MILBIN KOSHY

super heaters are widely used in steam generators and heat-recovery steam generators (HRSGs). Their purpose is to raise steam temperature from saturation conditions to the desired final temperature, the steam flowing through the super heater tubes is usually heated at a very high temperature to ensure that all saturated steam is converted into superheated steam. In fact, the elevated temperature will cause the formation of oxide scales on the inner surface of the tube. This oxide scale reduces the heat transfer from the hot flue gas into the steam within the tube. This thermal barrier will cause failure of tubes. Finite element modeling is used for finding the overheating of the tubes with oxide scale.

An unrecrystallized structure is found to significantly improve the work hardening characteristics by lowering the work hardening rate during early stages of deformation. This is in contrast to a recrystallized structure, which requires a higher work hardening rate to accommodate the greater degree of multiple slip necessary to maintain strain compatibility between the more randomly oriented grains. The stronger texture associated with the unrecrystallized structure allows deformation to occur more efficiently. Addition of magnesium also improves work hardening by increasing overall level of the work hardening rate. The improved characteristics of the work hardening behavior result in a parallel increase in both the strength and ductility at cryogenic temperatures. These findings are positive since they suggest a method by which improvements in the work hardening behavior and subsequent mechanical properties may be obtained through practical modifications of the microstructure and composition.

Signal processing and A/D conversion for cryogenic applications places severe demands on the silicon fabrication process used to implement these functions, particularly in ionizing radiation environments. We describe a process designed for cryo applications such as high-energy collider front-end electronics, with specific optimization in the areas of noise, radiation hardness and predictable operation at 77 K. Applications of the technology are reviewed together with device issues and radiation test results

Alloy KhN35VTYu has high values of σu, σ0.2, and a0.25 at normal and cryogenic temperatures after hardening at 1050°C for 3 h in air and aging at 700°C for 3–8 h. The alloy is not sensitive to stress concentration. Increasing the hardening temperature to 1200°C leads to a significant decrease in the values of σ0.2 and a0.25.