US3117428A

US3117428A - Apparatus for cooling gaseous media

Info

Publication number: US3117428A
Application number: US152604A
Authority: US
Inventors: Hanny Jost
Original assignee: Sulzer AG
Current assignee: Sulzer AG
Priority date: 1961-08-15
Filing date: 1961-11-16
Publication date: 1964-01-14
Anticipated expiration: 1981-01-14
Also published as: CH388358A; GB979935A

Description

3 Sheets-Sheet l .1. HANNY APPARATUS FOR COOLING GASEOUS MEDIA Jan. 14, 1964 Filed Nov. 16, 1961 FIG. 1

Q L L E Ev TE; T J r fpa r A u QM m INVEFATOR JOST HANNY BY l' w lwsfpbu' ATTORNEYS I TH Jan. 14, 1964 J. HANNY 3,117,423

APPARATUS FOR COOLING GASEOUS MEDIA Filed Nov. 16, 1961 3 h s-Sh 2 INVEIETOR JOST HANNY ATTORNEYS Jan. 14, 1964 J. HANNY APPARATUS FOR COOLING GASEOUS MEDIA 3 Sheets-Sheet 3 NVE I TQR JOST HANNY ATTORNEYS A044, M W MJW Filed NOV. 16, 1961 United States Patent Ofifice idiiAZ Patented Jan. 14, 19 34 AFAPATUS FSR CQQLENG GASEQUS MEDKA Jest Hanny, Winterthur, witzerland, assignor to ulzer Freres, Societe Anonyme, Winterthur, Switzerland, :1

Swiss company Fiied Nov. 16, 1%1, Ser. No. 152,694 Claims priority, application Switzerland Aug. 15, 1961 9 Claims. (iii. 62-402) This invention pertains to a system for cooling gaseous media, in which system an expansion turbine which operates at low temperature and in which the gases are expanded with the performance of work, is coupled by means of a shaft supported in gaseous hearings to a turbo compressor which operates at a higher temperature. The invention relates more particularly to such an arrangement in which the gas, which performs a braking function in the turbo compressor, flows in a closed cycle separate from the cycle of the working substance in the turbine, the compressor gas being recirculated through a heat exchanger and through an adjustable throttling device, and in which moreover gas of the same composition is used in the turbine, in the compressor, and in the gaseous bearings.

Apparatus according to the invention, or plural sets of such apparatus, may be employed in the gas cycle of a rectifier, liquefier, or low temperature refrigerating plant employing air or other suitable gas. Such plural installations may be operated either in series or in parallel.

Upon the occurrence of pressure variations or pressure drops at the turbine, gas at relatively high temperature will flow out of the braking compressor through the gas bearings, which are also fed with high temperature gas, and thence into the turbine. This results in substantial heat losses into the refrigeration cycle. For their dissipation substantial energy must be expended. The heat streaming into the cold portion of the system and the volume of gas which carries it are, other things being equal, dependent upon the volume of the braking compressor system. It is therefore desirable to reduce this volume so far as possible.

On the other hand, the heat exchanger in the braking device, which serves for the abstraction of energy transmitted from the turbine to the compressor, must deliver a specified amount of heat to the cooling medium, which is usually water. It is therefore desired to promote heat transfer Within the braking part of the system, particularly in the heat exchanger. It is only in this way i.e. by improved heat transfer through the exchange surfaces, that with a given amount of heat to be disposed of and with a given temperature difference between the medium to be cooled and the cooling medium, these surfaces can be held small and thereby, other things again being equal, the volume of the braking installation be held down. Improved heat transfer can, as is known, he achieved by raising the streaming velocity of the gas in the braking installation, thereby reducing the streaming cross section.

Let the thermal diameter a' be defined for the entire braking installation as the quotient of the four-fold volume of the gas cycle of the braking installation divided by the total surface through which heat exchange is to take place. If in addition to an increased streaming velocity the thermal diameter d of the entire braking installation is made as small as possible, the result is a further improvement in heat transfer. In this fashion, for a given quantity of heat and a specified temperature drop, the surface necessary for heat exchange can be held smaller than that required with a higher streaming velocity and bigger thermal diameter d This means however that the volume of the complete braking cycle will be very small, first because of the increased pressure drop and the consequent increase in streaming velocity, and also in view of the small exchange surface required by the thus further increased heat transfer and lastly because of the decline with d of the ratio of volume to surface.

According to the invention, and in contrast to prior installations in which pressure drop has been so far as possible avoided in the heat exchanger, the pressure drop corresponding to the substantial part of the pressure change produced by the compressor occurs in the heat exchanger. The invention is therefore characterized by the fact that the braking part of the system is so constructed that-to the extent permitted by the regulating capacity of the throttling deviceof the pressure change produced in the compressor, at least as large a fraction is dissipated in the heat exchanger as in the throttling device.

In this connection it is to be noted that with various gases such as helium or hydrogen, throttling at high temperatures produces a rise rather than a fall in the gas temperature.

Preferably the heat exchanger may be provided in the raking part of the system in the form of a number of narrow, long streaming conduits of split-tube or ribcooler type. The term split-tube cooler is used to denote a cooler in which the medium passes in opposite directions through coaxial tubes. With such an installation it is desirable that the thermal diameter of the entire braking installation as above defined shall not exceed 10 A further embodiment of the invention is characterized by the fact that the braking part of the system is constructed as a self-contained closed unit in which the heat exchanger is built directly onto the compressor, the throttling device being axially movable and being arranged coaxially with the compressor and surrounded by the heat exchanger.

By means of the system of the invention the gas streaming in the braking apparatus is circulated at a high velocity in a closed path. This effects good heat transfer. In consequence there is required a relatively small transfer surface for abstraction of the energy developed in the turbine. In consequence the physical size of the braking device can be held small by comparison with similar systems of the prior art.

Further features of the invention will appear from the following description of two embodiments, to be taken in conjunction with the accompanying drawings in which:

FIG. 1 shows an axial section on the line 11 of FIG. 2 through a braking device according to the invention, together with the coupling thereof to an expansion turbine which is disposed in the cyclical path of the coolant in a refrigeration plant;

FIG. 2 is a section on the line 22 of FIG. 1;

FIG. 3 shows a modified embodiment of the invention on the same convention as that of FIG. 1; and

FIG. 4 shows a section on the line 44 of FIG. 3, at an enlarged scale.

Like reference characters identify corresponding elements of structure in the various figures.

Referring to FIG. 1, the cold gas flows through the input line 1 into the high pressure space 2 of the turbine 3 and leaves the turbine, after expansion, through a funnel-shaped difiuser 5 and conduit 4, the diifuser being fixed to the housing 6 of the turbine. The outlet channel of the turbine is formed by means of a guide piece 8 which is similarly fastened to the housing 6 and which leads to diffuser 5. The housing 6 in turn is fastened to an insulating plate 20 of the low temperature refrigerating apparatus (not shown), which is disposed in a vacuum.

The turbine 3 is coupled to the rotor Iii of the turbo compressor by means of the shaft 9. The low pressure inlet and high pressure outlet conduits 11 and 12 of the compressor are disposed in a compressor housing 13 fastened to the housing 6 of the turbine. An inner portion 13a of the housing 13 is fixed by welding to a cylinder 47. The separation between the cold and warm parts of the apparatus is indicated at the dot-and-dash line A, the cold portion being above this line. The shaft 9, which may be disposed either horizontally or vertically according to the makeup of the installation, is borne in a gas bearing including segments 14. This bearing is disposed in a hollow space 15 of the turbine housing 6. The space 15 is divided into two parts by means of an enveloping element 17, to define an inner space 18 which houses the segments 14 and the fixed parts 19' of the bearing. Gas for nourishment of the bearing is fed from a separate source such as a bottle (not shown) through a conduit 21 in the compressor housing 13 into the spam 18. From the space 18 it passes through distribution channels 22 and a pressure equalizing space 23 to the segments 14. After passing through the bearing, the gas flows via an annular space 24 and the conduit 25, and also through openings 26 in the part 27, into the space 15. From the space 15 it is led out of the apparatus through a conduit not shown.

Packings necessary to be provided between the various spaces and against the atmospheric exterior are indicated at 28.

The braking part of the apparatus is formed by the compressor 10 with its low pressure side 11 and its high pressure annular space 12, these elements being disposed in the compressor housing 13. It also comprises the heat exchanger 31 connected directly to the housing 13, and a throttling device 32. The gas compressed in the compressor 1% passes from the space 12 as indicated in FIGS. 1 and 3 by means of the arrows directly into the channels 33 of the cylindrical heat exchanger 31, all within the closed path of the braking medium. After cooling in the heat exchanger 31, the gas penetrates to an annular space 34 which is coupled to the low pressure side 11 of the compressor via a connection 35 which is adjustable by means of the throttling device 32. This device is disposed coaxially with the compressor 19 and may be adjusted by means of a hand wheel 36 operating on an adjusting device. On the other hand, it is possible to control the setting of the throttling device 32 automatically, for example as a function of the temperature in the cooling circuit. The device 32 has the function of making possible adjustment of the rotational speed or the turbine within specified limits. To this end it is made axially movable by means of a spindle 33 which moves in a central bore 39 of the exchanger 31. The device 32 is therefore disposed in an envelope 4%, likewise positioned within the bore 39.

From the annular space 12 of the compressor the gas in the braking cycle passes in the embodiment of FIGS. 1 and 2 into axially extending laminar channels 33 of the heat exchanger 31, having a semi-circular cross section in planes perpendicular to the system axis. The gas passes through these channels in parallel. These channels possess between their radially inner and outer side walls rib-shaped heat transfer sheets having the shape of narrow strips 42 similar in construction to plate-fin coolers. These strips have a short extension axially of the system, and axially successive strips may be staggered with respect to each other circumferentially of the system axis 1. From the channels 33 the gas penetrates into the lower annular space 43 and from the latter into similar conduits 33:: which are similarly traversed in parallel, but in the opposite axial direction (upward, in FIG. 2). From these the gas passes into the space 34 and thence through the device 32 into the inlet space 11 of the compressor 16. The channels 33 and 33a are separated by means of the cylinder 47.

Between the channels 33 and 33a there are disposed semi-circular intermediate laminar spaces 48 which are filled with cooling water. This water is led into the heat exchanger 31 through a connection 49, into the circular segment-shaped space 49a. This space is stepped as required by the varying length of the channels 33 imposed on them by the shape of the inner portion 13a of the compressor housing. It extends radially inward however, even though at reduced cross section, to the vicinity of the throttlng device 32. The water thus passes into the heat exchanger, traversing the intermediate spaces 48 circumferentially of the axis in parallel flow as indicated in FIG. 2 before it emerges from the exchanger 31 via the oppositely disposed segment-shaped space 56a and the connection 50, positioned diametrically opposite the conduit 49 at the lower end of the exchanger 31. In order to permit passage therethrough of the cooling water, the cylinder 47 is provided with openings (not shown) in the vicinity of the segment spaces 49:: and 5% which extend over the length of the conduits 33. The cooling medium and the gas to be cooled accordingly flow transversely of each other in the embodiment of FIGS. 1 and 2.

The embodiment of FIGS. 3 and 4 diifers from that of FIGS. 1 and 2 simply in the construction of the heat ex changer 31. In FIGS. 3 and 4 this exchanger takes the shape of a split-tube cooler. The compressor housing 13 and the exchanger 31 are here also made up of several parts. Consequently the boundaries of the annular space 12 are defined in part by an intermediate element 16 which encloses the compressor intake 11 and which includes bores 51 for exit of the gas from the annular space 12. In this embodiment the gas, after leaving the annular space 12, passes successively through the inner and outer coaxial spaces defined by the tubes 61 disposed concentrically in bores 63' of the heat exchanger block. In this flow, the gas passes from one pair of coaxial spaces to a serially succeedin pair via the

intermediate spaces

62 and 63. The annular junction space 62 is disposed in a further element 54 which houses the ends of the tubes 61. The element 54 is disposed between the intermediate piece 16 and the block 31 of the heat exchanger. In the heat exchanger the annular space 63 is separated from the space 34 by means of an annular insert 55.

The flow path for the cooling water is formed in a manner similar to that of the gas. The water passes through the bore 72 and the annular space 63 into the tubes 64 which lead to the bores 65 of the exchanger 31 coaxial therewith. Series-connected coaxial pairs each including the

coaxial passages

54 and 65 are connected together via annular spaces 69 in the base plate 67 and annular spaces 70 in the heat exchanger block. The ends of the tubes 64 are fixed in an element 71 disposed between the heat exchanger block and the base 67. The cooling water leaves the installation at the opening 66 in the base.

Viewed in cross section of the heat exchanger block, the bores 60' for the gas and 55 for the cooling medium are disposed in an alternating displaced relation to each other on the periphery of circles or" unlike radius. The heat exchanger is therefore of the counter flow type.

The invention is not limited to the details of the structure shown. The throttling device can be disposed at other positions within the circular flow path, for example either downstream of the diffuser 12a or in the bore 51 of the element 16.

By means of the construction of the braking element which has been described, and in which a substantial part of the pressure rise produced in the compressor is dissipated in the heat exchanger itself, the gas is caused to flow in a closed path at high velocity. By this means the heat transfer from the gas to the heat exchange surfaces is substantially increased. The good heat exchange thus achieved can be further improved if the thermal diamter d of the braking structure is held small. With a given heat exchange surface a diminution in d corresponds, by definiton, to a reduction in volume. Moreover as a result of the reduction in d there occurs an increase in the coefiicient of heat transfer which, other things being equal, makes possible further reduction in the size of the heat exchange surface which indeed is conditioned by the quantity of heat to be abstracted, by the heat transfer coefficient between the gas and the heat transfer surface, and by the temperature difference between them. In consequence there must occur a further decline in the volume necessary for the braking part. By means of the invention therefore it is possible to make the volume of the braking part small to a high order without encountering difficulties in dissipation of the energy liberated by the turbine. As initially indicated, this re duction in the volume of the braking part substantially decreases the heat losses in the turbine incident upon variations in pressure.

I claim:

1. Apparatus for cooling at gas comprising an expansion turbine through which said gas is expanded, said turbine having a shaft supported in a gaseous bearing, a turbo compressor coupled to said shaft, means defining for said compressor a closed path within which a gas is circulated by said compressor, a heat exchanger and an adjustable throttling device disposed in series in said path, said compressor and closed path being so proportioned that at least as much of the pressure difference between the inlet and outlet of said compressor is dissipated in said heat exchanger as in said throttling device.

2. Apparatus for cooling a gas comprising an expansion turbine through which said gas is expanded, said turbine having a shaft supported in a gaseous bearing, a turbo compressor coupled to said shaft, means defining for said compressor a closed path within which a gas is circulated by said compressor, the gas in said turbine, compressor and bearing being of substantially the same composition, a heat exchanger and an adjustable throttling device disposed in series in said path, said compressor and closed path being so proportioned that at least as much of the pressure difference between the inlet and 3 outlet of said compressor is dissipated in said heat exchanger as in said throttling device.

3. Apparatus according to claim 1 in which the ratio of four times the volume of said path expressed in cubic centimeters to the area of the heat exchange surface in said heat exchanger, expressed in square centimeters, does not exceed 1.0 cm.

4. Apparatus according to claim 2 in which the heat exchanger comprises a plurality of long, narrow, streaming channels through which flows the gas from the compressor.

5. Apparatus according to claim 1 wherein the heat exchanger takes the form of a ribbed cooler.

6. Apparatus according to claim 1 wherein the heat exchanger comprises a plurality of annular spaces coaxial in a common axis, means connecting radially alternate of said spaces in series for flow therethrough of gas from said compressor, and means to pass a cooling medium through the others of said spaces.

7. Apparatus according to claim 1 wherein the heat exchanger takes the form of a split tube cooler.

8. Apparatus according to claim 1 wherein the heat exchanger comprises a plurality of cylindrical arrays of blind bores in a heat exchange block, said arrays being coaxial in a common axis, a tube disposed in each of said bores, means to circulate gas from said compressor through the tubes and bores of radially alternate of said arrays in series, and means to circulate a cooling medium through the tubes and bores of the others of said arrays in series.

9. Apparatus according to claim 4 wherein the turbo compressor and heat exchanger constitute a self-contained unit with the heat exchanger arranged coaxially of the compressor and with the throttling device disposed within the heat exchanger.

References Cited in the tile of this patent UNITED STATES PATENTS 2,740,267 Bayard Apr. 3, 1956 FOREIGN FATENTS 870,091 Great Britain June 14, 1961

Claims

1. APPARATUS FOR COOLING A GAS COMPRISING AN EXPANSION TURBINE THROUGH WHICH SAID GAS IS EXPANDED, SAID TURBINE HAVING A SHAFT SUPPORTED IN A GASEIOUS BEARING, A TURBO COMPRESSOR COUPLED TO SAID SHAFT, MEANS DEFINING FOR SAID COMPRESSOR A CLOSED PATH WITHIN WHICH A GAS IS CIRCULATED BY SAID COMPRESSOR, A HEAT EXCHANGER AND AN AD-