| 摘要 |
PROBLEM TO BE SOLVED: To solve a problem that an air stagnant area is generated on a leeward side of a collar portion 3 provided in each tube insertion hole 2 of a plate fin 4.SOLUTION: A hole edge waveform portion 6 is formed around each collar portion 3 and an intermediate waveform portion 5 is formed in an intermediate portion between the adjacent collar portions 3. The intermediate waveform portions 5 and the hole edge waveform portions 6 are bent into cross-sectional waveforms while being staggered by half pitches and boundaries between the intermediate waveform portions 5, and the hole edge waveform portions 6 are connected by an inclined surface 7. |
