FEM analysis for fluid-structure interaction in a dimensional helical tube base on complex mode theroy

Heat transfer enhancement was achieved due to flow-induced vibration in elastic tube bundle heat exchangers. To a further study on heat transfer enhancement mechanism and tube structural optimization, it was of importance to study vibration characteristics of fluid-structure interaction in heat transfer element. A helical tube bundle was a new type elastic heat transfer element. Because of its helical structure, the inside flow of the helical tube has a deep influence on its vibration characteristics due to Coriolis force damping. The FEM was used here to study the vibration characteristics of the helical tube with inside flow. The element matrix and the tube vibration equation were established with the regulation of different spiral angle, coordinate transformation and the simplification of the connector between two pipes. The influence of Coriolis force damping on the tube vibration characteristics was analyzed. The results showed that the 1st modal frequency decreases acutely because of inside flow of helical pipe; the spiral pipe reveals complex modal shapes due to Coriolis force damping; the 1st modal frequency and the damping ratio change with varying of the helical pitch and the speed of the inside flow.