Patent Publication Number: US-9893328-B2

Title: Thermally insulating apparatus for accommodating at least one component of an SOFC fuel cell system, and method for producing an apparatus of this kind

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an apparatus for accommodating at least one component of a SOFC fuel cell system comprising a thermally insulating inner box and an outer box surrounding the inner box, wherein the inner box comprises a base, a cover, and side panels, wherein the outer box bears against the base, the cover, and the side panels of the inner box and presses them together, and wherein the at least one component can be arranged in the interior of the inner box. 
     The present invention further relates to a method for producing such an apparatus. 
     2. Discussion of the Related Art 
     It is known to, at least partly, position components of a SOFC fuel cell system in a so-called “hot box” which may, at least partly, accommodate particularly those components of an SOFC fuel cell system which become very hot during operation. Such an apparatus for accommodating at least one component of a SOFC fuel cell system is, for example, known from the DE 10 2006 060 809 A1. 
     What is problematic with such designs is particularly the shrinkage of a used insulation material which may lead to more or less large or deep cracks or gaps in the insulation. 
     The present invention is, accordingly, based on the object to prevent any crack/gap formation and to improve the insulating properties in this way. 
     SUMMARY OF THE INVENTION 
     According to the invention, this object is solved by the base, the cover, and the side panels being at least partly over-dimensioned so that the inner box can be assembled by press-fitting. By over-dimensioning a press-fitting is obtained by compressing the base, the cover, and the side panels which together form the thermally insulating inner box. A particularly initial shrinkage at the base, the cover, and/or the side panels resulting from the pressure and the high temperature during the operation of the SOFC fuel cell system will therefore not lead to the formation of cracks and/or gaps between the base, the cover, and/or the side panels which together form the insulating inner box. The term “over-dimensioning” thus characterises the dimensions of the base, the cover and the side panels relative to each other. At least some of the dimensions of the base, of the cover, and/or the side panels exceed the possible maximum dimensions in the assembled state of the inner box. During the assembly of the inner box, accordingly, the press-fitting is formed. The press-fitting enables a zero-clearance/gap-free fitting of the parts of the inner box by a mechanical deformation of parts of the inner box required for the assembly. Owing to the mechanical deformation the formation of heat bridges by crack formation is reliably prevented even after a particularly initial material shrinkage at the parts of the inner box. The base and/or the cover and/or the side panels may, for example, be manufactured of a microporous insulating material. The base and/or the cover and/or the side panels may, for example, have a wall thickness of 3 mm to 50 mm, preferably approximately 40 mm. The outer box bearing against the respective outer sides of the base, of the cover and of the side panels may, for example, compress the inner box from all sides to the extent that the desired press-fitting is obtained. The base and/or the cover and/or the side panels are deformed accordingly by the outer box during assembly. 
     Usefully, it may be contemplated that the outer box comprises an outer cover, an outer base, and outer side panels. In this way a simple assembly of the outer box can be realised. The outer cover and/or the outer base and/or the outer side panels may, for example, be manufactured of a plastic material having a higher solidity as compared to the insulation material used for the insulating inner box. In particular, the outer cover and/or the outer base and/or the outer side panels may be made of polyamide or metal. The outer base and/or the outer cover and/or the outer side panels may, for example, be produced by an injection moulding method. The outer base and/or the outer cover and/or the outer side panels may, for example, have a wall thickness from 10 mm to 30 mm, preferably approximately 20 mm. 
     Advantageously it may be contemplated that the outer cover and/or the outer side panels and/or the outer base are connectable to the outer box surrounding the inner box by means of fixing means. In this way the outer box may uniformly compress the inner box from all sides. The fixing means used may, for example, comprise screws and/or nuts and/or rivets. In particular, the fixing means may comprise self-tapping screws so that, on the one hand, a releasable connection can be established between the outer cover and/or the outer base and/or the outer side panels, and, at the same time, the separate production of a thread for accommodating the self-tapping screw can be omitted. Possibly even the separate production of a drilled hole for accommodating the screw may be omitted. The fixing means may further comprise an adhesive bond between the outer cover and/or the outer base and/or the outer side panels. The adhesive bond may, for example, not be formed so as to be heat resistant to enable a preliminary simple pre-installation of the outer box without any further fixing means. A final installation of the outer box may then, for example, be implemented with the aid of further readily releasable fixing means, for example screws. In this way the outer box may be reopened without problems without having to do without a facilitated pre-installation in case of a subsequent defect after the activation of the SOFC fuel cell system. 
     It may also be contemplated that the outer cover and/or the outer base and/or the outer side panels are designed as a reinforced hollow structure. In this way the apparatus may be designed so that it is altogether more lightweight since material can be saved on the outer box without its stability being reduced to a relevant extent. The reinforced hollow structure may, for example, be formed as a thin cover layer which may be part of the outer cover and/or of the outer base and/or the outer side panels on the side of the outer cover and/or of the outer base and/or the outer side panels facing the inner box and/or on the side of the outer cover and/or of the outer base and/or the outer side panels facing away from the von the inner box. This thin cover layer may, for example, serve pressure distribution on the side facing the inner box. On the side of the outer box facing away from the inner box the thin cover layer may, for example, improve the insulating effect of the apparatus since insulating air cushions are formed in the reinforced hollow structure. 
     Usefully it may further be contemplated that a clamping device comprising a cover plate and a clamping block is provided, wherein the clamping block can, at least partly, be arranged in a clamping orifice in the outer box and a corresponding further clamping orifice in the inner box, and wherein the cover plate can be fixed on the outer box so that the clamping block is, at least partly, pressed into the interior of the inner box. By providing the clamping device a fuel cell stack arranged in the interior of the inner box may be separately compressed in its preferred thermally-induced linear expansion direction perpendicular to the stacking direction of the individual fuel cells. In this way, the density of an SOFC fuel cell stack disposed in the inner box can be ensured even in case of an operation-related shrinkage of the commonly used glass seals. 
     Furthermore, it may also be contemplated that the at least one component which can be positioned in the interior of the inner box is an SOFC fuel cell stack and/or a fuel reformer and/or an afterburner heat exchanger unit. In this way, all or at least important parts of the SOFC fuel cell system, particularly those components of the SOFC fuel cell system which become particularly hot during operation, may be placed in the interior of a single insulating box together. 
     It may also be contemplated that corresponding supply orifices through which supply lines may be passed are provided in the outer box and in the inner box, wherein fuel and air can be supplied to the interior of the inner box via the supply lines, and waste gas and generated electric current can be discharged from or lead out of the interior of the inner box. By providing corresponding supply orifices in the outer box and in the inner box connection lines may be guided to the components of the SOFC fuel cell system disposed in the interior of the apparatus in a particularly convenient way. In this way, in particular, no terminals to be elaborately manufactured so as to be closable have to be provided in wall sections of the outer box and/or in wall sections of the inner box. The supply lines may be conveniently passed through the corresponding supply orifices. 
     In this connection it may be contemplated that the supply orifices in the outer box are designed as at least one insert formed of an insulating material, wherein the insulating material has an increased stability as compared to the remainder the outer box. In this way it may, in particular, be ensured that heat bridges possibly forming at the supply lines will not damage the outer box. Furthermore, a run of the supply lines through the supply orifices which is safe and precise even during the operation of the SOFC fuel cell system can be ensured so that particularly the supply orifices provided in the inner box are not damaged, for example, widened by the supply lines. 
     It may also be contemplated that the outer box comprises at least one support device for a control device and/or for an ancillary unit of the SOFC fuel cell system, wherein the control device is designed for controlling the at least one component which can be positioned in the interior of the inner box. In this way, other components of the SOFC fuel cell system may be mountable and possibly exchangeable together with the apparatus. Furthermore, a multiple use of the outer box is rendered possible in this way. 
     In addition, it may be contemplated that the at least one support device is mountable on the outer box and/or integrally formed with the outer box. If the support device is mountable on the uniformly designed outer box a variable design of the outer box may be achieved so that an individualisation of the arrangement of components mountable on the support device is rendered possible. For example, the positioning of individual components may be varied depending on the available space. Likewise, different components, for example, components differing with regard to their performance and requiring different support devices may be mountable on the uniformly designed outer box. If the support device is integrally formed with the outer box, for example, by an injection moulding method from the same material as the rest of the outer box, the outer box may be used for mounting components on the outer side of the outer box without any additional effort. 
     The method according to the invention is based on the generic method for producing the apparatus according to the invention in that the inner box is assembled by press-fitting. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
       The invention will now be explained by way of example with the aid of a preferred embodiment with reference to the accompanying drawing in which: 
         FIG. 1  shows a three-dimensional exploded view of an apparatus for accommodating at least one component of an SOFC fuel cell system. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 1  shows a three-dimensional exploded view of an apparatus  10  for accommodating at least one component of a SOFC fuel cell system. The apparatus  10  comprises an inner box  12  and an outer box  14 . The outer box  14  surrounds the inner box  12 . In the interior of the inner box  12 , components of a SOFC fuel cell system not shown in  FIG. 1  may be positioned. These components may, for example, be an SOFC fuel cell stack and/or a fuel reformer and/or an afterburner heat exchanger unit. The inner box  12  comprises a base  16 , a cover  18 , and side panels  20 ,  22 ,  24 , and  26 . The base  16 , and/or the cover  18 , and/or the side panels  20 ,  22 ,  24 , and  26  are formed of a thermally insulating material, for example, a microporous insulating material. The base  16 , and/or the cover  18 , and/or the side panels  20 ,  22 ,  24 , and  26  may optionally have a smaller material thickness at their edges than in their respective centre as shown in  FIG. 1  so that, particularly, circumferential bridges having a lower material thickness may be formed at their respective edges. In this way, the formation of continuous gaps which would lead to a continuous crack reducing the insulating effect of the inner box  12  in case of material shrinkage of the insulating material can be prevented during the assembly of the components of the inner box  12 . The base  16 , the cover  18 , and the side panels,  20 ,  22 ,  24 , and  26  are partly manufactured so as to be over-dimensioned so that a complete fitting into the inner box  12  is only possible by applying pressure acting on the outer sides of the inner box  12  and provided by the outer box  14 . While the inner box  12  is assembled a press-fitting is generated. The term “over-dimensioning” thus characterises the dimensions of the base  16 , of the cover  18  and the side panels  20 ,  22 ,  24 , and  26  relative to each other. At least some of the dimensions of the base  16 , of the cover  18  and/or the side panels  20 ,  22 ,  24 , and  26  exceed the possible maximum dimensions of the inner box  12  in the assembled state. When fitting the inner box  12  therefore the press-fitting is produced. The press-fitting renders a zero-clearance/gap-free assembly of the parts of the inner box  12  by a mechanical deformation of the base  16 , of the cover  18 , and/or of the side panels  20 ,  22 ,  24 ,  26  of the inner box  12  required for fitting possible. Owing to the mechanical deformation the formation of heat bridges due to crack formation is reliably prevented even after an especially initial material shrinkage at the parts of the inner box  12 . 
     The outer box  14  may comprise an outer cover  28 , an outer base  30  and outer side panels  32 ,  34 ,  36 , and  38 . The outer cover  28 , the outer base  30 , and the outer side panels  32 ,  34 ,  36 , and  38  may, for example, be assembled with the outer box  14  with the aid of fixing means  40 . In the assembled state the inner sides of the outer cover  28 , of the outer base  30 , and of the outer side panels  32 ,  34 ,  36 , and  38  apply uniform compression forces to the outer sides of the inner box  12  so that it is assembled by press-fitting. The fixing means  40  may, for example, comprise screws. In this way, the outer cover  28 , the outer base  30 , and the outer side panels  32 ,  34 ,  36 , and  38  may be screwed together. As shown in  FIG. 1 , holes for accommodating the fixing means  40  formed as screws may be provided in the outer cover  28  and/or the outer base  30  and/or the outer side panels  32 ,  34 ,  36 , and  38 . If the fixing means  40  is designed as a self-tapping screws the holes or at least threads located in the holes and interacting with the fixing means  40  may be omitted. The self-tapping screws may generate the holes and/or the threads themselves during the installation, i.e. when they are screwed in. For facilitating the installation of the outer box  14 , an adhesive bond not explicitly shown in  FIG. 1  may be provided between the outer cover  28  and the outer side panels,  32 ,  34 ,  36 , and  38  as well as between the outer base  30  and the outer side panels  32 ,  34 ,  36 , and  38 . This adhesive bond may be regarded as part of the fixing means  40 . If the adhesive bond is provided other fixing means, for example in the form of the screws shown in  FIG. 1 , may be omitted as required. If the fixing device  40  comprises both the screws shown in  FIG. 1  and an adhesive bond between the individual parts of the outer box  14  it may be contemplated that the adhesive bond used is not heat resistant or soluble in water for facilitating the removal of the outer box  14 . The installation of the outer box  14  may then be subdivided into a pre-installation and a final installation. The pre-installation may comprise the assembly of the outer box  14  with the aid of the adhesive bond. The final installation may comprise the final screwing-in of additional fixing means  40  formed as screws. In this way a securing of the outer box  14  can already be omitted during the final installation. If the adhesive bond used is not heat resistant or not water-insoluble a simple removal of the outer box  14  can also be rendered possible. The outer cover  28  and/or the outer base  30  and/or the outer side panels  32 ,  34 ,  36 , and  38  may have a hollow structure  42  as shown in  FIG. 1 . The hollow structure  42  may, for example, be a simple honeycomb structure. The hollow structure  42  renders the saving of material possible which leads to a weight reduction without the stability of the outer box  14  being affected. The hollow structure  42  may be covered with thin plates allocated to the outer cover  28 , the outer base  30 , and the outer side panels  32 ,  34 ,  36 , and  38 . In this way, on the one hand, a uniform distribution of the compression forces acting on the inner box  12 , and, on the other hand, an improvement of the insulating effect of the apparatus  10  attributable to the air cushions enclosed in the hollow structure  42  may be achieved. 
     The apparatus  10  may further comprise a clamping device  44 . As shown in  FIG. 1 , the clamping device  44  may comprise a cover plate  46 , a clamping block  48 , a pressure distribution plate  68 , and elastic elements  66 . The clamping block  48  may be pressed into the interior of the inner box  12  through a clamping orifice  50  and a corresponding additional clamping orifice  52  and thereby clamp a fuel cell stack not shown in  FIG. 1  in the mounted state of the clamping device  44 . The clamping force required for this purpose may be achieved by fixing the cover plate  46  on the outer cover  28  with the aid of fixing elements  70 , wherein the applied force can be uniformly transferred to the clamping block  48  via the elastic elements  66  and the pressure distribution plate  68 . It is possible that a fuel cell stack positioned in the interior of the apparatus  10  is removable by removing the clamping device  44 . It is further possible that the fuel cell stack is only inserted after the fitting of the inner box  12  and the outer box  14  into the apparatus  10  before it is finally closed by the clamping device  44 . The clamping force applied by the clamping device  44  may be adjusted via the elastic elements  66  and, for example, amount to 500 N to 600 N, preferably approximately 550 N. The elastic elements  66  may, for example, be formed as coil springs. 
     The outer box  14  may comprise supply orifices  54 ,  56 ,  58 , and  74 . The supply orifices  54 ,  56 ,  58 , and  74  may extend through the outer box  14  and the inner box  12 . However, it is also feasible that the supply orifices  54 ,  56 ,  58 , and  74  only extend through the outer box  14 . For example, the supply orifices  54 ,  56 , and  58  may be located in the front outer side panel  32 . The supply orifice  74  may, for example, be located in the outer base  30 . The supply orifices  54 ,  56 ,  58 , and  74  may serve the supply of fuel and air as well as the lead-away of generated electric energy and the discharge of waste gas. In particular, if the supply orifices  54 ,  56 , and  58  extend through the outer box  14  and the inner box  12 , an insert  60  formed of a heat insulating material having a high stiffness may be provided in the outer box  14 . In this way, heat bridges at supply lines passed through the supply orifices  54 ,  56 , and  58  which might cause damage to the outer box  14  by heat may be avoided. Furthermore, damage to the supply orifices  54 ,  56 , and  58  in the inner box  12 , for example by widening, may be prevented in this way since the supply lines are accurately passed through the orifices. In this way, a gap formation between the supply lines and the inner box  12  which may reduce the insulating effect of the inner box  12  is prevented. 
     On the outer box  14 , for example on the front outer side panel  32 , support devices  62 ,  64  may be provided. For example,  FIG. 1  shows the support device  62  integrally formed with the front outer side panel  32 . The support device  62  may, for example, be formed as a hole for accommodating a mounting device not shown in  FIG. 1  on a bulge of the hollow structure  42 . Further, support devices  64  which may be mountable on the front outer side panel  32  and in turn render the installation of further components of the SOFC fuel cell system possible are shown in  FIG. 1 . The support device  62  may also permit the installation von additional components of the SOFC fuel cell system on the apparatus  10 . 
     On the outer base  30 , further, base elements  72  may be provided which may permit a fixation of the apparatus  10  in, for example, a housing of the SOFC fuel cell system not shown in  FIG. 1 . 
     A thin cover of the hollow structure  42  can, for example, be seen on the outer base  30 . Alternatively it is possible to design the outer cover  28  and/or the outer base  30  and/or the outer side panels  32 ,  34 ,  36 , and  38  so as to be massive, i.e. particularly without a hollow structure  42 . 
     For the assembly of the apparatus  10  first the base  16  is stacked onto the outer base  30 . Then the components of the SOFC fuel cell system to be positioned in the interior of the box  12  may be pre-mounted on the inner base  16 . Thereafter, the side panels,  20 ,  22 ,  24 , and  26  may be loosely brought up to the base  16 . By applying the cover  18 , the side panels,  20 ,  22 ,  24 , and  26  can first be temporarily held in this position. Now the installation of the outer side panels  32 ,  34 ,  36 , and  38  is performed, wherein, preferably, first two opposing outer side panels are fixed on the outer base  30 , particularly the front outer side panel  32  and the rear outer side panel  38 . Finally the outer cover  28  can be joined with the remaining parts of the outer box  14  so that both the outer box  14  and the inner box  12  are mounted. The insertion of the clamping device  44  may be performed after the installation of the outer cover  28 . 
     The features of the invention described in the above description, the drawing, as well as in the claims may be important for the realisation of the invention both individually and in any combination. 
     LIST OF NUMERALS 
     
         
           10  apparatus 
           12  inner box 
           14  outer box 
           16  base 
           18  cover 
           20  side panel 
           22  side panel 
           24  side panel 
           26  side panel 
           28  outer cover 
           30  outer base 
           32  outer side panel 
           34  outer side panel 
           36  outer side panel 
           38  outer side panel 
           40  fixing device 
           42  hollow structure 
           44  clamping device 
           46  cover plate 
           48  clamping block 
           50  clamping orifice 
           52  additional clamping orifice 
           54  supply orifice 
           56  supply orifice 
           58  supply orifice 
           60  insert 
           62  support device 
           64  support device 
           66  elastic element 
           68  pressure distribution plate 
           70  fixing element 
           72  base element 
           74  supply orifice