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During service, the water wall tube will inevitably corrode due to various corrosive gases such as SO2, HCl, H2S, etc. To prevent the occurrence of tube burst accidents caused by thinning and income-pressure resistance of the water wall tube, it is necessary to monitor the wall thickness of the water wall tube row in real-time. This paper proposes an array-based method for monitoring the thickness of the water wall tube row, and the different corrosion characteristics models of the water wall tube row are established by using the finite element analysis software Maxwell. Based on the model, the influence of tube wall thickness and material on measurement accuracy is analyzed by current density distribution and electric field intensity. The error of calculation formula is analyzed by simulating different corrosion conditions of tube wall thinning. The calculation formula of the wall thickness after the corrosion of the water wall tube row and the correction formula of the wall thickness of a single water wall tube with the correction coefficient α of 3 are determined. And put forward to define the ”generalized average thickness” of the water wall corrosion of multiple tubes, and determine the correct formula for calculating the thickness of the water wall tube row with a correction coefficient β of 0.85 to 0.95.

In this manuscript, we have investigated the geometrical process variation of a 3-dimensinal silicon nanotube tunnel field effect transistor (Silicon NT-TFET) using TCAD numerical simulations. The device tube wall thickness and gate length have been tuned to investigate the effects on silicon NT-TFET performance. The performance indicators for silicon-NT-TFETs are ON current, OFF current, transconductance (gm), sub-threshold slope (SS), output resistance (ro) and unity gain cut off frequency (ft), and also analyzed the sensitivity of the silicon NT-TFET performance metrics for various silicon tube wall thicknesses such as IOFF, ION, gm and ft. A Silicon NT-TFET provides better performance with a thicker tube wall thickness and shorter gate length. [ABSTRACT FROM AUTHOR]

Water wall tube temperature is a major parameter in the steam generator design which has a significant role in keeping the steam generator available. Thus, knowing the tube average temperature in different operating conditions is very important to avoid the causes of tube failures. High temperatures are a major cause of various types of failures, such as overheating, hydrogen damage, thermal stress, etc. Furthermore, deposits on the inner tube wall contribute to such failure by changing the thermal resistance of the tube wall, which causes a significant increase in the tube wall's average temperature, consequently lowering the allowable stress. Therefore, the model was created by using ANSYS FLUENT (Canonsburg, PA, USA) to determine the wall average water tube wall temperature considering the deposit layer thickness (magnetite). Furthermore, this model was verified. It was found that increasing tube thickness can increase the average tube temperature but combining it with increasing deposit thickness leads to higher temperatures. In other words, the effect of the deposit on the tube with higher thickness is higher than on the tube with lower thickness. By discussing the minimum thickness of the water wall tube, the suitable selection of the tube thickness and courses of action concerning the operating conditions that minimize the potential overheating of water tubes in the furnace section of the boiler can be determined. [ABSTRACT FROM AUTHOR]

Non-uniform axial deformation and tube wall thinning are the main issues restricting the further development of the tube electromagnetic bulging technology. Aiming at overcoming these issues, a tube electromagnetic bulging method based on convex driving coil is proposed in this paper. An electromagnetic-structure coupling model of the tube electromagnetic expansion process is established and the influence of detailed convex coil parameters on radial and axial Lorentz forces are analyzed. Results show that with the new proposed method, the homogeneous length of the tube axial deformation is 4.7 times that of the expansion loading with conventional driving coil. Meanwhile, the issue of tube wall thinning in the conventional electromagnetic bulging method is restrained due to the produced axial electromagnetic force using the proposed convex coil. The proposed tube electromagnetic bulging based on convex coil can effectively overcome the issues currently exist in the conventional tube electromagnetic bulging and promote wide industrial application of the electromagnetic forming technology.

In the conventional electromagnetic tube expansion, tube wall thickness tends to decrease significantly while the workpiece is expanded. This paper is aimed at introducing a new technique using three-coil electromagnetic tube bulging with axial compression as an innovative solution for this issue. To validate the feasibility of the proposed technique and investigate the electromagnetic force distribution along the workpiece, COMSOL software is used to construct a detailed finite element analysis model for the proposed electromagnetic coupling model. Results show that the ratio of the axial and the radial electromagnetic forces increases linearly with the increase of the height and the outer diameter of the top and bottom coils. Furthermore, the tube deformation profile and the wall thickness are compared with two different coil structures. Comparison analysis reveals that for the same axial to radial electromagnetic forces ratio, the effect of prohibiting the wall thickness reduction using different coil structures is quite similar. The new method is expected to have a good potential in enhancing the tube-forming performance.

Water wall tube temperature is a major parameter in the steam generator design which has a significant role in keeping the steam generator available. Thus, knowing the tube average temperature in different operating conditions is very important to avoid the causes of tube failures. High temperatures are a major cause of various types of failures, such as overheating, hydrogen damage, thermal stress, etc. Furthermore, deposits on the inner tube wall contribute to such failure by changing the thermal resistance of the tube wall, which causes a significant increase in the tube wall’s average temperature, consequently lowering the allowable stress. Therefore, the model was created by using ANSYS FLUENT (Canonsburg, PA, USA) to determine the wall average water tube wall temperature considering the deposit layer thickness (magnetite). Furthermore, this model was verified. It was found that increasing tube thickness can increase the average tube temperature but combining it with increasing deposit thickness leads to higher temperatures. In other words, the effect of the deposit on the tube with higher thickness is higher than on the tube with lower thickness. By discussing the minimum thickness of the water wall tube, the suitable selection of the tube thickness and courses of action concerning the operating conditions that minimize the potential overheating of water tubes in the furnace section of the boiler can be determined.

This paper is the second of a two-part series that presents experimental data and analysis on the liquid nitrogen quenching heat transfer process of a stainless-steel tube with an inner surface low-thermal conductivity thin-film coating. This paper focuses on the effects of different flow directions and two tube wall thicknesses. Additionally, this paper also provides an analysis on the chilldown thermal efficiency of the quenching process. Three flow directions with four different inner surface coating modifications, and three tube wall thicknesses were examined. The experimental data covers the Reynolds numbers ranging from 3500 to 140,000. The chilldown efficiency, along with chilldown time and LN 2 (liquid nitrogen) mass consumption were analyzed to assess the overall performance of the LN 2 line chilldown process. For thin tube wall cases, the chilldown efficiencies cover a range between 3% and 41%, and the maximum chilldown efficiency value is found for the tube with 3 L coating at Re = 5278 in the vertical up flow direction. For thick wall tube cases, the efficiencies cover a range between 4% and 52%, and the maximum chilldown efficiency value was found for the tube with 4 L coating at Re = 5308 in the vertical up flow direction. [ABSTRACT FROM AUTHOR]