Abstract
A boiler and a heat exchanger ate widely used in various plants such as power plants and chemical plants. However unexpected high level sounds are generated when these plants are operated and it becomes a serious problem. This kind of problem is called the acoustic resonance and it has been considered that the resonance generates when the frequency of the vortex shedding behind the tube bank coincides the natural frequency of the duct system. When a boiler was test operated on ahead at one factory, unexpected high level sounds were generated Then I examined the cause and the countermeasure based on measured data of sounds. As a result, it was clarified that the cause was the acoustic resonance and the insertion of the long baffle plate was effective as the countermeasure. In addition, the counter mechanism ofthe insertion of the baffle plate was not arising the resonance frequency ofthe duct but the decreasing of the energy which the vortex gives to the acoustic field of the duct.
