US2897655A - System comprising a cold-gas refrigerator and a heat exchanger - Google Patents

Description

Aug. 4, 1959 Filed Jan. 12, 1955 c. o. JONKERS ET AL 2,897,655 SYSTEM COMPRISING A COLD-GAS REFRIGERATOR AND A HEAT EXCHANGER 2 Sheets-Sheet 1 INVENTORS coawauus OTTO JONKER JACOB WILLEM LAURENS KOHLER BYMQ'UAI AGEN C. O. JONKERS ET AL SYSTEM COMPRISING A COLD-GAS REFRIGERATOR AND A HEAT EXCHANGER 2 Sheets-Sheet 2 Filed Jan. 12. 1955 INVENTOR CORNELIUS O. JONKERS JACOB VI. L. KOHLER United SYSTEM COMPRISING A COLD-GAS REFRIGERA- TOR AND A HEATEXCHANGER Cornelius Otto Jonkers and Jacob Willem Laurens Kiihler, Emmasingel, Eindhoven, Netherlands, assignors, by memo assignments, to North American Philips Company, Inc, New York, N.Y., a corporation of Delaware The invention relates to a system comprising a cold-gas refrigerator and aheat exchanger, in which a medium containing a plurality of components is cooled, one or more components being separated from the medium. The

system according to the invention has the featurethat the heat exchanger is provided with a support which extends from the hot side of the heat exchanger, where the medium is supplied, to its cold side, where this medium is conducted away, the support having .a plurality of extensions, with which this. medium is in thermal contact, the heat of the extensions being conducted away for at least 25% by conduction via the support to its cold side. At some'of these extensions the component(s) to be separated out are precipitated, so that near these extensions the composition of the medium is modified and the temperature at which the component(s) can be separated out is reduced. By suitable choice of the component parts of the heat exchanger, viewed from the hot side thereof, the mean temperature of each of these extensions is at the most 20 C., preferably atthe most C. lower than that of the next following extension, while in normal operation of the heat exchanger the mean temperature of that extension atwhich the separation starts is not more than 20 (3., preferably notmore than 10 C. lower than the point of separation of these components of the medium as it is supplied to the extension. The systemdescribed above may, for example comprise a device for liquifying gases ora device for separating gaseous mixtures into fractions.

Such a heat exchanger has been suggested by the applicant; in this beat exchanger the impurities contained in the gaseous mixtures can be frozen out, If for example air is supplied to the heat exchanger, carbonic acid and water vapour will be separated out in the heat exchanger.

Thisheat exchanger fulfils its function satisfactorily as long as there is no excessive accumulation of ice, which mightobturate the heat exchanger.

It is therefore necessary to clean the heat exchanger from time to time, for example by heating it, so that the deposits are evaporated. To this end it will in general be necessary to stop the apparatus, so that the production by day is reduced. It is therefore of importance to render the productive operational time of the heat exchanger as long as possible.

According to a further aspect of the system according to the invention, the medium is, before it is cooled in the heat exchanger, pre-cooled in a further heat. exchanger by thermal contact with the cooling water of the cold-gas refrigerator.

With a cold-gas refrigerator heat must be conducted away to the surroundings; to this end use will often be made of cooling water.

The cooling water is supplied to the cooler of the apparatus so that water is available to be employed as cooling medium for the gaseous. mixture to becondensed, so=that part of the impurities, for example water vapour, contained in thegaseous mixture, for example air, can be separated out. Owing tothe pro-cooling of the gaseous mem- . Patented Aug. 4,1959

mixture by means of cooling water, a smaller quantity of cold must be conducted away .to the gaseous mixture by the cold-gas refrigerator.

The heat exchanger may be constructed in various ways. The support may comprise sections of different heat resistance each.

If a medium containing a pluralityof components having relatively diiferent separating ranges flows through the heat exchanger, the support is provided preferably by at least two groups of extensions, which serve to separate out one or more components, the.component(s) associated with one separating range being depositedon one group of extensions, the component(s) associated with the other separating range being deposited on the other group of extensions.

It will often be desirable to provide a third group of extensionsbetweenv the two groups of extensions, the third group serving mainly for cooling the medium.

The heat exchanger may furthermore be used frcquently as a freezer of the cold-gas refrigerator.

As an alternative, the support may give off heat to the boiling vessel of a rectifying column.

The invention will be described more fully with reference to one embodiment.

Figs. 1 and 2 show a cold-gas refrigerator for 'condensing a gaseous mixture.

Fig. 2 is a sectional view taken'on the line H of Fig. 1.

Figs. 3-and 4 show a gas separating. system, Fig. -4 being a sectional View taken on the line IVlV of Fig.3.

In the cold-gas refrigerator shown in Figs. 1 and 2a quantity of workingmedium, for examplehydrogen-performs a closed thermodynamic cycle. The workingspace of the machine comprises a freezing space 1, ducts 2'in a freezing section 3, a regenerator 4 and ducts 5 in a cooler 6 and a cooled space '7. The 'volume of the freezing space 1 is acted upon by meansof a displacerpiston 8, whereas the volume ofthecooled space 7 is acted upon both by the movements of the displacenpistomgand those of a piston 9. The displacer piston 8 and 'the piston 9 reciprocate to this end ina cylinder 10 with a substantially constant phase difference of for example By means of a connecting rodmechanism 11 thedisplacer piston is coupled with a crank of a crankshaft 1 12 and the piston 9 is coupled by means ofa-connecting rod system 13 with cranks of the same crankshaft '12. The cold-gas refrigerator is driven by "means of a motor, for example an electric motor 14, as is shown in Fig. 1. The freezer comprises two-sections, i.e. a section-3 lo cated inside the machine proper, with which the channels 2 are associated, and a section comprising a support having three sections in this embodiment, i.e; the sectioii 'ls, a section 16 and a section 17. The heat resistanceof these sections is different. The wall thickness of: the section 15 is materially larger than that of the section'io and the wall thickness ofthe latter is larger than "that of the section 17. The sections 16 and 17 are interconnected by means of a connecting. piece 18 having good thermal conductivity. The sections of the support are provided with extensions constructed in the fonn' of transverse partitions, i.e. the transverse'partitions:w, 2t) and 21, in which apertures are provided. As is evident from Fig. 2 these apertures are'in staggered positions in two successive extensions. 'The transverse partitions '19 with the apertures 22 o f-the section 15 and the transverse partitions 20 with the apertures .23 ofthe section. 16 extend to a wall 24 surrounding these sections and the transverse partitions Zi with the apertures 25, 'associated'with the section 17, extend to a Wall 26. The section l7is insulated from'the wall 24. The heat exchanger. is surrounded by wall 27 having heat insulating properties.

The gas to be cooled is supplied through apertures Y28 and flows through the apertures 25 of the transverse partitions 21 in upward direction; then it flows through an aperture 29 in the connecting piece 18 and through the apertures 22 and 23 in the transverse partitions 19 and 20 respectively and along vanes 30 of the freezer may be separated out and the transverse partitions 19 serve mainly for further cooling the medium.

Before the medium is supplied to the transverse partitions 21, it brushes past pipes 34, through which cooling water flows. This cooling water is supplied through a duct 35 and leaves the pipes 34 through the duct 36, which may communicate with the cooler 6. In the pipes 34 part of the impurities, for example water Vapour contained in the gaseous mixture is separated out. The relative temperature division of the transverse partitions 19, and 21 is such that the mean temperature diiference between the successive transverse partitions associated with one of these groups is not more than for example 10 C. The mean temperature of the extension where the separation starts is not more than 20 C., preferably not more than 10 0. lower than the point of separation of the component in the medium as this is supplied to the extensions. In accordance with the quantity of medium flowing through the heat exchanger, the separation will start at one of the transverse partitions located for example on the bottom side of the heat exchanger, where the medium enters. If after some time such a quantity of ice has been separated out in the heat exchanger that one or more of the spaces 32 or 33 is practically filled, it is desirable to stop the supply of medium to the heat exchanger and 7 no cold is any longer withdrawn from the heat exchanger. The solid carbonic acid in the spaces 33 will then volatilize, whereas the ice in the spaces 32 changes into Water and can be conducted away through a duct 37.

The system shown in the Figs. 3 and 4 comprises a rectification column 41. This column has a filler 42, which may for example be constituted by so-called Raschig rings. On the bottom side the column is provided with a boiling vessel 43, containing a quantity.

of the fraction having the highest boiling point in the liquid state. The boiling vessel 43 has a bottom 44, through which a tubular support 45 is taken. This support is secured thermally to the bottom of the boiling vessel. The support has wall portions 46, 47 and 48, having different thicknesses and both on the inner side and on the outer side the support is provided with extensions, for example vanes. On the inner side the extensions 49 are provided, having apertures 59 and 51, as is evident from Fig. 4. On the outer side the wall portion 46 of the support is provided with extensions 52, the wall portion 47 with extensions 53 and the wall portion 48 with extensions 54. All these extensions are provided with apertures 55, which are in staggered positions in successive extensions. The bottom of the boiling vessel is provided with vanes 56, arranged concentrically around the support. At the bottom the support 45 communicates with a duct 57 and on the top side the support extends in the boiling vessel to an extent such that it projects over the normal liquid level in this vessel. The portion of the support outside the boiling vessel is surrounded by an insulating jacket 58. This heat exchanger is provided with two supply ports 59, communicating with a duct 60 and with an outlet port 61, communicating with a duct 62, which duct communicates with the gas separation section of the column. A space 63 contains a cooling helix 64, which is traversed by water. This cooling-helix 64 has a supply duct 65 and an outlet duct 66. The duct 60 for the gaseous mixture comprises a pump 67 for the supply of the gaseous mixture. The space 63 has an outlet duct 68 for the condensate.

' On the top side the'column communicates through, a duct 69 with a cold-gas refrigerator 70, which communicates also through a duct 71 with the column. The cold-gas refrigerator has an outlet duct 72 for the liquid fraction having the lowest boiling point. The refrigerator is driven by an electric motor 73.

The system operates as follows. The medium to be separated into fractions, for example air having a high water content, is conducted with the aid of the pump 67 through the duct 60 to the cooling helix 64, in which the air is precooled and in which sometimes part of the Water vapour is precipitated from the air. Any quantity of water produced may be conducted away through the duct 68. Then the gaseous mixture is supplied to the spaces between the extensions 54, 53 and 52. Owing to the frequent contact of the medium with the extensions 54 the water vapour contained in the air is separated out in the form of ice on these extensions. The separation range extends to about 60 C. At the extensions 53 the temperature of the medium is reduced further, for example to C. and at the extensions 52 the air is cooled from 140 C. to for example 182 C. On the extensions 52 the carbonic acid is deposited. The extensions in the portions 54 and 52 are spaced apart comparatively widely and between the successive extensions of each group there is a comparatively small temperature difference of for example 8 C. This temperature difference is obtained by constructing the support from parts having a definite heat resistance.

The purified air, the temperature of which is reduced, is supplied through the duct 62 to the column 41. This column may for example be a so-called single column and operates under atmospheric or substantially atmospheric pressure. In the column the air is separated into fractions. In the boiling vessel 43 of the column is contained a substantially constant quantity of the liquid fraction having the highest boiling point, in this case oxygen. From the column liquid oxygen flows down and evaporates again in the boiling vessel; part of the vapour rises up in the column and a further part is conducted away through the tubular support 45 and the duct 57. In the support 45 the last-mentioned vaporous oxygen is in thermal contact with the air to be separated and rising up outside the support. In this embodiment about 70% of the heat withdrawn from the air will serve to heat this oxygen, whereas 30% is transferred through the support to the oxygen in the boiling vessel, which is thus evaporated.

At the top end of the column is located the fraction having the lowest boiling point in the vapour state, in this case the nitrogen. The vapour is conducted away through the duct 69 to the cold-gas refrigerator 70. By means of the cold produced by this cold-gas refrigerator the nitrogen is condensed and the condensate is supplied partly as a reflux to the column through the duct 71 and partly conducted away through the duct 72.

If after some time the heat exchanger is completely filled with deposited impurities, the ice may be removed in a simple manner by scraping after having removed the jacket 58. As an alternative, the ice may be removed by heating a heat exchanger, the water thus produced being conducted away through the duct 68.

What is claimed is:

1. A heat exchanger system for use with a watercooled cold gas refrigerator provided with an intercounected freezer, regenerator and cooler and a first heat exchanger in which a medium is cooled, comprising a second heat exchanger for precooling said medium by thermal contact with the cooling water of said cold-gas reg frigerator and separating out at least a part of said impurities of said medium, said second heat exchanger being located at the entrance to said first heat exchanger, said second heat exchanger comprising a plurality of pipes through which cooling Water flows, an inlet for said cooling water, and a conduit connecting said pipes to said cooler.

2. A heat exchanger system for use with a water-cooled cold gas refrigerator provided with an interconnected freezer, regenerator and cooler and a first heat exchanger in which a medium is cooled, comprising a second heat exchanger for precooling said medium by thermal contact with the cooling water of said cold-gas refrigerator and separating out at least a part of said impurities of said medium, said second heat exchanger being located at 15 2,690,060

the entrance to said first heat exchanger, said second heat exchanger comprising an helical pipe formation through which cooling water flows, inlet and outlet means for said helical pipe formation, and a conduit for conducting said medium over said helical pipe formation, said conduit having a pump for impelling said medium into said heat exchanger system.

References Cited in the file of this patent UNITED STATES PATENTS 1,534,794 Lundgaard Apr. 21, 1925 2,011,964 Ajam Aug. 20, 1935 2,608,387 Randall Aug. 26, 1952 Legatski Sept. 28, 1954

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