US3538718A

US3538718A - Refrigeration evaporator heat exchanger

Info

Publication number: US3538718A
Application number: US792892A
Authority: US
Inventors: Joseph T Karbosky
Original assignee: Phillips Petroleum Co
Current assignee: Phillips Petroleum Co
Priority date: 1968-12-26
Filing date: 1968-12-26
Publication date: 1970-11-10
Anticipated expiration: 1987-11-10

Description

Nov. 10, 1970 J. T. KARBOSKY REFRIGERATION EVAPORATOR HEAT EXCHANGER Filed Dec. 26, 1968 INVENTOR JOSEPH T. KARBOSKY ATTY'S United States Patent O 3,538,718 REFRIGERATION EVAPORATOR HEAT EXCHANGER Joseph T. Karbosky, Bartlesville, Okla., assignor to Phillips Petroleum Company, a corporation of Delaware Filed Dec. 26, 1968, Ser. No. 792,892 Int. Cl. F25b 41/04 US. Cl. 62-217 3 Claims ABSTRACT OF THE DISCLOSURE A heat exchanger having conducting passageways for a fluid to be cooled, has disposed therebetween and at substantially right angles thereto, openings comprising conducting passageways for a low-boiling liquid refrigerant. The heat exchanger is immersed to a predetermined depth in said liquid refrigerant; both said heat exchanger and refrigerant are housed within an evaporator chamber. The liquid refrigerant disposed about the heat exchanger passageways for the fluid material to be cooled vaporizes, forming a circulating, vapor-liquid mixture in the chamber which effects eflicient heat exchange with such fluid to be cooled.

BACKGROUND OF THE INVENTION This invention relates to cooling apparatus comprising a heat exchanger disposed within an evaporator chamber. More particularly, this invention relates to a novel heat exchanger-evaporator combination which enables a lowboiling refrigerant to efficiently pass through the heat exchanger as the result of a siphon-type circulation.

The use of low-boiling liquid refrigerants for cooling purposes is well known, as in the cooling of natural gas to transform the same to a liquefied state with an attendant desired reduction in volume. One method of prior art heat exchange is conducted in apparatus in which the heat transfer surfaces are immersed in the liquid refrigerant which is vaporized on the heat transfer surfaces, thereby forming a gaseous layer on such surfaces which reduces the efficiency of heat transfer. In addition, the refrigerant is normally cycled from the vicinity of the heat exchanger prior to re-entry therein for continued heat-exchange engagement with the natural gas or other fluid to be cooled which is moving through the heat exchanger. Such movement of the refrigerant exteriorly of the heat exchanger requires piping and insulation. Also, the refrigerant flow to and from the heat exchanger results in wasted heat-absorption values.

In accordance with this invention, the heat exchanger comprising adjacent passageways disposed at right angles to each other, is disposed within a refrigeration evaporator chamber. The liquid refrigerant passes through vertical refrigerant-conducting passageways of the heat exchanger, such vertical passageways being immersed in the refrigerant. Transverse passageways in the exchanger conduct fluids to be cooled in heat-exchange relationship with the refrigerant.

A portion of the liquid refrigerant vaporizes in the vertical passageways, thereby creating a mixture of vapor and liquid which is forced to rise through the refrigerant passageways due to the different refrigerant densities within the chamber. At the chamber top the vapor separates from the liquid refrigerant borne upwardly by the vapor, and the liquid drops to the chamber bottom in a siphontype circulation. The resulting refrigerant circulation provides for efficient heat transfer with the fluid to be cooled. A pressure regulator allows discharge of gaseous refrigerant to an auxiliary heat exchanger through which fluids to be cooled pass prior to entering the evaporator chamber.

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It is an object of this invention, therefore to provide a novel heat exchanger-refrigeration evaporator combination in which liquid refrigerant efficiently engages in heat exchange relation with fluids to be cooled by means of a heat exchanger disposed within the evaporator which permits a siphon-like circulation through the exchanger within the evaporator chamber confines.

It is another object of this invention to provide a novel heat exchanger-evaporator apparatus in which the refrigerant is circulated through a short circulating path within a refrigeration evaporator chamber, thereby eliminating the need for piping and insulation necessary with longer refrigerant flow paths normally employed.

It is a further object of this invention to provide efficient apparatus for effecting novel and efficient refrigerant flow, such apparatus being composed of a minimum number of parts which are of simple design and low cost.

The above and other objects of this invention will become more apparent from the following detailed description when read in the light of the accompanying drawing and appended claims.

DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic representation of a heat exchanger refrigeration evaporator provided by this invention;

FIG. 2 is a perspective view of one form of heat exchanger which may be employed in this invention; and

FIG. 3 is a perspective view of two heat exchangers in series which may be employed in the refrigeration evaporator of this invention.

DESCRIPTION OF THE INVENTION Referring now more particularly to FIG. 1, a fluid to be cooled such as natural gas passes through line 10', heat exchanger 12 and line 14 into refrigeration evaporator chamber 16. Disposed in chamber 16 is a heat exchanger 18, details of which are more apparent from FIG. 2. After passing through the heat exchanger 18, fluids to be cooled exit the evaporator chamber 16 through line 20.

It will be seen from FIG. 2 that the heat exchanger 18 is comprised of a central heat exchanger bundle 22 which is connected at opposed end portions to header portion 24 at which end of the heat exchanger the gases to be cooled enter from line 14, and header portion 26 which defines the end of the heat exchanger from which th gases to be cooled are discharged into exit conduit 20, The heat exchanger bundle 22 is composed of two basic elements, i.e., corrugated sheets and planar sheets of metal having good heat conductivity and resistance to the fluid materials flowing over the surfaces thereof. Corrugated sheets fabricated of thin sheet metal have been found to work to good advantage in many applications.

In the course of fabrication of the heat exchanger bundle 22 of FIG. 2, three vertically disposed corrugated sheets 28 having corrugations 280 are placed over a side planar sheet 34, the longitudinal axes of such corrugations extending in the horizontal plane in the normal position of use as illustrated. Placed between corrugated sheets 28 are corrugated sheets 32 in which the longitudinal axes of corrugations 32c extend at right angles to corrugations 28c. Planar sheets 34 straddle each of the corrugated sheets 28 and 32. It is the function of the corrugations 28c of the sheets 28 in conjunction with the planar sheets 34 straddling the same, to form closed passageways between the

opposed headers

24 and 26 of the heat exchanger 18 for conducting a fluid to be cooled.

The corrugations 32c vertically disposed in sheets 32 form passageways with sheets 34 which conduct a lowboiling liquid refrigerant in heat-exchange relationship with the fluid material to be cooled passing along the corrugations of the sheets 28 in the heat exchanger. It is intended that a low-boiling liquid refrigerant such as methane, ethylene or propane, enter the bottom of evaporator chamber 16 through line 38 (see FIG. 1) having disposed therein a motor-operated valve 40 which is controlled by level control 42 mounted on shell 44 defining the chamber 16.

It will be noted from FIG. 1 that the heat exchanger 18 is substantially centrally disposed within the chamber 16 so as to be spaced from all side wall and cealing portions of the shell 44. In the normal course of operation, a desired low-boiling liquid refrigerant enters the evaporation chamber 16 until a desired height is attained as determined by the level control 42. A fluid to be cooled then enters the heat exchanger 18 through the line 14 and passes from the header 24 into openings defined in part by the horizontally disposed corrugations 280 of the sheets 28. Since the level of the liquid refrigerant within the chamber 16 is at a desired level L, a portion of liquid refrigerant adjacent of the heat exchanger surfaces of the vertical plates 34 defining interfaces between the conducting passageways for the gases to be cooled and the liquid refrigerant will be vaporized because of the heat imparted thereto by the flow of gas or liquid to be cooled passing along the corrugated sheets 28. Because of the large amount of vapor generated on surface portions of the corrugations 320 of the sheets 32, the static pressure created by the head of the liquid refrigerant within the chamber 16 will force a mixture of liquid and vapor up the corrugations 320 of the sheets 32 to an upper portion of chamber 16. At the top of the chamber 16 any liquid carried by the rising vapor will separate and return to the pool of liquid refrigerant lying at the bottom of the chamber. A thermosiphon circulating phenomenon is thus effected resulting from the differences in refrigerant density within the chamber 16.

A pressure recorder controller 46 is in communication with a flow indicator 48 through line 50 and controls the opening in a motor-operated valve 52 through line 54. The controller 46 may, therefore, regulate the pressure within the evaporation chamber 16 by exhausting vaporized refrigerant through the valve 52 into auxiliary heat exchanger 12 through which the incoming fluid to be cooled passes prior to entering the evaporator chamber and the heat exchanger located therein. Vapors exiting heat exchanger 12 may be cycled to a compressor, and the resulting liquid recycled to chamber 16.

To assure the creation of desired, continuous refrigerant cycling in the vapor and liquid phase analogous to a siphon-type circulation, it is desired that the heat exchanger 18 which may rest on the chamber bottom, be located within the chamber 16 to provide ample room between the exterior of the heat exchanger and the adjacent side walls and ceiling portion of the refrigeration evaporator for the generated currents of refrigerant vapor and liquid to cycle. It is also necessary to locate the level of the liquid refrigerant at a distance from the top of the heat exchanger 18 which assures optimum efficiency. The liquid level should be such as to assure optimum refrigerant circulation and resulting heat trans fer. The created flow of gas and liquid refrigerant increases the heat transfer between the liquids or gases being cooled and the refrigerant generating the currents passing up along the corrugations 280 of the sheets 32 within the heat exchanger core, since the liquid component effects greater heat exchange than the gaseous fraction.

The heat exchanger bundle may be readily formed by clamping the aforedescribed corrugated sheets to the planar sheets thereof, applying a flux at the points of contact, placing the assembly in a furnace and brazing the contacting parts of the heat exchanger together.

Since the refrigerant cycle in the above described apparatus is completely within an evaporator chamber 16, considerable insulation and piping is eliminated, greatly reducing the expense of the apparatus described for performing a heat exchange process. The liquid refrigerant need not be piped to and from the evaporator chamber which may be appropriately insulated, inasmuch as the heat exchange process takes place in a single compact enclosure. The compact apparatus is able to take full advantage of a novel siphon-type circulation in which liquid refrigerant rises through the vertical passages disposed between passageways conducting the fluids to be cooled. The refrigerant vaporizes and generates currents rising to the top of the chamber whereat a portion of the vapor is eliminated from the system as determined by controller 46, and the liquid refrigerant returns once more to the pool in the bottom of the chamber.

Although the foregoing description has been specific with respect to the apparatus schematically illustrated in the drawing, it is appreciated that various modifications in apparatus may be employed in carrying out the steps described.

The specific configuration of the heat exchanger disposed within the evaporator chamber 16 is not of critical importance. It is essential, however, that the passageways of such exchanger which conduct fluids to be cooled be spaced to permit passage therebetween of a refrigerant liquid-gas current above described effecting a thermosiphon. Accordingly, the heat exchanger may comprise spaced convoluted coils partly immersed in the liquid refrigerant with the lengths of the coil convolutions being arranged generally horizontally, similarly to the plate corrugations 28c.

Selection of the particular refrigerant height for the specific heat exchanger employed which affords the optimum circulation and heat exchange is believed to be within the skill of the art in the light of the teaching above made.

Although FIG. 1 is illustrative of an assembly in which a single heat exchanger 18 is disposed within evaporator chamber 16, two or more exchangers may be employed in series to provide longer heat exchange relation with the fluid to be cooled with the refrigerant.

FIG. 3 illustrates two exchangers 22a and 22b in end-to-end relation supported on roller members 56. The rollers 56 enable the exchangers to slidably engage a planar supporting surface which may comprise the evaporator chamber bottom, as they expand within such chamber in which. disposed. Also, inlet pipe 14a passes fluid to be cooled into the distal terminal end of exchanger 22b whereafter such fluid exits the evaporator chamber through pipe 2% adjacent the point of entry of inlet pipe 14a.

Fluids to be cooled may also pass through two heat exchangers arranged in parallel in an evaporator chamber, and the apparatus described may be employed in a plurality of stages wherein a fluid to be cooled is subjected to increasingly lower temperatures. Thus, by way of example, natural gas at a pressure of 583 p.s.i.g., which has been cooled to a temperature of 143 F., passes through two heat exchangers in parallel, exiting the evaporator chamber in which such exchangers are disposed at a temperature of 172 F. and a pressure of 579 p.s.i.g. Liquid methane is used as the refrigerant. Each exchanger which is mounted on wheels to facilitate expansion, being about 17 /2 inches high, 27 /2 inches wide and 12 feet in length.

I claim:

1. In a refrigeration evaporator heat exchanger the combination comprising an evaporator chamber, a heat exchanger disposed in said chamber and spaced from the wall portions thereof, a pool of low-boiling liquid refrigerant disposed in the bottom of such chamber and immersing said heat exchanger; said heat exchanger having vertical passageways open at opposed ends, the lower ends of said passageways being immersed in said pool of refrigerant in the bottom of the evaporator chamber; said vertical passageways being in heat-exchange relationship with a plurality of transversely extending passageways in said heat exchanger adapted to conduct a fluid to be cooled; means for regulating the level of liquid refrigerant within such evaporator chamber to a predetermined distance from the top of said heat exchanger, means for controlling the gaseous pressure in said evaporator chamber, and an auxiliary heat exchanger through which such fluid to be cooled is passed prior to entering said evaporator chamber; said means for controlling the vapor pressure in said evaporator chamber also being adapted to regulate a flow of vaporized refrigerant to said auxiliary heat exchanger.

2. The refrigerator evaporator heat exchanger of claim 1 in which a plurality of heat exchangers are arranged in series in said evaporator chamber and are supported on the bottom of said evaporator chamber; said heat exchangers being readily movable over said bottom.

3. In a refrigeration evaporator heat exchanger, the combination comprising an enclosed evaporator chamber having a pool of low-boiling liquid refrigerant disposed in the bottom thereof; heat exchanger means partially immersed in said pool and having generally vertically extending refrigerant-conducting passageways opened at opposed ends, the lower ends of said passageways being in said pool of liquid refrigerant; passageways in said heat exchanger means transversely disposed to said generally vertically disposed passageways; the liquid level in said evaporator chamber being adequate to generate currents comprising a mixture of vaporized refrigerant and liquid refrigerant passing upwardly in said vertically extending passageways; means for controlling the gaseous pressure in said evaporator chamber; means for con trolling the level of the liquid pool in said evaporator chamber, and an auxiliary heat exchanger through which such fluid to be cooled is passed prior to entering said evaporator chamber and through which vaporized refrigerant passes from said evaporator chamber; said means for controlling the vapor pressure in said evaporator chamber also regulating the flow of vaporized refrigerant to said auxiliary heat exchanger from said evaporator chamber.

References Cited UNITED STATES PATENTS 2,107,053 2/1938 Coons 62-219 2,952,445 9/1960 Ladd 165166 3,289,757 12/1966 Rutledge 165-166 MEYER PERLIN, Primary Examiner U.S. Cl. X.R. 62-219; 165-166