Unusual acoustic vibration in heat exchanger and steam generator tube banks possibly caused by fluid-acoustic instability

Flow channels of heat exchangers or steam generators containing tube arrays can be subject to acoustic vibration excited by flow of air, gas, or steam transversely across the tubes. Such vibration occurs when a flow disturbance inside the tube bank excites a strong acoustic (standing wave) mode of the channel. The acoustic modes typically excited are those related to the dimension perpendicular to both the fluid flow direction and the tube axes. Preventive measures taken in the design stage are typically directed against these commonly existing standing waves. Evidence is presented of the unusual occurrence of standing waves that develop in the flow direction and in the tube axial direction. The causes for their development and methods of suppression are discussed.