Heat exchanger

Abstract

A plurality of heat-exchange tubes 30 each including a flat pipe including a groove 36 and wavelike depression-and-projection portions 33, 34 are arranged in parallel in such a manner that each of respective longitudinal directions thereof is a vertical direction, and a heat exchange medium is made to flow from an inlet 31 at each lower portion to an outlet 32 at each upper portion. Guide walls 43, 44 are provided in a shell 40 , and exhaust gas is made to flow an inlet 41 at an upper portion to an outlet 42 at a lower portion, thereby making the exhaust gas meander in flow paths 46 a to 46 d and a space between the plurality of heat-exchange tubes 30 . The exhaust gas and the heat exchange medium have flows opposed to each other as a whole, and a secondary flow of the exhaust gas is made to occur by the wavelike depression-and-projection portions 33, 34 , thereby enhancing the heat exchange efficiency, and the arrangement in such a manner that each of the longitudinal directions is the vertical direction and the formation of a groove 36 and the wavelike depression-and-projection portions 33, 34 enable acceleration of downward discharge of condensed water.

1 . A finless heat exchanger for recovering heat of exhaust gas resulting from combustion via heat exchange between said exhaust gas and a heat exchange medium, the heat exchanger comprising:
 a plurality of heat-exchange tubes each formed as a flat pipe using a metal plate material having an excellent acid corrosion resistance, said plurality of heat-exchange tubes being arranged in parallel in such a manner that each of respective longitudinal directions thereof is mainly a vertical direction; and   a shell that houses said plurality of heat-exchange tubes and forms a flow path for said exhaust gas to pass therethrough between said plurality of heat-exchange tubes and said shell,   wherein said plurality of heat-exchange tubes each include an inlet for said heat exchange medium at a vertically lower portion thereof and an outlet for said heat exchange medium at a vertically upper portion thereof;   wherein said shell includes an inlet for said exhaust gas at a vertically upper portion thereof and an outlet for said exhaust gas at a vertically lower portion thereof, and   wherein said plurality of heat-exchange tubes and/or said shell include a meandering guiding section formed so that said exhaust gas flows in a space between the plurality of heat-exchange tubes while meandering downward from the vertically upper portion.   
     
     
         2 . A heat exchanger according to  claim 1 , wherein said plurality of heat-exchange tubes each include a vertical groove at a substantial center of a flat surface thereof. 
     
     
         3 . A heat exchanger according to  claim 2 , wherein said groove in each of said plurality of heat-exchange tubes is fixed by bonding inside the heat-exchange tube. 
     
     
         4 . A heat exchanger according to  claim 1 , wherein said meandering guiding section includes a guide wall formed inside said shell so that said exhaust gas flows in a substantially horizontal direction orthogonal to said plurality of heat-exchange tubes. 
     
     
         5 . A heat exchanger according to  claim 4 , wherein said meandering guiding section includes a rib formed toward said guide wall at a flat surface of each of said plurality of heat-exchange tubes at a position aligned with said guide wall of said shell, in addition to said guide wall. 
     
     
         6 . A heat exchanger according to  claim 1 ,
 wherein said meandering guiding section includes a plurality of ribs formed at a plurality of positions in a substantially horizontal direction on a flat surface of each of said plurality of heat-exchange tubes; and   wherein an inner side of an outer wall of said shell is in contact with one side surface and another side surface alternately from an uppermost position to a lower position from among opposite side surfaces of said plurality of heat-exchange tubes at positions where said plurality of ribs are formed and is not in contact with a side surface opposite to said side surface that is in contact with the inner side from among opposite side surfaces at a same position.   
     
     
         7 . A heat exchanger according to  claim 1 , wherein said plurality of heat-exchange tubes each include a plurality of wavelike depression-and-projection portions formed over a substantial entirety of a flat surface thereof, each of said plurality of wavelike depression-and-projection portions including a depression portion and a projection portion flexed at an angle ranging from 10 to 80 degrees relative to a main flow direction of said exhaust gas to be continuous with each other. 
     
     
         8 . A heat exchanger according to  claim 7 , wherein said plurality of heat-exchange tubes are each formed so that an angle of said wavelike depression-and-projection portions in a region positioned in a vertically upper portion of the flat surface relative to the main flow direction of said exhaust gas is smaller than an angle of said wavelike depression-and-projection portions in a region positioned in a vertically lower portion of the flat surface relative to the main flow direction of said exhaust gas. 
     
     
         9 . A heat exchanger according to  claim 8 , wherein said plurality of heat-exchange tubes are each formed so that the angle of said wavelike depression-and-projection portions in the region positioned in the vertically upper portion of the flat surface relative to the main flow direction of said exhaust gas falls within a range of 10 to 45 degrees and the angle of said wavelike depression-and-projection portions in the region positioned in the vertically lower portion of the flat surface relative to the main flow direction of said exhaust gas falls within a range of 45 to 80 degrees.