The average temperature of frozen soil wall is an essential parameter in the process of design, construction, and safety manage- ment of artificial ground freezing engineering. It is the basis of calculating frozen s...The average temperature of frozen soil wall is an essential parameter in the process of design, construction, and safety manage- ment of artificial ground freezing engineering. It is the basis of calculating frozen soil＇s mechanical parameters, fiarther prediction of bearing capacity and, ultimately, safety evaluation of the frozen soil wall. Regarding the average temperature of sin- gle-row-piped frozen soil wall, this paper summarizes several current calculation methods and their shortcomings. Furthermore, on the basis of Bakholdin＇s analytical solution for the temperature field under straight single-row-piped freezing, two new calcula- tion models, namely, the equivalent trapezoid model and the equivalent triangle model, are proposed. These two approaches are used to calculate the average temperature of a certain cross section which indicates the condition of the whole frozen soil wall. Considering the possible parameter range according to the freezing pipe layout that might be applied in actual construction, this paper compares the average temperatures of frozen soil walls obtained by the equivalent trapezoid method and the equivalent tri- angle method with that obtained by numerical integration of Bakholdin＇s analytical solution. The results show that the discrepancies are extremely small and these two new approaches are better than currently prevailing methods. However, the equivalent triangle method boasts higher accuracy and a simpler formula compared with the equivalent trapezoid method.展开更多
Aiming at the high temperature corrosion in a coal-fired boiler,the effect of H2S and SO2 on the corrosion of 12 CrlMoV under the water wall condition has been investigated by experiments.The results indicate that H2 ...Aiming at the high temperature corrosion in a coal-fired boiler,the effect of H2S and SO2 on the corrosion of 12 CrlMoV under the water wall condition has been investigated by experiments.The results indicate that H2 S can promote the corrosion significantly,and the coarse porous oxide film formed cannot stop the progress of corrosion.While SO2 presents little effect on the corrosion.The main composition of the surface of 12 CrlMoV corrosion products is Fe2 O3.With H2S in the atmosphere,the corrosion gradually develops into deeper layers by forming FeS,FeO and Fe2 O3 alternately.The corrosion rate is doubled for every 50℃ inerease in temperature at 400-500℃.展开更多
A thermal-hydrodynamic coupling model is used to investigate the interplay between the wall temperature distribution and the bubble departure during the nucleate boiling process.The boiling process is modeled as the c...A thermal-hydrodynamic coupling model is used to investigate the interplay between the wall temperature distribution and the bubble departure during the nucleate boiling process.The boiling process is modeled as the combination of three subprocesses:the transient heat conduction process in the solid heater,the evaporation of the microlayer underneath the bubble,and the bubble dynamics in the two-phase bulk fluid region.The moving bubble interface is captured by the volume of fluid method in the OpenFOAM framework.The proposed model is validated against the experimental results of the boiling process of the water on an Indium Tin Oxide heater.The predicted results agree well with related measurements in the literature.Following the validation,the effects of the boiling heat flux on the bubble departure period are examined.The results show that the bubble departure period decreases with the increase of the applied heat flux.High heat flux will cause irregularity in the departure periods for successive bubbles due to the influence of the wake flow evoked by the rising bubble.Furthermore,the influence of the bubble contact angle on the boiling heat-transfer performance is investigated.It is confirmed that the bubble departure diameter increases with the increase of the contact angle,meanwhile,the average wall temperature decreases with the increase of the contact angle.展开更多
This study presents a parameter selection strategy developed for the Stretch-Blow Molding (SBM) process to minimize the weight of preforms used. The method is based on a predictive model developed using Neural Network...This study presents a parameter selection strategy developed for the Stretch-Blow Molding (SBM) process to minimize the weight of preforms used. The method is based on a predictive model developed using Neural Networks. The temperature distribution model of the preform was predicted using a 3-layer NN model with supervised backpropagation learning. In addition, the model was used to predict the uniform air pressure applied inside the preform, taking into account the relationship between the internal air pressure and the volume of the preform. Parameters were validated using in situ tests and measurements performed on several weights and lengths of a 0.330 Liter Polyethylene Terephthalate (PET) bottles. Tests showed that the model adequately predicts both the blowing kinematics, mainly zone temperatures and blowing and stretching pressures along the walls of the bottle while maintaining the bottle strength and top load requirements. In the second step, the model was combined to automatically compute the lowest preform weight that can be used for a particular 330 ml bottle design providing a uniform wall thickness distribution.展开更多
基金supported by the National Natural Science Foundation of China (No. 50578120)the National High Technology Research and Development Program of China (863 Program) (No. 2006AA11Z118)
文摘The average temperature of frozen soil wall is an essential parameter in the process of design, construction, and safety manage- ment of artificial ground freezing engineering. It is the basis of calculating frozen soil＇s mechanical parameters, fiarther prediction of bearing capacity and, ultimately, safety evaluation of the frozen soil wall. Regarding the average temperature of sin- gle-row-piped frozen soil wall, this paper summarizes several current calculation methods and their shortcomings. Furthermore, on the basis of Bakholdin＇s analytical solution for the temperature field under straight single-row-piped freezing, two new calcula- tion models, namely, the equivalent trapezoid model and the equivalent triangle model, are proposed. These two approaches are used to calculate the average temperature of a certain cross section which indicates the condition of the whole frozen soil wall. Considering the possible parameter range according to the freezing pipe layout that might be applied in actual construction, this paper compares the average temperatures of frozen soil walls obtained by the equivalent trapezoid method and the equivalent tri- angle method with that obtained by numerical integration of Bakholdin＇s analytical solution. The results show that the discrepancies are extremely small and these two new approaches are better than currently prevailing methods. However, the equivalent triangle method boasts higher accuracy and a simpler formula compared with the equivalent trapezoid method.
基金supported by the National Key Research and Development Plan of China (No. 2018YFB0604203)
文摘Aiming at the high temperature corrosion in a coal-fired boiler,the effect of H2S and SO2 on the corrosion of 12 CrlMoV under the water wall condition has been investigated by experiments.The results indicate that H2 S can promote the corrosion significantly,and the coarse porous oxide film formed cannot stop the progress of corrosion.While SO2 presents little effect on the corrosion.The main composition of the surface of 12 CrlMoV corrosion products is Fe2 O3.With H2S in the atmosphere,the corrosion gradually develops into deeper layers by forming FeS,FeO and Fe2 O3 alternately.The corrosion rate is doubled for every 50℃ inerease in temperature at 400-500℃.
基金the National Key Research and Development Program of China(Grant No.2013GB113005B)the the National Natural Science Foundation of China(Grant No.51976026)。
文摘A thermal-hydrodynamic coupling model is used to investigate the interplay between the wall temperature distribution and the bubble departure during the nucleate boiling process.The boiling process is modeled as the combination of three subprocesses:the transient heat conduction process in the solid heater,the evaporation of the microlayer underneath the bubble,and the bubble dynamics in the two-phase bulk fluid region.The moving bubble interface is captured by the volume of fluid method in the OpenFOAM framework.The proposed model is validated against the experimental results of the boiling process of the water on an Indium Tin Oxide heater.The predicted results agree well with related measurements in the literature.Following the validation,the effects of the boiling heat flux on the bubble departure period are examined.The results show that the bubble departure period decreases with the increase of the applied heat flux.High heat flux will cause irregularity in the departure periods for successive bubbles due to the influence of the wake flow evoked by the rising bubble.Furthermore,the influence of the bubble contact angle on the boiling heat-transfer performance is investigated.It is confirmed that the bubble departure diameter increases with the increase of the contact angle,meanwhile,the average wall temperature decreases with the increase of the contact angle.
文摘This study presents a parameter selection strategy developed for the Stretch-Blow Molding (SBM) process to minimize the weight of preforms used. The method is based on a predictive model developed using Neural Networks. The temperature distribution model of the preform was predicted using a 3-layer NN model with supervised backpropagation learning. In addition, the model was used to predict the uniform air pressure applied inside the preform, taking into account the relationship between the internal air pressure and the volume of the preform. Parameters were validated using in situ tests and measurements performed on several weights and lengths of a 0.330 Liter Polyethylene Terephthalate (PET) bottles. Tests showed that the model adequately predicts both the blowing kinematics, mainly zone temperatures and blowing and stretching pressures along the walls of the bottle while maintaining the bottle strength and top load requirements. In the second step, the model was combined to automatically compute the lowest preform weight that can be used for a particular 330 ml bottle design providing a uniform wall thickness distribution.
