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Articles 271 - 275 of 275

Full-Text Articles in Transport Phenomena

A Mathematical Model And Simulation Of Natural Circulation Loop Thermalhydraulics, Nihad E. Daidzic Mar 1992

A Mathematical Model And Simulation Of Natural Circulation Loop Thermalhydraulics, Nihad E. Daidzic

Aviation Department Publications

In this work, a simple, nonlinear, seventh-order mathematical model with lumped parameter analysis of the thermalhydraulic processes in a natural circulation steam boiler loop is presented. Digital simulation has been performed in order to predict open loop transients in severe accidental situations. Parts of the circulation loop such as the steam drum, downcomer, and riser were modelled separately on the basis of the integral balance equations. The two-phase flow in the steam drum and in the riser was modelled with the aid of a homogeneous-equilibrium, two-phase flow model. Special care was taken to ensure the stability of the numerical scheme, …

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Solutal Partition Coefficients In Nickel-Based Superalloy Pwa-1480, Surendra N. Tewari, M. Vijayakumar, James E. Lee, P. A. Curreri Jul 1991

Solutal Partition Coefficients In Nickel-Based Superalloy Pwa-1480, Surendra N. Tewari, M. Vijayakumar, James E. Lee, P. A. Curreri

Chemical & Biomedical Engineering Faculty Publications

Solutal profiles in dendritic single-crystal specimens of PWA-1480 nickel-base superalloy, which were directionally solidified and quenched, were examined on several transverse cross-sections to obtain the partition coefficients. Similar to their nickel-base binaries, the partition coefficients of tantalum, titanium, and aluminum were found to be less than unity; those of tungsten and cobalt were greater than unity. The partition coefficients were temperature independent in the range 1584-1608 K. The contribution of solid-state diffusion to microsegregation was observed to be negligible.

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Dendrite Tip Radii In Directionally Solidified Pb-8.4-Atmospheric-Percent-Au, Surendra N. Tewari Dec 1990

Dendrite Tip Radii In Directionally Solidified Pb-8.4-Atmospheric-Percent-Au, Surendra N. Tewari

Chemical & Biomedical Engineering Faculty Publications

The cell/dendrite tip radii in directionally solidified Pb-8.4at.%Au have been investigated as a function of the growth speed and thermal gradient in the liquid at the tip. Dendrite growth models are not able to predict quantitatively the tip radii and tip compositions separately because of the occurrence of thermosolutal convection during growth. However, the relationship between the destabilizing solutal gradient, the stabilizing thermal gradient and the capillarity at the tip assumed using the ''marginal stability'' criterion is supported by the experimental data.

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A Numerical Solution For The Turbulent Flow Of Non-Newtonian Fluids In The Entrance Region Of A Heated Circular Tube, Prapat Wangskarn, Bahman Ghorashi, Rama Subba Reddy Gorla Mar 1990

A Numerical Solution For The Turbulent Flow Of Non-Newtonian Fluids In The Entrance Region Of A Heated Circular Tube, Prapat Wangskarn, Bahman Ghorashi, Rama Subba Reddy Gorla

Chemical & Biomedical Engineering Faculty Publications

Numerical solutions of conservation equations are obtained for turbulent flow of non-Newtonian fluids in a circular tube. The forward marching procedure of Patankar and Spalding^1 was implemented in order to obtain the simultaneous development of the velocity and temperature fields by using the apparent viscosity of fluids. Prandtl's mixing length concept is used to determine the apparent turbulent shearing stress. Furthermore, local and average Nusselt numbers are obtained in the entrance region, as well as in the fully developed region. For the case of the fully developed region, values of the Nusselt numbers …

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Asymptotic Boundary-Layer Solutions For Mixed Convection From A Vertical Surface In A Micropolar Fluid, Rama Subba Reddy Gorla, Paul P. Lin, An-Jen J. Yang Jan 1990

Asymptotic Boundary-Layer Solutions For Mixed Convection From A Vertical Surface In A Micropolar Fluid, Rama Subba Reddy Gorla, Paul P. Lin, An-Jen J. Yang

Mechanical Engineering Faculty Publications

Using the theory of micropolar fluids due to Eringen, asymptotic boundary layer solutions are presented to study the combined convection from a vertical semi-infinite plate to a micropolar fluid. Consideration is given to the region close to the leading edge as well as the region far away from the leading edge. Numerical results are obtained for the velocity, angular velocity and temperature distribution. The missing wall values of the velocity, angular velocity and thermal functions are tabulated. Micropolar fluids display drag reduction and reduced surface heat transfer rate when compared to Newtonian fluids.

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