Dynamic Flow Instability of Natural Circulation Heat Recovery Steam Generators
Heimo Walter
This paper presents the results of a theoretical stability analysis of a Heat Recovery Steam Generator (HRSG) with a horizontal tube bank. The investigation was done for different configurations of a natural circulation HRSG at low system pressure. In these cases the dynamic flow instability, namely the density wave oscillations, was analysed. The investigations of the HRSG show that changes of the bundle geometry can improve the flow stability under operating conditions where density wave oscillations occur. To improve the flow stability the flow resistance at the tube inlet (single phase flow) of the bundle heating surface should be increased. A faster decay of the density wave oscillations will be also achieved by the homogenization of the heat absorption in the individual layers of the bundle heating surface. This provision should be combined with additional flow resistance at the tube inlet.