Heat exchanger

Abstract

Outsides of flat tubes through which a first fluid flows are formed with wave-shaped surfaces, and fins form meandering passages for a second fluid. While the second fluid is flowing along the fins, it is made turbulent by striking the wave-shaped surfaces of the flat tubes due to the meandering passages. The turbulent flow contacts the outside surfaces of the flat tubes and the front and rear surfaces of the fins, so heat conduction is promoted without the formation of thick boundary layers at these surfaces. Therefore, the heat exchange efficiency is remarkably improved between the first fluid such as warm water flowing through the insides of the flat tubes and the second fluid such as air flowing at the outsides.

What is claimed is:  
     
         1 . A heat exchanger provided with a plurality of flat tubes forming passages for a first fluid inside them and having outside surfaces formed to a wave shape so that passages for a second fluid flowing at the outsides of said flat tubes meander in a wave shape and plate-shaped fins for guiding the second fluid at the outsides of said flat tubes forming the passages for the second fluid.  
     
     
         2 . A heat exchanger as set forth in  claim 1 , wherein said flat tubes are fabricated by bending corrugated sheets to tubular shapes and joining their seams.  
     
     
         3 . A heat exchanger as set forth in  claim 1 , wherein said flat tubes are formed by joining pairs of corrugated sheets.  
     
     
         4 . A heat exchanger as set forth in  claim 1 , wherein said flat tubes are provided with reinforcing plates at their insides.  
     
     
         5 . A heat exchanger as set forth in  claim 1 , wherein said flat tubes are fabricated by extrusion so that passages for a first fluid are formed inside.  
     
     
         6 . A heat exchanger as set forth in  claim 1 , wherein a longitudinal direction of said plate-shaped fins is substantially vertical to a longitudinal direction of said flat tubes.  
     
     
         7 . A heat exchanger as set forth in  claim 6 , wherein said plate-shaped fins are bent back at the ends in their longitudinal directions.  
     
     
         8 . A heat exchanger as set forth in  claim 6 , wherein a plurality of said plate-shaped fins form a fin assembly by being connected through leg parts like a multilevel shelf.  
     
     
         9 . A heat exchanger as set forth in  claim 1 , wherein said fins are bonded to the tops or bottoms of wave-shaped surfaces formed at the outside surfaces of said flat tubes.  
     
     
         10 . A heat exchanger as set forth in  claim 8 , wherein said leg parts of said fin assembly are bonded to the tops or bottoms of wave-shaped surfaces formed at the outside surfaces of said flat tubes and windows for passing the second fluid are formed by said leg parts.