Patent Publication Number: US-2013233520-A1

Title: Flat heat pipe

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates to heat transfer apparatuses and, more particularly, to a flat heat pipe with enhanced heat dissipation efficiency. 
     2. Description of Related Art 
     Generally, flat heat pipes can efficiently dissipate heat from heat-generating components such as central processing units (CPU). A conventional flat heat pipe includes a hollow cover, a continuous wick structure mounted on an inner surface of the cover and working medium contained in the wick structure. A vapor chamber is defined between an inner surface of the wick structure. When the cover absorbs heat generated from the heat-generating components, the working medium is vaporized by the heat and enters into the vapor chamber in all directions of the inner surface of the wick structure. Therefore, the vaporized working medium from different directions of the wick structure tends to interfere with each other and forms turbulence. Thus, heat dissipation efficiency and stability performance of the flat heat pipe are badly affected. 
     What is needed is a flat heat pipe which can overcome the problem of the prior art. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic view of a flat heat pipe along a transverse direction thereof in accordance with an embodiment of the disclosure. 
         FIG. 2  is a schematic view of the flat heat pipe of  FIG. 1  along a longitudinal direction thereof. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to  FIG. 1 , a flat heat pipe  1  in accordance with an embodiment of the disclosure includes a hollow cover  10 , a restricting plate  30  received in the cover  10  and abutting against the cover  10 , a wick structure  50  mounted on the restricting plate  30 , and a working medium (not shown) contained in the wick structure  50 . The flat heat pipe  1  is used to thermally connect with heat-generating components (not shown) to absorb heat generated therefrom. 
     The cover  10  is integrally formed by one piece of metal such as copper or brass. The cover  10  includes an elongated top plate  11 , an elongated bottom plate  13  spaced from and facing the top plate  11 , and two convex connecting plates  15  located at lateral sides of the flat heat pipe  1  and interconnecting lateral edges of the top and bottom plates  11 ,  13 , respectively. A distance between outer surfaces of the top and bottom plates  11 ,  13  varies between 0.8 millimeter and 2.0 millimeter. The top plate  11 , the bottom plate  13  and the connecting plates  15  cooperatively define a receiving chamber  17  therebetween. 
     The wick structure  50  is a screen made of wires mesh or a sintered body sintered by metal powder. The wick structure  50  is an elongated strip and located at a central portion of the receiving chamber  17  along a longitudinal direction of the cover  10 . Top and bottom ends of the wick structure  50  abut against central portions of the top plate  11  and the bottom plate  13 , respectively. A transverse section of the wick structure  50  is substantially “II” shaped. The wick structure  50  includes a neck portion  51  and two adhering portions  53  located at top and bottom ends of the neck portion  51 , respectively. The neck portion  51  has a length along the longitudinal direction of the cover  10  equal to that of each adhering portion  53 , and a width along a transverse direction of the cover  10  less than that of each adhering portion  53 . The neck portion  51  connects central portions of the adhering portions  53 . The adhering portions  53  are respectively adhered to the central portions of the top and bottom plates  11 ,  13 . A capillary force of the adhering portion  53  is larger than that of the necking portion  51 . One of the adhering portions  53  and the necking portion  51  cooperatively form a bugle-shaped configuration. Edges of the wick structure  50  are rounded. Therefore a contacting area of the wick structure  50  contacting the vaporized working medium is increased relative to the conventional wick structure without rounded edges. 
     The restricting plate  30  is elongated, and made of a material having good heat transferring performance and compressive capacity, such as metal. The restricting plate  30  has a length along the longitudinal direction of the cover  10  equal to that of the receiving chamber  17 . A height of the restricting plate  30  is equal to a distance between inner surfaces of the top and bottom plates  11 ,  13 . The restricting plate  30  is arranged in a middle of the receiving chamber  17  along the longitudinal direction of the cover  10 . Top and bottom ends of the restricting plate  30  abut against the inner surface of the top plate  11  and the bottom plate  13 , respectively. The restricting plate  30  divides the receiving chamber  17  into a first passage  171  and a second passage  173  along the longitudinal direction of the cover  10 . The first passage  171  and the second passage  173  are hermetical and not in communication with each other. The restricting plate  30  divides the wick structure  50  into two wick portions  55  along a longitudinal direction of the wick structure  50 . The two wick portions  55  are symmetrical relative to restricting plate  50  and adhered on opposite lateral surface of the restricting plate  30 , respectively. The two wick portions  55  are located in the first and second passages  171 ,  173 , and at inner lateral sides of the first and second passage  171 ,  173 , respectively. 
     Referring also to  FIG. 2 , in operation, when one end, i.e. an evaporating section, of the flat heat pipe  1 , absorbs heat generated from the heat-generating components, the working medium in the wick portions  55  of the wick structure  50  in the evaporating section is vaporized by the absorbed heat and enters into the first passage  171  and the second passage  173  from the inner lateral sides of the first passage  171  and the second passage  173 , respectively. The vaporized working medium flows individually along the first passage  171  and the second passage  173  to another end of the flat pipe heat pipe  1 , i.e. a condensing section opposite to the evaporating section, to release heat thereof. After the vaporized working medium releases its heat and condenses in the condensing section, the condensed working medium is returned by the wick portions  55  to the evaporating section, where the condensed working medium is again available for evaporation and goes on a phase-change circulation. 
     Referring to  FIG. 1  again, in this embodiment, the width of the adhering portion  53  is larger than that of the necking portion  51 . The capillary force of the adhering portions  53  is larger than the necking portion  51 . Therefore, during operation, the working medium condensed on the top plate  11  can be rapidly absorbed by the adhering portion  53  mounted on the top plate  11  and flow towards the neck portion  51 , and then the condensed working medium in the neck portion  51  can be rapidly guided back the bottom plate  13  via the adhering portion  53  mounted on the bottom plate  13  to avoid the flat heat pipe  1  overheating. 
     In addition, the vaporized work medium enters into the first passage  171  and the second passage  173  only from the lateral sides of the first passage  171  and the second passage  173 , so the vaporized work medium enters into the first passage  171  or the second passage  173  in a smaller angle relative to the conventional flat heat pipe. Thus, interference between the vaporized work medium in the first passage  171  or the second passage  173  is decreased relative to the conventional flat heat pipe. A probability of forming turbulence of the vaporized work medium is decreased. Furthermore, a stability of the flat heat pipe  1  is also improved via opposite ends of the restricting plate  30  abutting the top plate  11  and the bottom plate  13 , simultaneously. 
     It is believed that the disclosed embodiment(s) and their advantages will be understood from the foregoing description, and it will be apparent that various changes may be made thereto without departing from the spirit and scope of the disclosure or sacrificing all of its material advantages, the examples hereinbefore described merely being preferred or exemplary embodiments of the disclosure.