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Abstract On the basis of experience acquired during a study on the reliability of PWR vessels, this text illustrates the points requiring more thorough investigation in order to raise the confidence level of the estimation of the reliability of the vessel. We also offer evidence of the need to develop, for already existing installations, adaptive type reliability models allowing a continually updated estimate of the reliability of the plant.

In 1981 the Giprokhimmash suggested organizing the wide introduction of full secondary power source use at the Sumsk Severno industrial unit plants, including a considerable number of existing, under construction, and planned undertakings from various departments and services and predominantly the very large plants and production associations of Minkhimmash in the Sumsk Severuo industrial unit having large unused secondary power source reserves.

Abstract The accurate information of the thermal stresses and temperature in isotropic elastic solids is the key for many engineering applications. At present the classical linear coupled theory of thermoelasticity deduced with the assumptions of small temperature changes is widely used to solve the thermoelastic problems in engineering. In this paper, to describe the thermoelastic behavior in isotropic solids undergoing large temperature changes more accurately, the novel coupled models of thermoelasticity and the corresponding finite element models have been presented explicitly and validated by experimental measurement. The effect of large temperature changes on the solutions of thermoelastic problems is discussed. For the heat transfer process, if the isotropic elastic solids will expand when heated and contract when cooled and the condition d E E d T · σ i j E − δ i j 1 − 2 ν α 0 can be met in the context of small deformations, the effect of large temperature changes can be regarded as increasing the specific heat. The proposed models are applied to solve two thermoelastic problems. From the obtained numerical results, the effect of large temperature changes will increase with the amplitude of temperature change and may be considerably even when the temperature changes slowly.

Abstract The reverse flat-plate collector is a non-concentrating collector. It can collect solar heat at high temperatures which cannot be achieved by conventional non-concentrating collectors. In this paper, the authors have proposed a number of modified versions of the originally proposed reverse flat-plate collector. The new designs are of single, as well as double, absorber type. The thermal performance of these modified reverse flat-plate collectors is compared with that of a single absorber reverse flat-plate collector, as well as with the corresponding normal flat-plate collector. It is found that the new design having two absorbers gives the best thermal performance as compared with other configurations. The analytical models presented in this paper very well describe the experimental results.

Abstract The analysis and optimization of flat plate fins of constant thickness and straight base has been conducted for different fin’s shapes. Performance of the fins is quantified through effectiveness and expressed as a function of fin’s shape, width, and area. A linear piecewise function with varying number of evenly spaced sections is used to generate shapes with different number of degrees of freedom, which are classified as constrained- or unconstrained-base depending on the width of the fin at the constant temperature base location. For one- and two-degrees of freedom shapes, a variety of rectangular, triangular, trapezoidal, and rhomboidal geometries are considered and optimized. For more than two-degrees of freedom, more complex resulting shapes are also considered. By adjusting the value of the corresponding shape parameters, the best possible distributions of available area to maximize heat transfer are obtained, which produce significant improvements favored by smaller width and larger area. Unconstrained-base performs better than constrained-base configurations as they allow the distribution of a larger area close to the high-temperature base. Optimal shape of unconstrained-base fins is in general convergent with non-zero wide tip, while, for constrained-base fins, it is divergent in the first linear section from the base and convergent in the remaining ones. For increasing number of degrees of freedom the optimized shapes tend to resemble natural structures while effectiveness increases asymptotically to a limit for constant width and area. Besides determining the optimal configurations, consideration has been made about the optimal regions where a variety of shapes produce virtually the same effectiveness of the absolute maximum, which can be used to design fins with almost maximum performance but having simpler shapes or being functional under possible space restrictions. The dimensionless model and the systematic analysis proposed in this work are not only appropriate to study a wide range of flat plate fins but also can be implemented to analyze and perform optimization over other type of fins and fins configurations.