U.S. patent number 3,612,334 [Application Number 04/777,761] was granted by the patent office on 1971-10-12 for container for cryogenic fluids.
This patent grant is currently assigned to The Bendix Corporation. Invention is credited to Paul J. Gardner.
United States Patent |
3,612,334 |
Gardner |
October 12, 1971 |
CONTAINER FOR CRYOGENIC FLUIDS
Abstract
A container having an inner and outer vessel for storing
cryogenic fluid. The inner vessel is concentrically separated from
the outer vessel by bumper members. The bumper members are spaced
on a conduit around the inner vessel. A shield member is located in
the space between the inner and outer vessel. A mounting member
attached to the conduit is secured to the shield member for
preventing direct contact between the outer vessel and the shield
member and thereby effectively reduce conductive heat transfer to
the inner vessel.
Inventors: |
Gardner; Paul J. (Davenport,
IA) |
Assignee: |
The Bendix Corporation
(N/A)
|
Family
ID: |
25111177 |
Appl.
No.: |
04/777,761 |
Filed: |
November 21, 1968 |
Current U.S.
Class: |
220/560.1;
220/4.25; 220/560.09; 220/560.13; 62/47.1 |
Current CPC
Class: |
F17C
3/08 (20130101); B65D 7/22 (20130101); F17C
2203/0646 (20130101); F17C 2260/033 (20130101); F17C
2223/0161 (20130101); F17C 2265/031 (20130101); F17C
2201/0128 (20130101); F17C 2203/0308 (20130101); F17C
2203/0391 (20130101); F17C 2203/015 (20130101); F17C
2203/0643 (20130101); F17C 2223/033 (20130101) |
Current International
Class: |
F17C
3/00 (20060101); F17C 3/08 (20060101); B65d
025/00 () |
Field of
Search: |
;220/9,9A,9D,15,14,10 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Davis, Jr.; Albert W.
Claims
It will be understood that the container for cryogenic fluids which
is herein disclosed and described is presented for purposes of
explanation and illustration and is not intended in indicate limits
of the invention, the scope of which is defined by the following
claims.
1. In a container for storing cryogenic fluids having an inner
vessel and an outer vessel separated by bumper members spaced on a
conduit surrounding the inner vessel, means for isothermally
isolating the inner vessel from the transfer of thermal energy from
the outer vessel, said means comprising:
a shield member surrounding said inner vessel, said shield member
dispersing radiant energy away from said inner vessel and toward
said outer vessel; and
means for mounting said shield member on said conduit for
preventing direct contact between said outer vessel and said shield
member to thereby reduce conductive heat transfer from said outer
vessel to said inner vessel.
2. In the container, as recited in claim 1, wherein said shield
member includes:
a first radiation shield surrounding said inner vessel at a
predetermined distance; and
a second radiation shield concentrically spaced from said first
radiation shield by low thermal conductive connector members and
attached to said mounting means.
3. In the container, as recited in claim 2 wherein said mounting
means includes:
tubular means surrounding said conduit having a progressively
increasing interior diameter from a midpoint contact with said
conduit for reducing the thermal conductive surface between said
conduit and said mounting means.
4. In the container, as recited in claim 3, wherein said mounting
means further includes:
clip members surrounding said tubular means having tab members;
and
body members extending through opening in said second radiation
shield, each of said body members having an internal groove for
retaining said tab members of the clip member for securing said
second radiation shield to said conduit.
5. In the container, as recited in claim 4 wherein said tubular
means is in the form of a spool constructed of a low thermal
conductive material.
6. In the container, as recited in claim 5 wherein said second
radiation shield will flex in the area of the edge of said openings
to permit said body members to pass through said opening until said
edge snaps into an external groove in each of said body
members.
7. In a container for storing cryogenic fluids having an inner
vessel and an outer vessel separated by bumper members spaced on a
conduit operatively connected to and interposed between the inner
and outer vessels, means for isothermally isolating the inner
vessel from the transfer of thermal energy from the outer vessel,
said means comprising:
a shield member surrounding said inner vessel, said shield member
dispersing radiant energy away from said inner vessel and toward
said outer vessel; and
means for mounting said shield member on said conduit for
preventing direct contact between said outer vessel and said shield
member to thereby reduce conductive heat transfer from said outer
vessel to said inner vessel.
8. A container for cryogenic fluids according to claim 7, wherein
said inner and outer vessels are hermetically sealed and the space
therebetween is evacuated to provide a vacuum insulation.
9. A container for cryogenic fluids according to claim 7 further
including an insulation layer on the outer surface of said outer
shell so as to further reduce heat transfer into said inner vessel.
Description
BACKGROUND OF THE INVENTION
The present invention relates to a container for cryogenic fluids,
and particularly to improvements for reducing heat input to the
fluids in such container. The present invention is an improvement
over devices of the type disclosed in U.S. Pat. No. 3,043,466,
granted July 10, 1962.
It is known when using containers of the type disclosed in U.S.
Pat. No. 3,043,466, to employ vacuum insulation, that is, to seal
hermetically the inner and outer vessels and to provide a vacuum
between the vessels. It is known also to provide other insulation
structure between the vessels to supplement the vacuum insulation.
For this purpose either a discrete radiation shield or a laminar
insulated shield may be employed.
A discrete radiation shield is a low emissivity radiation barrier
placed in the vacuum space and mounted to some support structure.
Laminar insulated shields are formed by adding a laminar type low
conductivity insulation to the emitting (least critical) side of
the discrete shield. In designs requiring light weight, where
construction costs permit the processing of high quality vacuum
space surfaces, there is limited useful application for laminar
insulations because thicknesses of laminar insulation necessary to
compete favorably with low emissivity-pure vacuum insulation are
too great. Without going into detail, it should be understood that
the function of each type of shielding is thus suited to a
different temperature region in actual application, and the present
invention is concerned primarily with the use of discrete radiation
shields. However, as will be apparent, the present invention can
also be used in conjunction with laminar insulated shields.
SUMMARY OF THE INVENTION.
According to one form of the present invention, a container for
cryogenic fluids is provided comprising inner and outer spaced
vessels, and at least one discrete radiation shield is mounted in
thermal isolation in spaced relation between the vessels. A cooling
conduit is mounted in heat transfer relationship along the inner
surface of the shield, and the conduit communicates with the
interior of the inner vessel and the exterior of the outer vessel.
The conduit has a restricted passageway for limited escape of the
cryogenic fluid or cold gas in the inner vessel to effect vapor
cooling of the shield. According to another form of the present
invention a similar construction and arrangement is provided
wherein the shield is laminar insulated, and the cooling conduit
extends in heat transfer relationship through the interior of the
laminar structure.
It is among the objects of the present invention to provide a
cryogenic container having improved insulation characteristics over
prior art structures by virtue of the isothermal mounting of at
least one radiation shield therein.
Other objects of this invention will appear in the following
description and appended claims, reference being had to the
accompanying drawing forming a part of this specification wherein
like reference characters designate corresponding parts in the
several views.
FIG. 1 is a view in side elevation, partly in section of a
container embodying one form of the present invention wherein vapor
cooling of two shields is provided;
FIG. 2 is an enlarged fragmentary sectional view through the
container illustrating the cooling conduit or circuit that is
employed in conjunction with the embodiment illustrated in FIG.
1;
FIG. 3 is a perspective view of a container of this invention, with
some parts broken away and other parts shown in section for the
purpose of clarity;
FIG. 4 is a fragmentary sectional view, similar to that of FIG. 2
but illustrating another embodiment of the invention wherein vapor
cooling of two laminar insulated shields is provided;
FIG. 5 is a sectional view of a shield mounting assembly in the
container of this invention; and
FIG. 6 is another sectional view of the shield mounting assembly as
seen from substantially the line 6--6 in FIG. 5.
Before explaining the present invention in detail, it is to be
understood that the invention is not limited in its application to
the details of construction and arrangement of parts illustrated in
the accompanying drawing, since the invention is capable of other
embodiments and of being practiced or carried out in various ways.
Also, it is to be understood that the phraseology or terminology
employed herein is for the purpose of description and not of
limitation.
In the embodiment of the invention illustrated in FIGS. 1--3, 5 and
6, the cryogenic container 10 includes an inner pressure vessel 12
fabricated of a suitable metal such as stainless steel, and an
outer vessel 14 which is in spaced relation to the inner vessel 12
and is preferably fabricated of an aluminum alloy. In the
illustrated embodiment of the container 10, the vessels 12 and 14
are spherical in shape and are concentrically arranged. The inner
vessel 12 is supported within the outer vessel 14 by an arrangement
which provides minimum thermal conductivity. This is accomplished
by a plurality of bumpers 16, only two of which are shown, but
normally it is contemplated that six or more such bumpers will be
employed. These bumpers and the manner in which they are
constructed and arranged form no part of the present invention, and
attention is directed to the aforementioned Letters U.S. Pat. No.
3,043,466 for a more detailed description. The vessels 12 and 14
are hermetically sealed and are typically spherical in shape so as
to permit the outer vessel to withstand loads imposed thereon
because of the high vacuum insulation that is provided between the
vessels.
Normally the inner and outer vessels 12 and 14 will have two
apertures with fittings for accommodating a fill line or conduit 18
and a vent line or conduit 20, which are shown in FIG. 1 but do not
appear in FIG. 3. These lines are supported by the bumpers 16 in
the manner illustrated and described in the aforesaid patent.
Two discrete radiation shields 22 and 24 are isothermally mounted
in spaced relationship between the inner and outer vessels 12 and
14. Connectors 25, only one of which is shown (FIG. 3) provide for
the support of one shield on the other. These discrete shields are
used to reduce the radiant heat input to the cryogen which normally
will be stored within the vessel 12. In the illustrated embodiment,
the shields are preferably formed from aluminum with a 0.015 wall
thickness.
The shields 22 and 24 are mounted in the container 10 of this
invention so that they are thermally isolated from the vessels 12
and 14. This is accomplished by utilizing materials having low heat
conductivity characteristics for supporting the shields 22 and 24
and by designing interfaces into the shield mounting structures. In
the illustrated embodiment of the invention, this is accomplished
by mounting each of the shields 22 and 24 on a plurality of
identical shield hanger assemblies 50, only one of which appears in
FIG. 3. A shield hanger assembly 50 is described in detail herein
with reference to the support of a shield on a fill conduit 18,
although it is to be understood that the assembly 50 can also be
assembled with other structure in the container 10 such as the
usual electrical leads and cables which are found therein but which
are not illustrated in the drawing.
As shown in FIGS. 5 and 6, the hanger assembly 50 includes a
substantially tubular spool member 52, formed of a material having
low heat conductivity characteristics such as Teflon. The spool 52
is of a progressively increasing diameter, on the inner surface 54
thereof, so that substantially midway between its ends it has an
annular edge 55 which is disposed in a supporting relation with the
tube 18. A thin stainless tape 56 is wound about the external
surface of the spool 52 and is tack-welded thereto so that there is
very poor thermal conductivity between the tape 56 and the spool
52. A clip 58 is disposed in a supporting relationship with the
tape 56 and is in turn supported at its ends in an internal groove
60 formed in an annular body 62 which is also formed of a material
having poor heat conductivity characteristics such as Teflon. The
body 62 is extended through an opening 66 in the shield 24 until
the shield 24 at the edge of the opening 66 snaps into an external
retainer groove 64 formed in the body 62.
It can thus be seen that the assembly 50 includes the spool 52 and
the body 62 of low heat conductivity materials and the tape 56 and
the clip 58 form interfaces therebetween for mimimizing heat
conductivity between shields 22 and 24 and vessels 12 and 14.
The function of the shields 22 and 24 to prevent heat transfer
between the vessels 12 and 14 is further enhanced by the provision
of a vapor cooling coil or conduit 26 (FIGS. 2 and 3) located in
the space between the inner vessel 12 and the outer vessel 14. The
coil 26 is very long and is of the serpentine shape shown in FIG.
3, and is illustrated in FIG. 2 as being of irregular shape only
for purposes of clarity to distinguish it from the shields 22 and
24. The coil 26 also has a low thermal conductivity relationship
between the shields 22 and 24 and the pressure vessel 12 and the
shields and the outer vessel 14. The inner end of the cooling coil
26 communicates with the inner end of the fill conduit 18, as shown
in FIG. 2, so as to be in communication with the interior of the
inner vessel 12, and the cooling coil 26 has its outer end attached
to an external fitting 28 on the outer wall of the outer vessel 14
so as to be in communication with the exterior of the outer shell
14. The cooling coil 26 extends along the inner surface of the
inner shield 22 and along the inner surface of the outer shield 24
in heat transfer relationship with respect to both such
shields.
The passageway within the coil 26 is restricted so as to permit a
flow situation to prevail whereby the cold cryogenic fluid or cold
gas from the inner vessel 12 can leak or escape through the coil 26
to cool the shields 22 and 24. This is called vapor cooling or
vapor expansion cooling depending upon whether fluid expansion
subcooling is employed. It is contemplated that an expansion
orifice 30 can be located between the inner tank 12 and the inner
shield 22, and a second expansion orifice 32 can be located between
the inner shield 22 and the outer shield 24. The object of the
conduit or coil 26 is to cool each shield emitting surface to a
temperature below the static heat transfer equilibrium temperature
by absorbing shield heat into the cold flowing fluid. It is
recognized that as the shield temperature is reduced, there is an
increase in outer wall heat radiation to the shield due to the
larger temperature differential; however, heat absorbed from the
shield by conduction to the colder exiting fluid causes a net
reduction of heat input to the internal cryogen vessel. Thus, by
virtue of the illustrated arrangement, the heat input to the inner
vessel 12 is minimized. By virtue of the length of the coil 26,
heat conductivity between the vessels 12 and 14 and the shields 22
and 24 is minimized.
In the embodiment illustrated in FIG. 4, essentially the same
construction as that shown in FIGS. 1-3, 5 and 6 is illustrated,
except that in this embodiment inner and outer laminar insulated
shields 22aand 24aare employed, and it will be observed that the
cooling coil 26aextends through the interior of the laminar
structure. The cooling coil 26aagain is in communication with the
inner vessel 12avia the conduit 18aand with the exterior of the
outer vessel 14a, and it has an expansion orifice 30abetween the
inner laminar insulated shield 22aand the inner vessel 12 aand an
expansion orifice 32abetween the shields 22aand 24a. Thus, this
arrangement provides an opportunity of employing a vapor cooling
coil as a heat transfer barrier so that a reasonably high
temperature differential can be maintained across the shield 22a,
and a similar temperature differential can be maintained across the
outer shield 24aand thus, low temperature will be maintained at the
emitting surfaces of the shields.
Also, changes in atmospheric temperature and high temperature
environment can be reduced by the addition of insulation, such as
the laminar type insulation shown at 33 in FIG. 4, to the exterior
of the outer vessel 14a. Furthermore, the outer vessel 14acan be
cooled by the flow of cold gas through the vapor cooling line 26aby
extending the line 26athrough the insulation 33, as shown in FIG.
4. This arrangement utilizes the unused heat absorbing capacity of
the escaping gas so that it exits to the atmosphere at a
temperature as nearly equal to that of the environment as possible
and in the process cools the outer vessel 14a. This reduces heat
transfer from the outer shell 14ato the inner vessel 12a.
From the above description it is seen that this invention provides
a container 10 for cryogenic fluids in which the inner vessel is
effectively insulated by the isothermally mounted discrete shields
22 and 24. By virtue of the isothermal mounting of the shields 22
and 24, they are thermally isolated from the vessels 12 and 14 and
the conduits 18 on which they are hung. Under "no flow" conditions,
only a radiation mode heat transfer exists in the container 10 and
a high performance is obtained from the shields 22 and 24 to limit
this transfer. Under "flow" conditions, the isothermally mounted
shields conserve the refrigerative capability of the cryogen in the
vessel 12 by eliminating or minimizing the conductive mode heat
transfer. Since for a given vessel size the peripheral surface area
is constant, maximum efficiency would occur with all conductive or
all radiant heat transfer. In the applicable temperature range of
0.degree. F. to -400.degree. F. a radiation mode heat transfer is
most effective since the heat transfer varies according to the
fourth power difference between the temperatures of two surfaces,
namely, the shield and pressure vessel surfaces; whereas, with a
conductive mode heat transfer, the heat transfer varies directly as
the temperature difference. In the container 10, conductive mode
transfer to the shields is practically eliminated and the shields
effectively reduce radiation mode heat transfer. The vapor cooling
coil 26 reduces the temperature differential between adjacent
vessel and shield surfaces to reduce radiation mode heat transfer,
and the coil 26 is of a length such that heat conductivity between
adjacent surfaces is negligible.
* * * * *