Abstract:
A heat sink ( 10 ) includes a plurality of fins ( 12 ). Each of the fins includes a main body ( 122 ) and at least one bulge ( 126 ) disposed on the main body. The main bodies of two adjacent fins cooperatively define an air passage ( 121 ) therebetween, for allowing an airflow to pass therethough. The bulge has a varying projection height so as to form a streamline guide surface ( 127 ) thereon.

Description:
FIELD OF THE INVENTION  
       [0001]     The present invention relates generally to a heat sink, and more particularly to a heat sink for dissipating heat generated by electronic components, wherein fins of the heat sink project bulges therefrom for increasing heat dissipation efficiency of the heat sink.  
       DESCRIPTION OF RELATED ART  
       [0002]     A conventional heat dissipating apparatus includes a heat sink thermally connected with a heat source for absorbing heat therefrom, and a heat dissipating fan for providing an airflow, which flows through the heat sink to take away heat therefrom. The heat sink includes a plurality of fins with two opposite planar surfaces. A plurality of air passages is formed between the fins allowing the airflow to flow therebetween.  
         [0003]     When the airflow flowing through the air passages of the heat sink, the airflow is laminar or turbulent. Turbulent airflow increases heat convection efficiency between the fins and the airflow, which further increases heat dissipation efficiency of the heat dissipating apparatus. However, even if the airflow is turbulent, a laminar sublayer is still formed adjacent to the surfaces of the fins where the airflow contacts with the fins. The thickness of the laminar sublayer is gradually increased when the airflow flowing through the air passages of the heat sink. The increase in thickness of the laminar sublayer causes a decrease in heat convection efficiency. Therefore, reducing the laminar sublayer and so improving heat convection efficiency is key in increasing the heat dissipation efficiency of the heat dissipating apparatus.  
       SUMMARY OF THE INVENTION  
       [0004]     The present invention relates to a heat sink for dissipating heat from a heat-generating electronic component. According to a preferred embodiment of the present invention, the heat sink includes a plurality of fins. Each of the fins includes a main body and at least one bulge disposed on the main body. The main bodies of two adjacent fins cooperatively define an air passage therebetween, allowing airflow to pass therethough. The bulge has a varying projection height so as to form a streamline guide surface thereon. Furthermore, the bulge facilitates creating turbulence on surfaces of the fin, thereby increasing heat dissipation effectiveness of the fin when an airflow flows through the fin.  
         [0005]     Other advantages and novel features of the present invention will become more apparent from the following detailed description of preferred embodiment when taken in conjunction with the accompanying drawings, in which: 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0006]      FIG. 1  is an isometric view of a heat sink according to a preferred embodiment of the present invention;  
         [0007]      FIG. 2  is an isometric view of a fin of the heat sink of  FIG. 1 ;  
         [0008]      FIG. 3  is an isometric view of a fin of a heat sink according to a second embodiment of the present invention; and  
         [0009]      FIG. 4  is an isometric view of a heat sink according to a third embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0010]     Referring to  FIGS. 1 and 2 , a heat sink  10  according to a preferred embodiment of the present invention is shown. A heat dissipating fan (not shown) is disposed at one side of the heat sink  10 , for providing an airflow passing through the heat sink  10  to take away heat therefrom as indicated by arrows of  FIG. 1 . The heat sink  10  includes a plurality of parallel fins  12  and a heat pipe  14  extending through the fins  12 . The heat pipe  14  has two opposite ends respectively connecting with a heat-generating electronic component (not shown) and the fins  12 , for transferring heat therebetween.  
         [0011]     Each of the fins  12  includes a rectangular shaped main body  122 , and two flanges  123  extending from two opposite ends of the main body  122 . The fins  12  are stacked together with the flanges  123  of a rear fin  12  abutting against the main body  122  of a front fin  12 . A plurality of air passages  121  are formed between two adjacent fins  12  to allow the airflow pass through. The main body  122  of each fin  12  defines a receiving hole  124  at a top portion thereof, for allowing the heat pipe  14  to extend therethrough. A collar  125  extends forwards from a periphery of the receiving hole  124 , thus increasing the contacting areas between the fins  12  and the heat pipe  14 . The heat convection between the fin  12  and the heat pipe  14  is thus increased due to the collar  125 .  
         [0012]     Each fin  12  projects a bulge  126  forwards from the main body  122  thereof. The bulge  126  extends from the bottom and right corner of the main body  122  toward the bottom and left side of the heat pipe  14 . The extension direction of the bulge  126  is at an obtuse angle to the flow direction of the airflow. The joint of the bulge  126  and the main body  122  is rhombus-shaped in profile. The projection height of the bulge  126  gradually decreases from a center of the bulge  126  toward that of the joint. Two streamline guide surfaces  127  with arrow-shaped profiles are formed on the bulge  126 . The guide surfaces  127  extend from two acute corners of the bulge  126  toward a middle portion thereof and join with each other thereat. The profile of the guide surface  127  reduces the air resistance of the bulge  126 .  
         [0013]     When the airflow reaches the bulges  126  of the fins  12 , one part of the airflow strides over the bulges  126 , going straight ahead, whilst the other part of the airflow moves towards the heat pipe  14  along the guide surfaces  127  of the bulges  126 . There is more airflow flowing toward the heat pipe  14 , which removes more heat from the heat pipe  14 . The heat dissipation efficiency of the heat sink  10  is thus increased. Moreover, the airflow flowing through the air passages  121  of the fins  12  is deflected by the bulges  126  projecting from the main bodies  122  of the fins  12 . The turbulence of the airflow reduces the thickness of the laminar sublayer, which increases the heat convection between the fins  12  and the airflow, and further improves the heat dissipation efficiency of the heat sink  10 . In addition, the bulges  126  increase the heat dissipation areas of the fins  12 , and further increase the heat dissipation efficiency of the heat sink  10 .  
         [0014]     Referring to  FIG. 3 , the fin  12   a  of the heat sink  10  of the second embodiment of the present invention is shown. In this embodiment, the main body  122  of the fin  12   a  projects three parallel bulges  126   a . The extension lengths of the bulges  126   a  decrease from the left side of the main body  122  toward the right side thereof. The bulge  126   a  at the left side of the main body  122  extends from the bottom and right corner of the main body  122  toward the bottom and left side of the collar  125 , in a manner such that it can guide more airflow to flow toward the heat pipe. Referring to  FIG. 4 , the third embodiment of the heat sink  10   b  of the present invention is shown. The difference between this embodiment from the second embodiment is that the extension directions of the bulges  126   b  are different from each other. The bulges  126   b  guide the airflow flowing toward the heat pipe  14  along different directions. Air turbulence is thus generated, which increases the heat convection of the fins  12  and the airflow near the heat pipe  14 , and further improves the heat dissipation efficiency of the heat sink  10   b . Alternatively, the heat sink may include a plurality of heat pipes, whist the main body of each fin projects a plurality of bulges towards the heat pipes. When the main body of each of the fins projects more than two bulges, the bulges can be arranged on two opposite surfaces of the main body.  
         [0015]     In the above mentioned embodiments of the present invention, the joint of the bulge  126  and the main body  122  of the fin  12  has been rhombus-shaped in profile. Alternatively, that joint may be ellipse-shaped or other shaped in profile. When the main body of the fin projects more than two bulges, the joints of the bulges and the main body may have the same or different profiles.  
         [0016]     It is to be understood, however, that even though numerous characteristics and advantages of the present invention have been set forth in the foregoing description, together with details of the structure and function of the invention, the disclosure is illustrative only, and changes may be made in detail, especially in matters of shape, size, and arrangement of parts within the principles of the invention to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed.