US3197972A - Liquified gas transferring system - Google Patents

Description

Aug. 3, 1965 R. 0- KING LIQUIFIED GAS TRANSFERRING SYSTEM 2- Sheets-Sheet 1 Filed NOV. 27, 1961 Aug. 3, 1965 R. Q. KING 3,197,972

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United States Patent 3,197,972 LIQUIFIED GAS TRANSFERRING SYSTEM Robert Q. King, Escondido, Calif., assignor to Union Tank Car Company, Chicago, 111., a corporation of New Jersey Filed Nov. 27, 1961, Ser. No. 155,061 3 Claims. (or. 62-55) This invention relates in general to the vaporization of liquids. It deals more particularly with an improved device and method for effecting the vaporization of a liquefied gas.

It is an object of this invention to provide a new and improved vaporizer.

It is another object to provide a vaporizer the natural convection of atmospheric air.

It is still another object to provide a vaporizer, the effectiveness of which is not impaired by moisture in the air.

It is yet another object to provide a vaporizer which effects more beneficial heat transfer between the air and a liquefied gas than has been realized with devices heretofore utilized.

It is a further object to provide a vaporizer including a heat transfer passage of relatively small cross sectional area and substantial length which efiects superior heat transfer between the air and a liquefied gas.

It is still a further object, to provide a vaporizer which, to a great extent, effects extremely eflicient nucleate boiling of the liquid being vaporized.

It is yet a further object to provide a highly efiicient pressurizing system for liquefied gas storage tanks.

It is another object to provide a pressurizing system of the type referred to above which does not require an outside power source to effect efficient utilization of atmospheric air.

It is still another object to provide a pumping system for liquefied gas storage tanks which is simpler and less expensive than any system presently utilized.

It is another object to provide an improved method for controlled vaporization of a liquefied gas.

It is still another object to provide an improved method of pumping a liquefied gas out of a storage tank.

These and other objects of this invention are facilitated by providing a new and improved vaporizer and method of vaporizing a liquefied gas. Briefly, the invention contemplates a vaporizer which incorporates a substantially long enclosed passage of relatively small cross sectional area through which atmospheric air is drawn solely by natural convection. Means are provided for passing the liquid through an area surrounded by.moving atmospheric air. As the low temperature liquid is passed through this area, it acquires its heat of vaporization from the atmospheric air and is vaporized. A portion of the vaporizer effects a de-humidification of the atmospheric air while a succeeding portion eifects the main body of heat transfer requisite to the beneficial vaporization of such a liquefied gas.

The invention, both as to its organization and method of operation, taken with further objects and advantages thereof, will best be, understood by reference to the folwhich utilizes lowing description taken in connection with the accom- 3,197,972 Patented Aug. 3, 1965 Referring now to the drawings, and particularly to FIG- URE 1, a tank car is shown generally at 10. Mounted on the side of the tank car by any conventional means, such as brackets 11, is a vaporizer 12 embodying the features of this invention. The tank car is of the type constructed to carry LOX (liquid oxygen). 0n the other hand, it might carry one of several other liquefied gases having extremely low boiling points (less than about 230 K.), including liquid nitrogen.

In' this instance, the vaporizer 12 is adapted to induce a pressure build-up within the tank car 10 to effect a pumping of the LOX from the car. Since the vaporizer 12 finds advantageous application as a pumping system for a tank car, the succeeding discussion will be couched in terms of such a system to simplify an understanding of the invention. However, it will be readily understood that the principles of the invention find advantageous application in numerous systems requiring the vaporization of a liquefied gas.

To pump the LOX stored in the tank 10 into a liquid fueled missile, for example, a pressure build-up is effected in the tank by metering a small portion of the LOX stored in the tank car through the vaporizer 12. The vaporizer effects heat transfer between the atmospheric air and the LOX and a boiling of the LOX results as it picks up its heat of vaporization from the warmerair. Consequently, the LOX is vaporized and passes out of the vaporizer 12 and back into the tank car 10 above the level of the liquid stored inside the tank car to build up pressure within the car and cause the stored LOX in the car to be pumped out.

As will be seen in FIGURE 1, a LOX inlet pipe 13 connects the tank car 10 with the vaporizer 12 and is adapted to meter LOX from the car to the vaporizer. A vapor outlet pipe 14 connects the discharge end of the vaporizer 12 to the tank car 10.

Referring now to FIGURES 2 and 3, the vaporizer 12 is shown to include a generally irregularly shaped housing 20 which encloses a heat transfer complex 21. The LOX courses in one direction through the housing 20 inside the heat transfer complex 21 while the atmospheric air passes in the other direction through the housing 20 in surrounding relationship to the heat transfer complex 21. The LOX is vaporized during its passage through the complex 21 whereupon it returns to the tank car 10 and eifects a pressure build-up and consequent pumping of the remaining LOX out of the tank car, as has been pointed out.

The housing 20 includes a rolled sheet metal top 22 and a bottom 23. Appropriately shaped side walls 24, of rolled metal construction also, connect the top 22 and the bottom 23. The walls and the bottom might be joined by any conventional means such as welding, for example. Secured over the inlet end of the housing 20 is an expanded metal cover 25, while the discharge end of the housing is open, as at 26. The relatively warm atmospheric air enters the housing through the expanded metal cover 25 and is discharged in relatively cool condition at the discharge end 26.

The heat transfer complex 21 which carries the LOX through the housing 20, is supported within the housing by a spaced pair of support plates 30. The support plates 30 are or irregular configuration corresponding generally to the configuration of the side walls 24 (see FIGURE 2). The plates 30 are spaced apart within the housing 20 and secured to the top 22 and bottom 23 of the housing by any well known means, such as welding.

The heat transfer complex 21, which is supported by the plates 30, includes an inlet header 35, an outlet header 36, and a series (seen generally at 37) of superimposed serpentine pipe assemblies 39-44 which interconnect the inlet header 35 and the outlet header 36. The inlet header 35 receives LOX through the inlet pipes 13 whereupon the LOX passes through one of the Pipe assemblies 39-4-4 to the outlet header 36. It is vaporized i-n the process, and the vaporpasses out of the header 36 through the outlet pipe 14.

Referring specifically to FIGURE 2, the superimposed series 37 of serpentine pipe assemblies 39-44 are substantially identical to each other. They each define a generally arcuate path in side elevation from the inlet header 35 to the outlet header 36.

The heat transfer complex 21 is divided into a precooling section 56 (broadly that portion of the series 37 of pipe assemblies 39-44 to the right of line A in FIG- URE 2) which effects a de-humidification of the incoming atmospheric air, and a main transfer section Sll .(broadly that portion of the series 37 to the left of line A) which effects the greater portion of the vaporization of the LOX accomplished by the vaporizer 12. In this light, it will be seen that the pro-cooling section 56 is immediately adjacent the expanded metal cover 25 and extends but a relatively small portion of the length of the housing 2%), while the heat transfer section 51 occupies the greatest portion of the housing 2% and is adjacent, relatively speaking, the discharge end 26 of the vaporizer.

Each of the pipe assemblies 39-44 is substantially identical in configuration and is adapted individually to convey LOX from the inlet header 35, thr-ough a vaporization process as the LOX passes through the length of the pipe assembly, to the outlet header 36 in vapor form. Since the structure of each pipe assembly is identical, with but minor insignificant exceptions, only the pipe assembly 39 will be described in detail.

, Referring now to FIGURE 3, the serpentine pipe assembly 39 is shown in fragmentary plan view. It includes a generally regularly spaced-series of bare pipes 6t), extending in generally parallel relationship and supported in aligned apertures 61 in the support plates 3th. The pipes 60 are preferably composed of a highly heat conductive copper alloy and secured to the support plates 30by any conventional means such as brazing or the like. A fitting 62 provides communication between the outlet header 36 and the pipe 66 which is closest to the expanded metal cover 25. The succeeding pipes 60 are however, and any highly conductive material might beused.

That portion of the pipe assembly 39 which has bee described to this point, along with like portions of the underlying series of pipe assemblies 49-44, make up the pre-cooling section 50 of the heat transfer complex 21. As has been pointed out, the pre-cooling section 56 effects a de-humidification of the atmospheric air as it moves into the vaporizer through the expanded metal cover 25. As has been also pointed out, the pipes 60 are bare and spaced a substantial distance apart. This is important because frost, of course, builds up on each pipe 60 as Water vapor is deposited. Since the pipes 6!) are spaced .a reasonable distance apart, however, the passage' of atmospheric air through the inlet section 50 is not impeded or blocked by the build up of frost.

Still referring to FIGURE 3, the remaining portion of the pipe assembly 39, along with like portions of the underlying series of pipe assemblies 49-44, make up the primary heat transfer section 51 of the heat transfer complex 21. Those portions of the pipe assemblies 39-44 which comprise the primary transfer section 51 include a series of generally regularly spaced pipes 65, extending in generally parallel relationship and supported in aligned apertures 66 in the support plates 36. The pipes 65 are also preferably" composed of a highly conductive copper alloy and secured. to the support plates 30 by brazing or the like. A fitting 67 provides communication between i the inlet header 35 and that pipe '65 which is closest to the discharge opening 26 of the housing 26. The remain ing pipes 65 are then connected in communication with each other by the generally U-shaped fittings 63 which have been hereinbefor-e referred to. The use of a copper alloy in the fitting 67 is preferred, of course, although as has been pointed out, other highly conductive materials might be used.

A series of fins 7l, also preferably composed of a copper alloy, are mounted on the surface of each of the pipes 65 in a well known manner to provide a highly efficient heat transfer medium between the atmospheric air within the housing as and the LOX within the pipes 65. The fins 71 might be mounted on corresponding pipes 65 in substantially closely packed relationship to provide the maximum surface area possible for heat transfer. That portion of the heat transfer complex which contains finned pipes 65, and is referred to as the primary heat transfer section 51, accomplishes the greatest proport-ion of the effective vaporization of LOX enclosed within the pipe assemblies 39-44, as has been pointed out; after the pre-cooling section 5t) has substantially de-humidified the air entering the housing 243.

In operation, a small amount of LOX is metered through the LOX inlet pipe 13 to the inlet header 35 and into each of the pipe assemblies 39-44. This passage of LOX is effected solely by the head of LOX in the tank car 19. In this light, of course, the vaporizer 12 must always be mounted low, relative to a tank. An immediate cooling of the air within the housing 20 adjacent the discharge end 26 of the housing 2% begins to take place. In contrast, of course, an immediate warming of the LOX entering the vaporizer l2 coincidentally begins to take place. Remembering now that the housing 20 is relatively long and has a relatively small cross sectional area, it will be seen that the enclosed passage between the expanded metal cover 25 and the discharge end 26 of the housing 20 will act as a chimney and the warmer atmospheric air adjacent the expanded metal cover will actually be drawn toward the now colder portion of the housing 20 adjacent the discharge end, by convection.

v This is a continuing process, of course, and more warmer air is consequently drawn into the housing 20 through the expanded metal cover 25. The chimney effect afforded by the long passage formed Within the housing 20 enables the vaporizer 12 embodying the features of this invention to operate without an external power source for moving the atmospheric air through the housing 20. For example, in the past it has been common practice to use power driven fans of one type or another for such a purpose. In the few instances where forced circulation can be eliminated, as in the vaporizer shown in the Enger et al. Patent No. 2,823,521, it is eliminated only where a substantially low capacity and rate of volatilization is required. This is true because the Enger et al. device,

it must be carefully controlled.

As the moisture-laden atmospheric air enters the precooling section 50 of the heat transfer complex 21 in vaporizer 12, through the expanded metal cover 25, it is pre-cooled and consequently substantially de-humidified by the cold gas, or gas and liquid mixture, in the pipes 60. Frost tends to build up on the pipes 60 but, as has been pointed out, because the pipes are bare and spaced at a substantial'distance apart, any build up of frost does not block the passage of air through the housing 20. In addition, the relatively high velocity rush of air through the housing 20, induced by the chimney design, tends to flow some of the frost which does form on the pipes 60 through the housing. Consequently, the passage of substantially de-humidified air to the primary heat transfer section 51 is assured.

Since the air which reaches the primary heat transfer section 51 is substantially de-humidified, there is no significant buildup of frost on the fins 71 carried by the pipes 65. This lack of frost in turn assures the free passage of atmospheric air through the heat transfer section. It will be seen, of course, that a build up of frost on the fins '71 could easily effect a. complete blocking of the passage of air through the vaporizer 12 since the fins extend into generally close relationship with each other longitudinally of each pipe 70 and with the fins on adjacent pipes 70. The use of substantially de-humidified air in this manner represents a departure from conventional practice. In Vaporizers which are widely used today, for example, by the time the air has become substantially de-humidified it is exhausted from the unit.

By virtue of the substantially long housing 20 through which air must pass, itwill readily be understood that the air temperature gets very low before theair is exhausted from the vaporizer. Such low temperatures tend to reduce the vapor film which ordinarily forms on the inside of the pipes 65. Consequently, film boiling tends to be replaced by nucleate boiling'and the efiiciency of the vaporizer is greatly increased. In the ultimate case, of course, film boiling will be entirely replaced by nucleate boiling. This situation could probably be expected only in large vaporizer units.

Numerous advantages flow from the unique construction embodying the features of this invention. For example, as has been pointed out, no external power source is required to operate the vaporizer 12 since the movement of air is effected by natural convection alone, and not by any fan or the like. This means, of course, that the vaporizer 12 can be utilized as a tank car pump for liquefied gas, under any conditions and in any locale. Whether or not there is a power source, such as a source of electricity is unimportant, whereas with conventional Vaporizers of the type presently utilized, fans associated therewith are conventionally driven by electric motors.

In this light, the vaporizer 12 embodying the features of this present invention finds advantageous application with conventional vertically disposed storage tanks of one type or another as well as with tank cars. Where a vaporizer is used as a pump for such a tank, of course, the configurations of the housing and the enclosed heat transfer complex are different. For example a vertically disposed tank would preferably have a vaporizer with a rectangular walled, box-like housing configuration enclosing correspondingly shaped pipe assemblies. The shape of the vaporizer 12, which has been described in association with the tank car 10, is as it is merely to conform to the side of the tank car to prevent the vaporizer from being damaged.

In either case, doing away with an electric motor or its counterpart as a power converter in a vaporizer obviously makes it a considerably less expensive unit than its counterparts of the powered variety. In addition, the lack of moving parts is consistent with long service life and virtually no maintenance.

It is, of course, due primarily to the fact that the air passage incorporated in the vaporizer 12 is substantially long, with a relatively small height or thickness, so as to 6 6 without blocking or in any way shutting off the supply of air to the succeeding primary heat transfer section 51 of the vaporizer. The heat transfer section is, of course, comprised of conduits having closely spaced fins of a highly conductive material mounted thereon. An extremely effective vaporizer combination is the result.

In its preferred use as a pumping means for unloading tanks containing cryogenic liquids, for example, it finds an ideal application. Pumping is effected more quickly and less expensively than heretofore realized possible with generally similar equipment.

While an embodiment described herein is at present considered to be preferred, it is understood that various modifications and improvements may be made therein, and it is intended to cover in the appended claims all such modifications and improvements as fall within the true spirit and scope of the invention.

What is desired to be claimed and secured by Letters Patent of the United States is:

1. In combination, a container for storing a liquified gas and a system forpumping said liquified gas from said container with energy derived solely from the natural environment of the system, said container comprising a horizontally disposed, generally cylindrical tank, said pumping system comprising fluid conduit means with heat transfer characteristics having inlet means at one end and outlet means at the opposite end, means for introducing liquified gas from said container into said inlet means of said conduit means for travel therethrough, a housing defining an elongated air passage enclosing said conduit means along its length and being open to the atmosphere at an inlet end and an outlet end, said housing being contoured to fit snugly against the side of said tank with said outlet end of said passage disposed adjacent the bottom of the tank and said inlet end disposed upwardly along the side of the tank, said air passage having a relatively small cross-sectional area, the length and cross-sectional dimensions of said passage being so related that the introduction of said liquified gas into said conduit means from said inlet means induces substantial convectional flow of atmospheric air through said passage from said inlet end to said outlet end, sufficient atmospheric air being induced to flow through said passage in heat transfer contact with said conduit means so that sufi'icient liquified gas is vaporized in said conduit means to produce gas under substantial pressure, said outlet means of said conduit means being connected to said container whereby gas under pressure is introduced to said container to force liquified gas out of said container.

2. In combination with a container for storing a liquified gas, a system for pumping said liquified gas from said container with energy derived solely from the natural environment of the system, said pumping system comprising: fluid conduit means including a plurality of fluid conduits having heat transfer characteristics and extending in serpentine fashion from inlet means at one end of said conduit means to outlet means at the opposite end, means for introducing liquified gas from said container into said inlet means for travel through said conduits, means defining an elongated air passage enclosing said conduits along their length and being open to the atmosphere at an inlet end and an outlet end, said air passage having a relatively small cross sectional area, the length and cross sectional dimensions of said passage being so related that the introduction of said liquified gas into said conduits at said inlet means induces substantial convectional flow of atmospheric air through said passage from said inlet end to said outlet end, sufiicient atmospheric air being induced to flow through said passage in heat transfer contact with said conduit so that suflicient liquified gas is vaporized within said conduits to produce substantial gas under pressure, said outlet means of said conduit means being connected to said container whereby gas under pressure is introduced to said container to force liquified gas out of said container, each of said conduits being divided into a dehumidification section and a heat transfer section, each heat transfer section being disposed adjacent said outletend of said passage and each dehumidification section being disposed adjacent said inlet end of said passage, each dehumidification section comprising bare pipe meansfor removing moisture from the air Without causing suflicient buildup of frost to block air flow through said passage, each heat transfer section comprising pipe means having heat transfer fins mounted thereon for accelerating the vaporization of liquified gas in said conduits.

3. The combination of a container for storing a liquified gas and a system for pumping said liquified gas from said container with energy derived solely from the natural environment of the system wherein the container includes a horizontally disposed, generally cylindrical tank, said pumping system comprising a generally elongated housing secured to the side of said tank and having an air outlet end disposed adjacent the bottom of the tank and an air inlet end disposed upwardly along the side of the tank, said housing defining an arcuate air passage along the side of said tank from said air inlet end to'said air outlet end, the length of said air passage being substantially greater than the smallest of its cross-sectional dimensions, a series of fluid conduits having serpentine configurations extending through said passage from fluid inlet means adjacent said air outlet end to fluid outlet means adjacent said air inlet end, means for metering liquified gas from said container into said conduits through said fluid inlet means, the length and cross-sectional dimensions of said passage being so related that the introduction of said liquified gas intopsaid conduits through said inlet means induces a substantial flow of atmospheric air through said elongated air passage from said inlet end to said outlet end, said atmospheric air flowing through said passage in heat exchange contact with said conduits to vaporize said liquid gas within said conduits, and means for removing gas under pressure from said fluid outlet means and returning it to said tank to build up pressure Within said tank and force liquified gas out of said tank, each of said conduits being divided into a dehumidification section and a heat transfer section, each heat transfer section being disposed adjacent said outlet end of said passage and each dehumidification' section being disposed adjacent said inlet end of said passage, each dehumidification section comprising bare pipe means for removing moisture from the air without causing suflicient build up of frost to block air flow through said passage, each heat transfer section comprising pipe means having heat transfer fins mounted therein for accelerating the vaporization of liquified gas in said conduits.

References Cited by the Examiner UNITED STATES PATENTS 679,526 7/01 Carnay et al. 62-407 1,813,250 7/31 Moore 62-406 1,930,731 10/33 Thompson 62-53 2,823,521 2/58 Engeret al. 62-52 2,926, 506 3/60 Skaredofl 62-272 2,929,229 3/ Detweiler 62-256 2,958,204 11/60 Spaulding 62-52 3,012,408 12/61 Perkins et al. 62-52 3,058,317 10/62 Putman' 62-52 FOREIGN PATENTS 410,068 5/34 Great Britain.

EDWARD J. MICHAEL, Primary Examiner. ROBERT A. O'LEARY, Examiner.

Claims (1)

1. IN COMBINATION, A CONTAINER FOR STORING A LIQUIFIED GAS AND A SYSTEM FOR PUMPING SAID LIQUIDFIED FROM SAID CONTAINER WITH ENERGY DERIVED SOLELY FROM THE NATURAL ENVIRONMENT OF THE SYSTEM, SAID CONTAINER COMPRISING A HORIZONTALLY DISPOSED, GENERALLY CYLINDRICAL TANK, SAID PUMPING SYSTEM COMPRISING FLUID CONDUIT MEANS WITH HEAT TRANSFER CHARACTERISTICS HAVING INLET MEANS AT ONE END AND OUTLET MEANS AT THE OPPOSITE END, MEANS FOR INTRODUCING LIQUIFIED GAS FROM SAID CONTAINER INTO SAID INLET MEANS OF SAID CONDUIT MEANS FOR TRAVEL THERETHROUGH, A HOUSING DEFINING AN ELONGATED AIR PASSAGE ENCLOSING SAID CONDUIT MEANS ALONG ITS LENGTH AND BEING OPEN TO THE ATMOSPHERE AT AN INLET END AND AN OUTLET END, SAID HOUSING BEING CONTOURED TO FIT SNUGLY AGAINST THE SIDE OF SAID TANK WITH SAID OUTLET END OF SAID PASSAGE DISPOSED ADJACENT THE BOTTOM OF THE TANK AND SAID INLET END DISPOSED UPWARDLY ALONG THE SIDE OF THE TANK, SAID AIR PASSAGE HAVING A RELATIVELY SMALL CROSS-SECTIONAL AREA, THE LENGTH AND CROSS-SECTIONAL DIMENSIONS OF SAID PASSAGE BEING SO RELATED THAT THE INTRODUCTION OF SAID LIQUIFIED GAS INTO SAID CONDUIT MEANS FROM SAID INLET MEANS INDUCES SUBSTANTIAL CONVECTIONAL FLOW OF ATMOSPHERIC AIR THROUGH SAID PASSAGE FROM SAID INLET END TO SAID OUTLET END, SUFFICIENT ATMOSPHERIC AIR BEING INDUCED TO FLOW THROUGH SAID PASSAGE IN HEAT TRANSFER CONTACT WITH SAID CONDUIT MEANS SO THAT SUFFICIENT LIQUIFIED GAS IS VAPORIZED IN SAID CONDUIT MEANS TO PRODUCE GAS UNDER SUBSTANTIAL PRESSURE, SAID OUTLET MEANS OF SAID CONDUIT MEANS BEING CONNECTED TO SAID CONTAINER WHEREBY GAS UNDER PRESSURE IS INTRODUCED TO SAID CONTAINER TO FORCE LIQUIFIED GAS OUT OF SAID CONTAINER.

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