Compression system with overhead tichelmann heat exchangers

Abstract

A compression machine includes a compressor, a condenser, an expansion valve, an evaporator, and refrigerant. The refrigerant circulates between the compressor, the condenser, the expansion valve, and the evaporator. The evaporator includes a first plate heat exchanger and a second heat exchanger. The second plate heat exchanger is arranged downstream of the first plate heat exchanger with respect to the refrigerant flow coming from the expansion valve. The plates of the first plate heat exchanger and the plates of the second plate heat exchanger are arranged vertically. The first plate heat exchanger and the second plate heat exchanger are connected according to the Tichelmann principle.

Description

[0001] Compression machines are well known in the state of the art. The current use of a plate heat exchanger as an evaporator in a compression machine, especially when connecting the channels on one side and operating on the evaporation side from bottom to top, poses several physical problems.

[0002] The plate heat exchangers are designed to achieve the smallest possible temperature difference between the inflowing refrigerant flow and the outflowing medium to be cooled during full load operation. It is also desirable to achieve a high degree of efficiency. Problems arise particularly in partial load operation and at low temperatures.

[0003] The previous approach meant a large surface area for partial load operation, but also a lower flow velocity in the channels with a low volume flow.

[0004] As the compressors are now power-regulated in order to achieve an even better efficiency in partial load operation, this can lead to complications in the distribution of the refrigerant in the heat exchanger. In partial load operation, the refrigerant takes the path of least resistance, which means that it does not flow evenly through the entire transfer surface of the plates of the plate heat exchanger.

[0005] In addition, the reduction in the flow velocities of the refrigerant in partial load operation and a change in the viscosity of the oil contained in the refrigerant due to the low temperature can lead to undesirable oil displacements in the heat exchanger. The oil contained in the refrigerant comes from the oil used in the compressor.

[0006] The unwanted oil displacement in the heat exchanger in turn disrupts the heat transfer in the heat exchanger as well as the clean injection of the expansion valve.

[0007] In order to overcome these disadvantages, the rotational speed of the compressor is conventionally increased after a certain partial load time in order to remove the oil from the heat exchanger with a higher volume flow.

[0008] It would be desirable to overcome the aforementioned disadvantages of a compression machine, especially a compression refrigeration machine. In particular, it would be desirable to avoid undesirable oil displacements in the heat exchanger during partial load operation of the compression machine without having to increase the rotational speed of the compressor.

[0009] The present invention relates to a compression machine comprising a compressor. The compression machine further comprises a condenser, an expansion valve (throttling element), an evaporator and refrigerant. The refrigerant circulates between the compressor, the condenser, the expansion valve and the evaporator. The evaporator comprises a first plate heat exchanger and a second heat exchanger. The second heat exchanger is arranged downstream of the first plate heat exchanger with respect to the refrigerant flow coming from the expansion valve. The plates of the first plate heat exchanger and the second heat exchanger are arranged vertically. The refrigerant flow coming from the expansion valve flows through the first plate heat exchanger from top to bottom. This arrangement is also referred to as an overhead arrangement. The refrigerant outlet of the second heat exchanger is arranged at the same level or below the refrigerant outlet of the first plate heat exchanger. The first plate heat exchanger is connected according to the Tichelmann principle with respect to the refrigerant flow.

[0010] The Tichelmann principle refers to an arrangement of the connections on the plate heat exchanger in which the inlet connections are arranged on a first side of the plate heat exchanger and the outlet connections are arranged on an opposite second side of the plate heat exchanger. As a result, the flow lengths of the individual channels for the refrigerant are the same length. The flow lengths of the individual channels for the medium to which the cold is to be transferred from the refrigerant are also the same length. Regardless of the flow velocity, the plate heat exchangers are therefore self-regulating.

[0011] The plate heat exchanger can also be referred to as a plate heat transfer element.

[0012] The advantage of the compression machine according to the invention is that the refrigerant flow coming from the condenser is cooled by the downstream second heat exchanger before it is fed to the expansion valve. At the same time, the refrigerant flow that flows through the second heat exchanger and that comes from the first plate heat exchanger and flows to the compressor is heated and protects the compressor from liquid hammer and ensures an improvement in efficiency.

[0013] Furthermore, the connection of the plates of the first plate heat exchanger in the Tichelmann principle leads to a better distribution of the refrigerant flowing through in partial load operation. Although the refrigerant takes the path of least resistance in partial load operation, the flow is evenly distributed as all the flow lengths of the individual channels of the plate heat exchanger are the same length. This means that there is no difference in the distribution of the flow between full load operation and partial load operation.

[0014] The condenser is arranged downstream of the compressor. The condenser is preferably designed as a liquefier. The second heat exchanger is arranged downstream of the condenser in relation to the connections for the medium to be cooled. The expansion valve is arranged downstream of the second heat exchanger. The first plate heat exchanger is arranged downstream of the expansion valve with respect to the connections for the refrigerant. The second heat exchanger is arranged downstream of the first plate heat exchanger with respect to the connections for the refrigerant. The compressor is arranged downstream of the second plate heat exchanger.

[0015] The compression machine is preferably designed as a compression refrigeration machine.

[0016] The second heat exchanger is preferably designed as a plate heat exchanger.

[0017] The refrigerant flow coming from the expansion valve preferably flows through the second plate heat exchanger from top to bottom.

[0018] The second plate heat exchanger is preferably connected according to the Tichelmann principle with regard to the refrigerant flow.

[0019] The expansion valve is preferably arranged downstream of the second heat exchanger and upstream of the first plate heat exchanger with respect to the refrigerant flow.

[0020] With respect to the refrigerant flow, an oil separator is preferably arranged upstream of the condenser and downstream of the compressor. The oil separator is designed to separate between 70% and 95%, preferably between 80% and 90%, of the oil in the refrigerant. This preferably refers to the volume % of the oil in the refrigerant.

[0021] The compression machine is preferably designed for a cooling capacity of 30° C. to −100° C., preferably for a cooling capacity of −15° C. to −100° C., particularly preferably for a cooling capacity of −25° C. to −75° C. This preferably means that the medium to be cooled should preferably be cooled to a corresponding temperature. Preferably, this means that the refrigerant used in the compression machine has a corresponding minimum temperature.

[0022] The compression machine is preferably adapted to cool glycols, water, ethanol, salts, thermal oils and / or hydrocarbons.

[0023] The compression machine is preferably adapted to cool a brine.

[0024] The refrigerant is preferably HFCs, HFOs, PFCs, hydrocarbons or carbon dioxide.

[0025] The invention is described in more detail below with reference to FIG. 1, which shows the first plate heat exchanger, the second heat exchanger, which is preferably designed as a plate heat exchanger, the expansion valve and the connections of these elements.

[0026] FIG. 1 shows components of a compression refrigeration machine. More precisely, FIG. 1 shows a first plate heat exchanger 10 and a second plate heat exchanger 12. The second plate heat exchanger 12 is arranged downstream of the first plate heat exchanger 10 with respect to the refrigerant flow 16 coming from an expansion valve 14. With respect to the refrigerant flow 18 coming from a condenser (not shown), the second plate heat exchanger 12 is arranged upstream of the first plate heat exchanger 10. The refrigerant 18 coming from the condenser is thus cooled in the second plate heat exchanger 12. The medium to be cooled, preferably a brine, flows exclusively through the first plate heat exchanger 10. FIG. 1 shows the brine 20 flowing in and the brine 22 flowing out. The compression refrigeration machine is designed for a temperature range of −15° C. to −100° C.

[0027] The first plate heat exchanger 10 is arranged vertically. This means that the first plate heat exchanger 10 is arranged in an overhead position. The second plate heat exchanger 12 is also arranged vertically. The second plate heat exchanger 12 is therefore also arranged in an overhead position. In addition, the refrigerant outlet of the second plate heat exchanger 12 is arranged at the same level or below the refrigerant outlet of the first plate heat exchanger 10. The refrigerant therefore flows in the first plate heat exchanger 10 and in the second plate heat exchanger 12 from top to bottom and downwards overall. In this way, no unwanted liquid oil can accumulate in the plate heat exchangers 10, 12.

[0028] The first plate heat exchanger 10 is connected according to the Tichelmann principle. The second plate heat exchanger 12 is also connected according to the Tichelmann principle. This means that the flow lengths in the first plate heat exchanger 10 and in the second plate heat exchanger 12 are the same length. In other words, the path through all channels of the first plate heat exchanger 10 and the second plate heat exchanger 12, through which the refrigerant and the medium to be cooled flow, is the same length. This is shown by the flow arrows that can be seen in the first plate heat exchanger 10 and the second plate heat exchanger 12. This is achieved by arranging the inlet connections of the first plate condenser 10 on a first side and the outlet connections of the first plate condenser 10 on an opposite second side. Correspondingly, the supply connections of the second plate condenser 12 are arranged on a first side and the return connections of the second plate condenser 12 are arranged on an opposite second side.

[0029] On the one hand, this ensures that the refrigerant flows evenly through the first plate heat exchanger 10 and the second plate heat exchanger 12 in the event of partial load operation of the compression refrigeration machine, in particular in the event of partial load operation of a compressor (not shown). Furthermore, this ensures that the compressor is protected from liquid hammer, as the oil contained in the refrigerant coming from the first plate heat exchanger is heated as it flows through the second plate heat exchanger 12. The oil contained in the refrigerant comes from the compressor and cannot be completely removed even if an oil separator is provided. It has been shown that the overhead arrangement of the plate heat exchangers 10, 12 according to the invention and the connection of the plate heat exchangers 10, 12 according to the Tichelmann principle even makes it possible to dispense with an oil separator without causing liquid damage in the compressor. However, if separation of the oil is desired, an oil separator can be provided upstream of the condenser to further increase protection against liquid damage. By heating the oil in the second plate heat exchanger 12, condensation of the oil is avoided, which in turn prevents liquid oil from entering the compressor. Furthermore, the second plate heat exchanger 12 leads to an increase in the efficiency of the compression refrigeration machine.

Claims

1-11. (canceled)12. A compression machine, comprising:a compressor;a condenser;an expansion valve;an evaporator; andrefrigerant, wherein the refrigerant circulates between the compressor, the condenser, the expansion valve and the evaporator,wherein the evaporator comprises a first plate heat exchanger and a second heat exchanger,wherein the second heat exchanger is arranged downstream of the first plate heat exchanger with respect to the refrigerant flow coming from the expansion valve,wherein the plates of the first plate heat exchanger and the second heat exchanger are arranged vertically,wherein the refrigerant flow coming from the expansion valve flows through the first plate heat exchanger from top to bottom,wherein the refrigerant outlet of the second heat exchanger is arranged at the same level or below the refrigerant outlet of the first plate heat exchanger, andwherein the first plate heat exchanger is connected according to the Tichelmann principle with respect to the refrigerant flow.

13. The compression machine according to claim 12, wherein the expansion valve is arranged downstream of the second plate heat exchanger and upstream of the first plate heat exchanger with respect to the refrigerant flow.

14. The compression machine according to claim 12, wherein an oil separator is arranged upstream of the condenser and downstream of the compressor with respect to the refrigerant flow.

15. The compression machine according to claim 12, wherein the compression machine is a compression refrigeration machine.

16. The compression machine according to claim 12, wherein the second heat exchanger is a plate heat exchanger.

17. The compression machine according to claim 16, wherein the refrigerant flow coming from the expansion valve flows through the second plate heat exchanger from top to bottom.

18. The compression machine according to claim 16, wherein the second plate heat exchanger is connected according to the Tichelmann principle with respect to the refrigerant flow.

19. The compression machine according to claim 12, wherein the compression machine is configured for a refrigeration requirement of 30° C. to −100° C.

20. The compression machine according to claim 12, wherein the compression machine is configured for a refrigeration requirement of −15° C. to −100° C.

21. The compression machine according to claim 12, wherein the compression machine is configured for a cooling requirement of −25° C. to −75° C.

22. The compression machine according to claim 12, wherein the compression machine is adapted to cool glycols, water, ethanol, salts, thermal oils and / or hydrocarbons.

23. The compression machine according to claim 12, wherein the compression machine is adapted to cool a brine.

24. The compression machine according to claim 12, wherein the refrigerant comprises one or more of the following refrigerants: HFCs, HFOs, PFCs, hydrocarbons and carbon dioxide.

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