Patent Publication Number: US-6662858-B2

Title: Counter flow heat exchanger with integrated fins and tubes

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a heat exchanger, particularly to a heat exchanger having a novel design of fins and tubes. 
     2. Description of Related Art 
     A conventional plate type heat exchanger comprises a plurality of fins linked with tubes. The tubes are connected to a fluid pumping unit, e.g., a attach block, a compressor or a pump. In case of the attach block being associated with a heat source, fluid inside the tubes absorb heat generated by the heat source via the attach block and the heat can be dissipated by the fins. After this, the fluid again receives heat to perform another cycle of heat exchange repeatedly. Conventional fins are made with equipment entirely different from that for making the tubes so that it results in high expenses for the equipments and molding tools. Assembling various shapes and sizes of fins with the tubes is not readily done and working hours for the assembly job are higher so that manufacturing cost increase relatively. Conventionally, fins and tubes are joined by way of pressing or brazing. But, the pressed joints may result in high thermal resistance with low efficiency of heat transfer and the brazed joints may become crystallized to result in lower efficiency of heat transfer. Furthermore, the conventional plate type heat exchanger provides a fan to blow fresh air towards the fins and the tubes for accelerating heat dissipation. Ordinarily, air flow outside the tubes and fluid flow inside the tubes run across each other forming cross flows so that it occurs a phenomenon of temperature gradient between hot fluid at cross section of the inlet and the cool fluid at cross section of the outlet in the heat exchanger. Therefore, the tube has to be coiled multiply to ensure uniform temperature distributions. This, however, causes increased pressure loss within the system and thus reduced the efficiency of heat exchange, while the phenomenon of temperature gradient is still not completely eliminated. Therefore, when the heat exchanger is used in conjunction with an air conditioning system, the refrigerant flowing inside the tubes and air blown outside lead to the cool air out of the discharge port thereof with a non-uniform temperature distribution and it will result in a problem of unsatisfactory temperature sensitivity. 
     SUMMARY OF THE INVENTION 
     It is the main object of the present invention to provide a heat exchanger with integrated fins and tubes, which can eliminate thermal contact resistance occurring at the conventional joining points of the fins and tubes and enhance the efficiency of thermal conductivity. 
     Another object of the present invention is to provide a heat exchanger having integrated fins and tubes, with which working hours and equipment expense are reduced and it is possible to adapt to size changes of products for lowering the manufacturing cost. 
     A further object of the present invention is to provide a heat exchanger in which internal fluid and external air are arranged to counter flow to each other so that the efficiency of heat exchange can be enhanced and the phenomenon of temperature gradient can be eliminated to enhance the sensitivity of comfortable temperature. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention can be more fully understood by reference to the following description and accompanying drawings, in which: 
     FIG. 1 is a perspective view of a base plate of the present invention in the first embodiment thereof; 
     FIG. 2 is a perspective view of an external plate of the present invention in the first embodiment thereof; 
     FIG. 3 is a sectional view illustrating the plates shown in FIGS. 1 and 2 being assembled; 
     FIG. 4 is a sectional view illustrating the base plate shown in FIG. 1 being joined to a flat plate; 
     FIG. 5 is a perspective view illustrating the present invention being in a state of running; 
     FIG. 6 is a top view of a base plate of the present invention in the second embodiment thereof; 
     FIG. 7 is a top view of a base plate of the present invention in the third embodiment thereof; 
     FIG. 8 is a top view of one of a base plate of the present invention in the fourth embodiment thereof; 
     FIG. 9 is a side view of the base plate shown in FIG. 8; 
     FIG. 10 is a top view of a base plate of the present invention in the fifth embodiment thereof; and 
     FIG. 11 is a sectional view of the base plate shown in FIG.  10 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to FIG. 1, a counter flow heat exchanger with integrated fins and tubes according to the present invention comprises a metal base plate  10  worked and formed by a press or rolled by a cutter. The base plate  10  has two ends with a first projection  11  and a second projection  12 , respectively, and a part in between having a plurality of depressions  13  with bottom surfaces and projections  14  with top surfaces. The first and second projections  11 ,  12  have regularly arranged inward extending projecting sections  111 ,  121 , and the projections  14  each have regularly arranged projecting sections  141 ,  142  extending to opposite sides. A ridge  131  is placed in each depression  13  with both ends thereof having connecting tubes  132  reaching up to the level of the top surfaces of the projections  14 . Similarly, a groove  143  is placed in each projection  14  with both ends thereof having connecting tubes  144  reaching down to the level of the bottom surfaces of the depressions  13 . The connecting tubes  132  have through holes  133  at upper ends thereof and the connecting tubes  144  have through holes  145  at lower ends thereof. Further, the ridges  131  and the grooves  143  have shapes thereof corresponding to each other. 
     Referring to FIG. 2 in company with FIG. 1, a metal external plate  20  is used for closing the through holes  133  and the grooves  143  in the base plate  10  from above. The external plate  20  is shaped like the base plates  10 , having, however, connecting tubes  211  and  221  without through holes. 
     Referring to FIG. 3, an external plate  20  and multiple base plates  10  are disposed to be reversed to each other and the plates are joined to each other by brazing. When assembled, pairs of ridges  21 ,  131 , a respective space between two ridges  131  and a respective space between two grooves  143  form horizontal tubes  15 . Ridge  21 ,  131  and connecting tubes  132  form series vertical tubes  16  and grooves  143  and connecting tubes  144  form series vertical tubes  16 . Air holes  17  are provided between every neighboring two horizontal tubes  15  and formed by spaces between the projections  14  and the ridges  131  and between the depressions  13  and the grooves  143 . Due to design of projecting sections  111 ,  121 ,  141 ,  142 , it is possible to enhance turbulent effect while the air passes through the air holes  17  and to increase contact surface between air and the base plates  10 . Hence, the efficiency of heat exchange can be promoted. 
     Referring to FIG. 4, alternatively, a flat plate  23  replaces the external plate  20  in FIG. 3 to close the through holes  133  and the depressions  143  so that the same heat exchange effect as that shown in FIG. 3 is attained. 
     For using the present invention, as shown in FIG. 5, a lowermost base plate of the plate assembly in FIG. 3 or FIG. 4 is connected to two guide tubes  30  so that a heat exchange unit  40  can be set up. The lowermost base plate at the through holes in the ridges thereof and in connecting tubes on grooves thereof communicate with the two guide tubes  30  respectively. The two guide tubes  30  are respectively connected to a fluid pumping unit  60  via connecting pipes  50 ,  51 . If the fluid pumping unit  60  is an attach block over a heat source, heat generated by the heat source can be absorbed by the attach block and the absorbed heat is transmitted to the heat exchange unit  40  by the fluid in the tubes so that a process of heat dissipation can be conducted there. Due to the tubes of the heat exchange unit  40  being specially designed, the fluid in the tubes flows from right to left and outside fluid  70  counter flows from left to right respectively as directions shown in FIG.  5 . The air holes  17  inside the heat exchange unit  40  shown in FIG. 3 ensure exchange of heat. Since there is a counter flow of internal fluid against external fluid, a better efficiency of heat exchange is achieved, and the deficiency of temperature gradient can be improved so that the fluid  70  has a uniform temperature distribution. If, for instance, the fluid pumping unit  60  is a compressor, the fluid in inside the tubes is refrigerant and the fluid  70  outside the tubes is air, the air out of the heat exchange unit  40  can be in a state of uniform temperature distribution so as to obtain a preferable temperature sensitivity. 
     Referring to FIG. 6 in company with FIG. 1 again, a second embodiment of the present invention has base plates  80  with oval shaped connecting tubes  801 ,  802  replacing the circular connecting tubes  132 ,  144  of the first embodiment. Thus, the oval cross section has a larger area than the circular cross section so that connecting tubes on two base plates  80  at adjacent levels can be connected to each other more conveniently and firmly. 
     As shown in FIG. 7 in company with FIG. 6, a third embodiment of the present invention has base plates  81 . Each of the base plates  81  provides with additional circular connecting tubes  811  with or without through holes on each ridge thereof instead of the ridge  803  on the base plates  80  shown in FIG.  6 . Furthermore, each groove on the base plate  81  has additional circular connecting tubes  812  with or without through holes instead of the groove  804  shown in FIG.  6 . The connecting tubes  811 ,  812  can make two base plates  81  at adjacent levels be connected to each other more conveniently and firmly. 
     Referring to FIGS. 8 and 9 in company with FIG. 6 again, a fourth embodiment of the present invention has base plates  82  and each of the base plates  82  is provided with reinforcing ribs  821  under each of the projecting sections. 
     As shown in FIGS. 10 and 11 in company with FIG. 6 again, a fifth embodiment of the present invention has base plates  83  and each of the base plates  83  is provided with ridges  831  instead of grooves  804  shown in FIG.  6 . Projecting sections  806 ,  807 ,  808 ,  809  thereof are replaced with reinforcing ribs  832 ,  333 ,  834 ,  835 , respectively. 
     Referring again to FIGS. 1,  2 ,  3  and  4 , the fins and the tubes in the heat exchange unit are formed by way of the base plates  10  being associated with the external plate  20  integrally so that it can eliminate the efficiency loss of heat transfer due to thermal resistance at contact surfaces completely. Moreover, automatic working equipment can be utilized to perform the assembling job so that the equipment expense and labor cost can be lowered down largely. A consistent specification for the base plate  10  and the external plate  20  can be designated so that it is only needed to develop a single molding tool with a set of required width for the plates. The length of the plates can be formed by way of a continuous working process, e.g., each of the plates will be cut to a preset length thereof automatically during the working process so that all plates with different length thereof can be obtained as needed. In addition, the height of the exchanger unit can be adjusted by way of increasing the number of packed plates. Hence, heat exchange units with various lengths and heights are possibly made with the molding tool so that it is not necessary to prepare different molding tools for different specifications of heat exchanger units done in the conventional heat exchangers. Accordingly, the manufacturing cost can be saved greatly. 
     While the invention has been described with reference to preferred embodiments thereof, it is to be understood that modifications or variations may be easily made without departing from the spirit of this invention which is defined by the appended claims.