Abstract:
A dehumidifier includes a suction unit, a dehumidifying unit having a chiller, a discharge unit having a heat radiator, a refrigerant circulating system, and a heat exchanger. The suction unit sucks humid air into the dehumidifying unit, which cools the humid air and condenses the moisture in the humid air to create dry air. The discharge unit heats and discharges the dry air coming from the dehumidifying unit, and the heat exchanger exchanges heat between the humid air and the dry air coming from the dehumidifying unit. The refrigerant circulating system is used to cool the humid air at the dehumidifying unit and to heat the dry air at the discharge unit. In some embodiments, the heat exchanger includes a heat transfer unit, wherein flat plates are turned back alternately in opposite directions, and a first and second flow passage are prepared alternately in many layers between the flat plates.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to a dehumidifier to be installed in a room such as a drying chamber and is used to dehumidify the air in the room. 
     A type of dehumidifier has been known in the past, according to which a chiller is cooled down by vaporization heat, i.e. by vaporizing a refrigerant in liquid state. Then, humid air sucked from outside is chilled down by a chiller, and the humid air is dehumidified by condensation of the moisture contained in the humid air by chilling. The refrigerant is then liquefied by compressor, and dry air thus dehumidified is heated by condensation heat generated at the time of liquefaction. Then, the dry air is discharged to outside. 
     However, in case of a conventional type dehumidifier, temperature difference between the temperature of the humid air sucked from outside and the temperature of the dry air, which has been chilled down and dehumidified, is risen. Thus, problems may arise that electric power consumption required for chilling and temperature rise after dehumidification would be higher. 
     The Japanese Patent Publication JP-A-2000-320861 discloses a dehumidifier, according to which, after allowing the external air as sucked through air suction inlet to pass and to be heated by passing through one-half portion of an approximately U-shaped condenser, the heated air is passed to an evaporator cooled down. Then, a vapor in the air is efficiently condensed on the surface of the evaporator and dehumidified by rising temperature gradient of the air, and the dry air thus dehumidified is heated by passing through another one-half portion of the condenser, and the dried air after heating is discharged to outside via an air discharge outlet. 
     Also, the Japanese Patent Publication JP-A-Sho36-21644 discloses a heat exchanger having a heat transfer unit, wherein projections are prepared at a distribution ratio as required on a flat plate, the flat plate is folded back in multilayers alternately with such width as required, a gap for the projection is formed between the flat plates, and the flat plates are heat boundary. In the heat transfer unit, high temperature fluid and low temperature fluid are passed through the gap, and heat exchange operation is performed via the heat transfer unit. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide a dehumidifier, by which it is possible to have higher thermal efficiency in the process of dehumidifying and to save electric power required. 
     To attain the above object, a dehumidifier according to the present invention comprises a suction unit which humid air is sucked in, a dehumidifying unit having a chiller and for cooling down the humid air sucked in and for dehumidifying by condensing the moisture in the humid air, a discharge unit having a heat radiator and for heating and discharging dry air as dehumidified at the dehumidifying unit, a refrigerant circulating system for cooling down the humid air at the dehumidifying unit and for heating the dry air at the discharge unit, and a heat exchanger for performing heat exchange between the humid air and the dry air as dehumidified at the dehumidifying unit. 
     Further, in the dehumidifier according to the present invention, a partition is disposed in the dehumidifying unit, and there are provided a humid air flow passage which the humid air passes through and a dry air flow passage which the dry air passes through. 
     Further, in the dehumidifier according to the present invention, the heat exchanger comprises a casing arranged in a hollow box and a heat transfer unit accommodated in the casing, and flat plates are turned back alternately in opposite directions, and a first flow passage and a second flow passage are prepared alternately in many layers between the flat plates, and among a front plate and a rear plate running in parallel to a return line of the flat plate of the casing, a high temperature fluid inlet and a high temperature fluid outlet being communicated with the second flow passage are disposed on the front plate side, and a low temperature fluid inlet and a low temperature fluid outlet being communicated with the first flow passage are disposed on the rear plate side, a lateral plate sealing member to cover entire region of the end unit and a pressing plate having rigidity are installed between lateral plate being at a position opposite to an end of the heat transfer unit and the heat transfer unit, a biasing means is disposed between the pressing plate and the lateral plate, the biasing means presses the lateral plate sealing member toward an end of the heat transfer unit via the pressing plate, and the lateral plate sealing member air-tightly blocks the first flow passage and the second flow passage. 
     Further, in the dehumidifier according to the present invention, the biasing means is a coil spring arranged at a distribution rate as required, a flange nut is inserted from a side of the pressing plate of the coil spring, a spring supporting bolt to be inserted in the lateral plate is threaded on the flange nut, and by fastening the spring supporting bolt and by compressing the coil spring, pressing force onto the pressing plate of the spring is constrained, and by loosening the spring supporting bolt, constraining of the coil spring is released so that pressing force is applied onto the pressing plate. 
     Further, in the dehumidifier according to the present invention, a flat plate on the uppermost portion and a flat plate on the lowermost portion of the heat transfer unit are folded back in the same direction, a sealing member is engaged with each of a forward end of the flat plate of the uppermost portion and a forward end of the flat plate of the lowermost portion, and the sealing members are squeezed by an edge holding hardware disposed on a top plate of the casing and the top plate, and by the edge holding hardware disposed on a bottom plate of the casing and the bottom plate, and the heat transfer unit is fixed. 
     Further, in the dehumidifier according to the present invention, projecting portions are projected on each of a front side and a rear side of the flat plate folded back, the projecting portion on front surface of the flat plate and the projecting portion on rear surface are brought face to face to each other, and a gap serving as a flow passage is formed between the flat plates placed opposite to each other. 
     Further, in the dehumidifier according to the present invention, side end portions of the flat plate are air-tightly connected so that the first flow passage or the second flow passage is blocked, and the second flow passage and the first flow passage are separated from each other. 
     According to the present invention, the dehumidifier comprises a suction unit which humid air is sucked in, a dehumidifying unit having a chiller and for cooling down the humid air sucked in and for dehumidifying by condensing the moisture in the humid air, a discharge unit having a heat radiator and for heating and discharging dry air as dehumidified at the dehumidifying unit, a refrigerant circulating system for cooling down the humid air at the dehumidifying unit and for heating the dry air at the discharge unit, and a heat exchanger for performing heat exchange between the humid air and the dry air as dehumidified at the dehumidifying unit. As a result, less heat amount is needed for cooling down the humid air and thermal efficiency in the dehumidifying process can be extensively increased, and electric power can be saved. 
     Further, according to the present invention, in the dehumidifier, a partition is disposed in the dehumidifying unit, and there are provided a humid air flow passage which the humid air passes through and a dry air flow passage which the dry air passes through. As a result, it is possible to efficiently perform dehumidifying process because the humid air before the dehumidifying process and the dry air after the dehumidifying processes are not mixed together. 
     Further, according to the present invention, in the dehumidifier, the heat exchanger comprises a casing arranged in a hollow box and a heat transfer unit accommodated in the casing, flat plates are turned back alternately in opposite directions, and a first flow passage and a second flow passage are prepared alternately in many layers between the flat plates, and among a front plate and a rear plate running in parallel to a return line of the flat plate of the casing, a high temperature fluid inlet and a high temperature fluid outlet being communicated with the second flow passage are disposed on the front plate side, and a low temperature fluid inlet and a low temperature fluid outlet being communicated with the first flow passage are disposed on the rear plate side, a lateral plate sealing member to cover entire region of the end unit and a pressing plate having rigidity are installed between lateral plate being at a position opposite to an end of the heat transfer unit and the heat transfer unit, a biasing means is disposed between the pressing plate and the lateral plate, the biasing means presses the lateral plate sealing member toward an end of the heat transfer unit via the pressing plate, and the lateral plate sealing member air-tightly blocks the first flow passage and the second flow passage. As a result, it is possible to carry out disassembling procedure in easier manner, and maintenance services such as cleaning can be conveniently performed. 
     Further, according to the present invention, in the dehumidifier, the biasing means is a coil spring arranged at a distribution rate as required, a flange nut is inserted from a side of the pressing plate of the coil spring, a spring supporting bolt to be inserted in the lateral plate is threaded on the flange nut, and by fastening the spring supporting bolt and by compressing the coil spring, pressing force onto the pressing plate of the spring is constrained, and by loosening the spring supporting bolt, constraining of the coil spring is released so that pressing force is applied onto the pressing plate. As a result, no reaction force of the coil spring is applied on the lateral plate when mounting or removing the lateral plate, and mounting and removing of the lateral plate can be easily carried out. 
     Further, according to the present invention, in the dehumidifier, a flat plate on the uppermost portion and a flat plate on the lowermost portion of the heat transfer unit are folded back in the same direction, a sealing member is engaged with each of a forward end of the flat plate of the uppermost portion and a forward end of the flat plate of the lowermost portion, and the sealing members are squeezed by an edge holding hardware disposed on a top plate of the casing and the top plate, and by the edge holding hardware disposed on a bottom plate of the casing and the bottom plate, and the heat transfer unit is fixed. As a result, there is no need to physically fix the heat transfer unit by the procedure such as welding, and the reduction of the cost can be achieved. 
     Further, according to the present invention, in the dehumidifier, projecting portions are projected on each of a front side and a rear side of the flat plate folded back, the projecting portion on front surface of the flat plate and the projecting portion on rear surface are brought face to face to each other, and a gap serving as a flow passage is formed between the flat plates placed opposite to each other. As a result, the height of the projecting portion required for forming the flow passage may be only one-half. To fabricate the flat plate is facilitated, and the manufacturing cost can be reduced. 
     Furthermore, according to the present invention, in the dehumidifier, side end portions of the flat plate are air-tightly connected so that the first flow passage or the second flow passage is blocked, and the second flow passage and the first flow passage are separated from each other. As a result, the low temperature fluid flowing through the first flow passage and the high temperature fluid flowing through the second flow passage are not mixed together, and universal adaptability can be achieved. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematical drawing to show an arrangement of a dehumidifier according to an embodiment of the present invention, 
         FIG. 2  is a schematical perspective view of a heat exchanger according to the embodiment of the present invention, 
         FIG. 3  is an arrow diagram along the line A-A in  FIG. 2 , 
         FIG. 4  is an exploded perspective view of the heat exchanger as given above, 
         FIG. 5A  and  FIG. 5B  each represents a partial cross-sectional view of an end portion of the heat exchanger.  FIG. 5A  is a drawing to show a condition where a right lateral plate is mounted and a coil spring is not released, and  FIG. 5B  is a drawing to show a condition where the right lateral plate is mounted and the coil spring is released, 
         FIG. 6A  and  FIG. 6B  each represents a relation among the coil spring and a right lateral plate and a flange nut.  FIG. 6A  shows a condition in disassembled state, and  FIG. 6B  shows a condition where the coil spring is completely compressed, 
         FIG. 7  is a partial cross-sectional view of a lateral end portion of a variation example of the heat exchanger, and 
         FIG. 8  is a schematical drawing to show approximate arrangement when the dehumidifier according to the present embodiment is applied in a drying chamber. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Description will be given below on an embodiment of the present invention by referring to the attached drawings. 
     First, referring to  FIG. 1 , description will be given on an arrangement of a dehumidifier according to an embodiment of the present invention. 
     A dehumidifier  41  primarily comprises an air suction and discharging unit  42 , a heat exchanger  1 , a dehumidifying unit  43 , and a refrigerant circulating system  44 . The air suction and discharging unit  42  is disposed at an end of the heat exchanger  1 , and the dehumidifying unit  43  is provided at the other end of the heat exchanger  1 . 
     The air suction and discharge unit  42  comprises a suction unit  45  and a discharge unit  46 . The suction unit  45  has a suction inlet  48  to suck humid air  47  and a high temperature fluid inlet  21  to take the humid air  47  into the heat exchanger  1 . The discharge unit  46  has a low temperature fluid outlet  24  where dry air  49  flows in and a discharge outlet  51  to discharge the dry air  49 . 
     In the suction unit  45 , a suction fan  52  is provided, which sucks the humid air  47  from outside via the suction inlet  48  and discharges the humid air  47  via the high temperature fluid inlet  21 . An exhaust fan  53  and a heat radiator  54  are accommodated in the discharge unit  46 . The exhaust fan  53  takes the dry air  49  via the low temperature fluid outlet  24  and discharges the dry air  49  through the discharge outlet  51  via the heat radiator  54 . 
     The suction fan  52  and the exhaust fan  53  are designed to be integrally rotated by a first fan motor  55 . It may be so arranged that the suction fan  52  and the exhaust fan  53  are separately rotated by two motors respectively. 
     In the dehumidifying unit  43 , a chiller  56  is provided to separate space in the dehumidifying unit  43  to upper and lower portions, and a drain pipe  57  is disposed at a lower end of the dehumidifying unit  43  so that the water condensed in the dehumidifying unit  43  will be discharged. Further, in the dehumidifying unit  43 , a partition  61  to divide a space above the chiller  56  to a humid air flow passage  58  and a dry air flow passage  59 . On an upper flowing end of the humid air flow passage  58 , a high temperature fluid outlet  22  is disposed, and a low temperature fluid inlet  23  is disposed at a lower end of the dry air flow passage  59 . 
     As shown in  FIG. 3 , a first flow passage  7  (to be described later) where a low temperature fluid  38  passes through and a second flow passage  8  (to be described later) where a high temperature fluid  37  passes through are formed inside the heat exchanger  1 . An upper flowing end of the second flow passage  8  is communicated with the high temperature fluid inlet  21 , and a lower flowing end of the second flow route  8  is communicated with the high temperature fluid outlet  22 . An upper flowing end of the first flow passage  7  is communicated with the low temperature fluid inlet  23 , and a lower flowing end of the first flow passage  7  is communicated with the low temperature fluid outlet  24 . 
     A stirring fan  63  to be driven by a second fan motor  62  is provided along the dry air flow passage  59 , and the stirring fan  63  sucks the dry air  49  in the dry air flow passage  59  so as to promote the flowing of the dry air  49 . 
     The refrigerant circulating system  44  comprises a refrigerant pipe  64  in which the refrigerant flows and a compressor  65  to compress and liquefy a refrigerant in the refrigerant pipe  64 , and the refrigerant pipe  64  is connected to the heat radiator  54  and the chiller  56 . The refrigerant is circulated by the compressor  65  between the heat radiator  54  and the chiller  56  via the refrigerant pipe  64 . The refrigerant is then liquefied by the compressor  65  and radiates heat via the heat radiator  54 . Then, the refrigerant is vaporized by the chiller  56  and cools down the chiller  56 . 
     Next, description will be given on dehumidification by the dehumidifier  41 . 
     The first fan motor  55 , the second fan motor  62 , and the compressor  65  are driven. By the driving of the first fan motor  55 , the suction fan  52  and the exhaust fan  53  are rotated, and by the driving of the second fan motor  62 , the stirring fan  63  is rotated. By the compressor  65 , the refrigerant circulating system  44  is driven. 
     By rotation of the suction fan  52 , the exhaust fan  53 , and the stirring fan  63 , the humid air  47  is sucked in through the suction inlet  48 . The humid air  47  is passed through the heat exchanger  1  as the high temperature fluid  37  and is flown into the humid air flow passage  58  via the high temperature fluid outlet  22 . The high temperature fluid  37  is cooled down by the chiller  56  as the high temperature fluid  37  passes through the chiller  56  to lower than dew-point temperature, and is dehumidified. The air thus dehumidified is flown into the heat exchanger  1  as the low temperature fluid  38  via the low temperature fluid inlet  23 . Heat exchange is performed between the high temperature fluid  37  and the low temperature fluid  38  in the heat exchanger  1 . Then, the high temperature fluid  37  is cooled down by the low temperature fluid  38 , and a temperature of the low temperature fluid  38  is risen by the high temperature fluid  37 . 
     The low temperature fluid  38  is discharged via the low temperature fluid outlet  24 . The low temperature fluid  38  is then heated in a process to pass through the heat radiator  54  and the low temperature fluid  38  is discharged as the dry air  49  via the discharge outlet  51 . 
     By driving the compressor  65 , the refrigerant is circulated in the refrigerant circulating system  44 . 
     The refrigerant in gaseous state as passing through the refrigerant pipe  64  is compressed by the compressor  65  and is liquefied. In this process, condensation heat is generated, and temperature is risen by the fact that the refrigerant is compressed and liquefied. The refrigerant with risen temperature radiates heat as the refrigerant passes through the heat radiator  54  and heats up the low temperature fluid  38 . 
     The refrigerant of the fluid, which has been cooled down by passing through the heat radiator  54 , is guided to the chiller  56  via the refrigerant pipe  64 . The refrigerant is then expanded at the chiller  56  and is vaporized. By the vaporization of the refrigerant, heat in the surrounding is taken away, and the chiller  56  is cooled down. The chiller  56  cools down the humid air  47  to a level lower than the dew-point temperature. 
     The refrigerant thus vaporized is guided toward the compressor  65  via the refrigerant pipe  64 , and the refrigerant is then compressed by the compressor  65  again and is liquefied. 
     The circulation of the refrigerant as described above is repeated until the dehumidifying by the dehumidifier  41  is stopped. 
     As an example of the dehumidification processing as described above, the humid air  47  at normal temperature, e.g. the humid air  47  at temperature of 20° C. and at humidity of 60%, flows into the suction unit  45  from outside. 
     The humid air  47  flown into the suction unit  45  passes through the second flow route  8  (see  FIG. 3 ). Then, heat exchange is performed with the dry air  49 , which is flowing along the first flow route  7  (see  FIG. 3 ) by the heat exchanger  1 . For instance, the humid air  47  is cooled down to 10° C. and flows via the humid air flow passage  58 . Then, the humid air  47  passes through the chiller  56 , flow through a space under the chiller  56 , passes through the chiller  56  again and flows into the dry air flow passage  59  as the dry air  49 . 
     In this case, the chiller  56  is cooled down by heat exchange with the refrigerant, which passes through the refrigerant pipe  64 . During the process to pass through the chiller  56 , the humid air  47  is cooled down to temperature lower than the dew-point temperature, and moisture condensed by the refrigeration is attached on each of the fins of the chiller  56 . Therefore, the humid air  47  is dehumidified by the chiller  56 . For instance, the humid air  47  flows into the dry air flow passage  59  as the dry air  49  at temperature of 5° C. and the humidity of 30%. Also, the flowing of the humid air  47  and the dry air  49  from the humid air flow passage  58  to the dry air flow passage  59  is promoted by the stirring fan  63 . 
     The moisture attached to the fins of the chiller  56  is dropped to the bottom of the dehumidifying unit  43  and is discharged to outside via the drain pipe  57 . 
     The dry air  49  as flown into the dry air flow passage  59  further flows into the heat exchanger  1  via the low temperature fluid inlet  23 . After flowing into the heat exchanger  1 , the dry air  49  passes through the first flow passage  7 , and heat exchange is performed to and from the humid air  47 , which passes through the second flow passage  8 . For instance, the dry air  49  is heated up to 15° C., and the dry air  49  flows into the discharge unit  46  via the low temperature fluid outlet  24 . 
     The heat radiator  54  is heated by the refrigerant, which passes through the refrigerant pipe  64 , and the dry air  49  flowing into the discharge unit  46  is heated to 25° C., for instance, by heat exchange to and from the heat radiator  54 . By being heated, the dry air  49  is discharged to outside via the discharge outlet  51  as the dry air  49 , which is dried more. 
     In the present embodiment, the dehumidifier  41  has the heat exchanger  1 . By the heat exchanger  1 , heat exchange operation is performed, i.e. the heat exchange is performed between the humid air  47  at normal temperature (20° C.) and the dry air  49 , which has been cooled down to lower than the dew-point temperature by the chiller  56 . Therefore, heat amount to be needed to cool down the humid air  47  to dew-point may not be much, and it is possible to extensively increase thermal efficiency in the dehumidifying process, and to save of electric power. 
     Because the dehumidifier  41  is equipped with the heat radiator  54 , which is connected to the refrigerant pipe  64  in the discharge unit  46 , and condensation heat generated during the liquefying of the refrigerant can be collected by the dry air  49 , and the refrigerant can be cooled down. It is possible to efficiently perform dehumidification without decreasing the temperature of the air sucked in. 
     Because the partition  61  is provided in the humidifying unit  43 , the humid air  47  before the dehumidifying, which passes through the humid air flow passage  58 , is not mixed with the dry air  49  after dehumidification passing through the dry air flow passage  59 , and it is possible to promote efficient dehumidifying. 
     In the dehumidifier  41  as described above, the stirring fan  63  is provided for promoting the flowing of the dry air  49  in the dehumidifying unit  43 . However, the second fan motor  62  and the stirring fan  63  may not be used in a case where a flow passage resistance is not much when the dry air  49  passes through the chiller  56 . 
     First, referring to  FIG. 2  to  FIG. 4 , description will be given on a heat exchanger  1 , which is an embodiment of the present invention. 
     A heat exchanger  1  comprises a casing  2  configurated by a hollow box and a heat transfer unit  3  accommodated within the casing  2 . 
     The heat transfer unit  3  consists of a flat plate  4  made of a material with high thermal conductivity such as aluminum by folding the flat plate  4  alternately on each other in zigzag manner so as to be a multilayer plate. Folding lines of the flat plate  4  are consistent with each other in up-and-down direction so that the folding lines are included within same plane. 
     In the flat plate  4 , projecting portions  5   a  and  5   b  are formed by presswork in a distribution as predetermined. The projecting portion  5   a  and the projecting portion  5   b  are formed alternately in two planar directions respectively. With the flat plate  4  in folded condition, the projecting portion  5   a  is projected toward upper surface side of the flat plate  4 , and the projecting portion  5   b  is projected toward lower surface side so that the projecting portion  5   a  and the projecting portion  5   b  are brought face to face with each other. On the heat transfer unit  3 , it is preferable that an end edge  4   a  on the uppermost layer of the flat plate  4  is on the same side as an end edge  4   b  of the lowermost layer (on left side in  FIG. 3 ). On the end edges  4   a  and  4   b , sealing members  6   a  and  6   b , each designed to have a U-shaped cross-section, are fixed over total length. Each of the sealing members  6  is made of a highly elastic material having heat-resistant property, and a material such as silicone rubber is used, for instance. 
     Each of the end edges  4   a  and  4   b  is tilted toward upper side and toward lower side by an extent approximately equal to projecting height of the projecting portions  5   a  and  5   b.    
     Between sites confronted each other of the flat plate  4 , a gap is formed by the projecting portions  5   a  and  5   b . This gap forms a first flow passage  7  and a second flow passage  8  as partitioned by the flat plate  4 . As to be described later, a low temperature fluid  38  passes through the first flow passage  7  and a high temperature fluid  37  passes through the second flow passage  8 . 
     The projecting portion  5  may be so designed that the projecting portion  5  is projected only in one direction. In this case, the projecting portion  5  must have a height twice as high as heights of the projecting portions  5   a  and  5   b . If it is so arranged that the end edges  4   a  and  4   b  are projected to some extent beyond the folding lines of the flat plate  4  and the end edges  4   a  and  4   b  are butted against a front plate  13  (as to be described later) respectively, an edge holding hardware  18  may be omitted. 
     Next, description will be given on the casing  2 . 
     The casing  2  is primarily assembled by fixing a top plate  11 , a bottom plate  12 , the front plate  13 , a rear plate  14 , a right lateral plate (a lateral plate on right side with respect to the front plate  13  in  FIG. 2 )  15  and a left lateral plate  16  by using bolts  17 . The top plate  11  and the bottom plate  12  run in parallel to a plane of the flat plate  4  of the heat transfer unit  3 . The front plate  13  and the rear plate  14  run in parallel to a plane including the folding lines of the flat plate  4 , and the right lateral plate  15  and the left lateral plate  16  are confronted with an end portion of the flat plate  4  (i.e. the heat transfer unit  3 ). 
     First, description will be given on assembling of the top plate  11  and the bottom plate  12  with the front plate  13  and the rear plate  14  respectively. 
     The front plate  13  and the rear plate  14  have edge portions  13   a  and  14   a  of four sides of the front plate  13  and the rear plate  14  respectively and the edge portion  13   a  and the edge portion  14   a  are folded at right angle in outer direction. Both the front plate  13  and the rear plate  14  are designed to be shorter than the top plate  11  and the bottom plate  12 . 
     With the edge portion  14   a  fixed on the top plate  11  and on the bottom plate  12  by the bolt  17  respectively, the top plate  11  and the bottom plate  12  are assembled with the rear plate  14 . The edge holding hardwares  18  are positioned between the edge portion  13   a  and the top plate  11  and between the edge portion  13   a  and the bottom plate  12  respectively. With the edge portion  13   a  fixed on the top plate  11  and the bottom plate  12  respectively by the bolt  17 , the top plate  11  and the bottom plate  12  are assembled with the front plate  13 . The edge holding hardwares  18  are fastened together between the edge portion  13   a  and the top plate  11  and between the edge portion  13   a  and the bottom plate  12  respectively. For the purpose of improving air-tightness, sealing members may be interposed between the edge portions  13   a ,  14   a  and the top plate  11 , the bottom plate  12  respectively. 
     The edge holding hardwares  18  and  18  are tilted so as to separate from the top plate  11  and the bottom plate  12  respectively, and so as to form a V-shaped groove between the top plate  11  and the bottom plate  12  respectively. 
     As described above, the end edges  4   a  and  4   b  are tilted in upper direction and in lower direction by an extent approximately equal to projection height of the projecting portions  5   a  and  5   b  respectively. It is so arranged that the sealing member  6   a  is closely attached to the top plate  11  when the top plate  11  is brought into contact with the projecting portion  5   a  of the uppermost layer, and that the sealing member  6   b  is closely attached to the bottom plate  12  when the bottom plate  12  is closely fitted to the projecting portion  5   b  of the lowermost layer. 
     Under the condition that the end edges  4   a  and  4   b  are inserted into the V-shaped groove, the end edges  4   a  and  4   b  are sandwiched between the edge holding hardwares  18  and the top plate  11  and between the edge holding hardwares  18  and the bottom plate  12  respectively via the sealing members  6   a  and  6   b . Under the condition that the end edges  4   a  and  4   b  are sandwiched, the sealing members  6   a  and  6   b  are compressed by the pressure as required. 
     At four corners of the top plate  11  and the bottom plate  12 , support pillars  19 , each designed to have a rectangular cross-section, are fixed by screws. The high temperature fluid inlet  21  and the high temperature fluid outlet  22  are formed between the two support pillars  19  on front side and the front plate  13 . Also, the low temperature fluid inlet  23  and the low temperature fluid outlet  24  are formed between two support pillars  19  on rear side and the rear plate  14 . 
     Next, description will be given below on assembling of the top plate  11  and the bottom plate  12  with the right lateral plate  15  and the left lateral plate  16  respectively. 
     The assembling of the right lateral plate  15  and the left lateral plate  16  is performed symmetrically and in the same structure with each other. Therefore, description will be given below on the assembling of the right lateral plate  15 . 
     By arranging in such a manner that the heat transfer unit  3  is accommodated in a space formed by the top plate  11 , the bottom plate  12 , the front plate  13  and the rear plate  14 , and that the end edges  4   a  and  4   b  of the heat transfer unit  3  are sandwiched by the edge holding hardwares  18 , and the heat transfer unit  3  can be fixed on the top plate  11  and the bottom plate  12 . Under this condition, openings  25  and  25  each in rectangular shape can be formed on the left and right by the top plate  11 , the bottom plate  12 , the front plate  13  and the rear plate  14  respectively. 
     The openings  25  can be closed by the right lateral plate  15  via a planar type lateral plate sealing member  26  and via a holding plate  27 . The lateral plate sealing member  26  is used to cover the entire area of the end portion of the heat transfer unit  3 , and end portions of the first flow passage  7  and the second flow passage  8  are air-tightly closed by the lateral plate sealing member  26 . The lateral plate sealing member  26  is made of a highly elastic material with heat-resistant property, and silicone rubber is adopted, for instance. As the holding plate  27 , a material with rigidity—a steel plate, for instance—is used. 
     The holding plate  27  is provided in such a manner that the holding plate  27  can be brought closer to or separated from (i.e. displaceable in left and right directions respectively) the heat transfer unit  3 . A spring  28 , i.e. a compression coil spring, is interposed between the holding plate  27  and the right lateral plate  15 , and the lateral plate sealing member  26  is pressed on an end surface of the heat transfer unit  3  via the holding plate  27  by using the spring  28 . 
     Description will be given below further by referring to  FIG. 5  and  FIG. 6 . 
     The right lateral plate  15  has edge portions  15   a , i.e. upper and lower two edge portions, which are bent at right angle in inner direction. By fixing the edge portions  15   a  on the top plate  11  and the bottom plate  12  respectively by means of bolts  29 , the right lateral plate  15  are mounted on the top plate  11  and the bottom plate  12 . For the purpose of increasing air-tightness, the sealing material may be interposed between the edge portion  15   a  and the top plate  11  and between the edge portion  15   a  and the bottom plate  12  respectively. 
     The right lateral plate  15  has biasing means to press the holding plate  27  on the lateral plate sealing member  26 . 
     On inner surface of the right lateral plate  15 , a spring holder  32 , which is formed by bending a band-like plate member in U-shaped form, is fixed by means as required such as spot welding. An open end of the spring holder  32  is designed to face in inner direction and, a recessed groove  33  is formed. As many springs  28  as appropriate (in  FIG. 4 , two springs are shown at upper and lower positions respectively) are accommodated in the recessed groove  33 . The spring holder  32  functions as a guiding member to hold the springs  28 , which are biasing means, and the spring holder  32  also functions as a reinforcing member for the right lateral plate  15 . The biasing means is not limited to the compression coil spring, and a plate spring or the like may be used. 
     A flange nut  34  is inserted from inside of the spring  28 . The flange nut  34  has a nut portion  34   a  and a flange portion  34   b . On outer lateral surface of the flange nut  34 , a tapered portion  34   c  is formed, and it is so designed that the tapered portion  34   c  is engaged with inner diameter of the spring  28 , and that a center of the tapered portion  34   c  matches well with a center of the spring  28 . 
     From outside of the right lateral plate  15 , a spring supporting bolt  35  is inserted so that the spring supporting bolt  35  is engaged with the nut portion  34   a.    
     The spring  28  is accommodated in the recessed groove  33 , and the flange nut  34  is inserted into the spring  28 . Further, the spring supporting bolt  35  is engaged with the flange nut  34 , and the spring supporting bolt  35  is tightened. As a result, the flange nut  34  is displaced toward the right lateral plate  15 , and the spring  28  is compressed and deformed.  FIG. 6B  shows a condition where the spring  28  is sufficiently deformed and is accommodated in the recessed groove  33 , and a forward end surface of the flange portion  34   b  is brought approximately on the same level as an inner end of the spring holder  32 . It is understood that all of the springs  28  are under the condition as shown in  FIG. 6B . 
     The lateral plate sealing member  26  and the holding plate  27  are sequentially inserted into the opening  25 . All of the springs  28  are accommodated in the recessed groove  33 , and the right lateral plate  15  is set into the opening  25 . Then, the right lateral plate  15  is fixed on the top plate  11  and the bottom plate  12  by means of the bolts  29 . 
     Under this condition, the springs  28  are restricted and no pressing force is applied on the holding plate  27 . That is, the right lateral plate  15  receives no reaction force from the holding plate  27 . As a result, positioning can be easily achieved when the right lateral plate  15  is mounted, and the right lateral plate  15  can be mounted in easier manner. 
     When the mounting of the right lateral plate  15  is completed, the spring holding bolts  35  are loosened, and the springs  28  are brought into free condition. Even under the condition where the restriction by the spring holding bolts  35  are left free, the springs  28  are maintained in compressed state, and the restoring forces of the springs  28  are transmitted to the lateral plate sealing member  26  via the holding plate  27 . Because the lateral plate sealing member  26  is made of a highly elastic material, a portion where the end surface of the flat plate  4  is brought into contact is recessed by the restoring forces of the springs  28 . As a result, each of four end surfaces of the flat plate  4  is engaged into the lateral plate sealing member  26 , and the end surfaces of the heat transfer unit  3  are totally closed in air-tight manner by the lateral plate sealing member  26 . 
     The holding plate  27  is not supported physically and is kept in free condition. Because the holding plate  27  is pressed by a number of springs  28 , the holding plate  27  is uniformly brought into touch with end portion of the heat transfer unit  3 , and uniform sealing property can be maintained over the entire end portion. Each of the springs  28  is deformed by the spring supporting bolt  35 , and strong force is not required for the deforming. On the other hand, a number of springs  28  are provided with such distribution as required. As a result, high pressing force and uniform pressing force can be applied on the lateral plate sealing member  26  as a whole. 
     In  FIG. 5B , the spring holding bolt  35  is shown in completely removed state. In fact, however, a forward end of the spring supporting bolt  35  is engaged with the nut portion  34   a . That is, a head of the spring supporting bolt  35  is separated from the right lateral plate  15 . Therefore, even when the restriction by the spring supporting bolt  35  is released, the position of the springs  28  in vertical direction is maintained by the spring supporting bolt  35 . 
     By incorporating the top plate  11 , the bottom plate  12 , the front plate  13 , the rear plate  14 , the right lateral plate  15 , and the left lateral plate respectively, the heat exchanger  1  is set up. The heat transfer unit  3  can be fixed by holding the top plate  11  and the bottom plate  12 . i.e. by holding the front edges  4   a  and  4   b  by means of the edge holding hardwares  18  and  18 , and there is no need to use screws, welding process, etc. Further, at the same time as the fixation of the heat transfer unit  3 , the first flow passage  7  and the second flow passage  8  can be air-tightly separated because the sealing members  6   a  and  6   b  are engaged with the front edges  4   a  and  4   b  respectively. Also, the lateral plate sealing member  26  is pressed and air-tightly sealed at left and right ends of the heat transfer unit  3 . As a result, by simply incorporating the heat transfer unit  3  in the casing  2 , the first flow passage  7  and the second flow passage  8  as air-tightly separated from each other can be formed. 
     The high temperature fluid inlet  21  and the high temperature fluid outlet  22  are communicated with the second flow passage  8 , and the low temperature fluid inlet  23  and the low temperature fluid outlet  24  are communicated with the first flow passage  7 . 
     In the embodiment as given above, due consideration has been given to heat loss, and the low temperature fluid  38  is allowed to pass to the first flow passage  7 , which is in contact with the top plate  11  and the bottom plate  12 . However, in a case where the heat exchanger  1  itself is disposed in the drying chamber, the high temperature fluid  37  may be passed to the first flow passage  7 . 
     The heat exchanger  1  can be disassembled in easy manner, and the heat transfer unit  3  can be easily taken out. For the procedure of disassembling, the procedure to assemble the heat exchanger  1  can be performed in reverse direction. That is, the spring supporting bolt  35  is fastened first to turn to the condition so that reaction force of the spring  28  may not be applied on the right lateral plate  15 , and the right lateral plate  15  and the left lateral plate  16  are removed. By removing the top plate  11  and the bottom plate  12  from the front plate  13  and the rear plate  14  as well as from the support pillars  19  and  19 , all component parts of the heat exchanger  1  can be disassembled (see  FIG. 4 ). 
     Therefore, each component can be cleaned up as a single piece, and the cleaning procedure can be performed in easy and perfect manner. 
     By applying the heat exchanger  1  to the dehumidifier  41 , it is possible to have the dehumidifier  41  with high thermal efficiency and with good maintainability. 
       FIG. 7  shows a variation example of the heat exchanger  1  in the present embodiment. 
     In this variation example, both of the lateral ends (right lateral end in  FIG. 7 ) of the flat plates  4  and  4 , which make up together the second flow passage  8 , are bent and deformed so that both of the lateral ends are superimposed on each other. Further, the superimposed portions of the flat plates  4  and  4  are connected to each other by brazing or welding or the like. By connecting the superimposed portions with each other, both of the lateral ends of the second flow passage  8  can be closed air-tightly, and the second flow passage  8  is completely separated from the first flow passage  7 . Also, it may be so arranged that the lateral ends of the first flow passage  7  are connected together so that the first flow passage  7  are completely separated from the second flow passage  8 . 
     By arranging that the second flow passage  8  is separated from the first flow passage  7 , the low temperature fluid  38  flowing in the first flow passage  7  and the high temperature fluid  37  flowing in the second flow passage  8  do not leak through gap between the flat plate  4  and the lateral plate sealing member  26  and are not mixed with each other even when the lateral plate sealing member  26  is deteriorated. 
     As a result, it can be so arranged that the low temperature fluid  38  and the high temperature fluid  37  can be different in composition and can have different property so that a gas flown along the first flow passage  7  and a liquid is flown along the second flow passage  8 . It is possible to increase universal adaptability of the heat exchanger  1 . 
       FIG. 8  shows a case where the dehumidifier  41  in the present embodiment is applied for the use in a drying chamber to dry up clothes. 
     In  FIG. 8 , reference numeral  66  represents a drying chamber, Heating devices  67  such as stove are installed in the drying chamber  66 , and objects to be dried  68  such as damp clothes are accommodated. 
     A suction pipe  69  and a discharge pipe  71  are connected in the drying chamber  66 . The suction pipe  69  is connected to the dehumidifier  41  via the suction inlet  48 , and the discharge pipe  71  is connected to the dehumidifier  41  via the discharge inlet  51 . 
     When the dehumidifier  41  is operated, the air in the drying chamber  66  is sucked into the dehumidifier  41  via the suction pipe  69 , and the air thus sucked in is dehumidified in the dehumidifier  41 , and the dehumidified air is introduced into the drying chamber  66  via the discharge pipe  71  as dry air. 
     By operating the dehumidifier  41 , the humidity in the drying chamber  66  is decreased. Thus, the objects to be dried  68  can be perfectly dried up even when the temperature in the drying chamber  66  may not be risen. 
     Therefore, by applying the dehumidifier  41  in the drying chamber  66 , there is no need any more to maintain the interior space at high temperature by means of the heating device  67 , and the reduction of the fuel cost can be achieved.