Fretting Wear Damage of Heat Exchanger Tubes: A Proposed Damage Criterion Based on Tube Vibration Response

Abstract

A simple criterion is proposed to estimate fretting wear damage in heat exchanger tubes with clearance supports. The criterion is based on parameters such as vibration frequency, midspan vibration amplitude, span length, tube mass, and an empirical wear coefficient. It is generally accepted that fretting wear damage is proportional to a parameter called work rate. Work rate is a measure of the dynamic interaction between a vibrating tube and its supports. Due to the complexity of the impact-sliding behavior at the clearance supports, work rate calculations for heat exchanger tubes require specialized nonlinear finite element codes. These codes include contact models for various clearance support geometries. Such nonlinear finite element analyses are complex, expensive and time consuming. The proposed criterion uses the results of linear vibration analysis (i.e., vibration frequency and mid-span vibration amplitude due to turbulence) and does not require a nonlinear analysis. It can be used by nonspecialists for a quick evaluation of the expected work rate, and hence, the fretting wear damage of heat exchanger tubes. The proposed criterion was obtained from an extensive parametric study that was conducted using a nonlinear finite element program. It is shown that, by using the proposed work rate criteria, work rate can be estimated within a factor of two. This result, however, requires further testing with more complicated flow patterns.

A Simulation of the Turbulence Response of Heat Exchanger Tubes in Lattice-Bar Supports

“…The work of Yetisir et al (1997) utilized the input energy of the constrained system. However, in the present work, consistent with the rest of the dimensionless set, the input power is calculated based on the unconstrained modes.…”

“…The values of the work rate were normalized by the input power due to turbulence. The total power absorbed by a tube of length L and mass per unit length m, was expressed by Yetisir et al (1997) as…”

A new tube/support impact model for heat exchanger tubes

“…Normal work rate ðW N Þ is normalized by the input power induced by turbulence ðW tur Þ. The total power absorbed by a tube of length (L) and mass per unit length (m) was expressed by Yetisir et al (1998):…”

Modal localization in mistuned tube-array structures

“…1016/j.ijsolstr.2008.01.019 defects are commonly formed near the center of the tubes due to impact friction and wear during operation. Such abrasions are common in heat exchange systems operated under severe conditions Tsai (1987, 1988) and Yetisir et al (1998). However, their presence is clearly undesirable in critical cooling systems such as those used in nuclear power plants.…”