STV-17 Parallel Flow-induced Tube Vibration in Shell-and-tube Heat Exchangers
Tube vibration in parallel flow arises from unsteady pressures occurring on tube surfaces. Vibration is predicted via traditional empirical correlations or via random vibration theory. For both approaches, however, the forcing function is most accurately determined by in situ testing. The unsteady pressures in industrial flows, added to those in the turbulent boundary layer alone, complicate the definition of fluctuating pressure power spectral density functions, which can vary by more than 40 dB. This report describes the vibration phenomena, the current HTRI prediction method and its deficiencies, and several alternative prediction schemes. The lack of accurate measured data in shell-and-tube heat exchangers makes it challenging to exceed the order of magnitude accuracy recorded in the literature for any predictive method. Renewed interest in heat exchangers having more longitudinal flow (e.g., those with electric heater rods) motivates this review. Compared to the current HTRI method, the joint acceptance approach for predicting vibration amplitude due to tubeside and shellside parallel flow includes important structural and excitation input parameters and accommodates more relevant fluctuating power spectral density and coherence functions, when available. Additional measurements are needed to confirm whether the dielectric powder packing in electric heater rods provides more damping than that of conventional metallic tubes.