Heat exchanger and water heater

Abstract

The heat exchanger including a plurality of fluid flow paths ( 401 ), ( 402 ), ( 403 ) arranged in a plurality of stages in a height direction, wherein a fluid inlet port ( 13 a ) and a fluid outlet port ( 13 b ) of the fluid flow path ( 403 ) located at a lowermost stage among the plurality of fluid flow paths ( 401 ), ( 402 ), ( 403 ) have larger flow path cross-sectional areas than a fluid inlet port ( 11 a ) and a fluid outlet port ( 11 b ) of the fluid flow path ( 401 ) located at an uppermost stage.

What is claimed is: 
     
         1 . A heat exchanger comprising:
 a case body including a flow passage of combustion exhaust gas therein;   a plurality of fluid flow paths arranged in a plurality of stages in a height direction along a side wall of the case body;   a distribution header communicating with fluid inlet ports of the plurality of fluid flow paths and distributing a fluid to be heated to the plurality of fluid flow paths; and   a collection header communicating with fluid outlet ports of the plurality of fluid flow paths and collecting the fluid to be heated from the plurality of fluid flow paths, wherein   the fluid inlet port and the fluid outlet port of the fluid flow path located at a lowermost stage among the plurality of fluid flow paths have larger flow path cross-sectional areas than the fluid inlet port and the fluid outlet port of the fluid flow path located at an uppermost stage among the plurality of fluid flow paths, respectively.   
     
     
         2 . The heat exchanger according to  claim 1 , wherein
 the fluid inlet port and the fluid outlet port of a lower-stage fluid flow path located at a lower stage than the fluid flow path located at the uppermost stage among the plurality of fluid flow paths have larger flow path cross-sectional areas than the fluid inlet port and the fluid outlet port of the fluid flow path located at the uppermost stage, respectively.   
     
     
         3 . The heat exchanger according to  claim 1 , wherein
 the fluid inlet port and the fluid outlet port of the fluid flow path located at the lowermost stage among the plurality of fluid flow paths have larger flow path cross-sectional areas than the fluid inlet port and the fluid outlet port of an upper-stage fluid flow path located at a upper stage than the fluid flow path located at the lowermost stage, respectively.   
     
     
         4 . The heat exchanger according to  claim 1 , wherein
 the fluid flow path located at the lowermost stage among the plurality of fluid flow paths is disposed so as to protrude more inwardly of the case body than an upper-stage fluid flow path located at an upper stage than the fluid flow path located at the lowermost stage as viewed from an upstream side of the flow passage of the combustion exhaust gas.   
     
     
         5 . A water heater comprising the heat exchanger according to  claim 1 .