Heat exchanger and dimple tube used in the same, the tube having larger opposed protrusions closest to each end of tube

A heat exchanger comprising:

• a pair of headers provided for circulating refrigerant, each having a plurality of tube insertion openings;
• a plurality of tubes placed between the pair of headers arranged in parallel to each other in a vertical direction, where each tube has two ends which are respectively inserted into the relevant tube insertion openings of the headers;
• cooling fins provided between the tubes arranged in parallel, and wherein:
• each tube comprises a plate folded in two so as to make two edges of the plate contact each other and form a flat tube, wherein:
• the plate comprises protrusions provided on each inner wall of the flat tube in a manner such that the heads of opposed protrusions on both the inner walls contact each other the protrusions are arranged in an inclined checker pattern along the longitudinal direction of the tube, where the longitudinal spans of any two adjacent protrusions on each inclined line of the checker pattern partially overlap each other;
• and
• the plate is clad with a brazing filler metal and the protrusions are formed on a surface of the plate before the plate is folded, and the two edges of the plate ant the heads of the opposed protrusions are respectively made to contact folding the plate, and wherein:
• the assembled headers, tubes, and cooling fins are heated, and the two edges of the plate, the heads of the opposed protrusions, contact portions between the two ends of each tube and the headers, and contact portion between each tube and the cooling fins are respectively brazed;
• and
• the cooling fins are arranged in a manner such that a predetermined number of first sets of the opposed protrusions which are positioned closest to each end of each tube directly receive a pushing force from the cooling fins.