Abstract:
A method for assembling a heat exchanger device of a refrigeration unit may include pushing a heat exchanger coil of the heat exchanger device over a refrigerant collecting vessel of the heat exchanger device. The method may also include fluidically connecting the heat exchanger coil to the at least one cover of the heat exchanger device. The method may further include pushing a tubular casing of the heat exchanger device over the heat exchanger coil, and deforming the tubular casing radially inward.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims priority to German Patent Application No. DE 10 2014 220 403.8, filed on Oct. 8, 2014, and International Patent Application No. PCT/EP2015/073023, filed on Oct. 6, 2015, both of which are hereby incorporated by reference in their entirety. 
     
    
     TECHNICAL FIELD 
       [0002]    The invention relates to a method for assembling a heat exchanger device of a refrigeration unit. Furthermore, the invention relates to a heat exchanger device which is produced according to said method. 
       BACKGROUND 
       [0003]    Heat exchanger devices of this type are used in refrigeration units, in particular in refrigeration units of an air conditioning system, for example a vehicle air conditioning system. By way of the use of said heat exchanger devices, the degree of efficiency of the refrigeration unit can be improved, in particular if CO 2  (R744) is used as refrigerant. By way of the heat exchanger device, the low temperature level of the low pressure region of the refrigeration circuit can be utilized, in order to further cool the warmer refrigerant in the high pressure region immediately downstream of the gas cooler. Here, the heat exchanger device can be combined with a refrigerant collecting vessel (accumulator). The integration of a heat exchanger coil with the refrigerant collecting vessel in one component is very complex and expensive, however. 
         [0004]    DE 10 2006 031 197 A1 has disclosed an inner heat exchanger with an accumulator for refrigerant circuits, in particular in motor vehicle air conditioning systems, comprising a housing made from a pressurized tubular cylinder casing and a cover plate and a base plate, an accumulator which is made from a material which conducts heat poorly, preferably made from plastic, and is arranged so as to form a gap concentrically in the housing, for the liquid refrigerant at low pressure, and a finned tube for the refrigerant at high pressure, which finned tube is arranged in a helical manner in the gap between the accumulator and the cylinder casing. The cover plate and the base plate in each case have a connector plate with connectors for refrigerant lines, a U-shaped extraction tube with a vapor inlet and a vapor outlet for the refrigerant vapor being provided in the accumulator, and a baffle apparatus for separating the liquid and gaseous phase of the refrigerant being provided in the upper region of the accumulator. Here, the vapor inlet is arranged below the baffle apparatus in the accumulator in a manner which is protected against refrigerant liquid, and the vapor outlet is arranged outside the accumulator. The finned tube in turn is incorporated sealingly at its ends via a thread into the cover plate and the base plate, as a result of which an inner heat exchanger with an accumulator is to be provided, which heat exchanger can be produced cost-efficiently. 
       SUMMARY 
       [0005]    The invention is based on the object of providing a heat exchanger device which combines an inner heat exchanger with a refrigerant collecting vessel and the assembly of which is simplified. 
         [0006]    According to the invention, said object is achieved by way of the features of the independent claims. Advantageous embodiments are the subject matter of the dependent claims. 
         [0007]    The invention is based on the general concept of mounting a housing of the heat exchanger device as last component, as a result of which the mounting of the heat exchanger coil and the refrigerant collecting vessel becomes simpler. Here, the heat exchanger coil is pushed over the refrigerant collecting vessel and is connected fluidically to the at least one cover, the tubular casing is pushed over the heat exchanger coil, and the tubular casing is deformed radially inward. As a result, the assembly and the connection between the at least one cover and the heat exchanger coil are simple, since the tubular casing of the housing does not block the access to the heat exchanger coil. Therefore, the selection of the connection between the heat exchanger coil and the at least one cover is not restricted. Furthermore, the connection of the refrigerant collecting vessel to the at least one cover and to the heat exchanger coil is simplified correspondingly. 
         [0008]    It is favorable if the housing of the heat exchanger device has two covers, the heat exchanger coil is pushed over the refrigerant collecting vessel and is connected fluidically to the two covers, the tubular casing is pushed over at least one of the two covers and the heat exchanger coil, and, thereupon, the tubular casing is deformed radially inward. The flow paths in the heat exchanger device can be simplified as a result of the use of two covers. After the assembly of the heat exchanger coil and the refrigerant collecting vessel with the two covers, the tubular casing is then pushed over at least one of the two covers and is deformed radially inward. As a result, although the casing has to fit over at least one of the two covers, it can nevertheless have a functional smaller diameter after it has been deformed radially inward. Therefore, according to the invention, the assembly of the heat exchanger device can be improved without impairing the function of the heat exchanger device. 
         [0009]    One advantageous solution provides that the tubular casing is deformed radially inward in such a way that it bears against the heat exchanger coil. By virtue of the fact that the tubular casing bears against the heat exchanger coil, a helical sealing face is formed which delimits a fluid duct which is, in particular, helical between the refrigerant collecting vessel and the tubular casing. Here, the helical fluid duct extends the dwell time in the heat exchanger device and improves the heat exchange as a result. 
         [0010]    A further advantageous solution provides that the tubular casing is deformed radially inward hydraulically or pneumatically. In particular, a hydraulic or pneumatic deformation process brings about a homogeneous input of force into the tubular casing and therefore a homogeneous deformation process. A deformation process of this type can be applied in a flexible manner to different components, as a result of which tool costs can be reduced. 
         [0011]    One particularly advantageous solution provides that the tubular casing is deformed radially inward by means of a forming tool. The deformation can be controlled precisely as a result of the use of a forming tool for deforming the tubular casing. In particular, it can be ensured in this way in an improved manner that the tubular casing bears against the heat exchanger coil without damaging the latter. 
         [0012]    One advantageous possibility provides that the tubular casing is deformed radially inward to a more pronounced extent in the region of the heat exchanger coil than in the region of the cover. In this way, the advantages of the solution according to the invention can be utilized in a particularly favorable manner. 
         [0013]    Another advantageous possibility provides that the tubular casing is deformed radially inward to a more pronounced extent in the region of the heat exchanger coil than in the region of the at least one cover. In this way, the advantages of the solution according to the invention can be utilized in a particularly favorable manner. 
         [0014]    A further advantageous possibility provides that, before the tubular casing is pushed on, the refrigerant collecting vessel is connected to the two covers. As a result, the advantages according to the invention can also be utilized in the connection of the refrigerant collecting vessel to the two covers. 
         [0015]    One favorable alternative provides that, before the deforming of the tubular casing, the latter is connected at least sealingly to the at least one cover. In this way, the cover and the tubular casing can form a fluid-tight housing. Furthermore, any type of connection can be used between the cover and the tubular casing. 
         [0016]    Another favorable alternative provides that, before the deforming of the tubular casing, it is connected at least sealingly to both covers. In this way, the two covers and the tubular casing can form a fluid-tight housing. Furthermore, any type of connection can be used between the two covers and the tubular casing. 
         [0017]    One advantageous alternative provides that the tubular casing is connected at least sealingly to the at least one cover by way of the deforming of the tubular casing. As a result, the tubular casing and the at least one cover form a fluid-tight housing, without it being necessary to provide further connecting means. 
         [0018]    A further favorable alternative provides that the tubular casing is connected at least sealingly to both covers by way of the deforming of the tubular casing. As a result, the tubular casing and the two covers form a fluid-tight housing, without it being necessary to provide further connecting means. 
         [0019]    Furthermore, according to the invention, the object is achieved by way of a heat exchanger device of a refrigeration unit having a housing which has at least one cover and a tubular casing, having a heat exchanger coil and having a refrigerant collecting vessel, the tubular casing being connected to the at least one cover, and the tubular casing being tapered at least on one side in a region between two ends of the tubular casing. This refinement makes it possible that the heat exchanger device is assembled in accordance with the preceding method, with the result that the advantages of the above-described method likewise extend to the heat exchanger device. 
         [0020]    In the description and the appended claims, “to be tapered in a region” is understood to mean that the object has a smaller diameter, in particular internal diameter, in this region than in any other region of the object. 
         [0021]    One advantageous variant provides that an internal diameter of the tubular casing is smaller in a region between two axial ends of the tubular casing than an internal diameter of the tubular casing at at least one of the two axial ends of the tubular casing. This refinement also makes it possible that the heat exchanger device is assembled in accordance with the preceding method, with the result that the advantages of the above-described method likewise extend to the heat exchanger device. 
         [0022]    Furthermore, it is favorable if the housing of the heat exchanger device has two covers, if the tubular casing is connected to the two covers, and if the tubular casing is tapered at least on one side in a region between the two covers. This refinement makes it possible that a heat exchanger device having two covers is assembled in accordance with the preceding method, with the result that the advantages of the above-described method likewise extend to the heat exchanger device. 
         [0023]    Furthermore, the abovementioned refinement of the heat exchanger device makes virtually any desired type of connection possible between the tubular casing and the two covers, since the connecting point is easily accessible. 
         [0024]    A further advantageous variant provides that the internal diameter of the tubular casing is smaller in a region between two axial ends of the tubular casing than the internal diameter of the tubular casing at both axial ends of the tubular casing. This refinement also makes it possible that a heat exchanger device having two covers is assembled in accordance with the preceding method, with the result that the advantages of the above-described method likewise extend to the heat exchanger device. 
         [0025]    One favorable solution provides that the tubular casing is in contact with at least one of the two covers or with the at least one cover exclusively by way of an inner side of the tubular casing. In this way, firstly the corresponding cover can be of simpler configuration. Secondly, the outer side of the tubular casing can be configured independently of restrictions as a result of the connecting capability to the cover. Therefore, costs can be spared. 
         [0026]    One particularly favorable possibility provides that a refrigerant or a heat exchanger fluid is conducted through the heat exchanger coils, in particular under high pressure, and that the heat exchanger coil surrounds the refrigerant collecting vessel in a helical manner at least in sections. As a result, a second fluid passage which is different than the fluid passage within the heat exchanger coil is formed. In particular, said fluid passage is formed between the refrigerant collecting vessel and the tubular casing. On account of the helical course of the heat exchanger coil, said fluid passage likewise has a helical course, with the result that the heat exchanger coil and said fluid passage are guided on one another within the heat exchanger unit for a comparatively long distance. As a result, heat can be exchanged in a particularly satisfactory manner between the fluid which flows in the heat exchanger coil and fluid which flows in the fluid passage. 
         [0027]    One favorable possibility provides that the at least one cover or both covers has/have an external diameter which is greater than an internal diameter of the tubular casing in a region between axial ends of the tubular casing. As a result, the two covers have a great cross-sectional area which can be used to attach refrigerant inlets and outlets and/or fastening means. 
         [0028]    One particularly advantageous alternative provides that at least one of the two covers has an external diameter which is smaller than an internal diameter of the tubular casing before the deformation of the latter. As a result, the tubular casing can be pushed over said cover, with the result that it is made possible to first of all connect the heat exchanger coil, the refrigerant collecting vessel and the two covers to one another and subsequently to push on the tubular casing and to connect it to the remaining components. 
         [0029]    It is particularly advantageous if the heat exchanger device has been assembled in accordance with the above-described method. The advantages of the method are therefore transferred to the heat exchanger device, reference being made to this extent to the above description of said method. 
         [0030]    Further important features and advantages of the invention result from the subclaims, from the drawings and from the associated description of the figures using the drawings. 
         [0031]    It goes without saying that the features which are mentioned above and are still to be described in the following text can be used not only in the respectively specified combination, but rather also in other combinations or on their own, without departing from the scope of the present invention. 
         [0032]    Preferred exemplary embodiments of the invention are shown in the drawings and will be explained in greater detail in the following description, identical designations relating to identical or similar or functionally identical components. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0033]    In the drawings, in each case diagrammatically: 
           [0034]      FIG. 1  shows an outline sketch of a refrigeration unit, 
           [0035]      FIG. 2  shows a sectional illustration through a heat exchanger device during assembly and before a tubular casing is pushed on, 
           [0036]      FIG. 3  shows a sectional illustration of the heat exchanger device from  FIG. 2 , with the tubular casing which has been pushed on, 
           [0037]      FIG. 4  shows a sectional illustration of the heat exchanger device from  FIG. 3  after a deformation of the tubular casing, 
           [0038]      FIG. 5  shows a sectional illustration of the heat exchanger device with arrows for identifying the refrigerant flow, 
           [0039]      FIG. 6  shows a perspective view of a heat exchanger coil, 
           [0040]      FIG. 7  shows an illustration of two possible cross sections of a tube of the heat exchanger coil, and 
           [0041]      FIG. 8  shows an illustration of two further possible cross sections of a tube of the heat exchanger coil. 
       
    
    
     DETAILED DESCRIPTION 
       [0042]    A refrigeration unit  10  which is shown diagrammatically in  FIG. 1  comprises a compressor  12 , a gas cooler  14 , a heat exchanger device  16 , a throttle or an expansion valve  18 , and an evaporator  20 . Here, the refrigeration unit  10  operates on the known principle of the refrigeration circuit. A refrigerant  22  passes through a circuit  28  which is driven by the compressor  12 . First of all, the refrigerant  22  is compressed in the compressor  12 , as a result of which the temperature of the refrigerant  22  is increased. From the compressor  12 , the refrigerant  22  is guided into the gas cooler  14 , where it can dissipate heat to the surroundings on account of the increased temperature as a result of the compression. From the gas cooler  14 , the refrigerant  22  is guided via an inner heat exchanger  30  to the throttle/expansion valve  18  which throttles or regulates the flow of the refrigerant  22  and separates a low pressure region  24  from a high pressure region  26 . Downstream of the throttle/expansion valve  18 , the refrigerant  22  flows into the evaporator  20 , in which it expands and is cooled in the process. By virtue of the fact that the refrigerant  22  can output heat to the surroundings in the high pressure region  26 , the temperature of the refrigerant  22  is lower in the evaporator  20  than it was upon entry of the refrigerant  22  into the compressor  12 . The evaporator  20  has a second flow path for a medium to be cooled, such as air, with the result that the refrigeration unit  10  can absorb heat from the medium to be cooled. A refrigerant collecting vessel  32  is arranged downstream of the evaporator  20 , from which refrigerant collecting vessel  32  the refrigerant  22  is guided via the inner heat exchanger  30  to the compressor  12 . The refrigeration unit  10  is used, for example, in air conditioning systems of motor vehicles. 
         [0043]    On account of its lower greenhouse activity in comparison with other refrigerants, CO 2  (R744) is used as refrigerant  22 . In particular, if CO 2  is used as refrigerant  22 , the use of the inner heat exchanger  30  is favorable for the degree of efficiency of the refrigeration unit  10 . Via the inner heat exchanger  30 , heat from the refrigerant  22  in the high pressure region  26 , in particular downstream of the gas cooler  14 , is transferred to the refrigerant  22  in the low pressure region  24 , in particular downstream of the throttle/expansion valve  18 . As a result, the temperature of the refrigerant  22  can be reduced still further at the throttle/expansion valve  18 , with the result that the degree of efficiency of the refrigeration unit  10  is improved. 
         [0044]    To this end, the refrigeration unit  10  has the heat exchanger device  16  according to the invention which comprises the inner heat exchanger  30  and the refrigerant collecting vessel  32 . Both are arranged in a housing  34  which has at least one, for example two, covers  36  and a tubular casing  38 . Two fluid ducts run within the housing  34 . A first fluid duct  40  is formed by the inner heat exchanger  30 , in particular by a heat exchanger coil  42  of the inner heat exchanger  30 . A second fluid duct  44  extends within the housing  34  and in the process runs through the refrigerant collecting vessel  32  and through a region between the refrigerant collecting vessel  32  and the tubular casing  38 . The heat exchanger coil  42  of the inner heat exchanger  30  also runs in said region (cf.  FIGS. 4, 5 ). 
         [0045]    The two fluid ducts  40 ,  44  are connected in such a way that the two fluid ducts  40 ,  44  are flowed through in counterflow in the region between the refrigerant collecting vessel  32  and the tubular casing  38 , and the heat can thus be transmitted particularly effectively from the one fluid duct to the other fluid duct. 
         [0046]    For example, the first fluid duct  40  and therefore the heat exchanger coil  42  are flowed through by refrigerant  22  from the high-pressure region  26  in a manner which comes from the gas cooler  14 , whereas the second fluid duct  44  is flowed through by refrigerant  22  from the low pressure region  24  in a manner which comes from the evaporator  20  or the refrigerant collecting vessel  32 . The heat of the refrigerant  22  from the high pressure region  26  can thus dissipate to the refrigerant  22  on the low pressure side. 
         [0047]    The heat exchanger coil  42  runs in a helical manner at least in sections through the housing  34  of the heat exchanger device  16 . In particular, the heat exchanger coil  42  runs in a helical manner in a cylindrical casing-shaped region between the refrigerant collecting vessel  32  and the tubular casing  38 . The heat exchanger coil  42  preferably bears against the tubular casing  38 , with the result that a helical sealing face is produced between the heat exchanger coil  42  and the tubular casing  38 . 
         [0048]    As a result, the heat exchanger coil  42  surrounds the refrigerant collecting vessel  32 . Here, the heat exchanger coil  42  can likewise bear against the refrigerant collecting vessel  32 , with the result that the second fluid duct  44  extends in a helical manner between the refrigerant collecting vessel  32  and the tubular casing  38  and thus has a great length and the refrigerant  22  has a comparatively great amount of time to absorb heat from the heat exchanger coil  42 . As an alternative, there can be a spacing between the heat exchanger coil  42  and the refrigerant collecting vessel  32 . As a result, the second fluid duct  44  is not of helical configuration in the region between the refrigerant collecting vessel  32  and the tubular casing  38 , but the heat exchanger coil  42  produces a finned or corrugated surface, with the result that the fluid  22 , when it flows through the second fluid duct  44 , is swirled and can absorb heat from the heat exchanger coil  42  effectively as a result. This second variant has a lower flow resistance than the first variant. However, the thermal coupling between the second fluid duct  44  and the first fluid duct  40  is correspondingly lower. The possibility is offered to adapt the heat coupling and flow resistance to the respective requirements in an optimum manner. 
         [0049]    The heat exchanger coil  42  is connected to refrigerant connectors in the covers  36 , with the result that the refrigerant  22  can be guided through the heat exchanger coil  42  by way of the refrigerant connectors in the covers  36 . 
         [0050]    As shown, for example, in  FIGS. 6, 7 and 8 , the heat exchanger coil  42  can have various cross sections; in particular, the heat exchanger coil  42  can have circular, oval or elliptic cross sections. As an alternative or in addition to this, the heat exchanger coil  42  can also have a relatively flat profile with a plurality of relatively small individual ducts  50  within the heat exchanger coil  42 . 
         [0051]    The refrigerant collecting vessel  32  serves to catch and collect gaseous or liquid refrigerant  22  from the refrigerant gas flow and therefore to form a type of cooling reservoir. To this end, the refrigerant collecting vessel  32  has a cylindrical main body, through which the refrigerant  22  is introduced approximately axially in a manner which comes from the evaporator  20 . A further opening is situated on the same side, through which further opening the gaseous refrigerant  22  can flow out of the refrigerant collecting vessel  32  again. As a result, the refrigerant  22 , after flowing into the refrigerant collecting vessel  32 , has to pass through an arc, by way of which liquid or solid parts of the refrigerant  22  are deposited. 
         [0052]    Accordingly, the refrigerant collecting vessel  32  is connected to at least one of the covers  36 , with the result that refrigerant  22  can flow in through a refrigerant inlet in the refrigerant collecting vessel  32 . 
         [0053]    The mounting of the refrigerant collecting vessel  32  and the heat exchanger coil  42  onto the covers  36  would be made more difficult if the tubular casing  38  were already connected to one of the covers  36 . For this reason, the tubular casing  38  is configured in such a way that it can be mounted as last part of the heat exchanger device  16 . 
         [0054]    As a result, the connection between the covers  36  and the refrigerant collecting vessel  32  and the connection between the covers  36  and the heat exchanger coil  42  can be carried out in a very simple manner, with the result that connecting possibilities which are favorable and/or particularly advantageous in some other way can also be applied. In particular, there is no restriction with regard to the connection type between the covers  36  and the heat exchanger coil  42  and the refrigerant collecting vessel  32 . 
         [0055]    The tubular casing  38  first of all has an internal diameter  46  which is greater than an external diameter  48  of the covers  36  (cf.  FIG. 3 ). As a result, the tubular casing  38  can be pushed over the two covers  36 . It is sufficient here if the tubular casing  38  can be pushed merely over one of the two covers  36 . As a consequence, one of the two covers  36  can have an external diameter  48  which is greater than the internal diameter  46  of the tubular casing  38 . 
         [0056]    An alternative or an addition to this is a configuration of the heat exchanger device  16  with only one cover which has all necessary refrigerant connectors, and a tubular casing  38  which is closed on one side. It is sufficient here if the internal diameter  46  of the tubular casing  38  is greater than an external diameter of the heat exchanger coil  42 , with the result that the tubular casing  38  can be pushed over the heat exchanger coil  42  and onto the cover  36 . 
         [0057]    Since the tubular casing  38  is to be in contact with the heat exchanger coil  42 , the tubular casing  38  is deformed radially inward (cf.  FIG. 4 ) after being pushed onto the heat exchanger device  16 . By way of said radial deformation process, the tubular casing  38  can also be connected in a fluid-tight manner to the covers  36 . As an alternative, the tubular casing  38  can also be connected to the covers  36  before the radial deformation operation. 
         [0058]    The radial deformation of the tubular casing  38  can be achieved, for example, by way of hydraulic or pneumatic pressure which is applied to the tubular casing  38  from the outside. As an alternative or in addition to this, the radial deformation of the tubular casing  38  can be carried out by way of a forming tool. 
         [0059]    As a result of this sequence of assembly, the connection of the covers  36  to the heat exchanger coil  42  and the refrigerant collecting vessel  32  is not disrupted by the tubular casing  38  and the assembly of the heat exchanger device  16  is considerably facilitated. 
         [0060]    After the radial deforming of the tubular casing  38 , the internal diameter  46  of the tubular casing  38  is reduced in a region  45  between two axial ends  47  of the tubular casing  38 . As a result, the tubular casing  38  can bear against the heat exchanger coil  42 . The diameter  48  of the at least one cover  36  is greater than the diameter of the heat exchanger coil  42 . As a consequence, the internal diameter  46  of the tubular casing  38  is greater at the axial ends  47  than in the region  45  between the axial ends  47 .