ACCUMULATOR FOR AN AIR CONDITIONING SYSTEM

Abstract

 The invention relates to an accumulator for an air conditioning system, which accumulator comprises:
- a closed container with an inlet opening arranged near the top of the container and an outlet opening for supply and discharge of a first medium;
- a heat exchanger arranged in the closed container and having a first channel and a second channel for transporting a second medium, the second channel being in heat exchanging contact with the first channel, wherein one end of the first channel is in fluid connection with the outlet opening and wherein the other end of the first channel debouches inside and near the top of the container,
wherein the heat exchanger comprises a first tube embodying the first channel and a second tube embodying the second channel, wherein the second tube is arranged in the first tube.

Description

[0001] The invention relates to an accumulator for an air conditioning system, which accumulator comprises:

• a closed container with an inlet opening arranged near the top of the container and an outlet opening for supply and discharge of a first medium;
• a heat exchanger arranged in the closed container and having a first channel (low pressure) and a second channel (high pressure) for transporting a second medium, the second channel being in heat exchanging contact with the first channel, wherein one end of the first channel is in fluid connection with the outlet opening and wherein the other end of the first channel debouches inside and near the top of the container.

[0002] Such an accumulator is for example known from DE 102006017071.

[0003] An accumulator separates the liquid from the gaseous refrigerant after the refrigerant has passed the expansion means of an air conditioning system. The accumulator is also used as a reservoir for refrigerant during the life time of the system and for balancing the dynamic characteristics of the air conditioning system. The heat exchanger is furthermore used to evaporate any droplets of refrigerant still present. If such refrigerant droplets would continue to the compressor, substantial damage could be done to the compressor.

[0004] The accumulator typically also provides drying means for removing any moist from the refrigerant. The accumulator is also a physical separator of the liquid and the gaseous refrigerant. Furthermore, the accumulator collects lubricant transported by the refrigerant and returns the lubricant in a controlled way to the refrigerant to ensure that the lubricant is evenly distributed throughout the air conditioning system.

[0005] The refrigerant used nowadays is for example R134, which is a 1,1,1,2-Tetrafluoroethane based refrigerant. Such a refrigerant is environment unfriendly (GWP = 13000).

[0006] An alternative to R134 is R744, which is basicly liquid carbon dioxide. Carbon dioxide has a high volumetric cooling capacity, which makes it an excelent refrigerant. However, if the liquid carbon dioxide would be used in the current air conditioning systems designed for R134 using an expansion valve for regulating the superheating after the evaporator, the accumulator would not be sufficient to ensure that all carbon dioxide is in gas phase before it enters the compressor, as the carbon dioxide cylce will be a high pressure regulated system.

[0007] It is known in the prior art, for example from DE 102006017071, to arrange a heat exchanger at the outlet of the accumulator to heat the refrigerant exiting the accumulator to ensure that in particular carbon dioxide based refrigerant is fully in gas phase when entering the compressor. In particular the main effect of the heat exchanger will be an increase in the performance of the air conditioning system.

[0008] However, such an accumulator according to DE 102006017071 is difficult or even impossible to mount in an engine compartment of an existing motor vehicle due to the space restrictions. If such an accumulator with additional heat exchanger on top of accumulator needs to be mounted in an existing vehicle, the air conditioning system needs to be redesigned to comply with the space restrictions.

[0009] Accordingly it is an object of the invention to provide an accumulator according to the preamble in which the above mentioned disadvantages are reduced or even removed.

[0010] This object is achieved with an accumulator according to the invention, which accumulator is characterized in that the heat exchanger comprises a first tube embodying the first channel and a second tube embodying the second channel, wherein the second tube is arranged in the first tube.

[0011] Having a heat exchanger with two tubes arranged inside of each other, a compact heat exchanger is obtained, which can easily be bent to conform to the restricted space inside of an accumulator. The two tubes of the heat exchanger can for example be bent in a spiral, a U-shape or extend over the full height of the accumulator. Despite the restricted space, this provides for sufficient length to exchange heat with the first medium, i.e. a refrigerant, to ensure that only refrigerant in gas phase exits from the accumulator.

[0012] Compared to an R134a air conditioning system, there is no correlation in a carbon dioxide system between the temperature and the pressure at the high pressure side. This allows for optimization of the pressure to achieve the optimum coefficient of performance (COP) for each load point. To this end it is necessary to prevent interaction between the internal heat exchanger and the accumulator, which would otherwise lead to additional evaporation of liquid refrigerant in the accumulator. By arranging the second (high pressure) tube within the first tube, the high pressure side is shielded from the accumulator.

[0013] The first tube could be made from a composite material, which will further isolate the second tube from the accumulator. It also simplify the manufacture of such a first tube.

[0014] In a preferred embodiment of the accumulator according to the invention, the second tube is provided with a plurality of heat conducting elements extending substantially radially between the outer surface of the second tube and the inner surface of the first tube.

[0015] Preferably, the heat conducting elements are wires, such that a brush-like covering of the second tube is obtained.

[0016] As the first medium or refrigerant is substantially in gas phase when passing the heat exchanger, the heat conducting elements extending into the space through which the refrigerant flows do not provide too much back pressure, while the plurality of elements provide a large heat conducting surface, such that any liquid droplets of the refrigerant are easily heated in the heat exchanger into the gas phase by the second medium.

[0017] In another embodiment of the accumulator according to the invention a passage is arranged in the wall of the first tube and the passage is in fluid connection with the bottom zone of the closed container.

[0018] When the first medium flows through the space between the first tube and the second tube, the pressure will be a bit lower, than the pressure in the container. Due to the venturi principle any lubricants present at the bottom of the container will be sucked into through the passage and transported along with the gas phase first medium.

[0019] In another embodiment of the invention a conduit extends between the bottom zone of the closed container and the passage.

[0020] The first and second tube can be bent, for example into a U-shape, such that both tubes run along the bottom of the container and the passage in the first tube can be positioned near the bottom zone of the container.

[0021] However, if, for example, such an arrangement of bent tubes is not desired, a conduit can be arranged between the passage and the bottom zone of the closed container.

[0022] In yet another embodiment of the accumulator according to the invention filter means are arranged on the inlet opening for filtering the inflowing first medium.

[0023] The filter means could furthermore comprise drying means for drying the inflowing first medium.

[0024] With the filter means any water or other particles are filtered out from the refrigerant, to prevent wear to the air conditioning system by the water and particles.

[0025] The closed container could be provided with a drain plug at the bottom of the container for serviceability.

[0026] The invention also relates to an air conditioning system comprising a refrigerant loop in which are arranged in succession, in flow direction, at least a compressor, a gas cooler, expansion means and an evaporator, wherein an accumulator according to the invention is furthermore arranged in the refrigerant loop, wherein the inlet opening is in fluid connection with the evaporator and the outlet opening is in fluid connection with the compressor and wherein the second tube is arranged in fluid connection between the gas cooler and the expansion means.

[0027] These and other features of the invention will be elucidated in conjunction with the accompanying drawings.

Figure 1 shows a cross-sectional view of a first embodiment of an accumulator according to the invention.

Figure 2 shows a cross-sectional view of a second embodiment of an accumulator according to the invention.

Figure 3 shows a perspective view of a part of figure 1.

Figure 4 shows a schematic view of an air conditioning system according to the invention.

Figure 1 shows an accumulator 1 for an air conditioning system. The accumulator 1 has a closed container 2 with a lid 3, which is mounted by bolts 4 to the base of the container 2.

[0028] An inlet pipe 5 runs through the lid 3 and is connected to a filter dryer 6. Through the inlet a low pressure first medium, such as a refrigerant is supplied to the closed container 2. When the first medium exits the filter dryer 6, the gas part of the first medium will rise towards the lid 3 of the container 2, while any liquid particles will fall down, due to gravity, and are collected at the bottom as a fluid level F. In an air conditioning system, this fluid F will mainly consist of a lubricant.

[0029] The gas part of the first medium will rise to the top of the container 2 and enter a first tube 7. This first tube 7 is U-shaped and runs along the bottom of the container 2 and through the lid 3 as outlet pipe 8.

[0030] A passage 9 is arranged in the first tube 7, such that fluid F can be sucked in by the passing gaseous first medium flowing through the first tube 7. This ensures an even distribution of the fluid F into the first medium.

[0031] A second tube 10 runs from the outside of the container 2 through the first tube 7 and exits again on the outside of the container 2. The second tube 10 is provided on the outer surface with a plurality of heat conducting elements 11 or hairs. (see figure 3). These hairs 11 ensure a good heat exchanging contact between the gaseous first medium running through the first tube 7 and a second medium running through the second tube 10. This second medium is preferably the same refrigerant as the gaseous medium in the first tube 7, but at high pressure. The heat exchange ensures that any possible liquid in the first tube 7 is evaporated before it exits the accumulator 1.

[0032] Figure 2 shows a second embodiment of an accumulator 20. This accumulator 20 also has a closed container 21 with a lid 22 mounted by bolts 23.

[0033] An inlet pipe 24 extends through the lid 22 and debouches in a filter dryer 25. The gas part of the medium entering through the filter dryer 25 will rise towards the lid 22, while any liquid particles will be collected in the fluid F at the bottom of the container 21.

[0034] A separation wall 26 is vertically arranged in the container 21. An opening 27 is arranged in the separation wall 26, such that the gaseous medium can enter the space 28 between the inner wall of the container 21 and the separation wall 26, which embody a first tube or channel. The gaseous medium can exit the container 21 via the first tube 28 at the bottom.

[0035] A second tube 29 runs through the space 28 and conducts a second medium, such that heat can be exchanged with the gaseous medium in the first tube 28, to ensure that no liquid particles will leave the accumulator 20.

[0036] Furthermore, a conduit 30 is provided in the separation wall 26 having an inlet opening 31 at the bottom and an outlet opening 32 at the top, such that fluid can be sucked into the gaseous medium flowing through the first tube 28.

[0037] Figure 4 shows a schematic view of an air conditioning system 40 of the invention. The air conditioning system 40 has a refrigerant loop 41. This refrigerant loop 41 is a tube through which a suitable refrigerant flows. The refrigerant loop 41 has in succession and in flow direction, a compressor 42, a gas cooler 43, expansion means 44 and an evaporator 45, similar to a conventional air conditioning system.

[0038] To ensure that all refrigerant coming from the evaporator 45 is in gas phase before it enters the compressor 42, the loop 41 according to the invention is provided with an accumulator 46 according to the invention, such as for example the embodiments of figure 1 or 2.

[0039] The (low pressure) refrigerant coming from the evaporator 45 enters the accumulator 46 and runs through a first tube (see figures 1 and 2) and then exits towards the compressor.

[0040] The refrigerant coming from the gas cooler 43 and running to the expansion means 44, which typically has a high temperature and a high pressure, is guided through the second tube of the accumulator (see figures 1 and 2) to ensure that the low pressure refrigerant in the first tube does not contain any liquid particles, which could damage the compressor 42.

Claims

1. Accumulator for an air conditioning system, which accumulator comprises:

- a closed container with an inlet opening arranged near the top of the container and an outlet opening for supply and discharge of a first medium;

- a heat exchanger arranged in the closed container and having a first channel and a second channel for transporting a second medium, the second channel being in heat exchanging contact with the first channel, wherein one end of the first channel is in fluid connection with the outlet opening and wherein the other end of the first channel debouches inside and near the top of the container,
characterized in that
the heat exchanger comprises a first tube embodying the first channel and a second tube embodying the second channel, wherein the second tube is arranged in the first tube.

2. Accumulator according to claim 1, wherein the second tube is provided with a plurality of heat conducting elements extending substantially radially between the outer surface of the second tube and the inner surface of the first tube.

3. Accumulator according to claim 2, wherein the heat conducting elements are wires, such that a brush-like covering of the second tube is obtained.

4. Accumulator according to any of the preceding claims, wherein a passage is arranged in the wall of the first tube and wherein the passage is in fluid connection with the bottom zone of the closed container.

5. Accumulator according to claim 4, wherein a conduit extends between the bottom zone of the closed container and the passage.

6. Accumulator according to any of the preceding claims, wherein filter means are arranged on the inlet opening for filtering the inflowing first medium.

7. Accumulator according to claim 6, wherein the filter means comprise drying means for drying the inflowing first medium.

8. Air conditioning system comprising a refrigerant loop in which are arranged in succession, in flow direction, at least a compressor, a gas cooler, expansion means and an evaporator,
characterized in that an accumulator according to any of the preceding claims is furthermore arranged in the refrigerant loop, wherein the inlet opening is in fluid connection with the evaporator and the outlet opening is in fluid connection with the compressor and wherein the second tube is arranged in fluid connection between the gas cooler and the expansion means.

Drawing