Analytical Reconstruction of Failure of a Shell and Tube Heat Exchanger
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TECHNICAL ARTICLE—PEER-REVIEWED
Analytical Reconstruction of Failure of a Shell and Tube Heat Exchanger Gajendra Vasantrao Patil . M. A. Dharap . R. I. K. Moorthy
Submitted: 11 October 2016 Ó ASM International 2016
Abstract Heat exchanger tubes are supported at intermediate points by support plates. Flow-induced vibration of tube can cause it to impact or rub against a support plate or against adjacent tubes and can result in tube fretting wear. Fretting wear damage assessment procedure has been presented. This procedure is implemented by studying classical heat exchanger cases of premature failures. The authors expect this study to be useful for estimating the fretting wear damage of heat exchanger tubes. The study shows that based on fretting wear volume rate the life of heat exchanger tube can be predicted. Keywords Flow-induced vibration Heat exchanger tube Fretting wear Vortex shedding Finite element simulation List of symbols q v fn D CL xs
Fluid density Free stream velocity Reduced frequency Tube diameter Lift coefficient, dimensionless Circular vortex shedding frequency, radian/s
G. V. Patil (&) M. A. Dharap Veermata Jijabai Technological Institute, Mumbai, Maharashtra 400019, India e-mail: [email protected]; [email protected] G. V. Patil R. I. K. Moorthy Pillai college of engineering, New Panvel, Maharashtra 410206, India
FL qV SFF ;i N Le M C CNL K KNL RtþDt €tþDt ; U_ tþDt ; UtþDt U
f KNL U CNL V ðtÞ k FN Lð t Þ V_ KW WN L dW TEMA
Lift force (force perpendicular to the mean flow) per unit length of tube Mass flux Power spectral density Phase angle Number of harmonics contributing to the total force Element length Mass matrix Linear damping matrix Non-linear damping matrix Linear stiffness matrix Non-linear stiffness matrix External force vector at time t þ Dt Acceleration, velocity, and displacement vectors at time t þ Dt, respectively Contact force Support stiffness Displacement between tube and support Non-linear damping coefficient Worn volume after time T, Specific wear coefficient, Normal contact force between tube and support Sliding distance after time T Fretting wear damage volume rate Specific wear coefficient Normal work rate Support thickness Tube wall wear depth Tubular Exchanger Manufacturer Association
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J Fail. Anal. and Preven.
Introduction In heat exchangers, flow-induced vibrations have led to premature failure of tubes. Even otherwise tube fretting wear because of flow-induced vibration has been recognized as a significant contributor to the life of heat exchanger tube. The mechanisms causing the damaging flow-induced vibrations include ‘Vortex shedding,’ ‘Turbulence buffeting,’ and ‘Fluid elastic instability.’ Vortex shedding occurs when a vortex shedding frequency reaches the natural frequency of the tube, the vortex-shedding frequency does not further increase with flow velocity, the shedding frequency remains ‘locked in’ to the natural frequency of the structure [1]. Heat exchanger tubes respond in a random manner to turbulence in the flow field. Fluid el
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