WO2009012795A1

WO2009012795A1 - Manifold for a multi-compressor refrigeration system

Info

Publication number: WO2009012795A1
Application number: PCT/EP2007/006574
Authority: WO
Inventors: Klaus Koch
Original assignee: Carrier Corrporation
Priority date: 2007-07-24
Filing date: 2007-07-24
Publication date: 2009-01-29
Also published as: EP2183530A1

Abstract

A gas suction and oil refeeding manifold (2) for a multi-compressor refrigeration system according to the invention comprises a substantially horizontal collecting pipe (4) having a gaseous refrigerant iniet (10) for feeding a gaseous refrigerant to said collecting pipe (4), said collecting pipe (4) having a bottom (6) for collecting precipitated oil; at least one oil outlet (16) connecting to the bottom (6) of the collecting pipe (4), said oil outlet (16) discharging the precipitated oil; and at least one gaseous refrigerant outlet (14) arranged within the collecting pipe (4) vertically spaced apart from the bottom (6) thereof, said gaseous refrigerant outlet (12) discharging the gaseous refrigerant.

Description

MANIFOLD FOR A MULTI-COMPRESSOR REFRIGERATION SYSTEM

The present invention relates to a manifold for a multi-compressor refrigeration system and a multi-corn pressor refrigeration system comprising such a manifold.

In vapor compression refrigeration systems usually a certain amount of oil is added to the refrigerant in order to lubricate the moving mechanical parts in the compression cycle. On its way from the evaporator(s) to the compressor(s) the oil at least partially precipitates from the refrigerant. However, the amount of precipitated oil depends on the length of the conduits, the velocity of the refrigerant and the viscosity of the oil, which is a function of the pressure and the temperature. These parameters may change in operation, in particular, when some of the evaporators and/or compressors are switched on or off. In consequence the compressors are not supplied with oil continuously, but rather receive the oil in batches, which badly affects their operation.

Some multi-compressor systems are therefore equipped with an additional suction collection container in which the oil precipitates from the gaseous refrigerant leaving the evaporator(s) and is then supplied to the compressors.

However, such a suction collection container is expensive and it leads in operation to a loss of pressure within the compression cycle and reduces the performance of the vapor compression cycle. Furthermore, such a suction collection container is very prone to rust and needs a lot of space.

Accordingly, it would be beneficial to provide a space-saving, durable and high- performance multi-compressor refrigeration system and manifold which allows for a continuous supply of oil to the compressors. Exemplary embodiments of the invention include a gas suction and oil refeeding manifold for a multi-compressor refrigeration system, comprising a substantially horizontal collecting pipe having a gaseous refrigerant inlet for feeding a gaseous refrigerant into said collecting pipe, said collecting pipe having a bottom for collecting precipitated oil, at least one oil outlet connecting to the bottom of the collecting pipe, said oil outlet discharging the precipitated oil and refeeding it to a respective compressor, and at least one gaseous refrigerant outiet arranged within the collecting pipe vertically spaced apart from the bottom thereof, said gaseous refriger- ant outlet discharging the gaseous refrigerant and feeding it to a respective compressor.

Exemplary embodiments of the invention further include a multi-compressor refrigeration system comprising a set of compressors, at least one condensor, at least one expansion device, at least one evaporator, and refrigerant conduits circulating a refrigerant therethrough, wherein a gas suction and oil refeeding manifold, as disclosed herein, is arranged between the at least one evaporator and the set of compressors.

Embodiments of the invention will be described in greater detail below with reference to the enclosed figures, wherein

Figure 1 shows a schematic sectional view of a gas suction and oil refeeding manifold for a multi-compressor refrigeration system according to a first embodiment of the invention.

Figure 2 shows a schematic sectional view of a gas suction and oil refeeding man- ifold for a multi-compressor refrigeration system according to a second embodiment of the invention.

Figure 1 shows a sectional sectional view of a first gas suction and oil refeeding manifold 2 for a multi-compressor refrigeration system. The manifold 2 comprises a horizontal collecting pipe 4 which is closed at both ends 5. In the exemplary embodiment of Fig. 1 an upside down T-piece is arranged approximately in the middle of the collecting pipe 4, and this upside down T-piece forms a gaseous refrigerant inlet 10 for feeding gaseous refrigerant from at least one evaporator (not shown) into the collecting pipe 4. The gaseous refrigerant inlet 10 discharges into the upper portion 8 of the collecting pipe 4 in a downward direction.

In alternative embodiments (not shown), the gaseous refrigerant inlet 10 may be arranged at the side of the collecting pipe 4 and it may also discharge the refrigerant horizontally into the collecting pipe 4, but not from the bottom up.

The collecting pipe 4 comprises a bottom 6 for collecting precipitated oil, and it has five gaseous refrigerant outlets 14 which are vertically spaced apart from the bottom 6 of the collecting pipe 4 in order to discharge gaseous refrigerant from the collecting pipe 4.

These gaseous refrigerant outlets 14 are connected to or integrally formed into gaseous refrigerant discharging pipes 12, 18, 20, respectively, that extend in a downward direction through the bottom 6 of the collecting pipe 4 to a respective compressor 28 and that in operation deliver the gaseous refrigerant to the respective compressor 28. Each compressor 28 comprises a pressure line 30 which in operation delivers the compressed refrigerant to a condenser (not shown). The gaseous refrigerant discharging pipes 12, 18, 20 and the bottom 6 of the collecting pipe 4 are connected in a gas-tight manner, particularly welded together.

Three gaseous refrigerant outlets 14 and respective gaseous refrigerant discharging pipes 12, 18, 20 are arranged on the left hand side of the gaseous refrigerant inlet 10 and two gaseous refrigerant outlets 14 and respective gaseous refrigerant discharging pipes 12 are arranged on the right hand side of the gaseous refrigerant inlet 10. It is to be noted that the number of outlets 14 and discharging pipes 12, 18, 20 shown in Figure 1 is only exemplary and the manifold 2 may comprise any number of inlets 10, outlets 14 and discharging pipes 12, 18, 20 needed in a specific embodiment.

The gaseous refrigerant outlets 14 shown in Figure 1 are facing away from the gaseous refrigerant inlet 10 so that the gaseous refrigerant has to change its flowing direction before entering into the respective gaseous refrigerant outlet 14. This generates curls in the gaseous refrigerant which improve the precipitation of the oil comprised in the gaseous refrigerant. The gaseous refrigerant outlets 14 are formed as oblique end portions of the gaseous refrigerant discharging pipes 12, 18, 20. In the embodiment of Fig. 1 , these oblique end portions include an angle of 45° with respect to a horizontal plane, and the upper ends of these oblique end portions are spaced apart from inner wall of the upper portion of the collecting pipe 4 at a small distance.

In an embodiment of the invention, the gaseous refrigerant discharging pipes 12, 18, 20 can be introduced into the collecting pipe 4 until the gaseous refrigerant dis- charging pipes 12, 18, 20 hit the upper portion 8 of the inner wall of the collecting pipe 4. Thus, no further adjustment of the gaseous refrigerant discharging pipes 12, 18, 20 is necessary which facilitates the fabrication of the manifold 2. The two gaseous refrigerant discharging pipes 18, 20 shown on the left hand side of the collecting pipe 4 comprise an outer pipe 18 and an inner pipe 20, respectively, wherein the inner pipe 20 is arranged inside the outer pipe 18. The outer pipe 18 is circumferentially connected to the inner pipe 20 at a position below the bottom 6 of the collecting pipe 4, said connection forming a gas-tight joint 22. This allows to produce the manifold 2 having equal-sized openings in the bottom 6 of the collecting pipe 4, in which gaseous refrigerant discharging pipes 12, 18, 20 can be inserted which can be customized for the respective compressor 28. A suitable diameter for the openings in the manifold 2 and thus the maximum diameter for the gaseous refrigerant discharging pipes 12, 18, 20 to be inserted is 54 mm. In the embodiment of Fig. 1 the gaseous refrigerant discharging pipes 20 having a smaller diameter can be utilized for smaller compressors 28, and the gaseous refrigerant discharging pipes 12 having a larger diameter can be utilized for larger compressors 28 having a higher output.

The inner pipe 20 comprises a lateral opening 24 above the gas-tight joint 22 for discharging precipitated oil which collects at the bottom of the gap between the outer pipe 18 and the inner pipe 20. A suitable diameter for the lateral opening 24 is 5 mm.

Oil outlets 16 connect to the bottom 6 of the collecting pipe 4 that in operation discharge the oil which is precipitated from the gaseous refrigerant and collects at the bottom 6 of the collecting pipe 4. The oil outlets 16 are connected to or integrally formed into corresponding oil pipes 17 that extend in a downward direction to a respective compressor 28 and that in operation deliver the oil to a corresponding compressor 28. Said oil pipes 17 comprise a valve 26, respectively, in order to regulate the amount of oil which is delivered to the respective compressor 28. These valves 26 may be of any conventional kind, particularly they can be formed as mechanical or solenoid valves. Figure 2 shows a schematic sectional view of a second gas suction and oil refeed- ing manifold 31 for a multi-compressor refrigeration system.

The structure of the second gas suction and oil refeeding manifold 31 corresponds to the one of the first gas suction and oil refeeding manifold 2, and like features of the second gas suction and oil refeeding manifold 31 are designated with like reference.

For clarity reasons, only the left compressor 28 is shown in Fig. 2.

A shutoff-valve 32, an inspection glass 38 and a solenoid valve 34 are arranged, from top to bottom, in the oil pipe 17 of the left compressor 28. The shutoff-valve 32 enables to close the oil outlet 16, e.g. if the compressor 28 is shut off. The solenoid valve 34 is controlled by a control unit (not shown) in order to supply a predetermined amount of oil to the compressor 28. The inspection glas 38 permits monitoring the oil in oil pipe 17.

In this embodiment, the oil pipe 17 is not directly connected to compressor 28 but opens into gaseous refrigerant discharging pipe 12. Thus, the oil is added to the gaseous refrigerant which is sucked in by the compressor 28 via the gaseous refrigerant discharging pipe 12. This simplifies the construction of the compressor 28 as it does not need an additional oil inlet. Such an arrangement leading the oil pipe 17 and the gaseous refrigerant discharging pipe 12 together at a point before the compressor 28 can be provided for one or more compressors of the multi-com- pressor refrigeration system.

Additionally, a maintenance vale 36 is arranged in a separate oil outlet 16 at the right hand side of the collecting pipe 4. The oil collected at the bottom 6 of the collecting pipe 4 can be discharged by said maintenance valve 36, e.g. in order to carry out an oil change. The collecting pipe 4 can have any profile, e.g. a round, elliptical or angular profile. The term "pipe" is to be unterstood to cover any of such profiles.

A gas suction and oil refeeding manifold according to exemplary embodiments of the invention as described above allows to efficiently precipitate oil from a gaseous refrigerant and to distribute the gaseous refrigerant continuously to a plurality of compressors and it eliminates the need of an additional suction collection container and the safety valves required therefor. This reduces the space, particularly the height, needed for the construction considerably and also reduces the costs of production.

Both the efficiency of oil precipitation as well as the efficiency of the vapor compression cycle are improved and it is ensured that every compressor will continuously receive the amount of oil it needs for proper operation, irrespective of the length of the conduits between the evaporator(s) and the compressor(s), the velocity of the refrigerant, the viscosity of the oil, the capacity and construction of the compressor, and the compressors being switching on and off. Compressors differing in capacity and construction can be operated reliably with such a gas suction and oil refeeding manifold.

Thus a multi-compressor refrigeration system comprising a gas suction and oil refeeding manifold according to the invention can be produced at less cost and can be operated very efficiently.

In an embodiment of the invention the gaseous refrigerant outlet is arranged in the upper half of the inner space of the collecting pipe. This ensures that no or very few oil enters into the gaseous refrigerant outlet even if a large amount of oil collects at the bottom of the collecting pipe.

In a further embodiment of the invention the gaseous refrigerant outlet connects to a gaseous refrigerant discharging pipe in order to discharge gaseous refrigerant from the collecting pipe and to deliver it to a downstream compressor. In another embodiment the gaseous refrigerant outlet is integrally formed into the gaseous refrigerant discharging pipe. This avoids an additional joint which would need further steps of assembly and maintenance.

In another embodiment the gaseous refrigerant discharging pipe is substantially vertical so that the manifold according to the invention fits easily into an existing multi-compressor refrigerating system and the gaseous refrigerant is effectively discharged into the downstream compressor.

In another embodiment the gaseous refrigerant discharging pipe runs through the bottom of the collecting pipe, particularly through corresponding holes in the bottom. This allows to assemble the manifold easily and conveniently. As a matter of course, the bottom of the collecting pipe and the gaseous refrigerant discharging pipe have to be connected in a gas-tight manner, particularly welded together.

In another embodiment the gaseous refrigerant outlets face away from the gaseous refrigerant inlet. This enhances the efficiency of the oil precipitation as the flow of the gaseous refrigerant has to turn by up to 180° when flowing from the inlet to the outlets which generates curls in the gaseous refrigerant. The oil comprised in the gaseous refrigerant cannot follow this rapid change of direction and is precipitated very efficiently, particularly at the front and side walls of the collecting pipe.

In another embodiment the gaseous refrigerant outlet is formed as an oblique end of a gaseous refrigerant discharging pipe. Further the assembly of the manifold can be facilitated as the refrigerant discharging pipe can be introduced into the collecting pipe until the top of the discharging pipe hits the top of the collecting pipe so that no further adjustment of the discharging pipe is necessary.

In a further embodiment the gaseous refrigerant discharging pipe comprises an outer pipe having a first diameter, and an inner pipe having a second diameter which is smaller than the first diameter, wherein the inner pipe runs inside the outer pipe. By this arrangement, gaseous refrigerant discharging pipe of various diameters can be inserted into openings of equal size of the collecting pipe.

In a further embodiment the outer pipe is circumferentially connected to the inner pipe at a position below the bottom of the collecting pipe, said connection forming a gas-tight joint. This permits producing the manifold with only one type of refrigerant discharging pipe but at the same time using a pipe with a smaller diameter for delivering the gaseous refrigerant to the compressor if this is desirable for the re- spective compressor.

In another embodiment the inner pipe comprises a lateral opening above the gas- tight joint in order to discharge precipitated oil which is collected at the bottom of the space between the outer and inner pipes above the joint.

In another embodiment the oil outlet connects to an oil-discharging pipe to deliver the precipitated oil to a downstream compressor.

In a further embodiment the oil outlet is integrally connected to the oil-discharging pipe to deliver the precipitated oil to a downstream compressor avoiding an additional joint.

In another embodiment the oil-discharging pipe is substantially vertical so that the oil will be delivered using the force of gravity.

In another embodiment a valve, in particular a solenoid valve, is arranged in the oil-discharging pipe. This permits regulating the amount of oil delivered to the respective compressor very conveniently.

In another embodiment at least one of the collecting pipe, the gas inlet, the gaseous refrigerant outlet, and the oil outlet, comprises a rust-proof material. In a further embodiment said rust-proof material is copper. Copper is a very convenient material for producing said components.

Embodiments of the invention relating to a multi-compressor refrigerating system also attain the advantages as described with regard to the gas suction and oil refeeding manifold.

The features, embodiments, and advantages as described with respect to the gas suction and oil refeeding manifold and the multi-compressor refrigerating system can also be realised, in terms of method steps, with a method for operating a gas suction and oil refeeding manifold and a multi-compressor refrigerating system according to the invention.

While the invention has been described with reference to exemplary embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt the particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed, but that the invention include all embodiments falling within the scope of the dependent claims.

List of reference numerals:

2 first gas suction and oil refeeding manifold

4 collecting pipe 5 pipe ends

6 bottom

8 upper portion

10 gaseous refrigerant inlet

12 gaseous refrigerant discharging pipe 14 gaseous refrigerant outlet

16 oil outlet

17 oil pipe

18 first gas outlet pipe

20 second gas outlet pipe 22 joint

24 lateral opening

26 solenoid valve

28 compressor

30 pressure line 31 second gas suction and oil refeeding manifold

32 shut-off valve

34 solenoid valve

36 maintenance valve

38 inspection glas

Claims

ClaimsK 70 452/8

1. Gas suction and oil refeeding manifold (2) for a multi-compressor refrigeration system, comprising: a substantially horizontal collecting pipe (4) having a gaseous refrigerant inlet (10) for feeding a gaseous refrigerant into said collecting pipe (4), said collecting pipe (4) having a bottom (6) for collecting precipitated oil; at least one oil outlet (16) connecting to the bottom (6) of the collecting pipe (4), said oil outlet (16) discharging the precipitated oil; and at least one gaseous refrigerant outlet (14) arranged within the collecting pipe (4) vertically spaced apart from the bottom (6) thereof, said gaseous refrigerant outlet (14) discharging the gaseous refrigerant.

2. Gas suction and oil refeeding manifold (2) of claim 1 , wherein the gaseous refrigerant outlet (14) is arranged in the upper half of the collecting pipe (4).

3. Gas suction and oil refeeding manifold (2) of claim 1 or 2, wherein the gaseous refrigerant outlet (14) connects to or is formed integrally into a gaseous refrigerant discharging pipe (12; 18, 20).

4. Gas suction and oil refeeding manifold (2) of claim 3, wherein the gaseous refrigerant discharging pipe (12; 18, 20) is substantially vertical.

5. Gas suction and oil refeeding manifold (2) of claim 3 or 4, wherein the gaseous refrigerant discharging pipe (12; 18, 20) runs through the bottom (6) of the collecting pipe (4).

6. Gas suction and oil refeeding manifold (2) of any of the preceding claims, wherein the gaseous refrigerant outlet (14) faces away from the gaseous refrigerant inlet (10).

7. Gas suction and oil refeeding manifold (2) of claim 6, wherein the gaseous refrigerant outlet (14) is formed as an oblique end of the gaseous refrigerant discharging pipe (12; 18, 20).

8. Gas suction and oil refeeding manifold (2) of any of the preceding claims, wherein the gaseous refrigerant discharging pipe (12; 18, 20) comprises an outer pipe (18) and a inner pipe (20), the inner pipe (20) running inside the outer pipe (18).

9. Gas suction and oil refeeding manifold (2) of claim 8, wherein the outer pipe (18) is circumferentially connected to the inner pipe (20) at a position below the bottom (6) of the collecting pipe (4), said connection forming a gas-tight joint (22).

10. Gas suction and oil refeeding manifold (2) of claim 9, wherein the inner pipe (20) comprises a lateral opening (24) above the gas-tight joint (22).

11. Gas suction and oil refeeding manifold (2) of any of the preceding claims, wherein the oil outlet (16) connects to an oil discharging pipe.

12. Gas suction and oil refeeding manifold (2) of claim 1 1 , wherein the oil discharging pipe is substantially vertical.

13. Gas suction and oil refeeding manifold (2) of claim 11 or 12, wherein a valve (26), in particular a solenoid valve, is arranged in the oil discharging pipe.

14. Gas suction and oil refeeding manifold (2) of any of the preceding claims, wherein at least one of the collecting pipe (4), the gas inlet (10), the gaseous refrigerant outlet (14) and the oil outlet (16) comprises a rustless material.

15. Gas suction and oil refeeding manifold (2) of claim 14, wherein the rustless material is copper.

16. Multi-compressor refrigeration system comprising a set of compressors (28), at least one condensor, at least one expansion device, at least one evaporator, and refrigerant conduits circulating a refrigerant therethrough; wherein a gas suction and oil refeeding manifold (2) of any of the preceding claims is arranged between the at least one evaporator and the set of compressors (28).

17. Multi-compressor refrigeration system of claim 16, wherein at least one oil discharging pipe (16) and at least one gaseous refrigerant outlet (14) is provided for each compressor (28), said at least one oil discharging pipe (16) and at least one gaseous refrigerant outlet (14) connecting the collecting pipe (4) to the respective compressor (28).