Abstract:
A flat loop heat pipe is formed of a first capillary core, a second capillary core, a first support member, and a second support member. The first capillary core and the first support member constitute an evaporation room. The second capillary core and the second support member constitute a compensation room. In light of this structure, it is not difficult to activate circulation of thermal dissipation under low-watt heat source and the first capillary core can avoid dry-out phenomenon.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates generally to heat-dissipating technology, and more particularly, to a flat loop heat pipe. 
         [0003]    2. Description of the Related Art 
         [0004]    A conventional loop heat pipe (LHP) is an effective heat-dissipating device and generally composed of an evaporator, a vapor line, a condenser, and a liquid line, all of which are connected and communicated with one another to become a loop containing a working fluid. The evaporator includes a capillary structure connected with a heat source. A compensation chamber is provided between the liquid line and the capillary structure. When the evaporator absorbs the heat from the heat source, the working fluid inside the LHP also absorbs the heat from the heat source to produce vapors. The vapors flow through a pipeline from the evaporator toward condenser chamber and then give out the heat at the condenser to be condensed and converted into liquid, and then the liquid drive into the evaporator to complete a cycle. In light of the aforesaid operation, the working fluid repeatedly adsorb heat to evaporate and give out heat to condense for thermal dissipation. 
         [0005]    The capillary structure in the evaporator of the conventional LHP is generally made of sintered powders. However, the sintered powders are solid to have greater flow resistance, such that it is difficult to activate the cycle of the thermal dissipation when the heat source is low-watt. In addition, when the evaporation rate of the working fluid in the evaporator is larger than the reflux rate of the liquid line, it is difficult to suck the working fluid from the compensation chamber to the evaporator, such that the working fluid in the evaporator is subject to dry-out to weaken the heat-dissipating performance of the LHP. 
       SUMMARY OF THE INVENTION 
       [0006]    The primary objective of the present invention is to provide a flat LHP, which can prevent circulation of thermal dissipation from difficult activation. 
         [0007]    The secondary objective of the present invention is to provide a flat LHP, which can enhance the heat-dissipating performance. 
         [0008]    The foregoing objectives of the present invention are attained by the flat LHP composed of a container, a first capillary core, a second capillary core, a circulatory pipeline, and a working fluid. The container includes a case, a cover, and a chamber formed therein between the case and the cover. The case has two openings, one of which is a vapor outlet and the other is a liquid inlet. The first capillary core is sleeve-shaped and mounted below the chamber, having a plurality of pores disposed thereon and an opening connected with the vapor outlet in airtight in such a way that an evaporation room is formed. The second capillary core is also sleeve-shaped and mounted above the chamber, having a plurality of pores disposed thereon, a lower part stopped against the first capillary core, and an opening stopped against the liquid inlet in such a way that a compensation room is formed. The circulatory pipeline includes a vapor line, a condensation line, a liquid reflux line, and an injection port. The vapor line has one end connected with the vapor outlet in airtight. The condensation line has one end connected with the vapor line in airtight. The liquid reflux line has two ends, one of which is connected with the condensation line in airtight and the other end is connected with the liquid inlet in airtight. The injection port is located at the vapor line or the liquid reflux line. The working fluid is infused into the circulatory pipeline to become a medium of heat absorption and dissipation. 
         [0009]    In light of the above structure, vapors generated from the working fluid under a heat source of relatively low wattage can still travel to the evaporation room, such that the flow resistance of the vapors is too little to cause overgreat pressure partially inside the evaporation room and to make it difficult for activating the circulation of thermal dissipation. Besides, the second capillary core is stopped against the first capillary core without contact with the heat source, such that no evaporation happens and then the second capillary core keeps absorbing the working fluid located in the compensation room to reinforce supplement of the working fluid required by the first capillary core. In this way, it can prevent the evaporation room from dry-out to further enhance the heat-dissipating performance of the flat LHP. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]      FIG. 1  is a partially sectional view of a preferred embodiment of the present invention. 
           [0011]      FIG. 2  is an exploded view of the preferred embodiment of the present invention. 
           [0012]      FIG. 3  is a perspective view of a part of the preferred embodiment of the present invention. 
           [0013]      FIG. 4  is another perspective view of a part of the preferred embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0014]    Referring to  FIGS. 1-4 , a flat LHP  1  constructed according to a preferred embodiment of the present invention is composed of a container  20 , a first capillary core  30 , a second capillary core  40 , a first support member  50 , a second support member  60 , a circulatory pipeline  70 , and a working fluid  80 . 
         [0015]    The container  20  includes a case  21  and a cover  22 . A chamber  23  is formed inside the container  20  and between the case  21  and the cover  22 . The case  21  has two openings, which are a vapor outlet  211  and a liquid inlet  212  respectively. The distance between a center of the vapor outlet  211  and a bottom side of the base  21  is smaller than the distance between a center of the liquid inlet  212  and the bottom side of the case  21 . The vapor outlet  211  and the liquid inlet  212  are mounted to a left side and a right side of the base  21 . 
         [0016]    Each of the first and second capillary cores  30  and  40  is structurally capillary and thin sleeve-shaped, having a close end  31 ( 41 ) at one end thereof, an open end  32 ( 42 ) at the other end thereof, and a plurality of pores disposed thereon. Each of the two capillary cores  30  and  40  can be made of a porous material, which can be sintered powers, a fine groove, a net, a fiber, or a composition of those materials. In this embodiment, each of the two capillary cores  30  and  40  is a metallic thin net having above 100 meshes. 
         [0017]    Each of the first and second support members  50  and  60  is a sleeve-shaped metallic thin net having less than 20 meshes, a close end  51 ( 61 ), an open end  52 ( 62 ), and a plurality of pores disposed thereon. The first capillary core  30  is sleeved onto the first support member  50 , and the second capillary core  40  is sleeved onto the second support member  60 . In this way, the first and second capillary cores  30  and  40  can be well supported by the first and second support members  50  and  60  respectively. 
         [0018]    The first capillary core  30  is sleeved into the first support member  50  by that the close end  31  is stopped against the close end  51 , thus forming an evaporation module  100 . The evaporation module  100  is mounted to a bottom side of the chamber  23  to enable the open ends  32  and  52  to face and be connected with the vapor outlet  211  in airtight in such a way that an evaporation room  33  is formed inside the first capillary core  30 . The second capillary core  40  is sleeved into the second support member  60  by that the close end  41  is stopped against the close end  61 , thus forming a compensation module  200 . The compensation module  200  is mounted to a top side of the chamber  23  to enable the open ends  42  and  62  to face and be connected with the liquid inlet  212  in airtight in such a way that a compensation room  43  is formed inside the second capillary core  40 . The sum of the height of the evaporation module  100  and of the compensation module  200  is larger than the height of the chamber  23 , such that the evaporation and compensation modules  100  and  200  squeeze each other. In other words, the contact area between a bottom side of the evaporation module  100  and an internal bottom side of the container  20  and between a top side of the evaporation module  100  and a bottom side of the compensation module  200  is relatively larger; the contact area between a bottom side of the compensation module  200  and the top side of the evaporation module  100  and between a top side of the compensation module  200  and an internal top side of the container  20  is relatively larger. 
         [0019]    The circulatory pipeline  70  includes a vapor line  71 , a condensation line  72 , a liquid reflux line  73 , and an injection port  74 . The vapor line  71  has one end connected with the vapor outlet  211  in airtight for guiding flowage of vapors. The condensation line has one end connected with the vapor line  71  in airtight. A heat sink  75  can be additionally mounted to an external periphery of the condensation line  72  for reinforcing thermal dissipation and condensation of the condensation line  72 . The heat sink  75  can be fins, a cooling fan, or the like. In this embodiment, the heat sink is fins. The liquid reflux line  73  has two ends, one of which is connected with the other end of the condensation line  72  in airtight and the other of which is connected with the liquid inlet  212  in airtight. The injection port  74  is located at the vapor line  71  or the liquid reflux line  73  for injecting the working fluid  80  and vacuating and sealing the flat LHP  1  therethrough. 
         [0020]    The working fluid  80 , which can be water, methanol, ammonia, or Freon, is injected through the injection port  74  into the flat LHP  1 . 
         [0021]    The flat LHP  1  can be applied to a central processing unit (CPU), a light emitting diode (LED), or another euthermic element. Referring to  FIG. 1  again, when the bottom side of the case  21  is in contact with a heat source (not shown), like a CPU or an LED, the heat source transmits the heat to the container  20  and the evaporation module  100 . The working fluid  80  existing in the first capillary core  30  absorbs the heat from the heat source. When the heat absorbed by the working fluid  80  is greater than its latent heat, the working fluid  80  proceeds with phase change to transform itself into the vapors from liquid and then to fill the evaporation room  33 . Next, the vapors flow into through the vapor outlet  211  into the vapor line  71  from the evaporation room  33  and then flow along the vapor line  71  into the condensation line  72 . When the vapors are located at the condensation line  72 , the heat in the vapors is dissipated for heat exchange with outside and the efficiency of such thermal dissipation is enhanced by the heat sink  75 . After the heat in the vapors is fully released, the working fluid  80  proceeds with another phase change to transform itself into liquid from the vapors. In the meantime, the working fluid  80  transformed into liquid is pushed by the vapors and then flow to the liquid reflux line  73  and finally back to the compensation room  43 . At last, the working fluid  80  returns to the first capillary core  30  by means of the capillary action of the second capillary core  40  for again absorbing the heat of the heat source. In this way, a working cycle is formed. 
         [0022]    During the above working cycle, the first support member  50  can upheave the first capillary core  30  to form the evaporation room  33 , such that the flow resistance of the vapors can be reduced and even when the heat source is low-watt, the flowage of the vapors can still cause a circulatory thermal dissipation without any difficulty. Besides, the second capillary core  40  keeps absorbing the working fluid  80  and then transmit the same to the first capillary core  30  to prevent the first capillary core  40  from drought. 
         [0023]    It is to be noted that the evaporation module  100  is formed of the first capillary core  30  and the first support member  50 ; however, if the first capillary core  30  is rigid enough, it will be not necessary to mount the first support member  50  into the first capillary core  30 . Likewise, the compensation module  200  is formed of the second capillary core  40  and the second support member  60 ; however, if the second capillary core  40  is rigid enough, it will be not necessary to mount the second support member  60  into the second capillary core  40 . The sum of the height of the first and second capillary cores  30  and  40  is preferably larger than that of the chamber  23  in such a way that the first and second capillary cores  30  and  40  can squeeze each other to enable the larger contact area therebetween. 
         [0024]    In addition, the present invention is to primarily enable the hollow compensation and evaporation rooms  43  and  33  to be spaced from each other by a capillary structure, such that only one sleeve-shaped capillary core mounted to the bottom side of the container and connected with the vapor outlet  211  in airtight can also space the compensation and evaporation rooms  43  and  33  from each other. This sleeve-shaped capillary core can lessen the flow resistance of the vapors and enable the flowage of the vapors to do circulatory thermal dissipation without any difficulty while the heat source is low-watt. 
         [0025]    Although the present invention has been described with respect to a specific preferred embodiment thereof, it is no way limited to the details of the illustrated structures but changes and modifications may be made within the scope of the appended claims.