Patent Publication Number: US-2013240195-A1

Title: Heat exchanger and method for fabricating the same

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This non-provisional application claims priority under 35 U.S.C. §119(a) on Patent Application No(s). 101109183 filed in Taiwan, R.O.C. on Mar. 16, 2012, the entire contents of which are hereby incorporated by reference. 
     BACKGROUND OF THE INVENTION 
     1. Technical Field of the Invention 
     The disclosure relates to a heat exchanger and method for fabricating the heat exchanger, and more particularly to a heat exchanger having a plurality of fins and method for fabricating the heat exchanger. 
     2. Description of the Related Art 
     A heat dissipation module for a cabinet server often uses air-cooling heat dissipation mode. The operation of air-cooling heat dissipation is to set heat dissipation fins on various heat sources and to set corresponding heat dissipation fans in the casing of the cabinet server. The heat convection forced by the heat dissipation fans can dissipate heat generated by the heat sources. In this heat dissipation manner, the environmental temperature of the casing is very high because after the airflow brought by the heat dissipation fans takes way heat, the environmental temperature will be increased. Therefore, during the heat dissipation for the cabinet server, the directions for dissipating heat needed to be uniformed so that a cold channel and a hot channel are formed to control the environmental temperature. If environmental temperature of equipment room is not well controlled, it is very difficult to decrease the temperature of the cabinet server. With area of the equipment room getting larger, the density of servers is getting much greater. The design and management of environmental temperature, cold channel and hot channel become increasingly complicated. 
     The liquid-cooling heat dissipation module provides another manner for dissipating heat. The liquid-cooling heat dissipation module does not use air to decrease temperature, and thus it will not have the shortcomings of the air-cooling heat dissipation. The liquid-cooling heat dissipation module comprises a cooling device and a cooling pipe connecting the cooling device. The cooling device and the cooling pipe are disposed on the cabinet. The cooling pipe is connected to a heat exchanger for a heat source. The heat exchanger comprises an upper casing and a base. A plurality of heat dissipation fins are disposed in parallel on the base. Multiple passages are formed between fins. The upper casing is assembled to the fins and covers the fins. The fins are set in a chamber formed by the upper casing and the base. A cooling liquid provided by the cooling device flows to the heat exchanger through the cooling pipe. In the heat exchanger, the cooling liquid flows through passages between fins and performs heat exchange with fins so as to take away heat absorbed by the fins. 
     However, height errors of the fins may occur when fabricating the fins. If the fins are too high, a gap between the base and the upper casing may be formed by interference of fins and the upper casing. In this case, inferior-quality products may occur due to the difficulty in sealing the base and the upper casing. In the other hand, if the fins are too low, a gap between the fins and the upper casing may be formed. In this case, cooling liquid may flow through the gap between the fins and the upper casing and does not sufficiently contact with the fins. Thus, the heat dissipation efficiency is influenced. 
     SUMMARY OF THE INVENTION 
     In one aspect, a method for fabricating a heat exchanger is disclosed. The method comprises providing a substrate. The substrate comprises a base portion and a processing portion on the base portion. A thickness of the processing portion is substantially gradually reduced along a first direction. At least one groove is formed on the processing portion. The at least one groove extends along a second direction which intersects with the first direction. A plurality of fins is skived in parallel on the base portion. The plurality of fins extends along the first direction. The groove passes through each fin. Each fin having an upper margin far away from the base portion. A distance between each upper margin and the bottom surface is substantially gradually reduced along the first direction. The plurality of fins is milled along the first direction. The maximum distance between the upper margin and a bottom surface of the base portion is smaller than or equal to a preset value. 
     In another aspect, a heat exchanger is disclosed. The heat exchanger comprises a base portion having a bottom surface and a plurality of fins disposed on a side of the base portion far away from the bottom surface. Each fin has an upper margin far away from the base portion. A distance between each upper margin and the bottom surface is substantially gradually reduced along a first direction. The upper margins sunken to form at least one groove, and the groove extends along a second direction which intersects with the first direction. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present disclosure will become more fully understood from the detailed description given herein below for illustration only, and thus are not limitative of the present disclosure, and wherein: 
         FIG. 1  is a flowchart for fabricating a heat exchanger according to an embodiment of the disclosure; 
         FIGS. 2A-7B  show a fabricating process for a heat exchanger according to an embodiment of the disclosure; 
         FIG. 7C  shows a fabricating process for a heat exchanger according to another embodiment of the disclosure; and 
         FIG. 8  is a structure illustration of a heat exchanger according to another embodiment of the disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     In the following detailed description, for purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of the disclosed embodiments. It will be apparent, however, that one or more embodiments may be practiced without these specific details. In other instances, well-known structures and devices are schematically shown in order to simplify the drawing. 
     The detailed characteristics and advantages of the disclosure are described in the following embodiments in details, the techniques of the disclosure can be easily understood and embodied by a person of average skill in the art, and the related objects and advantages of the disclosure can be easily understood by a person of average skill in the art by referring to the contents, the claims and the accompanying drawings disclosed in the specifications. 
       FIG. 1  is a flowchart for fabricating a heat exchanger according to an embodiment. In this embodiment, the heat exchanger may be used in a liquid cooling heat dissipation module which is disposed in a cabinet server. The heat exchanger dissipates the heat generated from heat sources in the cabinet server. The fabricating flow for the heat exchanger will be described as below. 
     Firstly, a substrate is provided. The substrate comprises a base portion and a processing portion on the base portion. The processing portion has an upper surface and the base portion has a bottom surface. That is, the upper surface is opposite to the bottom surface. The distance between the upper surface and the bottom surface is substantially gradually reduced along a first direction (step S 1 ). 
     Next, at least one groove is formed on the upper surface along a second direction which interacts with the first direction (step S 2 ). 
     The processing portion is skived to form a plurality of fins in parallel standing on the base portion. The fins extend along the first direction and the at least one groove passes through each fin. Each fin has an upper margin far away from the base portion. Furthermore, the distance between each upper margin and the bottom surface is substantially reduced along the first direction (step S 3 ). 
     The fins are cut along the first direction. The maximum distance between the upper margins and the bottom surface is smaller than or equal to a preset value (step S 4 ). 
     An upper casing is provided. The upper casing comprises an accommodating space. A liquid input and a liquid output are connected to the accommodating space (step S 5 ). 
     The upper casing is assembled to the base portion. The fins are set in the accommodating space. Furthermore, the liquid input and the liquid output are set at the two opposite ends of the fins (step S 6 ). 
       FIGS. 2A-7B  show a fabricating process for a heat exchanger according to an embodiment. The detailed process is set forth as below. 
     Firstly, as shown in  FIG. 2A , the substrate  100  is provided. The substrate  100  can be made of but not limited to metal, such as aluminium alloy. The substrate  100  can be made by aluminum extrusion, but the disclosure is not limited this way. The substrate  100  comprises a base portion  110  and a processing portion  120  on the base portion  110 . As shown in  FIG. 2B , the processing portion  120  has an upper surface  121  and the base portion  110  has a bottom surface  111 . The upper surface  121  is opposite to the bottom surface  111 . The thickness of the processing portion  120  is substantially gradually reduced along a first direction d 1 . In this embodiment, the distance between the upper surface  121  and the bottom surface  111  is substantially reduced along a first direction d 1 . For example, the upper surface  121  is a slope. As shown in  FIG. 2B , the distance between the upper surface of right end of the slope and the bottom surface  111  is represented by H 11 , and the distance between the upper surface of left end of the slope and the bottom surface  111  is represented by H 12 . The distance H 11  is larger than the distance H 12 . It should be noted that the term “substantially reduce” means a reducing trend along the first direction d 1 . In other words, if there is irregular fluctuation on a segment of the upper surface  121 , it is also regarded that the distance between the upper surface  1210  and the bottom surface  111  is substantially reduced along the first direction. 
     Next, as shown in  FIGS. 3A and 3B , at least one groove  122  are formed on the upper surface  121  along a second direction d 2  which interacts with the first direction by process such as milling. In the embodiment shown by  FIGS. 3A and 3B , the number of the grooves is for example two, but the number is not limited by this embodiment. Furthermore, the second direction d 2  is substantially perpendicular to the first direction d 1 . Here the term “substantially perpendicular” means that the angle intersected by the first direction d 1  and the second direction d 2  is approximately a right angle under appropriate processing errors. In other embodiments, the substrate  100  and the grooves  122  can be fabricated together by way of aluminum extrusion. 
     The processing portion  120  is skived to form a plurality of fins  130  in parallel standing on the base portion  110 . More particularly, as shown in  FIGS. 4A-4C , firstly the processing portion  120  is cut by using a knife  30  along the cutting direction d 3  so as to form a fin  130 . The cutting direction d 3  and the upper surface  121  form an acute angle θ, as shown by  FIG. 4B . Then, the fin  130  is bended to stand on the base portion  110 , as shown by  FIG. 4C . A plurality of fins  130  are formed in the same way as the above. The distance h 2  between the upper margins of the curved fins  130  and the bottom surface  111  is greater than the distance h 1  between the upper surface  121  to the bottom surface  111 . Furthermore, the smaller the acute angle θ is, cutting direction d 3  and the upper surface  121  form an acute angle θ, the larger the distance h 2  between the upper margin and the bottom surface  111  will be (i.e., the height of the fins will be larger). As a result, persons skilled in the art would obtain an expected height of fins  130  by adjusting the acute angle θ. 
     As shown by  FIG. 5A , the fins  130  extend along the first direction d 1 . The grooves  122  extend along the second direct and pass by each fin  130 . As shown in  FIG. 5B , two adjacent fins  130  have a passage  132  therebetween. Each fin  130  has an upper margin  131  far away from the base portion  110 . Each upper margin  131  is a part of the upper surface  121  and has part of the structural feature of the upper surface  121 . As a result, distance between each upper margin  131  and the bottom surface  111  is substantially reduced along the first direction d 1 . For example, as shown in  FIG. 5C , the distance H 21  between the right upper margin  131  and the bottom surface  111  is larger than the distance H 22  between the left upper margin  131  and the bottom surface  111 . In this embodiment, the upper surface  121  before milling and curving process is a slope, and thus after the milling and curving process, the upper margins  131  of fins  130  form an oblique line. However, the shape of the upper margin  131  is not limited by this embodiment. For example, if the upper surface  121  before milling and curving process is a step plane, the upper margin  131   s  of fins  130  may form approximately a broken line, as shown by  FIG. 8 . 
     With reference to  FIG. 6A , the fins  130  are milled by a knife  32  (e.g., milling cutter) along the first direction to make the maximum distance between the upper margin  131  and the bottom surface  111  is smaller than or equal to a preset value h 3 , where the value h 3  may be determined according to different requirements. In this way, the height of the fins  130  can be controlled within a certain range to avoid interference with other elements (e.g. the upper casing  200  in  FIG. 7A ) when assembly. 
     As described above, the distance between the upper margin  131  and the bottom surface  111  is substantially gradually reduced along the first direction d 1 . Each groove  122  extends along the second direction d 2  and is formed on the upper margin  131 . In this case, when milling the fins  130  along the first direction d 1  by using the knife  32 , the milling waste is easily removed and thus does not stuff the passage  132  between two fins  130 . 
     Then, with reference to  FIG. 7A , an upper casing  200  is provided. The upper casing  200  comprises an accommodating space  201 . A liquid input  210  and a liquid output  220  are connected to the accommodating space  201 . 
     The upper casing  200  is assembled to the base portion  110 . The fins  130  are set in the accommodating space  201 . As shown in  FIG. 7B , the liquid input  210  and the liquid output  220  are at the opposite two ends of the fins  130 . The upper casing  210  completely covers the base portion  110 , but the disclosure is not limited this way. For example, as shown in  FIG. 7C , the upper casing  200  can be assembled on the base portion  110  and partly covers the base portion  110 . 
     In this embodiment, the upper casing  200  may be assembled to the base portion  110  by a solder, but the disclosure is not limited this way. When assembling the upper casing  200  to the base portion  110 , the distance H 23  between the upper margin  131  near the liquid input  210  and the bottom surface  111  is larger than the distance H 22  between the upper margin  131  near the liquid output  220  and the bottom surface  111 . More particularly, the upper margin  131  near the liquid input  210  is substantially attached to the upper casing  200 . 
     With reference to  FIGS. 7A and 7B , the heat exchanger  10  may be fabricated by the above mentioned process. The heat exchanger  10  comprises the base portion  110  and a plurality of fins  130 . The base portion  110  has the bottom surface  111 . The fins  130  are disposed in parallel on the side far away from the bottom surface  111 . Each fin  130  has an upper margin  131  far away from the base portion  110 . Furthermore, the distance between each upper margin  131  and the bottom surface  111  is substantially gradually reduced along the first direction. The upper margins  131  sunken to form at least one groove  122 . Each groove  122  extends along the second direction d 2  which intersects with the first direction d 1 . The first direction d 1  is substantially perpendicular to the second direction d 2 . Furthermore, the upper margins may from approximately an oblique line or a broken line, but the disclosure is not limited this way. 
     In addition, in this embodiment, the heat exchanger  10  further includes an upper casing  200 . The upper casing  200  comprises an accommodating space  201 . A liquid input  210  and a liquid output  220  are connected to the accommodating space  201 . The upper casing  200  is assembled to the base portion  110 . The fins  130  are in the accommodating space  201 . The liquid input  210  and the liquid output  220  are set at two opposite ends of the fins  130 . The distance H 23  between the upper margin  131  near the liquid input  210  and the bottom surface  111  is larger than the distance H 22  between the upper margin  131  near the liquid output  220  and the bottom surface  111 . The upper margin  131  near the liquid input  210  is substantially attached to the upper casing  200 . In this case, when cooling liquid flows into the accommodating space  201  from the liquid input  210 , it will sufficiently contact with the fins  130  and does not flow away by the gap between the upper margin  131  and the upper casing  200 . Therefore, the heat dissipation efficiency can be improved. 
     According to the above embodiments of the heat exchangers and method for fabricating the heat exchangers, the distance between the upper margin of fins and the bottom surface is substantially gradually reduced along the first direction. The groove extends along the second direction and is formed on the upper margin. As a result, when cutting the fins along the first direction by using a knife, cutting waste is easily removed and does not stuff the passage between fins. Therefore, the heat exchangers and method for fabricating the same not only can avoid blocking passages with cutting waste but also can exactly control the height of fins. Furthermore, small bubbles brought by cooling liquid can be easily removed and thus the heat dissipation efficiency can be improved.