Flow-Induced Vibration Handbook for Nuclear and Process Equipment. Группа авторов

Flow-Induced Vibration Handbook for Nuclear and Process Equipment - Группа авторов


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rel="nofollow" href="#fb3_img_img_0693b15c-6ad2-51a2-82a8-bfb084fd038a.gif" alt="Graph depicts viscous Damping Data for a Cylinder in Unconfined and Confined Liquids: Comparison Between Theory and Experiment."/> Graph depicts damping Data for Multi-Span Heat Exchanger Tubes in Water. Graph depicts comparison Between Tube Support Damping Model and Experimental Data.

      Damping in Two‐Phase Flow

      The subject of heat exchanger tube damping in two‐phase flow was reviewed by Pettigrew and Taylor (1997) as discussed in Chapter 6. The total damping ratio, ζT, of a multi‐span heat exchanger tube in two‐phase flow comprises support damping, ζS, viscous damping, ζV, and two‐phase damping, ζTP:

      (2‐19)equation

      When there is liquid between the tube and the support, support damping includes both squeeze‐film damping, ζSF, and friction damping, ζF. This situation is analogous to heat exchanger tubes in liquids and the support damping may be evaluated with Eqs. (2.18) and (2.19) above:

      Viscous damping in two‐phase mixtures is analogous to viscous damping in single‐phase fluids (Pettigrew and Taylor, 1997). Homogeneous properties of the two‐phase mixture are used in its formulation, as follows:

      (2‐21)equation

      where vTP is the equivalent two‐phase kinematic viscosity as per McAdams et al (1942):

      (2‐22)equation

      Above 40% void fraction, viscous damping is generally small and could be neglected for the U‐bend region of steam generators. However, it is significant for lower void fractions.

      There is a two‐phase component of damping in addition to viscous damping. As discussed by Pettigrew and Taylor (1997) and in Chapter 6, two‐phase damping is strongly dependent on void fraction, fluid properties and flow regimes, directly related to confinement and the ratio of hydrodynamic mass over tube mass, and weakly related to frequency, mass flux or flow velocity, and tube bundle configuration. A semi‐empirical expression was developed from the available experimental data to formulate the two‐phase component of damping, ζTP, in percent:

      (2‐23)equation

Graph depicts comparison Between Proposed Design Guideline and Available Damping Data. equation

      (2‐24)Скачать книгу