Linear Analysis And Correction Of Data Of Influence Of Vapor-liquid-solid Flow On Tube Vibration

Vapor- liquid- solid fluidized bed evaporator has a good capacity in both enhancing the heat transfer process and descaling, thus having a wide industrial application prospect. However, in order to evaluate the feasibility of this technique, the influence on the pipe vibration order and the possible damage of three-phase boiling flow inside the tube should be investigated when the evaporator was made of fragile materials such as graphite. In this paper, time- series data such as accelerations at different axial locations was measured for graphite heating tube of vapor- liquid-solid fluidized bed evaporator. Time domain and frequency domain analyses were also performed to discuss the influence of three-phase flow on vibration behavior of the graphite tube. The fluid state in the tube and its impact strength to the tube was investigated based on parameters including circulation flow rate, pressure drop and heat transfer coefficient.Firstly, vibration tests by knocking were performed under three conditions including free hanging, clamping on the device and water filling to determine the inherent frequency of the tube and the sampling frequency of the acceleration.Secondly, tests on tube vibrations, circulation flow rate, pressure drop and heat transfer coefficients we re performed for vapor- liquid flow. Statistical analysis results of standard deviation and kurtosis of vibration acceleration time series show that, with the increase of heating stream pressure, the standard deviation of vibration acceleration at different axial locations, the circulation flow rate and heat transfer coeffic ient of fluid in vapor and liquid phase became larger while the kurtosis decreased. The pressure drop parameter presented a fluctuate character.Finally, vibration test on the tube under three-phase flow was performed. Average power spectral density analys is of the vibration acceleration time series of the tube shows that, with the increase of the heating stream pressure, particle diameter and hold up, the value of resonance peak of each order induced by fluid became larger. Besides, resonance peak of each order in higher frequency gradually developed from clear single peaks to broad peak. With the increase of the heating stream pressure, the resonance peak tends to move to lower frequency. With the increase of the heating stream pressure, particle diameter and hold up, the standard deviation of vibration acceleration time series at three axial locations of the tube also became larger. The change of the kurtosis is relatively complicated and was influenced by many factors such as volume fraction, velocity and diameter of the particles and bubbles in the fluid in the test regions. Kurtosis could be used to determine the state of the fluid in the tube. Moreover, the effect of heating stream pressure, particle diameter and hold up on parameters such as circulation flow rate, pressure and heat transfer coefficient was further studied in this work. The results show that, with the increase of heating stream pressure, the circulation flow rate of the three-phase fluid, pressure drop as well as the heat transfer coefficient became larger. In contrast, the particle diameter and particle volume fraction have complicated effects o n those parameters and comprehensive analysis combining the vibration test results are required. Carbon was found in the wear products of fluidized bed,and it proved that the particles could cause damage the graphite tube.