Patent Publication Number: US-2017356690-A1

Title: Refrigerant heat exchanger

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is based on a patent application No. 2015-37254 filed in Japan on February 26, 2015, and whole contents of which application are incorporated by reference. 
     TECHNICAL FIELD 
     Disclosure in this specification relates to a refrigerant heat exchanger for heat exchange between a refrigerant for a refrigeration cycle and a heat medium. 
     BACKGROUND 
     Patent Literature 1 and Patent Literature 2 disclose heat exchangers which use a carbon fiber reinforced polymer (CFRP). Patent Literature 1 discloses the heat exchanger which uses CFRP for a tube and a fin. Patent Literature 2 indicates the heat exchanger which uses CFRP for a tube. 
     CITATION LIST 
     Patent Literature 
     Patent Literature 1: JP2008-138968A 
     Patent Literature 2: JP3140963U 
     SUMMARY 
     The Patent Literature 1 and Patent Literature 2 disclose no refrigerant heat exchanger which can be used with a refrigerant for a refrigeration cycle. In these conventional techniques, it is difficult to achieve a pressure-resistant property that can be withstood in a use of a refrigerant in a tube. In the above viewpoint, or in the other viewpoint not mentioned above, further improvement of a refrigerant heat exchanger is still demanded. 
     It is an object of disclosure to provide a light weight refrigerant heat exchanger. 
     It is another object of disclosure to provide a refrigerant heat exchanger having a high pressure-resistant property in a tube. 
     It is still another object of disclosure to provide a refrigerant heat exchanger having a high heat exchange property. 
     The present disclosure employs the following technical means, in order to attain the above-mentioned object. The symbols in the parenthesis indicated in the claims and/or this section merely show correspondence relations with concrete elements described in embodiments later mentioned as one example, and are not intended to limit the technical scope of this disclosure. 
     According to one disclosure, a refrigerant heat exchanger which provides a heat exchange between a refrigerant for a refrigeration cycle and a heat exchange medium is provided. The refrigerant heat exchanger has a passage defining member made of carbon fiber reinforced plastics, which provides a tube portion to define a refrigerant passage where the refrigerant of the refrigeration cycle flows. 
     The tube portion, which defines the refrigerant passage, is provided by the member made of carbon fiber reinforced plastics. In the refrigeration cycle, the refrigerant in a pressurized state or in a decompression state flows in the refrigerant passage. Carbon fiber reinforced plastics provide mechanical strength which can bear the pressure difference between the inside and outside of the refrigerant passage. In addition, since the carbon fibers contained in carbon fiber reinforced plastics have high thermal conductivity, it promotes the thermal transfer passing through the member itself. As a result, a lightweight refrigerant heat exchanger is provided. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a block diagram showing a refrigeration cycle according to a first embodiment; 
         FIG. 2  is a frontal view showing a refrigerant heat exchanger; 
         FIG. 3  is a cross sectional view on a line III-III in  FIG. 2  showing a refrigerant heat exchanger; 
         FIG. 4  is a cross sectional view on a line IV-IV in  FIG. 2  showing a refrigerant heat exchanger; 
         FIG. 5  is a perspective diagram showing a plate of a refrigerant heat exchanger; 
         FIG. 6  is an enlarged cross-sectional view showing a passage defining member of a refrigerant heat exchanger; 
         FIG. 7  is a perspective diagram showing the passage defining member of a refrigerant heat exchanger; 
         FIG. 8  is a process diagram showing a manufacturing method of a refrigerant heat exchanger; 
         FIG. 9  is a cross-sectional view showing a passage defining member according to a second embodiment; and 
         FIG. 10  is a partial cross-sectional view showing a refrigerant heat exchanger according to a third embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     A plurality of embodiments is described referring to the drawings. In the embodiments, the same reference number is used for components corresponding to facts which are described in the previous embodiments, and the same descriptions can be referenced for the components. In a consecutive embodiment, reference symbol, in which only hundred and more digits differ from, may be used for components corresponding to facts which are described in the previous embodiments. In a case that only a part of component or part is described, other descriptions for the other embodiment may be referenced or incorporated as descriptions for the remaining part of component or part. 
     First Embodiment 
     In  FIG. 1 , the refrigeration cycle  10  is a thermal-energy mechanism using a heat absorption and/or heat dissipation accompanying a phase change of a refrigerant. The refrigerant may be provided with various refrigerants, such as fluorocarbon system refrigerants and natural refrigerants, such as a carbon dioxide. The refrigeration cycle  10  is a steam compression type refrigeration cycle which produces a phase change by pressuring a refrigerant or decompressing a refrigerant, and produces heat absorption and/or heat dissipation. The refrigeration cycle  10  may be used for an air-conditioner, a cold storage facility, etc. In this embodiment, the refrigeration cycle  10  is used for the air-conditioner for air-conditioning a room of a vehicle. The refrigeration cycle  10  is mounted on the vehicle. Therefore, lightweight is demanded for the refrigeration cycle  10 . 
     The refrigeration cycle  10  has the compressor  11  which compresses a refrigerant. The refrigeration cycle  10  has a radiator  12  which radiate heat from the refrigerant of high temperature and high pressure which is compressed by the compressor  11 . In a case of the refrigerant condenses, the radiator  12  may be also called a condenser. The refrigeration cycle  10  has a decompressing device  13  which decompresses the refrigerant cooled by the radiator  12 . The refrigeration cycle  10  has a heat absorber  14  which make the refrigerant of low temperature and low pressure decompressed by the decompressing device  13  to absorb heat. When the refrigerant evaporates, the heat absorber  14  may be also called an evaporator. 
     Either at least one of the radiator  12  or the heat absorber  14  is used as a using side heat exchanger for air conditioning. The other one of the radiator  12  and the heat absorber  14  functions as an un-using side heat exchanger. For example, when the air-conditioner is used for a cooling application, the heat absorber  14  is used as a using side heat exchanger, in order to cool the medium for air conditioning, for example, air. In this case, the radiator  12  is used in order to discharge a thermal energy as an un-using side heat exchanger. 
     The radiator  12  and the heat absorber  14  are refrigerant heat exchangers in the refrigeration cycle. Since the refrigerant is pressurized or decompressed, the refrigerant heat exchanger is required to have high resistance to pressure. For example, the radiator  12  is required to bear strength withstand against high pressure of an internal refrigerant. The heat absorber  14  is required to bear strength withstand against low pressure of an internal refrigerant. 
     The radiator  12  and the heat absorber  14  are required to demonstrate high heat exchanging performance as heat exchangers. In a case that the medium which performs heat exchange to the refrigerant is air, a refrigerant heat exchanger is required to provide high heat transfer performance between the refrigerant and air. Therefore, the member forming the refrigerant heat exchanger is required to provide high heat transfer performance between the refrigerant and air. 
     In this embodiment, a novel refrigerant heat exchanger which can be used as the radiator  12  and/or the heat absorber  14  for the refrigeration cycle is provided. In this embodiment, a novel refrigerant heat exchanger which can be used as a heat absorber  14  is provided. 
     In  FIG. 2 , the refrigerant heat exchanger  20  provides the heat exchange between the refrigerant in the refrigeration cycle and the air as a heat exchange medium. The refrigerant heat exchanger  20  can be used as the heat absorber  14 . The refrigerant heat exchanger  20  has a heat exchange portion  21  and tank parts  24  and  25 . The heat exchange portion  21  has a plurality of passage defining members  22 . The refrigerant heat exchanger  20  can have support parts for supporting the refrigerant heat exchanger  20  to the air-conditioner. The heat exchange portion  21  of the refrigerant heat exchanger  20  and the tank parts  24  and  25  are made of carbon fiber reinforced plastics (CFRP). The support parts may also be made of CFRP. 
     A plurality of passage defining members  22  define the refrigerant passage where the refrigerant flows. Since the passage defining member  22  defines the tube in which the refrigerant flows, it is also called a tube member. Since the passage defining member  22  has a tabular appearance and defines the refrigerant passage in it, it is also called a heat exchange board. A plurality of passage defining members  22  defines the air passageway  23  in which air flows. A plurality of passage defining members  22  are also heat transfer members which bear the heat transfer between the refrigerant and air. A plurality of passage defining members  22  are arranged in a stacking manner to become parallel each other. A plurality of passage defining members  22  are arranged with predetermined clearances so as to define the air passageways  23  among them. The air passageway  23  is a passage where the air for the air conditioning as a medium to be cooled flows. 
     The tank part  24  is an inlet tank which receives the refrigerant from the decompressing device  13  and distributes the refrigerant to a plurality of passage defining members  22 . An inlet pipe  26  is disposed on the tank part  24 . The tank parts  25  is an exit tank which collects the refrigerant from a plurality of passage defining members  22 , and supplies it to a compressor  11 . An outlet pipe  27  is disposed on the tank part  25 . A plurality of passage defining members  22  are arranged between the tank part  24  and the tank part  25 . A plurality of passage defining members  22  communicates an internal chamber of the tank part  24 , and an internal chamber of the tank part  25 . 
       FIG. 3  shows a cross-section on a line III-III line shown in  FIG. 2 . This cross section illustrates a vertical cross section to the refrigerant flow direction of the passage defining member  22 , i.e., vertical cross section to a longitudinal direction of the passage defining member  22 .  FIG. 4  shows a cross-section on a line IV-IV in  FIG. 2 . 
     The passage defining member  22  has tube portion  31 . The tube portion  31  provides the tube in which the refrigerant flows. The tube portion  31  defines the refrigerant passage inside of the tube portion  31 . The tube portion  31  can have various sectional shapes, such as circular, a long circle, and a polygon. In this embodiment, the tube portion  31  has a circular cross section. One passage defining member  22  may be disposed with one or more tube portions  31 . In this embodiment, three tube portions  31  are disposed in one passage defining member  22 . The tube portion  31  communicates with the internal chamber of the tank parts  24  and  25  on both ends of the passage defining member  22 . The tube portion  31  communicates both the internal chamber of the tank part  24  and the internal chamber of the tank part  25  by the refrigerant passage therein. 
     The passage defining member  22  has plate portions  32  which protrude from the tube portion  31 . A part of the plate portion  32  is disposed on a leading edge of the passage defining member  22  to provide the leading edge of the passage defining member  22  with respect to an air flow direction AF. A part of the plate portion  32  is disposed on a trailing edge of the passage defining member  22  to provide the trailing edge of the passage defining member  22  with respect to the air flow direction AF. A part of the plate portion  32  is disposed between two tube portions  31 . 
     The plate portion  32  protrudes from the tube portion  31  in a spreading manner. The plate portion  32  spreads among a plurality of tube portions  31 . The plate portion  32  connects between two adjoining tube portions  31 . The plate portion  32  spreads over the tank part  24  and the tank part  25 . The plate portion  32  contributes to increase the mechanical strength of the passage defining member  22 . The plate portion  32  is a heat transfer member which is disposed on the outside of the tube portion  31 , and which is a member for widening a contact-surface to air which is the heat exchange medium. The plate portion  32  is provided by the passage defining member  22 , and is made of CFRP. The plate portion  32  contributes to enlarge surface area on which the passage defining member  22  and air contact. The plate portion  32  may also be called a fin portion. 
     The tube portion  31  forms a projection which projects towards the air passageway  23  from the plate portion  32 . In other words, the plate portion  32  forms a recessed portion between two tube portions  31 . Further, the passage defining member  22  which adjoins each other are arranged so that those tube portions  31  may shift with respect to the air flow direction AF. As a result, the air passageway  23  defined between the passage defining members  22  is formed in a winding manner with respect to the air flow direction AF. Such arrangement promotes the heat transfer between the passage defining member  22  and air. 
     A blower of the air-conditioner makes to flow air in the air passageway  23  defined between the passage defining members  22 . Air flows to cross the longitudinal direction of the tube portion  31 . Air flows in parallel with the plate portion  32 . Since the refrigerant heat exchanger  20  is used as the heat absorber  14 , condensed water adheres on an outside surface of the tube portion  31  and the plate portion  32 . In this embodiment, the refrigerant heat exchanger  20  is installed in an air-conditioner so that the plate portion  32  may spread almost in parallel with the gravity direction. Such an installment of the refrigerant heat exchanger  20  promotes draining flow of the condensed water. 
     One passage defining member  22  is formed by stacking plates  33  and  34 . In this embodiment, one passage defining member  22  is formed by stacking and joining two independent plates  33  and  34 . One passage defining member  22  may be formed by bending one plate and joining it. 
     In  FIG. 5 , the first plate  33  and the second plate  34  which form the passage defining member  22  have shapes corresponding to the refrigerant heat exchanger  20 . The plates  33  and  34  are long and narrow shape. In the illustrated example, the plates  33  and  34  may be called a quadrilateral or a rectangle. The plates  33  and  34  are made of CFRP. 
     The plates  33  and  34  have grooved portions  35  for forming the tube portion  31 , and flat plate portions  36  in a flat surfaced shape for forming the plate portion  32 . The grooved portion  35  is dented from the flat plate portion  36  on one surface of the plates  33  and  34 , on the other surface, is projected from the flat plate portion  36 . The plates  33  and  34  have recessed portions  37  and  38  for forming the tank parts  24  and  25 . The recessed portions  37  and  38  are dented from the flat plate portion  36  on one surface of the plates  33  and  34 , on the other surface, are projected from the flat plate portion  36 . Both ends of the grooved portion  35  reach the recessed portions  37  and  38 . Both ends of the grooved portion  35  open toward the recessed portions  37  and  38 . One passage defining member  22  is formed by stacking the plates  33  and  34  face to face. The first plate  33  and the second plate  34  have a symmetrical shape with respect to attaching surfaces of them. 
       FIG. 6  shows modeled cross section of the passage defining member  22 . These plates  33  and  34  contain the resin material and the carbon fibers  41  which constitute CFRP. In the drawing, in order to show the orientation direction of the carbon fibers  41 , a representative carbon fiber  41  is illustrated as a thin solid line in the cross section.  FIG. 7  is a partial cross-sectional and perspective diagram of the passage defining member  22 . In the drawing, in order to show the orientation direction of the carbon fibers  41 , a representative carbon fiber  41  is illustrated as a broken line. The carbon fibers  41  have high thermal conductivity. The carbon fibers  41  have thermal conductivity far higher than the resin material which constitutes CFRP. Therefore, the carbon fibers  41  have large influence on transferring of the thermal energy in the passage defining member  22 . 
     The carbon fibers  41  used in this embodiment are longer than the thickness of the plates  33  and  34 . The carbon fibers  41  has length over from an end to an end of the plates  33  and  34  with respect to a width direction of the plates  33  and  34 , i.e., a direction which intersects perpendicularly with the longitudinal direction of the refrigerant passage which the tube portion  31  provides. The carbon fibers  41  are provided by a cross which wove the carbon fibers. Therefore, the plates  33  and  34  contain the carbon fibers  42  which extend to intersect perpendicularly with the carbon fibers  41 . The carbon fibers  42  are extended along with the longitudinal direction of the tube portion  31 . 
     Alternative to the illustrated example, relatively short carbon fibers may be used. For example, in a case that many short carbon fibers are used, those short carbon fibers are oriented in the same direction of the carbon fibers  41  illustrated. In addition, the carbon fibers  41  may be arranged only in the single direction. 
     In the tube portion  31 , the carbon fibers  41  are oriented to extend to surround the refrigerant passage. In the illustrated example in which the tube portion  31  has a circular cross sectional shape, the carbon fibers  41  are oriented to extend along a circumferential direction of the tube portion  31 . In other words, in the cross section vertical to the longitudinal direction of the refrigerant passage which the tube portion  31  provides, the carbon fibers  41  are oriented to extend in parallel to the cross section. Such orientation of the carbon fibers  41  contributes to increase the pressure resistance with respect to the radial direction in the tube portion  31 . 
     In the plate portion  32 , the carbon fibers  41  are oriented to extend in a direction which intersects the longitudinal direction of the refrigerant passage which the tube portion  31  provides, for example, the direction which intersects perpendicularly. Such orientation promotes the heat conduction in the plate portion  32 , and contributes to suppress the temperature distribution in the plate portion  32 . 
     In the plate portion  32 , the carbon fibers  41  are oriented to protrude from the tube portion  31 . The carbon fibers  41  are extended in an inside of the plate portion  32  to protrude from the tube portion  31 . This orientation may contribute to promote the thermal transfer between the tube portion  31  and the plate portion  32 . 
     In addition, the carbon fibers  41  are extended over both the tube portion  31  and the plate portion  32  in a continuous manner. Utilization of such long carbon fibers  41  and/or such orientation of the carbon fibers  41  promote further the thermal transfer between the tube portion  31  and the plate portion  32 . 
     In the plate portion  32 , the carbon fibers  41  are extended to connect between two adjoining tube portions  31 . Such the orientation improves the mechanical strength with respect to the width direction of the passage defining member  22 . The carbon fibers  41  is extended over the overall width of the passage defining member  22  along with the air flow direction AF of air which is a heat exchange medium. The carbon fibers  41  are extended over all the plurality of the tube portions  31  and the plurality of the plate portions  32 . 
     Above explained orientation of the carbon fibers  41  in the tube portions  31  and/or the plate portions  32  make it possible to make thickness of the passage defining member  22  thin. The thin passage defining member  22  makes the refrigerant heat exchanger  20  possible to become lightweight. In addition, the thin passage defining member  22  promotes further the thermal transfer between the refrigerant and air. 
       FIG. 8  shows main processes in a manufacturing method of the refrigerant heat exchanger  20 . The manufacturing method of the refrigerant heat exchanger  20  has process described below. The first process A is a process of supplying a raw material for the plates  33  and  34 . At this process, a prepreg for CFRP is supplied. Prepreg is supplied where impregnation of the resin material is carried out to carbon fibers. Prepreg, resin material is selected to have the workability and the cure characteristic which are suitable for consecutive process. Thermosetting resin or thermoplastic resin may be used for the resin material of prepreg. Prepreg is supplied as a roll material  51 . 
     The second process B is a process of processing a raw material into the shape of the plates  33  and  34 . At this process, prepreg is cut into a predetermined scale and is given a predetermined shape. Prepreg is formed into a shape corresponding to the plates  33  and  34 . For example, the shape of the plates  33  and  34  is formed by pressing work using a pressing machine  52 . 
     The third process C is a process of arranging a plurality of plates  33  and  34  in a stacking manner so that the refrigerant heat exchanger  20  may be formed. At this process, a plurality of plates  33  and  34  are stacked regularly. At this process, a set of symmetrical plates  33  and  34  are stacked each other for one passage defining member  22 . And then at this process, two or more sets of plates  33  and  34  for forming the refrigerant heat exchanger  20  are stacked. The fourth process D is a process which joins the plates  33  and  34  and stiffens prepreg. 
     The carbon fibers  41  may be obtained as “PYROFIL” which Mitsubishi Rayon Co., Ltd. sells. The carbon fibers  41  may be obtained as UD tape in which fibrous direction is a uni-directional manner, a fabric sheet as a fabric, or discontinuous base material, such as chopped fibers. The carbon fibers  41  may be obtained as a “TORAYCA” which Toray Industries, Inc. sells. The carbon fibers  41  may be obtained as UD tape in which fibrous direction is a uni-directional manner, a fabric sheet as a fabric, or discontinuous base material, such as cut fibers or short fiber pellets. The carbon fibers  41  may be obtained as “DIALEAD” which Mitsubishi 
     Plastics Inc. sells. The carbon fibers  41  may be obtained as UD tape in which fibrous direction is a uni-directional manner, a fabric sheet as a fabric, or discontinuous base material, such as chopped fibers, short fiber pellets, or milled fibers which are grounded a fiber into short. 
     When UD tape or a fabric seat is used, prepreg is provided by impregnating the resin material to the carbon fibers  41  of which the longitudinal direction is positioned in a direction required as the plates  33  and  34 . When the discontinuous base material called chopped fibers, cut fibers, or short fiber pellets are used, the plates  33  and  34  are formed by injection molding by using the resin material with which the discontinuous base material is mixed. In this case, the carbon fibers are oriented along the direction of flow of the resin material in the injection molding process. Therefore, location of gates in the injection molding mold is set so that a resin material may flow in a direction which intersects the longitudinal direction of the tube portion  31 . 
     When thermosetting resin is used as a resin material to be impregnated the carbon fibers  41 , the manufacturing method process may use a vacuum heat pressing process by an autoclave, a resin injection forming process called an RTM (Resin Transfer Molding) process, or a suction type resin injection forming step called a VaRTM (Vacuum Resin Transfer Molding) process. In addition, when thermoplastic resin is used as a resin material to be impregnated the carbon fibers  41 , a stamp-press process (Stamping Molding) or an injection molding process (Injection Molding) may be used for the manufacturing method process. 
     According to this embodiment, since CFRP is used for the passage defining member  22  which is a refrigerant passage forming member of the refrigerant heat exchanger  20 , a refrigerant passage forming member can be formed thin and lightweight. As a result, a lightweight refrigerant heat exchanger is provided. According to this embodiment, the carbon fibers  41  are oriented to surround the tube portion  31 . Accordingly, the refrigerant heat exchanger which has high pressure resisting performance is provided with respect to the radial direction of the tube portion  31 . According to this embodiment, in the plate portion  32 , the carbon fibers  41  are oriented to protrude from the tube portion  31 . Accordingly, the refrigerant heat exchanger which has high heat exchanging performance between the refrigerant in the tube portion  31  and the medium on the outside of the plate portion  32  is provided. 
     Second Embodiment 
     This embodiment is a modification based on a basic form provided by the preceding embodiment. In the preceding embodiment, the tube portion  31  defines the refrigerant passage in the circular sectional shape. Alternatively, the passage defining member  22  may be formed to define refrigerant passages which have various sectional shapes. 
     As shown in  FIG. 9 , the passage defining member  22  of this embodiment have a tube portion  231 . The tube portion  231  defines the refrigerant passage having a sectional shape which may be called a rectangle or an ellipse. According to this embodiment, the contact surface of the refrigerant and plates  33  and  34  is formed over wide area. In addition, a flat shaped area over a large area is disposed on the outer surface of the passage defining member  22 . Such a shape makes it possible to provide a heat exchanging performance which suited the application of the refrigerant heat exchanger  20 . 
     Third Embodiment 
     This embodiment is a modifications based on a basic form provided by the preceding embodiment. In the preceding embodiments, the refrigerant heat exchangers  20  may belong to the types called the stacked plate type or the drawn cup type. Alternatively, the refrigerant heat exchanger  20  may be provided by various types. 
     The refrigerant heat exchanger  20  illustrated in  FIG. 10  belongs to a type called the tube and header type. One application of the refrigerant heat exchanger  20  illustrated is the radiator  12 . 
     The refrigerant heat exchanger has a passage defining member  322 . Also this embodiment, the passage defining member  322  forms the refrigerant passage where the refrigerant flows. The passage defining member  322  does not have the recessed portions  37  and  38  and the peripheral portions among the passage defining members  22  of the preceding embodiments, but has only portions corresponding to the tube portion  31  and the plate portion  32 . Therefore, the passage defining member  322  is formed to provide the refrigerant passage mainly. In this embodiment, the air passageway  23  is formed among a plurality of passage defining members  322  too. Fin  328  thermally connected to the passage defining member  322  is arranged in the air passageway  23 . The fin  328  is a heat transfer member which is disposed on the outside of the tube portion  31  and which widens a contact-surface with the air which is a heat exchange medium. The fin  328  is a member other than the passage defining member  322 . 
     In the illustrated example, the fin  328  is provided by a wavelike member called a corrugate fin. The fin  328  is made of material which is possible to join to the passage defining member  322  made of CFRP in a thermally and mechanically manner. The fin  328  is made of CFRP. In a case of joining the fin  328  to the passage defining member  22 , the fin  328  may be made of metal, such as aluminum. 
     The refrigerant heat exchanger  20  has header tanks  324  and  325  to which the ends of a plurality of passage defining members  322  are fluidly communicated. The header tanks  324  and  325  are made of metal, such as aluminum, or made of CFRP. The passage defining member  22  communicates the refrigerant chamber defined within the header tanks  324  and  325 . 
     Other Embodiments 
     The present disclosure is not limited to the above embodiments, and the present disclosure may be practiced in various modified embodiments. The present disclosure is not limited to the above combination, and disclosed technical means can be practiced independently or in various combinations. Each embodiment can have an additional part. The part of each embodiment may be omitted. Part of embodiment may be replaced or combined with the part of the other embodiment. The configurations, functions, and advantages of the above-mentioned embodiments are just examples. Technical scope of disclosure is not limited to the embodiments. It should be understood that some disclosed technical scope may be shown by description in the scope of claim, and contain all modifications which are equivalent to and within description of the scope of claim. 
     In the preceding embodiment, the carbon fibers  41  are disposed in whole of the passage defining member  22 . Alternatively, the carbon fibers  41  may be disposed in a part of the passage defining member  22 . For example, the carbon fibers  41  may be disposed in a part being required to have high mechanical strength, and/or a part which needs high thermal transfer nature. Further, in addition to the above-mentioned embodiments, it may be possible to add additional carbon fibers to a part being required to have high mechanical strength, and/or a part which needs high thermal transfer nature.