NL1023356C2 - Separation apparatus for removing drops of liquid from e.g. gaseous coolant, comprises liquid separator and coalescence device - Google Patents

Abstract

The apparatus (10) comprises a liquid separator (12) with an inlet for the two-phase mixture and a coalescence device (15) for the drops of liquid in the mixture. An apparatus for separating drops of liquid (e.g. oil) from a two-phase liquid/gas mixture (e.g. a mixture of gaseous coolant and liquid particles) (1) comprises a liquid separator with an inlet for the mixture and a coalescence device for the drops in the mixture. The coalescence device has an inlet for the mixture which is connected to the separator inlet, as well as having an outlet for the mixture. Independent claims are also included for the following: Use of a crack- type gas cooler as a coalescer in an oil separator used to separate oil from a coolant, the gas cooler being located upstream from the oil separator; and Use of the Coanda effect for coalescing drops of oil present in a stream of coolant on a surface (2, 3).

Description

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An assembly for separating liquid portions from a two-phase mixture comprising gas and liquid.

The present invention relates to an assembly for separating liquid particles, such as oil, from a liquid and gas comprising two-phase mixture, such as mixture of a gaseous refrigerant and liquid particles.

In cooling installations, it is common for a refrigerant to be compressed in the cooling cycle by means of a compressor. Oil is added to the compressor for lubricating the compressor. To ensure proper lubrication, the lubricating oil is administered in an excess. In the case of a piston compressor, that lubricating oil is also applied to the cylinders. The excess of lubricating oil disappears from the compressor in liquid and vapor form with the compressed gas, called compressed gas. The stream discharged from the compressor is therefore a two-phase mixture of gaseous refrigerant with liquid oil particles. These 15 oil particles can vary in size from very small (many times smaller than 70 µm, for example 5 μτη or much smaller) to large (200-1000 μτη) and even very large (larger than 1000 μχα to many times larger than 1000 μχα ). Since lubricating oil seriously contaminates the heat exchangers in the cooling installation, it is important to capture this lubricating oil. This is usually done by including a separator in the cooling cycle 20 after the compressor. A separator is often used as a gravity separator, which essentially consists of a vessel that is dimensioned such that the gas velocity therein is so low that most drops fall out of the gas stream to be collected in an oil bath at the bottom of the vessel. Such a gravity separator is capable of separating droplets with a size from 70 to 100 µm from the gas stream. The oil thus separated can then optionally be returned to the compressor. Smaller liquid particles pass through the separator. The new generations of highly loaded compressors, however, produce such small drops, in particular much smaller than 70 µm, as a result of a high speed that a conventional gravity separator is no longer sufficient. This problem has not yet been properly resolved.

The present invention has for its main object to provide an assembly for separating liquid from a two-phase mixture, with which also liquid particles with very small droplet size can be separated. The present invention has for its particular object to provide such an assembly with which liquid particles, such as oil particles, can be separated from the two-phase mixture comprising a refrigerant.

Said main object is achieved according to the invention by providing an assembly for separating liquid, such as oil, from a two-phase mixture, such as a two-phase mixture comprising a refrigerant, wherein the assembly comprises: a liquid separator with a separator inlet for the two-phase mixture; and • coalescence device for coalescerra of liquid particles contained in the two-phase mixture; Wherein the coalescence device comprises a coalescer inlet for the two-phase mixture and a coalescer outlet for the two-phase mixture, and wherein the coalescer inlet is connected to the separator inlet.

As previously stated, the liquid particles in the two-phase mixture according to the invention can vary in size from very small (≤ 5 μπι) to large (200-15,000 / an) or even very large (»1000 / tm).

With the assembly according to the present invention, liquid particles can be separated from this entire range of sizes. Compared to the state of the art, the progress in the assembly is in particular that the particles smaller than 70 μπι or even much smaller than 70 μs can be properly separated. In this respect, the two-phase mixture according to the invention can be seen as an aerosol-like mixture. After all, the invention in particular also makes it possible to separate the small liquid particles. The term aerosol-like is understood to mean in particular gas-containing liquid particles smaller than approximately 120 μ ,η, while larger liquid particles may very well also be present, and in certain applications will also be present.

By passing the two-phase mixture prior to the liquid separator through the coalescence device for coalescerra of liquid particles contained in the two-phase mixture, it is achieved that the very fine liquid particles, which are of a size normally not allowed to separate by a liquid separator -30 first coalescerra to larger liquid particles or possibly even a liquid film, after which these larger liquid particles can be easily separated in the liquid separator.

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According to an advantageous embodiment of the invention, the coalescence device is adapted to cause liquid parts to coalescence against a surface by means of a coanda effect. It is thus possible to have the very fine liquid particles in the two-phase mixture stream, without subjecting the two-phase mixture stream to, for example, filters 5 - which in practice can handle temperatures of up to only 120 ° C - into larger particles on a plane along which the two-phase mixture stream is conducted. is going to be. According to the invention, the larger particles formed on the surface, or optionally the liquid film formed thereon, can then both be directly captured and again be entrained by the two-phase mixture stream to be subsequently separated as larger particles in the liquid separator.

According to a further embodiment, the assembly according to the invention further comprises a compressor with a compressor inlet for two-phase mixture to be compressed, in particular refrigerant comprising two-phase mixture, and a compressor outlet for compressed two-phase mixture, wherein the IS compressor outlet is connected to the coalescer inlet. The coalescence device is thus provided immediately after the compressor, so that it is possible to treat lubricant particles entrained in the compressor by the two-phase mixture by means of the coalescence device. It should be noted, moreover, that in the ideal situation with a refrigerant installation, no contaminated refrigerant, but pure refrigerant, will be supplied to the compressor. However, this refrigerant can be in a two-phase mixture state.

According to a further embodiment of the invention, the coalescence device comprises at least one key-shaped channel via which key-shaped channel the coalescer inlet is connected to the coalescer outlet. By making use of the slit-shaped channel it is, inter alia, possible to use both boundary surfaces of the slit-shaped channel for a coanda effect. A slit-shaped channel moreover allows a compact structure with a relatively large boundary surface of the through-flowed channels.

In order to increase the contact surface along flow-through channels in a relatively compact construction, it is advantageous according to the invention if the coalescence device comprises a plurality of plate-like wall elements which, while releasing therebetween, have opposite adjoining ends with a different adjacent gap. chain of those slit-shaped channels are arranged parallel to each other. From a technical point of view, it is practical here if the plurality of plate-like wall elements and plurality of pipes are inserted into one another, forming the spit-shaped channels, into the cylindrical gaps, and when those opposite ends are the end ends of the cylindrical gaps.

According to an advantageous embodiment of the invention, the spit-shaped channels of the chain of slit-shaped channels, viewed transversely of the slit direction and flow-through direction, mutually have a substantially equal passage surface. The speed of the two-phase mixture in the slit-shaped channels can thus be kept approximately constant.

According to a further embodiment it is advantageous H according to the invention if liquid collecting means are provided at one or both of those opposite ends of the slit-shaped channels, which collecting means are preferably connected to discharge means for discharge of the collected liquid.

With vertically arranged slit-shaped channels, it is possible, for example, for the collecting means to consist of a collecting tray and for the discharge means to comprise a discharge pipe connected to the collecting vessel, which discharge pipe may optionally be provided with a valve for opening it at a desired moment for draining the collected liquid. It thus becomes possible, upon depositing relatively large quantities of liquid on the walls of the slit-shaped channels, to collect this liquid in the interim instead of carrying it along the entire channel system.

According to a further aspect, the present invention relates to the use of a slit type gas cooler as a coalescence device, hereinafter also called coalescer, in a lubricant separator for separating lubricant from refrigerant, the gas cooler being considered in the direction of flow of the refrigerant, I is included in the refrigerant flow for the lubricant separator.

In a still further aspect, the present invention relates to the use of an assembly according to the invention for separating lubricant, such as oil, from a gaseous refrigerant stream.

According to a still further aspect, the present invention relates to the use of a coanda effect for coalescing against a surface of lubricant particles, such as oil particles, present in a two-phase mixture-like refrigerant stream.

In the use according to the invention, the refrigerant comprises in particular ammonia or freon.

In the use according to the invention, the flow of refrigerant in particular has a speed greater than 5 m / s, such as 8 m / s or greater.

The present invention will be explained in more detail below with reference to the drawing. It shows:

Figure 1 shows a schematic representation of what is meant by coandefect according to the invention;

Figure 2 shows a schematic representation of an assembly according to the invention; and

Figure 3 shows a schematic representation of a coalescence device according to the invention.

FIG. 1 schematically illustrates the coanda effect utilized in accordance with an embodiment by the present invention. When a droplet laden gas stream 1 flows along a surface 2 and / or 3 at a high speed, such as a speed greater than 10 m / s, then that surface 2 will and / or 3 an underpressure is created which tends to attract droplets from the gas stream. These drops are then guided to the wall and strike on that wall. Struck on the wall and / or already prior to being struck on the wall in the underpressure zone along the wall, the drops will coalescence into larger drops. A film will then eventually form on the wall. The drops and any liquid films on the wall move along the wall at a considerably lower speed, for example a speed of approximately 10 mm / s. With respect to the gas flow rate, the movement of drops and / or film along the surface on which it is struck can therefore be designated as a kind of creep. The coanda effect described here occurs both when a gas stream is passed along a single surface - that is, when the upper surface 3 is completely absent, for example - and when the gas stream is passed between two surfaces.

FIG. 2 schematically shows an assembly 10 according to the invention. The assembly 10 shown in Fig. 2 is intended in particular for inclusion in a refrigerant circuit. According to this exemplary embodiment, the assembly 10 according to the invention comprises a compressor 11, an oil separator 12 and a coalescence device 15. At the compressor 11, refrigerant is drawn in via an inlet 14, which after being compressed is discharged from the compressor via outlet 16. Outlet 16 connects to inlet 17 of the coalescence device. Inlet 17 is also called coalescer inlet. The coalescence device 15 is provided with an outlet 18, 5 also referred to as a coalescer outlet, via which refrigerant carried through the coalescence device 15 drains out of the coalescence device. The coalescer outlet 18 connects to the oil separator inlet 19.

The compressor shown in Fig. 2 is shown very schematically. This I compressor is of the cylinder 32 / piston 30 type. An inlet valve 28 is provided on the inlet side of the cylinder 32. Inlet valve 28 is of the one-way type which passes only in the direction of the inlet 14 to the cylinder 32 and blocks the opposite direction. An outlet valve 29 is provided on the outlet side, which is also of the one-way type. Exhaust valve 29 is arranged such that it passes from the cylinder 32 to the compressor outlet 16 and blocks in the reverse direction. The piston 30 is moved up and down by means of a schematically indicated crank rod mechanism 31. The crank rod mechanism 31 is arranged in a schematically indicated chamber 34 in which optionally a bath of lubricating oil 27 is present. With compressors operating in particular at high speed, it is important that the piston 30 moving into the cylinder 32 is lubricated. To this end, lubricating oil is supplied to the piston 31.

This lubricating oil can come from the bath 27, but can also come from other sources. The supply of lubricating oil to the piston 30 occurs in particular with an excess. This supply of lubricating oil 30 can take place in many ways known from the prior art. For example, it is possible to provide a pipe system in the piston 30 with openings in the peripheral surface 35 of the piston 30.

As will be clear, it is almost impossible with such compressors 11 to completely prevent lubricant particles from falling into the supplied refrigerant 36. In Fig. 2 the lubricant particles, in particular oil particles, are schematically indicated by drops 33. A two-phase mixture of refrigerant and lubricant particles will thus be expelled from the compressor via the outlet 16.

The lubricant particles contained in this two-phase mixture 37 must be separated. According to the prior art, it is customary for this purpose to (directly) connect the compressor outlet 16 to an oil separator inlet 19 of a 7 oil separator 12. In the oil separator 12, the two-phase mixture is then successively passed through a demister 20 and a space 24, in which space 24 the drops drop out of the gas stream under the influence of gravity. In the demister, the drops are further enlarged so that they are in. space 24 easier 5. The droplets raining down from the gas stream are collected in a bath 22. From this bath 22 the collected liquid fluid, possibly with residual refrigerant, can then be discharged via line 26. Drain line 26 may optionally be returned to the compressor for recirculation of the lubricant. Partially lubricated two-phase mixture then leaves the oil separator via oil separator outlet 25 to precede the cold cycle.

According to the present invention, however, a coalescence device 15 is provided between the compressor outlet 16 and the oil separator inlet 19, an embodiment of which is shown in more detail in FIG. In the coalescence device 15, smaller lubricant particles - which cannot be separated from the gas stream in a conventional manner with demister and gravity - are brought to coalescence, so that larger particles of lubricant or even a lubricant film are formed. These larger particles or lubricant film can then be more easily separated later in the conventional oil separator. However, it is also very conceivable according to the invention that the conventional oil separator is completely eliminated and that the lubricant separation takes place directly in the coalescence device itself.

In Fig. 2, the coalescence device is depicted as being built into the (otherwise conventional) oil separator 12, however, it will be clear that the coalescence device may very well be positioned outside the conventional oil separator 12. The coalescence device according to the invention is in particular adapted to cause liquid parts to coalescence against a surface by means of a coanda effect.

Figure 3 shows in more detail an embodiment of the coalescence device 15 according to the invention. The coalescence device 15 according to the invention is constructed as a number of inserted tubes. The coalescer inlet 17 opens into the inner tube 41. The inner tube 41 ends at some axial distance above the lower end end partition 40. Around the inner tube 41 is a second tube 42 which connects with its lower end to the end end partition 40. Thus it is ensured that the medium flowing in through the inner tube 41 is at the bottom - such as with a curved arrow

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8 - the gap 43 is turned over. The second tube 42 terminates at some top axial distance from a partition 44. A gap 46 is formed on the partition 44 at the upper end of a third tube 45. A gap 46 is formed between the third tube 45 and the second tube 42. The space between the partition 44 and the upper end of the second tube 42 makes it possible for the medium, as indicated by a curved arrow, to be diverted into the gap 46. The third tube 45 ends again at the lower end at some axial distance from the lower end partition 40. Around the third tube 45 the outer tube 47 is radially spaced while leaving a gap 48. The axial distance between the lower end of the third tube 45 and the lower baffle 40 allows the medium to be led from the gap 46 to the gap 48. Slit 48 opens at its top into an outlet chamber 49 to which the coalescer outlet 18 connects.

On the inner surface of the inner tube 41 as well as on the outer and inner surfaces of the tubes 41,42,45 and 47, which deletes the gaps 43,46 and 48, under the influence of the coanda effect deposition of liquid particles, in the special lubricant particles. All this as described with reference to Fig. 1. The speed with which the gas flow is passed through the slits and the inner tube will generally be greater than 10 m / s. The speed at which the drops and / or any liquid film deposited on the walls of the tubes moves in the direction of flow of the gas is considerably slower, for example in the order of 10 mm / s. It is optionally possible to capture these drops and / or any liquid film stuck to the tube walls in the case of horizontal arrangement of the tubes at both ends of the spit-shaped channels or in the case of a vertical arrangement, as shown in Figs. the underside of the slit-shaped channels. An alternative, setup-independent method of collecting liquid particles can be realized with so-called crawl traps 53 (German “Krichfallen”). These are slots provided in the wall surfaces 41, 42, 45 and / or 47. The wall surfaces 41, 42, 45 and / or 47 will advantageously be provided internally with a drainage system, such as a hollow space 51, 52 or drainage channels. An example of crawl traps is shown in Figure 4, which shows a detail from Figure 3. As can be seen, the tube walls 42 and 45 here are double-walled with a space 51 and 52 between them through which the 9 particles (see dashed arrows) introduced via crawl traps 53 can be discharged. Depending on the degree of capture of liquid particles, the conventional separator can then possibly be dispensed with.

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Claims (17)

An assembly for separating liquid particles, such as oil particles, from liquid and gas comprising two-phase mixture, such as a mixture of gaseous refrigerant and liquid particles, wherein the assembly comprises: a liquid separator with a separator inlet for the two-phase mixture; and a coalescence device for coalescuing liquid particles contained in the two-phase mixture; Wherein the coalescence device comprises a coalescer inlet for the two-phase mixture and a coalescer outlet for the two-phase mixture, and wherein the coalescer inlet I is connected to the separator inlet. An assembly according to claim 1, wherein the coalescence device is adapted to cause liquid parts to coalescence against a surface by means of a coanda effect. 3. Assembly as claimed in claim 1 or 2, further comprising a compressor with an compressor inlet for compressed two-phase mixture, at least gas, in particular I refrigerant, and a compressor unit for compressed two-phase mixture, wherein the compressor inlet is connected to the coalescer inlet. 4. Assembly as claimed in any of the foregoing claims, wherein the coalescence device comprises at least one key-shaped channel via which slit-shaped channel the coalescer inlet is connected to the coalescer outlet. Assembly according to any one of the preceding claims, wherein the spit-shaped channel connecting to the I coalescer inlet runs opposite to the coalescer inlet I 6. Assembly as claimed in claim 4 or 5, wherein the coalescer outlet is transverse to the spit-shaped channel. Assembly as claimed in any of the claims 4-6, wherein the coalescence device comprises a plurality of plate-like wall elements which, while releasing therebetween I, are connected at opposite ends to each other with an adjacent slit until I have a chain of said slit-shaped channels, mutually connected I 30 are arranged in parallel. Assembly as claimed in claim 7, wherein the plurality of plate-like wall elements I comprise a plurality of pipes which are inserted into each other with cylindrical interspaces forming the slit-shaped channels, and wherein said opposite ends are the end ends of the cylindrical slits. 9. Assembly as claimed in claim 7 or 8, wherein the slit-shaped channels of the chain of key-shaped channels, viewed transversely of the slit direction and flow direction, mutually have a substantially equal passage surface. 10. Assembly as claimed in any of the claims 7-9, wherein liquid collecting means are provided at one or both of those opposite ends of the slit-shaped channels, which collecting means are preferably connected to discharge means for discharge of the collected liquid. Use of a slit type gas cooler as a coalescer in an oil separator for separating oil from refrigerant, wherein the gas cooler, viewed in the flow direction of the refrigerant, is included in the refrigerant flow for the oil separator. 12. Use of an assembly according to any of claims 1-10, for separating oil from a gaseous refrigerant stream. Use of a coanda effect to coalescence liquid-like oil particles present in a stream of refrigerant against a surface. Use according to claim 11 or claim 12 or claim 13, wherein the refrigerant comprises ammonia or freon. Use according to one or more of claims 11-14, wherein the flow of refrigerant has a speed greater than 5 m / s, such as 8 m / s or greater. A coalescence device as defined in a claim * claims 1-10. A coalescence device file for use in an assembly according to any one of claims 1-10. 25