Intermediate cooler for air-conditioning refrigerant

Abstract

An intermediate heat exchanger for refrigerant which passes through a high pressure side and a low pressure side in which the refrigerant has a different temperature circulating in an air conditioning loop. The heat exchanger includes a thin pressure-stable vessel defining at least one longitudinal compartment therein, and a flat multi-chamber tube through which refrigerant on one side flows. The tube extends through the at least one compartment and is spaced from at least two opposing walls of the compartment. Heat exchange ribs roughly fill the compartment between the tube and the two opposing walls, wherein refrigerant on the other side flows through the compartment between the tube and the two opposing walls.

Description

CROSS REFERENCE TO RELATED APPLICATION(S)

Not applicable.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not applicable.

REFERENCE TO A MICROFICHE APPENDIX

Not applicable.

TECHNICAL FIELD

The present invention relates to heat exchangers, and more particularly toward intermediate cooling of refrigerant circulating in an air-conditioning loop.

BACKGROUND OF THE INVENTION

AND

TECHNICAL PROBLEMS POSED BY THE PRIOR ART

Air-conditioning loops commonly include a refrigerant flowing through a compressor, gas cooler, evaporator (heat exchanger) and expansion valve, where the refrigerant passes through a high pressure side and a low pressure side in which the refrigerant has a different temperature.

One heat exchanger for exchanging heat between the high and low pressure sides, often referred to as an internal heat exchanger in transcritical air conditioning loops, is known from DE 196 35 454 A1 which provides improved heat exchange rates. However, manufacture of this device (arranged flat in the incorporation space in the vehicle) appears to be fairly demanding, among other things because the flat multi-chamber tubes are deformed as coils and insertion of the heat-conducting ribs between the windings of the coils is also complicated.

An intermediate heat exchanger is also disclosed in DE 103 22 028 B4, which is integrated as a coaxial tube in the collecting tube of the evaporator. This is a compact configuration which provides some ease of manufacture.

Another device for the same area of application is disclosed in U.S. Pat. No. 6,681,597 B1, in which the high pressure side and low pressure side flow through extruded, flat multi-chamber tubes which extend into a collection reservoir with their broad flat sides in conductive heat exchange relationship.

The present invention is directed toward improving upon the prior art to provide an easy to manufacture, compact heat exchanger for high and low pressure sides of an air-conditioning loop which provides efficient heat exchange.

SUMMARY OF THE INVENTION

In one aspect of the present invention, an intermediate heat exchanger is provided for refrigerant which passes through a high pressure side and a low pressure side in which the refrigerant has a different temperature circulating in an air conditioning loop. The heat exchanger includes a thin pressure-stable vessel defining at least one longitudinal compartment therein, and a flat multi-chamber tube through which refrigerant on one side flows. The tube extends through the at least one compartment and is spaced from at least two opposing walls of the compartment. Heat exchange ribs roughly fill the compartment between the tube and the two opposing walls, wherein refrigerant on the other side flows through the compartment between the tube and the two opposing walls.

In one form of this aspect of the present invention, at least one of the opposing walls is curved, and the ribs fill the compartment between the curved wall and the flat multi-chamber tube.

In another form of this aspect of the present invention, at least one longitudinal wall divides the vessel into at least two compartments, wherein the. multi-chamber tube extends in the longitudinal direction of the compartments and is substantially straight through at least one compartment. In a further form, the flat multi-chamber tube has a U-bend between two parallel straight portions, wherein the straight portions separately extend through two parallel compartments separated by the at least one longitudinal wall.

In still another form of this aspect of the present invention, the heat exchange ribs are arranged so as to be exposed to essentially no pressure loads.

In yet another form of this aspect of the present invention, the vessel is substantially cylindrical with closing covers at each end of the cylinder.

In another form of this aspect of the present invention, a plurality of longitudinal walls divide the vessel into a plurality of parallel longitudinal compartments. In a further form, a flat multi-chamber tube extends through each vessel compartment, with the tubes being arranged in series with one tube configured to input or output the refrigerant, and at least one other tube configured to output or input, respectively, the refrigerant. In a still further form, the one tube has a greater cross-section than the other tubes. In yet a further form, the vessel is substantially cylindrical, and the one tube extends substantially along the center plane of the cylindrical vessel.

In still another form of this aspect of the present invention, the vessel is substantially cylindrical, and the cross-sectional shape of the compartments is generally rectangular.

In yet another form of this aspect of the present invention, the chambers in the flat multi-chamber tube have a diameter of about 1.20 mm or less.

In another form of this aspect of the present invention, the length to diameter ratio (L/D) of the vessel is at least 3:1.

In still another form of this aspect of the present invention, both the vessel and the multi-chamber tube are extruded.

In yet another form of this aspect of the present invention, the ribs have walls extending longitudinally through the compartment.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a longitudinal cross-section through a first embodiment of an intermediate heat exchanger incorporating the present invention;

FIG. 2 is an axial cross-section through heat exchanger of FIG. 1;

FIG. 3 is a perspective view of one end of the heat exchanger of FIG. 1 showing inlets and outlets for the refrigerant;

FIG. 4 is an axial cross-section through a second embodiment of a heat exchanger incorporating the present invention;

FIG. 5 is a longitudinal schematic view of a third embodiment of a heat exchanger incorporating the present invention;

FIG. 6 is an axial cross-section through a fourth embodiment of a heat exchanger incorporating the present invention;

FIG. 7 is an axial cross-section through a fifth embodiment of a heat exchanger incorporating the present invention;

FIG. 8 is an axial cross-section through a sixth embodiment of a heat exchanger incorporating the present invention; and

FIG. 9 is an axial cross-section through a seventh embodiment of a heat exchanger incorporating the present invention.

DETAILED DESCRIPTION OF THE INVENTION

As illustrated in FIGS. 1 and 2, in accordance with one embodiment of the invention, a vessel 20 is formed as a round tube produced by extrusion. The tube has two longitudinal walls 22 and 24, which divide the tube into three compartments 26, 28, 30, each of which include a flat extruded multi-chamber tube 34 extending roughly the entire length of the compartments (the multi-chamber tube 34 could also be a soldered or welded tube with an internal insert forming the chambers).

In the illustrated embodiment, each multi-chamber tube 34 has two rows of passages 36 having a diameter of about 1.20 mm or less.

Further, each multi-chamber tube 34 is provided with one or more heat-conducting ribs 40 that fills up the cross-section of the corresponding compartmet, preferably as fully as possible, so that the refrigerant flowing there does not flow through large, free cross-sectional spaces and therefore heat exchange with the tubes 34 is enhanced.

In the FIGS. 1-2 embodiment, the refrigerant on the high pressure side (arrows in FIG. 1) flows on the top through the middle connection opening into the flat and larger multi-chamber tube 34 (in the center of the vessel 20). The refrigerant then flows downward through that tube, and at the vessel bottom is distributed to the two other smaller multi-chamber tubes 34, through which the refrigerant flows back up. From the two smaller tubes 34, the refrigerant flows via two outflow openings to an expansion device (not shown), and then, for example, through an evaporator.

In the FIGS. 1-2 embodiment, the refrigerant on the low pressure side flows into a corresponding inflow opening 44 either into the middle compartment 28 (in which case it flows downward through the heat exchange ribs 40 in the middle compartment 28 and then is distributed to the two other compartments to flow up through them), or the refrigerant on the low pressure side is distributed from the inflow opening 44 to all three compartments 26, 28, 30 (in which case it flows downward through all three compartments 26, 28, 30 and then to the compressor [not shown] in the loop).

The tube on the top and bottom has appropriate covers 48, which complete the vessel 20. As is apparent, flow channels for the refrigerant on the high pressure side are formed in cover 48.

The above described components may advantageously be made of aluminum, which parts may be assembled and joined by soldering.

FIG. 3 shows inflow and outflow of the refrigerant on the high pressure side and low pressure side one embodiment such as described in connection with FIGS. 1-2 above. Reference numbers 44, 50, 52 show flow passages of the refrigerant on the low pressure side, with this low pressure refrigerant flowing at 44 into the middle compartment 28 (or flowing out of this compartment there). A connection block 54 includes channels and may be soldered with the other mentioned components, and includes two additional inflow (or outflow) openings or channels 50, 52 that communicate with the other two compartments 28, 30. Openings or channels 60, 62, 64, 66, 68 are also provided for the refrigerant on the high pressure side, such openings being formed in the upper cover 48 and communicate with the multi-chamber tubes 34.

FIG. 4 illustrates another practical example in which only the middle compartment 28 is occupied by the multi-chamber tube 34 and heat exchange ribs 40. Refrigerant on the low pressure side flows through the ribs 40 in the middle compartment 28, and may (or may not) also flow in the two other compartments 26, 30. (It should be recognized that the longitudinal walls 70 can be made significantly thinner than is illustrated by FIG. 4, since roughly the same pressure is present in the compartments 26, 28, 30).

FIG. 5 schematically shows another embodiment incorporating the present invention, wherein the vessel 20 may have with a somewhat smaller degree of thinness. The multi-chamber tube 34 in this embodiment has a U-shaped bend 74, whereby inflow and outflow of the refrigerant may both occur on the upper cover 48 (where the reference HP stands for the high pressure side and LP for the low pressure side). The lower cover 48A is arched and the longitudinal wall 22 ends so that the refrigerant on the low pressure side can flow from compartment 26 back to the other compartment 28, with the remaining cross-section of both compartments 26, 28 being filled by heat exchange ribs 40 such as previously described.

FIGS. 6 and 7 show embodiments which facilitate insertion of the heat exchange ribs 40 with the multi-chamber tube 34 into the corresponding compartments, where the cross-section of compartments 26 and 30 in vessel 20 is configured with an appropriate shape. In the FIG. 6 embodiment, the wall thickness of the vessel 20 is partially increased somewhat at reference number 78, whereas, in FIG. 7, recesses 80 are included in the wall of vessel 20. Such embodiments are easy to produce by extrusion. Further, ordinary corrugated ribs can be used as heat exchange ribs 40, which are wound coil-like around the corresponding multi-chamber tube 34 and then inserted together with the tube into the appropriate compartment 26, 28, 30X.

Perhaps the simplest form of the present invention is shown in FIG. 8, wherein the multi-chamber tube 34 extends linearly through the vessel 20 along its center longitudinal plane. The semicircular cross-sections of the compartments 26 of vessel 20 created by the multi-chamber tube 34 are filled up with heat-conducting ribs 40 which have a rib height adapted to the round shape of vessel 20.

FIG. 9 illustrates yet another embodiment of an intermediate heat exchanger incorporating the present invention, which embodiment is particularly suitable for manufacture. In this embodiment, two longitudinal walls 22A, 24A include bent longitudinal edges 84, preferably having some elasticity, which lie against the inside of the vessel wall. The multi-chamber tube 34, the heat-conducting ribs 40 and the two longitudinal walls 22A, 24A may be advantageously combined into a stack and pushed together into the vessel 20 so that the longitudinal edges 84 abut the vessel wall, whereby perfect solder connections are made possible or supported. Moreover, the compartment 28 is filled up by heat-conducting ribs 40 that have a uniform rib height and are therefore favorable to manufacture.

Overall, the suitability for manufacture of intermediate heat exchangers incorporating the present invention can be understood from the description and the drawings. Further, it should be appreciated that the efficiency of heat exchange, and the ability to fit into limited space requirements, are further of heat exchangers according to the present invention because of a very thin configuration of the vessel 20. The thinness of the vessel 20, expressed by the length L/diameter D ratio (see FIG. 1), may be advantageously at least 3:1, although an L/D ration of 6:1 or even thinner is preferred.

Since the vessel 20 over its entire length is designed as a heat exchanger, good results in terms of heat exchange efficiency can be achieved. The vessel 20 and the intermediate heat exchanger have a noticeably slim appearance and are therefore particularly suitable for applications in which narrow spaces are present (according to the present invention, vessels with a length/diameter ratio of at least 3:1 or larger are considered slim vessels). Further, since the multi-chamber tubes 34 extend essentially straight through the compartments 26, 28, 30 (i.e., it need not be deformed), they may be readily assembled in the compartments together with the heat exchange ribs 40 almost completely filling up the remaining compartment cross-section, thereby providing both easy assembly and good heat exchange efficiency.

It should also be appreciated that the round shape of the longitudinal wall of the vessel 20 is able to withstand enormously high pressures, and therefore the heat exchange ribs 40 can be made from a very thin sheet material since it is not exposed to significant pressure stresses.

In addition, it should also be appreciated that the extrusion process for production of the vessel 20 makes it possible to design cross-section of the internal compartments 26, 28, 30 in the otherwise preferably round pressure vessel 20 to be rectangular, and as a result the heat exchange ribs 40 can be very favorably inserted there without significant squeezing and in so doing almost completely fill up the compartment as mentioned. Roughly rectangular or square compartment cross-sections can be advantageously achieved either by partially increasing the wall thickness of the vessel 20 or by including gradations of the otherwise round vessel in the longitudinal direction of the vessel 20, both of which can be efficiently manufactured by the deformation method of extrusion.

Still other aspects, objects, and advantages of the present invention can be obtained from a study of the specification, the drawings, and the appended claims. It should be understood, however, that the present invention could be used in alternate forms where less than all of the objects and advantages of the present invention and preferred embodiment as described above would be obtained.

Claims

1. An intermediate heat exchanger for refrigerant which passes 2 through a high pressure side and a low pressure side in which the refrigerant has a different temperature circulating in an air conditioning loop, comprising:

a thin pressure-stable vessel defining at least one longitudinal compartment therein;

a flat multi-chamber tube through which refrigerant on one side flows, said tube extending through said at least one compartment and spaced from at least two opposing walls of said compartment;

heat exchange ribs roughly filling the compartment between the tube and said two opposing walls, wherein refrigerant on the other side flows through the compartment between the tube and the two opposing walls.

2. The heat exchanger of claim 1, wherein at least one of the opposing walls is curved, and said ribs fill the compartment between said curved wall and said flat multi-chamber tube.

3. The heat exchanger of claim 1, further comprising at least one longitudinal wall dividing the vessel into at least two compartments, wherein the multi-chamber tube extends in the longitudinal direction of said compartments and is substantially straight through at least one compartment.

4. The heat exchanger of claim 3, wherein said flat multi-chamber tube has a U-bend between two parallel straight portions, wherein said straight portions separately extend through two parallel compartments separated by said at least one longitudinal wall.

5. The heat exchanger of claim 1, wherein said heat exchange ribs are arranged so as to be exposed to essentially no pressure loads.

6. The heat exchanger of claim 1, wherein said vessel is substantially cylindrical with closing covers at each end of the cylinder.

7. The heat exchanger of claim 1, further comprising a plurality of longitudinal walls dividing said vessel into a plurality of parallel longitudinal compartments.

8. The heat exchanger of claim 7, wherein a flat multi-chamber tube extends through each vessel compartment, with said tubes being arranged in series with one tube configured to input or output the refrigerant, and at least one other tube configured to output or input, respectively, the refrigerant.

9. The heat exchanger of claim 8, wherein said one tube has a greater cross-section than the other tubes.

10. The heat exchanger of claim 9, wherein said vessel is substantially cylindrical, and said one tube extends substantially along the center plane of the cylindrical vessel.

11. The heat exchanger of claim 1, wherein said vessel is substantially cylindrical, and the cross-sectional shape of the compartments is generally rectangular.

12. The heat exchanger of claim 1, wherein the chambers in the flat multi-chamber tube have a diameter of about 1.20 mm or less.

13. The heat exchanger of claim 1, wherein the length to diameter ratio (L/D) of the vessel is at least 3:1.

14. The heat exchanger of claim 1, wherein both the vessel and the multi-chamber tube are extruded.

15. The heat exchanger of claim 1, wherein said ribs have walls extending longitudinally through said compartment.