Abstract:
A heat exchanger for a motor vehicle air conditioning system is provided. The heat exchanger includes an inner tube through which a heat exchanger medium can flow and a flexible outer tube that at least regionally envelops the inner tube with the formation of a flow-through intermediate space. The inner tube exhibits a tubular section that enables a change in length and/or direction of the inner tube and runs inclined relative to the longitudinal direction of the outer tube.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims priority to German Patent Application No. 10 2011 100 692.7 filed May 6, 2011, which is incorporated herein by reference in its entirety 
       TECHNICAL AREA 
       [0002]    The technical field generally relates to a heat exchanger or heat transferring device for a motor vehicle air conditioning system, which can be flexibly adjusted to prescribed installation circumstances in the motor vehicle. 
       BACKGROUND 
       [0003]    Known in the art for increasing the performance and efficiency of motor vehicle air conditioning systems are air conditioner-internal heat exchangers, so-called internal heat exchangers (IHX). Internal heat exchangers 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 supplied to the expansion device on the high-pressure side of the refrigerant circuit. 
         [0004]    For example, DE 10 2005 052 972 A1 describes a two-walled heat exchanger tube with an outer tube and 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. 
         [0005]    The geometric dimensions and shapes of the tubes are of importance for optimizing the function of such heat exchangers in the refrigerant circuit. In an existing vehicle package, which offers no space for individually adapting or changing the outer contour or outer geometry of the heat exchanger, it is comparatively difficult to individually adjust such heat exchangers to prescribed requirements in terms of their heat exchanger capacity, for example specific to the vehicle type. 
         [0006]    In motor vehicle air conditioning systems, a compressor is usually situated on the motor side, while the evaporator of the air conditioning system fluidically connected thereto is arranged on the body side. In order to avoid any disturbing noises and vibrations, as well as to compensate for component and assembly tolerances, a length compensator is in most cases to be provided in the refrigerant circuit of the motor vehicle air conditioning system. 
         [0007]    For example,  FIG. 2  shows an internal heat exchanger  50  known from prior art, whose outlet  52  depicted therein on the left is coupled by means of a fitting  56  with a flexible length of tubing  60 , the other end of which is in turn connected by means of a fitting  58  with a rigid line section  62 . The heat exchanger  50  exhibits an essentially cylindrical outer tube  70 , which extends rigidly between two connection nozzles  64  and  66  for a high-pressure inlet  54  and a high-pressure outlet  68 . 
         [0008]    From the standpoint of assembly technology, the internal heat exchanger  50  is secured in the motor vehicle, for example via two connection nozzles  64 ,  66 . For purposes of vibration isolation or tolerance compensation, the flexible length of hose  60  is separately arranged and coupled, for example to a low-pressure line  52  of the heat exchanger  50 . 
         [0009]    By contrast, it is at least one object herein to provide an improved and simplified way of assembling an internal heat exchanger in the motor vehicle, which can be easily adjusted to prescribed, even diverse installation conditions. The heat exchanger can be adjusted for the direct substitution of existing heat exchanger configurations, and in particular with respect to prescribed or already existing terminals in the 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 
       [0010]    A heat exchanger is provided for a motor vehicle air conditioning system, and exhibits at least one inner tube through which a heat exchanger medium can flow and a flexibly designed outer tube. The outer tube at least regionally envelops the inner tube with the formation of at least one intermediate space through which the heat exchanger medium can flow. 
         [0011]    The inner tube and outer tube are here to be integrated into the air conditioner refrigerant circuit in such a way that the intermediate space between the outer tube and inner tube that can carry a flow from the outer tube flows opposite the direction of flow of the heat exchanger medium flowing through the inner tube. As a consequence, the heat exchanger operates according to the counter-flow principle. 
         [0012]    The inner tube further exhibits at least one tubular section running inclined relative to the longitudinal direction of the outer tube, thereby enabling a change in length and/or change in direction of the inner tube. In this regard, it is possible overall to provide a flexibly designed heat exchanger that can be individually adapted to prescribed installation conditions of the motor vehicle. While the outer tube is designed to be comparatively flexible and hence deformable, or even expandable within certain limits, through the use of a comparatively flexible outer tube material anyway, a comparatively rigid and inflexible tube material can, by contrast, continue to be used for the inner tube. 
         [0013]    Because at least parts of the tubular section of the inner tube run inclined relative to the longitudinal direction of the outer tube, the geometric configuration of the inner tube can be altered to provide a change in length and/or direction that is relatively easy to implement overall. For example, if several inner tube sections alternately run along opposing inclines viewed in the longitudinal direction of the tube, thereby yielding a zigzag progression viewed in the longitudinal direction, the inner tube can be extended, e.g., from outside, to alter the length of the inner tube, wherein the tube sections running inclined relative to the longitudinal direction only experience a slight directional change. For this reason, in an embodiment, the inner tube is configured as a dimensionally stable tube, but yet exhibits a basic geometric structure and shape making it possible to deform the inner tube at least once, thereby enabling its universal adjustment to prescribed and potentially varying installation circumstances on the motor vehicle. 
         [0014]    In another exemplary embodiment, regions of the inner tube exhibit a spiral and/or coiled configuration. Such a design permits the inner tube to elastically deform, e.g., comparably to a spiral spring, so that the heat exchanger along with its deformable inner tube and its already flexibly configured outer tube can be tailored to a wide variety of installation space requirements for the motor vehicle, and correspondingly variably integrated into the refrigerant circuit of the air conditioning system. 
         [0015]    From the standpoint of assembly technology, the heat exchanger can serve not only to decouple vibration, for example between the motor-side compressor and evaporator to be situated on the body side, but simultaneously assume the function of compensating for component and assembly tolerances. The need for a separate length or tolerance compensator, as shown on  FIG. 2 , can be eliminated. 
         [0016]    In another embodiment, several helically and/or spirally coiled and/or telescoping inner tubes are provided. The heat exchanger within its flexible outer tube exhibits at least two inner tubes, for example, symmetrically arranged relative to each other, but turned by 180° in terms of their spiral winding. 
         [0017]    Several spiral tubes each rotated relative to each other by a prescribed angle can also be provided, up to and including an arrangement in which an imaginary jacket surface of a helically coiled inner tube is completely filled with telescoping inner tubes. Such an inner tube configuration can exhibit up to eight or more inner tubes, and continues to permit an at least slight stretching of the heat exchanger, which is sufficient for purposes of the heat exchanger acting to balance out component or assembly tolerances. 
         [0018]    Another embodiment further provides that all inner tubes branch out of a shared inlet tube downstream from an inlet of the heat exchanger and/or empty into a shared outlet tube upstream from an outlet. In other words and viewed from the inner tube, the inner tubes branch out of a shared inlet tube upstream and/or empty into a shared outlet tube downstream. In this regard, the heat exchanger exhibits a single inlet or outlet tube for the heat exchanger medium flowing through the inner tubes for purposes of integration into the refrigerant circuit. Branching into several helically coiled inner tubes preferably takes place within a region of the heat exchanger jacketed by the outer tube. 
         [0019]    In addition, at least some of the inner tubes can spiral directly about each other in a mechanically unloaded basic position viewed in the longitudinal direction of the outer tube. Such an initial configuration makes it possible to dilate or stretch the inner tubes in such a way that, once they reach an extracted or elongated configuration, the individual telescoping spiral inner tubes come to be spaced apart from each other with the formation of flow-through intermediate spaces. At least several of the inner tubes can here be completely bathed in the heat exchanger medium. 
         [0020]    In an exemplary embodiment, the outer tube exhibits an essentially cylindrical geometry and that the inner tube with its coiled or helical axis is arranged parallel and/or overlapping relative to the longitudinal cylindrical axis of the outer tube. Such a concentric arrangement for an inner and outer tube forms an annular gap between the inner wall of the outer tube and the outer walls of the coiled inner tube. Of course, the heat exchanger medium can additionally also flow around or through the interior of the coiled inner tubes. 
         [0021]    In another embodiment, a connection nozzle furnished for securing the outer tube is interspersed in the radial direction by the inner tube on the outlet and/or inlet side. In particular, the intermediate space that can carry a flow between the outer tube and inner tube(s) can be coupled from the standpoint of fluid mechanics with an inlet or outlet tube extending in the longitudinal direction of the heat exchanger, while the respective coiled inner tube(s) are fluidically connected with an inlet or outlet extending outwardly in the radial direction. 
         [0022]    The inner tube is designed as a metal tube, in accordance with a further embodiment. Even though as a metal tube, the inner tube has an inherent dimensional stability, the material thickness and material type can be chosen with respect to a preselected deformability. The smallest possible flow-through inner tube diameter should also be selected so that the heat exchanger exhibits the required mechanical stability. For example, the heat exchanger can not only follow a straight line in the motor vehicle, but can be curved therein owing to its flexible inner and outer tube configuration. 
         [0023]    The inner tube(s) may also exhibit a flow-through inner diameter measuring in the range of from about 1 mm to about 3 mm, for example from about 1 mm to about 2 mm. The wall thickness of the inner tube(s) is less than about 1 mm. In this regard, the inner tubes are comparably thin and filigree in design, so as to enable a mechanical deformation of the entire heat exchanger, even without the assistance of forming tools. 
         [0024]    In a further embodiment, the outer tube is formed of an elastomer plastic or a synthetic or natural rubber material. In particular, the outer tube exhibits a flexibly deformable length of tubing, or consists of the latter. The outer tube can further be equipped with fiber reinforcement for reasons of stability. The axial length of the outer tube can also be greater by a prescribed amount than the axial extension of the inner tube in its base position, so as to facilitate a stretching or extraction of the heat exchanger. 
         [0025]    In another embodiment, the outer tube is a low-pressure line, and the inner tube or inner tubes are provided as high-pressure lines. As a consequence, predominantly a compressed liquid flows through the inner tube, and any branching heat exchanger tubes, while a predominantly gaseous refrigerant flows through the outer tube or the intermediate space formed between the outer tube and heat exchanger tubes. Alternatively, the outer tube can be a high-pressure line and that the inner tube can be a low-pressure line, and the outer and inner tubes are connected accordingly with the components of the refrigerant circuit from the standpoint of fluid mechanics. 
         [0026]    In a further embodiment, for a heat exchanger exhibiting a largely tubular and cylindrical outer contour, opposing end sections of the outer tube are situated downstream from an evaporator and upstream from a compressor in the refrigerant circuit of a motor vehicle air conditioning system. Accordingly, an arrangement upstream from an expansion device and downstream from a capacitor is provided in the refrigerant circuit of the air conditioning system for the opposing end sections of the inner tube or correspondingly branched heat exchanger tubes. It here generally holds true that the low-pressure line(s) is (are) designed for the fluidic coupling of the evaporator and compressor, while the high-pressure line(s) is (are) designed for the fluidic coupling of the capacitor and expansion device of the refrigerant circuit of the air conditioning system. 
         [0027]    A motor vehicle air conditioning system also is herein provided. The motor vehicle air conditioning system exhibits a refrigerant circuit with at least a compressor, a capacitor, an expansion device as well as an evaporator, which are serially fluidically connected with each other by means of corresponding lines of the refrigerant circuit, and coupled with each other from the standpoint of fluid mechanics in order to circulate the refrigerant. The refrigerant circuit here further exhibits a previously described, preferably tubular, flexible heat exchanger, which enables an exchange of heat between the low-pressure side lying downstream from the evaporator and the high-pressure side of the refrigerant circuit lying upstream from the expansion device. 
         [0028]    A motor vehicle having an air conditioning system is further herein provided. The air conditioning system exhibits a refrigerant circuit with at least a compressor, a capacitor, an expansion device as well as an evaporator, which are serially fluidically connected with each other by means of corresponding lines of the refrigerant circuit, and coupled with each other from the standpoint of fluid mechanics in order to circulate the refrigerant. The refrigerant circuit here further exhibits a previously described, preferably tubular, flexible heat exchanger, which enables an exchange of heat between the low-pressure side lying downstream from the evaporator and the high-pressure side of the refrigerant circuit lying upstream from the expansion device. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0029]    The various exemplary embodiments will hereinafter be described in conjunction with the following drawing figures, wherein like numerals denote like elements and wherein: 
           [0030]      FIG. 1  is a circuit diagram of a motor vehicle air conditioning system with internal heat exchanger in accordance with an exemplary embodiment; 
           [0031]      FIG. 2  is a heat exchanger arrangement according to prior art; 
           [0032]      FIG. 3  is a side view of a heat exchanger according to an exemplary embodiment; and 
           [0033]      FIG. 4  is a regional cross sectional view of the heat exchanger according to  FIG. 3 . 
       
    
    
     DETAILED DESCRIPTION 
       [0034]    The following detailed description is merely exemplary in nature and is not intended to limit the application and uses of the various embodiments. Furthermore, there is no intention to be bound by any theory presented in the preceding background or the following detailed description 
         [0035]    The motor vehicle air conditioning system  20  shown in  FIG. 1  exhibits a refrigerant circuit that couples the individual air conditioning components compressor  18 , capacitor  16 , internal heat exchanger  10 , expansion valve  12  and evaporator  14  with each other from the standpoint of fluid mechanics in a manner known in the art. The internal heat exchanger  10  is situated downstream from the capacitor  16  and upstream from the expansion valve on the high pressure side. The internal heat exchanger  10  is provided downstream from the evaporator  14  and upstream from the compressor  18  on the low pressure side. 
         [0036]    The high-temperature refrigerant exposed to a comparably high pressure is supercooled by the low-pressure and low-temperature refrigerant flowing in the opposite direction in the heat exchanger  10 , upstream from the expansion valve  12 . This internal heat exchange in the refrigerant circuit makes it possible to improve the efficiency of the motor vehicle air conditioning system  20 . 
         [0037]    The internal heat exchanger  10  is depicted in  FIGS. 3 and 4  in a curved configuration and in cross section. The heat exchanger  10  exhibits two connection nozzles  34 ,  35  coupled with each other from the standpoint of fluid mechanics by the flexible outer tube  30 . The connection nozzle  35  shown on the right of  FIG. 3  is fluidically connected with an inlet  40  extending in the longitudinal direction of the heat exchanger for the low-temperature refrigerant exposed to a comparably low pressure. By contrast, the other connection nozzle  34  shown on the left of  FIG. 3  is provided with an outlet  22  corresponding hereto for the low-temperature-low-pressure refrigerant. 
         [0038]    The connection nozzle  34  shown on the left of  FIG. 3  is provided with an inlet  42  for the refrigerant exposed to a high pressure that runs in the radial direction and protrudes into the connection nozzle  34 . A high-temperature-high-pressure outlet  44  also extends radially outward on the connection nozzle  35 , to which it corresponds. 
         [0039]    The cross section according to  FIG. 4  provides a more detailed view of the internal structure of the flexible heat exchanger  10  based on the connection nozzle  34  shown on the left of  FIG. 3 . The connection nozzle  34  empties into a low-temperature outlet tube  22 , which is fluidically connected with a suction side of the compressor  18 . 
         [0040]    The other end of the connection nozzle  34  exhibits an attachment flange  36  directed at least slightly radially outward, which serves as a mount for the flexible outer tube or outer hose  30 . The flexible tube  30  preferably made out of an elastomer material is crimped via the connection nozzle  34 , and there tightly fixed in place by means of attachment clamps or O rings  38 . 
         [0041]    In the area of the connection nozzle  34 , the high-pressure-high-temperature inlet  42  empties into a radially circumferential branching section  24 , in which the high-pressure inlet  42  branches into a plurality of individual heat exchanger inner tubes  28 . The branching section  24  here lies within the connection nozzle  34 . In the configuration depicted on  FIG. 4 , all helical or spiral heat exchanger inner tubes  28  directly adjoin each other in the axial direction  46 . 
         [0042]    Since the individual inner tubes  28  only exhibit an inner diameter in the range of from about 1 mm to about 3 mm, for example, from about 1 mm to about 2 mm, as well as a correspondingly small wall thickness, the inner tubes  28  can be reversibly mechanically deformed at least within prescribed regions, in particular extracted in an axial direction  46  and also curved or bent as shown on  FIG. 3 . 
         [0043]    The outlet side for the high-pressure-high-temperature refrigerant not explicitly depicted in the figures is designed as shown in  FIG. 4 . The spirally coiled inner tubes end up emptying into a trough region again, by means of which all inner tubes  28  of an spiral inner tube section  26  are coupled from the standpoint of fluid mechanics with a single high-pressure outlet  44  shown on the right of  FIG. 3 . The high-pressure line outlet  44  is provided upstream from the expansion valve  12 , and is connected from the standpoint of fluid mechanics with the inlet side of the expansion valve  12  while assembling the heat exchanger  10  in the air conditioner circuit. 
         [0044]      FIG. 4  further depicts the central longitudinal axis  48  of the heat exchanger  10 . The spirally coiled inner tube section  26  is preferably arranged centrally relative to the axis  48  of the heat exchanger  10  or the outer tube or outer hose  30 , so as to form as uniform an annular gap  32  as possible for the low-pressure-low-temperature refrigerant. 
         [0045]    The flexible and pliable configuration of the outer tube or outer hose  30  and the spirally coiled inner tube  28  enables a particularly easy universal geometric adjustment of the heat exchanger  10  to varying installation conditions of the motor vehicle. Depending on the configuration of the one, preferably the plurality of, inner tube(s)  28 , the geometric adjustment and concurrent deformation of the heat exchanger  10  can be performed during the assembly process in the air conditioner circuit. 
         [0046]    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 invention 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 invention as set forth in the appended claims and their legal equivalents.