Refrigeration system

Abstract

A refrigeration system, in particular a transport refrigeration system, comprising: a refrigerant circuit, which in particular works using CO.sub.2 as the refrigerant and in which there is guided a total mass flow of the refrigerant; a high-pressure-side heat exchanger arranged in the refrigerant circuit and cooling refrigerant compressed to a high pressure; at least one cooling stage which expands the principal mass flow from the intermediate-pressure collector to a low pressure in at least one cooling expansion member and in so doing makes refrigeration capacity available at a low-pressure-side heat exchanger; and a refrigerant compressor unit which compresses the principal mass flow from a low pressure to a high pressure, wherein the refrigerant compressor unit has a first compressor stage for compressing, to a medium pressure, the refrigerant of the principal mass flow supplied at low pressure, and a second compressor stage for compressing, to a high pressure, the refrigerant of the principal mass flow that has been compressed to a medium pressure.

Claims

1. A refrigeration system, comprising: a refrigerant circuit, which uses a refrigerant and in which there is guided a total mass flow of the refrigerant; a high-pressure-side heat exchanger arranged in the refrigerant circuit and cooling refrigerant compressed to a high pressure; an expansion member, which is arranged in the refrigerant circuit following on from the high-pressure-side heat exchanger and in the active state cools the total mass flow of the refrigerant by expansion and in so doing generates a principal mass flow of liquid refrigerant and an auxiliary mass flow of gaseous refrigerant, which enter an intermediate-pressure collector and are separated therein into the principal mass flow and the auxiliary mass flow; at least one cooling stage which expands the principal mass flow from the intermediate-pressure collector to a low pressure in at least one cooling expansion member and in so doing makes refrigerating capacity available at a low-pressure-side heat exchanger; a refrigerant compressor unit which compresses the principal mass flow from a low pressure to a high pressure, the refrigerant compressor unit comprising a plurality of cylinder units and a plurality of cylinder drives; wherein the refrigerant compressor unit has a first compressor stage for compressing, to a medium pressure, the refrigerant of the principal mass flow supplied at low pressure, and a second compressor stage for compressing, to a high pressure, the refrigerant of the principal mass flow that has been compressed to a medium pressure, and the auxiliary mass flow from the intermediate-pressure collector enters the second compressor stage of the refrigerant compressor unit for compressing to a high pressure, with the high pressure being higher than the medium pressure, and the medium pressure being higher than the low pressure; wherein a drive chamber of the refrigerant compressor unit, from which the compressor stages are driven, is held at medium pressure, wherein the drive chamber of the refrigerant compressor unit receives the cylinder drives and borders on the cylinder units; and further comprising at least one inlet chamber supplying medium pressure to at least one cylinder unit for the second compressor stage, the at least one cylinder unit for the second compressor stage positioned radially between the at least one inlet chamber and the drive chamber.

2. The refrigeration system in accordance with claim 1, wherein, CO.sub.2 is used as the refrigerant, and the low pressure lies at values in the range of 1 bar to 60 bar.

3. The refrigeration system in accordance with claim 1, wherein, CO.sub.2 is used as the refrigerant, and the medium pressure lies in the range of 20 bar to 120 bar.

4. The refrigeration system in accordance with claim 1, wherein, CO.sub.2 is used as the refrigerant, and the high pressure lies at values in the range of 50 bar to 160 bar.

5. The refrigeration system in accordance with claim 1, wherein the drive chamber is connected to a motor chamber of the refrigerant compressor unit via a connecting channel.

6. The refrigeration system in accordance with claim 1, wherein a high-pressure connection of the refrigerant compressor unit is arranged on a cylinder head of the second compressor stage.

7. The refrigeration system in accordance with claim 1, wherein a low-pressure connection of the refrigerant compressor unit is arranged on a cylinder head of the first compressor stage.

8. The refrigeration system in accordance with claim 1, wherein a medium-pressure outlet of the refrigerant compressor unit is arranged on a cylinder head of the first compressor stage.

9. The refrigeration system in accordance with claim 1, wherein a medium-pressure inlet of the refrigerant compressor unit is arranged in a portion of a motor housing.

10. The refrigeration system of claim 1, wherein the refrigerant circuit is integrated into a transport refrigeration system.

11. The refrigeration system of claim 1, wherein CO.sub.2 is used as the refrigerant.

12. The refrigeration system in accordance with claim 1, wherein the first compressor stage of the refrigerant compressor unit is connected to a medium-pressure-side heat exchanger, which cools the principal mass flow that has been compressed to a medium pressure before said principal mass flow enters the second compressor stage.

13. The refrigeration system in accordance with claim 12, wherein the medium-pressure-side heat exchanger is an external heat exchanger arranged outside the refrigerant compressor unit.

14. The refrigeration system in accordance with claim 1, further comprising an electric drive motor, wherein the principal mass flow compressed to a medium pressure enters a motor chamber of the refrigerant compressor unit for cooling of the electric drive motor after the cooling by a medium-pressure-side heat exchanger and prior to entry into the second compressor stage.

15. The refrigeration system in accordance with claim 14, wherein the principal mass flow compressed to medium pressure and cooled in the medium-pressure-side heat exchanger enters the second compressor stage after having passed through the motor chamber.

16. The refrigeration system in accordance with claim 1, wherein the expansion member expands the total mass flow to an intermediate pressure.

17. The refrigeration system in accordance with claim 16, wherein the intermediate pressure is higher than the medium pressure, and in that the auxiliary mass flow is expanded to the medium pressure by an auxiliary mass flow expansion member and enters the second compressor stage at the medium pressure.

18. The refrigeration system in accordance with claim 16, wherein the intermediate pressure corresponds substantially to the medium pressure.

19. The refrigeration system in accordance with claim 1, wherein a housing of the refrigerant compressor unit is formed from aluminum.

20. The refrigeration system in accordance with claim 19, wherein the housing of the refrigerant compressor unit comprises a housing case and bearing covers arranged on respective different sides of the housing case, the housing case and the bearing covers all being formed with aluminum.

21. The refrigeration system in accordance with claim 19, wherein the housing comprises cylinder heads which are formed with aluminum.

22. The refrigeration system in accordance with claim 1, wherein a refrigerant compressor of the refrigerant compressor unit is formed as a reciprocating compressor.

23. The refrigeration system in accordance with claim 22, wherein the at least one cylinder unit of the second compressor stage is arranged at an angular spacing relative to the at least one cylinder unit of the first compressor stage, based on a central axis of a drive shaft of the cylinder units.

24. The refrigeration system in accordance with claim 22, wherein all cylinder units of the compressor stages are arranged in a row.

25. The refrigeration system in accordance with claim 22, wherein at least one of the cylinder units forms the first compressor stage and at least one of the cylinder units forms the second compressor stage.

26. The refrigeration system in accordance with claim 25, wherein at least two cylinder units form the first compressor stage.

27. The refrigeration system in accordance with claim 1, wherein the refrigerant compressor unit comprises a refrigerant compressor and an electric drive motor.

28. The refrigeration system in accordance with claim 27, wherein the refrigerant compressor unit is provided by a semi-hermetic compressor, wherein both the electric drive motor and the refrigerant compressor unit are arranged in an overall housing of said semi-hermetic compressor.

29. The refrigeration system in accordance with claim 27, wherein the auxiliary mass flow, prior to entering the second compressor stage, is supplied to a motor chamber of the refrigerant compressor unit in order to cool the electric drive motor.

30. The refrigeration system in accordance with claim 29, wherein the auxiliary mass flow enters the second compressor stage after cooling of the electric drive motor in the motor chamber.

31. A refrigerant compressor unit, comprising: a refrigerant compressor; an electric drive motor; wherein the refrigerant compressor has (a) a first compressor stage for compressing, to a medium pressure, a refrigerant supplied at low pressure, and (b) a second compressor stage for compressing, to a high pressure, the refrigerant, that has been compressed to a medium pressure, with the high pressure being higher than the medium pressure, and the medium pressure being higher than the low pressure, the refrigerant compressor comprising a plurality of cylinder units and a plurality of cylinder drives; wherein the refrigerant compressor unit comprises a medium-pressure outlet connected to the first compressor stage and a medium-pressure inlet connected to the second compressor stage; wherein a drive chamber of the refrigerant compressor, from which the compressor stages are driven, is held at medium pressure, wherein the drive chamber of the refrigerant compressor receives the cylinder drives and borders on the cylinder units; and further comprising at least one inlet chamber supplying medium pressure to at least one cylinder unit for the second compressor stage, the at least one cylinder unit for the second compressor stage positioned radially between the at least one inlet chamber and the drive chamber.

32. The refrigerant compressor unit in accordance with claim 31, wherein the medium-pressure inlet opens out into a motor chamber of the electric drive motor for cooling the electric drive motor, and compressed refrigerant enters the second compressor stage after having passed through the motor chamber.

33. The refrigerant compressor unit in accordance with claim 31, wherein the drive chamber is connected to a motor chamber via a connecting channel.

34. The refrigerant compressor unit in accordance with claim 31, wherein the refrigerant compressor unit is formed as a semi-hermetic compressor, wherein both the electric drive motor and the refrigerant compressor are arranged in an overall housing of the semi-hermetic compressor.

35. The refrigerant compressor unit in accordance with claim 31, wherein the housing comprises cylinder heads which are formed with aluminum.

36. The refrigerant compressor unit in accordance with claim 31, wherein a high-pressure connection of the refrigerant compressor unit is arranged on a cylinder head of the second compressor stage.

37. The refrigerant compressor unit in accordance with claim 31, wherein a low-pressure connection of the refrigerant compressor unit is arranged on a cylinder head of the first compressor stage.

38. The refrigerant compressor unit in accordance with claim 31, wherein the medium-pressure outlet of the refrigerant compressor unit is arranged on a cylinder head of the first compressor stage.

39. The refrigerant compressor unit in accordance with claim 31, wherein the medium-pressure inlet of the refrigerant compressor unit is arranged in the region of a motor housing.

40. The refrigerant compressor unit in accordance with claim 31, wherein, CO.sub.2 is used as the refrigerant, and the low pressure lies at values in the range of 1 bar to 60 bar.

41. The refrigerant compressor unit in accordance with claim 31, wherein, CO.sub.2 is used as the refrigerant, and the medium pressure lies in the range of 20 bar to 120 bar.

42. The refrigerant compressor unit in accordance with claim 31, wherein, CO.sub.2 is used as the refrigerant, and the high pressure lies at values in the range of 50 bar to 160 bar.

43. The refrigerant compressor unit of claim 31, wherein CO.sub.2 is used as the refrigerant.

44. The refrigerant compressor unit in accordance with claim 31, further comprising a housing of the refrigerant compressor, the housing being formed from aluminum.

45. The refrigerant compressor unit in accordance with claim 44, wherein the housing comprises a housing case and, arranged on respective different sides of the housing case, bearing covers, wherein the housing case and the bearing covers are all formed with aluminum.

46. The refrigerant compressor unit in accordance with claim 31, wherein the refrigerant compressor is formed as a reciprocating compressor.

47. The refrigerant compressor unit in accordance with claim 46, at least one of the cylinder units forms the first compressor stage and at least one of the cylinder units forms the second compressor stage.

48. The refrigerant compressor unit in accordance with claim 47, wherein at least two cylinder units form the first compressor stage.

49. The refrigerant compressor unit in accordance with claim 47, wherein the at least one cylinder unit of the second compressor stage is arranged at an angular spacing relative to the at least one cylinder unit of the first compressor stage, based on a central axis of a drive shaft of the cylinder units.

50. The refrigerant compressor unit in accordance with claim 47, wherein all cylinder units of the compressor stages are arranged in a row.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 shows a schematic illustration of a cooling unit, in particular formed as a transport cooling unit, with a refrigeration system according to the invention;

(2) FIG. 2 shows a schematic illustration of a first exemplary embodiment of a refrigeration system according to the invention;

(3) FIG. 3 shows a schematic enlarged illustration of a refrigerant compressor unit for the first exemplary embodiment of the refrigeration system according to the invention;

(4) FIG. 4 shows a schematic illustration of a second exemplary embodiment of a refrigeration system according to the invention;

(5) FIG. 5 shows an enlarged illustration of the refrigerant compressor unit of the second exemplary embodiment of the refrigeration system according to the invention; and

(6) FIG. 6 shows a third exemplary embodiment of a refrigeration system according to the invention.

DETAILED DESCRIPTION OF THE INVENTION

(7) A cooling unit denoted as a whole by 10 comprises a thermally insulated housing 12, which encloses an interior 14, in which temperature-sensitive goods 16 or temperature-sensitive cargo 16 may be stored, the temperature-sensitive goods 16 or the temperature-sensitive cargo 16 being surrounded by a gaseous medium 18, in particular air, which is held at a defined temperature level in order to keep the temperature-sensitive cargo 16 or the temperature-sensitive goods 16 within a specified temperature range.

(8) The cooling unit 10 is preferably formed as a transportable cooling unit, for example as a structure for a lorry or a freight wagon or as a conventional transport container for transporting temperature-sensitive cargo 16 either by lorry or train or ship.

(9) In order to be able to maintain a defined or pre-specified temperature range for the cargo 16, a circulation flow 22 of the gaseous medium 18 is circulated in the interior 14, wherein, starting from a temperature-control unit 24, an inlet flow 26 enters the interior 14, passes through it, and enters the temperature-control unit 24 again as an outlet flow 28.

(10) The circulation flow 22 is generated here by a fan unit 32, which is arranged in the temperature-control unit 24 and is held at the desired temperature by an internal heat exchanger 34, which is arranged in a temperature-control unit 24.

(11) In this case, the inlet flow 26 preferably exits from the temperature-control unit 24 in a region close to a top wall 36 of the insulated housing 12, and the circulation flow 22 is preferably guided close to a bottom wall 38 of the insulated housing 12 back to the temperature-control unit 24, and in so doing forms the outlet flow 28 passing back to the temperature-control unit 24.

(12) In particular, the temperature-control unit 24 is arranged close to the top wall 36 of the insulated housing 12 and for example close to a front wall 48 or close to a rear wall 48 of the housing.

(13) An equipment unit 52 comprising a refrigerant compressor unit 54 with a refrigerant compressor 56 and an electric drive motor 58 is arranged preferably close to the temperature-control unit 24 on the thermally insulated housing 12, wherein the equipment unit 52 preferably also additionally comprises a first external heat exchanger 62 and an external fan unit 64, which for example generates an airflow 66 from ambient air, which airflow passes through the first external heat exchanger 62.

(14) As shown in FIG. 2, the refrigerant compressor unit 54, the inner heat exchanger 34, and the first external heat exchanger 62 are arranged in a refrigerant circuit of a refrigeration system 60 integrated in the cooling unit, said refrigerant circuit being denoted as a whole by 70.

(15) The refrigerant circuit 70 is connected to a high-pressure connection 72 of the refrigerant compressor unit 54, starting from which high-pressure connection a supply line 74 to the first external heat exchanger 62 leads, which heat exchanger cools a total mass flow G of refrigerant, in the present case in particular CO2, compressed to a high pressure by the refrigerant compressor 54, the refrigerant being present, in the case of CO2, in a trans-critical state.

(16) In this case, the refrigerant may be cooled in the first external high-pressure-side heat exchanger unit 62 either by ambient air, or also by contact with a heat-absorbing medium of any kind, for example also cooling water.

(17) After the external heat exchanger 62, the total mass flow G supplied at the high-pressure connection 72 of the refrigerant compressor unit 54 in the refrigerant circuit 70 passes through, in the case of CO2 in a trans-critical state, an expansion member 76 arranged in the refrigerant circuit 70, is expanded by said expansion member to an intermediate pressure PZ, and then enters an intermediate-pressure collector 82, in which the total mass flow G cooled by expansion divides into a principal mass flow H of liquid refrigerant, which settles in the form of a liquid refrigerant bath 84 in the intermediate-pressure collector 82, and an auxiliary mass flow Z, which forms a gas bubble 86 above the liquid bath 84.

(18) The principal mass flow H of liquid refrigerant, starting from the intermediate-pressure collector 82, is supplied to a cooling stage 92, which comprises a cooling expansion member 94, which cools the principal mass flow H to a low pressure PN by expansion, and, starting from here, the principal mass flow H enters the internal low-pressure-side heat exchanger 34, in which, due to the fact that refrigeration capacity has been made available, it is able to draw heat from the circulation flow 22 in the interior 18 of the cooling unit 10.

(19) The principal mass flow H heated in the heat exchanger 34 then enters the refrigerant compressor unit 54 at low pressure PN via a low-pressure connection 102.

(20) The refrigerant compressor 56 of the refrigerant compressor unit 54, as shown in FIG. 2 and FIG. 3, is formed as a reciprocating compressor and preferably comprises a first compressor stage 112, formed by two cylinder units 114a and 114b, each driven by a cylinder drive 115a, 115b, in particular an eccentric drive, each of which draws in the refrigerant of the principal mass flow H from an inlet chamber 116a, 116b and delivers it for example into a common outlet chamber 118. In so doing, the first compressor stage 112 compresses the refrigerant from the principal mass flow H supplied to the first compressor stage at low pressure, for example at values from 1 bar to 60 bar, to a medium pressure PM, which for example lies at values in the range of from 20 bar to 120 bar.

(21) The principal mass flow H compressed to a medium pressure PM is then supplied from a medium-pressure outlet 122 of the common outlet chamber 118 to a second external medium-pressure-side heat exchanger 124, which for example is likewise arranged in the equipment unit 52 and for example is likewise passed through by the external airflow 66.

(22) Due to the second external medium-pressure-side heat exchanger 124, it is possible to cool the refrigerant of the principal mass flow H compressed to a medium pressure PM back to a temperature close to ambient temperature, and to remove again from said refrigerant a significant part of the heat supplied during the compression.

(23) The cooled refrigerant of the principal mass flow H compressed to a medium pressure PM is supplied from the second external medium-pressure-side heat exchanger 124 to a medium-pressure inlet 128 of the refrigerant compressor unit 54 via a medium-pressure supply line 126, the medium-pressure inlet 128 being arranged on a motor housing 132 of the refrigerant compressor unit 54.

(24) In addition, the medium-pressure supply line 126 is also connected to the fan 86 of the intermediate-pressure collector 82, so that the auxiliary mass flow Z from the intermediate-pressure collector 82 is supplied via the medium-pressure supply line 126 likewise to the medium-pressure connection 128 of the refrigerant compressor unit 54, and the medium pressure PM adjusts so that it corresponds to the intermediate pressure PZ.

(25) The medium-pressure inlet 128 is preferably arranged on the motor housing 132 so that the incoming refrigerant enters a motor chamber 134, passes through the motor chamber 134 whilst cooling the electric drive motor 58, in particular whilst cooling a rotor 136 and a stator 138 of the electric drive motor, and then enters a second compressor stage 142 of the refrigerant compressor unit 54.

(26) The second compressor stage 142 likewise comprises two cylinder units 144a and 144b each driven by a cylinder drive 145a, 145b, in particular an eccentric drive, wherein the refrigerant compressed to a medium pressure PM and supplied to the second compressor stage 142 enters the cylinder units 144a and 144b via inlet chambers 146a and 146b, is compressed in said cylinder units, and then exits into an outlet chamber 148, which is connected to the high-pressure connection 72.

(27) In the first exemplary embodiment of the reciprocating compressor 54 according to the invention, the cylinder units 114a and 114b of the first compressor stage 112 and the cylinder units 144a and 144b of the second compressor stage 142 are driven via a common drive shaft 152, in particular a camshaft, which acts on the various cylinder drives 115a, 115b and 145a, 145b, is preferably connected coaxially with and in particular integrally to a rotor shaft 154 of the rotor 136, and together therewith forms an overall drive shaft 188.

(28) Furthermore, in the first exemplary embodiment of the refrigerant compressor unit 54, the cylinder drive chamber 156 receiving the drive shaft 152 and the cylinder drives 115a, 115b, 145a, 145b and bordering on the cylinder units 114a and 114b and also 144a and 144b is connected to the motor chamber 134 or transitions into the motor chamber, so that the cylinder drive chamber 156 is at medium pressure.

(29) This has the advantage that, as a result, in particular at the second compressor stage 142, only pressure differences between medium pressure and high pressure occur in the cylinder units 144a and 144b, and therefore the loading of cylinder drives 145a and 145b for the cylinder units 144a, 144b is lower than in the case of low pressure in the cylinder drive chamber 156.

(30) Similarly, the loading of the cylinder units 144a and 144b themselves, in particular of the pistons thereof, is also lower than in the case of low pressure in the cylinder drive chamber 156.

(31) As shown in FIG. 3, in the first exemplary embodiment of the refrigerant compressor unit 54 according to the invention, this is formed as a semi-hermetic compressor, in which the refrigerant compressor 56 and the electric drive motor 58 are arranged in an overall housing 130, which comprises a housing case 162, bearing covers 164 and 166 arranged on either side of the housing case 162, and bearing receptacles 174 and 176, which are integrally molded on the bearing covers 164 and 166 and which are formed from aluminum, wherein rolling bearings 184 and 186 are arranged in the bearing receptacles 174 and 176 and in this case support an overall drive shaft 188, comprising the drive shaft 152 and the rotor shaft 154.

(32) Furthermore, cylinder heads 192 and 194 are arranged on the housing case 162 and are likewise formed from aluminum, wherein the cylinder head 192 is associated with the cylinder units 114a and 114b and has the low-pressure connection 102, which is connected to the inlet chambers 116a and 116b, and has the outlet chamber 118, which is connected to the medium-pressure outlet 122.

(33) The cylinder head 194 is associated here with the cylinder units 144a and 144b, wherein the inlet chambers 146a and 146b are connected to the motor chamber 134 and/or the cylinder drive chamber 156, and the outlet chamber 148 is connected to the high-pressure connection 72.

(34) In the first exemplary embodiment of the refrigerant compressor unit 54 according to the invention, this is preferably arranged as an upright compressor, that is to say a central axis 202 of the overall drive shaft 188 runs substantially vertically, that is to say deviates at most by ±30° from a vertical.

(35) In order to deliver lubricant into the cylinder drive chamber 156, in particular to the cylinder drives 115a, 115b, 145a, 145b, for example a delivery channel 204 running at an incline to the central axis 202 of the overall drive shaft 188 is provided in said overall drive shaft and delivers lubricant into the cylinder drive chamber 156 from a lubricant sump 206 that forms above the lowermost cover 166 as considered in the direction of the force of gravity on account of the centrifugal force effective in the delivery channel.

(36) Alternatively, a lubricant pump unit driven by the electric drive motor 58 is provided in order to deliver the lubricant in the cylinder drive chamber 156.

(37) In order to control the electric drive motor 58, a converter 212 is also provided, which is likewise preferably arranged in the equipment unit 52.

(38) The speed of the electric drive motor 58 is controllable by means of this converter, and therefore the refrigeration capacity of the refrigerant compressor unit 54 is also controllable continuously within a designated power range.

(39) In a second exemplary embodiment of a refrigeration system 60′ according to the invention, shown in FIG. 4 and FIG. 5, those elements that are identical to those in the first exemplary embodiment are provided with like reference signs, and therefore, with regard to the description of said elements, reference may be made fully to the comments provided in relation to the first exemplary embodiment.

(40) In contrast to the first exemplary embodiment, the refrigerant compressor unit 54′ is provided with a refrigerant compressor 56′, which, in order to form the first compressor stage 112, comprises two cylinder units 114a and 114b, but, in order to form the second compressor stage 142, comprises just one cylinder unit 144, wherein all cylinder units 114a, 114b and 144 are driven by the common drive shaft 152.

(41) The ratio of the swept volume of the first compressor stage 112 to the swept volume of the second compressor stage 142 lies approximately in the range of from 1.5/1 to 2/1.

(42) In principle, it would be possible to arrange the cylinder units 114a, 114b and 144 at an angular spacing based on the central axis 202 of the drive shaft 152.

(43) A particularly advantageous solution, however, provides that the cylinder units 114a, 114b and 144 are arranged in a row.

(44) Furthermore, the cylinder head 192 associated with the first compressor stage 112, and the cylinder head 194 associated with the second compressor stage 142 are thus also combined to form an overall cylinder head 222, in which both the low-pressure connection 102, the medium-pressure outlet 122, and the high-pressure connection 72 are provided, whilst the medium-pressure inlet 128 is provided on the motor housing 132, for example on a side of the electric drive motor 58 opposite the cylinder drive chamber 156.

(45) In the second exemplary embodiment of the refrigerant compressor unit 54′, the overall drive shaft 188 is preferably arranged so that its central axis 202 runs substantially horizontally, that is to say for example deviates by most ±30° from an exactly horizontal orientation, wherein a lubricant sump 206′ is formed in particular in the lowermost region of the cylinder drive chamber 156 as considered in the direction of the force of gravity, and the cylinder drives 115a, 115b, 145 are lubricated from said lubricant sump.

(46) In a third exemplary embodiment of a refrigeration system according to the invention, shown in FIG. 6, which is based on the second exemplary embodiment, a valve 232 is also provided in the medium-pressure supply line 126 leading away from the intermediate-pressure collector and towards the medium-pressure inlet 128, which valve is arranged in particular between the intermediate-pressure collector 82 and an outlet of a medium-pressure line 125 leading from the second external heat exchanger 124 to the medium-pressure supply line 126 and thus makes it possible to set an intermediate pressure PZ in the intermediate-pressure collector 82, in such a way that this intermediate pressure does not necessarily have to be identical to the medium pressure PM, and instead it is possible to keep the intermediate pressure PZ higher than the medium pressure PM.

(47) If the valve 232 is formed here as an expansion valve, it is thus possible, when the auxiliary mass flow is expanded by the expansion valve 232, to additionally also cool the auxiliary mass flow, so that this auxiliary mass flow has an improved cooling effect when cooling the electric drive motor 58.

(48) In addition, in the third exemplary embodiment, those elements that are identical to those in the previous exemplary embodiments are also provided with like reference signs, and therefore reference is made to the comments in relation to the previous exemplary embodiments.