Title:
HEAT EXCHANGER FOR A MOTOR VEHICLE AIR CONDITIONING SYSTEM
Kind Code:
A1


Abstract:
A heat exchanger for a motor vehicle air conditioning system is provided. The heat exchanger includes at least one inner tube and an outer tube, which at least regionally envelops an inner tube to form a gap through which a heat exchanger medium can flow. The inner tube can include two at least regionally wound and nested tube sections.



Inventors:
Seybold, Lothar (Nauheim, DE)
Seryi, Artem (Wiesbaden, DE)
Application Number:
13/679601
Publication Date:
06/06/2013
Filing Date:
11/16/2012
Assignee:
GM GLOBAL TECHNOLOGY OPERATIONS LLC (Detroit, MI, US)
Primary Class:
Other Classes:
165/154
International Classes:
F28D7/10
View Patent Images:



Primary Examiner:
COX, ALEXIS K
Attorney, Agent or Firm:
LKGlobal (GME) (7010 E. COCHISE ROAD SCOTTSDALE AZ 85253)
Claims:
What is claimed is:

1. A heat exchanger for a motor vehicle air conditioning system, comprising: at least one inner tube having at least two regionally wound and nested tube sections; and an outer tube that at least regionally envelops the at least one inner tube, forming a gap through which a heat exchanger medium flows.

2. The heat exchanger according to claim 1, wherein the at least two tube sections are helical or spiral.

3. The heat exchanger according to claim 1, wherein the at least two tube sections are arranged concentrically relative to each other.

4. The heat exchanger according to claim 1, wherein the at least two tube sections lie inside the outer tube, and have a fluid connection between them.

5. The heat exchanger according to claim 1, wherein the at least one inner tube branches into the at least two tube sections downstream from an inlet that passes through the outer tube.

6. The heat exchanger according to claim 5, wherein the at least two tube sections of the at least one inner tube empty into a junction upstream from an outlet that passes through the outer tube.

7. The heat exchanger according to claim 6, wherein the at least two tube sections each exhibit a changing helical diameter viewed in the axial direction.

8. The heat exchanger according to claim 7, wherein the helical diameter of one of the at least two tube sections enlarges in the axial direction, and the helical diameter of the other of the at least two tube sections diminishes in the axial direction.

9. The heat exchanger according to claim 8, wherein a first tube section of the at least two tube sections passes over via a curved segment into a second tube section of the at least two tube sections.

10. The heat exchanger according to claim 9, wherein the at least one inner tube includes a straight tube section, which connects the inlet or outlet with at least one of the first tube section of the at least two tube sections and the second tube section of the at least two tube sections.

11. The heat exchanger according to claim 9, wherein the at least one inner tube includes a straight tube section, which connects the outlet with at least one of the first tube section of the at least two tube sections and the second tube section of the at least two tube sections.

12. The heat exchanger according to claim 9, wherein the at least one inner tube includes a straight tube section, which connects which connects the first tube section of the at least two tube sections and the second tube section of the at least two tube sections with each other.

13. The heat exchanger according to claim 10, wherein the straight tube section runs inside both the first tube section of the at least two tube sections and the second tube section of the at least two tube sections.

14. The heat exchanger according to claim 10, wherein the straight tube section runs outside both the first tube section of the at least two tube sections and the second tube section of the at least two tube sections.

15. The heat exchanger according to claim 1, wherein an inlet and an outlet of the at least one inner tube pass through the outer tube on the very same face of the outer tube.

16. The heat exchanger according to claim 1, wherein the outer tube is designed as a low pressure line, and the at least one inner tube is designed as a high pressure line.

17. The heat exchanger according to claim 1, wherein an inlet and an opposing outlet of the outer tube is arranged downstream from an evaporator and upstream from a compressor, and wherein an inlet and an opposing outlet of the at least one inner tube is arranged upstream from an expansion device and downstream from a capacitor in the refrigerant circuit of a motor vehicle air conditioning system.

18. A motor vehicle air conditioning system, comprising: a refrigerant circuit, which couples together at least a compressor, a capacitor, an expansion device as well as an evaporator in terms of flow so as to circulate a heat exchanger medium, and which further includes a heat exchanger including: at least one inner tube having at least two regionally wound and nested tube sections; and an outer tube that at least regionally envelops the at least one inner tube to form a gap through which the heat exchanger medium flows.

19. A motor vehicle, comprising: an air conditioning system including a refrigerant circuit, which couples together at least a compressor, a capacitor, an expansion device as well as an evaporator in terms of flow so as to circulate a heat exchanger medium, and which further includes a heat exchanger including: at least one inner tube having at least two regionally wound and nested tube sections; and an outer tube that at least regionally envelops the at least one inner tube to form a gap through which the heat exchanger medium flows, wherein the tube sections are arranged concentrically relative to each other.

Description:

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to German Patent Application No. 10 2011 118 761.1, filed Nov. 17, 2011, which is incorporated herein by reference in its entirety.

TECHNICAL FIELD

This application pertains to a heat exchanger for a motor vehicle air conditioning system, which is designed in particular as an internal heat exchanger for increasing the efficiency of the air conditioning system.

BACKGROUND

Known in the art for increasing the performance and efficiency of motor vehicle air conditioning systems are heat exchangers incorporated inside of air conditioning systems, so-called internal heat exchangers (IHX), which thermally couple a section of the refrigerant circuit running between the evaporator and compressor with a section of the refrigerant circuit running between the capacitor and expansion valve. In this way, the relatively cold refrigerant flowing from the evaporator to the compressor can be used to (pre)cool or supercool the comparatively warm refrigerant being supplied to the expansion device on the high-pressure side of the refrigerant circuit.

For example, DE 10 2005 052 972 A1 describes a double-walled heat exchanger tube with an outer tube and an inner tube, which define a channel between them. The high-pressure refrigerant here flows through the channel, and the low-pressure refrigerant flows through the inner tube.

The geometric dimensions and shapes of the tubes are crucially important for optimizing the way in which such heat exchangers function in the refrigerant circuit. In an existing vehicle package, which offers virtually no space for individually adapting or modifying the outer contour or outer geometry of the heat exchanger, it is relatively difficult to adjust such heat exchangers to prescribed requirements in terms of their heat exchanger capacity on an individual basis, for example specific to the vehicle type.

Accordingly, it may be desirable to provide an improved heat exchanger for a motor vehicle air conditioning system. In addition, other objects, desirable features and characteristics will become apparent from the subsequent summary and detailed description, and the appended claims, taken in conjunction with the accompanying drawings and this background.

SUMMARY

According to one exemplary embodiment, provided is an improved heat exchanger for a motor vehicle air conditioning system, which offers a comparatively high heat exchange capacity given prescribed outer dimensions, and which can be adjusted in terms of its heat transfer capacity to various performance requirements, generally without any changes to its outer geometry. Further, it is to be possible to adjust the heat exchanger so as to replace existing heat exchanger configurations, in one example, to prescribed or already existing connections in motor vehicle air conditioning systems.

The heat exchanger provided in this way exhibits at least one inner tube and one outer tube, wherein the at least one inner tube is at least regionally enveloped by the outer tube, forming a gap through which the heat exchanger medium can flow. The inner tube further exhibits at least two tube sections that are at least regionally wound or coiled, as well as nested.

The tube sections can be spiral or helical, in one example, twisted, and in such a case can also be referred to as spiral tube sections.

In a geometrically simple design, the tube sections extend on an imaginary lateral surface of one or more cylinders, which are generally aligned substantially parallel to the outer tube. However, the two tube sections do not absolutely have to trace a lateral surface of an imaginary cylinder, but can also exhibit contours that irregularly deviate from a helical shape, e.g., oval or elliptical as well as nested regions. In this regard, the term wound or coiled tube section as used here also encompasses tube sections of any shape that regionally deviate from a geometric spiral or helical form.

A heat exchanger medium can here flow through the gap formed by the inner tube and outer tube, as well as the inner tube and its tube sections, wherein it is provided in one example, that the gap between the inner tube and outer tube can carry a flow opposite the direction in which the heat exchanger medium flows through the inner tube. The heat exchanger medium, also referred to as the coolant, can be 2,3,3,3-tetrafluoropropene or HFO-1234yf or tetrafluoroethane or R134a.

The at least regionally wound, bent, coiled, spiral or helical configuration of two tube sections makes it possible to increase the overall length and surface of the inner tube lying inside the outer tube as a whole, or variably adjust the latter to disparate requirements with respect to heat exchanger performance. Depending on how densely the tube sections are coiled or wound, the tube length of the tube sections as well as inner tube over which the heat exchanger medium is able to flow can be variably altered, wherein the coiling or winding density indicates a measure for the number of consecutive coils in the tube section in an axial direction.

For example, if a comparatively high heat exchanger performance is required, at least one of the two tube sections can be lengthened in terms of its tube length that is able to carry a flow, but clinched in an axial direction from a geometric standpoint, thereby yielding a shorter axial distance of individual coils as a whole, and hence an elevated coiling density. The heat exchanger medium flowing through the gap between the inner tube and outer tube can advantageously flow completely around the tube sections.

Providing at least two nested tube sections allows the heat exchanger medium flowing through the gap to also flow around or through a region lying radially between the tube sections, so as to further increase a heat exchange performance or capacity. Depending on the configuration of the nested tube sections, the heat exchanger performance of the heat exchanger can be varied by up to about 20% or more.

In one exemplary embodiment, the tube sections, for example, a first and a second tube section, exhibit different curvature radii or helical diameters. Further, the tube sections with a different curvature radius or helical diameter can be arranged concentrically relative to each other. For example, a first tube section viewed in the radial direction can run completely inside a second tube section. Given the same or similar winding density for the first and second tube section, the varying helical diameter yields a somewhat expanded tube length overall for the radially outermost tube section.

If both tube sections are to exhibit roughly the same tube lengths, the inner tube section can exhibit a higher axial winding density relative to the outer one, for example, and thus also have an elevated number of windings or coils.

Because in one example, the outer tube section exhibits a lower winding or coiling density than the inner tube section, the heat exchanger medium flowing around the inner tube can flow toward the inner tube section and away from the latter relatively unimpeded, even in the radial direction.

The two tube sections can be arranged and aligned concentrically to each other, so that the helical or spiral axes of the first and second tube section substantially come to overlap each other. In addition, the longitudinal axes of the tube sections can also coincide with a longitudinal axis of the outer tube, thereby yielding a radially symmetrical design overall for the outer tube and inner tube or for the outer tube and tube sections of the inner tube.

In another exemplary embodiment, there is a direct fluid connection between the tube sections lying inside the outer tube. The tube sections advantageously branch or empty inside the outer tube, so that the heat exchanger for the inner tube exhibits only one inlet or one outlet. This type of embodiment is important in one example, for establishing connections to existing air conditioning system components and integrating the heat exchanger into an existing air conditioning system design. Further, this makes it possible to keep the final assembly of the heat exchanger in the air conditioning system circuit comparatively simple and inexpensive, despite a rather complex internal tube arrangement.

It is here advantageously provided that the inner tube branches into the at least two tube sections downstream from an inlet that passes through the outer tube. The branching of the tube sections here lies inside the outer tube.

In like manner, the two separated tube sections of the inner tube empty into a junction upstream from an outlet of the inner tube that passes through the outer tube. This junction or opening of the two tube sections here also lies completely inside the outer tube. In this regard, even though several tube sections run inside the outer tube, only two tube fairleads need to be provided, at which the inner tube with a single inlet and with only a single outlet passes through the wall of the outer tube.

In another exemplary embodiment, at least one tube section exhibits a changing helical diameter viewed in the axial direction. In one example, it can be provided that the outer, for example second, tube section expand, substantially continuously, on the inlet or outlet side from a comparatively small helical diameter on the outlet or inlet side into an enlarged helical diameter. Viewed in the axial direction, the radially expanding tube section can exhibit a roughly conical outer geometry. Depending on the winding or coiling density of the respective tube section, such a conical progression can specifically alter and influence the flow conditions inside the outer tube.

For example, individual passages or sections that taper in terms of flow can be provided in one example, between the radially expanded outer tube section and the inner tube, e.g., causing the flow rate of the heat exchanger medium to become locally elevated. Further, the variable shape of the at least one tube section in the axial direction can induce or facilitate a targeted swirling of the heat exchanger medium flowing through the gap.

An expanding or tapering helical diameter of at least one tube section can be provided for both the outer and inner tube section. In relation to the axial direction, the respective other tube section can here exhibit a constant helical diameter, or also one that varies in the axial direction. Depending on the required flow conditions and a required heat exchange performance of the heat exchanger, the winding and coiling density of the individual tube sections can remain constant in the axial direction or vary.

If an initially inner tube section exhibits a helical diameter that varies in an axial direction, it can also be provided in one example, that the inner tube section quasi passes through the outer tube section that envelops it like a jacket in the radial direction.

Another exemplary embodiment can also provide that the helical diameter of a tube section increase in the axial direction, while the helical diameter of the other tube section decreases in the axial direction. The tube sections here exhibit a quasi opposite or reverse geometry in relation to the axial direction. For example, while a tube section near the inlet of the inner tube increases from a minimum helical diameter toward the outlet to a maximum spiral tube diameter, precisely the opposite configuration can be provided for the other tube section. The latter can exhibit its maximum helical diameter on the inlet side, and its minimum helical diameter on the outlet side, for example.

In another exemplary embodiment, the first tube section passes by way of a curved segment into the second tube section, which can be reversely situated relative to the first tube section. In one example, it is here provided that the first tube section extends over nearly the entire axial extension of the outer tube, and passes by way of the curved segment into an oppositely aligned second tube section. For example, such an arrangement makes it possible to provide the inlet and outlet for the inner tube on the very same side of the outer tube or heat exchanger.

By contrast, if the inlet and outlet of the inner tube are to be provided at diametrically opposed end sections of the outer tube, the inner tube in another exemplary embodiment can exhibit an additional, substantially straight tube section. This substantially, but not necessarily, straight tube section connects either the inlet or outlet of the inner tube with the first and/or second tube section. As an alternative, the substantially straight tube section can connect the first and second tube section with each other in terms of flow. The end sections of the straight tube section here in one example, pass over into respective curved segments, which in turn pass over into the first and second tube sections, generally without branching.

The substantially straight tube section can here run either completely inside the nested tube sections, or extend radially outside both tube sections.

Depending on whether the straight tube is provided between the two tube sections or immediately adjacent to just one end section of a tube section in terms of flow, aligned or opposed flow conditions arise in the individual, nested tube sections, so that the heat exchange performance of the heat exchanger can be tailored to prescribed requirements.

Another exemplary embodiment can further provide that an inlet and outlet of the inner tube pass through the outer tube on the very same side, or the very same end face of the outer tube. Such a configuration helps to save on space when positioning the heat exchanger, and can assist in optimizing how the installation space of the vehicle is divided up. In addition, this embodiment makes it possible to design the face of the outer tube facing away from the inlet and outlet to be largely free of penetration, so that a duct for the inlet and outlet of the inner tube through the outer tube need only be provided on one face of the outer tube.

In this exemplary embodiment, a non-branching configuration of the inner tube can also prove advantageous. This holds true in one example, when the inlet and outlet are connected in terms of flow with respectively oppositely aligned tube sections, which merge into each other by way of a curved section in the area of the side of the outer tube facing away from the inlet or outlet.

In another exemplary embodiment, the outer tube is designed as a low-pressure line, and the inner tube or its tube sections are provided as high-pressure lines. As a consequence, predominantly a compressed fluid flows through the inner tube, while a predominantly gaseous heat exchanger medium flows through the outer tube or the gap formed between the outer tube and heat exchanger tubes.

As a variation of the above, it can further be provided that the outer tube be designed as the high-pressure line, and the inner tube as the low-pressure line, and correspondingly be connected in terms of flow with the components of the refrigerant circuit.

A cross sectional geometry of the inner tube or its tube sections can exhibit any contour corresponding to the requirements. The inner tube can be completely or sectionally designed as a circular tube, a square or multi-sided tube, as well as exhibit an oval or elliptical cross section.

It is further provided for a heat exchanger exhibiting a largely tubular and cylindrical outer contour that opposing end sections of the outer tube can be arranged downstream from an evaporator and upstream from a compressor in the refrigerant circuit of a motor vehicle air conditioning system. Accordingly provided for the opposing end sections of the inner tube is an arrangement upstream from an expansion device and downstream from a capacitor in the refrigerant circuit of the air conditioning system.

It here generally holds true that the low-pressure line(s) is/are designed to couple the evaporator and compressor in terms of flow, while the high-pressure line(s) is/are designed to couple the capacitor and expansion device of the refrigerant circuit of the air conditioning system in terms of flow.

In another exemplary embodiment, the present disclosure further relates to a motor vehicle air conditioning system that exhibits a refrigerant circuit with at least a compressor, a capacitor, an expansion device as well as an evaporator, which are fluidically and serially interconnected by corresponding lines of the refrigerant circuit, and coupled together in terms of flow to circulate the refrigerant.

The refrigerant circuit here further exhibits a previously described, generally tubular heat exchanger, which induces a heat exchange between the low-pressure side lying downstream from the evaporator and high-pressure side of the refrigerant circuit lying upstream from the expansion device.

In another exemplary embodiment, the present disclosure further relates to a motor vehicle, which exhibits an air conditioning system configured in this way, or at least a heat exchanger of the kind described previously.

A person skilled in the art can gather other characteristics and advantages of the disclosure from the following description of exemplary embodiments that refers to the attached drawings, wherein the described exemplary embodiments should not be interpreted in a restrictive sense.

BRIEF DESCRIPTION OF THE DRAWINGS

The various embodiments will hereinafter be described in conjunction with the following drawing figures, wherein like numerals denote like elements, and wherein:

FIG. 1 is a schematic view of a motor vehicle air conditioning system with an internal heat exchanger;

FIG. 2 is a cross section through an internal heat exchanger according to an exemplary embodiment;

FIG. 3 is another cross section through an internal heat exchanger according to another exemplary embodiment;

FIG. 4 is a cross section through a heat exchanger according to another exemplary embodiment;

FIG. 5 is a cross section through a heat exchanger according to another exemplary embodiment;

FIG. 6 is a cross section through an internal heat exchanger according to another exemplary embodiment; and

FIG. 7 is a cross section through an exemplary embodiment of the heat exchanger with an inlet and outlet for the inner tube provided on the very same side of the outer tube.

DETAILED DESCRIPTION

The following detailed description is merely exemplary in nature and is not intended to limit the present disclosure or the application and uses of the present disclosure. Furthermore, there is no intention to be bound by any theory presented in the preceding background or the following detailed description.

The motor vehicle air conditioning system 1 schematically depicted on FIG. 1 exhibits a refrigerant circuit 12, which couples together the individual air conditioning system components, i.e., compressor 14, capacitor 16, internal heat exchanger 10, expansion device 18, or an expansion valve, as well as an evaporator 20, in terms of flow in a manner known in the art. On the high-pressure side, the internal heat exchanger 10 is situated downstream from the capacitor 16 and upstream from the expansion device 18. On the low-pressure side, the internal heat exchanger 10 is provided downstream from the evaporator 20 and upstream from the compressor 14. In this regard, the double arrow on FIG. 1 indicates the direction of flow for the heat exchanger medium or refrigerant, which can be R134a or HFO-1234yf.

The high-temperature heat exchanger medium exposed to a comparatively high pressure is supercooled upstream from the expansion device 18 by the low-pressure and low-temperature heat exchanger medium flowing in the opposite direction in the heat exchanger 10. This internal heat exchange in the refrigerant circuit 12 makes it possible to improve the efficiency of the motor vehicle air conditioning system 1.

The internal heat exchanger 10 of a motor vehicle air conditioning system 1 shown as an example on FIG. 2 exhibits an outer tube 30 and an inner tube 32. The inner tube is designed as a high-pressure line, and exhibits an inlet 22 as well as an outlet 24, wherein the inlet is to be provided downstream from the capacitor 16, and the outlet 24 is to be provided upstream from the expansion device 18. The outer tube 30 also exhibits an inlet 26 as well as an outlet 28 at an opposing end in the axial direction. The refrigerant circuit 12 here integrates the inlet 26 downstream from the evaporator 20, and the outlet 28 upstream from the compressor 14. The arrows at outlets 24, 28 or inlets 26, 28 again denote the direction of flow for the heat exchanger medium.

As a consequence, the outer tube 30 is allocated to the low-pressure side of the refrigerant circuitl2, while a heat exchanger medium exposed to a high pressure can flow through the inner tube 32 in the opposite direction.

In the exemplary embodiment according to FIG. 2, the inner tube 32 branches into two nested or interlaced tube sections 35, 36, which each exhibit a number of individual coils 35′, 35′. The branching 33 into tube sections 35, 36 here takes place near the inlet 22, while a junction 34 of the two helically coiled tube sections 35, 36 is provided upstream from the outlet 24. As a consequence, the tube sections 35, 36 extend between the respective branching 33 and junction 34. Both tube sections 35, 36 are aligned and arranged roughly concentrically to each other, are fed by the inlet 22, and both empty into the outlet 24 of the inner tube 32.

Viewed in the axial direction 78, a first tube section 36 here exhibits a constant helical diameter in the radial direction, thereby yielding an overall cylindrical lateral surface for the inner tube section 36. Much the same holds true for the second, outer tube section 35, which overall exhibits a larger helical diameter 37 than the first tube section 36. The second tube section 35 also exhibits a roughly cylindrical imaginary lateral surface.

The helical diameter 37 of the outer tube section of the inner tube can measure between about 80% and about 98% of the inner diameter of the outer tube, generally between about 90% and about 95%, which applies to all depicted exemplary embodiments. The (inner) tube section of the inner tube nested therein can exhibit a diameter lying between about 40% and about 60% of the inner diameter of the outer tube.

In the exemplary configuration according to FIG. 2, the first tube section 36 lies completely inside the second tube section 35 in a radial direction. The winding or coiling density of the first and second tube section 36, 35 can be substantially constant over the entire axial extension of the inner tube 32, but can also locally exhibit individual changes.

Let it further be noted with respect to all exemplary embodiments depicted in FIGS. 2 to 6 that the tube sections 35, 36 can exhibit considerably more coils 35′, 36′ or windings than shown on the figures. The diameter of the tube sections 35, 36 that can carry a heat exchanger medium generally lies within a range of several millimeters. The inner diameter that is able to carry a flow can measure between about 2 and about 8 mm, generally between about 4 and about 6 mm. A clearance 39 between two coils of the tube sections 35, 36 adjacent in the axial direction 78 can also lie in the millimeter range, in one example, between about 1 and about 6 mm, and generally measure less than about 4 mm.

The branching 33 and junction 34 of the tube sections 35, 36 causes the pressurized heat exchanger medium to flow through the latter in the same direction, for example from left to right on FIG. 1, while the heat exchanger medium supplied to the gap 38 via the inlet 26 in the opposite direction, quasi from right to left on FIG. 1, flows through the outer tube 30 to the outlet 28.

The exemplary embodiments described below and depicted in FIGS. 3 to 7 essentially differ only in terms of how their respective inner tube is designed, while the outer tube 30 and connections provided thereupon, e.g., inlet 22, 26 and outlet 24, 28, remain unchanged.

The heat exchanger 40 according to FIG. 3 exhibits an inner tube 42, which has a branching downstream from an inlet 22 that also divides the heat exchanger medium supplied to the flow into two tube sections 45, 46. While the inner tube section 46 exhibits an unchanged helical diameter over its entire extension in the axial direction 78, the outer tube section 45 is subject to a continuous tapering of its helical diameter in the axial direction 78 Immediately adjacent to the branching 43, the tube section 45 exhibits a helical diameter nearly corresponding to the inner diameter of the outer tube 30. By contrast, additional coils 45′ as well as other coils 45″ lying further downstream exhibit a smaller helical diameter by comparison thereto, so that the tube section 45 in the area of the junction 44 ultimately exhibits a helical diameter comparable to the other tube section 46.

In the cross section according to FIG. 3, an imaginary lateral surface that is tangent to the outer radii of the coils 45′, 45″ of the tube section 45 exhibits a conically tapering shape relative to the axial direction 78. As a result of the conical shape, the inner tube 42 also acts as a turbolator, so that the heat transfer fills more effectively or the transferred heat is greater. The same holds true analogously for the exemplary embodiment on FIG. 4 described below, in which both tube sections 55, 56 even act as turbolators.

In the exemplary embodiments according to FIG. 4, the inner tube 52 modified by comparison to FIG. 3 exhibits a branching 53 and junction 54, so that it correspondingly branches into two nested tube sections 55, 56. While the tube section 55 essentially corresponds to the tube section 45 in the exemplary embodiment depicted in FIG. 3, the tube section 56 lying radially inside on the inlet side exhibits a diametrically opposed outer contour in relation to the axial direction 78.

The coils 56′, 56″ lying downstream from the branching 53 exhibit a helical diameter that becomes larger as the distance away from the branching 53 increases. In this regard, the first tube section 56 exhibits a conically expanding lateral surface in the axial direction 78 relative to the direction of flow for the heat exchanger medium, while the other tube section 55 exhibits a correspondingly conically tapering lateral surface. The tube sections 55, 56 here mutually pass through each other, so that the first tube section 56 lies inside the second tube section 55 on the inlet side, while the reverse constellation arises on the outlet side, in which the first tube section 56 comes to lie radially outside the second tube section 55.

The exemplary embodiment shown in FIG. 5 depicts another inner tube 62, which is designed not to branch, and in which individual nested tube sections 65, 67 are situated one behind the other viewed in the direction of flow. In addition, the inner tube 62 exhibits another substantially straight section 63, which lies both inside a first tube section 65 as well as inside a second tube section 67. The straight tube section 63 immediately adjoins an inlet 22, and in proximity to the opposing outlet 24 empties into a curved segment 64, which in turn empties into the first tube section 65 oppositely aligned in the axial direction 78.

The first tube section 65 winds nearly completely around the straight tube section 63, and at the other end, i.e., near the inlet 22, passes over by way of another curved segment 66 into the second, outer tube section 67. The latter envelops both the straight tube section 63 and the inner first tube section 63 in the circumferential direction, and finally empties out into the outlet 24. Since the two tube sections 65, 67 are directly connected in terms of flow via a curved segment 66, the heat exchanger medium flows through the two nested tube sections 65, 67 in an opposite direction with the heat exchanger 60 in operation.

The exemplary embodiment according to FIG. 6 shows another embodiment of tube sections 75, 77 that sequentially empty into each other. While the inner tube 72 provided there also exhibits two completely nested tube sections 75, 77, they are not coupled with each other in terms of flow directly via a single curved segment 66 as in the exemplary embodiment according to FIG. 5, but rather by means of a straight tube section 73 lying in between.

In such an arrangement, the pressurized heat exchanger medium can flow through both tube sections 75, 77 in the same direction relative to the axial direction 78. It is here further provided that the inlet 22 empties directly into the radially outer tube section 77, and, at the opposite end of the heat exchanger 70 near the outlet, the respective tube section 77 passes over via a curved segment 74 into a substantially straight tube section 73, by way of which the tube section can flow back on the left side of the heat exchanger 70 depicted on FIG. 6.

The heat exchanger medium is there supplied to the inner tube section 75 via another curved segment 76, so that both tube sections 77, 75 eventually are sequentially connected with each other in terms of flow, but geometrically lie one inside the other. Further, the straight tube section 73 shown in FIG. 6 extends completely outside the two tube sections 75, 77. However, it would also be conceivable to run the straight tube section 73 connecting the two tube sections 75, 77 inside the inner tube section 75, similarly to FIG. 5.

As described, the inner tube 32, 42, 52 in FIGS. 2, 3 and 4 is divided, in that it exhibits a branching 33, 43, 53 and a junction 34, 44, 54. By contrast, the inner tube 62, 72 is not divided in the exemplary embodiments in FIGS. 5 and 6. In comparison to an undivided inner tube, a divided inner tube yields an improved heat transfer (since the heat transfer medium in the inner and outer tubes flows in the opposite directions) and a low pressure loss. However, an undivided inner tube simplifies production by comparison to the divided design, because no material bond is required at the branching 33, 43, 53 as well as junctions 34, 44, 54, so that in no leaks can arise at these locations as a matter of principle. In an undivided inner tube, at least half of the heat transfer medium flowing through the inner tube further flows opposite to the heat transfer medium between the inner and outer tube, thereby producing a good heat transfer on average.

The heat exchanger 80 depicted on FIG. 7 illustrates another variant of the inner tube 82, which similarly to the exemplary embodiment shown on FIG. 2 exhibits two nested tube sections 85, 86 with a constant helical diameter. The tube sections 85, 86 here do not branch, and merge into each other near the end section of the outer tube 30 shown on the left hand side of FIG. 7 via a curved segment 84. Both the inlet 22 and the outlet 24 of the inner tube 82 here pass through the outer tube 30 at one and the same face 87 of the outer tube 30 lying on the right hand side of FIG. 7, so that the inlet and outlet 22, 24 can be coupled with the heat exchanger 80 in close proximity to each other.

Production is simpler and tends not involve as many errors in the heat exchanger 80 depicted on FIG. 7, since fewer bending operations are required for the inner tube 82 overall. Also rendered unnecessary are material bonds, such as welds, because there is no branching or merging here, as had been the case for the heat exchangers in FIGS. 2, 3 and 4. Since the inner tube here has no additional straight tube section like the tube sections in FIGS. 5 and 6, the pressure drop between the outer tube 30 and inner tube 82 is smaller in this design.

The varying exemplary embodiments of diverse inner tubes 32, 42, 52, 62, 72, 82 for an internal heat exchanger 10, 40, 50, 60, 70, 80 in a motor vehicle air conditioning system 1 depicted in particular in FIGS. 2 to 7 only show isolated examples of the different configurations conceivable for at least two nested tube sections of an inner tube.

All of the exemplary embodiments shown here in conjunction with modifications thereto described only in words can involve being able to individually adapt the heat exchange performance of the respective heat exchangers 10, 40, 50, 60, 70, 80 to the varying requirements of differently configured air conditioning systems 1, while retaining prescribed outer dimensions.

While at least one exemplary embodiment has been presented in the foregoing detailed description, it should be appreciated that a vast number of variations exist. It should also be appreciated that the exemplary embodiment or exemplary embodiments are only examples, and are not intended to limit the scope, applicability, or configuration of the present disclosure in any way. Rather, the foregoing detailed description will provide those skilled in the art with a convenient road map for implementing an exemplary embodiment, it being understood that various changes may be made in the function and arrangement of elements described in an exemplary embodiment without departing from the scope of the present disclosure as set forth in the appended claims and their legal equivalents.