An Improved Model to Study the Density Wave Oscillation in Tubes by Using Frequency Domain Method

Density Wave Oscillation (DWO) in tubes was usually studied by using the frequency domain method. However, in the conventional model, the heat storage of wall metal was usually neglected to simplify the complex solving process of transfer functions, which might cause unreasonable results when the tube wall had a thick wall or complex geometry structures. Hence, in the present paper, an improved mathematical model was proposed based on the frequency domain theory to theoretically study the DWO in tubes. The present model was an improvement of the conventional model. The most notable improvement in the present model was that the heat storage of the tube wall metal, the internal wall heat flux and the external wall heat flux were all considered as dynamic parameters. Based on the improvement, the prediction of the DWO in tubes by using the present model might be more accurate and reasonable than that by using the conventional model, and this was proved by the comparison of the results obtained with the two models to the experimental results gained from literature. In the present study, it was shown that both the present model and the conventional model could predict the DWO in tubes well when the tube wall was thin, and it was also found that the present model was more appropriate than the conventional model when the tube wall was thick. Both the thickness of the tube wall and the specific heat of tube wall metal play negative roles in the system stability.