Tube-to-tube heat exchanger assembly

Abstract

A tube-to-tube heat exchanger for use in an air conditioning system of a motor vehicle has a unitary tube, which is internally longitudinally divided into a first passage and a second passage by a heat conductive primary web. One warm fluid line is directly connected to each end of the first passage, without the need for a separate connector. One cold fluid return line is directly connected to each end of the second passage, without the need for a separate connector. The fluid lines are connected to the heat exchanger by brazing. In one embodiment, the web is substantially planar and the cross-section of each of the first passage and the second passage is substantially D-shaped. The heat exchanger may further include a support web, extending perpendicularly from approximately mid-way along the primary web. In another embodiment, the cross-sections of the first and second passages may be substantially circular, with the primary web being shaped accordingly. In a further embodiment, the first passage may be substantially circular in cross-section and the second section may be substantially crescent-shaped, with the primary web being shaped accordingly.

Description

FIELD OF THE INVENTION

[0001] The invention relates to heat exchangers and is particularly concerned with heat exchangers for use in air conditioning systems of motor vehicles.

BACKGROUND OF THE INVENTION

[0002] It is known that an internal heat exchanger (otherwise known as a suction line heat exchanger or simply a heat exchanger) improves performance of an air conditioning or refrigeration system by allowing heat transfer between a warm liquid supply line and a cold vapor return line. The term “internal” in this context means that heat is being exchanged internally within the system, as compared to a condenser or an evaporator, for example, which exchange heat between the system and the environment. One type of internal heat exchanger that could be used in motor vehicle applications is a “tube-in-tube” or “duplex” heat exchanger where one fluid line extends through the center of the heat exchanger and another fluid line surrounds the first fluid line. One such tube-in-tube heat exchanger is taught in U.S. patent application Ser. No. 2001/0,020,786 A1, filed on Feb. 23, 2001 in the name of Takamatsu, et al. However, internal heat exchangers are not typically used in motor vehicles, because they tend to be bulky, heavy, and/or expensive. The tube-in-tube heat exchanger, for example, requires a complicated connector to separate the fluid line running through the center of the heat exchanger from the fluid line that surrounds it. Such connectors tend to be relatively large, heavy, expensive, difficult to install and they typically cause a significant increase in suction line pressure drop, which results when fluids travel around corners or edges, for example. Such pressure drops reduce the performance of the air conditioning system (or wherever the heat exchanger is located). In extreme cases, where suction line pressure drop is particularly significant, the performance of the air conditioning system may be worse than if a heat exchanger were omitted from the system.

[0003] In view of the above, it would be desirable to have a heat exchanger that is suitable for use in an air conditioning system of a motor vehicle, that is easily manufactured, that can be easily bent to conform to installation requirements, that has a simple and inexpensive connection to the refrigeration or air conditioning system, and that does not add excessive weight, bulk or suction line pressure drop.

SUMMARY OF THE INVENTION

[0004] According to a first aspect, the invention provides a tube-to-tube heat exchanger assembly especially for use in an air conditioning system of a motor vehicle, the assembly comprising a unitary heat exchanger comprising a tube internally longitudinally divided into a first passage and a second passage by a primary web, the primary web being heat conductive; a first pair of fluid lines; and a second pair of fluid lines; wherein one line of the first pair of fluid lines is directly connected to one end of the first passage and the other line of the first pair of fluid lines is directly connected to the other end of the first passage and one line of the second pair of fluid lines is directly connected to one end of the second passage and the other line of the second pair of fluid lines is directly connected to the other end of the second passage.

[0005] The invention could be used in applications beyond the context of motor vehicles, in a virtually unlimited range of applications where heat exchange is necessary or desirable.

[0006] Advantageously, different embodiments of the present invention may permit a heat exchanger for use in a motor vehicle that is easy to manufacture and/or is easy to bend to suit installation requirements, and/or is simply and inexpensively connected to a refrigeration or air-conditioning system and/or does not add significant weight, bulk or suction line pressure drop.

BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Preferred embodiments of the invention will now be described with reference to the attached drawings in which

[0008] FIG. 1 is a schematic view of a heat exchanger assembly shown within a representative air conditioning system of a motor vehicle;

[0009] FIG. 2a is a perspective view (not to scale) from one end of a heat exchanger, with directly connected fluid lines extending from the heat exchanger, in accordance with an embodiment of the present invention;

[0010] FIG. 2b is a perspective view of the heat exchanger and fluid lines of FIG. 2a, from the other end;

[0011] FIG. 2c is a longitudinal sectional view of the heat exchanger of FIG. 2a;

[0012] FIG. 2d is a cross-sectional view along lines 2d-2d of FIG. 2c;

[0013] FIG. 2e is a cross-sectional view along lines 2e-2e of FIG. 2c;

[0014] FIG. 3a is a cross-sectional view of a heat exchanger in accordance with another embodiment of the present invention;

[0015] FIG. 3b is a cross-sectional view of a heat exchanger in accordance with yet another embodiment of the present invention; and

[0016] FIG. 3c is a cross-sectional view of a heat exchanger in accordance with yet another embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] Referring to FIG. 1, a schematic view of a representative air conditioning system 10 of a large motor vehicle is shown, for illustration purposes. In this example, refrigerant 12 leaves a condenser 14 as a high pressure liquid and flows through an internal heat exchanger (IHX) 18 and then through a thermal expansion valve 20 and a rear auxiliary module evaporator 22. The refrigerant 12 leaves the rear auxiliary module evaporator 22 as a low pressure vapor and flows back through the IHX 18 and then through an accumulator 24 and a compressor 26. The refrigerant leaves the compressor 26 as a high pressure vapor and flows through the condenser 14.

[0018] When the refrigerant 12 leaves the condenser 14, it flows along two different paths in this embodiment. One path is through the IHX 18 as discussed above. The other path is through an orifice tube 30 and then through a front module evaporator 32, where the refrigerant 12 leaves as a low pressure vapor and then flows through the accumulator 24, as described above.

[0019] Referring to FIG. 2a, the IHX 18 is shown in perspective view (not to scale), from one end, with a warm fluid (liquid, in this example) supply line 34 and a cold fluid (vapor in this example) return line 36 extending from the other end the IHX 18. FIG. 2b illustrates the IHX 18 of FIG. 2a in a perspective view from the other end. Cross-sectional views are shown in FIG. 2c (along a longitudinal axis), in FIG. 2d (across the IHX 18), and in FIG. 2e (across the fluid lines 34, 36, looking towards the IHX 18). The IHX 18 is a generally cylindrical tube 38, with an internal, heat conductive, generally planar web 42 which divides the interior area of the IHX 18 into two passages 44, 46.

[0020] FIGS. 2a and 2d illustrate, that in a cross-section across the width of the IHX 18, the web 42 creates two substantially D-shaped passages 44, 46. Ends 48, 50 of the warm liquid supply line 34 and the cold vapor return line 36, respectively, are shaped to fit within the passages 44, 46, respectively. Although in FIGS. 2a, 2b and 2c, the warm liquid supply line 34 and the cold vapor return line 36 are only shown to extend from one end of the IHX 18, in operation, another warm liquid supply line (not shown) and another vapor return line (not shown) would extend from the other end of the IHX 18 in a similar manner, as suggested in FIG. 1. The combination of the IHX 18 directly connected to supply lines 34 and return lines 36 may be referred to as a heat exchanger assembly.

[0021] The IHX 18 is preferably a single or unitary piece of material, formed by extrusion. Because the purpose of a heat exchanger is to transfer heat, the material should be heat conductive. The IHX 18 is preferably made from aluminum in view of its cost, weight, heat conductivity, and ability to bend. Other materials that could be used include steel, stainless steel, copper, INCONEL™ material, or plastic.

[0022] The ends 48, 50 of the warm liquid supply line 34 and the cold vapor return line 36 are formed to fit within the passages 44, 46, respectively of the IHX 18 by one of many methods knows to those skilled in the art. One such method involves the use of a machine (not shown) which strikes the end of a fluid line with a punch to create the desired shape.

[0023] The ends 48, 50 of the warm liquid supply line 34 and the cold vapor return line 36 are then inserted within the passages 44, 46, respectively, and directly connected therein by brazing (not shown). The type of brazing material used is dependent, to an extent, upon the material used to manufacture the IHX 18, and would be known to those skilled in the art. For example, if the IHX 18 is made of aluminum, then the brazing material is preferably an aluminum alloy paste, where the paste is likely a suspension of aluminum in a paste of flux. If the IHX 18 is copper, for example, then the brazing material may be silver phosphorous.

[0024] Alternatively, the warm liquid supply line 34 and the cold vapor return line 36 could be directly connected to the IHX 18 by staking, where each line 34, 36 would be affixed to the IHX 18 through the use of mechanical force.

[0025] Prior to affixing the warm liquid supply lines 34 and the cold vapor return lines 36 to the IHX 18, the IHX 18 would be shaped to fit a contour (not shown) where it will be installed in a motor vehicle (not shown). The IHX 18 is shaped using a process known to those skilled in the art. One such process involves the use of a machine (not shown) to clamp one end or portion of the IHX 18, while another machine (not shown) pushes or pulls another portion of the IHX 18 to bend the IHX 18 to create the desired shape.

[0026] As noted above, FIG. 2d is a cross-sectional view of the IHX 18 taken along the width of the IHX 18, showing a particular configuration of the web 42. However, the cross-section can be modified by the use different web configurations, for example. One possible modification is shown in FIG. 3a, where the web 42, which may be referred to as a primary web 42, is essentially the same as that shown in FIG. 2d, with a vertical support web 50 added, which provides additional support to the IHX 18 when the IHX 18 is bent. With the embodiment shown in FIG. 2d, the entire primary web 42 can extend, and preferably would extend, the length of the IHX 18. In the embodiment shown in FIG. 3a, whereas the primary web 42 can extend the length of the IHX 18, the support web 50 terminates at positions (not shown) within the tube 38 approximately where the end of the supply lines 34 or the return lines 36 would be affixed to the IHX 18, since otherwise, the support web 50 would prevent the supply lines 34 or the return lines 36 from being pushed within the IHX 18. The supply lines 34 and the return lines 36 would then be affixed to the IHX 18 as described above.

[0027] Another variation of a web configuration is shown in FIG. 3b. In this embodiment, one pair of fluid lines, likely (although not necessarily) the return lines 36, would have their ends shaped in a circular form (not shown) to fit within the substantially circular area 54 created by the primary web 56 (unless the ends of the return lines 36, in their original form, would fit within the area 54 without the need for modification). Similar to the embodiment described above with respect to FIG. 3a, the support web 58 of FIG. 3b does not extend the length of the tube 38. Rather, the support web 58 terminates at positions (not shown) within the tube 38 approximately where the ends of the supply lines 34 (or the return lines 36, as the case may be) would be affixed to the IHX 18. In this embodiment, an end portion of each supply line 34 would then be shaped as a crescent to fit within the tube 38. The supply lines 34 and the return lines 36 would be affixed within the IHX 18 as described above.

[0028] Another embodiment is shown in FIG. 3c, where both the shape of the tube 38 and the web configuration are different from those described above. In the embodiment shown in FIG. 3c, the cross-sectional view of the tube 38 is substantially peanut shaped, with a primary web 62 defining two circle-shaped passages 64, 66. In this embodiment, the end portions of the supply line 34 and return line 36 may be able to fit within the passages 64, 66, respectively, of the IHX 18 without modification. However, the circular profiles of the passages 64, 66 may provide limited heat exchange, due to the reduced surface area, as compared to the web configurations in the other embodiments. As well, the circular profiles of the passages 64, 66 may restrict bending of the IHX 18, other than in the horizontal plane.

[0029] Numerous modifications and variations of the present invention are possible in light of the above teachings. It is therefore to be understood that within the scope of the appended claims, the invention may be practised otherwise than as specifically described herein. For example, while the IHX 18 above has been described as being primarily for use in an air conditioning application of a motor vehicle that has a rear auxiliary module and conventional refrigerant, the IHX 18 could be used for other applications within a motor vehicle. For example, the IHX 18 could be used in a vehicle with a front module only, or with other refrigerants such as carbon dioxide or ammonia. In another example, the IHX 18 could be used as part of a heat pump or short-cycle system to warm up or extract heat from the engine coolant, to produce heat for a passenger compartment of the motor vehicle. It could also be used to cool engine, transmission or transaxel fluids. Moreover, the IHX 18 could be used in applications beyond the context of motor vehicles, where heat exchange is necessary or desirable. For example, the IHX 18 could be used in the chemical process industry or anywhere an inexpensive heat exchanger is needed. As another example, the IHX 18 could be used in domestic water heaters for pools or spas based on refrigerant cycles, for instance, or in hot water space heating systems.

Claims

1. A tube-to-tube heat exchanger assembly especially for use in an air conditioning system of a motor vehicle, the assembly comprising

a unitary heat exchanger comprising a tube internally longitudinally divided into a first passage and a second passage by a primary web, the primary web being heat conductive;

a first pair of fluid lines; and

a second pair of fluid lines;

wherein one line of the first pair of fluid lines is directly connected to one end of the first passage and the other line of the first pair of fluid lines is directly connected to the other end of the first passage and one line of the second pair of fluid lines is directly connected to one end of the second passage and the other line of the second pair of fluid lines is directly connected to the other end of the second passage.

2. The assembly of claim 1, wherein the first pair of fluid lines are warm fluid supply lines and the second pair of fluid lines are cold fluid return lines.

3. The assembly of claim 1, wherein the primary web is substantially planar.

4. The assembly of claim 1, wherein the heat exchanger is an extrusion.

5. The assembly of claim 1, wherein the heat exchanger is made of aluminum.

6. The assembly of claim 1, wherein each of the first passage and the second passage, in end view, is substantially “D” shaped.

7. The assembly of claim 6, wherein an end of each of the warm fluid supply lines and the cold fluid return lines is substantially “D” shaped in end view.

8. The assembly of claim 1, wherein each of the first passage and the second passage, in end view, is substantially circular.

9. The assembly of claim 1, wherein each of the warm fluid supply lines and the cold fluid return lines is directly connected to the heat exchanger by brazing.

10. The assembly of claim 7, wherein the heat exchanger further comprises a longitudinal support web extending from the primary web to the tube.

11. The assembly of claim 10, wherein, in an end view, the primary web and the support web together appear substantially T-shaped.

12. The assembly of claim 11, wherein the primary web extends longitudinally substantially the entire length of the tube.

13. The assembly of claim 12, wherein the support web terminates a distance from each end of the tube to allow for insertion of the warm liquid supply lines or the cold vapor supply lines into the tube.

14. The assembly of claim 1, wherein the primary web, in end view, is substantially arc-shaped, with ends of the primary web terminating at positions on an inner circumference of the tube, thereby creating the first passage having a substantially crescent-shape and the second passage having a substantially circular shape.

15. The assembly of claim 14, wherein the heat exchanger further comprises a support web, being substantially planar, and in an end view, the support web extending from approximately mid-way along the primary web, away from the primary web, to the inner circumference of the tube.

16. The assembly of claim 15, wherein each line of the first pair of fluid lines, in an end view, is shaped to conform to the cross-section of the second passage, and each line of the second pair of fluid lines, in an end view, is shaped to conform to the cross-section of the first passage.

17. The assembly of claim 16, wherein the primary web extends substantially the entire length of the tube.

18. The assembly of claim 17, wherein the support web terminates a distance from each end of the heat exchanger to allow for insertion of the warm liquid supply lines or the cold vapor supply lines into the tube.