| 摘要 |
PROBLEM TO BE SOLVED: To prevent any abnormal sound from being produced and the life thereof from being shortened owing to local heating of a combustion cylinder in a heat exchanger which is incorporated into a petroleum hot water heater and a warm water boiler, etc. SOLUTION: A discharge hole 13a of a return tube 13 is opened, directed downward just above the center of an upper surface of a combustion cylinder 3. Hereby, a non-freezing fluid from the return tube 13 is discharged toward the neighbourhood of the center of the upper surface of the combustion cylinder 3 (a portion most heated with combustion of the burner). For this, temperature rise of that portion is restricted, and hence local heating of the combustion cylinder 3 is arrested.
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