WO2001035036A1

WO2001035036A1 - Assembly of a gas cooler and refrigerant coolers, gas cooler, and use of an assembly or gas cooler of this nature, and method for the interstage cooling in multistage cooling systems

Info

Publication number: WO2001035036A1
Application number: PCT/NL2000/000716
Authority: WO
Inventors: Titus Maria Christiaan Bartholomeus
Original assignee: Grasso Products B.V.
Priority date: 1999-10-05
Filing date: 2000-10-05
Publication date: 2001-05-17
Also published as: EP1218675A1; ZA200202691B; NL1013212C2; AU1062901A

Abstract

An assembly (30) for cooling a gas using an evaporating first refrigerant, such as a film-evaporating refrigerant, which is brought into contact with the gas to be cooled. The assembly (30) comprises a gas cooler (19) of the gap type having a multiplicity of plate-like wall elements (30), which delimit the gaps (32, 34, 40, 43), and a refrigerant cooler (50) for cooling, in particular supercooling, a second refrigerant. The refrigerant cooler (50) comprises a channel or system of channels which is formed in at least one of the multiplicity of wall elements of the gas cooler of the gap type. One or more gaps may be subdivided, by means of a partition, into a first compartment (34) connected to the refrigerant inlet, which adjoins a plate element having a refrigerant-cooler channel or channel system, and a second compartment (32), connected to the gas inlet, which adjoins that side of the partition which faces away from the wall element.

Description

Assembly of a gas cooler and refrigerant cooler, gas cooler, and use of an assembly or gas cooler of this nature, and method for the interstage cooling in multistage cooling systems

According to a first aspect of the application, the invention relates to an assembly for cooling a gas using an evaporating first refrigerant, which is preferably to be brought into contact with the gas to be cooled and is preferably a film-evaporating first refrigerant, comprising: a gas cooler of the gap type, having a multiplicity of plate-like wall elements which are arranged parallel to one another, leaving open gaps which are delimited between them and, at opposite ends, are connected to in each case a different adjoining gap to form a series of gaps; and a refrigerant cooler for cooling, in particular supercooling, a second refrigerant. An assembly of this type is known. Referring to Claims 1 to 3, the applicant, Grasso Products B. V., has already been supplying assemblies of this nature for many years under the name "Interstage Cooling System B", cf. Fig. 2. This known interstage cooling system B is in fact a combination of a compressed-gas cooler (19), as has already been marketed by the applicant for a number of years under the name "Interstage Cooling System A", and a separate refrigerant cooler (18), in particular a liquid supercooler. The interstage cooling system A which has already been marketed for a number of years by the applicant is a gas cooler (19) of the gap type and essentially comprises a multiplicity of pipes which are fitted into one another with spaces between them and are arranged vertically. The spaces between adjacent pipes which have been fitted into one another form cylindrical gaps which, at their ends, are each connected to another adjoining gap in order to form a connected zigzag series of cylindrical gaps. At the start of the series of gaps, generally the outer gap, hot compressed gas originating from the so-called low-pressure side (1, Fig. 1) - referred to below as the "LP side" -, into which liquid refrigerant which has been branched off from the so-called high-pressure side (2) - referred to below as the "HP side" - has been injected is passed via an inlet into the series of gaps (19). The hot compressed gas and injected, evaporating refrigerant is passed through the series of gaps while the refrigerant evaporates, cooling the hot gas in the process, in order subsequently, at the end of the series, to be passed through to the HP side (2) via the outlet of the gas cooler (19). The injection of the refrigerant, which has been branched off from the HP side (2), into the hot gas originating from LP side (1) is controlled by a thermostatic expansion valve (11) which is actuated (13) by a temperature and/or pressure sensor (12) positioned on/in/at the outlet of the gas cooler (19). The separately arranged supercooler (18) is in fact nothing other than a conventional heat exchanger in which two separate channel systems, which are arranged so as to exchange heat, are accommodated. Expanded refrigerant which originates from the HP side (2) and has been branched off is passed through the first channel system, and the main stream of refrigerant, which remains after refrigerant has been branched off, is passed through the second channel system, the main stream of refrigerant then being supercooled further by further expansion of the stream of refrigerant which has been branched off. Then, after it has left the heat exchanger (18), the stream of refrigerant which has been branched off from the HP side (2) is used for injection into the stream (9) of hot gas originating from the LP side (1), in order then to be guided, together with the hot gas, through the above-described gas cooler (19) of the gap type with pipes which have been fitted into one another. Interstage cooling assemblies of this type having a gas cooler of the gap type and a separate liquid supercooler are known on a more general basis than simply those originating from the applicant, and are also supplied by other suppliers. A separate refrigerant cooler or liquid supercooler has the drawback that this cooler has to be fitted separately and/or supplied as a separate part, that it takes up relatively large amounts of space, that the joints and connections of such plate heat exchangers, which are often soldered, are relatively weak and are not able to successfully withstand vibrations. Perhaps the most significant drawback of a separate refrigerant cooler occurs specifically in the case of refrigerants which have a high heat of evaporation in combination with a low specific gravity/low relative density, in which case, after expansion, a high volumetric proportion of gas is formed, and therefore a very low volumetric proportion of liquid. One example of a refrigerant of this type is ammonia. With a refiigerant of this type, it is not possible at a technical level to distribute the remaining liquid refrigerant/liquid which is still to be evaporated over a heat exchanger with a plurality of parallel channels/pipes. The object of the present invention is to provide an improved assembly of the type described in the introduction, which improved assembly overcomes the above problems, at least some of these problems.

According to the invention, the above object is surprisingly achieved by the fact that refrigerant cooler comprises a channel or system of channels which is formed in at least one of the multiplicity of wall elements and is separated from the series of gaps. In other words, it has surprisingly proven possible to integrate the refrigerant cooler or refrigerant supercooler in the gas cooler by forming a channel or channel system in at least one of the walls delimiting the gaps, through which channel or channel system the refrigerant which is to be (super)cooled is passed in order for heat to be extracted from it. It is surprising that this is possible, since in gas coolers of the gap type the hot gas to be cooled, at temperatures of usually higher than 80°C and generally lower than 170°C, tends to heat the interior of the gas cooler, in particular its walls which delimit the gas, which therefore implies that the refrigerant which is to be cooled further and is being guided through at least one of the walls is in fact heated as a result of heat absorption instead of being cooled, as is the intention, by heat being extracted from it. The applicant has arrived at the insight that it is nevertheless possible to integrate a gas cooler and refrigerant supercooler to form a single unit.

According to an advantageous embodiment of the invention, this is possible as a result of the fact that the assembly comprises isolating means which, at least during operation, completely or partially isolate the at least one wall element provided with the channel or channel system from the gas stream which is to be cooled. According to the invention, isolating means of this nature can be produced by actuating the assembly, in particular the stream of first refrigerant, during operation in such a manner that the first refrigerant, along at least a section of the outside of the wall element containing the channel or channel system, forms a film of liquid, evaporating first refrigerant. Actuation of this nature is relatively easy to achieve in various ways for an average person skilled in the art. In this context, important factors include, inter alia: the velocity at which the gas which is to be cooled flows along the wall element, the temperature of the gas which is to be cooled; the physical properties of the gas; the amount of first refrigerant; the temperature of the first refrigerant; the physical properties of the first refrigerant; the physical properties of the wall element, etc. In the case of ammonia, even a film thickness of less 200 micrometers, generally even less than 100 micrometers, has proven to the applicant to provide a sufficient isolating action. Alternatively, the isolating means may also comprise means which are permanently present, such as, according to the one of the preferred embodiments a partition which divides the gap running along the wall element which contains the channel or channel system into a first compartment, which adjoins the wall element, and a second compartment, which adjoins that side of the partition which faces away from the wall element, the gas which is to be cooled in this case being passed through the second compartment, while the first compartment, on account of the space between the partition and the wall element, has an isolating action. According to another advantageous embodiment of the invention, the multiplicity of plate-like wall elements comprises a multiplicity of pipes which are fitted into one another with cylindrical spaces between them, fomiing the gaps, the said opposite ends being the ends of the cylindrical gaps.

If the multiplicity of plate-like wall elements comprises a multiplicity of pipes, according to the invention it is particularly advantageous if the channel is a channel which runs helically through the wall of the said at least one pipe, or if the channel system is a system of channels running helically through the wall of the said at least one pipe. In this way, it is possible to achieve the effect of the heat transfer coefficient from the second refrigerant, which is to be cooled, to the film of first refrigerant is substantially equal to, or at least of the same order of magnitude as, the heat transfer from the gas which is to be cooled to the film of first refπgerant.

In order to prevent the phenomenon which is known as sweating on the outside of the gas cooler of the gap type having pipes which are fitted into one another, according to the invention it is advantageous if the multiplicity of pipes which have been fitted together comprises an outer pipe and a multiplicity of inner pipes, and if the channel or channel system of the refrigerant cooler is formed in at least one of the multiplicity of inner pipes. In this arrangement, according to another advantageous embodiment the channel or channel system of the refrigerant cooler is formed in one or more of the outer pipes of the multiplicity of inner pipes, preferably in the outermost pipe of the multiplicity of inner pipes. This is advantageous inter alia in terms of structural engineering, since in this case the pipes for connecting the supply of second refrigerant which is to be cooled and discharging cooled second refrigerant are then in relative terms extremely easy to reach. The same also applies for the connections for the supply of first refrigerant and gas which is to be cooled, in which respect it can also be pointed out that, to cool the second refrigerant, it is advantageous for the latter to exchange heat with first refrigerant which is as cold as possible and that cooled gas mixed with first refrigerant can be discharged together via a single outlet which, in particular on account of the single central, common outlet, is easy to produce by extending the inner most pipe with respect to the pipes surrounding it.

According to a particularly preferred embodiment of the invention, which has in part already been mentioned above, the isolating means comprise a partition which is formed on one side and/or the other side of the at least one wall element in which the channel or channel system of the refrigerant cooler is formed, the said partition divides the said gap into a first compartment on that side of the partition which faces towards the said at least one wall element and a second compartment on that side of the partition which faces away from the said at least one wall element, the first compartment, as seen in the direction of flow, being connected on the upstream side to the refrigerant inlet for admitting the first refrigerant to the gas cooler, the second compartment, as seen in the direction of flow, on the upstream side being connected to the gas inlet for gas which is to be cooled, and the first and second compartments, as seen in the direction of flow through them, on the downstream side preferably being in communication with one another, in order to allow the refrigerant to come into contact with the gas. In this arrangement, the partition creates a separate space, which can be filled with gas and/or liquid from the second refrigerant, between the hot gas which is to be cooled and the wall element which contains the channel or channel system for second refrigerant. Depending on the rate at which the gas which is to be cooled is cooled, the length of the gap and other factors, the partition according to the invention may extend through part of a gap or an entire gap or even entirely or partially on both sides of the wall element through which second refrigerant flows. This is because as soon as the gas which is to be cooled has been cooled to a defined temperature, the heat of the gas, which may optionally be cooled still further, will be insufficient to heat the second refrigerant which is being guided through the corresponding wall element, at least to above its inlet temperature.

The partition therefore has the task of preventing direct contact between the in particular hot gas which is to be cooled and the wall element through which the second refrigerant which is to be cooled is guided, and therefore of isolating the hot gas from the second refrigerant which is to be cooled.

A second effect of the partition - which as such may also be considered entirely separately from the question of whether or not second refrigerant is flowing through the relevant wall element - is that subdividing the first gap, which adjoins the outer wall element, of the series of gaps into a first compartment, through which the first (or possibly only) refrigerant is guided, and a second compartment, which is adjacent (to the outermost wall element) and through which gas which is to be cooled is guided, prevents or at least counteracts sweating on the outside of the outer wall element, since this outer wall element will be heated by the warm/hot gas and is isolated from the first or only refrigerant used for cooling the gas by the space which results from the second compartment. With regard to a multiplicity of wall elements in the form of pipes which are fitted into one another, this represents the subject of Claims 10 and 11 of the present application, forming an independent second aspect of the application. However, as should be clear from the description of the anti-sweating action which has been outlined above, the subject of Claims 10 and 11 can be applied more broadly to gas coolers of the gap type in the broader sense, i.e. including, for example, gas coolers of the gap type composed of a plurality of parallel, flat plates.

So that the first refrigerant which is passed through the first compartment can exchange heat, via the partition, with the gas which is to be cooled and is passed through the second compartment, according to the invention it is advantageous if the partition is made from a thermally conductive material, such as a metal sheet.

According to both the first aspect and the second aspect of the present application, it is advantageous if the gaps of the series of gaps, as seen transversely to the gap direction and the direction of flow, each have a substantially identical passage area. The term substantially identical passage area is not intended to mean that the passage areas per se must be of identical size, but rather that a slight margin, for example a range of 10 to 20% variation in the passage area, is possible.

The present invention also relates to the use of an assembly according to the invention for cooling gaseous ammonia, in which the first refrigerant is ammonia, and preferably the second refrigerant is also ammonia. However, it is also possible to use other refrigerants, such as freon, in the assembly according to the invention. The invention also relates to the use of a gas cooler according to the invention for cooling gaseous ammonia, wherein the refrigerant is ammonia. However, other refrigerants, such as freon, can also be used in the gas cooler according to the invention. Furthermore, the invention also relates to the use of an assembly according to the invention in a multistage cooling installation for cooling gas originating from the low-pressure side by the refrigerant, which originates from the high-pressure side and has been branched off, being injected into the said gas and for the main stream of refrigerant originating from the high-pressure side to be supercooled by means of the refrigerant which has been branched off from the high-pressure side.

Furthermore, the invention also relates to the use of a gas cooler according to the invention in a multistage cooling installation for cooling gas originating from the low-pressure side by refrigerant originating from the high-pressure side being injected into it. Furthermore, according to the first aspect of the application, the invention also relates to a method for interstage cooling of gas originating from a low-pressure side and, cooling, preferably supercooling, liquid, or at least partially liquid, refrigerant originating from a high-pressure side, in a multistage cooling device, the refrigerant emanating from the high-pressure side being divided into a branch stream and a main stream, the main stream being passed through a channel or channel system formed in a wall element, the gas to be cooled being passed along the wall element, the branch stream being subjected to an expansion step and then being brought into contact with the wall element in such a manner that, along at least a section of the outside of the wall element, it forms a liquid film which isolates the wall element from the gas which is to be cooled.

In the appended drawings, Fig. 1-3 show examples of two two-stage cooling devices as are known from the prior art. The combination of Fig. 1 with Fig. 2 has already been discussed, in particular in the introduction to the description. Fig. 1 to 3 will be briefly explained in more detail below, primarily by designation of the components.

Fig. 1 shows a diagrammatic arrangement of a two-stage cooling installation in the general sense. The direction of flow through the various lines is in each case indicated more specifically by an arrow symbol. The two-stage cooling device comprises a so-called low-pressure side 1, referred to below as the "LP side", a high-pressure side 2, referred to below as the "HP side", and an interstage cooling unit 3 arranged between them. The LP side includes the evaporator 4, which is used to extract heat from the final consumer, or release cold to the final consumer, a control valve 5 of the throttle type, which is connected upstream of the evaporator, also known as a throttle control valve, and a compressor 6, which is connected downstream of the evaporator 4. The HP side 2 comprises a condenser 7, which dissipates the heat which has been absorbed substantially by the evaporator 4 to the environment, and a compressor 8, which is connected upstream of the condenser. Interstage cooling of the hot, gaseous refrigerant originating from the LP side, from line part 9, takes place between the LP side 1 and HP side 2 as a result of refrigerant, which has been branched off from the substantially liquid refrigerant originating from the high-pressure side (from line part 10) and is passed through an expansion valve 11, preferably a thermostatic expansion valve 11 (which is controlled by the pressures or temperatures measured at the sensor 12 via signal line 13), being injected and by the mixture then being allowed to exchange heat in a gas cooler 14 of the gap type having pipes which have been fitted into one another (cf. Fig. 3). As a result of a heat exchanger 18 being incorporated between expansion valve 11 and gas cooler 19, it is possible, after part of the stream of refrigerant has been branched off, for the remaining main stream of refrigerant to be supercooled in a heat exchanger 12, i.e. for this remaining main stream to be cooled to below the saturation temperature as a result of this stream being brought into heat-exchanging contact with the expanded, branched-off stream of refrigerant (cf. Fig. 2).

The present invention will be explained in more detail below with reference to Fig 4 to 9, in which:

Fig. 4 diagrammatically depicts the outline circuit diagram of a two-stage cooling device as is substantially known from the prior art and is therefore substantially identical to Fig. 1 ;

Fig. 5 diagrammatically depicts an interstage cooling device according to the first aspect of the application for a multistage cooling device according to the invention; Fig. 6 diagrammatically depicts an interstage cooling device according to the second aspect of the application for a multistage cooling device according to the invention;

Fig. 7 diagrammatically depicts a longitudinal section through an assembly according to the invention as can be used in both the embodiment shown in Fig. 5 and in the embodiment shown in Fig. 6;

Fig. 8 shows detail Vffl - VIII from Fig. 7, and

Fig. 9 diagrammatically depicts a variant of an assembly according to the invention. In Fig. 4, the same reference numerals as in Fig. 1 are used for corresponding parts. The exception to this is that the interstage cooling device in Fig. 4 is denoted by 20. The refrigerant line which enters the HP side from the interstage cooling device 20 is denoted by 15, the refrigerant line which enters the LP side from the interstage cooling device 20 is denoted by 14, the refrigerant line which enters the interstage cooling device 20 from the LP side is denoted by 9, and the line which enters the interstage cooling device 20 from the HP side is denoted by 10.

According to the invention, the interstage cooling device 20 may be configured with a refrigerant cooler or liquid supercooler (cf. Fig. 5) or without a refrigerant cooler or liquid supercooler (cf. Fig. 6). In both the interstage cooling device 20 shown in Fig. 5 and the interstage cooling device 20 shown in Fig. 6, it is possible to use the assembly 30 according to the invention which is illustrated in more detail in Fig. 7 and substantially forms an integrated gas cooler/refrigerant cooler or gas cooler/liquid supercooler. The essential difference between the embodiment shown in Fig. 5 and that shown in Fig 6 is that in the embodiment shown in Fig. 6 the line parts 26 and 27 (Fig. 5) have, as it were, been short-circuited without being connected to the assembly 30. It should therefore be clear that in the embodiment shown in Fig. 5 the helical channel 50 formed in the wall element 36 can be substantially dispensed with. In practice, for reasons of efficiency, it may be preferable, for the embodiment shown in both Fig. 5 and Fig. 6, to use one uniform assembly, for example the assembly 30 having a channel 50 formed through a wall element 30, and therefore for the inlet 26 and outlet 27 for the said channel 50 to be left unused in the embodiment shown in Fig. 6. Fig. 7 and 8 show an integrated gas cooler/refrigerant cooler assembly 30 according to the invention. The assembly 30 is composed of four pipes 44,

42, 36, 47 which have been fitted into one another, pipe 36, as will be explained in more detail below, being composed of the components 37 and 38. If the partition 33 which is to be described below is also regarded as a pipe, this constitutes a fifth pipe. The outer pipe 46 forms the outer shell, the external surface 47 of which is in contact with the environment. The inner pipes, namely pipe 36, pipe 42 and pipe 44 in succession, are accommodated inside the outer shell 46. A space is left open between the outer shell and each of these pipes in order to form successive cylindrical gaps 32/34, 40 and 43. The pipes 46, 36, 42 and 44 form plate-like wall elements which delimit the gaps 32/34, 40 and 43. At opposite ends 39 and 41, the gaps 32/34, 40 and 43 are each connected to their adjoining gap, to form a series of interconnected gaps. The gap 32/34 is subdivided by a cylindrical partition 33 into a first compartment 34, which adjoins pipe 36, and a second compartment 32, which adjoins the outer shell 46. The gas which is to be cooled can be passed into gap 32 via inlet 9 and the cylindrical distribution chamber 31. This gas which is to be cooled will then flow through the gap 32 to the end 39 (on the left in Fig. 7), in order, at the end 39 or space 39, to be, as it were, diverted through 180° and flow into gap 40, to flow through gap 40 towards the end 41 or space 41 (on the right on Fig. 7), will be diverted in space 41 through 180°, as it were, in order to flow into gap 43 and, via gap 43, to flow towards the end 51 or space 51 which lies opposite end 42, where it flows out into space 51 in order, once again, to be diverted through 180° and, via the interior 45 of pipe 44, to flow to outlet 15, where it leaves the assembly 30.

First refrigerant 22 can be supplied to the assembly via inlet 22 in order to cool the gas which is to be passed into the assembly via inlet 9. The first refrigerant 22 will enter the cylindrical distribution chamber 52 via inlet 22, in order to flow out of the cylindrical distribution chamber 52 into the first compartment 34 or gap 34, to flow through this gap 34 towards space 39 (on the left in Fig. 7), in order then to mix, in space 39, with the gas which is to be cooled and is passed via inlet 9 and gap 32 to space 39, and, together with this gas, to flow in succession via gap 40, space 41, gap

43, space 51, the interior 45 of pipe 44 to the outlet 15.

Ignoring the refrigerant cooler section for the time being, and referring in part to Fig. 6, in operation the assembly will operate as follows: Via line 21, the stream of first refrigerant is branched off from the refrigerant steam which originates from the HP side via line 10 and will generally be liquid, but may also contain a gaseous component. This branched-off first refrigerant stream is fed, via line 21, to an expansion device 25 in the form of a thermostatic expansion valve which, via signal line 23 and sensor 24, is controlled on the basis of the temperature and or pressure in the gas outlet 15 of the interstage cooling device 20. As is known per se from the prior art, the setting of the thermostatic expansion valve 25 will generally be adapted so as to maintain a specific, desired temperature as accurately as possible in line 15. The expanded first refrigerant stream originating from expansion device 25 is fed to the assembly 30 via line 22 (referred to as inlet 22 in Fig. 7). Gas which is to be cooled is fed to the assembly 30 via line 9 (referred to as inlet 9 in Fig. 7). The gas which is to be cooled will heat the outer shell 46 and also the cylindrical partition 33. From the first compartment 34, the partition 33 will be cooled by first refrigerant which is flowing through this first compartment 34, and therefore the first refrigerant will absorb heat originating from the hot gas and will cool the hot gas. To ensure that the cooling of the hot gas is carried out as quickly and efficiently as possible, the aim will be for the partition 33 to be coated with a film of first refrigerant on its side which faces toward the first compartment 34, which film may, for example be less than 100 micrometers if ammonia is used as the first refrigerant. To enable a film of this nature to be produced, it is particularly important for the flow velocity of the first refrigerant in compartment 34 to be sufficiently high, for example to be in the range from 10 to 30 m s. Subdividing gap 32/34 (which according to the prior art is not subdivided into compartments) into a first and second compartment by means of partition 33 prevents the first refrigerant, which is used to cool the gas which is to be cooled, from being able to come in direct contact with the outer shell 46, thus preventing or at least substantially counteracting sweating or condensation on the outer surface 47 of the outer shell 46. The first refrigerant stream and the stream of gas which is to be cooled will converge in space 39, will mix with one another and will be guided onwards via gap 40 and gap 43, with the mixture in the meantime exchanging yet more heat in order, in this way, for the gas to be cooled further. If the system is set up correctly, by space 51 the first refrigerant stream will have become completely gaseous.

Referring to Fig. 4, 5, 7 and 8, the main stream of refrigerant originating from the HP side which remains after the first refrigerant stream has been branched off, this main stream also being referred to as the second refrigerant stream, can be passed into the channel 50 via line 26 (Fig. 5) or inlet 26 (Fig. 7). Channel 50 is a helical channel which is formed in the wall of pipe 36 and, at the other end, opens out into an outlet 27, via which the cooled second refrigerant stream is discharged to the expansion valve 5 on the LP side. The helical channel 50 may be formed by milling a helical slot into a first pipe part 37 and then closing off this helical slot by sliding a close-fitting sleeve 38 over the first pipe part 37. The second refrigerant stream will release heat via pipe part 36 and sleeve 38 to the first refrigerant stream, which is colder in relative terms and is flowing through first compartment 34 or gap 34. In this way, the second refrigerant stream is cooled and, in practice, will even be supercooled. The partition 33, which divides gap 32/34 into a first compartment 34, through which the first refrigerant stream passes, and, in addition, a second compartment 32, through which the gas which is to be cooled passes, prevents the hot gas which is to be cooled from being able to come into direct contact with pipe 36, which would allow it to heat the second refrigerant stream instead of this second stream being cooled by the first refrigerant stream. If parameters such as the length of the gap 32/34 and the flow velocities of the gas which is to be cooled and of the first refrigerant stream are selected appropriately, the gas which is to be cooled will be cooled to a sufficient extent in space 39 to be able to be in direct contact with the pipe 36 in gap 40 without on balance heating the second refrigerant stream which is running through the helical channel 50. Although the medium mixture flowing through gap 40 will be able to partially heat the stream of second refrigerant, this heating will be less than the cooling effect via the other side of the pipe 36. With reference to the diagrammatic illustration shown in Fig. 9, it should be noted that according to the invention it is also possible for the separation between the gas stream which is to be cooled and the steam of first refrigerant to be continued further if the partition 62 is continued, via a bend section 67 and a second partition 68 so as to run along the other side of the pipe 36, indicated in Fig. 9 as wall element 64 with internal channel 65 for second refrigerant. As illustrated by dashed lines 71 in Fig. 9, if appropriate the partition may even be continued still further. Fig. 9 substantially represents a diagrammatic illustration of a gas cooler of the gap type composed of a multiplicity of flat plates or wall elements, namely outer plate 60, plate 64 which is provided with an internal channel 65, plate 70 and plate 73.

A gap 61/63, which is subdivided into a first compartment 63 and a second compartment 61 by partition 62, is formed between outer wall plate 60 and plate 64. A gap 66/69 which is partially divided into a first compartment 66 and a second compartment 69 by a partition 68 is formed between plate 64 and plate 70. A gap 72 is formed between plates 70 and 73. Arrow 76 indicates the supply of gas which is to be cooled, arrow 77 indicates the supply of the first refrigerant stream, and arrow 78 indicates the discharge of cooled gas. The supply and discharge for the second refrigerant stream, which open out into internal channel 65, are not shown.

If the first refrigerant, the second refrigerant and the gas to be cooled are ammonia, however, it will be preferable for the assembly of pipes which have been fitted into one another which is illustrated in Fig. 7 to be arranged in horizontal or lying position. This is because the length of the assembly of pipes can be relatively long. If the gas to be cooled, the first refrigerant and the second refrigerant are ammonia, the following indicative values may be mentioned for the gaps: the passage area of the gaps may be up to approx. 10000 mm , with the following

9 7 values being mentioned by way of example: 650 mm , 1200 mm , 2200 mm , 3000 mm², 4700 mm² and 8000 mm². It will be attempted, in an assembly, to keep the passage areas of the gaps substantially equal to one another.

For the gap thicknesses, it is possible to consider thicknesses ranging from 1 mm or less up to 25 mm, or possibly even above this, the following values being mentioned as examples of the gap thicknesses: 2,3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18 mm, as well as values between those listed. If the assembly according to the invention comprises a multiplicity of pipes which have been fitted into one another and a substantially constant value is desired for the passage area of the gaps of a single assembly, the gap thickness will increase from gap to gap from the outside inwards in the radial direction.

Claims

1. Assembly for cooling a gas using an evaporating first refrigerant, which is preferably to be brought into contact with the gas to be cooled and is preferably a film- evaporating first refrigerant, comprising: a gas cooler of the gap type, having a multiplicity of plate-like wall elements which are arranged parallel to one another, leaving open gaps which are delimited between them and, at opposite ends, are connected to in each case a different adjoining gap to form a series of gaps; and - a refrigerant cooler for cooling, in particular supercooling, a second refrigerant, characterized in that the refrigerant cooler comprises a channel or system of channels which is formed in at least one of the multiplicity of wall elements and is separated from the series of gaps.

2. Assembly according to Claim 1, characterized in that the assembly comprises isolating means which, at least during operation, completely or partially isolate the at least one wall element provided with the channel or channel system from the gas stream which is to be cooled.

3. Assembly according to Claim 1 or 2, characterized in that the multiplicity of plate-like wall elements comprises a multiplicity of pipes which are fitted into one another with cylindrical spaces between them, forming the gaps, the said opposite ends being the ends of the cylindrical gaps.

4. Assembly, according to Claim 3, characterized in that the channel is a channel which runs helically through the wall of the said at least one pipe, or the channel system is a system of channels running helically through the wall of the said at least one pipe.

5. Assembly according to Claim 3 or 4, characterized in that the multiplicity of pipes which have been fitted together comprises an outer pipe and a multiplicity of inner pipes, and in that the channel or channel system of the refrigerant cooler is formed in at least one of the multiplicity of inner pipes.

6. Assembly according to Claim 5, characterized in that the channel or channel system of the refrigerant cooler is formed in one or more of the outer pipes of the multiplicity of inner pipes, preferably in the outermost pipe of the multiplicity of inner pipes.

7. Assembly according to one of the preceding claims, characterized in that the isolating means comprise a partition which is formed on one side and/or the other side of the at least one wall element in which the channel or channel system of the refrigerant cooler is formed, the said partition dividing the said gap into a first compartment on that side of the partition which faces towards the said at least one wall element and a second compartment on that side of the partition which faces away from the said at least one wall element, - the first compartment, as seen in the direction of flow, being connected on the upstream side to the refrigerant inlet for admitting the first refrigerant to the gas cooler, the second compartment, as seen in the direction of flow, on the upstream side being connected to the gas inlet for gas which is to be cooled, and the first and second compartments, as seen in the direction of flow through them, on the downstream side preferably being in communication with one another, in order to allow the refrigerant to come into contact with the gas.

8. Assembly according to Claim 7, characterized in that the partition is made from a thermally conductive material, such as a metal sheet.

9. Assembly according to one of the preceding claims, characterized in that the gaps of the series of gaps, as seen transversely to the gap direction and the direction of flow, each have a substantially identical passage area.

10. Gas cooler for cooling a gas using an evaporating refrigerant which is preferably to be brought into contact with the gas to be cooled and is preferably a film- evaporating refrigerant, the gas cooler being of the type which has a multiplicity of pipes which are fitted into one another leaving open cylindrical gaps which, at their ends, are connected to form a series of interconnected gaps, characterized in that the gap between the outer pipe and the pipe which is next to the outer pipe is subdivided, by a cylindrical partition, into an outer compartment, which adjoins the outer pipe, and an inner compartment, which adjoins the inner pipe, the outer compartment being connected on the upstream side, as seen in the direction of flow, to the gas inlet for gas which is to be cooled, and the inner compartment being connected on the upstream side, as seen in the direction of flow, to the refrigerant inlet, and the inner and outer compartments merging on the downstream side, as seen in the direction of flow, in order to allow the refrigerant to come into contact with the gas.

11. Gas cooler according to Claim 10, characterized in that the gaps of the series of gaps, as seen transversely to the gap direction and the direction of flow, each have a substantially identical passage area.

12. Use of an assembly according to one of Claims 1-9 for cooling gaseous ammonia, wherein the first refrigerant is ammonia.

13. Use according to Claim 12, wherein the second refrigerant is ammonia.

14. Use of a gas cooler according to Claim 10 or 11 for cooling gaseous ammonia, wherein the refrigerant is ammonia.

15. Use of an assembly according to one of Claims 1-9 in a multistage cooling installation for cooling gas originating from the low-pressure side by the refrigerant, which originates from the high-pressure side and has been branched off, being injected into the said gas and by the main stream of refrigerant originating from the high- pressure side being supercooled by means of the refrigerant which has been branched off from the high-pressure side.

16. Use of a gas cooler according to one of Claims 10-11 in a multistage cooling installation for cooling gas originating from the low-pressure side by refrigerant originating from the high-pressure side being injected into it.

17. Method for, on the one hand, interstage cooling of gas originating from a low-pressure side and, on the other hand cooling, preferably supercooling, a liquid, or at least partially liquid, refrigerant originating from a high-pressure side, in a multistage cooling device, the refrigerant emanating from the high-pressure side being divided into a branch stream and a main stream, the main stream being passed through a channel or channel system formed in a wall element, - the gas to be cooled being passed along the wall element, the branch stream being subjected to an expansion step and then being brought into contact with the wall element in such a manner that, along at least a section of the outside of the wall element, it forms a liquid film of refrigerant which isolates the wall element from the gas which is to be cooled.

18. Cooling device provided with an assembly according to one of Claims 1 - 9 or provided with a gas cooler according to one of Claims 10 - 11, comprising as refrigerant ammonia NH₃, or possibly freon.