Compression system with an overhead tchelmann heat exchanger

Abstract

The invention relates to a compression machine comprising a compressor. The compression machine further comprises 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 comprises 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 art. The current use of a plate heat exchanger as an evaporator in a compression machine, particularly when connecting the channels on one side and operating from bottom to top on the evaporation side, presents several physical problems.

[0002] Plate heat exchangers are designed to achieve the smallest possible temperature difference between the incoming coolant flow and the outgoing medium to be cooled during full-load operation. Furthermore, high efficiency is desired. Problems arise particularly during partial-load operation and at low temperatures.

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

[0004] Since compressors are now power-controlled to achieve even greater efficiency during partial load operation, complications can arise in the distribution of the coolant in the heat exchanger. During partial load operation, the coolant takes the path of least resistance, which means that the entire transfer surface of the plate heat exchanger is not evenly distributed.

[0005] Additionally, the reduced flow velocity of the coolant during partial load operation, as well as a change in the viscosity of the oil contained in the coolant due to the low temperature, can lead to undesirable oil migration in the heat exchanger. The oil contained in the coolant comes from the oil used in the compressor.

[0006] The unwanted oil shift in the heat exchanger, in turn, disrupts the heat transfer in the heat exchanger as well as the clean injection of the throttle body.

[0007] To overcome these disadvantages, the speed of the compressor is conventionally increased after a certain partial load period 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, particularly a refrigeration compression machine. It would be particularly desirable to avoid undesirable oil displacement in the heat exchanger during partial load operation of the compression machine without having to increase the compressor speed. DE 20 2007 017723 U1 discloses a compression machine according to the preamble of claim 1.

[0009] The present invention relates to a compression machine according to claim 1, which has a compressor. The compression machine further comprises a condenser, a throttle element, an evaporator, and coolant. The coolant circulates between the compressor, the condenser, the throttle element, and the evaporator. The evaporator has 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 coolant flow coming from the throttle element. The plates of the first plate heat exchanger and the second heat exchanger are arranged vertically. The coolant flow coming from the throttle element flows through the first plate heat exchanger from top to bottom. This arrangement is also referred to as an overhead arrangement. The coolant outlet of the second heat exchanger is arranged at the same level as or below the coolant outlet of the first plate heat exchanger.The first plate heat exchanger is connected to the coolant flow according to the Tichelmann principle.

[0010] The Tichelmann principle refers to an arrangement of connections on a plate heat exchanger in which the inlet connections are located on a first side of the plate heat exchanger, and the outlet connections are located on a second, opposite side. This results in the flow lengths of the individual channels for the coolant being equal. Likewise, the flow lengths of the individual channels for the medium to which the cooling energy from the coolant is to be transferred are equal. Thus, plate heat exchangers are self-regulating, regardless of the flow rate.

[0011] The plate heat exchanger can also be called a plate heat exchanger.

[0012] The compression engine according to the invention has the advantage that the downstream second heat exchanger cools the coolant flow coming from the condenser before it is fed to the throttle device. At the same time, the coolant flow flowing through the second heat exchanger and coming from the first plate heat exchanger to the compressor is heated, protecting the compressor from liquid hammer and improving efficiency.

[0013] Furthermore, connecting the plates of the first plate heat exchanger according to the Tichelmann principle results in a better distribution of the coolant flowing through it during partial load operation. Although the coolant takes the path of least resistance during partial load operation, a uniform flow distribution results because all flow lengths of the individual channels of the plate heat exchanger are the same length. This means that there is no difference in the flow distribution between full load and partial load operation.

[0014] The condenser is arranged downstream of the compressor. The condenser is preferably designed as a condenser. The second heat exchanger is arranged downstream of the condenser with respect to the connections for the medium to be cooled. The throttle element is arranged downstream of the second heat exchanger. The first plate heat exchanger is arranged downstream of the throttle element with respect to the connections for the coolant. The second heat exchanger is arranged downstream of the first plate heat exchanger with respect to the connections for the coolant. The compressor is arranged downstream of the second plate heat exchanger.

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

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

[0017] The coolant flow coming from the throttle device flows through the second plate heat exchanger preferably from top to bottom.

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

[0019] The throttle element is preferably arranged downstream of the second heat exchanger and upstream of the first plate heat exchanger with respect to the coolant flow.

[0020] With respect to the coolant 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 contained in the coolant. This specification preferably refers to the vol% of the oil contained in the coolant.

[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. This preferably means that the coolant used in the compression machine has a corresponding minimum temperature.

[0022] The compression machine is preferably designed for cooling glycols, water, ethanol, salts, thermal oils and / or hydrocarbons.

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

[0024] The coolant is preferably HFC, HFO, PFC, hydrocarbons or carbon dioxide.

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

[0026] Figure 1 shows components of a refrigeration compression machine. More specifically, Figure 1 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 coolant flow 16 originating from a throttle element 14. With respect to the coolant flow 18 originating from a condenser (not shown), the second plate heat exchanger 12 is arranged upstream of the first plate heat exchanger 10. The coolant 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. Figure 1shows the inflowing brine 20 and the outflowing brine 22. The refrigeration compression machine is designed for a temperature range of -15 °C to -100 °C.

[0027] The first plate heat exchanger 10 is vertically oriented. This means that the first plate heat exchanger 10 is arranged in an overhead configuration. The second plate heat exchanger 12 is also vertically oriented. The second plate heat exchanger 12 is therefore also arranged in an overhead configuration. Furthermore, the coolant outlet of the second plate heat exchanger 12 is located at the same height as or below the coolant outlet of the first plate heat exchanger 10. The coolant therefore flows from top to bottom in the first plate heat exchanger 10 and the second plate heat exchanger 12, and overall downwards. This prevents unwanted liquid oil from accumulating 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 the second plate heat exchanger 12 are the same. 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 coolant and the medium to be cooled flow, is the same. This is represented by the flow arrows that can be seen in the first plate heat exchanger 10 and the second plate heat exchanger 12, respectively. This is achieved by arranging the inlet connections in the first plate condenser 10 on a first side and the outlet connections in the first plate condenser 10 on an opposite second side.Accordingly, the supply terminals of the second plate capacitor 12 are arranged on a first side and the outlet terminals of the second plate capacitor 12 are arranged on an opposite second side.

[0029] This ensures, on the one hand, that the coolant flows evenly through the first plate heat exchanger 10 and the second plate heat exchanger 12 when the refrigeration compression machine is operating at partial load, in particular when a compressor (not shown) is operating at partial load. Furthermore, it ensures that the compressor is protected from liquid hammer, since the oil contained in the coolant coming from the first plate heat exchanger is heated as it flows through the second plate heat exchanger 12. The oil contained in the coolant originates 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 make it possible to dispense with an oil separator without any liquid damage occurring in the compressor.However, if oil separation is desired, an oil separator can be installed upstream of the condenser to further increase protection against liquid damage. Heating the oil in the second plate heat exchanger 12 prevents oil condensation, which in turn prevents liquid oil from entering the compressor. Furthermore, the second plate heat exchanger 12 increases the efficiency of the refrigeration compression machine.

Claims

1. A compression machine, comprising: a compressor, a condenser, an expansion valve (14), an evaporator, and refrigerant, wherein the refrigerant circulates between the compressor, the condenser, the expansion valve and the evaporator, wherein the evaporator comprises a first plate heat exchanger (10) and a second heat exchanger (12), wherein the second heat exchanger is arranged downstream of the first plate heat exchanger with respect to the refrigerant flow (16) coming from the expansion valve, characterised in that the plates of the first plate heat exchanger and the second heat exchanger are arranged vertically, wherein the evaporator is arranged such that 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, and wherein the first plate heat exchanger is connected according to the Tichelmann principle with respect to the refrigerant flow.

2. The compression machine according to claim 1, 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.

3. The compression machine according to any one of the preceding claims, wherein an oil separator is arranged upstream of the condenser and downstream of the compressor with respect to the refrigerant flow.

4. The compression machine according to any one of the preceding claims, wherein the compression machine is designed as a compression refrigeration machine.

5. The compression machine according to any one of the preceding claims, wherein the second heat exchanger is designed as a plate heat exchanger.

6. The compression machine according to claim 5, wherein the refrigerant flow coming from the expansion valve flows through the second plate heat exchanger from top to bottom.

7. The compression machine according to claim 5 or 6, wherein the second plate heat exchanger is connected according to the Tichelmann principle with respect to the refrigerant flow.

8. The compression machine according to any one of the preceding claims, wherein the compression machine is designed for a refrigeration requirement of from 30 °C to -100 °C, preferably from -15 °C to -100 °C, more preferably for a refrigeration requirement of from -25 °C to -75 °C.

9. The compression machine according to any one of the preceding claims, wherein the compression machine is adapted to cool glycols, water, ethanol, salts, thermal oils and / or hydrocarbons.

10. The compression machine according to any one of the preceding claims, wherein the compression machine is adapted to cool a brine (18, 20).

11. The compression machine according to any one of the preceding claims, wherein the refrigerant comprises one or more of the following refrigerants: HFCs, HFOs, PFCs, hydrocarbons and carbon dioxide.

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