U.S. patent number 3,650,290 [Application Number 04/777,048] was granted by the patent office on 1972-03-21 for pressure control system for cryogenic fluids.
This patent grant is currently assigned to Air Reduction Company, Incorporated. Invention is credited to Walter B. Moen, George R. Spies.
United States Patent |
3,650,290 |
Moen , et al. |
March 21, 1972 |
PRESSURE CONTROL SYSTEM FOR CRYOGENIC FLUIDS
Abstract
Heat for maintaining operating pressure in a single phase
cryogen fluid at or above the critical pressure is provided by
controllably circulating a portion of the warmed delivery fluid in
heat exchange with the storage fluid. The circulated delivery fluid
is reheated and recombined with the remainder of the delivery
fluid. A regulator device having a double acting valve element
movable between two opposite positions controls flows respectively
to a pressuring heat exchanger coil and to a by-pass leading
directly to delivery.
Inventors: |
Moen; Walter B. (Berkeley
Heights, NJ), Spies; George R. (Murray Hill, NJ) |
Assignee: |
Air Reduction Company,
Incorporated (New York, NY)
|
Family
ID: |
26891038 |
Appl.
No.: |
04/777,048 |
Filed: |
November 19, 1968 |
Current U.S.
Class: |
137/339 |
Current CPC
Class: |
F17C
13/025 (20130101); F17C 2205/0326 (20130101); F17C
2250/0495 (20130101); F17C 2205/0332 (20130101); F17C
2203/0395 (20130101); F17C 2250/0439 (20130101); F17C
2221/017 (20130101); Y02E 60/32 (20130101); F17C
2221/014 (20130101); F17C 2270/025 (20130101); F17C
2227/0397 (20130101); F17C 2203/0629 (20130101); F17C
2201/032 (20130101); F17C 2221/033 (20130101); F17C
2227/0304 (20130101); F17C 2250/0421 (20130101); Y10T
137/6552 (20150401); F17C 2223/0161 (20130101); F17C
2227/0107 (20130101); F17C 2205/0338 (20130101); F17C
2227/0379 (20130101); F17C 2201/0109 (20130101); F17C
2221/011 (20130101); F17C 2227/0374 (20130101); F17C
2250/0626 (20130101); F17C 2250/0636 (20130101); F17C
2223/033 (20130101); Y02E 60/321 (20130101); F17C
2223/0115 (20130101); F17C 2221/016 (20130101); F17C
2221/012 (20130101) |
Current International
Class: |
F17C
13/00 (20060101); F17C 13/02 (20060101); F16k
049/00 () |
Field of
Search: |
;137/339,110,119
;62/52,51,50 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Scott; Samuel
Claims
We claim:
1. Apparatus for dispensing cryogenic fluids comprising;
an insulated container for holding a supply of said fluid;
an outlet from said container including means external of said
container for heating fluid discharged through said outlet;
a heat exchanger arranged in said container to pass a heating fluid
in indirect heat exchange with the fluid in said container;
a circulating conduit connected with said outlet for delivering
heated discharge fluid therefrom to said heat exchanger;
a discharge line connected with said outlet providing a bypass
conduit through which heated discharge fluid may bypass said heat
exchanger;
regulator means responsive to pressure within said container to
regulate the flow of heated fluid through said heat exchanger such
that the fluid contents of said container are thereby heated
sufficiently to maintain a desired pressure in said container;
said regulator means including throttling means operable in each of
said circulating conduit and said discharge line to proportion the
flow of heated discharge fluid therebetween.
2. Apparatus according to claim 1 wherein said regulator means
includes a regulator device having a single inlet connected with
said container outlet for receiving heated discharge fluid and two
outlet nozzles communicating respectively with said discharge line
and said circulating conduit;
and a single valve element moveable in operable relationship to
said outlet nozzles in response to displacement of diaphragm means
exposed to the pressure within said container.
3. A cryogenic fluid dispensing system comprising a container
having a delivery outlet;
a regulator having an inlet and first and second discharge outlets
each adapted to receive fluids from said inlet;
a valve element having an elongated passage in direct communication
with said inlet terminating in openings in opposite end faces of
said element;
first and second valve seat means respectively in said opposite end
faces surrounding the terminal openings of said passage;
said respective valve seat means being arranged to form valve
closures controlling the flow of inlet gas respectively to said
first and second discharge outlets;
spring bias means acting against said valve element to urge it
toward closed position against said first valve seat means;
diaphragm means exposed on one side to the pressure within said
container to oppose the force of said spring bias means;
and heat exchanger coil means in said container connected with said
second regulator outlet means to receive discharge fluid therefrom.
Description
The present invention is concerned particularly with systems for
the storing and dispensing the cryogenic fluids of the type
disclosed in the Balcar et al., U.S. Pat. No. 3,062,017. Such
systems store cryogenic substances such as oxygen, nitrogen, etc.,
in a single phase at or above the critical pressure of the fluid.
This system permits the storage of a maximum quantity of fluid for
a given weight of container since it is possible thereby to place
the greatest density of fluid into the container for the weight
required to withstand the corresponding pressures. Further by
storage of the fluid in single phase, it is possible to withdraw
and deliver the fluid when normal gravitational forces such as are
required for operation of two phase liquid storage systems, are not
fully effective. This occurs, for example, in space. Conditions
under which the normal influence of gravity is critically related
to the dispensing of the fluid occur also in air travel or undersea
exploration. In these situations the storage container may be
subjected to various orientations while in use. As a result a
continuous delivery of either the liquid or the gas is not assured
and the dispensing of the fluid is interfered with. In a
supercritical storage system of the type shown in the Balcar et
al., patent, the single phase fluid may be readily withdrawn
without dependence on the gravitational environment.
Aside from use of single phase storage of fluids to overcome
adverse gravitational considerations, such utilization is often a
necessity with certain cryogenic fluids having relatively low
critical pressures and critical temperatures and a narrow spread
between critical temperature and normal boiling point. Fluids
having extremely low critical temperatures and pressures, such as
helium, ordinarily cannot be maintained readily below the critical
temperature or the critical pressure and cannot be effectively
dispensed even at low pressures using conventional systems
dependent upon two fluid phases. In these cases, a single phase
dispensing system is necessary. In addition, heat is required with
such fluids to raise the operating pressure substantially above its
low critical pressure in order to dispense the fluid against
relatively high environmental absolute pressures such as in the
case of undersea use requiring increasingly higher pressures for
greater working depths.
In order to maintain effective operating pressure during withdrawal
of the single phase fluid, heat must be supplied to the storage
fluid. Systems such as have been applied heretofore for the
maintenance of operating pressure in two phase systems, i.e.,
liquid and gas, are not applicable to single phase type systems. In
general, the earlier pressure controlling arrangements have
inherently depended upon the existence of the liquid phase for
operation. In single phase systems with which the present invention
is concerned, there is of course, no such liquid phase and
consequently, it is necessary to develop an effective and unique
system which is specifically related to and effective for the
maintenance of pressure in such type systems without regard to
gravitational environment. In the Balcar et al. patent, a system
for imparting heat to a single phase system is shown. However, it
does not satisfy a number of practical requirements to which such
dispensing apparatus is subjected. In the system disclosed, for
example, a heater element operated by a thermally responsive switch
is operated intermittently to control the heating of the delivery
fluid that is circulated through a coil in heat exchange relation
with fluid in the vessel. Such a type of electrical heater,
however, is impractical and restrictive in many applications. For
example, it requires a source of electric heat always available in
conjunction with the vessel and dispensing system. This obviously
could be extremely cumbersome if not entirely precluded where the
vessel is intended to be portable, such as where it is used by a
diver undersea. Furthermore, the switch mechanism itself which
depends on solenoid or similar valve means affords a potential
source of difficulty since it represents mechanism disposed
externally of the fluid circuit.
Accordingly, it is the principal object of the present invention to
provide a storage and dispensing system for cryogenic fluids
maintained at supercritical pressure, which is operable
independently of gravitational influences, wherein a portion of the
delivery fluid is controllably circulated in heat exchange
relationship with the contents of the vessel to maintain the
desired operating pressure.
It is a further object of the invention that such means for heating
the contents of the vessel to maintain this operating pressure may
be independent of sources of electrical heating power and can
employ instead environmental heat as a source for heating the
fluid.
It is a still further object of the present invention to provide
such a system wherein the heat imparted to the vessel contents for
such purpose be controlled by effectively proportioning the flow or
quantity of delivery fluid circulated through heat exchanger means
for that purpose.
It is a still further object of the present invention to provide a
novel regulator device suitable for effecting such control and for
obtaining the necessary proportioning of the circulating fluid by
means of a double acting valve element which proportions the flow
of delivery fluid to a heat exchanger means within the vessel and
to a bypass going directly to the delivery outlet.
A fuller understanding of the invention together with other of its
objects and advantages may be had by reference to the following
description and the accompanying drawings in which:
FIG. I is a schematic representation of a cryogenic fluid container
and associated dispensing controls and delivery lines and
FIG. 2 is a schematic view showing portions of the cryogenic
container and associated delivery lines of a highly advantageous
regulating device for controlling the circulation of fluid for
maintaining pressure in the container.
Referring to FIG. I, the numeral 10 refers to a cryogenic vessel of
the so-called Dewar type which has an inner vessel 12 within an
outer vessel 14 so as to provide between them an evacuated space
16. In normal practice wrappings of reflective material may be
wound on the inner vessel to impede the passage of heat due to
radiation and, finely particulated material such as activated
charcoal may be placed in the evacuated space to act as a getter
which absorbs residual gas and aids in effectively maintaining a
high vacuum. The chamber 18 within the inner vessel receives the
cryogenic fluid to be maintained under appropriate pressure at the
time of dispensing. The chamber 18 is normally charged with fluid
as liquid through a suitable filling valve such as shown at 20 and
line 22. This same line 22 when the filling valve 20 is closed, as
will be hereinafter described, also serves as the discharge line
through which the cryogenic fluid is dispensed from the vessel. A
thermocouple shown at 24 is located within the chamber 18 and by
conventional means operates a temperature gauge 26 mounted or
otherwise positioned externally of the vessel to indicate the
temperature of the contents. The temperature reading of the gauge
26 as described in Balcar et al., U.S. Pat. No. 3,062,017 shows by
appropriate calibration the quantity of cryogenic material within
the container. This is related to the fact that at a constant
operating pressure, the density of the fluid within the container
progressively decreases as fluid is withdrawn. Correspondingly, the
temperature of the fluid must be gradually increased to maintain
the operating pressure while the density is decreasing.
Consequently calibration is possible showing at any particular
reading of the temperature gauge the quantity of fluid remaining in
the vessel.
The discharge line 22 externally of the vessel 10 connects with a
preheater coil 28. This coil may be of any suitable design
effective to heat the fluid therein by absorption of heat. Such
coil, for example, may utilize a series of fins 29 to enhance the
thermal exchange from the surrounding environment. Alternatively a
source of heat may be provided for absorption in the coil. A pair
of regulators 30 and 32 are connected at the downstream side of the
coil 28. The regulator 32 discharges through bypass conduit 33
directly to discharge line 34. An outlet valve 36 is operable to
open or close the line 34. The regulator 30 provides an alternate
path of flow through line 38 to a heat exchanger coil 40 within the
chamber 18, thence through reheating coil 42 to the discharge line
34. The regulator 30 serves as a pressure controller which controls
the flow of a divided portion of delivery fluid through heat
exchanger 40 to heat the single phase contents of chamber 18 when
it is necessary to increase the pressure. The regulator 32 serves
as a bypass which permits fluid from the preheating coil 28 to pass
directly to the discharge line 34, bypassing the path leading
through the heat exchanger coil 40. By appropriate settings of the
regulators 30 and 32, they function cooperatively such that the
delivery fluid is constantly proportioned between the coil 40 and
the bypass to maintain the desired operating pressure.
The regulators 30 and 32 utilize upstream pressurized fluid to load
a diaphragm control element in a manner that is well-known in the
art. Assuming for example, that the vessel 10 is intended to
operate at a pressure range of approximately 800-1,000 p.s.i.a.,
the regulator 30 may be adjusted to be fully opened at 800 p.s.i.a.
and fully closed at 1,000 p.s.i.a. The regulator 32 on the other
hand, may be so adjusted as to be fully closed at 800 p.s.i.a. and
fully open at 1,000 p.s.i.a. It will thus be seen that when the
pressure of the cryogenic fluid in chamber 18 is at or below the
level of 800 p.s.i., the fluid withdrawn from the chamber upon
opening the discharge valve 36 will flow entirely through the
regulator 30 and exchanger 40 in which heat imparted by preheater
coil 28 is applied to the contents of the chamber to increase the
pressure therein. As pressure begins to increase to a level above
800 p.s.i., the operation of regulator 32 will cause a suitable
proportion of the fluid coming from the coil 28 to bypass the heat
exchanger 40 and pass directly to the discharge line 34 where it is
combined with the portion of the fluid that continues to be
delivered through the heat exchanger 40. The two regulators will
then cooperate so as to deliver to the exchanger 40 whatever
portion of the fluid is necessary to maintain the pressure within
the range of 800 to 1,000 p.s.i. It will be seen that as the
pressure increases still further, the regulator 30 would be
progressively closed so that in the event the upper desired limit
of the pressure of the operating range is reached, the regulator 30
would be entirely closed and none of the fluid would be conducted
to exchanger 40 to impart additional heat to the contents of the
vessel. Consequently, as fluid continues to be withdrawn, the
pressure in the chamber 18 tends to decrease until such time as the
regulator 30 once more is caused to open and deliver additional
pressure building heat to the vessel.
The reheat coil 42 is intended to impart to the fluid that has
passed through the exchanger 40 substantially that amount of heat
which has been withdrawn from the fluid in heating the contents of
the vessel. Consequently, the fluid, after passing through the
reheat coil 42, is at a temperature comparable to that of the fluid
that passes directly to the discharge line 34 through the bypass
regulator 32.
Depending upon the particular application in which the vessel 10 is
to be used, there may be placed downstream of the discharge valve
36, a regulating device which is effective to reduce the pressure
of the fluid from the operating pressure of the chamber 18 to some
lower pressure. In the case, for example, of use for undersea
diving, this may be a depth responsive regulator which is arranged
to reduce the pressure to a level having a predetermined
differential from the ambient pressure of the surrounding sea. This
will vary of course according to the depth at which the diver may
be working. Such a regulator, for example, might be arranged as
shown at 44. A coil 46 is arranged to heat the delivery fluid to
substantially ambient temperatures to enhance the operation of
regulator 44 such as by preventing freezing and to permit
comfortable inhalation when the fluid is used for respiration.
There may be connected to the discharge end of the regulator 44 any
other valve or regulator means adopted for use of the fluid. In the
case of delivering oxygen for breathing purposes, a conventional
breathing demand regulator could be employed.
In order to avoid inadvertent over pressurization of the fluid
container, a pressure relief valve is provided in communication
with the chamber 18. This valve shown at 48 is connected to the
discharge end of the preheater coil 28 which thereby maintains the
relief valve in direct communication with the interior or the
vessel through the line 22. However, such valve can be connected in
any convenient manner.
Under normal conditions, the vessel 10 is filled to a predetermined
extent with cryogenic fluid at substantially lower pressure than
its normal operating pressure. In this manner, the cryogenic fluid
can be stored for a long period before the pressure within the
chamber rises to a point that may necessitate the venting of the
fluid to avoid over pressurization. In the event that it is desired
to place the vessel in operation before the chamber pressure has
risen to intended operating pressure, means are provided to enable
the pressure to be rapidly increased to such level. Such means
includes a preheat valve 50 which is connected to the outlet of the
pressure building regulator 30. The valve 50 connects directly with
the chamber 18 through a line 52. It will be seen that by opening
the valve 50, a continuous flow passage is formed through the line
22, coil 28, regulator 30 (which is open inasmuch as the pressure
within the chamber 18 is below the normal operating pressure) valve
50, line 51, and line 52. In the actual construction of the system
herein shown schematically, coil 28 is positioned at the bottom of
the vessel 10 when the system is in the vertical position so that
this open circuit forms a thermosyphon in which the fluid from the
container becomes heated in coil 28 and by convection results in a
thermosyphon effect that circulates fluid from the chamber 18
through the coil 28 and back to the chamber. By warrent of this
effect the heating of the fluid in the coil 28 progressively warms
and increases the temperature within the chamber 18 until the
desired operating pressure is achieved. At this point, the
discharge valve 36 is opened and the vessel 10 can be placed in
operation. For convenience, the line 52 may be connected with a
valve 54 which serves, when opened, to permit the venting of gas in
the chamber 18 when fluid is being introduced to the filling valve
20. After filling and during the period of storage and operation
this valve is closed.
An alternative embodiment of the invention combining into one
element, regulators 30 and 32 is shown in FIG. 2 of the drawing. In
this drawing, the equivalent parts of the apparatus have been
identified by the letter a and the same numeral as in FIG. 1. Thus
the cryogenic vessel equivalent to that shown at 10 in FIG. I is
indicated at 10a in FIG. 2 and so on. The chamber 18a contains the
cryogenic fluid to be dispensed. A control regulator device 60 is
provided to control the delivery of fluid from the container 18a
and to regulate the circulation of fluid through the heat exchanger
coil 40a within the chamber 18a and thereby maintain the desired
operating pressure. Regulator 60 is essentially the functional
counterpart of the regulators 30 and 32 of FIG. I. The regulator 60
has an inlet connection 62 to which the fluid from the chamber 18
is delivered through the line 22a and preheating coil 28a. An
outlet connection 64 delivers fluid through the heat exchanger 40a,
thence reheat coil 42a to the discharge valve 36a. An outlet 66
delivers fluid directly to the discharge valve 36a.
The housing of regulator 60 has a chamber 68 which communicates
with the outlet 64 and a chamber 70 which communicates with the
outlet 66. A reciprocating valve element 72 has valve seats 74 and
76 in its opposite end faces and a central bore 78 which
communicates with openings in the ends of the element surrounded by
the valve seats 74 and 76. The valve seats 74 and 76 are arranged
to seat respectively against annular nozzles 80 and 82 which define
the valve openings. The valve element is integrally mounted in a
diaphragm 84 which divides chamber 70 from a chamber 86 and is
subject to pressure within the chamber 70 to displace the valve
element. O-ring members 87 are disposed on the valve element to
effectively seal the chamber 68 from the intermediate chamber 86. A
spring 88 acts downwardly against the valve element 72 so as to
close the valve nozzle 80 until a predetermined pressure exists in
the chamber 70, causing the seat 74 to move away from seated
position against nozzle 80.
It may be seen that when the pressure within the chamber 18a is
below a predetermined value and seat 74 is closed, the pressure in
chamber 18a extends to the chamber 70 through line 22a, inlet 62,
passage 78, chamber 68, outlet 64, line 67, and outlet 66. The
fluid, therefore, upon opening of the valve 36a will flow through
line 22a, preheating coil 28a, inlet 62, bore 78 in the valve
element into chamber 68, past the open valve seat 76, and thence
through outlet 64 and heat exchanger coil 40a. Coil 40a then will
cause heating of the contents of chamber 18a and an increase in
chamber pressure. The fluid, after passing through the exchanger
40a, thence passes through the reheater coil 42a in which it is
rewarmed to compensate for the heat withdrawn in the heat exchanger
40a as discussed in connection with FIG. 1. When the pressure has
risen to a level sufficient for the pressure reflected in the
chamber 70 and acting on the underside of diaphragm 84 to overcome
the bias of the spring 88, the valve element will be unseated from
the nozzle 80 thus permitting the fluid to flow from the inlet 62
directly to the chamber 70 and thence outlet 66, line 67 to the
discharge valve 36a. Such fluid, therefore, bypasses the heat
exchanger coil 40a. As the pressure rises from heating by coil 40a
the valve element 72 will move further toward the nozzle 82 to
reduce flow to the coil and will close completely when the
operating pressure achieves a predetermined upper limit. The valve
element will continue to be adjusted between its opposite positions
against the nozzle openings 80 and 82 so that fluid entering the
inlet 62 is proportioned between the outlets 64 and 66 of the
regulator, causing only that amount of fluid to pass through the
coil 40a necessary to maintain the desired operating pressure.
In this embodiment, a relief valve 48a is provided by means of a
spring-loaded bellows 90 which acts against an opening 92 that
communicates directly with the bore 78 of the valve element,
thereby, maintaining constant and direct communication with the
interior of the chamber 18a. The filling valve 20a operates in the
same manner described in connection with FIG. 1. Similarly, a
preheat valve 50a is connected in the line 38a and is operable to
produce a thermosyphon effect as described in connection with FIG.
I to increase the storage pressure of the container to operating
level when it is desired to place the system in condition for
operation.
It will, of course, be understood that the operating pressures
employed in any installation will be a function of the particular
fluid in use. For example, in the case of oxygen whose critical
pressure is approximately 730 p.s.i.a. the operating pressure would
normally be at least about 1 percent above its critical pressure.
The operating range may extend from this pressure up to the maximum
pressure required for a particular use. As a general rule 1,500
p.s.i.a. will suffice. Under such conditions the fluid within the
chamber of the insulated vessel will consequently always be in the
single phase and the apparatus will function independently of the
orientation of the vessel or gravitational forces acting
thereon.
Examples of other cryogenic substances which may be used
advantageously in accordance with this invention and their critical
pressures are as follows:
Nitrogen 493 p.s.i.a. Argon 710 p.s.i.a. Helium 33.2 p.s.i.a.
Hydrogen 191 p.s.i.a. Methane 673 p.s.i.a.
The range of operating pressures with which the present invention
would generally be used is from about 1 percent above the critical
pressure thereof to the maximum working pressure required for
particular applications. Generally, pressures within the range up
to 1,500 p.s.i.a. will be sufficient.
As previously mentioned, an advantage of the present invention,
even if no significant gravitational problem exists, is in
facilitating the operation of the dispensing system at adequately
high pressures. For example, in the use of helium in undersea work,
operating pressures of as high as 1,500 p.s.i.a. may be desired
which is far above the critical pressure of helium. Input of heat
sufficient to maintain the helium at such operating pressures is
effectively accomplished in the manner hereinabove described.
The temperature of the fluid at the time of initial withdrawal will
depend upon several factors including the initial filling density
of the storage vessel, the operating pressure and the particular
fluid. In the case of a vessel typically filled to 90 percent with
liquid helium at 1 atmosphere, the temperature may be about
-403.degree. F., if it is desired to withdraw the helium at an
operating pressure of about 1,500 p.s.i.a. or about -450.degree. F.
at an operating pressure of about 35 p.s.i.a. As quantities of the
fluid are withdrawn, the temperature will be progressively
increased and may reach normal atmospheric temperature or whatever
temperature level is required to withdraw a specified amount of the
contents from the storage vessel.
In general, the cryogenic substances with which the present
invention is concerned, are utilized by maintaining a body of such
substance at an extremely low temperature in a thermally insulated
zone to which heat is controllably introduced as hereinabove
described. For the purpose of this disclosure, a cryogenic
substance may be regarded as a substance having a boiling
temperature below -150.degree. C.
It will be understood that changes may be made in the methods and
apparatus set forth hereinabove without departing from the spirit
of the invention or exceeding the scope thereof as defined in the
following claims.
* * * * *