface of the insulating inner pipe 2. An annular portion 5 is attached to an outer peripheral portion at both ends of the insulating inner pipe 2, and an outer pipe 6 is bonded to an outer peripheral portion of the annular portion 5. The outer pipe 6 has a first insertion hole 7 which opens radially. A first hermetic terminal 8 is provided in the first insertion hole 7, and a conductive pin 9 connected to a respective one of the electrodes 4 is fixed in the first insertion hole 7. The insulating inner pipe 2 is an inner pipe having a volume resistance value of at least 1010 Ω·m at 20° C. The outer pipe 6 has a vacuum exhaust valve 15 (for example, a needle valv