Patent Publication Number: US-2011057047-A1

Title: Hot air heater

Description:
This application claims priority under 35 U.S.C. §119 to Japanese Patent Application No. 2009-206672, filed Sep. 8, 2009, which is incorporated by reference. 
     BACKGROUND 
     1. Technical Field 
     The present invention relates to a hot air heater (or forced flue heater) that heats the room air by combustion gas from a burner through a heat exchanger. 
     2. Related Art 
     As this kind of hot air heater, there is known one having the following construction. Within a housing having formed therein an inlet port for sucking room air and an outlet port, there are housed a circulation fan, a burner, and a heat exchanger which is arranged to cause to flow combustion gas (or flue gas) from the burner through an inside of the heat exchanger. The air sucked from the inlet port by the operation of the circulation fan is heated by the heat exchanger and is blown out of the outlet port as hot air (see, e.g., Patent Document 1). 
     Although not disclosed in Patent Document 1, this kind of hot air heater is provided with a supporting plate for supporting the heat exchanger inside the housing. The supporting plate is ordinarily constituted by a simple plate member and is generally fixed to the inside of the housing by means of screws. 
     It is, however, to be noted that the heat exchanger, when a fuel is burned in the burner, will reach a relatively high temperature. The heat from the heat exchanger will be transmitted through the supporting plate to that part of the housing to which the supporting plate is fixed by screwing, with the result that such a part will reach a high temperature. 
     Patent Document 1: JP-A-2003-121004 
     SUMMARY 
     In view of the above problems, it is an advantage of the invention to provide a hot air heater in which the temperature increase in the housing by heat transmission through the supporting plate can be limited and in which the thermal efficiency can be improved. 
     In order to solve the above-mentioned problems, this invention is a hot air heater comprising: a housing having formed therein an inlet port for sucking room air and an outlet port; a circulation fan, a burner, and a heat exchanger, all being housed in the housing. The heat exchanger is arranged to cause combustion gas from the burner to flow through an inside of the heat exchanger so that the room air sucked by operating the circulation fan into the inlet port is heated by the heat exchanger for blowing forward as hot air out of the outlet port. In the above-mentioned hot air heater, a supporting plate is disposed to support the heat exchanger inside the housing, and the supporting plate is provided with a radiating fin. 
     According to the invention, the heat that is transmitted from the heat exchanger to the supporting plate is radiated from the radiating fin. The amount of heat to be transmitted to the housing through the supporting plate is reduced and, consequently, the temperature increase in the housing can be limited. At the same time, since the air flowing around the supporting plate gets heated by the heat radiation from the radiating fin, the thermal efficiency is improved. 
     Preferably, the radiating fin is disposed such that a plate surface of the fin obliquely crosses the direction of flow of the air from the circulation fan. According to this arrangement, the heat exchange between the radiating fin and the flow of the air is performed efficiently. As a result, the reduction in the amount of heat transfer to the housing and also the heating of the air can be accelerated. 
     In this invention, preferably, the radiating fin is made up of a cut-and-raised piece formed in the supporting plate. According to this arrangement, unlike a case in which a radiating fin in the form of a member separate from the supporting plate is fixed to the supporting plate, the cost can be reduced by minimizing the number of constituent parts. Further, the opening that is formed by the cut-and-raised piece of the radiating fin contributes to the reduction in the heat transfer area of the supporting plate. Consequently, the amount of heat transfer to the housing can further reduced. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will now be described with reference to the accompanying drawings in which: 
         FIG. 1  is a perspective view of a hot air heater according to an embodiment of this invention; 
         FIG. 2  is a sectional side view of the hot air heater according to the embodiment of this invention; 
         FIG. 3  is a sectional front view taken along the line III-III in  FIG. 2 ; 
         FIG. 4  is an enlarged plan view, partly shown in section, of a main part taken along the line IV-IV in  FIG. 3 ; and 
         FIG. 5  is a perspective view of a main part of the hot air heater according to an embodiment of this invention. 
     
    
    
     DESCRIPTION OF EXEMPLARY EMBODIMENTS 
     With reference to  FIGS. 1 through 3 , reference numeral  1  denotes a housing of a hot air heater according to an embodiment of this invention. The housing  1  is made up of: a main body constituted by a rear plate part  11 , a right-side side-plate part  12  and a left-side side-plate part  12 , a top plate part  13 , and a bottom plate part  14 ; and a front panel  15  which covers the front surface of the main body. There are formed, on an upper portion of the rear plate part  11 , an inlet port la for sucking the room air and, on a lower part of the front panel  15 , an outlet port lb. 
     On the top plate part  13  of the housing  1  there is provided an operation panel  16 . Further, on an outer surface of the rear plate part  11  of the housing  1 , there is disposed a guard frame  17  which encloses the piping space among a supply and exhaust duct (not illustrated) which extends outdoors, an exhaust pipe  53 , and a combustion fan  6 . 
     At an upper inside portion of the housing  1  there is housed a circulation fan  2 . The circulation fan  2  is disposed inside a fan casing  21  which faces the inlet port  1   a , and is constituted by an oblong cross flow fan driven by a motor  22 . 
     Inside the housing  1  there is defined an air passage  3  which connects the fan casing  21  and the outlet port  1   b  together. The air passage  3  is enclosed by: the rear plate part  11 ; a first lateral partition plate  31  which is disposed on the inside of the left-side side-plate part  12  (left as seen in  FIG. 3 ); a second lateral partition plate  32  which extends downward from the right end part, as seen in  FIG. 3 , of the fan casing  21 ; a lower partition plate  33  which is disposed slightly below the lower end of the outlet port  1   b ; and a front partition plate  34  which extends downward from the front edge of the fan casing  21 . 
     Inside the housing  1  there is further housed a cylindrical burner  4  which is supplied with a fuel gas through a gas valve unit  41  and a pipe  42  connected thereto, the burner  4  being housed in a manner to pass through a lower part of the second lateral partition plate  32 . There is also housed a heat exchanger  5  which is positioned inside the air passage  3  and which causes the combustion gas (flue gas) of the burner  4  to flow through the inside. It is thus so arranged that the room air sucked from the inlet port  1   a  by operating the circulation fan  2  is heated by the heat exchanger  5  and is blown out of the outlet port  1   b  into the room as hot air. 
     Inside the housing  1  there is also housed a combustion fan  6  which supplies the burner  4  with outside air as combustion air through an air supply duct section of the supply and exhaust duct. The combustion fan  6  is constituted by a centrifugal fan which is driven by a motor  62  and which is disposed inside a fan casing  61  that is fixed to the rear plate part  11  of the housing  1 . In addition, a humidification water reservoir  7  to be filled with water is disposed below the lower partition plate  33 . It is thus so arranged that the hot air is supplied with steam through an opening  33   a  formed through the lower partition plate  33 . That lower end part  15   a  of the front panel  15  which lies below the outlet port  1   b  is arranged to be detachable so that the humidification water reservoir  7  can be taken out of position for refilling it with water. 
     The heat exchanger  5  is provided with: a combustion tube  51  which extends leftward as seen in  FIG. 3  from the burner  4 ; a bellows-type of heat exchange tube  52  which is laterally disposed above the combustion tube  51 ; and an exhaust pipe  53  which is laterally disposed between the combustion tube  51  and the heat exchange tube  52 . The left end of the combustion tube  51 , which corresponds to the downstream end thereof, and the left end of the heat exchange tube  52 , which corresponds to an upstream end thereof, are brought into fluid flow communication with each other through a box  54 . Also, the right end of the heat exchange tube  52 , which corresponds to the downstream end thereof, and the right end of the exhaust pipe  53 , which corresponds to the upstream end thereof, are brought into fluid flow communication with each other through a box  55 . It is thus so arranged that the combustion gas (flue gas) flows through the combustion tube  51 , the box  54 , the heat exchange tube  52 , and the box  55  into the exhaust pipe  53 . The downstream end of the exhaust pipe  53  is projected out of the rear surface of the housing  1  through the rear plate part  11  and is connected to an exhaust duct part of the supply and exhaust duct. 
     The heat exchanger  5  is supported by a supporting plate  8  inside the housing  1 . As shown in  FIGS. 4 and 5 , this supporting plate  8  has: a front plate part  81  which is fixed with screws  81   a  to a fixing part  31   a  formed by cutting and raising the first lateral partition plate  31 ; and a side plate part  82  which is bent rearward from laterally inner edge part of the front plate part  81  and which is fixed with screws  82   a  to the outside surface of the box  54  of the heat exchanger  5 . On a laterally outward edge part of the front plate part  81 , there is formed, by bending, a flange part  83  which is intended to close the openings that were formed as a result of cutting and raising of the fixing part  31   a  of the first lateral partition plate  31 . On a rear edge part of the side plate part  82 , there is formed, by bending, a flange part  84  which comes into abutment with the rear plate part  11  of the housing  1 . The flange part  84  is engaged with a hook part  11   a  provided in the rear plate part  11  at an engaging hole  84   a  that is formed in the flange part  84 . 
     With the above-mentioned arrangement as it is, the heat from the heat exchanger  5  will be transmitted through the supporting plate  8  to the first lateral partition plate  31  or to the rear plate part  11 , with the result that the housing  1  rises in temperature. 
     As a solution, in this embodiment, there are disposed a plurality of radiating fins  85  in the front plate part  81  and in the side plate part  82 , respectively, of the supporting plate  8 . According to this arrangement, the heat transmitted from the heat exchanger  5  to the supporting plate  8  is radiated from the radiating fins  85 . The amount of heat to be transmitted to the housing  1  through the supporting plate  8  is reduced and, consequently, the temperature rise in the housing  1  can be limited. At the same time, the air that flows around the supporting plate  8  is heated by radiation from the radiating fins  85 . In other words, the supporting plate  8  functions efficiently as a heat exchange member, and the thermal efficiency also improves. 
     Each of the radiating fins  85  is disposed in a manner such that the plate surface thereof obliquely crosses the direction of flow of the air from the circulation fan  2  (i.e., crosses the vertical direction at an inclination). Therefore, the heat exchange takes place efficiently between the radiating fins  85  and the air flow, with the result that the reduction in the amount of heat transfer to the housing  1  and also the heating of the air can be accelerated. 
     Alternatively, it may be considered to form the radiating fins  85  in a plate member that is separate from the supporting plate  8  and then to fix the radiating fins  85  to the supporting plate  8  by means of welding, and the like. This solution, however, brings about an increase in the number of parts and a higher cost. 
     As a solution, in this embodiment, the radiating fins  85  are constituted by cut-and-raised pieces that are formed in the supporting plate  8 . According to this arrangement, the radiating fins made of separate members are not required, and the cost can be reduced. In addition, the heat transmitting area of the supporting plate  8  is narrowed due to the presence of the holes  85   a  that are formed as a result of cutting-and-raising of the radiating fins  85 . Therefore, the amount of heat transmission to the housing  1  is further reduced, and the temperature rise in the housing  1  can more effectively be limited. 
     A description has so far been made of an embodiment of this invention. This invention is, however, not limited to the above-mentioned embodiment. For example, although in the above-mentioned embodiment, the outdoor air is supplied to the burner  4  as combustion air, it is also possible to supply the indoor air to the burner  4  as combustion air.