Thesis (Ph. D.)--University of Texas at Austin, 2007. / Vita. Includes bibliographical references.

M.Ing. / The steelmaking process is briefly described with regard to process parameters and products influencing the fume extraction function of the water-cooled ducting. The flow distribution in the complex tubular network was determined by developing a software program based on parallel pass connections. A heat transfer analysis was performed on the specific problematic section referred to as the fixed elbow, with boundary conditions simulating the actual maximum operating conditions in an electric arc furnace. The temperature distribution was incorporated in a thermal stress analysis and a total stress profile was obtained for the radial as well as circumferencial positions. Areas of maximum stress were identified and the theory of fatigue failure due to cyclic operation was applied to these maximum stress conditions. The ABAQUS finite element program was used to model the behaviour of the material under the operating conditions using the sequencially coupled heat transfer and stress analysis routine. The results obtained correlates well with the actual failure of water-cooled ducting sections in operation and provides a platform for designing and optimising similar equipment for industrial applications.

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This research presents an analysis of thermal stratification in the reactor cold leg of the Advanced Plant Experiment-Combustion Engineering (APEX-CE). This phenomenon may be a precursor leading to a Pressurized Thermal Shock (PTS) event in a nuclear power plant. This work was performed in support of the U.S. Nuclear Regulatory Commission's (USNRC) re-evaluation of its PTS regulations. Using the APEX-CE test facility, thermal stratification was observed for injection flow rates ranging from 30% to 100% and natural circulation flow rates that were generated by core decay powers ranging from 1.5% to 4%, both relative to the scaled Palisades values. A theoretical model was derived to estimate the hot stream entrainment that occurs during cold leg thermal stratification. This model was applied to the Separate Effects Transparent Loop (SETL) facility, a scaled cold leg/downcomer configuration of the APEX-CE plant. The model predictions were in reasonable agreement with the High Pressure Injection (HPI) fluid entrainment data from the Purdue ½ scale facility. The same model was then used to estimate HPI entrainment in SETL. The results proved to be very consistent. Finally, data for the onset of loop seal spillover was obtained using SETL and APEX-CE. A useful flow map, characterizing the onset condition, was generated. / Graduation date: 2002

A large amount of heat can be liberated during cement hydration, causing very large temperature increases in mass concrete members. The non-uniform temperature field produced by the cement during curing can cause very high internal stresses that may crack the concrete. Concrete thermal cracking in very large structures is a well-known phenomenon and was studied extensively during the height of dam construction in the United States. In recent years concrete bridge member sizes have increased for structural and aesthetic reasons. Recent problems in San Antonio and Houston, Texas with thermal cracking and very high internal temperatures in mass concrete bridge members has renewed interest in studying early-age thermal cracking and its mechanisms. In order to predict the early-age thermal cracking risk of a concrete member, the temperature history, autogenous shrinkage, modulus development, tensile strength development, coefficient of thermal expansion development, creep behavior, and external restraint conditions must be known. A testing procedure has been developed to measure concrete heat of hydration, mechanical property development, and free shrinkage response at different curing temperatures. The concrete free shrinkage includes thermal and autogenous shrinkage components and is measured using a newly developed free shrinkage testing apparatus. The early age concrete creep is calculated from rigid cracking frame tests performed at different varying temperatures. Trends in early age creep behavior for different concrete mixtures common in mass concrete have been found and are used to develop a statistical model relating concrete mixture proportions and constituent material properties for use in mass concrete thermal stress modeling. The results from the test methods described are used in a new concrete early-age cracking risk and durability software package called ConcreteWorks. / text

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