Effect of material on fluid elastic instability of parallel triangular tube array subjected to water cross

Abstract

The effect of tube material and structure on fluid elastic instability is examined experimentally using a parallel triangular finned tube array with a P/D ratio of 1.78. Flow-induced vibration is a common cause of failure in shell and tube heat exchangers, and it may result in substantial harm to the heat exchanger as well as significant financial loss. There are different mechanisms responsible for flow induced vibration out of which fluid elastic instability and vortex shedding are the most severe due to their sudden occurrence and high amplitude of vibration. Different parameters affect the tube vibration when the tube array is subjected to water crossflow. In this paper effect of tube material and fin are examined for fluid elastic instability. Experimentation was performed to measure demanding velocity at fluid elastic instability for plain and finned tubes for steel, aluminum and copper material. A fully flexible tube array with a cantilever end condition and with a constant pitch ratio subjected to water cross flow was considered. Testing was done with a gradually increasing water flow rate from 5 m3/hr and increases up to 75 m3/hr to obtain fluid elastic instability. The relationship between the critical velocity at fluid elastic instability and the mass damping parameter was investigated using Connor's equation. The amplitude response of vibration concerning the change in velocity shows that the addition of fins, as well as the material change, greatly affects the fluid elastic instability. A small peak before the occurrence of fluid elastic instability was observed. This is maybe due to vortex shedding which further required to be verified using the Strouhal number.