Abstract:
A heat exchanger includes: a plurality of first heat radiation members, each of the plurality of first heat radiation members including a first refrigerant flow path through which a refrigerant flows; a plurality of second heat radiation members, each of the plurality of second heat radiation members including a second refrigerant flow path through which the refrigerant flows; and a fin attached between the plurality of second heat radiation members, wherein an interval between the plurality of first heat radiation members is smaller than an interval between the plurality of second heat radiation members.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is based upon and claims the benefit of priority of the prior Japanese Patent Application No. 2015-003810, filed on Jan. 13, 2015, the entire contents of which are incorporated herein by reference. 
     FIELD 
     The embodiments discussed herein are related to a heat exchanger, a cooling unit, and an electronic device. 
     BACKGROUND 
     Recently, miniaturization of electronic devices such as a desktop personal computer, a mobile personal computer, and a server is being promoted. Electronic components such as a central processing unit (CPU) used in these electronic devices generate heat as they are operated. 
     When the temperature of the electronic components such as the CPU exceeds a permissible upper temperature limit, a problem such as a failure, malfunction, or a decrease in processing capability is caused. Thus, a means for cooling an electronic component that generates a large amount of heat is required. 
     An air-cooling method and a water-cooling method are used to cool the electronic components. In the case of cooling an electronic component that generates a large amount of heat, the water-cooling method is often employed. Hereinafter, the electronic component that generates a large amount of heat will be referred to as a heat generation component. 
     In a water-cooling type cooling apparatus, a heat receiving part is mounted on the heat generation component, and a heat exchanger and a cooling fan are arranged at a location that is spaced away from the heat receiving part, and the heat receiving part and the heat exchanger are connected to each other via a pipe. The heat receiving part is provided with a flow path through which the cooling water flows. By circulating the cooling water between the heat receiving part and the heat exchanger, the heat generated from the heat generation component is transferred to the heat exchanger, and then is dissipated from the heat exchanger to the atmosphere. The heat exchanger is provided with a plurality of heat radiation fins along a flow path through which a refrigerant flows. 
     Further, herein, water or other fluids (refrigerant) that are used for transferring heat from the heat receiving part to the heat exchanger will be referred to as “cooling water.” 
     With the miniaturization of the electronic device, miniaturization is also required for the heat exchanger mounted in the electronic device. However, when the size of the heat exchanger is merely reduced, the flow path of the cooling water is narrowed so that a pressure loss increases and the flow rate of the cooling water flowing in the heat exchanger and the heat receiving part is reduced. Consequently, the heat exchange efficiency of the heat exchanger is lowered so that the heat generation component may not be sufficiently cooled. 
     The followings are a reference documents. 
     [Document 1] Japanese Laid-Open Patent Publication No. 2014-053507, 
     [Document 2] Japanese Laid-Open Patent Publication No. 2014-052142, 
     [Document 3] Japanese Examined Utility Model Registration Application Publication No. 02-005326 and 
     [Document 4] Japanese Laid-Open Patent Publication No. 11-230638. 
     SUMMARY 
     According to an aspect of the invention, a heat exchanger includes: a plurality of first heat radiation members, each of the plurality of first heat radiation members including a first refrigerant flow path through which a refrigerant flows; a plurality of second heat radiation members, each of the plurality of second heat radiation members including a second refrigerant flow path through which the refrigerant flows; and a fin attached between the plurality of second heat radiation members, wherein an interval between the plurality of first heat radiation members is smaller than an interval between the plurality of second heat radiation members. 
     The object and advantages of the invention will be realized and attained by means of the elements and combinations particularly pointed out in the claims. 
     It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are not restrictive of the invention, as claimed. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a perspective view illustrating a heat exchanger according to a first exemplary embodiment; 
         FIG. 2  is a front view illustrating the heat exchanger according to the first exemplary embodiment; 
         FIG. 3  is a sectional view illustrating a first header portion; 
         FIG. 4  is a sectional view illustrating a second header portion; 
         FIG. 5  is a perspective view illustrating a cooling unit including the heat exchanger according to the first exemplary embodiment; 
         FIG. 6  is a block diagram illustrating the configuration of the cooling unit; 
         FIG. 7  is a perspective view illustrating an electronic device including the cooling unit; 
         FIG. 8  is a side view illustrating the interior of the electronic device; 
         FIG. 9  is a plan view illustrating the interior of the electronic device; 
         FIG. 10  is a perspective view illustrating a heat exchanger according to a second exemplary embodiment; 
         FIG. 11  is a perspective view illustrating the heat exchanger according to the second exemplary embodiment; 
         FIG. 12  is a sectional view illustrating a first header portion; 
         FIG. 13  is a sectional view illustrating a second header portion; 
         FIG. 14  is a perspective view illustrating a cooling unit including the heat exchanger according to the second exemplary embodiment; and 
         FIG. 15  is a side view illustrating the interior of an electronic device including the cooling unit. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Hereinafter, exemplary embodiments will be described with reference to the accompanying drawings. 
     First Exemplary Embodiment 
       FIG. 1  is a perspective view of a heat exchanger  20  according to a first exemplary embodiment, and  FIG. 2  is a front view of the same heat exchanger  20 . 
     The heat exchanger  20  according to this exemplary embodiment includes a first header portion  21 , a pair of second header portions  22  disposed with the first header portion  21  being interposed therebetween, and first and second heat radiation members  23  and  24  that interconnect the first header portion  21  and the second header portions  22 . 
     All the first and second heat radiation members  23  and  24  are tube-shaped or plate-shaped members, each having therein a space through which the cooling water flows. The first heat radiation members  23  and the second heat radiation members  24  are disposed horizontally such that a plurality of first heat radiation members and a plurality of second heat radiation members are arranged side by side in the vertical direction, respectively. 
     In the present exemplary embodiment, a plate-shaped member called a perforated pipe is used as the first and second heat radiation members  23  and  24 . In the perforated pipe, a plurality of holes, which perforate the perforated pipe from one end surface to the other end surface thereof, are provided in parallel. According to this exemplary embodiment, as illustrated in  FIGS. 1 and 2 , five first heat radiation members  23  are located at a lower side, while five second heat radiation members  24  are located at an upper side. In other words, in this exemplary embodiment, the first and second heat radiation members  23  and  24  are arranged side by side in a height direction. 
     Further, the number of each of the first and second heat radiation members  23  and  24  may be set as appropriate, without being limited to five (5). Further, the number of the first heat radiation members  23  may be different from the number of the second heat radiation members  24 . 
     A plurality of heat radiation fins  25  are provided between the second heat radiation members  24 . In order to install these fins  25 , the interval between neighboring second heat radiation members  24  is set to be relatively large. In contrast, no fin is provided between the first heat radiation members  23 , and the interval between the first heat radiation members  23  is set to be relatively small. 
     The first heat radiation members  23 , the second heat radiation members  24 , and the fins  25  are made of a metal having good heat conductivity such as, for example, aluminum or copper. 
       FIG. 3  is a sectional view illustrating the first header portion  21 , and  FIG. 4  is a sectional view illustrating the second header portion  22 . 
     As illustrated in  FIG. 3 , the first header portion  21  is provided with a cooling water inlet  27   a  and a cooling water outlet  27   b . Further, the first header portion  21  is partitioned into a first space S 1  connected to the cooling water inlet  27   a  and a second space S 2  connected to the cooling water outlet  27   b , by a partition wall  21   a . The first space S 1  is located at a lower side, while the second space S 2  is located at an upper side. The cooling water inlet  27   a  is an example of a first connection port, and the cooling water outlet  27   b  is an example of a second connection port. 
     The first space S 1  is connected to a hole (hereinafter, referred to as a “cooling water flow path  23   a ”) of the first heat radiation member  23 , and the second space S 2  is connected to a hole (hereinafter, referred to as a “cooling water flow path  24   a ”) of the second heat radiation member  24 . 
     The cooling water flowing from the cooling water inlet  27   a  into the first space S 1  of the first header portion  21  further enters the cooling water flow path  23   a  of the first heat radiation member  23 , and then moves to the second header portion  22  through the cooling water flow path  23   a.    
     As illustrated in  FIG. 4 , the second header portion  22  is provided with a third space S 3  that connects the cooling water flow path  23   a  of the first heat radiation member  23  with the cooling water flow path  24   a  of the second heat radiation member  24 . The cooling water, which has entered the second header portion  22  from the cooling water flow path  23   a  of the first heat radiation member  23 , flows upwards in the second header portion  22 , and then enters the cooling water flow path  24   a  of the second heat radiation member  24 . Further, the cooling water moves to the second space S 2  of the first header portion  21  through the cooling water flow path  24   a  of the second heat radiation member  24 , and is discharged from the cooling water outlet  27   b.    
       FIG. 5  is a perspective view illustrating a cooling unit  30  having the above-described heat exchanger  20 , and  FIG. 6  is a block diagram illustrating the configuration of the same cooling unit  30 . Further,  FIG. 7  is a perspective view illustrating an electronic device  40  having the same cooling unit  30 ,  FIG. 8  is a side view illustrating an interior of the same electronic device  40 , and  FIG. 9  is a plan view illustrating the interior of the same electronic device  40 . Furthermore, arrows in  FIG. 6  indicate the flow direction of the cooling water. 
     As illustrated in  FIGS. 5 and 6 , the cooling unit  30  includes a heat exchanger  20 , a heat receiving part  31 , a pump  32 , and a tank  33 . The heat receiving part  31  is provided with a flow path through which the cooling water flows, and is thermally connected to a heat generation component  11  (see, e.g.,  FIG. 8 ). Further, the heat generation component  11  and other electronic components are mounted on a circuit board  10 . 
     The cooling water inlet  27   a  of the heat exchanger  20  is connected to the cooling water flow path in the heat receiving part  31  through a pipe  28   a . Further, the cooling water outlet  27   b  is connected to the tank  33  through a pipe  28   b . Further, as illustrated in  FIG. 6 , the tank  33  and the pump  32  are connected to each other by a cooling water flow path  34   a , and the pump  32  and the heat receiving part  31  are connected to each other by a cooling water flow path  34   b.    
     According to this exemplary embodiment, a plurality of pumps  32  (e.g., six pumps in  FIG. 5 ) are connected in parallel between the tank  33  and the heat receiving part  31  to increase the flow rate of the cooling water. In this regard, the number of the pumps  32  may be set as appropriate. For example, the number of the pumps  32  may be one (1). 
     As illustrated in  FIGS. 5 and 8 , the cooling unit  30  is secured to the circuit board  10  by, for example, four locking pins  35  and springs  36 . 
     The electronic device  40  includes a case  41 , a circuit board  10 , a cooling unit  30 , and a cooling fan  42 . The circuit board  10 , the cooling unit  30 , and the fan  42  are disposed within the case  41 . In the electronic device  40  illustrated in  FIGS. 7 and 8 , a plurality of fans  42  are disposed on an end of the case  41 , and a duct  43  is provided between the fans  42  and the heat exchanger  20  to guide air from the fans  42  to the heat exchanger  20 . 
     Hereinafter, an operation of the cooling unit  30  according to this exemplary embodiment will be described. 
     The heat generation component  11  generates heat while being operated. However, since the heat generation component  11  is thermally connected to the heat receiving part  31  (see, e.g.,  FIGS. 6 and 8 ), the heat generation component  11  is cooled by the cooling water flowing in the heat receiving part  31  so that the temperature is kept under a permissible upper temperature limit. Further, the temperature of the cooling water flowing in the heat receiving part  31  rises as the heat generation component  11  is cooled. 
     The high-temperature cooling water discharged from the heat receiving part  31  flows into the first space S 1  of the first header portion  21  of the heat exchanger  20  through the pipe  28   a  and the cooling water inlet  27   a . Further, the cooling water flows from the first space S 1  into the third space S 3  of the second header portion  22  through the first heat radiation member  23 . Furthermore, the cooling water flows from the second header portion  22  into the second space S 2  of the first header portion  21  through the second heat radiation member  24  (see, e.g.,  FIGS. 3 and 4 ). 
     When the cooling water passes through the first and second heat radiation members  23  and  24 , a heat exchange process is performed between the air sent by the fans  42  and the cooling water passing through the first and second heat radiation members  23  and  24 , so that the temperature of the cooling water drops. 
     The low-temperature cooling water discharged from the cooling water outlet  27   b  of the heat exchanger  20  flows into the tank  33  through the pipe  28   b . Further, the cooling water is temporarily stored in the tank  33 , and then is transferred to the heat receiving part  31  by the pumps  32  (see, e.g.,  FIG. 6 ). 
     Thus, the cooling unit  30  according to the present exemplary embodiment sequentially circulates the cooling water through the heat receiving part  31 , the heat exchanger  20 , the tank  33 , and the pumps  32 , so that heat generated from the heat generation component  11  is transferred to the heat exchanger  20 , and is dissipated from the heat exchanger  20  to the atmosphere. 
     For example, when the size of the heat exchanger is simply reduced as in the related art, the cooling water flow path of the heat radiation member is narrowed and the flow rate of the cooling water capable of flowing in the heat exchanger decreases. Further, the density of the fins increases, so that a significant pressure loss occurs in the air passing through the heat exchanger. Hence, when the size of the heat exchanger is simply reduced as in the related art, this leads to a considerable reduction in the heat exchange efficiency of the heat exchanger. 
     Whereas, the heat exchanger  20  according to the present exemplary embodiment is configured such that no fin is provided between the first heat radiation members  23  and the interval between the first heat radiation members  23  is small. Thus, the size of the heat exchanger may be reduced without reducing the size of the heat radiation members (e.g., the first and second heat radiation members  23  and  24 ). Further, since it is not necessary to reduce the size of the heat radiation members, a large amount of cooling water may flow into the heat exchanger  20 . 
     Further, the heat exchanger  20  according to the present exemplary embodiment may be configured such that the interval between the first heat radiation members  23  is small and the interval between the second heat radiation members  24  is large. Thus, the fins  25  may be arranged at a proper density between the second heat radiation members  24 . As described above, when the size of the heat exchanger according to the related art is merely reduced, the density of fins increases so that a significant pressure loss occurs in the air passing through the heat exchanger, but such a problem may be avoided in the heat exchanger  20  according to the present exemplary embodiment. 
     In the present exemplary embodiment, since no fin exists between the first heat radiation members  23 , a pressure loss may decrease in the air passing through the heat exchanger  20  so that the entire cooling capacity of the apparatus is improved. Moreover, since the miniaturization of the apparatus may be realized without reducing the size of the heat radiation members  23  and  24 , a pressure loss in the flow paths of the heat radiation members  23  and  24  may also be reduced, and consequently the flow rate of the cooling water may increase. Therefore, the temperature of the cooling water discharged from the heat exchanger  20  may be sufficiently lowered. 
     For example, according to the heat exchanger  20  of the present exemplary embodiment, the flow rate of the cooling water may increase 1.7 times while the flow rate of the air increases 1.2 times, as compared to the conventional heat exchanger having the same size. Accordingly, the heat exchanger  20  of the present exemplary embodiment has sufficiently high heat exchange efficiency even if the heat exchanger  20  is miniaturized. Further, since the cooling unit  30  and the electronic device  40  use the heat exchanger  20  that has high heat exchange efficiency, the heat generation component  11  may be sufficiently cooled. 
     Further, in the exemplary embodiment, descriptions have been made on a case where the second header portions  22 , the first heat radiation members  23 , and the second heat radiation members  24  are disposed on the opposite sides of the first header portion  21 , respectively. However, the second header portion  22 , the first heat radiation member  23  and the second heat radiation member  24  may be disposed on only one side of the first header portion  21 . 
     Second Exemplary Embodiment 
       FIG. 10  is a perspective view illustrating a heat exchanger  50  according to a second exemplary embodiment when viewed from a rear side, and  FIG. 11  is a perspective view illustrating the same heat exchanger  50  when viewed from a front side. Here, for the convenience of description, a side where a cooling water inlet  57   a  and a cooling water outlet  57   b  are provided is referred to as a front side while the opposite side thereof is referred to as a rear side. 
     The heat exchanger  50  according to the present exemplary embodiment includes a first header portion  51 , a pair of second header portions  52  disposed with the first header portion  51  being interposed therebetween, and first and second heat radiation members  53  and  54  that interconnect the first and second header portions  51  and  52 . As in the first exemplary embodiment, a perforated pipe is used as each of the first and second heat radiation members  53  and  54  in the present exemplary embodiment. 
     The first heat radiation members  53  and the second heat radiation members  54  are disposed horizontally such that a plurality of first heat radiation members and a plurality of second heat radiation members are arranged side by side in the vertical direction, respectively. According to the present exemplary embodiment, as illustrated in  FIGS. 10 and 11 , the plurality of first heat radiation members  53  are arranged in the front side (the side where a cooling water inlet  57   a  and a water outlet  57   b  are located), while the plurality of second heat radiation members  54  are arranged in the rear side. That is, in the present exemplary embodiment, assuming that the height direction is defined as a first direction, the direction where a first refrigerant flow path  53   a  extends is defined as a second direction, and the direction perpendicular to the first and second directions is defined as a third direction, the first and second heat radiation members  53  and  54  are arranged side by side in the third direction (front-rear direction). 
     The interval between the second heat radiation members  54  is set to be relatively large. Further, a plurality of heat radiation fins  25  are disposed at a suitable interval between the second heat radiation members  54 . Meanwhile, no fin exists between the first heat radiation members  53 , and the interval between the first heat radiation members  53  is set to be relatively small. 
       FIG. 12  is a sectional view illustrating the first header portion  51 , and  FIG. 13  is a sectional view illustrating the second header portion  52 . 
     As illustrated in  FIG. 12 , a cooling water inlet  57   a  and a cooling water outlet  57   b  are provided in the first header portion  51 . Further, the first header portion  51  is partitioned into a first space S 1  connected to the cooling water inlet  57   a  and a second space S 2  connected to the cooling water outlet  57   b , by a diaphragm  51   a . The first space S 1  is connected to a hole (hereinafter, referred to as a “cooling water flow path  53   a ”) of the first heat radiation member  53 , and the second space S 2  is connected to a hole (hereinafter, referred to as a “cooling water flow path  54   a ”) of the second heat radiation member  54 . 
     The cooling water, which has entered the first space S 1  of the first header portion  51  from the cooling water inlet  57   a , further enters the cooling water flow path  53   a  of the first heat radiation member  53 , and moves to the second header portion  52  through the cooling water flow path  53   a.    
     As illustrated in  FIG. 13 , the second header portion  52  is provided with a third space S 3  that connects the cooling water flow path  53   a  of the first heat radiation member  53  with the cooling water flow path  54   a  of the second heat radiation member  54 . The cooling water, which has entered the second header portion  52  from the cooling water flow path  53   a  of the first heat radiation member  53 , flows in the second header portion  52  in a direction from the front side to the rear side, and then, enters the cooling water flow path  54   a  of the second heat radiation member  54 . Further, the cooling water moves to the second space S 2  of the first header portion  51  through the cooling water flow path  54   a  of the second heat radiation member  54 , and then is discharged from the cooling water outlet  57   b.    
       FIG. 14  is a perspective view illustrating a cooling unit  60  having the above-described heat exchanger  50 , and  FIG. 15  is a side view illustrating the interior of an electronic device  70  including the cooling unit  60  of  FIG. 14 . Components of  FIGS. 14 and 15 , which are the same as those of  FIGS. 5 and 8 , will be denoted by the same reference numerals. 
     As illustrated in  FIG. 14 , the cooling unit  60  has a heat exchanger  50 , a heat receiving part  31 , a pump  32 , and a tank  33 . The cooling water inlet  57   a  of the heat exchanger  50  is connected to a cooling water flow path in the heat receiving part  31  via a pipe  28   a , while the cooling water outlet  57   b  is connected to the tank  33  via a pipe  28   b.    
     As illustrated in  FIGS. 14 and 15 , the cooling unit  60  is secured to the circuit board  10  by, for example, four locking pins  35  and springs  36 . 
     Further, as illustrated in  FIG. 15 , the electronic device  70  includes a case  41 , a circuit board  10 , a cooling unit  60 , and a cooling fan  42 . The circuit board  10 , the cooling unit  60 , and the cooling fan  42  are disposed in the case  41 . 
     Since a cooling water circulation course is the same as the first exemplary embodiment, a detailed description thereof will be omitted here. 
     As in the first exemplary embodiment, in the present exemplary embodiment, no fin exists between the first heat radiation members  53  and the interval between the first heat radiation members  53  is set to be small. Further, the heat exchanger  50  according to the present exemplary embodiment is configured such that the interval between the first heat radiation members  53  is small and the interval between the second heat radiation members  54  is set to be large. Thus, the fins  25  are arranged at a proper density between the second heat radiation members  54 . 
     In this regard, similarly to the heat exchanger  20  according to the first exemplary embodiment, the heat exchanger  50  according to the present exemplary embodiment has sufficiently high heat exchange efficiency even if it is miniaturized. Further, since the cooling unit  60  and the electronic device  70  according to the present exemplary embodiment use the heat exchanger  50  that has high heat exchange efficiency, the heat generation component  11  may be sufficiently cooled down. 
     Further, in the exemplary embodiment, descriptions have been made on a case where the second header portions  52 , the first heat radiation members  53 , and the second heat radiation members  54  are disposed on the opposite sides of the first header portion  51 . However, the second header portion  52 , the first heat radiation member  53 , and the second heat radiation member  54  may be disposed on only one side of the first header portion  51 . 
     All examples and conditional language recited herein are intended for pedagogical purposes to aid the reader in understanding the invention and the concepts contributed by the inventor to furthering the art, and are to be construed as being without limitation to such specifically recited examples and conditions, nor does the organization of such examples in the specification relate to an illustrating of the superiority and inferiority of the invention. Although the embodiments of the present invention have been described in detail, it should be understood that the various changes, substitutions, and alterations could be made hereto without departing from the spirit and scope of the invention.