Abstract:
The present invention relates to a condenser for a domestic refrigerator having channelling which provides for the passage of a refrigerant associated with a substantially flat metal surface suitable for ensuring heat exchange between the refrigerant and air. The condenser comprises two plates configured to face each other, at least one of the plates being provided with a shaped groove configured to provide channelling which provides passage for the refrigerant.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The present invention concerns a condenser for domestic refrigerator cabinets, of the type comprising channelling for the passage of a refrigerant associated with a substantially flat metal surface in order to increase the heat exchange between the refrigerant and the air. As used herein, the term “refrigerator cabinet” refers to any type of domestic refrigerator or freezer.  
           [0003]    2. Description of the Related Art  
           [0004]    The static condensers used today in domestic refrigeration are essentially of two types: plate-type and wire-type. The first type is that referred to at the start of the description. Both types have the drawback of having a primary surface (tube) and a secondary surface (plate or wires) that are joined to the primary one by stapling or welding (therefore contact is made at only a few points, with a consequent loss of temperature and hence efficiency).  
           [0005]    Furthermore, recent experiments made by Applicants on condensers have surprisingly demonstrated the great importance of mass in this type of heat exchanger.  
           [0006]    The aim of the present invention is therefore that of providing a condenser that does not have the aforementioned drawbacks, for which a substantial energy saving can be guaranteed, while remaining simple and economic to produce.  
         SUMMARY OF THE INVENTION  
         [0007]    According to the invention, this aim is achieved by the fact that the condenser comprises two metal plates facing each other and joined together by welding or brazing, at least one of said plates being provided with a shaped groove capable of constituting said channelling for the passage of the refrigerant.  
           [0008]    Because of these characteristics it is possible to improve optimal heat exchange between the hot refrigerant and the material constituting the plate. Furthermore, with the solution according to the invention it is possible to use a plate of greater thickness, and there is no need to ensure good shaping of the plate in the area of the tubes (as required by current plate-type condensers). In fact, the plate condensers used nowadays have a thickness of 0.3-0.4 mm, whereas in the solution according to the invention the condenser is formed by two plates of a thickness preferably comprised between about 0.2 mm and about 0.5 mm, more preferably between about 0.3 mm and about 0.4 mm, brazed or welded together, for which the total thickness is preferably comprised between about 0.6 mm and about 0.8 mm.  
           [0009]    One of the advantages of the solution according to the invention is that the solution improves efficiency through better contact. The primary surface (tube) and the secondary surface (plate) of traditional plate condensers are all the same in that they are two plates, a smooth flat one and a flat one with funnelled channelling in the form of grooves brazed or welded together, with contact over the whole surface except in the area of the shaped grooves.  
           [0010]    Additionally, the solution improves efficiency because of the closeness of the channels. Current condensers have an inter-tube pitch of 50-60 mm. This distance was once considered to be optimal, as a fair compromise between cost and performance. In the solution according to the invention (the channelling being produced by pressing), the number of channellings does not alter the cost of the component by which it can be produced so as to optimise performance. An inter-channel pitch of between about 20 and about 50 mm, preferably between about 30 and about 40 mm, has improved efficiency of exchange, particularly with a horizontal lying position of the parallel rectilinear portions of the conduits (connected by curvilinear portions for the production of the coil), with reference to the usage configuration of the condenser arranged on an outer wall of the refrigerator cabinet.  
           [0011]    Another advantage of the solution is improved efficiency through greater mass of the condenser. As stated above, current plate-type condensers typically have a thickness of 0.3-0.4 mm, which is a limit for this type of technology. With the solution according to the invention it is possible also to have thicknesses of about 0.8 mm and therefore double the weight (for the same surface area). On the basis of tests carried out, a thickness of between about 0.6 mm and about 0.8 mm proves to be more optimal.  
           [0012]    Another advantage is the possibility of providing L-shaped side folds in the plate, in order to obtain the desired dimension of the “chimney”, and of having prepositioning, for fixing to the product without using other components (as is necessary in some plate-type solutions and for the wire-type version). The term “chimney” refers here to the portion of space comprised between the condenser and the rear wall of the refrigerator cabinet, suitable for directing the hot air upwards by convective motion.  
           [0013]    On the basis of the tests carried out, the applicant has found that, in order to improve efficiency further, the solution according to the invention requires a section of the channelling preferably comprised between about 6 mm 2  and about 14 mm 2 , more preferably comprised between about 8 mm 2  and about 12 mm 2 .  
           [0014]    According to another characteristic of the invention, the condenser can advantageously be provided with finning between the channelling, which permits better circulation of air between the two sides of the condenser. The optimal height of the fins is comprised between about 3 mm and about 12 mm, preferably between about 5 mm and about 10 mm.  
           [0015]    In another embodiment of the invention it is possible to braze in a furnace, together with the two plates, also the two tubes for connection to the remainder of the circuit (compressor and filter). This will make it possible to have better quality (elimination of two welds) and lower cost of the condenser. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0016]    Further advantages and characteristics of a condenser according to the present invention will become apparent from the following detailed description, provided purely by way of non-exhaustive example, with reference to the attached drawings in which:  
         [0017]    [0017]FIG. 1 is a view of the condenser in one configuration thereof installed on a domestic refrigerator;  
         [0018]    [0018]FIG. 2 is a side view of the condenser in FIG. 1;  
         [0019]    [0019]FIG. 3 is a detail from FIG. 1, which illustrates the finning of the condenser;  
         [0020]    [0020]FIG. 4 is a view in section along the line IV-IV in FIG. 3, on a larger scale; and  
         [0021]    [0021]FIG. 5 is a view in section, along the line V-V, in FIG. 3. 
     
    
     DETAILED DESCRIPTION  
       [0022]    With reference to the drawings, the reference numeral  10  illustrates a domestic refrigerator provided, on a rear wall thereof  10   a , with a condenser  12  configured to receive hot refrigerant coming from a compressor C, of liquefying it gradually and of sending it, cooled, to an evaporator (not illustrated) of the refrigerant circuit. The condenser  12  is constituted by two metal plates  12   a  and  12   b  made of iron or steel (FIGS. 4 and 5) brazed together in a furnace (for example, using a copper-based brazing alloy) and each having a thickness of about 0.4 mm. One of the two plates, in the example illustrated in the drawing the plate  12   b , has a shaped groove  14  made for example by pressing, which covers substantially the whole flat surface of the condenser along a coiled path. In particular, downstream from the compressor C the refrigerant enters the bottom of the channelling defined by the groove  14  and flows, horizontally and back and forth, over the flat surface of the condenser until it reaches the top. From there, through a vertical groove  14 ′, it is directed towards the lower portion of the condenser, from where it is then sent subsequently to the evaporator.  
         [0023]    The vertical distance H between two parallel lengths of the groove is, in the example illustrated, comprised between about 30 mm and about 40 mm. The condenser  12  has at the side two L-shaped folded edges 12 c  that are capable of defining both the portions for joining (for example by screwing) to the rear wall  10   a  of the refrigerator  10  and, together with said wall, a channel F generally known as a “chimney” suitably inclined and suitable for favouring the circulation of air by convective motion in relation to the condenser  12 .  
         [0024]    In order to increase heat exchange, the surfaces of the condenser comprised between the parallel rectilinear lengths of the groove  14  are provided with fins  16  made by partial cutting of the plates  12   a  and  12   b  and subsequent bending (FIGS. 3 and 4). Tests carried out by the Applicants have demonstrated that the optimal height H′ of the fins is comprised between about 5 mm and about 10 mm, with a length of between about 20 mm and about 40 mm, although this latter characteristic is not particularly critical and is dictated by the exigencies of practical production of the fins.  
         [0025]    The groove  14  of the condenser  12  has an optimal section of passage of between about 8 mm 2  and about 12 mm 2 , with a depth of between about 2.1 mm and about 3.2 mm, a main radius R (FIG. 5) of between about 1.5 mm and about 2 mm and a secondary radius R′ (for connection to the flat plate  12   a  of the condenser) of between about 0.5 mm and about 1 mm.  
         [0026]    In relation to the connections to the compressor C and to the remainder of the refrigerant circuit, the condenser  12  may be provided with small connecting tubes  18  joined to the condenser itself during the process of brazing or welding the two plates  12   a  and  12   b.    
       EXAMPLE  
       [0027]    Tests have been carried out on a prototype condenser as described and illustrated, with a 10 mm 2  section of channelling and a pitch between the horizontal lengths of channelling equal to 35 mm. The condenser was installed on the Whirlpool RE 160 AUT model refrigerator produced by the applicant, from which the traditional type of plate condenser was removed for preventive reasons. The tests were repeated, in identical conditions, on a commercial Whirlpool refrigerator of the same model. The tests gave the following results:  
                                                                 Traditional               condenser   Condenser of the invention                                    Compartment temp.    +5° C.    +5° C.       Condenser temp    43.8° C.    40.6° C.       Consumption (Wh/24 h)   558   539       Variation (%)       (−3.4%)                  
 
         [0028]    Therefore, for the same temperature inside the refrigerator, there was a 3.4% lower consumption, thanks to a lowering of the condensation temperature by 3.2° C. obtained with the condenser according to the invention.  
         [0029]    Naturally, variants of the condenser according to the invention are possible. For example, the groove can be produced on both the plates so that the channelling is made in the space between the grooves facing each other; in this configuration the channelling has a substantially circular cross-section. Furthermore, the material of the plates can also vary, although the choice of iron or steel has a more advantageous effect both in terms of energy efficiency and in terms of reduced costs.