Method for manufacturing fin-tube heat exchanger and combustion apparatus including fin-tube heat exchanger

Abstract

The method for manufacturing a fin-tube heat exchanger includes the step of expanding each heat transfer tube extending through a corresponding tube insertion hole of a heat transfer fin with a tube expander inserted in heat transfer tubes. The expanding step includes a first sub-step of expanding the tube expander in a radial direction of the heat transfer tube to a radially expanded state while the tube expander is at rest in a first predetermined region to be expanded inside the heat transfer tube to bring the first predetermined region to be expanded into close contact with the tube insertion holes; and a second sub-step of releasing the tube expander from the radially expanded state to a radially contracted state and moving the tube expander to a second predetermined region to be expanded inside the heat transfer tube. The first and second sub-steps are alternately repeated.

What is claimed is: 
     
         1 . A method for manufacturing a fin-tube heat exchanger comprising heat transfer fins having tube insertion holes and heat transfer tubes made of aluminum or stainless steel and respectively extending through the tube insertion holes of the heat transfer fins, the method comprising the step of:
 expanding each of the heat transfer tubes extending through the corresponding tube insertion hole with a tube expander inserted in the heat transfer tube, wherein   the expanding step comprises:   a first sub-step of expanding the tube expander in a radial direction of the heat transfer tube to a radially expanded state while the tube expander is at rest in a first predetermined region to be expanded inside the heat transfer tube to bring the first predetermined region to be expanded into close contact with the corresponding tube insertion hole; and   a second sub-step of releasing the tube expander from the radially expanded state to a radially contracted state and moving the tube expander to a second predetermined region to be expanded inside the heat transfer tube, wherein   the first sub-step and the second sub-step are alternately repeated.   
     
     
         2 . The method for manufacturing the fin-tube heat exchanger according to  claim 1 , wherein
 the tube expander comprises:   a cylinder comprising a plurality of head segments divided in a circumferential direction;   a core rod to be respectively pushed from end of the heat transfer tube into opening of the cylinder in the heat transfer tube; and   a conversion mechanism to convert axial pushing force of the core rod into a movement of the head segments in an expanding radial direction, wherein   the core rod is pushed into the cylinder to move the head segments in the expanding radial direction to expand the cylinder to the radially expanded state, and the core rod is pulled from the cylinder to move the head segments in a contracting radial direction to contract the cylinder to the radially contracted state.   
     
     
         3 . A combustion apparatus comprising:
 a fin-tube heat exchanger including:
 heat transfer fins having tube insertion holes; and 
 heat transfer tubes made of aluminum or stainless steel and respectively extending through the tube insertion holes of the heat transfer tubes, wherein 
   a first predetermined region to be expanded inside each of the heat transfer tubes extending through the corresponding tube insertion hole is brought into close contact with the corresponding tube insertion hole with a tube expander that is expanded in a radial direction of the heat transfer tube to a radially expanded state while being at rest in the first predetermined region to be expanded,   the tube expander released from the radially expanded state to a radially contracted state is movable to a second predetermined region to be expanded inside the heat transfer tube, and   the tube expander at rest in the second predetermined region to be expanded is configured to be radially expanded again to the radially expanded state to bring the second predetermined region to be expanded into close contact with the corresponding tube insertion hole.   
     
     
         4 . The combustion apparatus comprising the fin-tube heat exchanger according to  claim 3 , wherein
 the tube expander comprises:   a cylinder comprising a plurality of head segments divided in a circumferential direction;   a core rod to be respectively pushed from end of the heat transfer tube into opening of the cylinder in the heat transfer tube; and   a conversion mechanism to convert axial pushing force of the core rod into a movement of the head segments in an expanding radial direction, wherein   the core rod is pushed into the cylinder to move the head segments in the expanding radial direction to expand the cylinder to the radially expanded state, while the core rod is pulled from the cylinder to move the head segments in a contracting radial direction to contract the cylinder to the radially contracted state.