Patent Publication Number: US-2019181474-A1

Title: Fuel cell apparatus

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a national stage entry according to 35 U.S.C. 371 of PCT Application No. PCT/JP2017/028901 filed on Aug. 9, 2017, which claims priority to Japanese Application Nos. 2016-158257 filed on Aug. 10, 2016, and 2017-072854 filed on Mar. 31, 2017, which are entirely incorporated herein by reference. 
    
    
     TECHNICAL FIELD 
     The present disclosure relates to a fuel cell apparatus. 
     BACKGROUND 
     In recent years, as next-generation energy sources, there have been proposed various fuel cell modules of the type that may include a cell stack, which is housed in a housing, may include a plurality of stacked fuel cells capable of obtaining electric power by utilizing a fuel gas (hydrogen-containing gas) and air (oxygen-containing gas), and also fuel cell apparatuses each of which may include such a fuel cell module housed in an exterior case. 
     There is another proposal as to a fuel cell apparatus, which may include a heat storage tank, in which a heat exchanger carries out heat exchange between exhaust gas from a fuel cell module and a medium, such as water, to cool the exhaust gas for recovery and reuse of water contained in the exhaust gas, and also the heat recovered by the medium may be utilized for the supply of hot water. 
     Moreover, there is discussion of a technique to supply a medium to a heat exchanger after lowering the temperature of the medium by a heat dissipator disposed between a heat-storage tank and the heat exchanger. For example, Japanese Unexamined Patent Publication JP-A 2009-38015 (Patent Literature 1) discusses a construction in which an exterior case may have an air inlet provided in one surface thereof and an air outlet provided in the opposite surface thereof, and, Japanese Unexamined Patent Publication JP-A 2015-72090 (Patent Literature 2) discusses a construction in which an exterior case may have an air inlet and an air outlet for a heat dissipator provided in one and the same surface thereof. 
     Furthermore, with regard to exhaust air flow control in a heat dissipator, for example, Japanese Unexamined Patent Publication JP-A 2010-92775 and Japanese Unexamined Patent Publication JP-A 2016-217670 (Patent Literatures 3 and 4) discuss a fuel cell apparatus that may have an air flow channel such as a duct. 
     SUMMARY 
     A fuel cell apparatus according to a non-limiting aspect of the present disclosure may include: a fuel cell module; a heat exchanger which carries out heat exchange between exhaust gas from the fuel cell module and a medium; a circulation line connected to the heat exchanger, the circulation line allowing the medium to circulate through the heat exchanger; a heat dissipator located in the circulation line, the heat dissipator cooling the medium flowing through the heat exchanger; and an exterior case which houses the fuel cell module, the heat exchanger, the heat dissipator, and at least part of the circulation line. 
     The heat dissipator may be provided with two openings. The heat dissipator may include a duct which defines an air flow channel between the two openings; a fan located closer to a first opening of the two openings than a second opening of the two openings in the air flow channel, the fan producing flowing air; and a radiator located closer to the second opening than the first opening in the air flow channel, the radiator carrying out heat exchange between the medium and air flowing through an interior of the air flow channel. 
     The exterior case may be provided with two ventilation holes to which the two openings are connected directly or via an air passageway, respectively, and the duct may include a plurality of separable parts. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       Other and further objects, features, and advantages of the invention will be more explicit from the following detailed description taken with reference to the drawings wherein: 
         FIG. 1  is a block diagram showing the structure of an example of a fuel cell apparatus according to a non-limiting aspect of the present disclosure; 
         FIG. 2  is a perspective view showing the appearance of an example of the fuel cell apparatus according to a non-limiting aspect of the present disclosure; 
         FIG. 3  is one side view of an example of the fuel cell apparatus according to a first non-limiting embodiment; 
         FIG. 4  is another side view of an example of the fuel cell apparatus according to the first non-limiting embodiment; 
         FIG. 5A  is an exploded perspective view showing a specific example of a heat dissipator of the first non-limiting embodiment; 
         FIG. 5B  is an exploded perspective view showing a specific example of the heat dissipator of the first non-limiting embodiment; 
         FIG. 6A  is a view schematically showing the heat dissipator of the first non-limiting embodiment; 
         FIG. 6B  is a view schematically showing the heat dissipator of the first non-limiting embodiment; 
         FIG. 7A  is an explanatory view of a structural example of a radiator duct of the first non-limiting embodiment; 
         FIG. 7B  is an explanatory view of a structural example of the radiator duct of the first non-limiting embodiment; 
         FIG. 8  is a side view of an example of a fuel cell apparatus according to a second non-limiting embodiment; 
         FIG. 9  is a side view of an example of the fuel cell apparatus according to the second non-limiting embodiment; 
         FIG. 10  is an explanatory view of a structural example of a heat dissipator of the fuel cell apparatus according to the second non-limiting embodiment; 
         FIG. 11  is an explanatory view of another structural example of the heat dissipator of the fuel cell apparatus according to the second non-limiting embodiment; 
         FIG. 12  is an explanatory view of another structural example of the heat dissipator of the fuel cell apparatus according to the second non-limiting embodiment; 
         FIG. 13  is an explanatory view of another structural example of the heat dissipator of the fuel cell apparatus according to the second non-limiting embodiment; 
         FIG. 14  is a schematic sectional view of the heat dissipator of the fuel cell apparatus shown in  FIG. 13 ; and 
         FIG. 15  is a schematic sectional view of the heat dissipator of the fuel cell apparatus shown in  FIG. 13 . 
     
    
    
     DETAILED DESCRIPTION 
     Disposing a heat dissipator in a lower part of a fuel cell apparatus causes complications in maintenance operation. Thus, ease of maintenance has been demanded in a heat dissipator which is located in a fuel cell apparatus. The following describes fuel cell apparatuses according to non-limiting embodiments of the disclosure in sequence. 
     First Non-Limiting Embodiment 
       FIG. 1  is a block diagram showing the structure of an example of a fuel cell apparatus according to the present disclosure. Throughout the drawings to be hereafter referred to, the same reference numerals or symbols designate corresponding or identical constituent components. A fuel cell apparatus  1  according to the first non-limiting embodiment includes a reformer  10 , a cell stack device  20 , a heat exchanger  30 , a heat-storage tank  40 , a heat dissipator  50 , and a condensed water tank  60 . Each such constituent device is, together with auxiliary machines which operate a fuel cell module  91  as described later, housed in an exterior case, not shown. It is not necessary to house all of the aforenamed devices in the exterior case, and for example, the heat-storage tank  40  and the heat exchanger  30  may be disposed outside the exterior case. Moreover, the fuel cell apparatus in which apart of the aforenamed devices is omitted is also possible. 
     A raw fuel supply pipe  100  which supplies a raw fuel and a water supply pipe  101  which supplies reformed water are connected to the reformer  10 . Inside the heated reformer  10 , the raw fuel and the reformed water undergo reforming reactions with each other to produce a hydrogen-containing reformed gas. The reformed gas produced in the reformer  10  is supplied to the cell stack device  20  through a reformed gas supply pipe  102 . 
     The cell stack device  20  includes a manifold  21  and a cell stack  22 . the reformed gas supplied to the cell stack device  20  is supplied from the manifold  21  into the cell stack  22 . In the cell stack device  20 , air (oxygen-containing gas) is introduced from an oxygen-containing gas supply member  103  outside the cell stack  22 . When passing through the interior of the cell stack  22 , the reformed gas reacts with this air to carry out power generation. In a region above the cell stack  22 , reformed gas left unused for power generation merges with air left unused for power generation, and the resulting confluent flow is burned to produce high-temperature exhaust gas. Moreover, the reformer  10  is heated under heat resulting from the combustion. 
     The reformer  10  and the cell stack device  20  are brought into high-temperature conditions, and are encased by a heat-insulating material and are placed inside the exterior case as the fuel cell module  91 . 
     Exhaust gas generated in the fuel cell module  91  is discharged from the cell stack device  20 , and is then supplied to the heat exchanger  30  through an exhaust gas flow channel  104 . A circulation line  105  is connected to the heat exchanger  30  to carry out heat exchange between the exhaust gas and a medium introduced in the circulation line  105 . As the medium, it is possible to use a non-freezing liquid containing ethylene glycol, etc., or water. Under the heat exchange, the exhaust gas is cooled, whereas the medium is heated by the heat of the exhaust gas. Due to the cooling of the exhaust gas, water vapor contained in the exhaust gas becomes water, with consequent occurrence of vapor-liquid separation. The separated gas is discharged through an exhaust channel  107  from a gas exhaust outlet externally. The water separated by the cooling of the exhaust gas is delivered through a condensed water recovery channel  106  to the condensed water tank  60 . In the condensed water tank  60 , the water is purified into pure water through an ion exchange process or otherwise. The pure water is introduced into the water supply pipe  101 , and is then supplied, as reformed water, to the reformer  10 . Unnecessary water is ejected from a drain  109 . 
     The medium is circulated successively through the heat-storage tank  40 , the heat dissipator  50 , and the heat exchanger  30  in the order named. The medium is stored in the heat-storage tank  40 . After being delivered from the heat-storage tank  4  to the heat dissipator  50 , the medium is cooled, and then supplied to the heat exchanger  30 . In the heat exchanger  30 , the medium is heated by heat exchange with the exhaust gas. The medium having an elevated temperature is returned to the heat-storage tank  40 . 
     That is, there is formed the circulation line  105  in which the medium is circulated successively through the heat-storage tank  40 , the heat dissipator  50 , and the heat exchanger  30  in the order named. In other words, the heat-storage tank  40 , the heat dissipator  50 , and the heat exchanger  30  are disposed successively in the order named along the circulation line  105 . 
     A hot water supply piping is introduced in the heat-storage tank  40  to utilize heated water resulting from heat exchange between water delivered from a water supply pipe  108  and the medium stored in the heat-storage tank  40  as hot water. Where water is used as the medium, the fuel cell apparatus may be configured so as to supply the medium as hot water per se. 
     When the amount of heat accumulated in the heat-storage tank  40  reaches the upper limit (full heat storage state), the medium is no longer able to recover the heat of the exhaust gas in the heat exchanger  30 , and consequently the exhaust gas cannot be cooled sufficiently, causing a failure in the separation of moisture from the exhaust gas. As a result, a failure in condensation of moisture contained in the exhaust gas may lead to a shortage of water which is supplied to the reformer  10 . Accordingly, it is necessary to decrease the temperature of the medium which is supplied to the heat exchanger  30 . In the fuel cell apparatus  1  according to the present non-limiting embodiment, the medium is cooled by the heat dissipator  50  and to then supplied to the heat exchanger  30 . The heat dissipator  50  includes a radiator  51  and a fan  52 . When the medium is at a high temperature, the fan  52  is actuated to facilitate dissipation of heat from the medium passing through the interior of the radiator  51 . On the other hand, when the medium is at a low temperature, the fan  52  is left unactuated to restrain dissipation of heat from the medium in the heat dissipator  50 . 
       FIG. 2  is a perspective view showing the appearance of an example of the fuel cell apparatus according to the present disclosure. In  FIG. 2 , for purposes of explanation of the interior of the fuel cell apparatus, there is shown the fuel cell apparatus with the exterior case (more specifically, four side panels, a top panel, etc. constituting the outer frame of the fuel cell apparatus) removed. In the following description, the side panel will be also referred to simply as “side”. For purposes of convenience, a face of the fuel cell apparatus as viewed in the direction of arrow A (or equivalently a y direction) in  FIG. 2  is defined as a front face of the fuel cell apparatus  50 . Moreover, a rightward direction as viewed from the front face is defined as an x direction, and a height direction is defined as a z direction. In the fuel cell apparatus  1 , the heat dissipator  50  is disposed below the fuel cell module  91 , and, the heat-storage tank  40  is disposed on a lateral side of the fuel cell module  91  and the heat dissipator  50 . 
     Moreover, a control board  93  for controlling the fuel cell apparatus  1  is disposed on a lateral side of the fuel cell module  91 , and, a power conditioner  94  for supplying electric power produced by the fuel cell module  91  to outside is disposed on a lateral side of the heat-storage tank  40 . In addition, an auxiliary machine  70  such as a fuel pump is disposed above the fuel cell module  91  to operate the fuel cell module  91 . One or more auxiliary machines  70  are disposed inside a space indicated by a dotted line. The description of the specific configuration of the auxiliary machine will be omitted. 
     The heat dissipator  50  includes a narrow piping of the radiator  51  through which the medium passes (refer to  FIGS. 5A and 5B ). Disposing the heat dissipator  50  below the fuel cell module  91  enables protection of the fuel cell module  91  from trouble such as liquid leakage from the radiator. Moreover, disposing the heat dissipator  50  below the control board  93  and the power conditioner  94  enables protection of the control board  93  and the power conditioner  94  from trouble such as liquid leakage from the radiator. In addition, disposing the heat dissipator  50  below the fuel cell module  91  enables introduction of external air having a relatively low temperature, and thus can enhance the heat-dissipation efficiency. 
       FIG. 3  is one side view of an example of the fuel cell apparatus according to the present non-limiting embodiment, illustrating a side face  81  of an exterior case  80  having longitudinal sides.  FIG. 4  is the other side view of an example of the fuel cell apparatus according to the present non-limiting embodiment, illustrating a side face  83  of the exterior case  80  opposite to the side face  81 . As shown in  FIG. 3 , the exterior case  80  for housing devices constituting the fuel cell apparatus  1  is shaped in a rectangular prism. In a lower side opening  81   a  of the side face  81  of the exterior case  80 , an air inlet  54  and the radiator  51  of the heat dissipator  50  are disposed. On the other hand, as shown in  FIG. 4 , in a lower side opening  83   a  of the side face  83  of the exterior case  80 , an air outlet  55  and the fan  52  of the heat dissipator  50  are disposed. 
     As shown in  FIGS. 3 and 4 , an opening area of the air inlet  54  is larger than an opening area of the air outlet  55 . This makes it possible to increase the amount of air which is introduced from the air inlet  54 , and thereby efficiently cool the medium flowing through the interior of the piping of the radiator  51 . Moreover, forming the air inlet  54  in the large-area side face  81  allows the air inlet  54  to have a large opening area. In addition, an opening area of the opening  81   a  connected with the air inlet  54  can be larger than an opening area of the opening  83   a  connected with the air outlet  55 . 
     As described above, the fuel cell module  91  indicated by a broken line is disposed above the heat dissipator  50  to avoid any trouble associated with the heat dissipator  50 , as well as to achieve an improvement in heat-dissipation efficiency in the heat dissipator  50 . The heat-storage tank  40  is disposed adjacent to the fuel cell module  91 . 
       FIGS. 5A and 5B  are each an exploded perspective view showing a specific example of the heat dissipator of the present non-limiting embodiment. The heat dissipator  50  includes the radiator  51 , the fan  52 , an air flow channel  53 , and a radiator duct (hereafter also referred to simply as “duct”)  59 . The duct  59 , in the form of a frame body that defines the air flow channel  53 , includes a plurality of separable parts. Thus, it is possible to achieve good maintainability. Moreover, for example, the duct  59  is made of resin and is thus lighter in weight than a metal-made duct. This facilitates duct servicing and maintenance. 
     The duct  59  shown in  FIG. 5A  includes an upper duct  59 A and a lower duct  59 B. In  FIG. 5A , the upper duct  59 A is illustrated as being separated from the lower duct  59 B. By designing the duct  59  so that the upper duct  59 A can be separated from the lower duct  59 B, it is possible to achieve good maintainability. 
       FIG. 5B  shows a case where the upper duct  59 A includes a first duct  59 A 1  which is separable from the upper duct  59 A. By designing the duct  59  so that the first duct  59 A 1  can be separated from the upper duct  59 A, it is possible to achieve good maintainability for the fan  52 , etc. located below the first duct  59 A 1 . 
       FIGS. 6A and 6B  are each a view schematically showing the heat dissipator of the present non-limiting embodiment.  FIG. 6A  is an explanatory view of a structural example of the heat dissipator of the present non-limiting embodiment, illustrating the structure of the heat dissipator  50  disposed over the bottom face of the exterior case  80 , as seen in a plan view. 
     Upon actuation of the fan  52  of the heat dissipator  50 , air is introduced from the air inlet  54  connected to the opening  81   a  formed in the side face  81  under negative pressure, and, the medium flowing through the interior of the piping is cooled when the air passes through the radiator  51 . After passing through the radiator  51 , the air passes through the air flow channel  53  and the fan  52 , and is eventually discharged from the air outlet  55  connected to the opening  83   a  formed in the side face  83 . 
     The air flow channel  53 , which is defined by the duct  59 , may be communicated with other portions in the exterior case  80 . In this case, by the operation of the fan  52 , in addition to air present in the heat dissipator  50 , air present in portions other than the heat dissipator  50  in the exterior case  80  can be discharged. 
       FIG. 6B  is a plan view showing the positional relationship between the heat dissipator of the present non-limiting embodiment and other devices. As shown in  FIG. 6B , in the heat dissipator  50  as seen in a transparent plan view, the first duct  59 A 1  lies outside the range of the fuel cell module  91 . The first duct  59 A 1  constitutes part of the upper duct  59 A. The first duct  59 A 1  is separable from the upper duct  59 A, and it is thus possible to facilitate replacement of the fan  52  located below the first duct  59 A 1 . 
       FIGS. 7A and 7B  are each an explanatory view of a structural example of the radiator duct of the present non-limiting embodiment.  FIG. 7A  shows a case where part of the upper duct  59 A is constituted by the first duct  59 A 1  as described above with reference to  FIG. 6B .  FIG. 7B  shows another case where a first duct  59 C is disposed independently of the upper duct  59 A and the lower duct  59 B. In this structure, during maintenance operation, the first duct  59 C can be separated completely from the upper duct  59 A and the lower duct  59 B, and it is thus possible to achieve good maintainability. 
     Second Non-Limiting Embodiment 
     The following describes a fuel cell apparatus  11  according to a second non-limiting embodiment. Each constituent device of the fuel cell apparatus  11  is designed basically as is shown in the block diagram of  FIG. 1  and the perspective view of  FIG. 2 , and thus overlapping descriptions will be omitted. 
     Moreover, the function of a heat dissipator  150  of the second non-limiting embodiment is identical with that of the heat dissipator  50  of the foregoing first non-limiting embodiment except for the shape of the air flow channel (refer to  FIG. 10 , for example). Thus, the detailed description of the heat dissipator  150  will be omitted. 
       FIG. 8  is a side view of an example of the fuel cell apparatus according to the present non-limiting embodiment, illustrating a side face of an exterior case  80  having longitudinal sides.  FIG. 9  is a side view of an example of the fuel cell apparatus according to this non-limiting embodiment, illustrating a side face of the exterior case  80  having transverse sides. The exterior case  80  for housing devices constituting the fuel cell apparatus  11  is also shaped in a rectangular prism. An area of the side face  81  of the exterior case  80  is larger than an area of the side face  82  of the exterior case  80  contiguous to the side face  81 . 
     An air inlet  154  of the heat dissipator  150  is connected directly to an opening  181   a  formed in the large-area side face  81  so as to extend along the lower side of the side face  81 , and, a radiator  151  is disposed in the air inlet  154 . 
     An air outlet  155  of the heat dissipator  150  is connected directly to an opening  182   a  formed in the small-area side face  82  so as to extend along the lower side of the side face  82 , and, a fan  152  is disposed in the air outlet  155 . 
     The air inlet  154  and the air outlet  155  have been illustrated as being connected directly to the opening  181   a  and the opening  182   a  formed in the side face  81  and the side face  82 , respectively. Also in cases where the air inlet  154  and the air outlet  155  are connected to their respective openings via air flow channels as described later, in the present non-limiting embodiment, the air inlet  154  makes connection with the opening  181   a  formed in the side face  81 , and the air outlet  155  makes connection with the opening  182   a  formed in the side face  82 . 
     The relationship in opening area between the air inlet  154  and the air outlet  155  is similar to the earlier described relationship in opening area between the air inlet  54  and the air outlet  55 , and will thus not be described hereinbelow. 
     In setting such a rectangular prism-shaped fuel cell apparatus, especially in a residential house, in most cases, the fuel cell apparatus is oriented so that the large-area side face  81  is located substantially parallel to a house wall. With the side face  81  located substantially parallel to the house wall, the contiguous side face  82  faces into open space correspondingly, thus enabling safe and effective exhaust from the air outlet  55  provided in the side face  82 . Moreover, owing to the side face  82  facing into open space, maintainability can be improved. 
       FIG. 10  is an explanatory view of a structural example of the heat dissipator of the fuel cell apparatus according to the present non-limiting embodiment, illustrating the structure of the heat dissipator  150  disposed over the bottom face of the exterior case  80 , as seen in a plan view. The heat dissipator  150  includes the radiator  151 , the fan  152 , and an air flow channel  153 . 
     The operation of the fan  152  is identical with that of the earlier described fan  52  except that air that has passed through the radiator  151  passes through the fan  152  along the air flow channel  153  with a 90° turn. Thus, the description of the fan  152  will be omitted. 
     While the air flow channel  153  is defined by, in addition to a partition wall plate, for example, the outer wall of a constituent device disposed around the heat dissipator, these wall portions are not intended to isolate the air flow channel  153  completely from other portions than the heat dissipator. Thus, the air flow channel  153  may be communicated with other portions in the exterior case  80 . In this case, by the operation of the fan  152 , in addition to air present in the heat dissipator  150 , air present in portions other than the heat dissipator  150  in the exterior case  80  can be discharged. Where the air flow channel  153  is provided separately from other portions in the exterior case  80  for the purpose of cooling auxiliary machines, etc. mounted in the exterior case  80 , an additional fan may need to be provided to ventilate the interior of the exterior case  80 . In this regard, in the present non-limiting embodiment, discharge of air from both of the heat dissipator  150  and other portions in the exterior case  80 , as well as replenishment of fresh air into both of them, can be carried out by a single fan  152 . This eliminates the need to provide such an additional fan as above described, and thus reduces the number of fans in the fuel cell apparatus, with consequent downsizing of the fuel cell apparatus. 
     That is, as shown in  FIG. 10 , in the heat dissipator  150  of the present non-limiting embodiment, the air inlet  154  is provided so as to make connection with the opening  181   a  provided in the side face  81  which is one side face of the exterior case  80 . Moreover, the air outlet  155  is provided so as to make connection with the opening  182   a  provided in the side face  82  which is the other face of the exterior case  80  contiguous to the side face  81 . This arrangement reduces the size of the heat dissipator  150 , and thus makes it possible to downsize the fuel cell apparatus. 
     Moreover, as shown in  FIG. 10 , the air inlet  154  is provided so as to make connection with the opening  181   a  provided in the side face  81  of the exterior case  80 , and, the air outlet  155  is provided so as to make connection with the opening  182   a  provided in the side face  82  contiguous to the side face  81 . In this case, even when the air inlet  154  faces windward, the air flow channel  153  bent in an L- or V-form constitutes resistance, and consequently external air is restrained from flowing to the interior through the air inlet  154 . Consequently, since the medium flowing through the radiator  151  is not overcooled, it is possible to reduce deterioration in heat-storage performance in the heat-storage tank  40 . 
     If the air inlet and the air outlet are provided so as to make connection with their respective openings provided in one common side face of the exterior case and to be located close to each other, for example, discharged air may flow into the air inlet once again, causing the efficiency of the heat dissipator to fall off. In this regard, by providing the air inlet  154  and the air outlet  155  so as to make connection with the opening  181   a  and the opening  182   a,  respectively, provided in different side faces contiguous to each other, the location for air introduction and the location for air discharge are separated from each other, and therefore it is possible to prevent a decrease in the cooling efficiency of the heat dissipator. 
     Moreover, an opening area of the air inlet  154  may be larger than an opening area of the air outlet  155 . In addition, an opening area of the opening  181   a  connected with the air inlet  154  may be larger than an opening area of the opening  182   a  connected with the air outlet  155 . This makes it possible to ensure the heat-dissipation capability of the radiator  151  located near the air inlet  154 , and to reduce the size of the fan  152  located near the air outlet  155 . 
       FIG. 11  is an explanatory view of another structural example of the heat dissipator of the fuel cell apparatus according to the present non-limiting embodiment. Where the heat dissipator  150  is disposed on an inward side of the fuel cell apparatus, the air inlet  154  is connected, through an air passageway  183 , to the opening  181   a  provided in the side face  81 , and, the air outlet  155  is connected, through an air passageway  184 , to the opening  182   a  provided in the side face  82 . This arrangement affords the same advantageous effects as achieved by the arrangement shown in  FIG. 10 . 
       FIG. 12  is an explanatory view of still another structural example of the heat dissipator of the fuel cell apparatus according to the present non-limiting embodiment. As a point of difference from the arrangement shown in  FIG. 10 , an auxiliary machine  171  is disposed in the air flow channel  153  of the heat dissipator  150 . Some of a plurality of auxiliary machines housed in the exterior case  80  include devices which get hot easily and thus exhibit high reliability when cooled, such as pumps. At least part of the plurality of auxiliary machines is disposed in the air flow channel  153  connecting the air inlet  154  and the air outlet  155 . Thereby, it is possible to cool the mounted auxiliary machine  171  render the auxiliary machine highly reliable, and enhance the reliability of the fuel cell apparatus. 
       FIG. 13  is an explanatory view of yet another structural example of the heat dissipator of the fuel cell apparatus according to the present non-limiting embodiment.  FIG. 14  is a schematic sectional view of the heat dissipator of the fuel cell apparatus shown in  FIG. 13  taken along the section line A-A of  FIG. 13 . Moreover,  FIG. 15  is a schematic sectional view of the heat dissipator of the fuel cell apparatus shown in  FIG. 13  taken along the section line B-B of  FIG. 13 . The present non-limiting embodiment differs from the above-described fuel cell apparatus  10  shown in  FIG. 10  in respect of the shape of the bottom face of the heat dissipator. In  FIGS. 14 and 15 , the cross-hatched area located outside the air flow channel  153  indicates a space where the fuel cell module  91 , the auxiliary machine  70 , etc. are disposed. The wall face of the air flow channel  153  is defined by a partition plate such as a metallic plate or part of the enclosures of devices mounted around the heat dissipator  150 . 
     The air inlet  154  is provided so as to make connection with the opening  181   a  provided in the side face  81  of the exterior case  80 , and, the air outlet  155  is provided so as to make connection with the opening  182   a  provided in the side face  82  contiguous to the side face  81 . The air flow channel  153  connecting the air inlet  154  and the air outlet  155  is bent in an L-form in the exterior case  80 . The bottom face of the air flow channel  153  defined by a metal-made partition plate, etc. includes a bottom face  156   a  opposed to the air inlet  154  and a bottom face  156   b  opposed to the air outlet  155 . 
     Above the bottom face  156   a  opposed to the opening  181   a  (hereafter also referred to as the air inlet  154  in the following non-limiting embodiment), the radiator  151  is disposed. The bottom face  156   a  slopes downwardly from an inward side of the air flow channel  153 , for example, the bend of the L-shaped air flow channel  53 , toward the air inlet  154 . Moreover, above the bottom face  156   b  opposed to the opening  182   a  (hereafter also referred to as the air outlet  155  in the following non-limiting embodiment), the fan  152  is disposed. The bottom face  156   b  slopes downwardly from an inward side of the air flow channel  153 , for example, the bend of the L-shaped air flow channel  153 , toward the air outlet  155 . 
     In forming the bottom faces sloping downwardly toward the openings  181   a  and  182   a,  respectively, it is sufficient that each bottom face be free from any upward incline on its way to the opening. That is, for example, the bottom face may be configured to have a continuous slope, to have a slope which is partly made flat, or to have a stepped slope. Note that, where a drain hole is provided as described later, the bottom face may be configured to slope downwardly only to the location corresponding to the drain hole. 
     Assuming the entry of water such as rain water from the air inlet  154 , since the bottom face  156   a  slopes downwardly toward the air inlet  154 , the water present on the bottom face  156   a  flows toward the air inlet  154 . This makes it possible to suppress the retention of water in the heat dissipator  150 . Moreover, assuming the entry of water such as rain water from the air outlet  155 , since the bottom face  156   b  slopes downwardly toward the air outlet  155 , the water present on the bottom face  156   b  flows toward the air outlet  155 . This makes it possible to suppress the retention of water in the heat dissipator  150 . 
     The bottom face  156   a  may be provided with a drain hole  157  located below the radiator  151  and near the air inlet  154 . Moreover, the bottom face  156   b  may be provided with a drain hole  158  located below the fan  152  and near the air outlet  155 . The shape and number of the drain holes  157  and  158  are determined in conformance with the shapes of the air inlet  54  and the air outlet  155 . Although the drain hole  157  is located near the air inlet  154 , whereas the drain hole  158  is located near the air outlet  155  in the present non-limiting embodiment, the drain hole  157  may be located in any position of the bottom face  156   a,  and the drain hole  158  may also be located in any position of the bottom face  156   b.    
     As the advantages of formation of the drain holes  157  and  158 , considering the entry of water such as rain water from the air inlet  154 , the water present on the bottom face  156   a  can be discharged from the drain hole  157  located near the air inlet  154 , and also, considering the entry of water such as rain water from the air outlet  155 , the water present on the bottom face  156   b  can be discharged from the drain hole  158  located near the air outlet  155 . 
     Only when the drain holes  157  and  158  are provided, the bottom face may slope downwardly from the inward side of the air flow channel  153  toward each of the drain holes  157  and  158 , as well as slope downwardly from each of the air inlet  154  and the air outlet  155  to each of the drain holes  157  and  158 . In this case, the water entered can be collected in each of the drain holes  157  and  158  and flow therefrom. 
     Thus, by providing the drain holes  157  and  158 , it is possible to discharge water which has entered through the air inlet  154  or the air outlet  155  without causing the water to flow over the surface of the exterior case  80 . Moreover, since the drain holes  157  and  158  are provided inside the exterior case  80  (in other words, provided in the heat dissipator  150  or the air passageways  183  and  184 ), even under a substantial external wind pressure, the water entered can be discharged smoothly without being influenced by the wind pressure. 
     In the present non-limiting embodiment, there may be a case where the heat dissipator  150  is disposed in other location than the lowermost part of the exterior case  80 . In such a case, a water supply pipe may be connected to the drain holes  157  and  158  to direct discharged water toward the bottom of the fuel cell apparatus  11  or away from the fuel cell apparatus  11 . Moreover, there may be a case where the air inlet  154  is connected, through the air passageway  183 , to the opening  181   a  provided in the side face  81 , or the air outlet  155  is connected, through the air passageway  184 , to the opening  182   a  provided in the side face  82 . In this case, the air passageway  183  may be configured to slope downwardly toward the opening  181   a,  or the air passageway  184  may be configured to slope downwardly toward the opening  182   a.  Besides, the air passageways  183  and  184  may be provided with a drain hole. 
     Thus, since water which has entered the heat dissipator  150  flows toward the air inlet  154  or the air outlet  155 , this avoids the retention of water in the heat dissipator  150 , and thus protects the heat dissipator  150  from corrosion. Moreover, since the water which has entered can be discharged from the drain holes  157  and  158 , this protects the heat dissipator  150  from corrosion. In consequence, a highly durable fuel cell apparatus is provided. 
     The present disclosure has been described in detail, it being understood that the present disclosure is not limited to the non-limiting embodiments as described heretofore, and various changes, modifications, and improvements are possible without departing from the scope of the present disclosure. 
     REFERENCE SIGNS LIST 
     
         
         
           
               1 ,  11 : Fuel cell apparatus 
               10 : Reformer 
               20 : Cell stack 
               30 : Heat exchanger 
               40 : Heat-storage tank 
               50 ,  150 : Heat dissipator 
               51 ,  151 : Radiator 
               52 ,  152 : Fan 
               53 ,  153 : Air flow channel 
               54 ,  154 : Air inlet 
               55 ,  155 : Air outlet 
               156   a,    156   b : Bottom face 
               157 ,  158 : Drain hole 
               59 : Radiator duct 
               59 A: Upper duct 
               59 B: Lower duct 
               59 A 1 ,  59 C: First duct 
               60 : Condensed water tank 
               70 ,  71 : Auxiliary machine 
               80 ,  180 : Exterior case 
               81 ,  82 ,  83 : Side face 
               81   a,    83   a,    181   a,    182   a : Opening 
               83 ,  84 ,  183 ,  184 : Air flow channel 
               91 : Fuel cell module 
               105 : Circulation line